On Wed, 20 Aug 2003 22:23:45 -0500, David L Peterson wrote:
I jsut keep thinking of the old Jules Verne story where they mine a
shaft, hire masons to build a piller in the middle, have an army of
small foundrys all pour at once to create a giant cannon. Seems we
have the sort of technology to do that for real now. Maybe have giant
underground resivours that you fill with compressed air and a giant
dump gate. Or a giant version of my propane fired potato gun!
Seems you could get some pretty good initial velocity by the time the
thing would breach the surface. With all the experience we've had
tunneling I don't see why we couldn't build a giant underground
version of the kentucky rifle. and desing the pressure system to take
full advantage of the length. Just something I've thought about. I
havn't done the numbers, but I know that any initial speed means less
fuel needed onboard.

The projectile in the cannon barrel can't exceed the speed of sound
in the barrel. With normal propellants at temperatures and pressures
tolerable by any reasonable launch vehicle, you could only get about
2700 MPH (about 4,000 fps). You could do a bit better with staged
charges (ala Gerald Bull's Supergun).

But even 2700 MPH is too fast to slam a launcher into sea level
atmosphere. The launcher would still have to be mostly fuel tanks,
and they're rather fragile things. The muzzle would have to extend
about 8 miles up to make entry into the atmosphere at that speed
tolerable.

Now an 8 mile high cannon is a lot of work to only gain 2700 MPH
(you need a bit more than 18,000 MPH to reach low orbit). I don't
see it as being cost effective. Fuel is the smallest major expense
of launching a payload anyway.

Gary