Path: utzoo!utgpu!water!watmath!clyde!att!whuts!sw
From: sw@whuts.UUCP (WARMINK)
Newsgroups: sci.space.shuttle
Subject: Re: Soviet and American Shuttles
Summary: lift-to-drag
Message-ID: <4887@whuts.UUCP>
Date: 12 Oct 88 16:43:07 GMT
References: <1574@nunki.usc.edu> <3020@jpl-devvax.JPL.NASA.GOV> <40869@linus.UUCP>
Distribution: sci.space.shuttle,sci.space
Organization: AT&T Bell Laboratories
Lines: 33

In article <40869@linus.UUCP>, jp@linus.UUCP (Jeffrey Picciotto) writes:
> David Smyth writes:
> >2) How fast do you thin the shuttle needs to go to get enough lift to
> >go UP?  Right now, the shuttle decends at about 100 feet per second
> >throughout the re-entry: The thing does NOT fly, it drops like a brick.
> >The wings just increase the manoeverability.
> 
> Is this really true?  How fast is it descending when it touches down?
> Assuming a reasonably slow rate of descent, doesn't this show that the
> shuttle could fly if it had useful and sufficiently powerful engines
> available?
> 

With a lift to drag ratio of approximately 4:1, it can be seen that for level flight
the thrust of the engine(s) has to be at least 25% of the Shuttle's weight.

Speed is not the only factor in determining rate of climb - angle of attack is too.
There is a tradeoff between low-speed, high angle of attack and high-speed,
low angle of attack flight, the optimum rate of climb is usually somewhere
in between.

The best gliding angle is also given by the L/D ratio (atan(D/L)), but in order to land
with zero vertical velocity the actual glideslope is steeper, and the excess energy
is used to allow for an increase of angle of attack in order to reduce the final
rate of descent to nearly zero.

So, I suppose the answer is that anything with any lift at all will fly, 
given enough thrust....
-- 
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