Was curious about your mention of Stennis, so I looked it up: https://en.wikipedia.org/wiki/John_C._Stennis_Space_Center#E2_Test_stand https://en.wikipedia.org

Was curious about your mention of Stennis, so I looked it up: https://en.wikipedia.org/wiki/John_C._Stennis_Space_Center#E2_Test_stand https://en.wikipedia.org/wiki/John_C._Stennis_Space_Center#E... Sounds like SpaceX has, with NASA and the State of Mississippi modified the test stand to support methane.