Aspen Aerogels (ASPN) 10-K 7 Mar 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Mar. 05, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	ASPN
Entity Registrant Name	ASPEN AEROGELS, INC.
Entity Central Index Key	0001145986
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity File Number	001-36481
Entity Tax Identification Number	04-3559972
Entity Address, Address Line One	30 Forbes Road
Entity Address, Address Line Two	Building B
Entity Address, City or Town	Northborough
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01532
City Area Code	508
Local Phone Number	691-1111
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
ICFR Auditor Attestation Flag	true
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, par value $0.00001 per share
Security Exchange Name	NYSE
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Document Financial Statement Error Correction [Flag]	false
Entity Common Stock, Shares Outstanding		76,664,530
Entity Public Float			$ 454.8
Auditor Name	KPMG LLP
Auditor Firm ID	185
Auditor Location	Boston, MA, United States of America
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s definitive Proxy Statement for its Annual Meeting of Stockholders to be held on May 30, 2024 are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 139,723	$ 281,335
Restricted cash	248	1,226
Accounts receivable, net of allowances of $230 and $255	69,995	57,350
Inventories	39,189	22,538
Prepaid expenses and other current assets	17,176	7,236
Total current assets	266,331	369,685
Property, plant and equipment, net	417,227	259,223
Operating lease right-of-use assets	17,212	11,990
Other long-term assets	2,278	2,518
Total assets	703,048	643,416
Current liabilities:
Accounts payable	51,094	54,728
Accrued expenses	22,811	16,003
Deferred revenue	2,316	5,846
Operating lease liabilities	1,874	2,368
Total current liabilities	78,095	78,945
Convertible note - related party	114,992	103,580
Operating lease liabilities long-term	21,906	13,456
Total liabilities	214,993	195,981
Commitments and contingencies (Note 12)
Stockholders' equity:
Preferred stock, $0.00001 par value; 5,000,000 shares authorized, no shares issued or outstanding at December 31, 2023 and 2022
Common stock, $0.00001 par value; 250,000,000 shares authorized, 76,503,151 and 69,994,963 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively	0	0
Additional paid-in capital	1,161,657	1,075,226
Accumulated deficit	(673,602)	(627,791)
Total stockholders' equity	488,055	447,435
Total liabilities and stockholders' equity	$ 703,048	$ 643,416

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Allowance for accounts receivable and contract assets	$ 230	$ 255
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	76,503,151	69,994,963
Common stock, shares outstanding	76,503,151	69,994,963

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Revenue	$ 238,718	$ 180,364	$ 121,622
Cost of revenue	181,797	175,388	111,685
Gross profit	56,921	4,976	9,937
Operating expenses:
Research and development	16,356	16,930	11,441
Sales and marketing	33,008	28,792	16,581
General and administrative	56,760	38,499	22,514
Total operating expenses	106,124	84,221	50,536
Loss from operations	(49,203)	(79,245)	(40,599)
Other income (expense)
Interest expense, convertible note - related party	(5,328)	(5,110)
Interest income (expense), net	6,534	1,617	(229)
Income from Employee Retention Credits	2,186
Gain on extinguishment of debt			3,734
Total other income (expense)	3,392	(3,493)	3,505
Net loss	$ (45,811)	$ (82,738)	$ (37,094)
Net loss per share:
Basic	$ (0.66)	$ (2.1)	$ (1.22)
Diluted	$ (0.66)	$ (2.1)	$ (1.22)
Weighted-average common shares outstanding:
Basic	69,439,034	39,363,114	30,433,154
Diluted	69,439,034	39,363,114	30,433,154

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Underwritten Public Offering [Member]	At The Market Offering [Member]	Private Placement [Member]	Registered Direct Offering [Member]	Common Stock 0.00001 Par Value [Member]	Common Stock 0.00001 Par Value [Member] Underwritten Public Offering [Member]	Common Stock 0.00001 Par Value [Member] At The Market Offering [Member]	Common Stock 0.00001 Par Value [Member] Private Placement [Member]	Common Stock 0.00001 Par Value [Member] Registered Direct Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Underwritten Public Offering [Member]	Additional Paid-in Capital [Member] At The Market Offering [Member]	Additional Paid-in Capital [Member] Private Placement [Member]	Additional Paid-in Capital [Member] Registered Direct Offering [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2020	$ 67,852										$ 575,811					$ (507,959)
Beginning balance, shares at Dec. 31, 2020						27,821,685
Net loss	(37,094)															(37,094)
Stock compensation expense	5,176										5,176
Issuance of restricted stock, shares						476,550
Vesting of restricted stock units	(2,713)										(2,713)
Vesting of restricted stock units, shares						254,513
Proceeds from employee stock option exercises	2,301										2,301
Proceeds from employee stock option exercises, shares						351,387
Proceeds from offering, net			$ 19,377	$ 73,509									$ 19,377	$ 73,509
Proceeds from offering, net, shares								929,981	3,462,124
Forfeiture of performance-based restricted stock, shares						(78,125)
Ending balance at Dec. 31, 2021	128,408										673,461					(545,053)
Ending balance, shares at Dec. 31, 2021						33,218,115
Net loss	(82,738)															(82,738)
Stock compensation expense	9,385										9,385
Issuance of restricted stock, shares						399,016
Vesting of restricted stock units	(2,362)										(2,362)
Vesting of restricted stock units, shares						173,263
Proceeds from employee stock option exercises	553										553
Proceeds from employee stock option exercises, shares						118,552
Proceeds from offering, net		$ 267,496	$ 72,733	$ 49,863								$ 267,496	$ 72,733	$ 49,863
Proceeds from offering, net, shares							29,052,631	5,241,400	1,791,986
Increase in debt discount due to modification of convertible note - related party	4,097										4,097
Ending balance at Dec. 31, 2022	447,435										1,075,226					(627,791)
Ending balance, shares at Dec. 31, 2022						69,994,963
Net loss	(45,811)															(45,811)
Stock compensation expense	10,954										10,954
Issuance of restricted stock, shares						44,928
Vesting of restricted stock units	(420)										(420)
Vesting of restricted stock units, shares						79,151
Proceeds from employee stock option exercises	$ 1,659										1,659
Proceeds from employee stock option exercises, shares	323,502					323,502
Proceeds from offering, net					$ 74,377										$ 74,377
Proceeds from offering, net, shares										6,060,607
Issuance costs from underwritten public offering	$ (139)										(139)
Ending balance at Dec. 31, 2023	$ 488,055										$ 1,161,657					$ (673,602)
Ending balance, shares at Dec. 31, 2023						76,503,151

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Underwritten Public Offering [Member]
Underwriting discounts and commissions		$ 8,052
Issuance costs		452
At The Market Offering [Member]
Issuance costs		616	$ 43
Commissions and fees		2,269	601
Private Placement [Member]
Issuance costs		137	1,491
Fees and issuance costs		$ 137	$ 1,491
Registered Direct Offering [Member]
Fees and issuance costs	$ 623

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (45,811)	$ (82,738)	$ (37,094)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	15,318	9,222	9,440
Gain on extinguishment of debt			(3,734)
Accretion of interest on convertible note - related party	4,403	5,110
Amortization of debt discount due to modification of convertible note - related party	888
Amortization of debt issuance costs			18
Provision for bad debt	(93)	115	(85)
Stock compensation expense	10,954	9,385	5,176
Reduction in the carrying amount of operating lease right-of-use assets	2,859	2,640	1,618
Changes in operating assets and liabilities:
Accounts receivable	(12,552)	(37,042)	(4,643)
Inventories	(16,651)	(10,551)	1,112
Prepaid expenses and other assets	(7,401)	(3,155)	(2,324)
Accounts payable	4,583	5,318	7,379
Accrued expenses	6,808	5,184	6,983
Deferred revenue	(3,530)	4,525	(543)
Operating lease liabilities	(2,424)	(2,444)	(1,497)
Other liabilities			(434)
Net cash used in operating activities	(42,612)	(94,399)	(18,628)
Cash flows from investing activities:
Capital expenditures	(175,455)	(177,974)	(13,778)
Net cash used in investing activities	(175,455)	(177,974)	(13,778)
Cash flows from financing activities:
Proceeds from issuance of convertible note related party		100,000
Proceeds from employee stock option exercises	1,659	553	2,301
Payments made for employee restricted stock tax withholdings	(420)	(2,362)	(2,713)
Fees and issuance costs from registered direct offering of common stock	(623)
Proceeds from private placement of common stock		50,000	75,000
Fees and issuance costs from private placement of common stock	(139)	(137)	(1,491)
Repayment of prepayment liability		(9,728)
Net cash provided by financing activities	75,477	478,370	92,474
Net (decrease) increase in cash, cash equivalents and restricted cash	(142,590)	205,997	60,068
Cash, cash equivalents and restricted cash at beginning of period	282,561	76,564	16,496
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	139,971	282,561	76,564
Supplemental disclosures of cash flow information:
Interest paid	1	153	236
Income taxes paid	0	0	0
Supplemental disclosures of non-cash activities:
Right-of-use assets obtained in exchange for new operating lease liabilities	10,380	3,030	12,092
Capitalized Interest	6,084	2,723
Increase in debt discount due to modification of convertible note - related party		4,097
Changes in accrued capital expenditures	(8,217)	31,970	4,701
Underwritten Public Offering [Member]
Cash flows from financing activities:
Proceeds from offering, net		267,948
Issuance costs		(452)
At The Market Offering [Member]
Cash flows from financing activities:
Proceeds from offering, net		73,349	19,420
Issuance costs		(616)	$ (43)
Registered Direct Offering [Member]
Cash flows from financing activities:
Proceeds from offering, net	75,000
Convertible Note [Member]
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of debt issuance costs	$ 37	32
Cash flows from financing activities:
Issuance costs		$ (185)

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
At The Market Offering [Member]
Commissions and fees net	$ 2,269	$ 601

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ (45,811)	$ (82,738)	$ (37,094)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023
Trading Arrangements, by Individual
Title	directors or executive officers
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Rule 10b5-1 Arr Modified Flag	false
Non Rule10B51 Arr Modified Flag	false

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	(1) Description of Business Nature of Business Aspen Aerogels, Inc. (the Company) is an aerogel technology company that designs, develops and manufactures innovative, high-performance aerogel insulation used primarily in the energy industrial and sustainable insulation materials markets. In addition, the Company has introduced a line of aerogel thermal barriers for use in battery packs in the electric vehicle ("EV") market. The Company is also developing applications for its aerogel technology in the battery materials and a number of other high-potential markets. The Company maintains its corporate offices in Northborough, Massachusetts. The Company has three wholly owned subsidiaries: Aspen Aerogels Rhode Island, LLC, Aspen Aerogels Germany, GmbH and Aspen Aerogels Georgia, LLC. Liquidity During the year ended December 31, 2023, the Company incurred a net loss of $ 45.8 million and used $ 42.6 million of cash in operations and $ 175.5 million of cash for capital expenditures. On February 15, 2022, the Company entered into a note purchase agreement with an affiliate of Koch Disruptive Technologies, LLC (Koch), relating to the issuance and sale of $ 100.0 million of the Company’s convertible debt. On November 29, 2022, the Company completed an underwritten public offering of 29,052,631 shares of our common stock at a public offering price of $ 9.50 per share. The Company received net proceeds of $ 267.5 million after deducting underwriting discounts and commissions of $ 8.1 million and offering expenses of approximately $ 0.5 million. On December 19, 2023, the Company entered into a securities purchase agreement with certain institutional investors named therein, pursuant to which the Company agreed to issue and sell, in a registered direct offering by the Company directly to the Investors an aggregate of 6,060,607 shares of the Company’s common stock, $ 0.00001 par value per share. The shares were sold to the Investors at a price per share of $ 12.375 per share. The net proceeds from the Offering, after deducting offering expenses, were approximately $ 74.4 million. The Company had unrestricted cash and cash equivalents of $ 139.7 million as of December 31, 2023. On November 28, 2022, the Company entered into a loan agreement with General Motors Holdings LLC, an entity affiliated with General Motors LLC, which provides for a multi-draw senior secured term loan in an aggregate principal amount of up to $ 100.0 million, available to the Company on a delayed draw basis beginning January 1, 2023 to September 30, 2023 , subject to certain conditions precedent to funding. On September 28, 2023, the Company amended the GM Loan Agreement to extend the draw period for the delayed GM Loan to a period beginning on the date that is twelve months prior to the date agreed upon by the Company and GM for the start of production at an aerogel manufacturing facility in Bulloch County, Georgia (the Plant) and ending on March 31, 2024 (or any later date approved in writing by GM at its sole discretion); extend the maturity date of the GM Loan from March 31, 2025 to September 30, 2025; and add financial covenants measured starting from the fiscal quarter ending December 31, 2024 and at the end of each fiscal quarter thereafter. The Company is increasing investment in the research and development of next-generation aerogel products and manufacturing process technologies. In addition, the Company has developed a number of promising aerogel products and technologies for the EV market. The Company believes that the commercial potential for the Company’s products and technology in the EV market is significant. Accordingly, the Company is hiring additional personnel, incurring additional operating expenses, and incurring significant capital expenditures to expand silica aerogel manufacturing capacity, build an automated thermal barrier fabrication operation, enhance research and development laboratory facilities and equipment, and construct a battery materials facility, among other efforts. The Company expects its existing cash balance will be sufficient to support current operating requirements, current research and development activities and the capital expenditures required to support the evolving commercial opportunity in the EV market and other strategic business initiatives. However, the Company plans to supplement its cash balance with equity financings, debt financings, equipment leasing, sale-leaseback transactions, customer prepayments, or government grant and loan programs to provide the additional capital necessary to purchase the capital equipment, construct the new facilities, establish the operations and complete the aerogel capacity expansions required to support these evolving commercial opportunities and strategic business initiatives.

