SpaceX tests 7th Starship test prototype to failure


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Capitalism in space: As they had planned, SpaceX has done a tank pressure test of its seventh Starship prototype to failure, destroying the prototype.

This was actually the second test to failure for this tank, which is testing a new stainless steel alloy. The first had only sprung a leak that could be repaired.

Deemed 304L, the type of steel is still readily available off the shelf and only 10-20% more expensive than the 301 alloy SpaceX has used to build all Starship prototypes up to SN7. The biggest change it brings to the table is improved ductility (malleability), particularly at the cryogenic temperatures Starship’s tanks will often be held at. By reducing brittleness, Starships built out of 304L steel should be able to fail far more gracefully by developing stable leaks instead of violently decompressing. In fact, the very same test tank destroyed on June 23rd demonstrated that capability perfectly when it sprung a leak during its first pressure test on June 15th.

During its first cryogenic pressure test with liquid nitrogen, SpaceX CEO Elon Musk revealed that the SN7 test tank managed to reach 7.6 bar (~110 psi) before it began to leak – technically satisfactory for orbital Starship launches with an industry-standard 25% safety factor. Thanks to the general flexibility of steel, including the new 304L alloy SN7 was built with, SpaceX was able to simply repair the leak it identified, readying the test tank for a second cryogenic pressure test barely a week later.

Below the fold are two videos showing this second failure. Unlike earlier tests using different alloys, the tank does not go flying hundreds of feet into the air. The rupture seems more gentle, if I can use such a word for such a failure.

They have another tank ready to go, so testing should proceed quickly even after this test failure. And they also are prepping the full scale #5 Starship prototype for testing, which if all goes well will include actual test hops.

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3 comments

  • Ray Van Dune

    Do we know how many Bar the second test of SN7 got to?

  • mpthompson

    I haven’t heard how high the test of SN7 went. Elon usually tweets the values a few days after (sometimes quicker) so it will probably be released in the next few days. It seems SpaceX ultimately needs to be above 8.4 Bar to achieve the safety margin for manned flight, so hopefully, it will be close to that or higher.

  • Michael

    Here is a neat video of Zeus checking out the area in the aftermath.

    https://www.youtube.com/watch?v=Bm5hrbLSH2k

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