Re: Drag an asteroid back to earth..
The reason why is to prove the concept that asteroids can be snared and moved into orbit around the moon, where they will be much closer to Earth and can be used to harvest water which can be used to make rocket fuel for use on a mission to Mars. It would make a Mars mission much cheaper and easier. Given the large quantities of rocket fuel required for a mission to deep space it would be extremely difficult and prohibitively expensive to get enough fuel off of Earth and into orbit for use by a spacecraft. It costs millions of dollars to put one ton of cargo into orbit, and tens of thousands of tons of fuel would be needed. If you can make that fuel with materials harvested from an asteroid it would save a 100+ billion dollars off the cost of a mission to Mars. You make rocket fuel by splitting water molecules into hydrogen and oxygen molecules. Even a fairly small asteroid could hold enough frozen water to fuel Mars missions.
99% of all asteroids are millions of miles from Earth and it would take years just to get to them, which makes the raw materials they hold far too expensive too harvest for use on space missions. By dragging the asteroid closer to Earth you save time and money and you use less fuel travelling back and forth, which means you have more fuel for the Mars mission.
When it comes to deflecting an asteroid that threatens to crash into Earth, you really only need to deflect it a tiny amount to make it sail off into space instead of hitting the planet. The earlier we deflect it the less of a nudge that will be required. If the asteroid is millions of miles away we would only be required to nudge it a tiny fraction of one degree off course to make it miss the planet. Given that the asteroid will be traveling at 20,000mph or faster we would need to detect it long before it gets close to the planet. It would have to be detected weeks or months in advance so we could launch a spacecraft to intercept and deflect the asteroid while it is millions of miles out in space. At that distance from Earth, even a tiny explosion or a small booster rocket would suffice to deflect the asteroid enough to make it miss.
Last edited by AtomicDumpling; 04-08-2013 at 12:02 AM.