Summary of Basis of Presentatio

Summary of Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Basis of Presentation and Significant Accounting Policies	(2) Summary of Basis of Presentation and Significant Accounting Policies Principles of Consolidation The accompanying condensed consolidated financial statements of the Company include the accounts of all its subsidiaries which are majority-owned, controlled by the Company or a variable interest entity (“VIE”) where the Company is the primary beneficiary. All significant intercompany accounts and transactions have been eliminated in consolidation. A VIE is an entity that lacks one or more of the characteristics of a voting interest entity. A VIE is defined as an entity in which equity investors do not have the characteristics of a controlling financial interest or do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties. The Company consolidates a VIE in accordance with ASC 810, Consolidation ("ASC 810") when it is the primary beneficiary of such VIE. As primary beneficiary, the Company has both the power to direct the activities that most significantly impact the economic performance of the VIE and a right to receive benefits or absorb losses of the entity that could be potentially significant to the VIE. The Company is required to reconsider its evaluation of whether to consolidate a VIE each reporting period, based upon changes in the facts and circumstances pertaining to the VIE. The Company evaluates the initial consolidation of each consolidated VIE, which includes a determination of whether the VIE constitutes the definition of a business in accordance with ASC 805, Business Combinations ("ASC 805"), by considering if substantially all of the fair value of the gross assets within the VIE are concentrated in either a single identifiable asset or group of single identifiable assets. Upon consolidation, the Company recognizes the assets acquired, the liabilities assumed, and any third-party ownership of membership interests as non-controlling interest as of the consolidation or acquisition date, measured at their relative fair values. In April 2022, the Company engaged Prodensa Servicios de Consultora to establish OPE Manufacturer Mexico S de RL de CV, a maquiladora located in Mexico with the express purposes of manufacturing thermal barrier PyroThin products and ultimately operating an automated fabrication facility for PyroThin. OPE is currently owned by Prodensa, which charges a management fee though there is an option for OPE to be purchased by Aspen after a period of 18 months . During the period between inception and the exercise of the purchase option, OPE operations are consolidated within the Company financial statements as of and for the year ended December 31, 2023 . Use of Estimates The preparation of the consolidated financial statements requires the Company to make a number of estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates and assumptions include allowances for doubtful accounts, sales returns and allowances, product warranty costs, inventory valuation, the carrying amount of property and equipment, right-of-use assets, lease liabilities, stock-based compensation, and deferred income taxes. The Company evaluates its estimates and assumptions on an on-going basis using historical experience and other factors, including current economic conditions, which are believed to be reasonable under the circumstances. Management adjusts such estimates and assumptions when facts and circumstances warrant. Illiquid credit markets, volatile equity markets, and declines in business investment can increase the uncertainty inherent in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in these estimates resulting from continuing changes in the economic environment will be reflected in the financial statements in future periods. Cash and Cash Equivalents Cash equivalents include short-term, highly liquid instruments, which consist of money market accounts and high-quality debt securities issued by the U.S. government via cash sweep accounts. All cash and cash equivalents are maintained with major financial institutions in North America. Deposits with this financial institution may exceed the amount of insurance provided on such deposits; however, these deposits typically may be redeemed upon demand and, therefore, bear minimal risk. Restricted Cash As of December 31, 2023, the Company had $ 0.2 million of restricted cash to support its outstanding letters of credit. Concentration of Credit Risk Financial instruments, which potentially expose the Company to concentrations of credit risk, consist principally of accounts receivable. The Company’s customers are primarily insulation distributors, insulation contractors, insulation fabricators and select energy and automotive end-users located throughout the world. The Company performs ongoing credit evaluations of its customers’ financial condition and generally requires no collateral to secure accounts receivable. The Company maintains an allowance for doubtful accounts based on its assessment of the collectability of accounts receivable. The Company reviews the allowance for doubtful accounts quarterly. During the year ended December 31, 2023, the Company recorded a charge for estimated customer uncollectible accounts receivable of less than $ 0.1 million. During the year ended December 31, 2022, the Company recorded a charge for estimated customer uncollectible accounts receivable of $ 0.1 million. During the year ended December 31, 2021, the Company did not record any charges for uncollectible accounts receivable. Allowance for doubtful accounts was $ 0.2 million and $ 0.3 million at December 31, 2023 and 2022, respectively. The Company does not have any off-balance-sheet credit exposure related to its customers. For the year ended December 31, 2023 , two customers represented 41 % and 14 % of total revenue, respectively. For the year ended December 31, 2022 , two customers represented 25 % and 22 % of total revenue, respectively. For the year ended December 31, 2021 , one customer represented 28 % of total revenue. At December 31, 2023 , the Company had two customers which accounted for 60 % and 6 % of accounts receivable, respectively. At December 31, 2022 , the Company had two customers which accounted for 44 % and 10 % of accounts receivable, respectively. Inventories Inventory consists of finished products, work-in-process, and raw materials. Inventories are carried at lower of cost, determined using the first-in, first-out (FIFO) method, and net realizable value. Cost includes materials, labor and manufacturing overhead. Manufacturing overhead is allocated to the costs of conversion based on normal capacity of the Company’s production facility. Abnormal freight, handling costs and material waste are expensed in the period it occurs. The Company periodically reviews its inventories and makes provisions as necessary for estimated excess, obsolete or damaged goods to ensure values approximate the lower of cost and net realizable value. The amount of any such provision is equal to the difference between the cost of inventory and the estimated net realizable value based upon assumptions about future demand, selling prices and market conditions. Prepaid expenses and other current assets Prepaid expenses and other current assets primarily include value added tax and income tax receivables, prepayments of future services, and payments for pre-billed inventories. Property, Plant and Equipment, Net Property, plant and equipment are stated at cost. Expenditures for maintenance and repairs are charged to expense as incurred. Expenditures for major betterments are capitalized as additions to property, plant and equipment. Depreciation on plant and equipment is calculated on the straight-line method over the estimated useful lives of the assets. Assets related to leasehold improvements are amortized on a straight-line basis over the shorter of the lease term or estimated useful life of the asset. Assets utilized in the Company’s operations that are taken out of service with no future use are charged to cost of revenue or operating expenses, depending on the department in which the asset was utilized. Impairments of construction in progress are charged to operating expenses upon the determination of no future use. Other Assets Other assets primarily include long-term deposits. Impairment of Long-Lived Assets Long-lived assets are reviewed for impairment when events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. Recognition and measurement of a potential impairment is performed on assets grouped with other assets and liabilities at the lowest level where identifiable cash flows are largely independent of the cash flows of other assets and liabilities. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset or asset group to future undiscounted net cash flows expected to be generated by the asset or asset group. If the carrying amount of an asset or asset group exceeds its estimated undiscounted future cash flows, an impairment charge is recognized for the amount by which the carrying amount of the asset or asset group exceeds the fair value of the asset or asset group. Fair value is determined through various valuation techniques including discounted cash flow models, quoted market values and third-party independent appraisals, as considered necessary. Revenue Recognition The Company recognizes revenue in accordance with Accounting Standards Codification 606, Revenue from Contracts with Customers (ASC 606). See note 3 for further details. Warranty The Company provides warranties for its products and records the estimated cost within cost of revenue in the period that the related revenue is recorded. The Company’s standard warranty period extends to one year from the date of shipment. This standard warranty provides that the Company’s products will be free from defects in material and workmanship, and will, under normal use, conform to the specifications for the product. The Company’s products may be utilized in systems that involve new technical demands and new configurations. Accordingly, the Company regularly reviews and assesses whether warranty reserves should be recorded in the period the related revenue is recorded. For an initial shipment of product for use in a system with new technical demands or new configurations and where the Company is unsure of meeting the customer’s specifications, the Company will defer the recognition of product revenue and related costs until written customer acceptance is obtained. The Company recorded warranty expense of $ 0.5 million during the year ended December 31, 2023 . The Company recorded warranty expense of $ 0.2 million during the year ended December 31, 2022 . The Company recorded warranty expense of less than $ 0.1 million during the year ended December 31, 2021 . Shipping and Handling Costs Shipping and handling costs are classified as a component of cost of revenue. Customer payments of shipping and handling costs are recorded as product revenue. Stock-based Compensation The Company grants share-based awards to its employees and non-employee directors. All share-based awards granted, including grants of stock options, restricted stock and restricted stock units (RSUs), are recognized in the statement of operations based on their fair value as of the date of grant. Expense is recognized on a straight-line basis over the requisite service period for all awards with service conditions. For performance-based awards, the grant date fair value is recognized as expense when the condition is probable of being achieved, and then on a graded basis over the requisite service period. The Company uses the Black-Scholes option-pricing model to determine the fair value of service-based option awards. The Black-Scholes model requires the use of a number of complex and subjective assumptions including fair value of the underlying security, the expected volatility of the underlying security, a risk-free interest rate and the expected term of the option. The fair value of restricted stock and RSUs is determined using the closing price of the Company’s common stock on the date of grant. All shares of restricted stock are not transferable until vested. Restricted stock is typically issued to non-employee directors and typically vests over a one-year period from the date of issuance. RSUs are issued to employees and typically vest over a three-year period from the date of issuance. The fair value of restricted stock and RSUs upon which vesting is solely service-based is expensed ratably over the vesting period. If the service condition for shares of restricted stock is not met for any reason, the shares of unvested restricted stock will be forfeited and returned to the Company. For stock awards that contain a market condition, the Company uses the Monte-Carlo simulation model to determine the fair value of the awards. In addition to the input assumptions used in the Black-Scholes model, the Monte-Carlo simulation model factors the probability that the specific market condition may or may not be satisfied into the valuation. Stock-based compensation expense for awards with a market condition is recognized on a straight-line basis over the requisite service period for each such award. Research and Development Costs incurred in the Company’s research and development activities include compensation and related costs, services provided by third-party contractors, materials and supplies and are classified as research and development expenses as incurred. Earnings per Share The Company calculates net loss per common share based on the weighted-average number of common shares outstanding during each period. Potential common stock equivalents are determined using the treasury stock method. The weighted-average number of common shares included in the computation of diluted net income (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options and RSUs. Common equivalent shares are excluded from the computation of diluted net loss per share if their effect is antidilutive. Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. The Company accounts for uncertain tax positions using a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Differences between tax positions taken in a tax return and amounts recognized in the financial statements are recorded as adjustments to income taxes payable or receivable, or adjustments to deferred taxes, or both. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. The Company recognizes penalties and interest related to uncertain tax positions, if any, as a component of income tax expense. Segments Operating segments are identified as components of an enterprise about which separate, discrete financial information is available for evaluation by the chief operating decision maker in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company’s chief operating decision maker reviews consolidated operating results to make decisions about allocating resources and assessing performance for the entire Company. The Company presently views its operations and manages its business as two operating segments. Leases The Company accounts for leases in accordance with FASB ASC Topic 842, Leases. The Company determines whether an arrangement is a lease at inception. For leases where the Company is the lessee, a lease liability and a right-of-use (ROU) asset is recognized for all leases, with the exception of short-term leases with terms of twelve months or less. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s payment obligations under the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term. To measure its lease liabilities, the Company uses its incremental borrowing rate or the rate implicit in the lease, if available. The Company calculates its incremental borrowing rate using a synthetic credit rating analysis based on Moody’s Building Materials Industry Rating Methodology. ROU assets also include any direct costs and prepaid lease payments but exclude any lease incentives received. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company elected the short-term lease recognition exemption for all leases that qualify. For leases that qualify for this exemption, the Company does not recognize ROU assets or lease liabilities. For lease agreements with lease and non-lease components, the Company accounts for each component separately. However, in the case of equipment leases, the Company accounts for lease and non-lease components as a single component. Refer to Note 11. Leases for additional information. Foreign Currency Transactions The Company converts foreign currency transactions recognized in the Consolidated Statements of Operations to U.S. dollars by applying the exchange rate prevailing on the date of the transaction. Gains and losses arising from foreign currency transactions and the effects of remeasuring monetary assets and liabilities are recorded in general and administrative expenses, net in the Consolidated Statements of Operations . Employee Retention Credits In March 2020, the Coronavirus Aid, Relief, and Economic Security Act was signed into law, providing numerous tax provisions and other stimulus measures, including the Employee Retention Credit: a refundable tax credit against certain employment taxes. The Taxpayer Certainty and Disaster Tax Relief Act of 2020 and the American Rescue Plan Act of 2021 extended and expanded the availability of the Employee Retention Credits. We qualified for the Employee Retention Credits in the third and fourth quarters of 2020 and the first quarter of 2021. In September 2023, we submitted filings for CARES Employee Retention Credits totaling $ 2.2 million that are reported in the accompanying condensed consolidated balance sheet within prepaid expenses and other current assets as of December 31, 2023, and in the accompanying statement of operations for the year ended December 31, 2023 . Recently Issued Accounting Standards From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board or other standard setting bodies. Recently issued standards typically do not require adoption until a future effective date. Prior to their effective date, the Company evaluates the pronouncements to determine the potential effects of adoption to its consolidated financial statements. Standards Implemented Since December 31, 2022 The Company has not implemented any accounting standards that had a material impact on its consolidated financial statements during the year ended December 31, 2023. Standards to be Implemented After December 31, 2023 In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2023-07 Segment Reporting (Topic 280) Improvements to Reportable Segment Disclosures to enhance disclosures about significant segment expenses. This ASU is effective for the Company’s fiscal year 2024 and interim periods in fiscal year 2025. Early adoption is permitted. The Company is currently evaluating segment expense disclosures related to its annual report for fiscal year 2024. In December 2023, the FASB issued ASU 2023-09 Income Taxes (Topic 740) Improvements to Income Tax Disclosures that requires disclosure of disaggregated income taxes paid, prescribes standard categories for the components of the effective tax rate reconciliation, and modifies other income tax-related disclosures. This ASU is effective for the Company’s fiscal year 2025. Early adoption is permitted. The Company is currently evaluating income tax disclosures related to its annual report for fiscal year 2025. Although there are several other new accounting pronouncements issued by the FASB, the Company does not believe any of these accounting pronouncements had or will have a material impact on its Consolidated Financial Statements. The Company believes that the impact of recently issued accounting standards that are not yet effective will not have a material impact on its consolidated financial statements.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	(3) Revenue from Contracts with Customers Revenue Recognition Revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, the Company performs the following five steps: (i) identification of the contract with a customer; (ii) identification of the performance obligations in the contract; (iii) determination of the transaction price; (iv) allocation of the transaction price to the separate performance obligations in the contract; and (v) recognition of the revenue associated with performance obligations as they are satisfied. The Company applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price based on the estimated relative standalone-selling prices of the promised products or services underlying each performance obligation. The Company determines standalone-selling prices based on the price at which the performance obligation is sold separately. If the standalone-selling price is not observable through past transactions, the Company estimates the standalone-selling price considering available information such as market conditions and internally approved pricing guidelines related to the performance obligations. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. When determining the transaction price of a contract, an adjustment is made if payment from a customer occurs either significantly before or significantly after performance, resulting in a significant financing component. Applying the practical expedient in paragraph ASC 606-10-32-18, the Company does not assess whether a significant financing component exists if the period between when the Company performs its obligations under the contract and when the customer pays is one year or less. The Company did not have any contracts outstanding at both December 31, 2023 and December 31, 2022 and did not enter into any contracts during each of the years ended December 31, 2023 and 2022 that contained a significant financing component. The Company records deferred revenue for product sales when (i) the Company has delivered products, but other revenue recognition criteria have not been satisfied, or (ii) payments have been received in advance of the completion of required performance obligations. Energy Industrial The Company generally enters into contracts containing one type of performance obligation. For a majority of the contracts, the Company recognizes revenue at a point in time when transfer of control of the products is passed to the customer, which is generally upon delivery according to contractual shipping terms within customer purchase orders. For a limited number of customer arrangements for customized products with no alternative use to the Company and an enforceable right to payment for progress completed to date, the Company recognizes revenue over time using units of production to measure progress toward satisfying the performance obligations. Units of production represent work performed as we do not generate significant work in process and thereby best depicts the transfer of control to the customer. Customer invoicing terms for contracts for which revenue is recognized under the over time methodology are typically based on certain milestones within the production and delivery schedule. The timing of revenue recognition is assessed on a contract-by-contract basis. The Company also enters into rebate agreements with certain customers. These agreements may be considered an additional performance obligation of the Company or variable consideration within a contract. Rebates are recorded as a reduction of revenue in the period the related revenue is recognized. A corresponding liability is recorded as a component of deferred revenue on the consolidated balance sheets. These arrangements are primarily based on the customer attaining contractually specified sales volumes. The Company estimates the amount of its sales that may be returned by its customers and records this estimate as a reduction of revenue in the period the related revenue is recognized. The Company currently estimates return liabilities using historical rates of return, current quarter credit sales, and specific items of exposure on a contract-by-contract basis. Sales return reserves were approximately $ 0.2 million and $ 0.1 million at December 31, 2023 and December 31, 2022, respectively. Thermal Barriers The Company supplies fabricated, multi-part thermal barriers for use in battery packs in the EV market. These thermal barriers are customized to meet customer specifications. Although thermal barrier products are customized with no alternative use to the Company, the Company does not always have an enforceable right to payment. Under the provisions of ASC 606, the Company recognizes revenue at a point in time when transfer of the control of the products is passed to the customer according to the terms of the contract, including under bill and hold arrangements. The timing of revenue recognition is assessed on a contract-by-contract basis. Shipping and Handling Costs Shipping and handling costs associated with outbound freight after control over a product has transferred to a customer are accounted for as fulfillment costs and are included in the cost of product revenue. The associated amount of revenue recognized includes the consideration to which the Company expects to be entitled to receive in exchange for incurring these shipping and handling costs. Disaggregation of Revenue In the following tables, revenue is disaggregated by primary geographical region and source of revenue: December 31, 2023 U.S. International Total (In thousands) Geographical region Asia $ — $ 35,698 $ 35,698 Canada — 2,033 2,033 Europe — 42,731 42,731 Latin America — 7,219 7,219 U.S. 151,037 — 151,037 Total revenue $ 151,037 $ 87,681 $ 238,718 Source of revenue Energy industrial $ 52,838 $ 75,801 $ 128,639 Thermal barrier 98,199 11,880 110,079 Total revenue $ 151,037 $ 87,681 $ 238,718 December 31, 2022 U.S. International Total (In thousands) Geographical region Asia $ — $ 34,746 $ 34,746 Canada — 4,947 4,947 Europe — 22,239 22,239 Latin America — 4,464 4,464 U.S. 113,968 — 113,968 Total revenue $ 113,968 $ 66,396 $ 180,364 Source of revenue Energy industrial $ 64,699 $ 60,108 $ 124,807 Thermal barrier 49,269 6,288 55,557 Total revenue $ 113,968 $ 66,396 $ 180,364 December 31, 2021 U.S. International Total (In thousands) Geographical region Asia $ — $ 19,383 $ 19,383 Canada — 2,985 2,985 Europe — 27,924 27,924 Latin America — 4,493 4,493 U.S. 66,837 — 66,837 Total revenue $ 66,837 $ 54,785 $ 121,622 Source of revenue Energy industrial $ 60,299 $ 54,659 $ 114,958 Thermal barrier 6,538 126 6,664 Total revenue $ 66,837 $ 54,785 $ 121,622 Contract Balances The following table presents changes in the Company’s contract assets and contract liabilities during the year ended December 31, 2023: Balance at Additions Deductions Balance at (In thousands) Contract assets Thermal barrier 143 — ( 143 ) — Total contract assets $ 143 $ - $ ( 143 ) $ — Contract liabilities Deferred revenue Energy industrial $ 5,846 $ 17,484 $ ( 21,014 ) $ 2,316 Total contract liabilities $ 5,846 $ 17,484 $ ( 21,014 ) $ 2,316 During the year ended December 31, 2023, the Company recognized $ 5.8 million of revenue that was included in deferred revenue at December 31, 2022. A contract asset is recorded when the Company satisfies a performance obligation by transferring a promised good or service and has earned the right to consideration from its customer. These assets may represent a conditional right to consideration and are included within accounts receivable on the consolidated balance sheets. A contract liability is recorded when consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services under the terms of the contract. Contract liabilities are recognized as revenue after control of the products or services is transferred to the customer and all revenue recognition criteria have been met.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2023
Inventory Disclosure [Abstract]
Inventories	(4) Inventories Inventories consist of the following: December 31, 2023 2022 (In thousands) Raw material $ 24,735 $ 19,876 Work in process 7,936 2,204 Finished goods 6,518 458 Total $ 39,189 $ 22,538

