SpaceX Super Heavy Booster Prototype Undergoes A Cryogenic Proof Test

Evelyn Arevalo by Evelyn Arevalo July 13, 2021

SpaceX Super Heavy Booster Prototype Undergoes A Cryogenic Proof Test

 Featured Image Source: LabPadre via YouTube/Twitter 

SpaceX initiated the development of Starship’s Super Heavy rocket that will propel it to orbit. The first full-scale prototype called ‘Booster 3’, was transported to the launch pad where it will undergo a series of ground tests. On Thursday, July 8, Booster 3 underwent a proof test at ambient temperature. This test is typically preformed ahead of a cryogenic proof test meant to assess the stainless-steel vehicle’s structural integrity. It was the first time SpaceX has preformed a ground test on a Super Heavy prototype. This past week, heavy thunderstorms and high winds rolled into South Texas, causing SpaceX to delay major tests for a couple of days. Live cameras at Boca Chica captured incredible footage of Booster 3 struck by lightning last Wednesday, shown below. 

After weather cleared up a bit, engineers transported a Raptor engine labeled ‘57' to the launch pad on Sunday, July 11, and installed it. All engines have a production number to identify them. SpaceX founder Chief Engineer Elon Musk shared yesterday that they made a “Final decision… earlier this week on booster engine count. Will be 33 at ~230 (half million lbs) sea-level thrust,” Musk said via Twitter. The final version of the Super Heavy booster will have 33 powerful methane fueled engines, however, the prototypes will initiate testing with 29 then scale up. Starship, the spacecraft, will feature a trio of sea-level engines and three vacuum-optimized Raptors (R-Vac), especially designed for propulsion in space. Super Heavy will not require R-Vac engines because it will return to Earth soon after launching Starship to orbit. Using Super Heavy to blast off Starship to space enables the vehicle to carry over 100 tons of cargo and conserve fuel. Engineers aim to develop a fully-reusable booster capable of conducting at least three flights per day.


Weather improved in South Texas by Monday, July 12; engineers proceeded to perform a cryogenic proof test on Booster 3. This test is important because it serves to determine how strong the vehicle is. During the test, the 230-foot-tall stainless-steel vehicle was pressurized with cryogenic liquid nitrogen, that has a freezing temperature of approximately −320 °F (−196 °C), to simulate the pressure and temperature its propellant tanks will experience in-flight when its propellant tanks are loaded with ultra-cold methalox [methane and liquid oxygen] fuel and its powerful engines are ignited. Super Heavy will produce more than twice the thrust of the Saturn V rocket that launched NASA astronauts to the moon during the Apollo missions.

Now that Booster 3 has its first engine installed, we can expect to see a static-fire test of the Raptor engine soon. It is unknown how many Raptors will SpaceX install given that these tests can be risky, based on previous Starship test ignitions of early prototypes that exploded. It is unclear how many Raptors SpaceX would be willing to risk on Booster 3. During a static-fire test, vehicle’s propellant tanks will be filled with liquid methane and oxygen to ignite the powerful Raptor for a few seconds as the gigantic booster remains grounded to the test stand. Musk said that Booster 3 will only undergo ground testing –not fly, so it is likely that this booster will be pushed enough to see if it has any structural flaws. Musk shared that the first to fly will be Booster 4, “Booster 3 will be used for ground tests. We’re changing much of design from 3 to 4,” he said, “Booster 3 was very hard to build. Expect especially rapid evolution in first ~10 boosters & first ~30 ships.” To support Starship flights, SpaceX is building the launch tower that will support orbital missions, pictured below. The first orbital flight attempt could occur as soon as this Summer. The company plans a bold debut flight, the Starship launch vehicle will lift off from South Texas to orbit around Earth and land off the coast of Kauai, Hawaii! 

 Image Source: Elon Musk 


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