Tilting at Asteroids

JimPooley writes "The European Space Agency are conducting a feasibility study into a future mission to knock an asteroid off course. A Spanish company are planning the 'Don Quixote' mission to launch a pair of spacecraft at an asteroid. One hits the asteroid, while the other monitors it to see what happens."

Cheaper, easier and

[PhysicsGenius]

more accurate to paint them white [spacedaily.com] and let the sun do the work.

Same Thing we do Every Night

[medcalf]

Hidalgo and Sancho? Is anyone else humming "Mouse of La Mancha"?

Costs of Asteroid diversion

[geoswan]

Oh yeah, some slashdotters were suggesting that if we were going to go to the trouble of diverting an asteroid, like 2002 NT7, so it didn't hit us, why didn't we go all the way, and divert it enough to capture it in a useful low earth orbit?

The simple answer is that would be a cost a lot more energy. 2002 NT7 would have hit Earth with a velocity of 28 km per second. Earth's escape velocity is 11 km per second. To divert it so it wouldn't hit earth required changing its velocity by something like 28 centimeters per second. Capturing it in LEO would require changing its velocity by close to 28 kilometers per second.

Those velocities differ by a factor of 10^5.

Now maybe my Physics is really rusty, but the formula for kinetic energy is one half mass times the square of the velocity. So, unless my physics is rusty, the energy to capture 2002 NT7 would be 10^10 times greater than just diverting it.

If we really needed a big pile of rock in LEO wouldn't we be better off just quarrying the moon?