[AR] Re: LOX-Methane Kabooms
- From: Paul Breed <paul@xxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 25 May 2016 16:25:40 -0700
mixing with buffer gas (air).
Not 100% sure this helps your case... just methane mixed with air could
make a really big bang....
The largest non nuke explosive has just 7 tons of fuel...
(Russian FOAB) 44Tons TNT equivalent...
Could easily have way more methane than that in a launcher accident....
On Wed, May 25, 2016 at 2:48 PM, David Masten <dmasten@xxxxxxxxxxx> wrote:
The latest document is from 2008 with correction 1 Sept 2, 2011.
6055.09-M, volume 5 is the one of interest, specifically table V5.E4.T5
(which is nearly identical to 2005's 6055.09-STD C9.T18).
It may very well be the case that LO2/LCH4 should be treated more like
LO2/LH2 than LO2/RP-1. The greater of 8W^2/3 or 0.14W for LH2 gives greater
than one adjustment at smaller quantities (<~500lb) while only 14% at huge
quantities. Is this because any credible mixing would be limited due to
pure volume and time? I'm thinking if the BLEVE shock case it occurs before
time to mix, otherwise in the open and sufficient time to get full mixing
it would also involve dissipation and mixing with buffer gas (air). I don't
know, just trying to think through it.
Thanks,
Dave
On 5/25/2016 2:12 PM, George Herbert wrote:
That's the standard, yes; the question is if it's right or not.
The difference between 10 tons HE equivalent probably typical (plus
satisfying fireball), and 225 tons at C9.T18 (20% to 500k lbs 10% above
that), to a possible 1.3 kilotons for a Falcon Heavy at 100% TNT
efficiency, to a worst case ~ 4 kilotons for the full load of Kerosene at
43 MJ/Kt...
I am not convinced the scenarios *past* 100% RE are implausible... The
propellant energy density is ~3x higher than TNT.
Assuming it will always necessarily go very inefficiently, especially if
something falls back into a flame trench and ruptures and mixes before
ignition, seems unwise. That's the point. A Falcon-9 contains over a
kiloton of unreacted energy, a Falcon Heavy about 4 kilotons...
George William Herbert
Sent from my iPhone
On May 25, 2016, at 1:33 PM, Randall Clague < <rclague@xxxxxxxxx>
rclague@xxxxxxxxx> wrote:
Has no one on this thread read DDESB-6055.9? It's the standard reference
on the topic. LOX/hydrocarbons, all of them, are rated at 20%. If you have
40,000 lbm of LOX/methane, and it goes bang, it will have a TNT equivalent
(NEW) of 8000 lbm.
The Quantity-Distance for blast is 40*(NEW^(1/3), units are feet and
pounds. For 8000 lbm, that comes to 800 feet. That's not useful, because
the Hazardous Fragment Distance for even the smallest quantity of explosive
mixture is 1250 feet.
Jeff Greason and I did have some success convincing AST that if you could
dump one of your propellants, you need only consider the stoichiometric
complement to whatever you hadn't been able to dump before impact. For
example, if kerosene (assuming O:F of 2.6:1) remaining at impact was 1000
lbm, but LOX remaining was only 520 lbm, your NEW would not be 304 lbm, as
6055.9 would have it. It would be 144 lbm.
That's only useful if you can dump a propellant, of course.
-R
On Tuesday, May 24, 2016, Keith Henson < <hkeithhenson@xxxxxxxxx>
hkeithhenson@xxxxxxxxx> wrote:
On Tue, May 24, 2016 at 10:08 PM, Henry Vanderbilt
<hvanderbilt@xxxxxxxxxxxxxx> wrote:
Seems to me it might be worthwhile to come at this from the opposite
end: What conditions would be necessary to produce thorough mixing of
the majority of a vehicle's LOX-CH4 propellants, followed by detonation?
At least once in a test the tank valves opened without ignition and
the whole load of RP-1 and LOX drained out through the engine. The
mix was called gel and tended to be treated like nitroglycerine. In
this particular event (which I don't remember even what rocket it was
or when), the aftermath was a rocket sitting in a large pool of gel.
According to the story related to me, the test engineers just walked
away and waited a few hours till all the LOX evaporated.
There are people who have fun by filling two liter soda bottles with
LOX and propane. Apparently if you let the bottles warm up a little,
the propane becomes miscible with the LOX. If you shoot at the
bottles with a 30-06, about half the time they will detonate (with an
impressive bang). So apparently that hydrocarbon and LOX isn't as
sensitive as nitro. On the other hand, tracer ammo will set off such
mixes every time.
Keith
--
David Masten
CTO
Masten Space Systems415-244-9171
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