🚀 go-pugleaf

In article <1989Mar14.172237.29235@cs.rochester.edu,
dietz@cs.rochester.edu (Paul Dietz) writes: 
> . . . Sanger would use turboramjet engines to propel a winged 
> first stage to Mach 5, at which point a LOX/LH2 propelled second stage 
> -- either an unmanned expendable cargo rocket (like Pegasus) or a 
> reusable winged manned vehicle -- would be released to ascend to 
> orbit.  

I would think that the greatest advantage an air launch would have
over ground launch would be initial altitude not initial speed. Mach 5
is pretty tough to achieve with a cargo vehicle and is only about 20%
of orbital speed so why bother getting up to that speed with your
launcher/first stage? Sounds like a lot more trouble and expense than
a traditional first stage, even after initial development costs.

Getting up to good altitudes might be useful, though, to get above all
that air resistance. Let the air help you instead of fighting you.
Design your aircraft first stage to achieve maximum altitude and
forget about speed except as it comes along as a free bonus.

Is the battle against high density air also a small percentage of the
effort and not worth it? How much of the work of an expendable first
stage could be done with an aircraft without significant design
innovation? Would effort be more profitably expended in going for
altitude or speed? What's the d/d$?

jim
symon@cs.unc.edu
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