United States securities and exchange commission logo





                          September 15, 2021

       John F. Fairbank
       Chief Financial Officer
       Aspen Aerogels Inc.
       30 Forbes Road, Building B
       Northborough, Massachusetts 01532

                                                        Re: Aspen Aerogels Inc
                                                            Registration
Statement on Form S-3
                                                            Filed September 10,
2021
                                                            File No. 333-259449

       Dear Mr. Fairbank:

              This is to advise you that we have not reviewed and will not
review your registration
       statement.

               Please refer to Rules 460 and 461 regarding requests for
acceleration. We remind you
       that the company and its management are responsible for the accuracy and
adequacy of their
       disclosures, notwithstanding any review, comments, action or absence of
action by the staff.

                                                        Please contact
Jacqueline Kaufman at 202-551-3797 with any questions.




                          Sincerely,


                          Division of Corporation Finance

                          Office of Trade & Services