Property, Plant and Equipment,

Property, Plant and Equipment, Net	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Net	(5) Property, Plant and Equipment, Net Property, plant and equipment consist of the following: December 31, 2023 2022 Useful life (In thousands) Construction in progress $ 314,695 $ 209,056 — Buildings 25,473 24,016 30 years Machinery and equipment 185,339 136,607 3 — 10 years Computer equipment and software 9,495 10,239 3 years Leasehold improvements 23,514 9,226 Shorter of useful life or lease term Total 558,516 389,144 Accumulated depreciation and amortization ( 141,289 ) ( 129,921 ) Property, plant and equipment, net $ 417,227 $ 259,223 Depreciation expense was $ 15.3 million, $ 9.2 million and $ 9.4 million for the years ended December 31, 2023, 2022 and 2021, respectively. Construction in progress totaled $ 314.7 million and $ 209.1 million at December 31, 2023 and 2022, respectively. The balance at December 31, 2023 and 2022 included engineering designs and construction costs totaling $ 279.7 million and $ 164.5 million, respectively, for a planned aerogel manufacturing facility in Bulloch County, Georgia. The Company incurred $ 6.1 million and $ 2.7 million in capitalized interest for the years ended December 31, 2023 and December 31, 2022, respectively, for the construction in progress in Bulloch County, Georgia.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued Expenses	(6) Accrued Expenses Accrued expenses consist of the following: December 31, 2023 2022 (In thousands) Employee compensation $ 16,876 $ 12,467 Other accrued expenses 5,935 3,536 Total $ 22,811 $ 16,003

Revolving Line of Credit

Revolving Line of Credit	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Revolving Line of Credit	(7) Revolving Line of Credit The Company was party to the Second Amended and Restated Loan and Security Agreement with Silicon Valley Bank (Loan Agreement). On March 12, 2021, the Loan Agreement was amended and restated to extend the maturity date of the revolving credit facility to April 28, 2022 and to establish financial covenants on certain minimum Adjusted EBITDA levels and minimum Adjusted Quick Ratio covenants, each as defined in the Loan Agreement. At various dates in 2021, and subsequently on March 31, 2022, April 28, 2022, June 23, 2022, August 26, 2022 and October 14, 2022, the Company entered into amendments to the Loan Agreement to revise certain financial covenants, among other things. On November 28, 2022, the Company terminated the Loan Agreement with Silicon Valley Bank. As of both December 31, 2022 and 2023 , the Company had no amounts drawn from the revolving credit facility.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	(8) Related Party Transactions Convertible Note During the year ended December 31, 2022, the Company issued a $ 100.0 million aggregate principal amount convertible note to Wood River Capital, LLC, an entity affiliated with Koch Strategic Platforms, LLC (the 2022 Convertible Note). Refer to note 9 for more information. Common Stock Sales On June 29, 2021, the Company sold 3,462,124 shares of common stock to Spring Creek Capital, LLC, an entity affiliated with Koch Strategic Platforms, LLC, in a private placement of our common stock and received net proceeds of $ 73.5 million after deducting fees and offering expenses of $ 1.5 million. On March 28, 2022, the Company sold 1,791,986 shares of common stock to Wood River Capital, LLC, an entity affiliated with Koch Strategic Platforms, LLC, at a purchase price equal to $ 27.902 per share, for aggregate gross proceeds of approximately $ 50.0 million. On November 28, 2022, the Company sold 10,526,316 shares of common stock to Wood River Capital, LLC, an entity affiliated with Koch Strategic Platforms, LLC, at a purchase price equal to $ 9.50 per share, for aggregate gross proceeds of approximately $ 100.0 million, in an underwritten offering of common stock. Other During the year ended December 31, 2023, the Company recorded costs of $ 8.6 million as a component of construction in process in connection with the planned aerogel manufacturing facility in Bulloch County, Georgia in fees from an entity affiliated with Koch Disruptive Technologies, LLC for project management service. The Company had $ 2.8 million in accounts payable as of December 31, 2023 due to the entity affiliated with Koch Disruptive Technologies, LLC. During the year ended December 31, 2022, the Company recorded costs of $ 8.9 million as a component of construction in progress in connection with the planned aerogel manufacturing facility in Bulloch County, Georgia in fees from an entity affiliated with Koch Strategic Platforms, LLC for project management services. During the year ended December 31, 2022, the Company sold 135,870 shares of its common stock to Robert M. Gervis, a director of the Company at the time, in the Company’s at-the-market offering pursuant to a sales agreement, dated March 16, 2022, by and among the Company and Cowen and Company, LLC and Piper Sandler & Co. (the Sales Agreement), for net proceeds of $ 4.4 million.

Convertible Note - Related Part

Convertible Note - Related Party	12 Months Ended
	Dec. 31, 2023
Convertible Notes [Abstract]
Convertible Note - Related Party	(9) Convertible Note - Related Party 2022 Convertible Note On February 15, 2022 , the Company entered into a note purchase agreement (the Note Purchase Agreement) with Wood River Capital LLC, an entity affiliated with Koch Strategic Platforms, LLC (Koch), relating to the issuance and sale to Koch of the 2022 Convertible Note in the aggregate principal amount of $ 100.0 million. The transactions contemplated by the Note Purchase Agreement closed on February 18, 2022 (the Issue Date). The maturity date of the 2022 Convertible Note is February 18, 2027 , subject to earlier conversion, redemption, or repurchase. The 2022 Convertible Note is a senior unsecured obligation of the Company and ranks equal in right of payment to all senior unsecured indebtedness of the Company, and will rank senior in right of payment to any indebtedness that is contractually subordinated to the 2022 Convertible Note. In accordance with ASU 2020-06, the 2022 Convertible Note is accounted for as a single unit of account and consists of the following: December 31, December 31, 2023 2022 Convertible note, principal $ 100,000 $ 100,000 Payment in-kind 18,318 7,830 Discount on convertible note ( 3,209 ) ( 4,097 ) Debt issuance costs, net of accumulated amortization ( 117 ) ( 153 ) Convertible note $ 114,992 $ 103,580 In general, fair values determined by Level 1 inputs utilize observable inputs such as quoted prices in active markets for identical assets or liabilities. Fair values determined by Level 2 inputs utilize data points that are either directly or indirectly observable, such as quoted prices for similar instruments in active markets, interest rates and yield curves. Fair values determined by Level 3 inputs utilize unobservable data points in which there is little or no market data, which require the Company to develop its own assumptions for the asset or liability. The 2022 Convertible Note does not have current observable inputs such as recent trading prices (Level 3) and is measured at fair value using a combination of option pricing and discounted cash flow models and incorporate management’s assumptions for stock price, volatility and risk rate. The Company estimated the fair value of the 2022 Convertible Note is approximately $ 118.2 million as of December 31, 2023 . However, as the Company has not elected to utilize the fair value option, it is carried at amortized cost of $ 115.0 million. Contractual Interest Rates The 2022 Convertible Note was issued at par and bears interest at the Secured Overnight Financing Rate (SOFR) plus 5.50 % per annum if interest is paid in cash, or, if interest is paid in-kind as an increase in the principal amount of the outstanding note, at the SOFR plus 6.50 % per annum. Under the terms of the 2022 Convertible Note, SOFR has a floor of 1 % and a cap of 3 %. Interest on the 2022 Convertible Note is payable semi-annually in arrears on June 30 and December 30. The Company, at its option, is permitted to settle each semi-annual interest payment in cash, in-kind, or any combination thereof. It is expected that the Notes will mature on February 18, 2027 , subject to earlier conversion, redemption or repurchase. The Company elected to repay the contractual interest due on June 30, 2022, December 30, 2022, June 30, 2023, and December 30, 2023 in-kind as an increase to the principal amount of $ 2.9 million, $ 4.9 million, $ 5.1 million, and $ 5.4 million respectively. The contractual interest attributable to the 2022 Convertible Note was recorded as an addition to the convertible note – related party balance on the condensed consolidated balance sheets. During the year ended December 31, 2023, the Company incurred $ 10.5 million of interest from the 2022 Convertible Note, of which $ 6.1 million was capitalized as part of the construction in progress for the planned manufacturing facility in Bulloch County, Georgia. The Company paused the capitalization of interest related to the manufacturing facility being constructed in Bulloch County, Georgia during the year ended December 31, 2023 , as a result of the intentional slow down in construction. During the year ended December 31, 2022, the Company incurred $ 7.8 million of interest from the 2022 Convertible Note, of which $ 2.7 million was capitalized as part of the construction in progress for the planned manufacturing facility in Bulloch County, Georgia. Debt issuance costs comprised less than $ 0.2 million for the year ended December 31, 2023. The effective interest rate approximated the contract interest rate for the year ended December 31, 2023. Conversion Rights On November 28, 2022, the Company entered into an amendment to the Convertible Note with Wood River Capital, LLC to reduce the initial Conversion Price by $ 5.00 per share from $ 34.936625 per share to $ 29.936625 per share, by increasing the initial Conversion Rate from 28.623257 shares per $ 1,000 of Capitalized Principal Amount to 33.400100 shares per $ 1,000 of Capitalized Principal Amount under the Convertible Note. Accordingly, the 2022 Convertible Note is convertible at the option of the holder at any time prior to the business day immediately preceding the maturity date at an initial conversion rate of 33.400100 shares of the Company’s common stock per $ 1,000 of capitalized principal. The effective conversion price is approximately $ 29.936625 per share (the Conversion Price). The Conversion Price is subject to adjustment upon the occurrence of certain dilutive events such as stock splits and combinations, stock dividends, mergers and spin-off. As of December 31, 2023, 3,951,833 shares of the Company’s common stock were issuable upon conversion of the 2022 Convertible Note. The Company has the right to settle conversions in shares of common stock, cash, or any combination thereof. If the closing price per share of the Company’s common stock on the New York Stock Exchange is at least 130 % of the Conversion Price for 20 consecutive trading days , the Company may elect to convert the principal and accrued interest owing under the Notes, plus a make-whole amount equal to the sum of the present values of the remaining interest payments that would have otherwise been payable from the date of such conversion, redemption or repurchase, as applicable, through maturity (the Make-Whole Amount), into the Company’s common stock at the Conversion Price. Optional Redemption The 2022 Convertible Note is redeemable at the Company’s option at any time and in the event that the volume weighted average price of the Company’s common stock for the 10 trading days immediately preceding the date on which the Company provides the redemption notice has been at least 130 % of the Conversion Price then in effect at a redemption price of 100 % of the principal amount, plus accrued and unpaid interest (excluding the redemption date), plus the Make-Whole Amount. Contingent Redemption Upon the occurrence of certain fundamental changes described in the Indenture (each, a Fundamental Change), the Holder of the Note may require that the Company repurchase all or part of the principal amount of the Note at a purchase price of 100 % of the principal amount of such Note, plus accrued and unpaid interest to, but excluding, the Fundamental Change repurchase date, plus the Make-Whole Amount. The Indenture includes customary “events of default,” which may result in the acceleration of the maturity of the Note. Embedded Derivatives The Company determined that the Make-Whole feature of the 2022 Convertible Note requires bifurcation in accordance with Accounting Standards Codification 815, Derivatives and Hedging (ASC 815). Accordingly, the Company must separately account for the feature at fair value with changes in fair value reported in current period earnings. The fair value of the Make-Whole was determined to be immaterial as of February 18, 2022, December 31, 2022, and December 31, 2023 .

Other Income (Expense)

Other Income (Expense)	12 Months Ended
	Dec. 31, 2023
Interest Income (Expense), Net [Abstract]
Other Income (Expense)	(10) Other Income (Expense) Interest For the years ended December 31, 2023, and 2022 , interest expense on the related party convertible note was $ 5.3 million and $ 5.1 million, respectively and interest income, net, of $ 6.5 million and $ 1.6 million, respectively, are primarily related to interest earned on unrestricted cash and cash equivalents. For the year ended December 2021, interest expense, net was $ 3.5 million, and consisted primarily of fees and interest expense related to the Company’s revolving credit facility with Silicon Valley Bank. Employee Retention Credits The CARES Act provides an employee retention credit (CARES Employee Retention Credit), which is a refundable tax credit against certain employment taxes of up to $ 5,000 per employee for eligible employers. The tax credit is equal to 50 % of qualified wages paid to employees during a quarter, capped at $ 10,000 of qualified wages per employee through December 31, 2020. Additional relief provisions were passed by the United States government, which extend and slightly expand the qualified wage caps on these credits through December 31, 2021. Based on these additional provisions, the tax credit is now equal to 70 % of qualified wages paid to employees during a quarter, and the limit on qualified wages per employee has been increased to $ 10,000 of qualified wages per quarter. The Company qualified for the tax credit under the CARES Act for qualified wages for the years ended December 31, 2020 and 2021. In September 2023, the Company submitted filings for CARES Employee Retention Credits totaling $ 2.2 million that are reported in the accompanying condensed consolidated balance sheet within prepaid expenses and other current assets as of December 31, 2023, and in the accompanying statement of operations for the year ended December 31, 2023.

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	(11) Leases The Company leases office, laboratory, warehouse and fabrication space in Massachusetts, Rhode Island and Monterrey, Mexico under operating leases. Under these agreements, the Company is obligated to pay annual rent, real estate taxes, and certain other operating expenses. The Company also leases equipment under operating leases. The Company’s operating leases expire at various dates through 2034 . During 2016, the Company entered into an agreement to extend its lease of approximately 51,650 square feet of office space in Northborough, Massachusetts. The lease commenced on January 1, 2017 and will expire on December 31, 2031 . The annual base rent associated with the lease was $ 478,000 during 2023 and is increasing by approximately 3 % annually for the term of the lease. The lease also requires the payment by the Company of its pro rata share of real estate taxes and certain other expenses. Prior to the expiration of the lease, the Company will have the right to extend the lease for an additional term of five years . Under the terms of the lease extension, the landlord provided the Company with an allowance of $ 1.2 million to be utilized for improvements to the leased premises. These amounts were considered a lease incentive and were excluded from the Company’s ROU assets upon its adoption of ASU 2016-02 on January 1, 2019 (see note 11). At December 31, 2023 and 2022 , the Company had capitalized $ 1.2 million in associated leasehold improvement costs. The Company incurred operating lease costs of $ 5.3 million and $ 4.0 million during the years ended December 31, 2023 and 2022, respectively. Cash payments related to operating lease liabilities were $ 4.9 million and $ 3.6 million during the years ended December 31, 2023 and 2022, respectively. At December 31, 2023, the weighted average remaining lease term for operating leases was 9.0 years. At December 31, 2023, the weighted average discount rate for operating leases was 12.0 % . Maturities of operating lease liabilities at December 31, 2023 are as follows: Year Operating (In thousands) 2024 $ 4,531 2025 4,373 2026 4,064 2027 3,793 2028 3,946 Thereafter 19,174 Total lease payments 39,881 Less imputed interest ( 16,101 ) Total lease liabilities $ 23,780 As of December 31, 2023 , the Company had no additional operating real estate or equipment leases that would commence during 2024.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	(12) Commitments and Contingencies Cloud Computing Agreement The Company is party to a cloud computing agreement that is a service contract for enterprise resource planning software. The agreement has a three-year term beginning on January 15, 2021, with option to renew. During the year ended December 31, 2023, the Company capitalized $ 1.3 million of costs related to implementation of the software that began to amortize during 2022 with a five year expected life. The capitalized implementation costs are classified on the consolidated balance sheets as follows: December 31, December 31, 2023 2022 (In thousands) Cloud computing costs included in other current assets $ 420 $ 420 Cloud computing costs included in other assets 1,590 1,590 Amortization of cloud computing costs ( 662 ) ( 242 ) Total capitalized cloud computing costs $ 1,348 $ 1,768 Thermal Barrier Contract The Company is party to production contracts with GM to supply fabricated, multi-part thermal barriers (Barriers) for use in the battery system of its next-generation EVs (Contracts). Pursuant to the Contracts, the Company is obligated to supply Barriers at fixed annual prices and at volumes to be specified by the OEM up to a daily maximum quantity through the respective terms of the agreements, which expire at various times from 2026 through 2034. While the OEM has agreed to purchase its requirement for Barriers from the Company for locations to be designated from time to time by the OEM, it has no obligation to purchase any minimum quantity of Barriers under the Contracts. In addition, the OEM may terminate the Contracts any time and for any or no reason. All other terms of the Contracts are generally consistent with the OEM’s standard purchase terms, including quality and warranty provisions that are customary in the automotive industry. Letters of Credit The Company has provided certain customers with letters of credit securing obligations under commercial contracts. As of December 31, 2023, the Company had $ 0.2 million of restricted cash to support our outstanding letters of credit. The Company had letters of credit outstanding of $ 1.2 million at December 31, 2022 . These letters of credit were secured by the Company’s revolving credit facility (see note 7). On November 28, 2022 , we terminated the Loan Agreement with Silicon Valley Bank. Litigation The Company is, from time to time, a party to litigation that arises in the normal course of its business operations. See Part I, Item 3 (“Legal Proceedings”) of this Annual Report on Form 10-K for a description of certain of the Company’s current legal proceedings. The Company is not presently a party to any litigation for which it believes a loss is probable requiring an amount to be accrued or a possible loss contingency requiring disclosure. Purchase Commitments As of December 31, 2023, the Company had purchase commitments of approximately $ 267.3 million, which included capital commitments of $ 202.6 million. Purchase commitments related to capital expenditures are anticipated to be spent over the next three years , while the Company's remaining purchase commitments are anticipated to be spent throughout 2024. Purchase obligations relate primarily to open purchase orders for capital expenditures, inventories, and goods and services. Purchase obligations are entered into with various vendors in the normal course of business and are consistent with the Company's expected requirements.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Stockholders' Equity	(13) Stockholders’ Equity At December 31, 2023 and 2022 , the Company was authorized to issue 255,000,000 shares of stock, of which 250,000,000 shares were designated as common stock and 5,000,000 shares were designated as preferred stock.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2023
Postemployment Benefits [Abstract]
Employee Benefit Plan	(14) Employee Benefit Plan The Company sponsors the Aspen Aerogels, Inc. 401(k) Plan. Under the terms of the plan, the Company’s employees may contribute a percentage of their pretax earnings. During the year ended December 31, 2023, 2022, and 2021, the Company provided matching contributions of $ 1.5 million, $ 1.2 million, and $ 0.3 million, respectively.

