Previous studies have investigated the use of magnets to accelerate satellites to the high speeds required for launch. But most have focused on straight tracks, which have to gather speed in one quick burst. Supplying the huge spike of energy needed for this method has proven difficult. The advantage of a circular track is that the satellite can be gradually accelerated over a period of several hours.

The tunnel would direct the cone to a ramp angled at 30° to the horizon, where the cone would launch towards space at about 8 kilometres per second, or more than 23 times the speed of sound. A rocket at the back end of the cone would be used to adjust its trajectory and place it in a proper orbit.

Anything launched in this way would have to be able to survive enormous accelerations — more than 2000 times the acceleration due to gravity (2000g). This would seem to be an obstacle for launching things like communications satellites, but Fiske points out that the US military uses electronics in laser-guided artillery, which survive being fired out of guns at up to 20,000g. […]

A cone-shaped shell would protect the payload during its passage through the atmosphere into space, and includes a rocket at the back end to adjust its trajectory (Illustration: J Fiske/LaunchPoint Technologies)

If the ring launched hundreds of satellites a year, it would be cheaper than conventional rocket launches. With 300 launches per year, the team estimates the ring could put payloads into orbit for $745 per kilogram. If the launch rate reached 3000 launches per year, they calculate that would drop to $189 per kilogram. Today, it costs more than 100 times that to send payloads into space.

A ring of superconducting magnets fires a projectile off a ramp at 8 kilometres per second, fast enough to reach orbit (Artist’s conception: J Fiske/LaunchPoint)
Although Epstein is sceptical about the prospects for such a ring, he cautions that if built, the ring itself could become a target for attacks. This is because of its potential for use as a weapon, launching missiles that could reach anywhere in the world. “The ring then becomes one of the most important targets on the planet,” he told New Scientist.
http://www.newscientistspace.com/article/dn10180-huge-launch-ring-to-fling-satellites-into-orbit.html