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From: logajan@ns.network.com (John Logajan)
Newsgroups: sci.physics,sci.electronics
Subject: Re: Coilguns -- help me Spock!
Message-ID: <1990Apr8.062629.6589@ns.network.com>
Date: 8 Apr 90 06:26:29 GMT
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henry@utzoo.uucp (Henry Spencer) writes:
>>>>> In case #2, you have the projectile being "pushed" in REPULSIVE (or
>>>>> opposing) mode and also being "pulled" in ATTRACTIVE (or aiding) mode.
>>	Even _*IF*_ one mode is more "efficient" than the other, _*WHY NOT
>>USE BOTH AT THE SAME TIME!!??*_  ...
>
>Stability issues are one possible reason.  The Space Studies Institute
>mass-driver people eventually settled on an all-attractive scheme, as
>I recall, because it naturally stabilized the projectile, while schemes
>using repulsive drive as well needed active stabilization.

I think it was Paul Dietz who mentioned stability to me in a private post.
(Sorry if I am attributing it to the wrong author.)  I speculated in
reply that if an off center projectile is drawn in to an attractive
magnet, that it will pick up momentum that will vector it into the side
of the barrel also.  The next stage will amplify this and so on.

It is not so obvious then, that attractive mode is more stable than repulsive
mode.  Unless there is some additional non-obvious damping mechanism
in attractive mode, I would say they both needed some sort of side to
side motion restraint.

-- 
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