Employee Stock Ownership Plans

Employee Stock Ownership Plans	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Employee Stock Ownership Plans	(15) Employee Stock Ownership Plans Effective June 12, 2014, the Company adopted the 2014 Employee, Director and Consultant Equity Incentive Plan (the 2014 Equity Plan). Under the 2014 Equity Plan, the Company was authorized to grant incentive stock options (ISOs), non-qualified stock options (NSOs), restricted stock, restricted stock units (RSUs) and other stock-based awards. Stock options under the 2014 Equity Plan were granted with an exercise price not less than the fair market value of the Company’s common stock at the date of grant. The 2023 Equity Plan was approved by stockholders at the Company’s annual meeting of stockholders on June 1, 2023 as the successor to the 2014 Equity Plan, and no further awards may be made under the 2014 Equity Plan after that date. Under the 2023 Equity Plan, the Company may grant ISOs, NSOs, restricted stock, RSUs and other stock-based awards. Stock options under the 2023 Equity Plan are to be granted with an exercise price not less than the fair market value of the Company’s common stock at the date of grant. Equity awards granted to employees generally vest over a service period of three to four years . Restricted stock and stock options granted to nonemployee directors generally vest over a one-year service period. As of December 31, 2023, 5,808,440 shares of common stock were reserved for issuance upon the exercise or vesting of outstanding stock-based awards granted under the Company’s equity incentive plans. Any cancellations or forfeitures of awards outstanding under the 2023 Equity Plan, the 2014 Equity Plan or the 2001 Equity Incentive Plan, as amended (the 2001 Equity Plan) will result in the shares reserved for issuance pursuant to such awards becoming available for grant under the 2023 Equity Plan. As of December 31, 2023, the Company has either reserved in connection with statutory tax withholdings or issued a total of 5,173,760 shares under the Company’s equity incentive plans. As of December 31, 2023, there were 2,139,794 shares of common stock available for future grant under the 2023 Equity Plan. During the year ended December 31, 2023, the Company granted 523,783 restricted common stock units (RSUs) with a grant date fair value of $ 4.6 million and non-qualified stock options (NSOs) to purchase 1,974,978 shares of common stock with a grant date fair value of $ 9.7 million to employees under its equity incentive plans. The RSUs and NSOs granted to employees will vest over a three-year period from the applicable vesting commencement date. During the year ended December 31, 2023, the Company also granted 44,928 shares of restricted common stock with a grant date fair value of $ 0.3 million and NSOs to purchase 46,272 shares of common stock with a grant date fair value of $ 0.2 million to its non-employee directors under the 2023 Equity Plan. The restricted common stock and NSOs granted to non-employee directors vest upon the earlier of the date that is the one-year anniversary of the grant date or the day prior to the Company’s annual meeting of stockholders to be held in 2024. On June 29, 2021, the Company also awarded 461,616 shares of restricted common stock to its chief executive officer with vesting subject to the achievement of certain volume weighted average common stock price targets, over a three -to- five year period. The award had an aggregate grant date fair value of $ 6.5 million. On June 2, 2022, the Company issued 53,590 shares of restricted common stock, pursuant to a performance-based restricted stock agreement, to each of certain employees, with vesting in tranches, subject to achievement of certain time and performance vesting conditions, as defined, over a three -to- five year period. The equity awards had a total aggregate fair value of $ 4.0 million at the time of grant. Stock-based compensation is included in cost of sales or operating expenses, as applicable, and consists of the following: Year Ended December 31, 2023 2022 2021 (In thousands) Cost of product revenue $ 583 $ 931 $ 510 Research and development expenses 799 1,166 750 Sales and marketing expenses 1,484 1,883 822 General and administrative expenses 8,088 5,405 3,094 Total stock-based compensation $ 10,954 $ 9,385 $ 5,176 Stock Options Valuation and Amortization Method The fair value of each stock option is estimated as of the date of grant using the Black-Scholes option-pricing model. Key inputs into this formula included expected term, expected volatility, expected dividend yield and the risk-free rate. Each assumption is set forth and discussed below. The Company used a Monte-Carlo Simulation model to estimate the original grant date fair value of the CEO Options as well as the subsequent modifications. The simulation model was based on the Black-Scholes option-pricing model and a number of complex assumptions including (i) whether the vesting condition is satisfied within the time-vesting periods, and (ii) the date the common stock price target is met per the terms of the agreement. For stock options with a service condition, the fair value is amortized on a straight-line basis over the requisite service period of the options, which is generally a three-year vesting period from the date of grant. Expected Term The expected term represents the period that the Company’s stock-based awards are expected to be outstanding. The Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. Accordingly, the Company uses the simplified method to calculate the expected term for options granted. Expected Volatility In 2023, 2022 and 2021, the Company used its historical volatility as a basis to estimate expected volatility in the valuation of stock options. Expected Dividend The Company uses an expected dividend yield of zero . The Company does not intend to pay cash dividends on its common stock in the foreseeable future, nor has it paid dividends on its common stock in the past. Risk-free Interest Rate The Company uses a risk-free interest rate based on U.S. Treasury zero-coupon issues with a remaining term equal to the expected life assumed at the date of grant. Estimated Forfeitures The Company records the impact of forfeitures of service-based awards under the provisions of ASU 2016-09 at the time an award is forfeited. Assumptions Utilized The following information relates to the fair value of the option awards estimated by use of the Black-Scholes option-pricing model: Year Ended December 31, 2023 2022 2021 Weighted average assumptions: Expected term (in years) 6.12 5.97 5.96 Expected volatility 70.04 % 61.85 % 59.80 % Risk free rate 4.08 % 2.13 % 0.86 % Expected dividend yield 0.00 % 0.00 % 0.00 % Weighted average fair value: Grant-date fair value of options granted $ 4.91 $ 14.20 $ 14.28 Grant-date fair value of options vested $ 9.63 $ 5.06 $ 2.91 Aggregate intrinsic value of options exercised $ 1,652,567 $ 1,306,245 $ 12,675,489 Outstanding Options The following table summarizes information about stock options outstanding: Number of Weighted Weighted Weighted Aggregate ($ in thousands, except share and per share data) Options outstanding at December 31, 2022 3,904,080 $ 7.12 $ 11.37 5.26 $ 16,486,864 Granted 2,021,250 $ 4.91 $ 7.46 Forfeited ( 300,788 ) $ 10.18 $ 17.25 Expired ( 66,846 ) $ 98.27 $ 82.78 Exercised ( 323,502 ) $ 2.59 $ 5.13 $ 1,652,567 Options outstanding at December 31, 2023 5,234,194 $ 5.21 $ 8.99 6.13 $ 41,225,602 Exercisable at December 31, 2023 3,002,950 $ 4.58 $ 8.52 6.13 $ 24,797,684 Expected to vest at December 31, 2023 2,231,244 $ 6.07 $ 9.62 2.09 $ 16,427,918 As of December 31, 2023, total unrecognized compensation cost related to non-vested service-based options granted under the Company’s equity incentive plans was $ 9.7 million. The unrecognized compensation cost for the service-based options is expected to be recognized over a weighted average period of 2.09 years. Restricted Stock Awards and Restricted Stock Units The Company values restricted stock awards and RSUs based on the closing price of our shares on the date of grant. RSUs have time-based vesting conditions and typically vest over three or four years . Restricted stock awards issued to nonemployee directors generally vest in full one year from the date of grant. During the year ended December 31, 2021, the Company also awarded 461,616 shares of restricted common stock to its chief executive officer with vesting subject to the achievement of certain volume weighted average common stock price targets, over a three -to- five year period. The Company valued the shares using a Monte-Carlo simulation model to estimate the grant date fair value utilizing an expected volatility of 59.3 % and a risk free rate of 0.89 %. On June 2, 2022, the Company issued 53,590 shares of restricted common stock, pursuant to a performance-based restricted stock agreement, to each of certain employees, with vesting in tranches, subject to achievement of certain time and performance vesting conditions, as defined, over a three -to- five year period. The Company used a Monte-Carlo simulation model to estimate the grant date fair value utilizing an expected volatility of 63.4 % and a risk free rate of 2.92 % . The following table provides detail of grants, vesting, and forfeitures of RSUs during 2023: Restricted Weighted Balance at December 31, 2022 257,075 $ 22.19 Granted 523,783 8.72 Vested ( 117,941 ) 18.97 Forfeited ( 88,670 ) 16.93 Balance at December 31, 2023 574,247 $ 11.38 Restricted stock awards granted during 2023 are considered issued and outstanding common stock and are excluded from the table above. As of December 31, 2023, there were 881,674 shares of restricted stock outstanding of which 44,928 were granted to nonemployee directors, 461,616 shares of restricted stock outstanding granted to the Company’s chief executive officer and 375,130 shares of restricted stock outstanding granted to other employees. The total intrinsic value of restricted stock and RSUs that vested in 2023 and 2022 was $ 1.3 million and $ 7.4 million, respectively. As of December 31, 2023, 1,377,796 of the total shares of restricted stock and RSUs outstanding will vest upon the fulfillment of service conditions. As of December 31, 2023, total unrecognized compensation cost related to restricted stock awards issued to nonemployee directors of $ 0.1 million, and RSUs of $ 4.4 million is expected to be recognized over a weighted average period of 0.42 years and 1.90 years respectively. As of December 31, 2023, total unrecognized compensation cost related to restricted stock awards issued to the Company’s chief executive officer and certain other employees of $ 4.1 million is expected to be recognized over a weighted average period of 1.08 years.

CARES Act Payroll Tax Deferral

CARES Act Payroll Tax Deferral	12 Months Ended
	Dec. 31, 2023
Other Liabilities Disclosure [Abstract]
CARES Act Payroll Tax Deferral	(16) CARES Act Payroll Tax Deferral The Company elected to defer approximately $ 0.9 million of its employer payroll tax obligation for the period from March 27, 2020 to December 31, 2020 pursuant to the provisions of the CARES Act. The Company was required to remit 50 percent of the deferred tax balance on or before December 31, 2021 and is required to remit the remaining 50 percent on or before December 31, 2022 . As of December 31, 2022, the Company had remitted its repayment obligation.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	(17) Net Loss Per Share The computation of basic and diluted net loss per share consists of the following: Year ended December 31, 2023 2022 2021 (In thousands, except share and per share data) Numerator: Net loss $ ( 45,811 ) $ ( 82,738 ) $ ( 37,094 ) Denominator: Weighted average shares outstanding, basic and diluted 69,439,034 39,363,114 30,433,154 Net loss per share, basic and diluted $ ( 0.66 ) $ ( 2.10 ) $ ( 1.22 ) Potentially dilutive common shares that were excluded from the computation of diluted net loss per share because they were anti-dilutive consist of the following: Year ended December 31, 2023 2022 2021 Common stock options 5,234,194 3,904,080 3,567,207 Restricted common stock units 574,247 257,075 350,195 Restricted common stock awards 881,674 23,886 14,934 Convertible note, if converted 3,951,833 3,601,533 — Total 10,641,948 7,786,574 3,932,336 In the table above, the potential dilutive shares from common stock options, restricted common stock units, restricted common stock awards, and the convertible note were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented. The Company excludes the shares issued in connection with restricted stock awards from the calculation of basic weighted average common shares outstanding until the restrictions lapse. For each of the years ended December 31, 2023, 2022 and 2021 , there was no dilutive impact of the common stock options, RSUs, and restricted stock awards.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	(18) Income Taxes The Company incurred net operating losses and recorded a full valuation allowance against net deferred assets for all periods presented. Accordingly, the Company has not recorded a provision for federal or state income taxes. The reconciliation between the U.S. statutory income tax rate and the Company’s effective rate consists of the following: Year Ended December 31, 2023 2022 2021 U.S. federal income tax statutory rate 21 % 21 % 21 % Permanent differences — 1 % 10 % State tax, net of federal benefit 7 % 5 % 5 % Changes in valuation allowance for deferred tax assets ( 17 )% ( 27 )% ( 35 )% Stock-based compensation ( 7 )% — % — % Expiring net operating losses — % — % ( 1 )% Other 2 % — % — % State rate change ( 6 )% — % — % Effective tax rate — — — The tax effects of temporary differences between financial statement and tax accounting that gave rise to significant portions of the Company’s deferred tax assets and deferred tax liabilities at December 31, 2023 and 2022 are presented below: December 31, 2023 2022 (In thousands) Deferred tax assets: Net operating loss carryforwards $ 82,563 $ 81,943 Stock-based compensation 3,076 6,677 Operating lease liabilities 5,997 4,065 Capitalized research and development 6,320 3,916 Tax credit carryforwards 4,261 448 Reserves and accruals 6,180 3,160 Interest expense limitation 929 1,257 Total gross deferred tax assets 109,326 101,466 Deferred tax liabilities: Depreciation ( 1,125 ) ( 1,879 ) Operating lease right-of-use assets ( 4,340 ) ( 3,081 ) Total deferred tax liabilities ( 5,465 ) ( 4,960 ) Total deferred tax assets and liabilities 103,861 96,506 Valuation allowance ( 103,861 ) ( 96,506 ) Net deferred tax asset $ — $ — The net change in the valuation allowance for the year ended December 31, 2023 , was an increase of $ 7.4 million. The Company has recorded a full valuation allowance against its deferred tax assets due to the uncertainty associated with the utilization of the net operating loss carryforwards and other future deductible items. In assessing the realizability of deferred tax assets, the Company considers all available evidence, historical and prospective, with greater weight given to historical evidence, in determining whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of the Company’s deferred tax assets generally is dependent upon generation of future taxable income. At December 31, 2023 , the Company had $ 358.9 million of net operating losses available to offset future federal income, if any, of which $ 194.6 million expire on various dates through December 31, 2037 . Net operating losses of $ 164.3 million generated from 2018 through 2023 have an unlimited carryforward . At December 31, 2023, the Company had $ 198.6 million of apportioned net operating losses available to offset future state taxable income, if any, and which begin to expire at various dates between 2024 and 2043 . For each of the years ended December 31, 2023, 2022 and 2021 , the Company did no t have any material unrecognized tax benefits and thus no interest and penalties related to unrecognized tax benefits were recorded. In addition, the Company does no t expect that the amount of unrecognized tax benefits will change significantly within the next twelve months. The Company files a federal income tax return in the United States and income tax returns in various state and foreign jurisdictions. All tax years are open for examination by the taxing authorities for both federal and state purposes. The Tax Cuts and Jobs Act (“TCJA”) requires taxpayers to capitalize and amortize research and development (“R&D”) expenditures under section 174 for tax years beginning after December 31, 2021. This rule became effective for the Company during 2022. Capitalized R&D costs were $ 31.6 million as of December 31, 2023 . The Company will amortize these costs for tax purposes over 5 years for R&D performed in the U.S. and over 15 years for R&D performed outside the U.S. In 2023 , all R&D was performed in the U.S.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Segment Information	(19) Segment Information Operating segments are identified as components of an enterprise about which separate, discrete financial information is available for evaluation by the chief operating decision maker in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company’s chief operating decision maker reviews consolidated operating results to make decisions about allocating resources and assessing performance for the entire Company. The Company reports two segments: Energy Industrial and Thermal Barrier. We evaluate segment performance based on the segment profit (loss) before corporate expenses. Summarized below are the Revenue and Segment Operating Profit for each reporting segment: Year Ended Year Ended Revenue Segment Operating Profit (Loss) December 31 December 31 2023 2022 2021 2023 2022 2021 (In thousands) Energy industrial $ 128,639 $ 124,807 $ 114,958 $ 34,162 $ 18,844 $ 14,486 Thermal barrier 110,079 55,557 6,664 22,759 ( 13,868 ) ( 4,549 ) Total $ 238,718 $ 180,364 $ 121,622 $ 56,921 $ 4,976 $ 9,937 Corporate expenses 106,124 84,221 50,536 Operating loss ( 49,203 ) ( 79,245 ) ( 40,599 ) Other expense, net 3,392 ( 3,493 ) 3,505 Net loss $ ( 45,811 ) $ ( 82,738 ) $ ( 37,094 ) Year Ended Depreciation Expense December 31, 2023 2022 2021 (In thousands) Energy industrial $ 10,720 $ 8,476 $ 9,440 Thermal barrier 4,598 746 — Consolidated depreciation expense $ 15,318 $ 9,222 $ 9,440 Total Assets December 31, 2023 2022 (In thousands) Energy industrial $ 93,168 $ 94,415 Thermal barrier 118,565 39,320 Total assets of reportable segments 211,733 133,735 Construction in progress 314,678 209,050 All other corporate assets 176,637 300,631 $ 703,048 $ 643,416 Information about the Company’s total revenues, based on shipment destination or services location, is presented in the following table: Year Ended December 31, 2023 2022 2021 ($ in thousands) Revenue: U.S. $ 151,037 $ 113,968 $ 66,837 International 87,681 66,396 54,785 Total $ 238,718 $ 180,364 $ 121,622

