[AR] Re: OT: Iron Man becoming real
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket <arocket@xxxxxxxxxxxxx>
- Date: Sun, 12 May 2019 23:04:50 -0400 (EDT)
On Mon, 13 May 2019, Ivan Vuletich wrote:
Somewhat more on topic, how practical would it be to integrate small jet
turbines like the ones in the videos into a first stage for an HPR rocket?
It's not a ridiculous idea, if you don't want your first stage to go very
high or very fast(*), but why would you bother? What does it do for a
rocket that a rocket first stage can't do better and cheaper?
Jets win for cruising. It's very hard to beat rockets for accelerating.
Those are two quite different applications -- don't confuse them -- and
first stages almost always are about accelerating.
(* Beyond about Mach 2, jet air intakes become a difficult and complex
design problem; they're not trivial even at subsonic speed, especially if
there's a lot of vehicle body ahead of them, but Mach 2-ish is where it
gets really bad. And since the air thins out as you climb, the problem of
getting useful amounts of thrust -- already hard with jets' lousy T/W --
turns a speed limit into an altitude limit. )
Henry
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