I bet against it and I was in charge of mission assurance for the
program. But it was worth a try, so long as it could be done safely,
and we figured out how to do that much at least. Then I kept getting
surprised by how well it worked at every step of the process, all the
way through cold-flow testing on a real engine. You just couldn't keep
the reaction confined to the combustion chamber; it would propagate
upstream through the injector and manifold, and by the time it reached
the run tank it had transitioned to a high-order detonation. The
high-speed camera footage was truly spectacular.
It's possible that using ethylene rather than acetylene would have tamed
it enough to make it workable, but the Isp wouldn't have been much over
300 seconds and ALASA needed 320, so there was no funding for it. If
someone ever does give it try, with the resources to do it right, I'll
give them whatever pointers I can.
John Schilling
john.schilling@xxxxxxxxxxxxxx
(661) 718-0955
On 1/23/2020 12:56 PM, Henry Spencer wrote:
On Thu, 23 Jan 2020, Peter Fairbrother wrote:
"However, DARPA ended plans to perform a flight demonstration with ALASA in November 2015 after discovering that NA-7 was too volatile to be safely handled."
While I guess up to half of what I buy is not really used much or well, I think 'most everyone here could have told them that...
In fairness, DARPA exists to try things that are too speculative for normal military funding channels. It's quite predictable that many of the ideas they try are flops.
Nitrous/acetylene, alarming though it sounds, actually managed to pass safety tests for things like handling, which I would definitely have bet against. (And remember that F-15s are in the *business* of carrying objects stuffed full of high explosive...) It just didn't turn out to be quite tolerant enough for full-scale hot firings.
Henry
