The moral of the story I take from that is always, always purge your lines.

Also, ice? The ancient enemy of rocketry. Who ordered that?

p.s. exercise for the reader: how did John Carmacks helicopter rotor escape peroxide hammer?

Randall Clague wrote:
On Fri, 01 Nov 2002 21:50:56 -0800, David Weinshenker
<[EMAIL PROTECTED]> wrote:

  
China Lake had a boo-boo recently where a couple grams (which is,
admittedly, a lot of vapor) of peroxide got hit with a peroxide hammer.
      
How did they manage to contrive _that_ particular combination of circumstances?
    

The usual bag of Murphy's tricks.  You'd have to ask Dave Hall for the
details, or search the aRocket archive (I think the search function is
working again), but IIRC it went something like:

*) They had an anomaly, so they shut down the engine.
*) It wasn't a malfunction, a mishap, or other negative incident, so
they were going to start up again soon.
*) There was some heat soak from the engine to a peroxide line.
*) The heat evaporated some of the peroxide remaining in the line,
which they had not purged.
*) There was some ice in a line or valve, sticking it closed (I'm less
clear on this detail - maybe this caused the initial anomaly).
*) When the ice melted, the line pressure went up much faster than the
valves would have allowed.
*) This got peroxide flowing much faster than the design called for.
*) When the fast moving liquid peroxide hit the peroxide vapor, it
stopped.  This created a peroxide hammer.
*) The peroxide hammer compressed the peroxide vapor enormously.  Dave
gave some figure he calculated.  I don't remember it, but it was
absurdly high.  It couldn't last, of course, but it didn't have to.
*) The compression adiabatically heated the peroxide vapor to high
temperature.
*) The high pressure, high temperature peroxide vapor detonated.
Surprise!  It does that.

And last but not least, though Dave doesn't say so,

*) The people who put the system together said, "DAMN!  I thought we
thought of *everything*!"

And the moral of the story is, of course, that as good as your
imagination is, Mother Nature's is better.  (That's why you have to
gang up on her if you want your complex systems to work smoothly.)

-R

--
"...And the last thing I remember is asking,
'What could go wrong?'"
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