Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!ncar!noao!asuvax!enuxha!kluksdah
From: kluksdah@enuxha.eas.asu.edu (Norman C. Kluksdahl)
Newsgroups: sci.space
Subject: Re: Sanger
Summary: Mass Ratio for Mach 0
Message-ID: <81@enuxha.eas.asu.edu>
Date: 16 Mar 89 21:07:45 GMT
References: <1989Mar14.172237.29235@cs.rochester.edu <7234@thorin.cs.unc.edu> <7284@thorin.cs.unc.edu>
Organization: Arizona State Univ, Tempe
Lines: 27

In article <7284@thorin.cs.unc.edu>, symon@lhotse.cs.unc.edu (James Symon) writes:
> your numbers suggest to my envelope-back that the benefits of added
> speed at launch probably don't warrant the investment in a Mach 5
> launch vehicle.
> 
>  So how about Mach 0.0 
> at 125,000 ft. under a set of monster balloons?
> 

I just calculated the theoretical mass ratio, using the same assumptions
as before (i.e. negligibly small air resistance, Isp = 400).  If, at 125K
altitude, the air is negligibly thin, then orbital velocity can be
attained with a mass ratio of (roughly speaking) 5.75.

I agree with your point.  Unless Mach 5 can be attained VERY cheaply, then
it simply isn't worth the cost.  An additional point is that getting a
carrier to Mach 5 at high altitude would either require dual engines 
(i.e. turbojet and ramjet, turbojet and rocket, etc, ad nauseum) or something
akin to an air-turbo ramjet.

**********************************************************************
Norman Kluksdahl              Arizona State University
            ..ncar!noao!asuvax!enuxha!kluksdah

standard disclaimer implied

Useful criticism always appreciated.  Senseless flames always discarded.