People have made videos of the Dragon pad abort test superimposed on the
SLC-40 explosion. The Dragon does not start moving until there is visible
flame, and the flame never reaches it.
WRT detonation, there is such a beast as a deflagration-to-detonation
transition, and people put a lot of work into preventing or postponing that
transition. No one talks about reversing it. My understanding is that if
you have a detonable mixture, and a detonation begins, it continues until
the mixture is consumed.
-R
On Sunday, September 11, 2016, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
I've seen a detonation so small that the engine was still there and usable
after - no damage to the stand either. It was a small amount of methane
mixed with air touching off externally; the small shockwave only showed up
in video review (brightly sunlit) afterwards.
My guess in this instance would be that there was a relatively small
explosion (possibly a detonation) that initiated the visible flame
eruption, to produce the flame size achieved in one video frame. There
were undoubtedly other relatively small (relative to the overall propellant
load, at least) explosions (possibly detonations) as well, notably when the
payload's maneuvering propellant touched off. The majority of the fuel and
LOX seemed to go up in a mere deflagration, however. Only an "explosion"
in Hollywood.
I find it more interesting that Musk said the Crew Dragon escape would
have had time to work. This may imply that the apparent several seconds of
noisy lead-in to the visible initial explosion actually does represent
things going visibly wrong in the telemetry. (I suspect NASA would be more
than a little nervous about taking him at his word if he's talking about an
escape initiated only after the initial visible explosion, FWIW. I'm not
sure I'd want a seat for that experiment either...)
Henry
On 9/11/2016 4:19 PM, Ben Brockert wrote:
It's nice folksy rocketeer wisdom, but is there any real reason to
think there wasn't any detonation at all? That's a lot of fuel and
oxidizer in close proximity on fire, and a simple tank burst from
pressure doesn't make a sharp boom audible and shaking windows from
ten miles away.
And no, it wasn't a BLEVE.
I've also had a detonation on a test stand, and the test stand and
engine were still there. Detonations aren't magic, and it's possible
to have a small one.
On Sun, Sep 11, 2016 at 6:32 PM, Randall Clague <rclague@xxxxxxxxx>
wrote:
"If you go out to the test stand and the test stand is severely damaged,
you
had a case burst. If you go out to the test stand and you can't find the
test stand, you had a detonation." --Dave Hall
On Friday, September 2, 2016, Marcus D. Leech <mleech@xxxxxxxxxx> wrote:
On 09/02/2016 05:01 AM, Aplin Alexander T wrote:
what
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FWIW, Elon Musk has tweeted to say it wasn't actually an explosion (and
that Dragon would have been able to save itself):
"@scrappydog yes. This seems instant from a human perspective, but it
really a fast fire, not an explosion. Dragon would have been fine."
https://twitter.com/elonmusk/status/771479910778966016
There was a window-rattling kaboom or two. It was an explosion, but
it *WAS NOT* was a detonation.
When you have a test-stand explosion you can tell the difference
between a
mere explosion, and a detonation easily. In the former case,
there'll be burnt, and perhaps mangled, wreckage. In the latter, you
can no longer find the test-stand :) :)
Alex Aplin
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