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A comment on Oumuamua may be a hydrogen iceberg. Parent comment

Re:Oumuamua may be a hydrogen iceberg by dmurray on Wednesday June 03, 2020 @08:22PM (#23410845)
I'm sure this is true in practice, but I can't wrap my head round why it's correct in theory. Let's say I hook up my exhaust to my intake, I can still squirt some gasoline into the engine, make it explode and expand and thereby drive a piston, at the cost of having even hotter air the next time round.

If I repeat this long enough, my engine will melt, but that's a minor matter of materials science. Maybe I can win my drag race before it melts. Is that the limiting factor or is there some other reason I'm missing that we need a heat gradient?

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Re:Oumuamua may be a hydrogen iceberg by marcosdumay on Wednesday June 03, 2020 @10:05PM (#23411526)
If you heat it more each time, yeah, the old air can act as a cold reservoir and make things run.

If you do draw it with enough detail, you'll notice that if you do not heat it more at each turn, you won't be able to get any pressure difference at your "explosion".

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