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From: dietz@SLB-DOLL.CSNET (Paul Dietz)
Newsgroups: net.space
Subject: Rail guns vs. ordinary guns
Message-ID: <8601182306.AA26432@s1-b.arpa>
Date: Sat, 18-Jan-86 16:10:15 EST
Article-I.D.: s1-b.8601182306.AA26432
Posted: Sat Jan 18 16:10:15 1986
Date-Received: Mon, 20-Jan-86 04:22:46 EST
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Organization: The ARPA Internet
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There are several advantages of an electric gun over a chemical gun.  First,
the chemical gun is limited by the velocity of sound in the gas; if the
projectile moves faster than the gas particles it can't be accelerated.
Unless exotic propellants are used (pressurized hydrogen, for example)
velocity is limited.  Second, the gas in a conventional gun fills the
entire space between the breach and the projectile, meaning that gas
has to be added while the projectile is being accelerated (hard)
or the initial pressure must be very high.

A conventional railgun shares the second problem (only it is magnetic
flux, not gas, that fills the gun) but more current can be pumped in
easily.  Coilguns don't have that problem, and should have very high
efficiencies.

I wonder how hard it would be to design a hydrogen gas gun in which
the gas is arc heated as in a railgun.  It wouldn't be too efficient,
but the major cost of launching is going to be capital costs, not
electricity costs, so it might be worth looking into.