[X] My Assistant

[nprev]

Here's a Christmas present for us all...a 0.7 km NEO may make a 4200 km altitude Earth flyby on Halloween, 2041: http://neo.jpl.nasa.gov/risk/2006xg1.html

[tty]

You definitely do NOT want to use any violent technique that might break an impactor up into small fragments. Remember that according to recent research the main killing mechanism of the Chicxulub impact was the vast cloud of dust-sized secondaries that deposited enough energy in the stratosphere to cause wordwide fires and fry unprotected organisms.

That, paradoxically, is one reason I think using nuclear charges would be safer than a series of "deep impacts". The shock wave from a directed-energy nuclear weapon set off some distance from an impactor would act more or less in parallell and equally on all parts of it and therefore run less risk of breaking up an "orbiting rubble pile".

Safest of all (but very slow) is of course "gravity tugs", which apply an equal force on each atom of an impactor.

tty

[ugordan]

That, paradoxically, is one reason I think using nuclear charges would be safer than a series of "deep impacts". The shock wave from a directed-energy nuclear weapon set off some distance from an impactor would act more or less in parallell and equally on all parts of it and therefore run less risk of breaking up an "orbiting rubble pile".

Except that would be a very cost ineffective way to divert an object. Probably wouldn't work, either. Some 80% percent of the energy released by a nuclear weapon is soft x-rays, the rest being mostly kinetic energy of the fragments. Were you to arrange detonation some distance away from the object, the surface area of the expanding debris that did useful work would diminish rapidly. In essence you'd waste a large fraction of the bomb's yield on nothing. It's arguable that the fragments would push upon the object with any significance when they hit. Let's say you set the bomb off so 10% of the spherical debris cloud impacted the object - a fairly close burst. Given a warhead in the (conservative) range of 1 ton, that's 100 kg of material pushing on a kilometer or so sized object. Even given the high nucleus speeds (something like thousands of km/s) that wouldn't do much. The fragments would still deliver a shock to the object, the front being parallel wouldn't help much. As for the bulk of the energy released - the x-rays, I imagine they'd be rapidly absorbed by the first couple of millimeters of surface regolith which would explosively flash into steam, generating some impulse thrust and producing a shock wave on its own in the object, in advance of the much slower fragment debris cloud that is yet to arrive. The x-ray generated shock wave shape wouldn't be dependant on whether the bomb went off near or far -- what angle the x-rays were absorbed wouldn't matter as the material would blow-off vertically to the surface at that point. There's really no easy way to convert the sudden release of many megatons into a gentle push.
A nuclear charge would basically only be good at destroying an object and we don't want that. Moving the detonation point away from the object will rapidly diminish your return, if any.

BTW, what's a directed-energy nuclear weapon?