A real quirk about nitrous beyond what has already been said, is its poor
thermal heat transfer properties. A cylinder can sit all day as the ambient
temp goes up the central mass of nitrous will not. So siring mechanisms are
used to equilibrate the liquid temp. Even small volumes exhibit this
quality so amateurs are affected even with little motors. Most of the time
it goes unnoticed because it's saturated,self pressurizing, properties are
all an amature usually cares about.
It can and has killed people too, 3 in 2007 at Mojave. Just be careful
beyond LOx careful.
K
On Wed, Jan 13, 2021 at 11:41 AM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Wed, 13 Jan 2021, Jack Hanna wrote:
...so i'm wondering what
are some best practices for nitrous oxide handling...
Aside from the obvious basics of handling a liquid that has to be kept
under high pressure, the key things to understand about nitrous are that
(a) it's a monopropellant, capable of decomposing energetically and maybe
violently, and (b) it's terribly sensitive to contamination.
Pure nitrous is fairly benign and will take a lot of abuse and just sit
there. Even a little bit of organic contamination makes it much touchier,
more likely to do something violent if mistreated slightly. And it's an
extremely good solvent for almost anything organic -- lubricants,
sealants, minor ingredients of plastics, etc. -- and *will* pick up
organic contamination if you give it the slightest chance.
After several scary little incidents with surprise decomposition of
nitrous, XCOR instituted LOX-grade cleaning for all nitrous plumbing, and
had no more.
In fact, you could do a lot worse than to read up on LOX safety practices,
and apply them to nitrous. Almost every LOX hazard has some sort of
equivalent for nitrous, although sometimes not as bad. For example, in
LOX plumbing, any space where LOX can get trapped between two closed
valves needs a relief valve, because it will eventually start to boil, and
without a relief valve, pressure will go up until something bursts.
Nitrous won't do that... but the liquid *does* have a very high
coefficient of thermal expansion, so if it's a hot day, and your nitrous
comes out of a tank that's still cold, and then the liquid sits trapped
between valves, warming up, its pressure *can* rise quite impressively.
Beware of "we got away with it repeatedly so it must be okay"; that's what
killed the crews of Challenger and Columbia, and probably also the three
people who died in the Scaled Composites nitrous explosion. You need to
learn from the people who did have accidents, not just the ones who
didn't. The single most dangerous thing about nitrous is the widespread
belief that it's as safe as mother's milk. Treat it as dangerous and keep
it clean, and it will behave itself.
Henry