SpaceX fires up Starship and Super Heavy booster hours apart – Teslarati

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SpaceX appears to have successfully fired a Starship and Super Heavy booster hours apart, testing a total of three new Raptor 2 engines on the two rockets.

SpaceX says it completed a twin-engine static fire with Starship 24 less than three hours after the company first successfully fired a Raptor 2 engine installed on a rocket prototype. That earlier test, conducted by Super Heavy Booster 7, was also the first time SpaceX used its new Starbase orbital launch site to support a static fire test and the second ever static fire of a Starship booster prototype. If the company had called it quits after Booster 7 survived its first deliberate trial by fire, it would have been another exceptionally successful day.

But SpaceX wasn’t done.

Instead, after Booster 7’s seemingly flawless single-Raptor static fire at 5:25 pm CDT, SpaceX loaded Starship 24 with a small amount of liquid oxygen and methane propellant and ignited two of the ship’s six engines at 8:18 pm. It was initially unclear how many engines were involved, but a tweet from SpaceX later confirmed that there were two. More likely than not, one of those engines was a sea level-optimized Raptor with a smaller bell nozzle and the other was a vacuum-optimized Raptor with a much larger nozzle.

Almost ten months ago, Starship 20 – SpaceX’s first potentially orbital-class Starship prototype – began static fire testing in a somewhat similar fashion. The first day of static fires began with a single Raptor Vacuum engine and ended with a simultaneous RVac and Raptor test at sea level in October 2021. In some ways, SpaceX has been a little less cautious with Starship 24, which is the second potential orbital class prototype to begin proof testing. Ship 24 already had all six Raptors installed, while Ship 20 only had four of six engines installed first static fire tests. SpaceX also took about three weeks to progress from Ship 20’s first static fire test to its first static fire of all six engines, while it appears Ship 24 could attempt its first six-engine test just a few days to a week later .

On the other hand, Ship 24’s path to its first static fire was substantially longer than Ship 20’s. Ship 20 completed its first static fire test(s) just 25 days after its first proof test, referring to the process of verifying that the prototype was in good working order before moving on to riskier tests with flammable propellants and intentional ignitions. Ship 20 also completed its first six-engine static fire 46 days after testing began. Ship 24, meanwhile, took 75 days to go from its first proof test to its first static fire—almost three times slower than Ship 20, a prototype that was essentially the first of its kind.

It is possible that Ship 24’s upgraded Raptor 2 engines are partially or fully to blame. Instead of jumping right into ‘hot’ Raptor testing like Ship 20, which began that particular campaign with a partial ignition preburner test, SpaceX Ship 24 continued seven ‘spin-prime’ tests before its first static fire. For Raptor, spin primes test the ignition step for preburner ignition, which is itself a step for ignition of the main combustion chamber (where the engine begins to produce meaningful power). Raptor launch procedures likely involve flowing gaseous helium, nitrogen, or propellant (oxygen/methane) through the engine to turn on its turbopumps, ‘priming’ them for ignition of the preburner and main combustion chamber.

On Raptor 1, the preburners would once reach a high enough flow rate, producing hot gas that would mix the main combustion chamber one last time and ignite to start the engine. In a recent interview with Tim Dodd (“The Everyday Astronaut”), CEO Elon Musk revealed that SpaceX was able to “remove flare igniters” from Raptor 2’s main combustion chamber (MCC). It is unclear if that means that Raptor 2 has now zero MCC igniters, but a big change in the overall ignition process could explain why the start of Ship 24 and Booster 7 engine testing was so slow. So could the accidental explosion Booster 7 caused when SpaceX attempted to spin-prime all 33 of its Raptor 2 engines simultaneously.

Anyway, SpaceX has finally crossed that certain Rubicon and, with luck, Raptor 2 testing will begin to accelerate on both Starship 24 and Super Heavy Booster 7. SpaceX has test windows scheduled for August 11th, 15th, and 16th. A warning distributed to Boca Chica, Texas residents on August 10. confirmed that the company intends to carry out at least one more static fire test on the 11th.

SpaceX fires up Starship and Super Heavy booster hours apart

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