(Oren Tirosh) wrote in message . com...
Some methods I've seen mentioned for peroxide biprop ignition a

Decompose the peroxide with catalyst pack.
Pyrotechnic igniter in the chamber.
Dissolve catalyst in fuel.
Hypergolic starting slug in fuel feed line.

How about mixing some liquid catalyst into the peroxide feed for a few
seconds until there is stable self-sustaining combustion in the
chamber? Liquid catalysts for monoprops have been abandoned in favor
of catalyst packs for good reasons but they seem to have some
desirable properties for biprop ignition:

Usable with high concentration peroxide.
Can be used with strongly stabilized peroxide.
No hazardous materials.
Restartable and reusable.


It could probably work, but I think you overstate the case for it.

Various platinum based catalysts will work fine with 98% peroxide, it
is only the classic silver ones that have issues. The commercial
catalysts we are using for our mixed-monoprop engines would work fine
with 98%, for instance.

High concentration and highly stabilized is really only a condition
that happens at the amateur experimental stage where people are
concentrating cheap peroxide on bench level equipment in small
batches. Anything resembling a commercial rocket is almost certainly
going to be using unstabilized peroxide.

Adding a third consumable and the associated plumbing is a non-trivial
increase in system complexity.

We have only done a few tests with liquid catalysts, but we have had
much better success with solid catalyst packs. Compared to almost any
other biprop, cat-pack decomposition auto-ignition biprops are really
easy to make work at good efficiencies.

John Carmack
www.armadilloaerospace.com