Gravitational Tug
 The original "Star Trek" television series debuted on September 8, 1966, with the USS Enterprise taking viewers on journeys across the galaxy. Some present-day astronauts have devised a Trek-like plan for diverting any asteroids that might threaten Earth.
LU: The idea that we had is to simply hover a spacecraft nearby. [:05]
That's Ed Lu, who devised the concept with fellow astronaut Stan Love. It's called a gravitational tractor. Lu says that with enough warning time, it could gently pull an asteroid away from a collision course with Earth.
LU: The asteriod has gravity, and it will pull the spacecraft towards it with a very slight force -- it's a very weak force of gravity, but that weak force is, in effect, your towline. The engines of the spacecraft keep it from falling towards the asteriod, so what it essentially is doing is towing the asteroid -- instead of having a towline or a rope, you have this force of gravity. The advantage is that you don't really need to know ahead of time exactly what the asteriod is made of, what the shape is, what its rotation rate is, and so on and so forth. This thing only requires that the asteriod has gravity, which all asteriods do. So in that sense, it's kind of guaranteed to work. [:44]
Lu says that in some cases, the spacecraft wouldn't need to be any bigger or more complicated than today's communications satellites. In other words, you wouldn't need a fancy starship to protect Earth from a cosmic collision -- just time and patience.
Script by Damond Benningfield, Copyright 2006
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