[TML] Solution to the near-c rock question

[Anthony Jackson]

shadow at shadowgard.com wrote:

> 
> You want a miss by a lot more than 2600 km.

Yeah, you kind of want a 2.5 m/s shove.
> 
> Also giving a body big enough to worry about 1 m/s of delta-v isn't 
> something we can pull ooff with current tech.

Yeah it is. Surface ablation with nuclear weapons will do the trick. For 
that matter, drilling a hole in it and blowing it up will cause most of 
the fragments to miss Earth, as long as you do it a while out. If you 
take a 1 kilometer rock with a mass of 2 gigatons and detonate a 100 
kiloton nuke in it, that works out to an energy of 210 kilojoules per 
kilogram. If 1% of that energy gets turned into kinetic energy of the 
fragments, the average expansion velocity perpendicular to its impact 
path is 53 m/s, and if you make sure to detonate the weapon a bit off 
center, you'll also get an off center expansion, which should cut the 
mass down even more. You'll still get a few megatons of incoming rock, 
which isn't helpful, but you can probably create a donut hole in the 
rock cloud with an additional nuke or two, and chunks below a certain 
size aren't a threat anyway.
> 
> For that matter, it'd take us years to build something that *could* 
> intercept it "a month out". Much less do so while carrying something 
> that would give the required delta-v.

Now this is certainly true.