On Wednesday, March 3, SpaceX’s Starship SN10 vehicle took to the air from Boca Chica, Texas in a (successful) 10-kilometer test flight. The vehicle was scheduled to perform its hop earlier in the day, at 20:15 UTC, but that attempt was aborted at engine ignition. Speaking on Twitter after the abort, SpaceX CEO Elon Musk stated that the launch abort was because of a “slightly conservative high thrust limit” on the vehicle’s Raptor engines. SpaceX engineers changed the limit and fueled the vehicle for a second attempt about two hours later. The SpaceX webcast went live ten minutes before launch, with famed “norminal” SpaceX engineer John Insprucker as host.

Finally, at 23:14 UTC, SN10 ignited its three Raptor engines and took to the air, taking four minutes to reach its planned apogee. Along the way, two Raptor engines were shut down to reduce flight loads. At this early phase in testing, and with people’s houses less than three kilometers from the pad, the flights are limited to subsonic velocity. These shutdowns were punctuated by brief gushes of flame as unburnt propellant hit the hot metal of the engines, but this was expected.

At apogee, the craft hung in the air on the blue mach diamond thrust of the single Raptor engine, until that engine was shut down to begin the descent. As it began the transition to horizontal flight, the vehicle dumped excess liquid oxygen in a dramatic but planned cloud of gas.

As it descended, the vehicle controlled its attitude with the fore and aft flaps. Everything appeared to go “norminally” — a SpaceX term originating from a misspeak during a webcast — during this portion of the flight. Once it was under two kilometers in altitude, the vehicle prepared to perform its flip and landing maneuver.

At about 500 meters altitude, the vehicle relit all three of its engines, a change from the previous flight profile. All engines successfully ignited, and the leeward engine immediately shut off after the flip. This engine has the least leverage in the gimbal to flip the vehicle vertically and is only used if one of the other engines fails to ignite, which has happened before on the flights of SN8 and SN9.

After transitioning from being on its side back to being vertical for landing, it shut off the other engine and did the final landing burn with one engine. This allowed for the best control of the vehicle’s descent without having to resort to deep throttling, which complicates engine design. Unlike the Falcon 9, Starship incorporates a low thrust-to-weight ratio portion in its landing burn and one engine allows this.

It touched down harder than planned and at a slight angle, but it was still standing on the landing pad when the dust cleared. This was the first full Starship test vehicle to land successfully, after the flights of SN8 and SN9 which both exploded upon landing.

Amateur post-landing analysis of footage showed that two of the six landing legs did not latch, which would explain why SN10 was leaning just a bit after touchdown. Several days later, this was confirmed by a tweet from Elon Musk, who went on to explain the hard landing happened because the “SN10 engine was low on thrust due (probably) to partial helium ingestion from [the] fuel header tank. Impact of 10 [meters per second] crushed legs & part of skirt”, which led to an explosion eight minutes after landing.

More Information

Launch video (LabPadre)