Space Forum / Space History / September 2008

On Wed, 20 Aug 2008 13:57:24 -0400, "Greg D. Moore \(Strider\)"
<mooregr_deleteth1s@greenms.com> wrote:

...Yeah, they really did sort of bite the dust on that one, didn't
they?

                OM

On Wed, 20 Aug 2008 13:57:24 -0400, in a place far, far away, "Greg D.
Moore \(Strider\)" <mooregr_deleteth1s@greenms.com> made the phosphor
on my monitor glow in such a way as to indicate that:

I'm not sure I've ever heard anyone make such a claim.

Per Henry Spencer, it was caused by a flaw in the test setup rather than
a flaw in the design of the Orion parachute system:

<http://www.newscientist.com/blog/space/2008/08/spacecraft-crash-due-to-test-setu
p-not.html?DCMP=ILC-rhts&nsref=ts13_head>

(Henry doesn't post to s.s.* any more, but y'all can pretend he came
back and posted this:)

Spacecraft crash due to test setup, not design flaw

NASA has quietly released photos and video of a 31 July parachute test
for its future Orion astronaut capsule that didn't go so well: the
mockup capsule hit the ground pretty hard. Unsurprisingly, some have
jumped on this, claiming that NASA is trying to cover up a failure.

The full story is a bit more complicated than that. I'm sure NASA wasn't
eager to publicise this embarrassing episode, but it wasn't exactly a
failure. There was a problem, yes, but it was in part of the test setup,
rather than in the parachutes that would actually land an operational
Orion after a trip to the space station or the Moon.

Testing a parachute drop of a heavy object is not simple. In particular,
several auxiliary parachutes were used to help set up the right test
conditions, so that Orion's own three-part parachute system would get a
realistic test. Orion uses "drogue" chutes that ensure the capsule is
stable, as well as "pilot" chutes that pull its main chutes out.

Unfortunately, some of the auxiliary chutes failed, and as a result the
Orion parachute system was activated at high speed, in dense,
low-altitude air. The drogue parachutes failed instantly on deployment
in the unrealistically harsh conditions. Then the capsule began to
tumble, main-parachute deployment was hopelessly messed up, and hope of
anything resembling a soft landing was lost.

Foul-ups in testing are not uncommon, especially when the test setup is
being tried for the first time. One of the headaches of high-tech test
programmes is having to debug the test arrangements before you can start
debugging the things you're trying to test.

Sometimes a malfunctioning test setup actually gives the tested system a
chance to show what it can do in an unrehearsed emergency. During a test
of an Apollo escape-system in the 1960s, the escape system successfully
got the capsule clear of a malfunctioning test rocket.

But sometimes the test conditions are so unrealistically severe that
there's no hope of correct functioning. Unpleasant though the result
often looks, this isn't properly considered a failure of the tested
system. That seems to have been what happened here.

Properly speaking, the outcome of this test is best summed up not as
"failure" but as "no test". That's testing jargon for "the test setup
messed up so badly that the test told us nothing about the tested
system". Expensive and embarrassing, yes, but it doesn't indicate a
problem with the Orion design.

Most likely.  Apollo had some problems with chutes, but nothing terribly
serious during actual flights.

To be fair, the failure was with the chutes used to set up the test, not the
Orion chutes.  So this wasn't so much an Orion failure as it was a failure
to test properly.

Jeff

Or that the military got it right on the first try.

No, but the Orion team should have gone to them and asked for advice on
how to do this, as they dump heavy cargo out of the rear of jet cargo
planes that then deploys chutes and descends to earth quite frequently.
They even managed to slide a Minuteman missile out the back of a C-5,
have it align nose upright under a parachute, then ignite and ascend on
its planned trajectory.

Pat