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	(20) Subsequent Events In January 2024, the Company was notified by a customer of an engineering change to one of the parts the Company manufactures for that customer to enable incremental productivity and support a set of broader system level changes that could drive higher demand for its parts. The Company has submitted a preliminary claim to the customer for reimbursement for estimated inventory and equipment losses incurred by the Company and its vendors due to potential obsolescence. The customer’s ordinary course process is to audit the claim to determine the proposed reimbursable amount. The Company expects the matter to be concluded by the second quarter of 2024, and currently estimates the potential impact to be in the range of zero to approximately $ 10.0 million. In January 2024 , we entered into a sale and leaseback arrangement, pursuant to which we sold certain equipment to an equipment leasing company for a one-time cash payment of $ 5.0 million and leased back such equipment from the leasing company. The associated monthly lease rents will be paid over the term of three years . On March 5, 2024, the Compensation and Leadership Development Committee of the Company’s Board of Directors (the "Committee") approved the cancellation of the outstanding, unearned portion of the performance-based restricted shares granted to certain employees pursuant to the Company’s 2014 Employee, Director and Consultant Equity Incentive Plan on June 29, 2021 (to the CEO) and June 2, 2022 (to certain other employees). The Committee determined that, based on current market conditions, the likelihood of achievement of any of the remaining performance hurdles applicable to the unearned restricted shares is remote, and that the unearned restricted shares therefore had ceased to have incentive value for the grantees. On March 6, 2024, the Company entered into cancellation agreements pursuant to which the applicable employees agreed to such cancellation. The cancellation of the unearned restricted shares resulted in an acceleration of the unamortized stock-based compensation charges of approximately $ 2.2 million.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2023
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	Schedule II VALUATION AND QUALIFYING ACCOUNTS (in thousands) Description Balance Charges Recoveries Deductions to Charges to Balance Year Ended December 31, 2023: Allowances for uncollectible accounts and sales returns and allowances $ 255 ( 93 ) — — 68 $ 230 Year Ended December 31, 2022: Allowances for uncollectible accounts and sales returns and allowances $ 150 115 — — ( 10 ) $ 255 Year Ended December 31, 2021: Allowances for uncollectible accounts and sales returns and allowances $ 442 ( 84 ) ( 208 ) — — $ 150 (a) Represents allowances for uncollectible accounts established through general and administrative expenses. (b) Represents recoveries of allowances for uncollectible accounts established through general and administrative expenses. (c) Represents actual write-offs of uncollectible accounts. (d) Represents net change in allowances for sales returns, recorded as contra-revenue.

Description of Business (Polici

Description of Business (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Nature of Business	Nature of Business Aspen Aerogels, Inc. (the Company) is an aerogel technology company that designs, develops and manufactures innovative, high-performance aerogel insulation used primarily in the energy industrial and sustainable insulation materials markets. In addition, the Company has introduced a line of aerogel thermal barriers for use in battery packs in the electric vehicle ("EV") market. The Company is also developing applications for its aerogel technology in the battery materials and a number of other high-potential markets. The Company maintains its corporate offices in Northborough, Massachusetts. The Company has three wholly owned subsidiaries: Aspen Aerogels Rhode Island, LLC, Aspen Aerogels Germany, GmbH and Aspen Aerogels Georgia, LLC.
Liquidity	Liquidity During the year ended December 31, 2023, the Company incurred a net loss of $ 45.8 million and used $ 42.6 million of cash in operations and $ 175.5 million of cash for capital expenditures. On February 15, 2022, the Company entered into a note purchase agreement with an affiliate of Koch Disruptive Technologies, LLC (Koch), relating to the issuance and sale of $ 100.0 million of the Company’s convertible debt. On November 29, 2022, the Company completed an underwritten public offering of 29,052,631 shares of our common stock at a public offering price of $ 9.50 per share. The Company received net proceeds of $ 267.5 million after deducting underwriting discounts and commissions of $ 8.1 million and offering expenses of approximately $ 0.5 million. On December 19, 2023, the Company entered into a securities purchase agreement with certain institutional investors named therein, pursuant to which the Company agreed to issue and sell, in a registered direct offering by the Company directly to the Investors an aggregate of 6,060,607 shares of the Company’s common stock, $ 0.00001 par value per share. The shares were sold to the Investors at a price per share of $ 12.375 per share. The net proceeds from the Offering, after deducting offering expenses, were approximately $ 74.4 million. The Company had unrestricted cash and cash equivalents of $ 139.7 million as of December 31, 2023. On November 28, 2022, the Company entered into a loan agreement with General Motors Holdings LLC, an entity affiliated with General Motors LLC, which provides for a multi-draw senior secured term loan in an aggregate principal amount of up to $ 100.0 million, available to the Company on a delayed draw basis beginning January 1, 2023 to September 30, 2023 , subject to certain conditions precedent to funding. On September 28, 2023, the Company amended the GM Loan Agreement to extend the draw period for the delayed GM Loan to a period beginning on the date that is twelve months prior to the date agreed upon by the Company and GM for the start of production at an aerogel manufacturing facility in Bulloch County, Georgia (the Plant) and ending on March 31, 2024 (or any later date approved in writing by GM at its sole discretion); extend the maturity date of the GM Loan from March 31, 2025 to September 30, 2025; and add financial covenants measured starting from the fiscal quarter ending December 31, 2024 and at the end of each fiscal quarter thereafter. The Company is increasing investment in the research and development of next-generation aerogel products and manufacturing process technologies. In addition, the Company has developed a number of promising aerogel products and technologies for the EV market. The Company believes that the commercial potential for the Company’s products and technology in the EV market is significant. Accordingly, the Company is hiring additional personnel, incurring additional operating expenses, and incurring significant capital expenditures to expand silica aerogel manufacturing capacity, build an automated thermal barrier fabrication operation, enhance research and development laboratory facilities and equipment, and construct a battery materials facility, among other efforts. The Company expects its existing cash balance will be sufficient to support current operating requirements, current research and development activities and the capital expenditures required to support the evolving commercial opportunity in the EV market and other strategic business initiatives. However, the Company plans to supplement its cash balance with equity financings, debt financings, equipment leasing, sale-leaseback transactions, customer prepayments, or government grant and loan programs to provide the additional capital necessary to purchase the capital equipment, construct the new facilities, establish the operations and complete the aerogel capacity expansions required to support these evolving commercial opportunities and strategic business initiatives.
Principles of Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements of the Company include the accounts of all its subsidiaries which are majority-owned, controlled by the Company or a variable interest entity (“VIE”) where the Company is the primary beneficiary. All significant intercompany accounts and transactions have been eliminated in consolidation. A VIE is an entity that lacks one or more of the characteristics of a voting interest entity. A VIE is defined as an entity in which equity investors do not have the characteristics of a controlling financial interest or do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties. The Company consolidates a VIE in accordance with ASC 810, Consolidation ("ASC 810") when it is the primary beneficiary of such VIE. As primary beneficiary, the Company has both the power to direct the activities that most significantly impact the economic performance of the VIE and a right to receive benefits or absorb losses of the entity that could be potentially significant to the VIE. The Company is required to reconsider its evaluation of whether to consolidate a VIE each reporting period, based upon changes in the facts and circumstances pertaining to the VIE. The Company evaluates the initial consolidation of each consolidated VIE, which includes a determination of whether the VIE constitutes the definition of a business in accordance with ASC 805, Business Combinations ("ASC 805"), by considering if substantially all of the fair value of the gross assets within the VIE are concentrated in either a single identifiable asset or group of single identifiable assets. Upon consolidation, the Company recognizes the assets acquired, the liabilities assumed, and any third-party ownership of membership interests as non-controlling interest as of the consolidation or acquisition date, measured at their relative fair values. In April 2022, the Company engaged Prodensa Servicios de Consultora to establish OPE Manufacturer Mexico S de RL de CV, a maquiladora located in Mexico with the express purposes of manufacturing thermal barrier PyroThin products and ultimately operating an automated fabrication facility for PyroThin. OPE is currently owned by Prodensa, which charges a management fee though there is an option for OPE to be purchased by Aspen after a period of 18 months . During the period between inception and the exercise of the purchase option, OPE operations are consolidated within the Company financial statements as of and for the year ended December 31, 2023 .
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements requires the Company to make a number of estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates and assumptions include allowances for doubtful accounts, sales returns and allowances, product warranty costs, inventory valuation, the carrying amount of property and equipment, right-of-use assets, lease liabilities, stock-based compensation, and deferred income taxes. The Company evaluates its estimates and assumptions on an on-going basis using historical experience and other factors, including current economic conditions, which are believed to be reasonable under the circumstances. Management adjusts such estimates and assumptions when facts and circumstances warrant. Illiquid credit markets, volatile equity markets, and declines in business investment can increase the uncertainty inherent in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in these estimates resulting from continuing changes in the economic environment will be reflected in the financial statements in future periods.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents include short-term, highly liquid instruments, which consist of money market accounts and high-quality debt securities issued by the U.S. government via cash sweep accounts. All cash and cash equivalents are maintained with major financial institutions in North America. Deposits with this financial institution may exceed the amount of insurance provided on such deposits; however, these deposits typically may be redeemed upon demand and, therefore, bear minimal risk.
Restricted Cash	Restricted Cash As of December 31, 2023, the Company had $ 0.2 million of restricted cash to support its outstanding letters of credit.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially expose the Company to concentrations of credit risk, consist principally of accounts receivable. The Company’s customers are primarily insulation distributors, insulation contractors, insulation fabricators and select energy and automotive end-users located throughout the world. The Company performs ongoing credit evaluations of its customers’ financial condition and generally requires no collateral to secure accounts receivable. The Company maintains an allowance for doubtful accounts based on its assessment of the collectability of accounts receivable. The Company reviews the allowance for doubtful accounts quarterly. During the year ended December 31, 2023, the Company recorded a charge for estimated customer uncollectible accounts receivable of less than $ 0.1 million. During the year ended December 31, 2022, the Company recorded a charge for estimated customer uncollectible accounts receivable of $ 0.1 million. During the year ended December 31, 2021, the Company did not record any charges for uncollectible accounts receivable. Allowance for doubtful accounts was $ 0.2 million and $ 0.3 million at December 31, 2023 and 2022, respectively. The Company does not have any off-balance-sheet credit exposure related to its customers. For the year ended December 31, 2023 , two customers represented 41 % and 14 % of total revenue, respectively. For the year ended December 31, 2022 , two customers represented 25 % and 22 % of total revenue, respectively. For the year ended December 31, 2021 , one customer represented 28 % of total revenue. At December 31, 2023 , the Company had two customers which accounted for 60 % and 6 % of accounts receivable, respectively. At December 31, 2022 , the Company had two customers which accounted for 44 % and 10 % of accounts receivable, respectively.
Inventories	Inventories Inventory consists of finished products, work-in-process, and raw materials. Inventories are carried at lower of cost, determined using the first-in, first-out (FIFO) method, and net realizable value. Cost includes materials, labor and manufacturing overhead. Manufacturing overhead is allocated to the costs of conversion based on normal capacity of the Company’s production facility. Abnormal freight, handling costs and material waste are expensed in the period it occurs. The Company periodically reviews its inventories and makes provisions as necessary for estimated excess, obsolete or damaged goods to ensure values approximate the lower of cost and net realizable value. The amount of any such provision is equal to the difference between the cost of inventory and the estimated net realizable value based upon assumptions about future demand, selling prices and market conditions.
Prepaid expenses and other current assets	Prepaid expenses and other current assets Prepaid expenses and other current assets primarily include value added tax and income tax receivables, prepayments of future services, and payments for pre-billed inventories.
Property, Plant and Equipment, Net	Property, Plant and Equipment, Net Property, plant and equipment are stated at cost. Expenditures for maintenance and repairs are charged to expense as incurred. Expenditures for major betterments are capitalized as additions to property, plant and equipment. Depreciation on plant and equipment is calculated on the straight-line method over the estimated useful lives of the assets. Assets related to leasehold improvements are amortized on a straight-line basis over the shorter of the lease term or estimated useful life of the asset. Assets utilized in the Company’s operations that are taken out of service with no future use are charged to cost of revenue or operating expenses, depending on the department in which the asset was utilized. Impairments of construction in progress are charged to operating expenses upon the determination of no future use.
Other Assets	Other Assets Other assets primarily include long-term deposits.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets are reviewed for impairment when events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. Recognition and measurement of a potential impairment is performed on assets grouped with other assets and liabilities at the lowest level where identifiable cash flows are largely independent of the cash flows of other assets and liabilities. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset or asset group to future undiscounted net cash flows expected to be generated by the asset or asset group. If the carrying amount of an asset or asset group exceeds its estimated undiscounted future cash flows, an impairment charge is recognized for the amount by which the carrying amount of the asset or asset group exceeds the fair value of the asset or asset group. Fair value is determined through various valuation techniques including discounted cash flow models, quoted market values and third-party independent appraisals, as considered necessary.
Leases	Leases The Company accounts for leases in accordance with FASB ASC Topic 842, Leases. The Company determines whether an arrangement is a lease at inception. For leases where the Company is the lessee, a lease liability and a right-of-use (ROU) asset is recognized for all leases, with the exception of short-term leases with terms of twelve months or less. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s payment obligations under the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term. To measure its lease liabilities, the Company uses its incremental borrowing rate or the rate implicit in the lease, if available. The Company calculates its incremental borrowing rate using a synthetic credit rating analysis based on Moody’s Building Materials Industry Rating Methodology. ROU assets also include any direct costs and prepaid lease payments but exclude any lease incentives received. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company elected the short-term lease recognition exemption for all leases that qualify. For leases that qualify for this exemption, the Company does not recognize ROU assets or lease liabilities. For lease agreements with lease and non-lease components, the Company accounts for each component separately. However, in the case of equipment leases, the Company accounts for lease and non-lease components as a single component. Refer to Note 11. Leases for additional information.
Foreign Currency Transactions	Foreign Currency Transactions The Company converts foreign currency transactions recognized in the Consolidated Statements of Operations to U.S. dollars by applying the exchange rate prevailing on the date of the transaction. Gains and losses arising from foreign currency transactions and the effects of remeasuring monetary assets and liabilities are recorded in general and administrative expenses, net in the Consolidated Statements of Operations .
Employee Retention Credits	Employee Retention Credits In March 2020, the Coronavirus Aid, Relief, and Economic Security Act was signed into law, providing numerous tax provisions and other stimulus measures, including the Employee Retention Credit: a refundable tax credit against certain employment taxes. The Taxpayer Certainty and Disaster Tax Relief Act of 2020 and the American Rescue Plan Act of 2021 extended and expanded the availability of the Employee Retention Credits. We qualified for the Employee Retention Credits in the third and fourth quarters of 2020 and the first quarter of 2021. In September 2023, we submitted filings for CARES Employee Retention Credits totaling $ 2.2 million that are reported in the accompanying condensed consolidated balance sheet within prepaid expenses and other current assets as of December 31, 2023, and in the accompanying statement of operations for the year ended December 31, 2023 .
Revenue Recognition	Revenue Recognition The Company recognizes revenue in accordance with Accounting Standards Codification 606, Revenue from Contracts with Customers (ASC 606). See note 3 for further details.
Warranty	Warranty The Company provides warranties for its products and records the estimated cost within cost of revenue in the period that the related revenue is recorded. The Company’s standard warranty period extends to one year from the date of shipment. This standard warranty provides that the Company’s products will be free from defects in material and workmanship, and will, under normal use, conform to the specifications for the product. The Company’s products may be utilized in systems that involve new technical demands and new configurations. Accordingly, the Company regularly reviews and assesses whether warranty reserves should be recorded in the period the related revenue is recorded. For an initial shipment of product for use in a system with new technical demands or new configurations and where the Company is unsure of meeting the customer’s specifications, the Company will defer the recognition of product revenue and related costs until written customer acceptance is obtained. The Company recorded warranty expense of $ 0.5 million during the year ended December 31, 2023 . The Company recorded warranty expense of $ 0.2 million during the year ended December 31, 2022 . The Company recorded warranty expense of less than $ 0.1 million during the year ended December 31, 2021 .
Shipping and Handling Costs	Shipping and Handling Costs Shipping and handling costs are classified as a component of cost of revenue. Customer payments of shipping and handling costs are recorded as product revenue.
Stock-based Compensation	Stock-based Compensation The Company grants share-based awards to its employees and non-employee directors. All share-based awards granted, including grants of stock options, restricted stock and restricted stock units (RSUs), are recognized in the statement of operations based on their fair value as of the date of grant. Expense is recognized on a straight-line basis over the requisite service period for all awards with service conditions. For performance-based awards, the grant date fair value is recognized as expense when the condition is probable of being achieved, and then on a graded basis over the requisite service period. The Company uses the Black-Scholes option-pricing model to determine the fair value of service-based option awards. The Black-Scholes model requires the use of a number of complex and subjective assumptions including fair value of the underlying security, the expected volatility of the underlying security, a risk-free interest rate and the expected term of the option. The fair value of restricted stock and RSUs is determined using the closing price of the Company’s common stock on the date of grant. All shares of restricted stock are not transferable until vested. Restricted stock is typically issued to non-employee directors and typically vests over a one-year period from the date of issuance. RSUs are issued to employees and typically vest over a three-year period from the date of issuance. The fair value of restricted stock and RSUs upon which vesting is solely service-based is expensed ratably over the vesting period. If the service condition for shares of restricted stock is not met for any reason, the shares of unvested restricted stock will be forfeited and returned to the Company. For stock awards that contain a market condition, the Company uses the Monte-Carlo simulation model to determine the fair value of the awards. In addition to the input assumptions used in the Black-Scholes model, the Monte-Carlo simulation model factors the probability that the specific market condition may or may not be satisfied into the valuation. Stock-based compensation expense for awards with a market condition is recognized on a straight-line basis over the requisite service period for each such award.
Research and Development	Research and Development Costs incurred in the Company’s research and development activities include compensation and related costs, services provided by third-party contractors, materials and supplies and are classified as research and development expenses as incurred.
Earnings per Share	Earnings per Share The Company calculates net loss per common share based on the weighted-average number of common shares outstanding during each period. Potential common stock equivalents are determined using the treasury stock method. The weighted-average number of common shares included in the computation of diluted net income (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options and RSUs. Common equivalent shares are excluded from the computation of diluted net loss per share if their effect is antidilutive.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. The Company accounts for uncertain tax positions using a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Differences between tax positions taken in a tax return and amounts recognized in the financial statements are recorded as adjustments to income taxes payable or receivable, or adjustments to deferred taxes, or both. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. The Company recognizes penalties and interest related to uncertain tax positions, if any, as a component of income tax expense.
Segments	Segments Operating segments are identified as components of an enterprise about which separate, discrete financial information is available for evaluation by the chief operating decision maker in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company’s chief operating decision maker reviews consolidated operating results to make decisions about allocating resources and assessing performance for the entire Company. The Company presently views its operations and manages its business as two operating segments. Leases The Company accounts for leases in accordance with FASB ASC Topic 842, Leases. The Company determines whether an arrangement is a lease at inception. For leases where the Company is the lessee, a lease liability and a right-of-use (ROU) asset is recognized for all leases, with the exception of short-term leases with terms of twelve months or less. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s payment obligations under the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term. To measure its lease liabilities, the Company uses its incremental borrowing rate or the rate implicit in the lease, if available. The Company calculates its incremental borrowing rate using a synthetic credit rating analysis based on Moody’s Building Materials Industry Rating Methodology. ROU assets also include any direct costs and prepaid lease payments but exclude any lease incentives received. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company elected the short-term lease recognition exemption for all leases that qualify. For leases that qualify for this exemption, the Company does not recognize ROU assets or lease liabilities. For lease agreements with lease and non-lease components, the Company accounts for each component separately. However, in the case of equipment leases, the Company accounts for lease and non-lease components as a single component. Refer to Note 11. Leases for additional information. Foreign Currency Transactions The Company converts foreign currency transactions recognized in the Consolidated Statements of Operations to U.S. dollars by applying the exchange rate prevailing on the date of the transaction. Gains and losses arising from foreign currency transactions and the effects of remeasuring monetary assets and liabilities are recorded in general and administrative expenses, net in the Consolidated Statements of Operations . Employee Retention Credits In March 2020, the Coronavirus Aid, Relief, and Economic Security Act was signed into law, providing numerous tax provisions and other stimulus measures, including the Employee Retention Credit: a refundable tax credit against certain employment taxes. The Taxpayer Certainty and Disaster Tax Relief Act of 2020 and the American Rescue Plan Act of 2021 extended and expanded the availability of the Employee Retention Credits. We qualified for the Employee Retention Credits in the third and fourth quarters of 2020 and the first quarter of 2021. In September 2023, we submitted filings for CARES Employee Retention Credits totaling $ 2.2 million that are reported in the accompanying condensed consolidated balance sheet within prepaid expenses and other current assets as of December 31, 2023, and in the accompanying statement of operations for the year ended December 31, 2023 .
Recently Issued Accounting Standards	Recently Issued Accounting Standards From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board or other standard setting bodies. Recently issued standards typically do not require adoption until a future effective date. Prior to their effective date, the Company evaluates the pronouncements to determine the potential effects of adoption to its consolidated financial statements. Standards Implemented Since December 31, 2022 The Company has not implemented any accounting standards that had a material impact on its consolidated financial statements during the year ended December 31, 2023. Standards to be Implemented After December 31, 2023 In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2023-07 Segment Reporting (Topic 280) Improvements to Reportable Segment Disclosures to enhance disclosures about significant segment expenses. This ASU is effective for the Company’s fiscal year 2024 and interim periods in fiscal year 2025. Early adoption is permitted. The Company is currently evaluating segment expense disclosures related to its annual report for fiscal year 2024. In December 2023, the FASB issued ASU 2023-09 Income Taxes (Topic 740) Improvements to Income Tax Disclosures that requires disclosure of disaggregated income taxes paid, prescribes standard categories for the components of the effective tax rate reconciliation, and modifies other income tax-related disclosures. This ASU is effective for the Company’s fiscal year 2025. Early adoption is permitted. The Company is currently evaluating income tax disclosures related to its annual report for fiscal year 2025. Although there are several other new accounting pronouncements issued by the FASB, the Company does not believe any of these accounting pronouncements had or will have a material impact on its Consolidated Financial Statements. The Company believes that the impact of recently issued accounting standards that are not yet effective will not have a material impact on its consolidated financial statements.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Summary of Revenue Disaggregated by Geographical Region and Source of Revenue	In the following tables, revenue is disaggregated by primary geographical region and source of revenue: December 31, 2023 U.S. International Total (In thousands) Geographical region Asia $ — $ 35,698 $ 35,698 Canada — 2,033 2,033 Europe — 42,731 42,731 Latin America — 7,219 7,219 U.S. 151,037 — 151,037 Total revenue $ 151,037 $ 87,681 $ 238,718 Source of revenue Energy industrial $ 52,838 $ 75,801 $ 128,639 Thermal barrier 98,199 11,880 110,079 Total revenue $ 151,037 $ 87,681 $ 238,718 December 31, 2022 U.S. International Total (In thousands) Geographical region Asia $ — $ 34,746 $ 34,746 Canada — 4,947 4,947 Europe — 22,239 22,239 Latin America — 4,464 4,464 U.S. 113,968 — 113,968 Total revenue $ 113,968 $ 66,396 $ 180,364 Source of revenue Energy industrial $ 64,699 $ 60,108 $ 124,807 Thermal barrier 49,269 6,288 55,557 Total revenue $ 113,968 $ 66,396 $ 180,364 December 31, 2021 U.S. International Total (In thousands) Geographical region Asia $ — $ 19,383 $ 19,383 Canada — 2,985 2,985 Europe — 27,924 27,924 Latin America — 4,493 4,493 U.S. 66,837 — 66,837 Total revenue $ 66,837 $ 54,785 $ 121,622 Source of revenue Energy industrial $ 60,299 $ 54,659 $ 114,958 Thermal barrier 6,538 126 6,664 Total revenue $ 66,837 $ 54,785 $ 121,622
Summary of Changes in Contract Assets and Contract Liabilities	The following table presents changes in the Company’s contract assets and contract liabilities during the year ended December 31, 2023: Balance at Additions Deductions Balance at (In thousands) Contract assets Thermal barrier 143 — ( 143 ) — Total contract assets $ 143 $ - $ ( 143 ) $ — Contract liabilities Deferred revenue Energy industrial $ 5,846 $ 17,484 $ ( 21,014 ) $ 2,316 Total contract liabilities $ 5,846 $ 17,484 $ ( 21,014 ) $ 2,316

