Fraction of the cost of rockets

We already have the technology to send trains into space, at a fraction of the cost of rockets

This is Startram, a proposed launch system that would use magnetic levitation trains, a 1000-mile tunnel, and a superconducting cable to reach low Earth orbit. Amazingly, we already have the technology to do it...at far less than the cost of rockets.

Gizmag has a great overview of how Startram would work, but the basic idea is simple enough. Because maglev trains hover above their tracks and thus don't have to worry about friction, they are theoretically capable of going far beyond their current mark of about 350 miles per hour to reach the 20,000 miles per hour needed for orbital velocities. Of course, to safely accelerate humans to those speeds, you'd need a lot of track, not to mention a way to keep a hypersonic train from being ripped to shreds by the air around it. According to its engineers, a vacuum tube that's 1,000 miles long and simulates the lower air pressure of the mesosphere should do the trick.

While most of the tube would be at sea level, the exit point would need to be about 12 miles high. The same magnetic levitation technology used in the trains could also be used to suspend the tunnel that high in the air, as Gizmag explains:

If we arrange that there is a superconducting cable on the ground carrying 200 million amperes, and a superconducting cable in the launch tube carrying 20 million amperes, at an altitude of 20 km there will be a levitating force of about 4 tons per meter of cable length - more than enough to levitate the launch tube. The vacuum tube would be held down against excess levitation force by high strength tethers. Dyneema (UHMWPE) is more than strong enough for this purpose. Redundant design would make a failure of the levitation system most unlikely.

That may sound far-fetched, but its designers - James Powell, George Maise, and John Rather - point out that supporting a 12-mile cable would require only a fraction of the engineering knowhow needed to hold up the much longer tethers involved in a space elevator. The engineers propose building the system in polar regions like Alaska, northern Canada, Greenland, or Siberia, with the Antarctic ice sheet a particularly appealing candidate because it has no native lifeforms.

To build a passenger-carrying version of this Startram system, the team estimates it would take 20 years and $60 billion - which may sound like a lot, but when you consider it took almost three times that much to get the space shuttle off the ground, it's a steal. And once it's built, it would only cost $50 per kilogram to send things into orbit, compared to the current rates of $10,000 per kilogram for cargo and $100,000 per kilogram for people. That means a ticket to space would only cost about $5,000, and the designers estimate the accident rates would be on par with modern airliners.

As a final added bonus, Startram's ability to get tons of material into orbit on very short notice could make it our best defense system against any large objects headed our way, which the designers consider to be Startram's "most important application":

Today, we have no defense against asteroid or comet impacts. We probably would not even have a warning prior to impact. With present launch capabilities, this situation will not change. To really defend against impacts, we need a much more capable warning system, together with many large, high velocity interceptors that are pre-positioned in orbit and ready to go the moment an incoming threat is detected. This will require launching many tons of mass into orbit, something not possible with today's high cost launch systems.