[AR] Re: More MAX delays.
- From: "Troy Prideaux" <troy@xxxxxxxxxxxxxxxxxxxxx>
- To: <arocket@xxxxxxxxxxxxx>
- Date: Tue, 28 Jan 2020 11:02:08 +1100
However we do know that the activation energy is very high, above 250
kJ/mol. The bonds in the molecule are strong, and the ends of the
molecules, being partly negatively charged, repel each other and prevent
close contact.
This means that in order to get nitrous to decompose you need a high
concentration of energy in one spot.
The activation energy of N2O decomposition is considered very high for *pure*
(uncontaminated) N2O but can be significantly reduced with organic
contamination particularly under higher pressures (from the scaled composites
report):
"Also, the system pressure significantly affects the ignition sensitivity of
***liquid*** N2O. For example, N2O flowing at 130 psi in an epoxy composite
pipe would not react even with a 2500 J ignition energy input. However, at 600
psi, the required ignition energy was only 6 J."
And one of my favourite quotes from Randall Clague (from his time at XCOR):
"The only percussive problems we ever had with nitrous oxide were traceable to
fuel contamination. In pure form, it's annoyingly hard to get nitrous to
decompose. In the presence of fuel, it's annoyingly easy"
This increase in sensitivity is utilised as a virtue for conventional N2O
hybrids (in particular) and biprops that keep organics far away from the
oxidizer until they meet in the CC - augmenting virtues such as the
minimization injector complexity for hybrids, O:F mixing and allowing deeper
throttling with minimal development.
Of course, it also provides (perhaps) insurmountable challenges to developing
a stable monoprop utilising a temperamental organic additive such as acetylene
- which (without N2O) can be significantly stabilised in diluted
concentrations, but with N2O... another story.
Troy
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