The Aerie
Not so long ago I wrote a blog entry about Japan's Hayabusa probe, which attempted to land on an asteroid, sample it, and return to Earth. This probe ran into some trouble, but ground control seems to be getting a grip on things and may be able to resume operations. The fact that this mission can even possibly recover from such a serious problem is a testament to the skill and engineering genius behind its design and operation.
But my concern voiced last November has not been addressed. The world needs to consider what it will mean when we can routinely land robotic probes on asteroids. An article posted on Space.com today explores one idea, which is to use such asteroids to deflect other asteroids.
French scientists want to land a robotic probe on an asteroid and maneuver it out to a Lagrange point, one of the locations in space where the pull of the Earth is balanced by the pull of the sun, so that something placed there will follow the Earth in its orbit without a lot of perturbation. Then if a threat is detected, Lagrange asteroids could be moved into position to shatter or deflect the threatening body.
The author (and presumably the French) see this idea as the possible solution to the infinitesimal threat of an asteroid striking the Earth during our particular sliver of the historical record. What nobody seems to see is that it's much more likely that the ability to maneuver an asteroid would be used to imperil the Earth, rather than save it.
We're at the bottom of a very deep well, and people are talking about sending robots up out of the well to start shoving rocks around. How long until somebody tries getting a robot to shove one of those rocks INTO the well where we are all standing?
The next arms race could be a Japanese or French robot guiding a rock into a precision de-orbit over anyplace. The next arms race could be every space-capable or nearly-capable country launching robots to seize control of the nearest asteroids, lest somone else do so.
I don't have any answers, but all these excited "triumph of science" articles seem to be overlooking this dangerous possibility. Given that the US treats its space program like the redheaded bastard child, we could find ourselves in a very vulnerable position. It's not too much to imagine China, Japan, Russia, even France, having the capability to launch robotic probes to nearby asteroids, and then positioning them to threaten anyplace on Earth.
Even the United States.
In a world that emphasizes the flashiest weapons, it would be good to remember that the first weapons were probably rocks. And dropped from outer space, rocks would be even more deadly than a penny dropped off the Empire State Building... and a lot more likely than a natural asteroid hitting the Earth anytime during this historical epoch.
Posted by Albatross at June 20, 2006 11:38 AM | TrackBackForget about malicious intent--what happens if, during the process, there's an "oops." Bye-bye earth. Ah, but we all know our machines never malfunction... malfunction... malfunction...
At this time, however, I don't think space rocks as weapons constitute much of a threat -- do you know how much energy it would take to move any large-sized asteroid anywhere, let alone position it at a Lagrange Point? Even if they got it started, it would probably take years for it to reach its destination.
The other issue is this: Let's say someone wants to use it as a weapon. "Aiming" a big rock like that would be tricky at best.
The energy needed to move an asteroid can be minimized by trading for time. If you're willing to wait, it doesn't take a lot of energy to change an asteroid's course in the vacuum of space. And if something is already bound for the vicinity of Earth, it doesn't take a lot to alter that course.
For reaction mass, the French scientists postulate scooping up the asteroid's surface and flinging it into space. This assumes an asteroid surfaced with something other than solid rock, of course. Then you can leverage solar energy to run a motor to steadily fling asteroid mass into space.
Precision aiming is of course a big challenge - but that's exactly what the Japanese plan to do with their Hayabusa probe. It's return has to be just as precise to be successful. So that technology is not entirely out of the question.
Posted by: Albatross at June 20, 2006 4:22 PM