Hours after a successful Falcon 9 launch, a SpaceX Starship prototype has kicked off a challenging gauntlet of tests for the fifth time in hopes of becoming the first to take flight.
Five days after the ~30m (~100 ft) tall steel rocket was transported from the factory to the launch pad, SpaceX has fully integrated it with a brand new launch mount – built from scratch after operator error caused Starship SN4 to explode and destroy the prior mount. Assembled and outfitted with great haste, the new mount was completed just a day or two before Starship SN5 was moved to the pad and installed on top of it.
Triggered by a quick disconnect umbilical panel fuel leak that effectively caused a bomb-like fuel-air explosion, Starship SN4’s May 29th demise occurred shortly after a Raptor static fire test that was likely one of the last hurdles standing between SpaceX and the first full-scale Starship flight test. That fated static fire itself occurred a single day after SpaceX crossed a major regulatory milestone with an official FAA launch license for an effectively unlimited number of suborbital Starship flights. Now transformed into a pile of scorched scrap metal, Starship SN4 has passed the torch to Starship SN5.
Effectively identical to the gauntlet of tests Starship SN4 completed in the weeks prior to its destruction, Starship SN5 has kicked off its own test campaign with an ambient pressure test – a low-risk method of checking a pressure vessel for leaks. Starship SN5 apparently passed that first test without issue and SpaceX is now in the midst of loading the rocket tank section with cryogenic liquid nitrogen as a chemically neutral and nonexplosive stand-in for live liquid oxygen and methane propellant. (SN4 serves as a perfect illustration of why initial cryo proof tests are performed with LN2 instead of real propellant.)
SN4 was actually the first full-scale Starship prototype to survive a full cryogenic proof test, achieving 7.5 bar (~110 psi), so SN5’s success is far from guaranteed. Still, given SpaceX’s iterative, clockwork-like approach to development means that it’s far more likely than not that Starship SN5 will pass all the tests that its predecessor did – and then some.
If Starship SN5’s cryo proof is successful, SpaceX has a few options available. Depending on the level of confidence in SN5, SpaceX could proceed directly into installing a single Raptor engine on the rocket’s triple-engine thrust structure and move on to wet dress rehearsals (WDRs) with methane and oxygen propellant. If a more cautious approach is preferred, SpaceX could perform a WDR or two before installing a Raptor engine. Either way, once the WDR phase is complete, Starship SN5 can begin live Raptor engine testing, starting with turbopump prime and preburner tests and culminating in one or several static fires.
Finally, once preburner and static fires have been completed without issue, SpaceX can begin to seriously prepare SN5 for its inaugural hop test, likely targeting an altitude of ~150m (~500 ft) before landing a few hundred feet from the launch mount. For now, many steps remain in the interim before Starship SN5 is even close to a hop test, but it shouldn’t take long to find out how long we’ll have to wait.