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Path: utzoo!watmath!clyde!akgua!astrovax!ks
From: ks@astrovax.UUCP (Karl Stapelfeldt)
Newsgroups: net.space
Subject: Re: Challenger's new launching attitude
Message-ID: <307@astrovax.UUCP>
Date: Sat, 21-Apr-84 15:41:12 EST
Article-I.D.: astrovax.307
Posted: Sat Apr 21 15:41:12 1984
Date-Received: Sun, 22-Apr-84 09:19:22 EST
References: <12075@sri-arpa.UUCP> <205@ames-lm.UUCP> <297@astrovax.UUCP>
Organization: Princeton Univ. Astrophysics
Lines: 15


     Phil Karn points out (quite correctly) that my earlier posting is
essentially too restrictive.  The orbiter can direct its thrust through the
center of mass of the orbiter/ET combination and still accelerate upward and
downrange.  In an effort to salvage credibility, I note that the geometry
of the combination (for a given flight path angle with respect to the
orbiter wing plane, coincident with the thrust vector) dictates that the
cross-sectional area of the vehicle to the direction of flight (and thus the
aerodynamic drag force on the combination) is a minimum for the configuration
that we are all used to seeing.  Thus while the vehicle is still ascending
through the atmosphere, it seems to me that there is a strong fuel economy
incentive for the orbiter-below-ET attitude.  However, once the vehicle
has climbed above most of the atmosphere (essentially the last 3/4 of the
ascent), there seems to be no restriction of this kind on the orientation
of the orbiter with respect to the tank.  Thanks for your correction, Phil.