Re: Jet engine 1st stage

k...@xxxxxxxx wrote:
> Thank you, but it doesn't answer the question. What is it about space
> launches that makes rockets better, and what is it
> that is different about atmospheric flight that makes jets better?

> So far as I can see, it boils down to this:

[snip]

You skipped a couple of issues that I addressed in my earlier post.

There's the issue of oxidizer availability. Jets need external oxygen.
Common destinations in space are notoriously short of oxygen. Thus, if
you want a jet-powered spacecraft, you need to operate it in the air
for most of the period when you're accelerating to orbital (or escape)
velocities.

That leads to practical engineering issues. It's easy to make a rocket
run at mach 25 (1950s technology). It's rather harder to make a jet
engine run at mach 5, let alone mach 25.

So, rockets usually end up being easier and more economical to harness
for orbital flight.

As you identified, the overwhelming fuel efficiency advantage of jet
engines makes them preferable for sustained subsonic flight.

> It would be interesting to compare rocket-powered ballistic launches to jet
> engines for efficiency of point-to-point passenger transport.

That's been done. Depending on the exact assumptions in the analysis,
you can sometimes finagle a result that shows rockets to be
cost-competitive for intercontinental flights. Have you googled the
topic yet?

> But none of the experts have chosen to actually come out
> and say one way or the other.

If you want an number-filled answer from a professional aerospace
engineer, perhaps you should contact an aerospace firm instead of
asking a newsgroup populated primarily by rocket enthusiasts and
amateurs. Statistically, you're more likely to get a response from the
non-experts here.

Mike Miller

.

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