The Millennial Project:
The second stage of Marshall T. Savages book, Millennial Project, Bifrost, will be the shining bridge into space, a 21st Century Launch System, replacing the wasteful rocket launches practiced today.
The "Project" proposes building a 250 kilometer long, hyperbolic tunnel drilled into a mountain and the surrounding countryside. Ideally the mountain would be near the equator for better launch conditions and even less necessary force (objects located at the equator already have a greater angular velocity than those further away), making the launch even cheaper. Mt. Kilimanjaro is given as a good candidate.
Inside the tunnel, a shuttle, called the wave-rider would be accelerated with superconducting rings in the walls, just like MagLev Trains. The largest part of the necessary exit velocity would be provided on the this ramp through magnetism. The shape of the wave-rider would ideally be a delta wing, an excellent glider able to coast on its own shockwave. For the rest of the way to orbit, it would only need about 4 tons of fuel, which would be Ice.
Ice? Yup, frozen water, fired upon by ground based lasers powered by the Aquarius colonies. These lasers will vaporize the ice on the rear of the launch vehicle, giving it the final boost into space. No more rocket fuel, no more wasted rockets, just ice and electricity. Neat, huh? Incidentally, the light of the lasers is the bridge to the heavens, thus the name Bifrost.
This "bridge into space" will be able to deliver payloads into orbit cheaper than anything we have now. When a kilogram of payload onboard a Space Shuttle would cost about $8800, Bifrost will be cheap, as low as $15 to $20 per kilogram over the long term, according to Savage.
Sounds too good to be true? Well, Savage's plan has one little problem: He figured in using this system to deliver humans into space, but up to now there is no way that humans or any organic object would survive a launch that exerts from 10 up to 255 Gees upon the body. But for payloads, the system is sound...
Once a cheap way to deliver materials into space has been set up, the next step can be begun in earnest: Building a permanent habitat in Earth's orbit, Asgard.
A nice picture of how Bifrost could look like is at http://oceania.org/images/plate5.jpg
The Millenial Project: Aquarius, Bifrost, Asgard, Avalon, Elysium, Solaria, Galactica and Foundation