Ideas for a shuttle launcher

According to the all-knowing web, a nail gun uses one of (count 'em!) four mechanisms:

1. A spring
2. A solenoid
3. Compressed air
4. Combustion (wow!)

The solenoid idea attracts me, but how much energy do I need to impart to a shuttle.  The fastest nail-guns propel a nail 470 m/s.  Is that initial velocity?

A shuttle weighs about 5 g, and has a maximum initial velocity of 300 km/h, which is about 83 m/s.  

E0 = 0.5 * m * v^2 = 0.5 * 0.005 * 83 * 83 = 17 J

How much does a nail weigh?  Let's say we have a 5 cm nail, about 2 mm in diameter:

V = pi * 0.001 ^2 * 0.05 = 1.6 e-7 

If it's iron, that works out to a mass of 1.2 g, and:

E0 = 0.5 * 0.0012 * 470 * 470 = 136 J

That's almost 10x the energy release I need, so perhaps even a solenoid will do the trick (which is not quite at the top of the heap as far as nail guns are concerned).

Rail and coil guns