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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.space
Subject: Re: Electromagnetic mass drivers
Message-ID: <4617@utzoo.UUCP>
Date: Sun, 11-Nov-84 00:16:55 EST
Article-I.D.: utzoo.4617
Posted: Sun Nov 11 00:16:55 1984
Date-Received: Sun, 11-Nov-84 00:16:55 EST
References: <2298@ihnss.UUCP>
Organization: U of Toronto Zoology
Lines: 22

> The main restrictions on electromagnetic mass drivers are:
> (1) the object must contain quite a bit of iron (of course)
> ...

You are thinking of induction motors, which are essentially obsolete
as electromagnetic accelerators.  Nowadays the favored accelerator
technology is the linear synchronous motor, which requires magnetic
coils on the accelerated object.

And by the way, a "mass driver" is a specific type of accelerator in
which the payload is carried by a bucket for acceleration, and the
bucket is then decelerated for re-use while the payload continues on.
This permits accelerating small payloads without throwing away a costly
magnetic-coil system for every payload.

"Mass driver" is **NOT** a generic synonym for "electromagnetic catapult".
Electromagnetic catapults have been around for quite a while.  The mass
driver, with its recirculating buckets, was invented by a specific man:
Gerard O'Neill.  He could have patented it, and perhaps should have.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry