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posted by janrinok on Thursday November 07 2019, @01:22AM   Printer-friendly
from the 2-out-of-3-ain't-bad dept.

https://spacenews.com/boeing-performs-starliner-pad-abort-test/

WASHINGTON — NASA and Boeing said a pad abort test of the CST-100 Starliner commercial crew vehicle Nov. 4 was a success despite the failure of one of the capsule's three parachutes to properly deploy.

The Starliner lifted off from a test stand at Launch Complex 32 at White Sands Missile Range in New Mexico at approximately 9:15 a.m. Eastern time. The spacecraft's launch abort engines fired for five seconds, and a separate set of orbital maneuvering thrusters for 10 seconds, accelerating the spacecraft to more than 1,000 kilometers per hour to simulate escaping a malfunctioning rocket on the launch pad.

The capsule soared to a planned peak altitude of about 1,350 meters before jettisoning its service module and heat shield, then deploying its parachutes. The capsule, cushioned by airbags, landed about 90 seconds after liftoff.

...

"We did have a deployment anomaly, not a parachute failure," Boeing said in a post-launch statement. "It's too early to determine why all three main parachutes did not deploy, however, having two of three deploy successfully is acceptable for the test parameters and crew safety." The company added that, at the present time, it doesn't expect the issue to delay the Orbital Flight Test.

...

SpaceX, which conducted a pad abort test of its Crew Dragon spacecraft in May 2015, is preparing for an in-flight abort test in December. On that test, a Crew Dragon spacecraft will fire its SuperDraco thrusters to escape a Falcon 9 nearly 90 seconds after liftoff from the Kennedy Space Center, around the time of maximum dynamic pressure on the spacecraft. SpaceX is scheduled to perform a static fire of those thrusters as soon as Nov. 6 in preparation for that flight.

Boeing will not perform its own in-flight abort test, concluding that data from the pad abort, along with modeling of flight conditions, will be sufficient, an approach NASA approved.

Boeing and NASA are declaring the test a success because the crew and capsule would have been perfectly safe had this happened under real conditions. The capsule is designed to be able to land even following a failure of one of the parachutes. However, the reason that redundancies exist is because there are often unforeseen issues outside of test conditions. Should a test that would result in the crew living, yet one that also fails to function nominally be considered a success? If so, is this success enough to provide sufficient confidence in Boeing's ability to move forward without even carrying out an in-flight abort, which is substantially more challenging than a pad abort?


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  • (Score: 2) by FatPhil on Thursday November 07 2019, @09:27AM

    by FatPhil (863) <{pc-soylent} {at} {asdf.fi}> on Thursday November 07 2019, @09:27AM (#917262) Homepage
    I bet the problem stems to a problem in the wording of the spec.

    Maybe the spec was written by the person who could utter this sentence without realising what he was mangling:
    "It's too early to determine why all three main parachutes did not deploy, however, having two of three deploy successfully is acceptable for the test parameters and crew safety.".

    Specifically the phrase "all three main parachutes did not deploy". subject="all three main parachutes" action="did not deploy". Only sane interpretation: none of them deployed, as they all didn't deploy (if you don't believe me, subsitute "did not" with "failed to"), not the reality he's trying to describe.

    Completely different from "not all of the three main parachutes deployed". subject="not all of the three main parachutes" action="deployed". Only sane interpretation: not all 3 deployed, which is the reality he was attempting to describe.

    The only positive we can get from this result is that the shutes fail independently of each other, the redundancy is doing its job. However, if the failure rate is 1/3, then they're killing everyone 11% of the time, which ain't a great result. If the failure mode was all-or-none, then the redundancy would be utterly useless.
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