Question for the group mind: Has anyone out there come across
a formal methodology and/or experimental data for determining
the TNT equivalence of a LOX-Methane propellant explosion?
Not, I hasten to add, a deliberately premixed one - I think I
classified that potential blend as an "insanely dangerous" mixed
monopropellant in my Space Access talk. But we've now got
multiple launch providers talking about flying LOX-Methane
bipropellant out of the major ranges, and people are starting
to ask for specifics about how big an explosion you might get
in a worst-case accident.
Which presumably would be a low-velocity crash right next to
(or back onto!) the pad after an early engine cutoff, tank
rupture and no immediate ignition so the potential for
extensive mixing followed by detonation. LOX and methane
are fully miscible as liquids at typical storage temperatures,
and not hypergolic, so the usual explanations of why we can't
get 100% mixing and full theoretical energy release don't hold.
With LOX-Kerosene, for example, the "maximum credible event"
is assessed at about 10% of theoretical yield partly on the
grounds that the kerosene will freeze as it mixes.
I would expect that LOX-Methane would be somewhere between 10%
and 100% of theoretical yield in a worst-case crash, but that
covers a fairly broad range - and at 100% theoretical yield,
it probably covers an impractical amount of the Cape in the
blast zone. So, looking for the least troublesome way to
narrow that estimate, and if that comes down to "Yeah, the
experiments are a bitch but the guys at White Sands did that
in 1963...", this might be a place to ask.
John Schilling
john.schilling@xxxxxxxxxxxxxx
(661) 718-0955