I’ve been watching episodes of a TV show called Salvation on Netflix, which is basically the story of a desperate attempt to save Earth from an extinction level NEO ( Near Earth Object ) — aka asteroid — impact.
In the final episode of series 2, after everything else has gone wrong already, the main protagonist of the story ( Darius Tanz ) is trying to explain to The White House the dangers of fragmenting the asteroid by using nukes — ie: a last resort effort to save the planet — being that it just turns one large impact into many large impacts, and has a greater chance of wiping out all life ( as there’s no longer anywhere to hide ).
I suddenly realised that there is a correct way to use nukes to defend the planet …
Okay, so here’s the thing … the problem with using nukes to destroy an asteroid, is that most of the explosive force is just directed uselessly out into space, as there’s nothing to contain it, so no matter how big the nuke, all you’re likely to do is crack the asteroid like an egg, you have zero chance of vaporising it, leaving a worse situation where multiple large impacts occur at different locations, instead of only a single larger impact … both are bad situations, but multiple impacts is far worse, where the initial NEO mass was so large, that dividing it into several smaller objects doesn’t actually help, because they’re all individually worthy of being called extinction level impactors.
So clearly we need the object to miss the planet entirely.
Now in the TV show they develop a solar sail and rail gun, as means to divert the trajectory of the NEO, and while both of these and other ideas ( of which I also have a few ) are perfectly valid — but they’re technically challenging solutions to the problem — and the ideal solution is one where less can go wrong, because such objects travel at an extreme velocity, and you really don’t have very long to react once you know it’s on the way, and possibly only one shot at getting it right … but there is a solution, and the show made me realise what it is ( in terms of using the nukes ).
Ironically, the solution is that we need the nukes to miss the object — think about it:
- Calculate the trajectories;
- Fire the nukes in series to create explosions offset to the incoming NEO trajectory;
- Each explosion produces a shockwave, not enough to fracture the asteroid, but enough to nudge its path slightly …
… I mean the math and the timing would be difficult, but actually way easier than other things we’ve already achieved — the only real question is whether or not you can get them to have an escape velocity great enough to nudge the asteroid early enough to miss the planet.
BUT — the point being — IF it’s possible to do it with nukes, THEN this is how it would be possible ( as opposed to trying to blow it up ).
I do think that better long term solutions exist versus trying to use nukes, because the downside is you’re potentially creating a subsequent orbital rain of nuclear radiation, and I don’t know enough about how the Earth’s magnetosphere may or may not protect us from such blow-back … and I certainly loved the idea in the TV show about the massive rail gun.
My favourite solution is actually one involving some very specially designed satellites, which serve the dual purpose of providing clean energy, but that’s a story for another day.