Newsgroups: sci.space
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Room Temperature fusion - possible indications?
Message-ID: <1989Mar28.174538.22118@utzoo.uucp>
Organization: U of Toronto Zoology
References: <290@vlsi.ll.mit.edu> <1098@Portia.Stanford.EDU> <296@v7fs1.UUCP> <5849@pdn.nm.paradyne.com> <1989Mar26.003753.11770@utzoo.uucp> <5853@pdn.paradyne.com> <24998@amdcad.AMD.COM> <7739@pyr.gatech.EDU> <369@hydra.gatech.EDU>
Date: Tue, 28 Mar 89 17:45:38 GMT

In article <369@hydra.gatech.EDU> dsm@prism.gatech.EDU (Daniel McGurl) writes:
>Ah, but you miss a critical point, the only fuel required is to get out to the
>Asteroid belt.  Getting the asteriods back involves just giving them a push
>of sorts (unless you are in a hurry...

Pushing even a small asteroid -- say a mere million tons -- into an orbit
that crosses Earth's is going to require more than a little bit of fuel.

>... Also, the space ship could probably slow in a
>way similar to the shuttles when it returns to Earth, just use the atmosphere
>as a speed brake.

At the kinds of velocities we've been talking about, no it can't.
Aerobraking works fine at a few kilometers per second.  At thousands of
kps, it doesn't work at all:  you have your choice of vaporizing, slamming
into the ground and making a large crater, or zipping off into space after
losing only a small fraction of your speed.  There is no way you are going
to lose hundreds or thousands of kps of speed in a distance of a few
thousand kilometers without vaporizing.  (Not to mention the small problem
that this involves decelerations of many thousands of Gs.)
-- 
Welcome to Mars!  Your         |     Henry Spencer at U of Toronto Zoology
passport and visa, comrade?    | uunet!attcan!utzoo!henry henry@zoo.toronto.edu