[AR] a subtle N2O hazard (was Re: breathing nitrogen)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 23 Apr 2016 00:27:03 -0400 (EDT)
On Fri, Apr 22, 2016 at 3:04 AM John Dom <johndom@xxxxxxxxx> wrote:
As to the Scaled Composites cold flow fatalities... did they perform
that test inside a non-ventilated compound as if it were LOX?
Randall has already dealt with the cause of the Scaled fatalities -- blast
injuries -- but this reminded me of something I'd been meaning to post.
Nitrous oxide (N2O) is best known to Arocket readers as an oxidizer for
hybrid and biprop systems, but there's also been interest in it as a
monopropellant. Decomposing it is tough because it's so stable (at least
when pure!), but vigorously-preheated catalysts can do it, and it does
yield substantial energy. Best to decompose it as a gas, by the way --
people who have tried decomposing the liquid report an excessive number of
loud surprises.
However, there is also a less-well-known chemical hazard lurking there.
Decomposition of N2O doesn't always go all the way to N2 and O2. In
somewhat ill-defined circumstances, you can also get significant amounts
of nitric oxide (NO) in the decomposition products. Not only is NO itself
toxic, but when it hits air, it tends to oxidize to NO2!
This happened recently to some friends of mine, who were working with
nitrous for a non-rocketry application. Fortunately, they had enough
background knowledge that when they saw brown fumes, they realized they
had a major emergency on their hands -- they evacuated the area and
ventilated it thoroughly and at length before going back in. Their later
experiments were done with a fume-removal setup, NO2 detectors, etc... and
similar precautions are in order for anyone tinkering with N2O monoprop
concepts. N2O good (maybe); NO2 bad bad bad.
Henry
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