Rotating Space Tethers (Score:1)
by vincecate (741268) on Wednesday January 14, @01:28AM (#7970679)

The space elevator idea needs materials that we may not have for 50 years or more.

Rotating space tethers can be built today. They do not need anything stronger than Spectra-2000, which is used for fishing line. Even though we could really build these, space tethers don't get nearly the press that space elevators get. I think this is because the space elevator is simpler to understand.

A rotating space tether is long (like maybe 500 km long) with a weight at one end. It is rotating around its center of mass, which is close to the weighted end. The whole thing is in orbit around the Earth. It is spinning fast, like maybe 2.5 km/sec at the tip. The tip is going backwards relative to the orbital speed when it is down and forwards when it is up. So when it is down something can grab on even though it is not going at orbital speed.

Rotating space tethers can catch a payload from a reusable suborbital rocket and toss it into orbit. The reusable 1st stage of the SpaceX Falcon-1 could lift a payload high enough and fast enough for a practical tether to catch it. This could make for very cheap access to space.

Rotating tethers can recycle energy. If one tourist is coming down and another is going up there is no need to use an ion-drive or other thruster. This is a fantastic win. But even if you have to use a thruster it can be a high ISP thruster or you can even push on the Earth's magnetic field with an EDT.

Rotating space tethers can toss a payload every 100 minutes. A space elevator could easily take days to climb.

I have a Java applet that you can use to simulate space tethers at my site:

With this you can see how they work. In my unbiased opinion, this is the best way to get into space with current materials.

-- Vince