# Comets, Asteroids and H bombs

I’d like to point to a frequent mistake made by many celebrity physics professors, who keep telling us this on the Discovery Channel,  National Geographic Channel and other broadcast channels.  It’s more ignorance than a mistake. Doesn’t really matter that many movie directors in Hollywood agree with them.

They say, God forbid smashing an incoming asteroid with a big nuclear bomb! That the parts of a broken asteroid are even more dangerous. That many more pieces will be  hitting us, better to leave it in one big chunk.

Well, this is baloney. Maybe if we decided to detonate very near our planet. In which case no method would work anyway. But if we destroy the asteroid far away from us, many years and many billion kilometers before the scheduled impact, then it poses no danger whatsoever.

The gravity center of the asteroid could still meet us here. But it will be an empty center made of  cold interplanetary vacuum from which all the pieces will have already escaped. This is called the Conservation of Momentum. It would be incredibly hard to keep a smaller piece of the exploded asteroid in the old orbit. Of the original rock merely a bunch of  spin off trajectories, less dangerous than the average asteroid would remain.

You can imagine the Halley comet splitting in to only two smaller parts because of an internal explosion. Let’s say that before the explosion, Haley is 10 years from smashing into Mars. The two orbits after dividing will both be very different from the old one. