Posted on 02/23/2013 10:02:55 AM PST by SunkenCiv
Explanation: How would you change the course of an Earth-threatening asteroid? One possibility - a massive spacecraft that uses gravity as a towline - is illustrated in this artist's vision of a gravitational tractor in action. In the hypothetical scenario worked out in 2005 by Edward Lu and Stanley Love at NASA's Johnson Space Center, a 20 ton nuclear-electric spacecraft tows a 200 meter diameter asteroid by simply hovering near the asteroid. The spacecraft's ion drive thrusters are canted away from the surface. Their slight but steady thrust would gradually and predictably alter the course of the tug and asteroid, coupled by their mutual gravitational attraction. While it sounds like the stuff of science fiction, ion drives do power existing spacecraft. One advantage of using a gravitational tractor is that it would work regardless of the asteroid's structure. Given sufficient warning and time, a gravitational tractor could deflect the path of an asteroid known to be on a collision course enough to miss planet Earth.
(Excerpt) Read more at 129.164.179.22 ...
[Illustration Credit & Copyright: Dan Durda (FIAAA, B612 Foundation)]
This is a technique that would (less effectively) alter the trajectory of an asteroid in order to keep it from hitting the Earth. Like other methods, it would only work if enough lead time were available, meaning, for our own defense, we need to have a comprehensive detection grid up and running ASAP. The only thing to recommend this gravitational tractor would be if the asteroid were rotating, as most of them probably are -- rotation would make it more difficult to attach a plasma engine that would point in one direction.
|
This is a technique that would (less effectively) alter the trajectory of an asteroid in order to keep it from hitting the Earth. Like other methods, it would only work if enough lead time were available, meaning, for our own defense, we need to have a comprehensive detection grid up and running ASAP. The only thing to recommend this gravitational tractor would be if the asteroid were rotating, as most of them probably are -- rotation would make it more difficult to attach a plasma engine that would point in one direction.
|
The orbit of the asteroid would have to be known to a LOT of decimal places...a tiny error at the orbit of Jupiter would result in a BIG ERROR on Earth. Of course, this could also be used as a weapon...a really good one, too, because by the time it got close anything you could think of to deter it would be about as effective as an umbrella.
I was thinking about the rotation problem the other night while watching a show about this sort of thing and noticed they never talk about the fact that they’re tumbling through space.
To me that leads me to think that maybe some sort of mass driver or low thrust propulsion might be better because they would only push when the asteroid is oriented correctly.
OTOH a large enough gravitational tractor parked at the right distance could probably overcome the complex moving gravitational field of the asteroid.
It wouldn’t be as efficient, but it *might* be more practical. The problem with it is, the propulsion would have to be not strong enough to break away from the grav, while being strong enough to maintain a steady distance and steady tug on the rock. IOW, it would require a very long time frame to work, and experience teaches that we simply won’t have that long a time frame in which to work.
IMHO, it makes much more sense to take small asteroids moving retrograde, attach these long-working motors to them, and keep them handy for threat annihilation. We’d need some large but available number of them (or we could park them at the Lagrange points), and thread the needle with just one. A single head-on impact by a small one would basically obliterate both our projectile and the interloper. Problem solved.
Well, Bruce Willis can relax. No Armageddon for us! Cool.
Given enough time we can move planets.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.