[AR] Re: Hypergolics with N2O?
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 24 Feb 2023 11:26:03 -0500 (EST)
On Fri, 24 Feb 2023, Ben Brockert wrote:
I'd expect that anything that is usefully hypergolic with oxidizers like
LOX or nitrous has to be pyrophoric as well. TEA/TEB will autoignite in
air. Anything that can strip oxygen off liquid nitrous is probably going
to be happy to burn in 21% oxygen gas.
Yeah, especially given how stable (pure) nitrous is at room temperature,
you'll need something pretty aggressive to get *fast*, *reliable*
hypergolic ignition. And nothing less will do, for a rocket engine.
Lots of combinations that do generally ignite on contact don't do it quite
vigorously enough for safe rocket ignition.
Note that something can be "pyrophoric" by the technical definition even
if it sometimes takes several *minutes* to ignite in air. Or if ignition
is very sensitive to, e.g., whether it's dry air or humid air.
How does a silane leak demolish a building, rather than burning at the
leak location?
It doesn't reliably, immediately ignite on contact with air, as witness
Rotary's experience. Often, frequently, even usually, but not always.
And delayed ignition gives it time to mix with the air...
There is some suspicion that absolutely pure silane, SiH4, is not
pyrophoric, that the ignition is the result of traces of higher silanes
(the silane equivalents of ethane, propane, etc.) formed as impurities in
manufacturing. Which would explain why its behavior varies.
Henry
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