Filed Pursuant to Rule 424(b)(5)
Registration Number 333-263622


The information in this preliminary prospectus supplement is not
complete and may be changed. A registration statement relating to these securities has become effective by rule of the Securities and Exchange Commission. This preliminary prospectus supplement and the accompanying prospectus are not an offer to
sell these securities, and we are not soliciting offers to buy these securities, in any jurisdiction where the offer or sale is not permitted.




(To Prospectus dated
March 16, 2022)

$150 million


% Convertible Senior Notes due 2027



We are offering $150 million principal amount of our
                % Convertible Senior Notes due 2027 (the “notes”). The notes will bear interest at a rate of
                % per year, payable semiannually in arrears on January 1 and July 1 of each year, beginning on January 1, 2023. The notes will mature on
July 1, 2027, unless earlier redeemed, repurchased or converted.

Holders may convert their notes at their option at any time prior to
the close of business on the second scheduled trading day immediately preceding the maturity date. Holders who convert on or prior to January 1, 2025 (other than a conversion in connection with a make-whole fundamental change in which the conversion
rate is adjusted) shall be entitled to receive an interest make-whole payment payable in cash, as described in this prospectus supplement. Upon conversion of notes, we will deliver cash, shares of our common stock or a combination of cash and shares
of our common stock, at our election, as described in this prospectus supplement.

The conversion rate with respect to the notes will
initially be                  shares of common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately
$                 per share of common stock). The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid

We may not redeem the notes prior to July 6, 2025. On or after July 6, 2025, we may redeem for cash all or any portion
(subject to the partial redemption limitation described herein) of the notes if the last reported sale price of our common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive)
during any 30 consecutive trading day period ending on the trading day prior to the date on which we provide notice of the redemption. The redemption price will be the principal amount of the notes to be redeemed, plus accrued and unpaid interest
to, but excluding, the redemption date.

If we undergo a fundamental change (as defined below), subject to certain conditions, holders may
require us to repurchase for cash all or part of their notes at a purchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but not including, the fundamental change repurchase date.

The notes will be our senior unsecured obligations and will rank senior in right of payment to any of our future indebtedness that is
expressly subordinated in right of payment to the notes, will rank equally in right of payment with all of our existing and future liabilities that are not so subordinated (including our existing Convertible Senior PIK Toggle Notes due 2027), will
be effectively junior to any of our secured indebtedness to the extent of the value of the assets securing such indebtedness (including any borrowings outstanding under our revolving line of credit) and will be structurally subordinated to all
indebtedness and other liabilities (including trade payables) of our subsidiaries.

We do not intend to apply to list the notes on any
securities exchange or any automated dealer quotation system. Our common stock is listed on the New York Stock Exchange (“NYSE”) under the symbol “ASPN”. The last reported sale price of our common stock on the NYSE on
June 28, 2022 was $14.71 per share.

Investing in our notes involves a high degree of risk. You should carefully consider the risks
described under the heading “Risk Factors” beginning on page S-14 of this prospectus supplement before buying our notes.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or
determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.


     Per Note      Total  

Public offering price(1)

   $        $    

Underwriting discounts and

   $        $    







Proceeds, before expenses, to us

   $                    $                









Plus accrued interest, if any from July     , 2022.


We have agreed to reimburse the underwriters for certain expenses in connection with this offering. See

The underwriters also may purchase up to an additional $22.5 million principal amount of
notes, solely to cover over-allotments, at the public offering price, less the underwriting discounts and commissions payable by us, within 30 days from the date of this prospectus supplement.

Concurrently with this offering, we are offering, through a separate prospectus supplement, $225 million of shares of our common stock,
plus up to an additional $33.75 million of shares of common stock that the underwriters of the concurrent common stock offering have the option to purchase from us, solely to cover over-allotments. Our existing stockholder Wood River Capital,
LLC, an affiliate of Koch Strategic Platforms, LLC, and/or certain of its affiliates have indicated an interest in purchasing up to $100 million of our common stock in the concurrent common stock offering at the public offering
price. However, because indications of interest are not binding agreements or commitments to purchase, Wood River Capital, LLC and/or certain of its affiliates may determine to purchase fewer securities than they indicate an interest in
purchasing or not to purchase any securities in the concurrent common stock offering. See “Concurrent Common Stock Offering”. The completion of this offering is not contingent on the completion of the concurrent common stock offering, and
the completion of the concurrent common stock offering is not contingent on the completion of this offering. Accordingly, you should not assume that the concurrent common stock offering will be consummated on the terms described in this prospectus
supplement, or at all. This prospectus supplement does not constitute an offer to sell, or the solicitation of an offer to buy, any securities being offered in the concurrent common stock offering.

The underwriters are offering the notes as set forth under “Underwriting”. We expect that delivery of the notes will be made to
investors in book-entry form through The Depository Trust Company on or about                , 2022.



Joint Book-running Managers



   Jefferies    BofA Securities

Green Structuring Agent



Supplement dated                 , 2022

About the Author: AKDSEO

You May Also Like