But the comparison is mixing with pure O2. That is a big difference.
Dave
On 5/25/2016 4:25 PM, Paul Breed wrote:
> 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 <mailto: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
<mailto: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
<mailto: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 Systems
415-244-9171 <tel:415-244-9171>