"Alan Erskine" wrote in
:

"Damon Hill" wrote in message
...
"Alan Erskine" wrote in news:dUqBj.24424
:

But isn't that ignition/combustion?

Yes. What's the problem?

That's what I mean; why have spark ignition when they could combine O2
and H2? Surely there's a way.

Because oxygen and hydrogen don't self-ignite. Externally igniting
propellants will and have damaged the SSME on the pad during ignition
aborts; as I quoted from the Wikipedia article on the SSME, the ignition
sequence begins at the gas generator/preburners.

--Damon