Video: J-2X Powerpack Test By Staff Writers on February 20, 2012 in Media, Video NASA’s J-2X testing picks up this year with assessment of the powerpack. On February 15, a 1.86 second burst of flames marked a successful test at Stennis Space Center, bringing the upper stage of NASA’s Space Launch System closer to reality. Staff WritersMore Posts Leave a Reply Cancel reply Your email address will not be published. Required fields are marked * Name * Email * Website Comment Type the RED Moving Letters View Help Information Moving Letters: Notify me of follow-up comments by email. Notify me of new posts by email.