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