I'd be interested in seeing the original source for the 1/4" liquid nitrous
oxide critical diameter number--it does seem to contradict the extensive
experience with liquid nitrous in racing applications that David mentions.
After all, if liquid nitrous could detonate like that, I would think
someone would have tested it as an explosive (strap a detonator onto or
inside a bottle of nitrous). Maybe that would work, but TNT is better...?
The SPG site (http://www.spg-corp.com/nitrous-oxide-safety.html) states "it
is highly unlikely that a deflagration or detonation wave can be sustained
in pure (uncontaminated) liquid nitrous oxide." So I'm not sure what to
think.
On Sat, Dec 5, 2015 at 11:02 AM, David Gregory <david.c.gregory@xxxxxxxxx>
wrote:
The only literature I've located on the subject of N2O stability is here:
http://docs.google.com/viewer?a=v&pid=sites&srcid=cm9ja2V0bW9vbmxpZ2h0aW5nLmNvbXxob21lfGd4OjExOTMyNTk1MTE4ZTYzYjA
They have some very interesting conclusions. One of them is that liquid
N2O is largely stable and difficult to ignite. However gaseous N2O is
remarkably easy to ignite, even with sudden compression. The critical
diameter for gaseous N2O is on the order of a few inches.
I take these conclusions to be consistent with the data for automotive and
HPR uses of N2O (few if any reported incidents). And also consistent
with the scaled accident - cold flows of liquid N2O inevitably also involve
two phase flows, and the SS2 motor would have been well above the critical
diameter. Pg 28 has an interesting short discussion on unexplained
decomposition anomalies - several of which occurred when venting from a
pipe.
Note that quenching by the liquid phase is a common phenomenon - liquid
oxygen fires in most "compatible" materials are only ignitable in the
presence of the gaseous phase.
-David
On Fri, Dec 4, 2015 at 12:53 PM, Lloyd Droppers <ldroppers@xxxxxxxxx>
wrote:
Yes, saying that a liquid N2O has a 1/4" critical diameter means that a
tube larger that 1/4" will propagate a detonation wave while a smaller tube
can damp the detonation wave depending on the material, length, etc. 1/4"
is actually a reasonable size as far as critical diameters for rocket
monopropellants. For Ref 90%HTP is 1.0" critical diamete
<http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-10-01464>r,
Nitromethane is 0.1"
<http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.2263489>,
and I couldn't find anything else quickly.
I think that you might be setting up a false dichotomy in thinking
gaseous nitrous is the real bogeyman, as liquid nitrous is still a
monopropellant and potentially dangerous if not handled with care. You have
probably seen this but SPL has a nice intro on Nitrous safety
<http://www.spl.ch/publication/SPL_Papers/N2O_safety_e.pdf>.
Lloyd
On Sat, Dec 5, 2015 at 7:24 AM, Paul Mueller <paul.mueller.iii@xxxxxxxxx>
wrote:
Thanks for the info and I'll try to educate myself. Meanwhile, does this
mean that a 1/4" tube full of liquid nitrous could propagate a detonation
wave due to dissociation (presumably the only energy source that could
cause a detonation wave)? This seems to contradict my previous
understanding that it is very difficult to have a dissociation reaction in
liquid nitrous. Gaseous nitrous is the real boogey-man here. Am I up in the
night?
Paul M
On Fri, Dec 4, 2015 at 11:08 AM, George Herbert <
george.herbert@xxxxxxxxx> wrote:
You really want Paul Coopers grad level textbook "Explosives
Engineering".
George William Herbert
Sent from my iPhone
On Dec 4, 2015, at 9:54 AM, Ed LeBouthillier <codemonky@xxxxxxxxxxxxx>wrote:
means that it is about 1/4" for liquid nitrous oxide.
Paul Mueller said
Yeah, I'm not familiar with the "critical diameter" and what it
proceed down a tube.
The critical diameter is the diameter at which a detonation can
Smaller than that, the detonation should not propagate, large thanthat, it should.
https://books.google.com/books?id=5P-mCAAAQBAJ&lpg=PA285&ots=42Lfa7DirE&dq=critical%20diameter%20detonation&pg=PA285#v=onepage&q=critical%20diameter%20detonation&f=false
It's touched on here:
https://en.wikipedia.org/wiki/Explosive_material
and is more detailed here: