sick--sick

Sorry. I don't buy this. I still think that the gravity tug is the most simple solution that we know will work whether the asteroid is tumbling or not.

But if it's not tumbling (rare, I would think) this would work.

... this irregular thrust will send him on an incalculable curve. Maybe the curve will be large enough for him to miss Earth, but maybe not.

coat the asteroid with something highly reflective, and it becomes a solar sail (albeit one with very high sail loading). If the original surface was strongly absorbing, the monentum transfer due to solar radiation should be nearly doubled. I find it hard to imagine the Yarkovsky effect being anywhere near as large in magnitude.

http://en.wikipedia.org/wiki/Radiation_pressure

The beauty of it is that rotation of the asteroid is not a problem - in fact, it's what makes the scheme work! You coat the entire asteroid, and this either increases of decreases the tiny thrust from IR photons regardless of orientation.

It does seem, however, that the change in photon pressure associated with the coating would be the larger effect. But I think they act in different directions. Radiation pressure would give a force that is directed radially outward from the sun, while the Yarkovsky effect yields a thrust that acts in a direction almost mutually perpendicular to the axis of rotation and the direction toward the sun.

I wonder how sensitive this technique would be to changes in the asteroid's rotation? And how stable that rotation might be over the long time scales required for this to work?