For the second time in five weeks, SpaceX has cycled its first orbital-grade Super Heavy booster from the Starship factory to the launch pad ahead of a challenging and multifaceted test campaign.
The 69-meter (225 ft) Deemed Super Heavy Booster 4, or B4, rocket was first launched to the launch pad around August 3 after being fitted by SpaceX technicians. 29 Raptor engines in one night. Following a prototype of the orbiter-class S20 spacecraft a few days later, two spacecraft stages were stacked to their full height on August 6, creating the largest rocket ever assembled. The 20th was quickly returned to the construction site, with SpaceX workers completing about 10 additional days of finishing touches—mainly focused on avionics connections and secondary plumbing.
A week later, Booster 4 followed the 20 ship back to ‘high bay’ at Starbase, where the teams eventually removed all 29 Raptor engines and spent the next four weeks or so doing similar final integration work. Now, after installing what looks like hundreds of feet of wire, dozens of additional gas and fluid lines, compressed gas tanks, and hydraulic sleds, SpaceX’s first airworthy Super Heavy, are back at the launch site.
A little less than two weeks ago, SpaceX again 29 Raptors installed on Booster 4. This time around, though, all of these engines are believed to be ready for flight — or at least, static fire testing — after qualification testing is completed at SpaceX’s development facilities in Central Texas. Interestingly, each of the Super Heavy’s 20 outer ring engines from the Raptor Boost is also expected to have its own small umbilical slab that will attach to the orbital launch platform’s ground systems.
When Booster 4 was installed on the all-new orbital launch pad, most of the engine’s individual connectors had yet to be installed, and it’s unclear whether SpaceX will actually be able to test the complex mechanisms before the Super Heavy returns to the construction site. This time, all 20 secret engines have been installed on the launch pad, and it is safe to assume that these mechanisms will be extensively tested in the coming weeks.
This test will be part of a more involved testing campaign. Specifically, if SpaceX intends to test the Super Heavy Booster 4 at the orbital launch site, any booster testing will simultaneously require the neutralization of the comprehensive tank farm designed specifically for the orbital plate and a wide range of other ground infrastructure that simply did not exist at the beginning of 2021. Qualifying the Booster 4 was no less difficult, as the Super Heavy was never fully tested. Now in the midst of destruction at SpaceX’s suborbital test facilities, Super Heavy Booster 3 I did He completed a partial proof-of-cold test with three Raptor engines, but SpaceX has never filled an extremely heavy engine with more than 3,000 tons (~6.6 million pounds) of fuel and has never fired more than three Raptor engines simultaneously.
Perhaps the most mysterious part of the Super Heavy Booster 4 qualification is its consistent test-fire campaign. Despite SpaceX getting there, the final challenge will likely be to ignite all 29 of the B4 Raptor’s engines — which are likely to produce up to 5,400 tons (11.9 million pounds) of thrust, making the Super Heavy the most powerful rocket ever tested. Absolutely.
At the same time, SpaceX also started Raptors reinstalled on ship 20 – Currently installed in Suborbital Pad B – Before the first Starship Proof test(s) and steady fire. Stay tuned for updates on SpaceX’s plans to test the first orbital-class vehicle and Super Heavy booster.