Moving an asteroid into Earth orbit

Count Iblis

Suppose we want to use an asteroid to build a large space station. We could alter the course of a asteroid so that it will come very close to Earth, but the velocity relative to Earth will then be more than the escape velocity of 11.2 km/s. Presumably we must use aerobraking to let it lose enough energy to be captured. But then this must be done such that perturbations by the Sun or Moon will then change the orbit so that it doesn't move inside the atmosphere anymore.

Can we capture a 10 km diameter asteroid this way?

DaveC426913

Yes. The real engineering question is: where will you house the 7 billion occupants while Earth is under construction?

(I'm not just being facetious, there's an underlying ... risk ... inherent in your proposal.)

D H

Absolutely! Jupiter captured several this way, all at once, in July 1994. The Earth captures several smallish asteroids this way frequently, and captured a larger one in 1908, and a very large one 65 million years ago.

The idea of aiming a 10 km asteroid at the Earth's atmosphere is rather foolish.

Perhaps using the Moon as a gravity slingshot might be a better idea. Perhaps.

tony873004

... If you consider an impact as a capture! :)
But Jupiter actually did capture SL-9 into an orbit probably about a century prior to impact. But as the impact illustrated, it was not a stable orbit. Likewise, using the moon as a slingshot can work. In fact it did, in 2006: http://www.orbitsimulator.com/cgi-bi...num=1182030550
But it was also an unstable orbit, and after completing a few orbits, our temporary moon escaped. So to capture and keep an asteroid in a stable orbit requires a large amount of delta-V on our part. You won't want to use the atmosphere, because you will broil the surface.
If we had the technology to produce the necessary delta V, then we would have the technology to mine the asteroid in its solar orbit, returning only the finished product to Earth.

EngineeredVision

I actually have an entire profession dedicated to asteroid wrangling in a science fiction story I'm developing. This profession plays an integral role in terraforming because it allows for large ice-laden objects in the outer systems to be brought to the inner terrestrial planets to deliver large quantities of water. In this case the asteroid wranglers actually want the captured body to strike the terraforming candidate. It’s been theorized that much of Earth’s water actually came to our planet in this way.

The second and more difficult function of the asteroid wranglers is to, as you suggest, capture a very large asteroid object and draw it into orbit around a terraforming candidate, essentially turning it into a small moon. This offers many benefits to the developing biosphere such as providing tides and stabilizing the planet’s rotation over time, thereby fostering more stable climate conditions.

Because there are inherent dangers with either of these operations they are only ever done on non-inhabited terraforming candidates.

Borek

In SF world military applications of such a profession seem to be promising

D H

Good luck with your writing. Stuff like this is fine for the domain of science fiction. I enjoy good science fiction -- so long as the science isn't too bad. Bad science fiction ([cough] Armageddon [/cough]) is a different story. Unfortunately, a lot of the lay (supposed) science fact writing on asteroid mining is in fact bad science fiction masquerading as lay science articles.

EngineeredVision

For the record, I don't like Armageddon or any of Michael Bay's films for that matter.

DaveC426913

Your guys think real long-term! Like hundreds of thousands of years...