[Madidus_Scientia]

I was thinking that a series of bombs designed to penetrate might dig a deeper hole than one big bomb

[Bored chemist]

"If we're supposing multiple projectiles then they would have to impact almost simultaneously."
Why?
One a week would work fine, you just need to give them a guidance system that will navigate for the last part of the trip without help from earth.

"Yeah, what about a series of bunker buster style missles ahead of the nuclear charge, it would take precision to make them all hit the same crater though"
Just tell all but the first one to aim for the hottest bit.

[Edster]

Project Orion?
 the bomb or bombs have a fuel pellet deployed between them and the object to be moved. The plastics used in the hydrogen bomb in the compression phase seem to be good contenders as they are efficient in absorbing neutron flux and rapidly expanding when superheated into plasma.

You could erect a reflective "lightsail" on the object and use the radiation pressure from a nuclear detonation, but that would be a lot less effective.
Alternatively if caught early you could use the light from the sun to steer it away with a sail.

[Fluid_thinker]

well it sounds like we are all buggered until someone finds the anti gravity particle and a way in which we can harness it into a laser like ray gun and then we simply point it at the comet/asteroid and it falls apart.

there,, problem solved

[lyner]

I did have one but the wheels dropped off.

[Madidus_Scientia]

What if we get Chuck Norris to death-stare it, that'll stop it

[Fluid_thinker]

Just go an have a Phall curry from my local curry house, than bend over and aim the next morning.