Question

How effective would a thermonuclear device of 47 megatons or higher like the zsar bomba be in space?

Could we use as planetary defence on somthing like an asteroid as long as it is detected in time and what effect if any would it have on our planet and our satellites in orbit?

Answer 1

Have a look at impact.arc.nasa.gov/biblio.cfm for a comprehensive list of papers on the subject of asteroid deflection, or Google "deflecting asteroids site:nasa.gov" for a list of popular articles.

The summary of the Near Earth Orbit Program mentions the use of nuclear explosions, but makes it clear that a small device would be needed to prevent the asteroid from fracturing. A Tzar Bomba explosion would risk shattering the asteroid into bits, and even if all the bits missed the Earth this time round there is an excellent chance they would get us on the next orbit.

The favoured method seems to be laser ablation. If you shine a powerful laser at the asteroid you can boil off material from the surface, and the escaping gas will exert a force on the asteroid. This would be a very small force, but if you spot the asteroid far enough away it could divert the asteroid enough. See the NASA article for more info.

I seem to say this a lot, but the NASA site is a gold mine of useful information. If you want to research anything space related your first action should be to Google "whatever site:nasa.gov".