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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: 1) by khallow on Monday January 15 2018, @06:45AM (2 children)

    by khallow (3766) Subscriber Badge on Monday January 15 2018, @06:45AM (#622472) Journal

    Apollo 1 doesn't count, I guess?

    Correct, it wasn't a launch.

  • (Score: 2) by choose another one on Monday January 15 2018, @09:22AM

    by choose another one (515) on Monday January 15 2018, @09:22AM (#622499)

    Correct, it wasn't a launch.

    Umm, nor was the SpaceX COPV explosion being talked about in TFA - it was during fueling for static fire test.

    If we don't count pre-launch failures on the pad then SpaceX's record suddenly looks awful lot better.
    If we do, NASA's record looks worse.

    That is one of the problems when you have very little data - tweaking definitions ever so slightly to exclude or include one event can make a massive difference to your "safety record".

  • (Score: 2) by dry on Monday January 15 2018, @08:10PM

    by dry (223) on Monday January 15 2018, @08:10PM (#622698) Journal

    It showed a lot of design problems that would have in all probability led to flight failures. In some ways it was lucky that it failed when it did as it forced the engineers to consider things like is it smart to use a 100% oxygen environment combined with lots of flammable materials as well as simple design decisions such as how the door opens.