At 01:14 AM 9/13/2003 -0700, Randall Clague wrote:
You misunderstand: I don't care how hard the design problem is. I'm
not going to design a turbojet/turbofan engine; that would be stupid.
I'm going to buy one.
You misunderstood me -- buying one isn't enough. You have to design an inlet for one, and you most certainly can't buy that. Thing is, the inlet is far and away the most complex part of a ramjet. The only things he has to design that you don't have to are a burner and a nozzle. Those are relatively easy to design.
Ian, OTOH, can't buy one. He has to design his. I automatically win the design competition, because I didn't have to do any work.
Actually, you have to do most of the work he has to do, and he gets a *MUCH* lighter system, which probably saves him enough elsewhere to win.
Dunno. Actually, I'm on Randalls side at the moment more- the thrust:weight ratio of the ramjet is pretty similar (the jet engine weighs more but the compressor gives it more thrust, so the jet is smaller, and it mostly balances out).
I think a ramjet would win big if you wanted to cost reduce the booster. I don't think it's in any way a silly idea, but I suspect most sane developments would just drop a jet engine in (if there was a suitable one anywhere, otherwise a ramjet is probably a better choice than what Kistler was up to).
It may very well be that a ramjet would be really easy, but you don't know that until you actually try it, and straight away you've got a risk in your program; and then you'd be looking to hedge the risk, in which case you'd go for the jet engine too, but then you've got two developments to do the same thing, so you'd probably drop the ramjet (although a really inspired choice would be to run the two in parallel for a bit before making a decision based on how it was going- the two are close enough that you'd get synergy.)
You might be able to hire an aerospace engineer from somewhere and give him the spec for the ramjet and say- go build. It would probably take a couple of years, but it's still probably cheaper than buying a turbojet- that's what? 10 man years worth?
If it was a manned booster you may prefer the turbojet though; which is probably more where Randalls head is I suspect. Although if you've got rockets on it anyway, you may use them for a go around; so it's not completely obvious.
Hope that's clear :-)
-p
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