[AR] Re: DARPA responsive launch challenge
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 21 Apr 2018 14:04:34 -0400 (EDT)
On Sat, 21 Apr 2018, Keith Henson wrote:
I believe John is referring to ALASA, not RASCAL et al. ALASA was using a
stock F-15 and a mixed-monoprop nitrous/acetylene rocket...
Given that acetylene can't be liquefied or compressed beyond 2
atmospheres without becoming shock sensitive, it amazes me that anyone
would try to make such a devil's brew.
Bear in mind that it was a DARPA project, and DARPA is in the business of
trying things that look speculative and iffy.
Given the very skewed mixture ratio -- 7:1 if I recall correctly -- the
acetylene was pretty thinly dispersed in the other component, which is the
way acetylene is routinely stored and handled in industry (although in
acetone rather than nitrous). So the acetylene itself wasn't that big a
concern. But nitrous with fuel in it, even a little bit of fuel, is
notoriously much more sensitive than clean nitrous -- that was the more
worrisome bit.
Set against that, (a) the mix was made and stored chilled well below room
temperature, and (b) there was at least one proprietary trick also
helping. So, as Mitch Burnside Clapp (then ALASA project manager) put it
three years ago, "there are reasons why this is not entirely insane".
And indeed, mixing, handling, storage, and cold-flow tests were free of
loud surprises. (This was all being done very gingerly by remote control,
of course.) But when it came to hot-fire tests, as John Schilling said,
"it is still excessively enthusiastic about ignition".
Henry
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