You don't want a natal chart for that. That'd just tell you where everything was at the time it was erm born and therefore give some insight into it's erm personality.
You could use horary astrology to effectively produce a natal chart of the birth of the idea of dropping a bomb to see what the outcome of such an action might be.
But your best bet would be electional astrology which is used to identify the best time to do something. You could do that using either by using the natal chart of the bomb or of the plan of dropping it to see when the heavens are particularly beneficial to that kind of thing, or you could do what would effectively be a magic(k)al election based on the perceived attributes of the bomb/bombing (mostly martial/saturnine I expect).
I'd not bother myself - beyond the benefits of boggling the mind with complex calculations and deep contemplation of the planetary model, astrology really is a crock :imo:
Magic(k)ally speaking, if you'd identified by election a particularly good occasion for some sort of ... oh I dunno .... summoning of something particularly malefic or something, then I suppose setting off a nuke might not be a bad offering. I don't personally subscribe to the plot theory of history, let alone a magic(k)al plot theory but it's an interesting thought.