If I read all this rant correctly no amateur can possibly control all the
variables. Period. So they should abstain using N2O unless they accept unk-unk
risks. Good evening.
jd
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of Paul Mueller
Sent: zondag 6 december 2015 19:28
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: ALASA canceled because... Mixed Mono
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
<http://docs.google.com/viewer?a=v&pid=sites&srcid=cm9ja2V0bW9vbmxpZ2h0aW5nLmNvbXxob21lfGd4OjExOTMyNTk1MTE4ZTYzYjA>
&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
<http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-10-01464>
" critical diameter, 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:
Paul Mueller said
Yeah, I'm not familiar with the "critical diameter" and what it means that
it is about 1/4" for liquid nitrous oxide.
The critical diameter is the diameter at which a detonation can proceed down
a tube.
Smaller than that, the detonation should not propagate, large than that, it
should.
It's touched on here:
https://en.wikipedia.org/wiki/Explosive_material
and is more detailed here:
https://books.google.com/books?id=5P-mCAAAQBAJ
<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>
&lpg=PA285&ots=42Lfa7DirE&dq=critical%20diameter%20detonation&pg=PA285#v=onepage&q=critical%20diameter%20detonation&f=false