Mass drivers as spaceship launchers

>
> > - and if rocketry is too expensive, go around it.
>

Agreed. While a coilgun would be practical to go all the way to
escape velocity on the moon, Earth's atmosphere prevents the same
use here. However, if maglev or a coilgun can get it going to say
half the speed of sound, that is a lot of kinetic energy for which
your rocket does not need to carry fuel. Any savings on fuel is
carried over several times due to the rocket equation.

If you can build a maglev or coilgun on a high mountain near the
equator, launching your rocket from the "muzzle" at say Mach 0.7 and
12000 feet, you've got a huge savings on fuel. If the horizontal
acceleration is one gee, your gun needs to be less than three
kilometers long.

This is the same idea used by Scaled Composites and a number of
other X-prize contenders: light the candle when you've already got
some speed and altitude. The big difference with a coilgun or
maglev is that the entire first stage, and all of its energy supply,
stays on the ground, possibly to be reused within hours or minutes.

And then there's always the the other bypass to consider, the space
elevator....

Ed

Ah, the space elevator also has been called the space hook. That
would be the ideal way to get things into LEO or really close - take the
elevator. I think at 40 miles up your steel on the lower floors would
get sticky (molten). Such a building would take decades of international
steel production to even start thinking about. Sounds more like fiction
as apposed to a real idea, but if I remember correctly in brainstorming
you don't eliminate ideas. I read a book once about some kind of tether
between earth and perhaps the moon - it either guided or the craft
pulled itself down this cable. I wondered at one time if something that
was in orbit could lower a line down to the surface and that something
could climb it or be winched up it. Fanciful I know, but if you wanted
to move everyone off this planet you would just not have enough rockets
to go 'round.

The way I read the 40 mile long magnetic vacuum rifle - the
cargo was levitated magnetically the entire length of the barrel. I say
barrel and rifle because it has a lot more in common with a SciFi weapon
than an accepted way to fire things off planet. Someone should try to
get the military to back it as a weapon program seeing as their budget
is substantially larger than what NASA ever will get. Mt. Kilimanjaro
was sited at a good site, as was Mt. Fuji, but I suppose any mountain
would do. The main idea of any new form of spacelift is to leave as much
of the launcher on the ground as is physically possible. Any idea that
does that is better than the 'bombs with a hole knocked out' we
currently strap people to, cross our fingers, and launch into orbit.

- Ted