SpaceX is ready to conduct another round of Starship SN7 tests

Image Source: @austinbarnard45 via Twitter

SpaceX is in the process of developing Starship, a stainless-steel spacecraft that will one day take humanity back to the moon and enable life on Mars. The aerospace company is working on a very tight schedule. SpaceX’s first private-customer, Japanese entrepreneur Yusaku Maezawa, booked a journey around the moon aboard Starship by 2023. And NASA selected SpaceX to develop a lunar optimized Starship lander under the Artemis program which aims to take the first woman and next man to the moon in 2024. SpaceX only has a couple of years to develop a space-ready Starship. We are already in mid-2020, time sure goes by fast but SpaceX teams are assembling Starship test vehicles faster. A production factory of Starship prototypes are under construction at the company’s South Texas facility located in a small village at Boca Chica Beach, Brownsville, TX.

The founder and Chief Engineer at SpaceX Elon Musk says – “A high production rate solves many ills. If you have a high production rate, you have a high iteration rate. For pretty much any technology whatsoever, the progress is a function of how many iterations do you have, and how much progress do you make between each iteration. If you have a high production rate then you have many iterations. You can make progress from one to the next.”

SpaceX is building many prototypes this year, each featuring minor changes to test out. The prototypes are referred to by serial number (SN). The company already tested four vehicles which were destroyed during tests. Starship SN5 and SN6 are simultaneously under construction inside a vehicle assembly building at Boca Chica. Destructive tests are expected, Starship is still in its initial phase of development. Engineers are currently preparing to test a Starship dome tank referred to as SN7. This tank features a variety of stainless steel alloys, it was manufactured to determine if 301 or 304L (or a custom) stainless-steel mix would be stronger for future vehicles. In March, Musk shared some Starship parts “will use 304L, as it has higher toughness” at cryogenic temperatures and that SpaceX will experiment with “internally developed” stainless-steel alloy mix by the end of this year.

Some parts will use 304L, as it has higher toughness at cryo temps. Will move to internally developed alloys probably end of year.

— Elon Musk (@elonmusk) March 14, 2020

The SN7 dome tank was tested last week on June 15^th, it underwent a cryogenic pressurization test in which the stainless-steel vehicle is filled up with ultra-chilled liquid nitrogen to test if the structure can withstand pressures it would experience during flight. Starship must withstand a pressure in between ~6 and ~8.5 bar strength; A ~6 bar is needed for orbital flight and ~8.5 bar is needed for crewed flights. If a prototype passes the cryogenic pressure test, the next phase is a static firing of a Raptor engine.

Tank didn’t burst, but leaked at 7.6 bar. This is a good result & supports idea of 304L stainless being better than 301. We’re developing our own alloy to take this even further. Leak before burst is highly desirable.

— Elon Musk (@elonmusk) June 15, 2020

Last week’s SN7 test was pressurized to a 7.6 bar – “Tank didn’t burst, but leaked at 7.6 bar. This is a good result & supports idea of 304L stainless being better than 301. We’re developing our own alloy to take this even further. Leak before burst is highly desirable,” Musk explained on June 15. “…There a few known weak points on this test tank, probably capable of more pressure.”

“The second test tank to follow shortly has addressed the weak points,” he added.

The SN7 test tank has been repaired with 304L stainless steel, and will undergo another cryogenic pressure test this week. According to the city’s website, a road closure at Boca Chica Beach indicates SpaceX could conduct some vital work on Tuesday, June 23 from 8:00 a.m to 5:00 p.m CDT. A Boca Chica SpaceX enthusiast shared a photograph of the Starship SN7 dome tank repaired via Twitter, to which Musk responded – “All patched up!”

All patched up!

— Elon Musk (@elonmusk) June 22, 2020

The SN7 dome tank will serve as a manufacturing guidance. When the full-scale Starship test vehicle’s assembly is completed, it will undergo a cryogenic test as well. If testing goes smoothly, SpaceX teams aim to conduct a low-altitude debut test flight of 150 meters and a high-altitude test of 20 kilometers.