
Starship about to be stacked on Superheavy, using
the launch tower’s chopstick arms. Click for full image.
For the first time in six months SpaceX engineers have stacked Starship prototype #24 on top of Superheavy prototype #7, with the intention of running a dress rehearsal countdown and a full static fire test of Superheavy’s 33 engines, all in preparation for the first orbital test flight before the end of this year.
According to CEO Elon Musk, Booster 7 and Ship 24 will attempt Starship’s first full-stack wet dress rehearsal (WDR) once all is in order. The prototypes will be simultaneously loaded with around 5000 tons (~11M lb) of liquid oxygen and methane propellant and then run through a launch countdown. Diverging just before ignition and liftoff, a WDR is meant to be more or less identical to a launch attempt.
…If the wet dress rehearsal goes to plan, SpaceX will then attempt to simultaneously ignite all 33 of the Raptor engines installed on Super Heavy B7, almost certainly making it the most powerful liquid rocket ever tested. Even if all 33 engines never reach more than 60% of their maximum thrust of 230 tons (~510,000 lbf), they will likely break the Soviet N-1 rocket’s record of 4500 tons of thrust (~10M lbf) at sea level. It would also be the most rocket engines ever simultaneously ignited on one vehicle. SpaceX will be pushing the envelope by several measures, and success is far from guaranteed.
Depending on the results of these tests, the stacked rocket will either require further modifications, or could even proceed directly to launch.
We are thus seeing a true race between SpaceX’s privately developed and funded rocket and NASA’s government developed and funded SLS rocket. Which will launch first? Right now the race is neck-and-neck, though that is deceiving since SpaceX began development twelve years after NASA started work on SLS. Even if SLS launches first, SpaceX will have clearly shown that private enterprise does things faster (7 years vs 18 years) and for far less money (about $9 billion vs $46 billion).