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From: "Andrew Higgins" <>
Newsgroups: sci.physics,sci.physics.electromag,,
Subject: Re: Orbital cannons (was: Re: Gerald Bull)
Date: Sun, 13 Feb 2000 03:36:08 GMT

Bill Bonde <> wrote in message
> Allen Thomson wrote:
> >
> > In article <>,
> > Henry Spencer <> wrote:
> >
> > >
> > >Many gun/catapult schemes run into a fundamental difficulty:  it's
> > >hard to fire something out of the atmosphere with enough horizontal
> > >velocity that it only needs one rocket kick stage,
> > >
> >
> > An excellent point that needs to be FAQified for those who are
> > learning about launchers: most of the velocity an ordinary satellite
> > launcher needs to attain is *horizontal* (parallel to the ground).
> > Going up is only needed to get out of the draggy air. Getting into
> > orbit needs 7500 m/sec of horizontal velocity; just getting above the
> > sensible atmosphere isn't nearly as hard, as witness the bigger
> > sounding rockets, which don't put anything into orbit but do reach
> > orbital altitudes.
> > 
> > There are various somewhat academic exceptions and qualifications to
> > the above, but it's good enough to start with.
> >
> Balloon floats up to 135,000 feet or as close to the edge of the
> sensible atmosphere as possible. Attached cannon fires projectile up a
> bit and horizontal. Shaped charge on projectile explodes sending
> sub-projectile payload into orbit. If you don't think this quite gets
> the velocity there, than a sub-sub-projectile is used.

A shaped charge is easily capable of launching a projectile to
orbital velocity.  Conventional shaped charges have jet velocities
of 10 km/s, and I have seen some recent Russian work on ceramic-
lined cylindrical shaped charges with velocities up to 12 km/s,
with potential theoretical velocities from using alumina or boron
nitride of 20 - 30 km/s.

Unfortunately, there are no good ideas for making a useful satellite
out of a jet of liquid metal (or ceramic).  These are very useful
devices, however, for simulating orbital debris and micrometeoroid
impacts on real satellites.
   Andrew J. Higgins            Department of Mechanical Eng.
   Assistant Professor          McGill University
   Shock Wave Physics Group     Montreal, Quebec CANADA

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