If a 4% concentration of hydrogen in ambient air goes BOOM...

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

You're under the mistaken impression that O2 mixed with H2 at cryogenic
temperatures results in instantaneous combustion. It does not. Even at
room temperature, it does not. You *have* to have some sort of ignition
source, like a spark generator.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein

On Mar 11, 3:22 am, Damon Hill wrote:


If you're referring to the external spark generators, that's only to
ignite venting hydrogen before it builds up to explosive levels, which
might happen if the engines are shut down on the pad.

The ignitors are for engine start vs shutdown
The start sequence is fuel rich ROFI's (radially outward firing
ignitors) are used to prevent an overpressure once the engines
ignite.

Maybe it would go bang rather than whoosh?

Brian in a slightly silly mood.



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"Alan Erskine" wrote in message
...
...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?