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From: ems@amdahl.UUCP (ems)
Newsgroups: net.space
Subject: Re: homemade railguns...
Message-ID: <2653@amdahl.UUCP>
Date: Mon, 27-Jan-86 16:58:22 EST
Article-I.D.: amdahl.2653
Posted: Mon Jan 27 16:58:22 1986
Date-Received: Wed, 29-Jan-86 06:35:21 EST
References: <8601171419.AA20243@s1-b.arpa>, <2611@amdahl.UUCP> <6308@utzoo.UUCP>
Organization: Circle C Shellfish Ranch, Shores-of-the-Pacific, Ca
Lines: 35
Summary: But for demos, are high speeds needed?

In article <6308@utzoo.UUCP>, henry@utzoo.UUCP (Henry Spencer) writes:
> > It was my understanding that rail guns took a fractional second
> > to a few seconds to accelerate something depending on design.
> > Surely a model could be built that would be able to use computer
             *****
> > grade caps?
> 
> But the output velocity probably wouldn't be too hot, not from a gun

The original discussion was about building a model gun.  I took this
to mean a lab gun for 'playing with'.  Not one that would reach
hazardous velocities.  I can see where others might take 'model' to
mean 'prototype of small size' with realistic performace velocities.

> of practical length.  Assuming a constant acceleration, v^2 = 2ad,
> which translates as "to get a high velocity, you need either a high
> acceleration (short transit time, high currents, low-inductance caps)
> or a very long gun (gets physically cumbersome very quickly)".  The
> problems of gun length are why rail-gun and mass-driver work tends to
> push for very high accelerations.  Phrased another way, again for a
> constant acceleration, v = 2d/t, which means that a velocity of hundreds
> of meters per second (a high-velocity rifle is maybe a thousand) means
> acceleration times of a few milliseconds if the gun is to fit in an
> average-sized room.

For more modest accelerations, could not the time be extended to a
few hundredths of seconds for a 10 metre or so rail gun?

(Yes, I know I should do the math, but it is so much easyier to let
 someone else do it ...)

-- 
E. Michael Smith  ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems

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