Tesla CEO Elon Musk announced that Starship prototype SN4 passed the cryogenic proof test at SpaceX’s launch site in Boca Chica, Texas. The SpaceX founder tweeted a video on April 27 saying it was snowing in Texas and in a subsequent tweet Musk said that SN4, SpaceX’s full-scale Starship prototype, has passed the cryogenic proof test.
The cryogenic proof test is one of the first tests including an ambient pressure test to prove the Starship’s flight worthiness. The prototype had already passed the ambient pressure test before heading to the cryogenic proof test and will now prepare for static fire and then potentially a hop to 150 metres.
SN4 has become SpaceX’s first full-scale prototype to pass such test after the Mk1, SN1, and SN3 full-scale Starship prototype failed at it. While SN2 had passed the cryogenic proof test, was only a partially assembled tank section rather than a full-scale Starship prototype. It passed the test by hitting 4.9 bar which the SpaceX founder admitted in a tweet that though it was “enough to fly”, it was “kind of a softball”.
4.9 bar. Kind of a softball tbh, but that’s enough to fly!— Elon Musk (@elonmusk) April 27, 2020
While the test plans for SN4 are constantly evolving, SpaceX is planning to hop the prototype to around 150 metres which was earlier planned for SN3. According to Tesla CEO, it will be limited to only small hops which do not require the relight of raptor engines and the flaps will be used in SN5 or SN6.
SN4 won’t get flaps, so can only do flights with engine on. Just did a reset this week on flap, actuator & static aero design. Either SN5 or SN6 will get flaps.— Elon Musk (@elonmusk) April 16, 2020