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2023
Inventory Disclosure [Abstract]
Schedule of Inventories	Inventories consist of the following: December 31, 2023 2022 (In thousands) Raw material $ 24,735 $ 19,876 Work in process 7,936 2,204 Finished goods 6,518 458 Total $ 39,189 $ 22,538

Property, Plant and Equipment_2

Property, Plant and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Summary of Property, Plant and Equipment	Property, plant and equipment consist of the following: December 31, 2023 2022 Useful life (In thousands) Construction in progress $ 314,695 $ 209,056 — Buildings 25,473 24,016 30 years Machinery and equipment 185,339 136,607 3 — 10 years Computer equipment and software 9,495 10,239 3 years Leasehold improvements 23,514 9,226 Shorter of useful life or lease term Total 558,516 389,144 Accumulated depreciation and amortization ( 141,289 ) ( 129,921 ) Property, plant and equipment, net $ 417,227 $ 259,223

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following: December 31, 2023 2022 (In thousands) Employee compensation $ 16,876 $ 12,467 Other accrued expenses 5,935 3,536 Total $ 22,811 $ 16,003

Convertible Note - Related Pa_2

Convertible Note - Related Party (Tables)	12 Months Ended
	Dec. 31, 2023
Convertible Notes [Abstract]
Summary of Convertible Notes	In accordance with ASU 2020-06, the 2022 Convertible Note is accounted for as a single unit of account and consists of the following: December 31, December 31, 2023 2022 Convertible note, principal $ 100,000 $ 100,000 Payment in-kind 18,318 7,830 Discount on convertible note ( 3,209 ) ( 4,097 ) Debt issuance costs, net of accumulated amortization ( 117 ) ( 153 ) Convertible note $ 114,992 $ 103,580 In general, fair values determined by Level 1 inputs utilize observable inputs such as quoted prices in active markets for identical assets or liabilities. Fair values determined by Level 2 inputs utilize data points that are either directly or indirectly observable, such as quoted prices for similar instruments in active markets, interest rates and yield curves. Fair values determined by Level 3 inputs utilize unobservable data points in which there is little or no market data, which require the Company to develop its own assumptions for the asset or liability. The 2022 Convertible Note does not have current observable inputs such as recent trading prices (Level 3) and is measured at fair value using a combination of option pricing and discounted cash flow models and incorporate management’s assumptions for stock price, volatility and risk rate. The Company estimated the fair value of the 2022 Convertible Note is approximately $ 118.2 million as of December 31, 2023 . However, as the Company has not elected to utilize the fair value option, it is carried at amortized cost of $ 115.0 million.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Summary of Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities at December 31, 2023 are as follows: Year Operating (In thousands) 2024 $ 4,531 2025 4,373 2026 4,064 2027 3,793 2028 3,946 Thereafter 19,174 Total lease payments 39,881 Less imputed interest ( 16,101 ) Total lease liabilities $ 23,780

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Summary of Capitalized Implementation Costs are Classified on the Consolidated Balance Sheets	The Company is party to a cloud computing agreement that is a service contract for enterprise resource planning software. The agreement has a three-year term beginning on January 15, 2021, with option to renew. During the year ended December 31, 2023, the Company capitalized $ 1.3 million of costs related to implementation of the software that began to amortize during 2022 with a five year expected life. The capitalized implementation costs are classified on the consolidated balance sheets as follows: December 31, December 31, 2023 2022 (In thousands) Cloud computing costs included in other current assets $ 420 $ 420 Cloud computing costs included in other assets 1,590 1,590 Amortization of cloud computing costs ( 662 ) ( 242 ) Total capitalized cloud computing costs $ 1,348 $ 1,768

Employee Stock Ownership Plans

Employee Stock Ownership Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Stock Based Compensation Included in Cost of Sales or Operating Expenses	Stock-based compensation is included in cost of sales or operating expenses, as applicable, and consists of the following: Year Ended December 31, 2023 2022 2021 (In thousands) Cost of product revenue $ 583 $ 931 $ 510 Research and development expenses 799 1,166 750 Sales and marketing expenses 1,484 1,883 822 General and administrative expenses 8,088 5,405 3,094 Total stock-based compensation $ 10,954 $ 9,385 $ 5,176
Summary of Fair Value of Option Awards Estimated by Use of Black-Scholes Option Pricing Model	The following information relates to the fair value of the option awards estimated by use of the Black-Scholes option-pricing model: Year Ended December 31, 2023 2022 2021 Weighted average assumptions: Expected term (in years) 6.12 5.97 5.96 Expected volatility 70.04 % 61.85 % 59.80 % Risk free rate 4.08 % 2.13 % 0.86 % Expected dividend yield 0.00 % 0.00 % 0.00 % Weighted average fair value: Grant-date fair value of options granted $ 4.91 $ 14.20 $ 14.28 Grant-date fair value of options vested $ 9.63 $ 5.06 $ 2.91 Aggregate intrinsic value of options exercised $ 1,652,567 $ 1,306,245 $ 12,675,489
Summary of Stock Option Outstanding	The following table summarizes information about stock options outstanding: Number of Weighted Weighted Weighted Aggregate ($ in thousands, except share and per share data) Options outstanding at December 31, 2022 3,904,080 $ 7.12 $ 11.37 5.26 $ 16,486,864 Granted 2,021,250 $ 4.91 $ 7.46 Forfeited ( 300,788 ) $ 10.18 $ 17.25 Expired ( 66,846 ) $ 98.27 $ 82.78 Exercised ( 323,502 ) $ 2.59 $ 5.13 $ 1,652,567 Options outstanding at December 31, 2023 5,234,194 $ 5.21 $ 8.99 6.13 $ 41,225,602 Exercisable at December 31, 2023 3,002,950 $ 4.58 $ 8.52 6.13 $ 24,797,684 Expected to vest at December 31, 2023 2,231,244 $ 6.07 $ 9.62 2.09 $ 16,427,918
Summary of Grants, Vesting, and Forfeitures of RSUs	The following table provides detail of grants, vesting, and forfeitures of RSUs during 2023: Restricted Weighted Balance at December 31, 2022 257,075 $ 22.19 Granted 523,783 8.72 Vested ( 117,941 ) 18.97 Forfeited ( 88,670 ) 16.93 Balance at December 31, 2023 574,247 $ 11.38

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share	The computation of basic and diluted net loss per share consists of the following: Year ended December 31, 2023 2022 2021 (In thousands, except share and per share data) Numerator: Net loss $ ( 45,811 ) $ ( 82,738 ) $ ( 37,094 ) Denominator: Weighted average shares outstanding, basic and diluted 69,439,034 39,363,114 30,433,154 Net loss per share, basic and diluted $ ( 0.66 ) $ ( 2.10 ) $ ( 1.22 )
Summary of Potentially Dilutive Common Shares Excluded from Computation of Diluted Net Loss Per Share	Potentially dilutive common shares that were excluded from the computation of diluted net loss per share because they were anti-dilutive consist of the following: Year ended December 31, 2023 2022 2021 Common stock options 5,234,194 3,904,080 3,567,207 Restricted common stock units 574,247 257,075 350,195 Restricted common stock awards 881,674 23,886 14,934 Convertible note, if converted 3,951,833 3,601,533 — Total 10,641,948 7,786,574 3,932,336

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Reconciliation Between U.S. Statutory Income Tax Rate and Company's Effective Rate	Year Ended December 31, 2023 2022 2021 U.S. federal income tax statutory rate 21 % 21 % 21 % Permanent differences — 1 % 10 % State tax, net of federal benefit 7 % 5 % 5 % Changes in valuation allowance for deferred tax assets ( 17 )% ( 27 )% ( 35 )% Stock-based compensation ( 7 )% — % — % Expiring net operating losses — % — % ( 1 )% Other 2 % — % — % State rate change ( 6 )% — % — % Effective tax rate — — — The tax effects of temporary differences between financial statement and tax accounting that gave rise to significant portions of the Company’s deferred tax assets and deferred tax liabilities at
Schedule of Deferred Tax Assets and Deferred Tax Liabilities	December 31, 2023 and 2022 are presented below: December 31, 2023 2022 (In thousands) Deferred tax assets: Net operating loss carryforwards $ 82,563 $ 81,943 Stock-based compensation 3,076 6,677 Operating lease liabilities 5,997 4,065 Capitalized research and development 6,320 3,916 Tax credit carryforwards 4,261 448 Reserves and accruals 6,180 3,160 Interest expense limitation 929 1,257 Total gross deferred tax assets 109,326 101,466 Deferred tax liabilities: Depreciation ( 1,125 ) ( 1,879 ) Operating lease right-of-use assets ( 4,340 ) ( 3,081 ) Total deferred tax liabilities ( 5,465 ) ( 4,960 ) Total deferred tax assets and liabilities 103,861 96,506 Valuation allowance ( 103,861 ) ( 96,506 ) Net deferred tax asset $ — $ —

