"Damon Hill" wrote in message
...
"Alan Erskine" wrote in
:

...why do the SSME's have an ignition system? Why don't they just mix
a small amount of H2 and O2 in an ignition system?

The SSME has an internal ignition system, in both gas generators;
they're literally spark plugs. Necessary since a precisely controlled
startup sequence is required and just mixing the two propellants won't
result in ignition, unlike hypergolic propellants.

But isn't that ignition/combustion?