# Capturing an asteroid in Earth orbit

1. Aug 31, 2009

### bhn1700

Yes I know someone else has posted something similar but I was wondering if capturing an 150 meter asteroid is possible in Earth orbit? Also can it be done by adjusting the delta v way out from Earth using the tug of a probe that you send to do such a job? (And maybe a final slow down with the moon when you get close.) And lastly can a 150 meter asteroid be captured into Earth orbit without it being torn apart given the 'rubble pile' nature that it will very likely have?
Thank you

2. Aug 31, 2009

### spacester

Big question. I'm guessing you're looking for a Space Elevator counterweight?

First off, you're almost certainly looking at a NEO (Near Earth Object), not a main-belt asteroid. Apollo, Aten and Amor asteroids are all good candidates.

Secondly, you would *apply* delta v in order to *adjust* the orbital velocity. Orbital transfers are typically done by applying propulsive force to initiate the transfer orbit, and then you coast until you reach the altitude of the orbit you're transferring to, at which point you apply delta V again in order to complete the velocity adjustment.

For an NEO, the delta V is quite modest. Of course, a 150 m object is very massive, so the *total* impulse is pretty darn huge. This is why a main belt rock seems to be out of the question, but an NEO would be possible. A major difficulty is that for a particular object, you might have to wait many years for the orbital timing to be right.

A typical burn-coast-burn transfer would need to find a way to apply that force without tearing the rubble pile apart. In my mind this would likely be the most challenging part of the enterprise. (Not counting the politics of getting approval to do such a thing.)

So maybe you would use the gentler continuous thrust method, most likely meaning that you would use ion engines (of a future design with more thrust than current engines). This would make it a lot easier to apply the force non-destructively.

I'm thinking the gravity gradient in a high Earth orbit is so small that tearing the rubble pile apart would not be an issue, but I've never played with the numbers on that, so I dunno.

All indications are that the stuff up there is a very diverse population in terms of these parameters. The first trick is to identify your target, note that not all of them are going to be rubble piles and you might find one that is a solid chunk of metal.

Hey I know - we should go take a look with a prospector craft.

HTH