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Summary of Revenue and Segment Operating Profit	Summarized below are the Revenue and Segment Operating Profit for each reporting segment: Year Ended Year Ended Revenue Segment Operating Profit (Loss) December 31 December 31 2023 2022 2021 2023 2022 2021 (In thousands) Energy industrial $ 128,639 $ 124,807 $ 114,958 $ 34,162 $ 18,844 $ 14,486 Thermal barrier 110,079 55,557 6,664 22,759 ( 13,868 ) ( 4,549 ) Total $ 238,718 $ 180,364 $ 121,622 $ 56,921 $ 4,976 $ 9,937 Corporate expenses 106,124 84,221 50,536 Operating loss ( 49,203 ) ( 79,245 ) ( 40,599 ) Other expense, net 3,392 ( 3,493 ) 3,505 Net loss $ ( 45,811 ) $ ( 82,738 ) $ ( 37,094 ) Year Ended Depreciation Expense December 31, 2023 2022 2021 (In thousands) Energy industrial $ 10,720 $ 8,476 $ 9,440 Thermal barrier 4,598 746 — Consolidated depreciation expense $ 15,318 $ 9,222 $ 9,440 Total Assets December 31, 2023 2022 (In thousands) Energy industrial $ 93,168 $ 94,415 Thermal barrier 118,565 39,320 Total assets of reportable segments 211,733 133,735 Construction in progress 314,678 209,050 All other corporate assets 176,637 300,631 $ 703,048 $ 643,416
Schedule of Revenues, Based on Shipment Destination or Research Services Location	Information about the Company’s total revenues, based on shipment destination or services location, is presented in the following table: Year Ended December 31, 2023 2022 2021 ($ in thousands) Revenue: U.S. $ 151,037 $ 113,968 $ 66,837 International 87,681 66,396 54,785 Total $ 238,718 $ 180,364 $ 121,622

Description of Business - Addit

Description of Business - Additional Information (Detail) $ / shares in Units, $ in Thousands				12 Months Ended
	Dec. 19, 2023 USD ($) $ / shares shares	Nov. 29, 2022 USD ($) $ / shares shares	Nov. 28, 2022 USD ($)	Dec. 31, 2023 USD ($) Subsidiary $ / shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($)	Feb. 15, 2022 USD ($)
Basis Of Presentation [Line Items]
Number of Subsidiaries | Subsidiary				3
Net loss incurred				$ 45,811	$ 82,738	$ 37,094
Cash used in operations				42,612	94,399	18,628
Cash for capital expenditures				175,500
Proceeds from offering, net	$ 74,400
Unrestricted cash and cash equivalents				139,723	281,335
Issuance and sale of convertible debt				$ 114,992	$ 103,580		$ 100,000
Underwritten public offering, shares issued | shares	6,060,607
Common stock, par value | $ / shares	$ 0.00001			$ 0.00001	$ 0.00001
Public offering price | $ / shares	$ 12.375
General Motors Holdings LLC [Member] | Loan Agreement [Member]
Basis Of Presentation [Line Items]
Aggregate principal amount			$ 100,000
Senior secured term loan, Draw beginning date			Jan. 01, 2023
Senior secured term loan, Draw Endining date			Sep. 30, 2023
At The Market Offering [Member]
Basis Of Presentation [Line Items]
Proceeds from offering, net					$ 73,349	$ 19,420
Koch Strategic Platforms (KSP) [Member]
Basis Of Presentation [Line Items]
Proceeds from offering, net				$ 73,500
Underwritten Public Offering [Member]
Basis Of Presentation [Line Items]
Proceeds from offering, net		$ 267,500			$ 267,948
Underwritten public offering, shares issued | shares		29,052,631
Public offering price | $ / shares		$ 9.5
Underwriting discounts and commissions		$ 8,100
Offering expenses		$ 500

Summary of Basis of Presentat_2

Summary of Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) $ in Thousands		12 Months Ended
	Jun. 02, 2022 USD ($)	Dec. 31, 2023 USD ($) Segment Customer	Dec. 31, 2022 USD ($) Customer	Dec. 31, 2021 USD ($)	Sep. 30, 2023 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Charge for uncollectible accounts receivable		$ (93)	$ 115	$ (85)
Restricted cash		248	1,226
Allowance for doubtful accounts		$ 200	300
Standard product warranty period		1 year
Warranty expense		$ 500	$ 200	$ 100
Period of option to purchase		18 months
Number of segment | Segment		2
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Charge for uncollectible accounts receivable		$ 100
Restricted Stock Units [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock-based award vesting period		3 years
Stock-based awards granted to purchase common stock, grant date fair value	$ 4,000
Restricted Stock Units [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock-based award vesting period	3 years	3 years
Restricted Stock Units [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock-based award vesting period	5 years	4 years
Non-Employee Directors [Member] | Restricted Common Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock-based award vesting period		1 year
CARES Act [Member]
Summary Of Significant Accounting Policies [Line Items]
Employee Retention Credits Receivable					$ 2,200
Total Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of customers | Customer		2	2
Total Revenue [Member] | Customer Concentration Risk [Member] | Customer A [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		41%	25%	28%
Total Revenue [Member] | Customer Concentration Risk [Member] | Customer B [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		14%	22%
Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of customers | Customer		2	2
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer A [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		44%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer B [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		10%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer One [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		60%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer Two [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		6%

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue Recognition [Line Items]
Warranty expense	$ 500	$ 200	$ 100
Revenue from Contract with Customer, Excluding Assessed Tax	238,718	180,364	121,622
Deferred revenue, revenue recognized	5,800
Maximum [Member]
Revenue Recognition [Line Items]
Sales return reserves	200	100
Energy Industrial [Member]
Revenue Recognition [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 128,639	$ 124,807	$ 114,958

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Summary of Revenue Disaggregated by Geographical Region and Source of Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation Of Revenue [Line Items]
Total revenue	$ 238,718	$ 180,364	$ 121,622
Energy Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	128,639	124,807	114,958
Thermal Barrier [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	110,079	55,557	6,664
Asia [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	35,698	34,746	19,383
Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	2,033	4,947	2,985
Europe [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	42,731	22,239	27,924
Latin America [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	7,219	4,464	4,493
U.S. [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	151,037	113,968	66,837
U.S. [Member] | Energy Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	52,838	64,699	60,299
U.S. [Member] | Thermal Barrier [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	98,199	49,269	6,538
International [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	87,681	66,396	54,785
International [Member] | Energy Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	75,801	60,108	54,659
International [Member] | Thermal Barrier [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 11,880	$ 6,288	$ 126

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Summary of Changes in Contract Assets and Contract Liabilities (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Contract assets
Beginning Balance	$ 143
Additions	0
Deductions	(143)
Ending Balance	0
Contract liabilities
Beginning Balance	5,846
Additions	17,484
Deductions	(21,014)
Ending Balance	2,316
Thermal Barrier [Member]
Contract assets
Beginning Balance	143
Additions	0
Deductions	(143)
Ending Balance	0
Energy Industrial [Member]
Contract liabilities
Beginning Balance	5,846
Additions	17,484
Deductions	(21,014)
Ending Balance	$ 2,316

Inventories - Schedule of Inven

Inventories - Schedule of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Raw material	$ 24,735	$ 19,876
Work in process	7,936	2,204
Finished goods	6,518	458
Total	$ 39,189	$ 22,538

Property, Plant and Equipment_3

Property, Plant and Equipment, Net - Summary of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 558,516	$ 389,144
Accumulated depreciation and amortization	(141,289)	(129,921)
Property, plant and equipment, net	417,227	259,223
Construction in Progress [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, gross	314,695	209,056
Buildings [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 25,473	24,016
Property, plant and equipment, Useful life	30 years
Machinery and Equipment [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 185,339	136,607
Machinery and Equipment [Member] | Minimum [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	3 years
Machinery and Equipment [Member] | Maximum [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	10 years
Computer Equipment and Software [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 9,495	10,239
Property, plant and equipment, Useful life	3 years
Leasehold Improvements [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 23,514	$ 9,226
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	Property, plant and equipment, net

Property, Plant and Equipment_4

Property, Plant and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property Plant and Equipment [Line Items]
Depreciation	$ 15,318	$ 9,222	$ 9,440
Property, plant and equipment, gross	558,516	389,144
Capitalized Interest	6,084	2,723
Construction in Progress [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, gross	314,695	209,056
Rhode Island [Member] | Construction in Progress [Member]
Property Plant and Equipment [Line Items]
Property, plant and equipment, gross	314,700	209,100
Georgia [Member]
Property Plant and Equipment [Line Items]
Pre-construction costs	279,700	164,500
Georgia [Member] | Construction in Progress [Member]
Property Plant and Equipment [Line Items]
Capitalized Interest	$ 6,100	$ 2,700

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued Liabilities, Current [Abstract]
Employee compensation	$ 16,876	$ 12,467
Other accrued expenses	5,935	3,536
Total	$ 22,811	$ 16,003

Revolving Line of Credit - Addi

Revolving Line of Credit - Additional Information (Detail) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Line of Credit Facility [Line Items]
Restricted cash to support our outstanding letters of credit	$ 248,000	$ 1,226,000
Silicon Valley Bank Credit Facility [Member] | Loan Agreement [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility amount withdrawn	$ 0	$ 0

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Dec. 19, 2023	Nov. 28, 2022	Mar. 28, 2022	Jun. 29, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Common stock sold	6,060,607
Common stock purchase price	$ 12.375
Proceeds from offering, net	$ 74,400
Accounts payable					$ 51,094	$ 54,728
Koch Strategic Platforms L L C [Member]
Related Party Transaction [Line Items]
Common stock issuance fees and offering expenses				$ 1,500
Proceeds from offering, net					73,500
Koch Strategic Platforms L L C [Member] | Construction in Progress [Member]
Related Party Transaction [Line Items]
Costs recorded as a component of construction in progress						$ 8,900
Common Stock [Member] | Private Placement [Member]
Related Party Transaction [Line Items]
Common stock sold						1,791,986	3,462,124
Wood River Capital, LLC [Member] | 2022 Convertible Notes [Member]
Related Party Transaction [Line Items]
Issuance and sale of convertible notes						$ 100,000
Wood River Capital, LLC [Member] | Private Placement [Member]
Related Party Transaction [Line Items]
Common stock purchase price		$ 9.5	$ 27.902
Proceeds from offering, net		$ 100,000	$ 50,000
Wood River Capital, LLC [Member] | Common Stock [Member] | Private Placement [Member]
Related Party Transaction [Line Items]
Common stock sold		10,526,316	1,791,986
Spring Creek Capital, LLC [Member] | Common Stock [Member] | Private Placement [Member]
Related Party Transaction [Line Items]
Common stock sold				3,462,124
Robert M. Gervis [Member] | At-The-Market Offering [Member] | Sales Agreement [Member]
Related Party Transaction [Line Items]
Proceeds from offering, net						$ 4,400
Robert M. Gervis [Member] | Common Stock [Member] | At-The-Market Offering [Member] | Sales Agreement [Member]
Related Party Transaction [Line Items]
Common stock sold						135,870
Koch Disruptive Technologies LLC [Member]
Related Party Transaction [Line Items]
Accounts payable					2,800
Koch Disruptive Technologies LLC [Member] | Construction in Progress [Member]
Related Party Transaction [Line Items]
Costs recorded as a component of construction in progress					$ 8,600

Convertible Note - Related Pa_3

Convertible Note - Related Party - Additional Information (Detail)				12 Months Ended
	Nov. 28, 2022 $ / shares	Nov. 27, 2022 $ / shares	Feb. 15, 2022 USD ($)	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($)	Dec. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)
Convertible Notes [Line Items]
Issuance and sale of convertible notes				$ 100,000,000	$ 100,000,000
Debt instrument, interest rate terms				Interest on the 2022 Convertible Note is payable semi-annually in arrears on June 30 and December 30. The Company, at its option, is permitted to settle each semi-annual interest payment in cash, in-kind, or any combination thereof.
Payment in-kind				$ 18,318,000	7,830,000
Debt issuance costs				$ 117,000	153,000
Purchase price of notes percentage				100%
Payment in-kind						$ 5,400	$ 5,100,000	$ 4,900,000	$ 2,900,000
Maximum [Member]
Convertible Notes [Line Items]
Debt issuance costs					200,000
SOFR Plus [Member]
Convertible Notes [Line Items]
Debt instrument, interest rate				5.50%
SOFR Plus [Member] | Floor Rate [Member]
Convertible Notes [Line Items]
Debt instrument, interest rate				1%
SOFR Plus [Member] | Cap Rate [Member]
Convertible Notes [Line Items]
Debt instrument, interest rate				3%
SOFR Plus [Member] | PIK Interest [Member]
Convertible Notes [Line Items]
Debt instrument, interest rate				6.50%
2022 Convertible Notes [Member]
Convertible Notes [Line Items]
Convertible notes, fair value				$ 118,200,000
Convertible debt carried at amortized cost				$ 115,000,000
Initial conversion rate of convertible notes				33.4001
Common stock per capitalized principal | $ / shares				$ 1,000
Conversion notes effective conversion price per share | $ / shares				$ 29.936625
Common stock issuable upon conversion of convertible notes | shares				3,951,833
Percentage of common stock closing price per share of conversion price				130%
Number of trading days on conversion price				20 consecutive trading days
Convertible notes redemption terms				The 2022 Convertible Note is redeemable at the Company’s option at any time and in the event that the volume weighted average price of the Company’s common stock for the 10 trading days immediately preceding the date on which the Company provides the redemption notice has been at least 130% of the Conversion Price then in effect at a redemption price of 100% of the principal amount, plus accrued and unpaid interest (excluding the redemption date), plus the Make-Whole Amount.
Convertible notes redemption percentage				130%
Redemption price, percentage of principal amount redeemed				100%
Interest on convertible debt				$ 10,500,000	7,800,000
Capitalized interest on convertible debt				$ 6,100,000	$ 2,700,000
2022 Convertible Notes [Member] | Wood River Capital, LLC [Member]
Convertible Notes [Line Items]
Initial conversion rate of convertible notes	33.4001	28.623257
Common stock per capitalized principal | $ / shares	$ 1,000	$ 1,000
Conversion notes effective conversion price per share | $ / shares	29.936625	$ 34.936625
Conversion notes effective conversion price per share decrease | $ / shares	$ 5
2022 Convertible Notes [Member] | Koch Strategic Platforms (KSP) [Member]
Convertible Notes [Line Items]
Issuance and sale of convertible notes			$ 100,000,000
Debt instrument, issuance date			Feb. 15, 2022
Existing maturity date			Feb. 18, 2027	Feb. 18, 2027

Convertible Note - Related Pa_4

Convertible Note - Related Party - Summary of Convertible Notes (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Feb. 15, 2022
Convertible Notes [Abstract]
Convertible note, principal	$ 100,000	$ 100,000
Payment in-kind	18,318	7,830
Discount on convertible note	(3,209)	4,097
Debt issuance costs, net of accumulated amortization	(117)	(153)
Convertible note	$ 114,992	$ 103,580	$ 100,000

Other Income (Expense) - Additi

Other Income (Expense) - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Interest expense, net			$ (3,500,000)
Interest income (expense), net	$ 6,534,000	$ 1,617,000	$ (229,000)
CARES Act refundable tax credit percentage			70%	50%
CARES Act qualified wages per employee for refundable tax credit			$ 10,000	$ 10,000
Prepaid Expenses and Other Current Assets [Member]
Related Party Transaction [Line Items]
CARES Act Employee Retention Credits	2,200,000
Maximum [Member]
Related Party Transaction [Line Items]
CARES Act refundable tax credit				$ 5,000
Related Party [Member]
Related Party Transaction [Line Items]
Interest expense, related party	$ 5,300,000	$ 5,100,000

Leases - Additional Information

Leases - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2016 USD ($) ft²
Lessee, Lease, Description [Line Items]
Operating lease expiry year	2034
Operating lease cost	$ 5,300,000	$ 4,000,000
Cash payments related to operating lease liabilities	$ 4,900,000	3,600,000
Operating lease, weighted average remaining lease term	9 years
Operating lease, weighted average discount rate, percent	12%
Operating lease liability payments not yet commenced	$ 0
Restricted cash	248,000	1,226,000
Silicon Valley Bank Credit Facility [Member] | Revolving Credit Facility [Member]
Lessee, Lease, Description [Line Items]
Restricted cash	200,000
Letters of credit outstanding	$ 1,200,000	$ 1,200,000
Loan termination date	Nov. 28, 2022
Landlord [Member] | Industrial Real Estate Lease [Member]
Lessee, Lease, Description [Line Items]
Number of square feet for lease | ft²			51,650
Lease commence date			Jan. 01, 2017
Lease end date			Dec. 31, 2031
Lease annual base rent			$ 478,000
Operating Lease Rent Increase Percent			3%
Operating Lease Extended Term			5 years
Amount receivables as an aid to construction of improvements of the leased premise			$ 1,200,000

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Leases [Abstract]
2024	$ 4,531
2025	4,373
2026	4,064
2027	3,793
2028	3,946
Thereafter	19,174
Total lease payments	39,881
Less imputed interest	(16,101)
Total lease liabilities	$ 23,780

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021	Dec. 31, 2016 USD ($) ft²
Commitments And Contingencies [Line Items]
Restricted cash to support our outstanding letters of credit	$ 248,000	$ 1,226,000
Rent expense incurred under operating leases	5,300,000	4,000,000
Purchase commitments	267,300,000
Capital commitments	$ 202,600,000
Purchase commitments spent over period	3 years
Silicon Valley Bank Credit Facility [Member] | Revolving Credit Facility [Member]
Commitments And Contingencies [Line Items]
Restricted cash to support our outstanding letters of credit	$ 200,000
Letters of credit outstanding	$ 1,200,000	1,200,000
Loan termination date	Nov. 28, 2022
Landlord [Member] | Lease Agreement [Member]
Commitments And Contingencies [Line Items]
Number of square feet for lease | ft²				51,650
Lease end date				Dec. 31, 2031
Lease commence date				Jan. 01, 2017
Lease annual base rent				$ 478,000
Lease increased percentage				3%
Lease extended term				5 years
Amount receivables as an aid to construction of improvements of the leased premise				$ 1,200,000
Cloud Computing Agreement [Member] | Enterprise Resource Planning Software [Member]
Commitments And Contingencies [Line Items]
Debt instrument, maturity term			3 years
Capitalized costs related to implementation of agreement		$ 1,300,000
Thermal Barrier Contracts [Member] | OEM [Member]
Commitments And Contingencies [Line Items]
Purchase commitment, description	While the OEM has agreed to purchase its requirement for Barriers from the Company for locations to be designated from time to time by the OEM, it has no obligation to purchase any minimum quantity of Barriers under the Contracts.

