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Should Nuclear Devices Be Kept On Hand To Protect Against Near Earth Objects?
Lasrick writes: Seth Baum ponders whether nuclear devices should be kept on hand for the purpose of destroying near-Earth objects (NEOs) that pose a threat to the planet. Baum acknowledges that "The risk posed by NEOs is not zero, but it is small relative to the risk posed by nuclear weapons." Even so, Baum writes, since the consequences of an NEO hitting the earth would be catastrophic, keeping 10 or 20 nuclear devices available might be a good idea, and would be "insignificant compared to the thousands now held in military arsenals."
The summary is wrong. TFA says the nuke would be for changing the trajectory of the NEO, not destroy the NEO. It also found nukes to be better than other methods of changing trajectories.
The actual thermal effect of a nuclear weapon in the atmosphere is almost exclusively due to the fact that there is an atmosphere. In the immediate milliseconds following fission you get a very intense burst of soft x-rays, these are in turn absorbed in the first 2 miles or so of the atmosphere, superheating its component gases and causing it to radiate white, IR, and UV light. FUMP. This emitted IR/UV/White is the intensity that causes flash fires, vaporization, deflagration, etc.
In a vacuum, a nuke goes off like a _very_ short flash bulb followed by a rapidly expanding cloud of _very_ whispy very superheated plasma that is composed of the nuke's fomer mass - only. What you don't see however is that the intense surge of X-rays does not get captured by anything, and instead continue on, rather lethally for hundreds to thousands of kilometers.
A nuke against a NEO would best be used well ahead of time, in close proximity of 5 to .2 kilometers depending on the item's composition. Upon detonation the x-ray burst would get captured by the first few centimeters of the objects surface material facing the nuke. Material would boil off to several mm of depth, almost explosively for a few fractions of a second, and deliver a soft shove to the object conversely away from its boiled off char.