It has been a long time since we’ve seen engines test-fired in Starbase, but Thursday afternoon, SpaceX did not just one but two. These tests mark a significant milestone for Vacuum Raptor development.
First Vacuum engine static fire while installed on a Starship
Starship 20 has been standing on Pad A for several weeks now, conducting several tests with different systems. Most notably have been tests on its RCS thrusters which knocked off some thermal protection tiles. Thursday night brought the return of Raptor static fires to Boca Chica with not one but two static fires from Starship 20.
This test marks the first static fire SpaceX conducted of a Raptor engine since Superheavy Booster 3 static fired a Raptor back on July 20. Static fire number one was the first time SpaceX test-fired the vacuum-optimized Raptor engine while being integrated on a Starship vehicle.
Surprise dual engine static fire
About 30 minutes after the first static fire, SpaceX conducted a second static fire using two Raptors installed on Starship 20. Video captured by LabPadre shows an aborted static firing several minutes before this second firing. The footage shows liquid oxygen flowing from two different engines, which means that SpaceX attempted to start two Raptors. While this is not the first time SpaceX has conducted a multi-engine static fire, this is the first one to include a Vacuum Raptor.
This is not the first Vacuum Raptor engine we have seen from SpaceX. A few vacuum engines have made their way to Starbase for testing and possibly flights. However, this Raptor vacuum is the first we’ve seen test-fired outside SpaceX’s test facility in McGregor, Texas.
Every Raptor produced has been test-fired there, except for a few used during Booster 4 testing, but we expect those to return for testing. Vacuum Raptors are no exception, as we have seen several installed on test stands at McGregor. We got our first look at how much larger the vacuum version of the engine was just over a year ago when the first one rolled off the production line. Since then, McGregor residents have heard their test fires, and then three were installed when Starship 20 was hoisted on top of Booster 4 back in August.
What’s the difference between the normal Raptor and Vacuum Raptor?
The vacuum-optimized Raptor engine is designed for use outside the atmosphere. It sports a much larger nozzle and several other changes that SpaceX would like to keep close to its chest. These improvements make the engine must more efficient while operating in a thinner atmosphere and, well, the vacuum of space.
You see vacuum rocket engines on all multi-stage rockets, as it makes sense to install a more efficient engine once staging takes place higher in the atmosphere. Starship will differ slightly – since it still needs sea-level optimized engines for landings – but it will sport three vacuum Raptors.
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