Don’t be misled, this test was a massive success. SpaceX only estimated a 60% chance of landing- and SN10 managed to land. This was a prototype vehicle, so with SpaceX’s rapid development explosions are rather expected, but before we go into that- let’s rewind the clock.
On Wednesday, March 3rd SpaceX prepared for the launch of their prototype Mars rocket; Starship SN10. After addressing an issue with a stuck liquid oxygen vent valve in the ground service equipment, they worked towards a liftoff time of 2:14pm CT. As they reached T-0 the three raptor engines ignited – but quickly shut down. The auto-abort, Elon said on twitter, was the result of a “Slightly conservative thrust limit.” SpaceX decided to move forward with another launch attempt with increased limits on the thrust and propellant cycle.
SpaceX moved to target 5:15pm CT, and went live just a few minutes before liftoff. When they reached T-0, the prototype vehicle ignited all three engines and lifted off the pad. At T+2 minutes and 15 seconds, SpaceX executed the planned shutdown of the first Raptor engine. SN10’s flight continued successfully for another minute before reaching the second planned engine shutdown. Upon reaching its apogee of 10KM, SN10 hovered with one engine until T+4:20 (nice one Elon) when it began the bellyflop maneuver. The raptor engine gimbaled to an extreme to transition SN10 to a horizontal position, then Starship descended under the control of its flaps until reaching about 500 meters in altitude.
Both SN8 and SN9 had reached this point in flight, but this is where the major differences between SN10 and the previous vehicles begin to show. During previous attempts SpaceX ignited two of the Raptor engines in order to reorient vertically for landing. Neither of the previous two rockets were able to properly reorient and stick the landing. As Elon said previously on twitter, only two of the raptor engines are actually required for landing, but this time, SpaceX decided to ignite all three raptor engines and measure engine health to determine which of the engines should stay lit for landing, and which should be shut down.
This change in landing procedure served SpaceX well. As SN10 reached the planned altitude, all three raptor engines ignited sequentially, then gimbaled to move the vehicle vertical. The engines are ignited sequentially rather than simultaneously as the engines must be ignited at a higher thrust level (and thus fuel draw) before they can throttle back. The sequential ignition allows them to avoid causing a drop in fuel pressure which could lead to an engine malfunction. Once SN10 was vertical, at T+6 minutes and 7 seconds, the first raptor engine was shut down- followed shortly by a second.
SN10 continued to descend, now seemingly sporting a small methane leak, as there was fire along the lower side of the vehicle. Despite these flames, SN10 continued its controlled descent and made a smooth landing relatively centered on the landing pad. The last of the flames disappeared as the fire suppression system sprayed water at the base of the rocket. The last of the dust cleared, as SpaceX’s stream ended; just 2 minutes and 30 seconds after SN10’s successful landing. That may seem like the end of the story, with people hoping for a second flight of SN10, but those watching other streams, like that of Everyday Astronaut, got that flight a little sooner than they hoped for.
At T+14m34s SN10 erupted into ball of flames. The explosion, emanating from the base of the rocket, threw the vehicle high into the air.
In addition to the livestreams of the explosion, we were treated to an excellent video shortly after by Trevor Mahlmann. The explosion is at 3:38.
While SpaceX will certainly be investigating the exact cause of the explosion, no exact reasoning has been provided so far, failure is to be expected with prototype vehicles like Starship; and this test was no failure. SpaceX has now proved the feasibility of the Bellyflop maneuver- which limits the speed of the vehicle on reentry without burning precious fuel. The amount of fuel needed to recover a second stage impacts the total payload of a rocket far more than the first stage does- so every kilogram matters. This is also why delaying the reignition of engines for as long as possible is essential. Any extra time the vehicle is kept hovering is just burning fuel. While any chance of SN10 flying again is gone, SpaceX is hard at work with many more prototype Starship vehicles in various stages of production, including prototypes of the SuperHeavy Boosters; BN1 and BN2. This will be a major year for SpaceX; they are aiming for orbital flights of Starship later this year. This test certainly provided them with a great deal of valuable data which will be used as they continue to rapidly develop and improve Starship which will one day take us to Mars.
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