Re: VTVL?

Jeff Findley wrote:
"Sylvia Else" <sylvia@xxxxxxxxxxxxxxxxxxx> wrote in message news:46ae6237$0$15276$afc38c87@xxxxxxxxxxxxxxxxxxxxxxx
All existing launch vehicles are pure rocket powered, unwinged, and launch vertically. It seems more than likely that the launch profiles used are optimum for those vehicles. Otherwise one would have to assume gross incompetence on the part of the engineers.

However, move away from pure rockets and add wings, and there's no reason to suppose that the optimum profile remains the same.

Some posters seem to be taking the view that the launch profile used for existing launchers is the optimum for all launchers, and from that concluding that neither wings, nor air breathing engines, are viable. The circularity of such an argument is obvious.

If you're talking a new aircraft with a hypersonic separation, to optimize performance, then I think this approach is extremely challenging from an economic point of view. Taking the approach of hypersonic separation from the air breathing stage necessarily means development of an entirely new aircraft. That's expen$ive! I'd guess that such a launch vehicle may be cheaper than an all rocket powered launch vehicle if the air breathing part of the vehicle is fully reusable and flight rate is sufficiently high that you're launching it (or one of its sister ships) on the order of more than one per day. Only then do I think you'd have a chance of eventually paying for the development of the hypersonic air breather.

That's not really the point at issue. The question is whether an analysis done in the past can provide a definitive answer about the relative costs of future solutions using technologies that didn't exist at the time of the analysis.

Sylvia.
.

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