[Barbshowers]

In space, the only medium the weapon has to work against is the asteroid itself, so for a thermonuclear bomb to be of any use against an asteroid, it would need to be inserted into it.

Agreed. Reminds me of "Armageddon." Although an approach similar to that one spacecraft (forgot the name) which was put in the path of a comet nucleus , should be used. However, to prevent premature detonation it would be a good idea to get its velocity within appreciable limits.

If the body of the nuke was similar to the UK-designed/US-improved version of the bomb that was designed to cause earthquakes for damage (name? Big Momma or something), that should help it with entry into the asteroid and cause sufficient damage.

Nukes wouldn't really deflect an asteroid because the release of energy is too sudden; a more effective solution is to detect an Earth-bound object early, and then attach thrusters to it, using long-term forces to manipulate its trajectory. Breaking off any parts, before or after it passes Earth, would be too risky as it would be almost impossible to determine what path they would take after detonation.

Agreed. Which is why we do that, but then destroy it after it passes us to the point it won't pose a risk. Any chunks can make it swing back to us the next time given it most certainly was affected by Earth's gravitational pull, and not just the Sun's. Or we can just readjust its trajectory to head directly into the sun.

Or rather direct it to Venus. It would be interesting to see that !