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posted by Fnord666 on Sunday January 14 2018, @06:53PM   Printer-friendly
from the space-is-risky dept.

Safety panel raises concerns about Falcon 9 pressure vessel for commercial crew missions

An independent safety panel recommended NASA not certify SpaceX's commercial crew system until the agency better understands the behavior of pressure vessels linked to a Falcon 9 failure in 2016. That recommendation was one of the stronger items in the annual report of the Aerospace Safety Advisory Panel (ASAP) released by NASA Jan. 11, which found that NASA was generally managing risk well on its various programs.

The report devoted a section to the composite overwrapped pressure vessels (COPVs) used to store helium in the second stage propellant tanks of the Falcon 9. The investigation into the September 2016 pad explosion that destroyed a Falcon 9 while being prepared for a static-fire test concluded that liquid oxygen in the tank got trapped between the COPV overwrap and liner and then ignited through friction or other mechanisms.

SpaceX has since changed its loading processes to avoid exposing the COPVs to similar conditions, but also agreed with NASA to redesign the COPV to reduce the risk for crewed launches. NASA has since started a "rigorous test program" to understand how the redesigned COPV behaves when exposed to liquid oxygen, the report stated. ASAP argued that completing those tests is essential before NASA can allow its astronauts to launch on the Falcon 9. "In our opinion, adequate understanding of the COPV behavior in cryogenic oxygen is an absolutely essential precursor to potential certification for human space flight," the report stated, a sentence italicized for emphasis in the report.

[...] The report raised issues in general about the commercial crew program, including concerns that neither Boeing nor SpaceX, the two companies developing vehicles to transport NASA astronauts to and from the International Space Station, will meet a requirement of no greater than a 1-in-270 "loss of crew" (LOC) risk of an accident that causes death or serious injury to a crewmember. That includes, the report stated, a risk of no more than 1 in 500 for launch and reentry.

Both programs are likely to be delayed:

Boeing, SpaceX have razor-thin margins to fly crew missions in 2018


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  • (Score: 3, Informative) by JoeMerchant on Monday January 15 2018, @04:36AM

    by JoeMerchant (3937) on Monday January 15 2018, @04:36AM (#622427)

    So, while I generally agree with the water-skiing cliche': if you never wipe out, you're not trying hard enough... on the other hand, you wouldn't catch me boarding any vehicle that puts LOx in contact with composite materials as described in the summary - that's un-necessary risk.

    There's plenty of risks from unknown unknowns in spaceflight, when we get manned missions out of LEO again, we're going to hit plenty of those... no need to add additional risk from known issues that can be addressed in design. Also, a design risk of no more than 1/500 is just asking everybody's best guess to come out to better than 0.2%, not guaranteeing anything about actual risk.

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