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Capitalized Implementation Costs are Classified on the Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Cloud computing costs included in other current assets	$ 420	$ 420
Cloud computing costs included in other assets	1,590	1,590
Amortization of cloud computing costs	662	(242)
Total capitalized cloud computing costs	$ 1,348	$ 1,768

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - shares	Dec. 31, 2023	Dec. 31, 2022
Equity [Abstract]
Total number of shares authorized	255,000,000	255,000,000
Common stock, shares authorized	250,000,000	250,000,000
Preferred stock, shares authorized	5,000,000	5,000,000

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Exercise Price And Additional Disclosures [Abstract]
Matching contribution during the period	$ 1.5	$ 1.2	$ 0.3

Employee Stock Ownership Plan_2

Employee Stock Ownership Plans - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Jun. 02, 2022	Jun. 29, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards granted to purchase common stock			2,021,250
Restricted common stock issued			76,503,151	69,994,963
Stock compensation expense			$ 10,954	$ 9,385	$ 5,176
Number of comparable companies for expected volatility			Company used its historical volatility as a basis to estimate expected volatility in the valuation of stock options.
Expected dividend yield			0%	0%	0%
Expected volatility			70.04%	61.85%	59.80%
Risk free rate			4.08%	2.13%	0.86%
2014 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance			5,808,440
Increased number of shares available for future grant			2,139,794
Number of shares either issued or reserved in connection with statutory tax withholdings			5,173,760
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			3 years
Stock-based awards granted to purchase common stock, grant date fair value	$ 4,000
Restricted common stock issued	53,590
Expected volatility	63.40%
Risk free rate	2.92%
Shares outstanding			574,247	257,075
Restricted Stock Units [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			1 year
Restricted Stock Units [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested options grants			$ 4,400
Unrecognized compensation cost period for recognition			1 year 10 months 24 days
Restricted Stock Units [Member] | 2014 Equity Plan [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			1 year
Restricted Stock Units [Member] | 2014 Equity Plan [Member] | Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards granted to purchase common stock, grant date fair value		$ 6,500
Stock-based awards shares awarded		461,616	461,616		461,616
Expected volatility					59.30%
Risk free rate					0.89%
Restricted Stock Units [Member] | 2014 Equity Plan [Member] | Other Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards shares awarded			375,130
Restricted Stock Units [Member] | 2023 Equity Plan [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards granted to purchase common stock			44,928
Stock-based awards granted to purchase common stock, grant date fair value			$ 300
Restricted Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding			881,674
Restricted Common Stock [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards granted to purchase common stock			44,928
Restricted Common Stock [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			1 year
Restricted Common Stock [Member] | 2014 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			3 years
Restricted Common Stock [Member] | 2023 Equity Plan [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			1 year
Restricted Common Stock [Member] | Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards granted to purchase common stock			523,783
Stock-based awards granted to purchase common stock, grant date fair value			$ 4,600
Non-Qualified Stock Options [Member] | 2014 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			3 years
Non-Qualified Stock Options [Member] | 2014 Equity Plan [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			1 year
Non-Qualified Stock Options [Member] | 2023 Equity Plan [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards granted to purchase common stock			46,272
Stock-based awards granted to purchase common stock, grant date fair value			$ 200
Non-Qualified Stock Options [Member] | Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards granted to purchase common stock			1,974,978
Stock-based awards granted to purchase common stock, grant date fair value			$ 9,700
Service Based Awards [Member] | 2014 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			3 years
Service Based Awards [Member] | Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested options grants			$ 9,700
Unrecognized compensation cost period for recognition			2 years 1 month 2 days
Restricted Stock and Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding			1,377,796
Total intrinsic value			$ 1,300	$ 7,400
Restricted Stock Awards [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested options grants			$ 100
Unrecognized compensation cost period for recognition			5 months 1 day
Restricted Stock Awards [Member] | Chief Executive Officer and Certain Other Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested options grants			$ 4,100
Unrecognized compensation cost period for recognition			1 year 29 days
Minimum [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period	3 years		3 years
Minimum [Member] | Restricted Stock Units [Member] | 2014 Equity Plan [Member] | Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period		3 years			3 years
Minimum [Member] | Restricted Stock Units [Member] | 2023 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			3 years
Maximum [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period	5 years		4 years
Maximum [Member] | Restricted Stock Units [Member] | 2014 Equity Plan [Member] | Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period		5 years			5 years
Maximum [Member] | Restricted Stock Units [Member] | 2023 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based award vesting period			4 years

Employee Stock Ownership Plan_3

Employee Stock Ownership Plans - Summary of Stock Based Compensation Included in Cost of Sales or Operating Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 10,954	$ 9,385	$ 5,176
Cost of Product Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	583	931	510
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	799	1,166	750
Sales and Marketing Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	1,484	1,883	822
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 8,088	$ 5,405	$ 3,094

Employee Stock Ownership Plan_4

Employee Stock Ownership Plans - Summary of Fair Value of Option Awards Estimated by Use of Black-Scholes Option Pricing Model (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Weighted average assumptions:
Expected term (in years)	6 years 1 month 13 days	5 years 11 months 19 days	5 years 11 months 15 days
Expected volatility	70.04%	61.85%	59.80%
Risk free rate	4.08%	2.13%	0.86%
Expected dividend yield	0%	0%	0%
Weighted average fair value:
Grant-date fair value of options granted	$ 4.91	$ 14.2	$ 14.28
Grant-date fair value of options vested	$ 9.63	$ 5.06	$ 2.91
Aggregate intrinsic value of options exercised	$ 1,652,567	$ 1,306,245	$ 12,675,489

Employee Stock Ownership Plan_5

Employee Stock Ownership Plans - Summary of Stock Option Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Number of Shares, Beginning Balance	3,904,080
Number of Shares, Granted	2,021,250
Number of Shares, Forfeited	(300,788)
Number of Shares, Expired	(66,846)
Number of Shares, Exercised	(323,502)
Number of Shares, Ending Balance	5,234,194	3,904,080
Number of Shares, Exercisable at December 31, 2023	3,002,950
Number of Shares, Expected to vest at December 31, 2023	2,231,244
Weighted Average Grant Date Fair Value Per Share, Beginning Balance	$ 7.12
Weighted Average Grant Date Fair Value Per Share, Granted	4.91	$ 14.2	$ 14.28
Weighted Average Grant Date Fair Value Per Share, Forfeited	10.18
Weighted Average Grant Date Fair Value Per Share, Expired	98.27
Weighted Average Grant Date Fair Value Per Share, Exercised	2.59
Weighted Average Grant Date Fair Value Per Share, Ending Balance	5.21	7.12
Weighted Average Grant Date Fair Value Per Share, Exercisable at December 31, 2023	4.58
Weighted Average Grant Date Fair Value Per Share, Expected to vest at December 31, 2023	6.07
Weighted Average Exercise Price Per Share, Beginning Balance	11.37
Weighted Average Exercise Price Per Share, Granted	7.46
Weighted Average Exercise Price Per Share, Forfeited	17.25
Weighted Average Exercise Price Per Share, Expired	82.78
Weighted Average Exercise Price Per Share, Exercised	5.13
Weighted Average Exercise Price Per Share, Ending Balance	8.99	$ 11.37
Weighted Average Exercise Price Per Share, Exercisable at December 31, 2023	8.52
Weighted Average Exercise Price Per Share, Expected to vest at December 31, 2023	$ 9.62
Weighted Average Remaining Contractual Term, Outstanding	6 years 1 month 17 days	5 years 3 months 3 days
Weighted Average Remaining Contractual Term, Exercisable at December 31, 2023	6 years 1 month 17 days
Weighted Average Remaining Contractual Term, Expected to vest at December 31, 2023	2 years 1 month 2 days
Aggregate Intrinsic Value, Beginning Balance	$ 16,486,864
Aggregate Intrinsic Value, Exercised	1,652,567	$ 1,306,245	$ 12,675,489
Aggregate Intrinsic Value, Ending Balance	41,225,602	$ 16,486,864
Aggregate Intrinsic Value, Exercisable at December 31, 2023	24,797,684
Aggregate Intrinsic Value, Expected to vest at December 31, 2023	$ 16,427,918

Employee Stock Ownership Plan_6

Employee Stock Ownership Plans - Summary of Grants, Vesting, and Forfeitures of RSUs (Detail) - Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Beginning Balance | shares	257,075
Restricted Stock Units, Granted | shares	523,783
Restricted Stock Units, Vested | shares	(117,941)
Restricted Stock Units, Forfeited | shares	(88,670)
Restricted Stock Units, Ending Balance | shares	574,247
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 22.19
Weighted Average Grant Date Fair Value, Granted | $ / shares	8.72
Weighted Average Grant Date Fair Value, Vested | $ / shares	18.97
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	16.93
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 11.38

CARES Act Payroll Tax Deferral

CARES Act Payroll Tax Deferral - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Other Liabilities Disclosure [Abstract]
Deferred employer payroll tax obligation	$ 0.9
Employer payroll tax obligation period	March 27, 2020 to December 31, 2020
Percentage of deferred tax balance	50%
Remittance date of deferred tax balance	Dec. 31, 2021
Remaining percentage of deferred tax balance	50%
Remittance date of deferred tax balance, remaining percentage	Dec. 31, 2022

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss	$ (45,811)	$ (82,738)	$ (37,094)
Denominator:
Weighted average shares outstanding, basic	69,439,034	39,363,114	30,433,154
Weighted average shares outstanding, diluted	69,439,034	39,363,114	30,433,154
Net loss per share, basic	$ (0.66)	$ (2.1)	$ (1.22)
Net loss per share, diluted	$ (0.66)	$ (2.1)	$ (1.22)

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Potentially Dilutive Common Shares Excluded from Computation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive Securities	10,641,948	7,786,574	3,932,336
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive Securities	5,234,194	3,904,080	3,567,207
Restricted Common Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive Securities	574,247	257,075	350,195
Restricted Common Stock Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive Securities	881,674	23,886	14,934
Convertible Note If Converted [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive Securities	3,951,833	3,601,533

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation Between U.S. Statutory Income Tax Rate and Company's Effective Rate (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S. federal income tax statutory rate	21%	21%	21%
Permanent differences		1%	10%
State tax, net of federal benefit	7%	5%	5%
Changes in valuation allowance for deferred tax assets	(17.00%)	(27.00%)	(35.00%)
Stock-based compensation	(7.00%)	0%	0%
Expiring net operating losses			(1.00%)
Other	2%	0%	0%
State rate change	(6.00%)	0%	0%
Effective tax rate	0%	0%	0%

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 82,563	$ 81,943
Stock-based compensation	3,076	6,677
Operating lease liabilities	5,997	4,065
Capitalized research and development	6,320	3,916
Tax credit carryforwards	4,261	448
Reserves and accruals	6,180	3,160
Interest expense limitation	929	1,257
Total gross deferred tax assets	109,326	101,466
Deferred tax liabilities:
Depreciation	(1,125)	(1,879)
Operating lease right-of-use assets	(4,340)	(3,081)
Total deferred tax liabilities	(5,465)	(4,960)
Total deferred tax assets and liabilities	103,861	96,506
Valuation allowance	(103,861)	(96,506)
Net deferred tax asset	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Net change in valuation allowance	$ 7,400,000
Net operating losses available to offset future state taxable income expiration description	between 2024 and 2043
Unrecognized tax benefits	$ 0	$ 0	$ 0
Interest and penalties related to unrecognized tax benefits	0	0	0
Expected amount of unrecognized tax benefits	0	$ 0	$ 0
Capitalized R&D costs	$ 31,600,000
U.S. [Member]
Income Taxes [Line Items]
Capitalized research and development costs amortization period	5 years
Non-US [Member]
Income Taxes [Line Items]
Capitalized research and development costs amortization period	15 years
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 358,900,000
Expiration of federal net operating loss carryforwards	$ 194,600,000
Net operating loss carryforwards expiration date	Dec. 31, 2037
Federal [Member] | Unlimited Carryforward [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 164,300,000
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 198,600,000

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023 Segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Information - Summary o

Segment Information - Summary of Revenue and Segment Operating Profit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenue	$ 238,718	$ 180,364	$ 121,622
Segment Operating Profit (Loss)	56,921	4,976	9,937
Corporate expenses	106,124	84,221	50,536
Operating loss	(49,203)	(79,245)	(40,599)
Other expense, net	3,392	(3,493)	3,505
Net loss	(45,811)	(82,738)	(37,094)
Depreciation expense	15,318	9,222	9,440
Total assets	703,048	643,416
Construction in Progress [Member]
Segment Reporting Information [Line Items]
Total assets	314,678	209,050
All Other Corporate Assets [Member]
Segment Reporting Information [Line Items]
Total assets	176,637	300,631
Operating Segment
Segment Reporting Information [Line Items]
Depreciation expense	15,318	9,222	9,440
Total assets	211,733	133,735
Operating Segment | Energy Industrial [Member]
Segment Reporting Information [Line Items]
Revenue	128,639	124,807	114,958
Segment Operating Profit (Loss)	34,162	18,844	14,486
Depreciation expense	10,720	8,476	9,440
Total assets	93,168	94,415
Operating Segment | Thermal Barrier [Member]
Segment Reporting Information [Line Items]
Revenue	110,079	55,557	6,664
Segment Operating Profit (Loss)	22,759	(13,868)	$ (4,549)
Depreciation expense	4,598	746
Total assets	$ 118,565	$ 39,320

Segment Information - Schedule

Segment Information - Schedule of Revenues, Based on Shipment Destination or Research Services Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenue	$ 238,718	$ 180,364	$ 121,622
U.S. [Member]
Segment Reporting Information [Line Items]
Revenue	151,037	113,968	66,837
International [Member]
Segment Reporting Information [Line Items]
Revenue	$ 87,681	$ 66,396	$ 54,785

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] - USD ($)		1 Months Ended
	Mar. 06, 2024	Jan. 31, 2024
Subsequent Event [Line Items]
Sale and leaseback arrangement date		January 2024
Sale and leaseback equipment value		$ 5,000,000
Sale and leaseback rent payment term		3 years
Acceleration of unamortized stock-based compensation charges	$ 2,200,000
Minimum [Member]
Subsequent Event [Line Items]
Potential impact of reimbursement from customer		$ 0
Maximum [Member]
Subsequent Event [Line Items]
Potential impact of reimbursement from customer		$ 10,000,000

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts (Detail) - Allowances for Uncollectible Accounts and Sales Returns and Allowances [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 255	$ 150	$ 442
Charges to Costs and Expenses	(93)	115	(84)
Recoveries of Costs and Expenses	0	0	(208)
Deductions to Allowances for Uncollectible Accounts	0	0	0
Charges to (Deductions from) Other Accounts	68	(10)	0
Balance at End of Year	$ 230	$ 255	$ 150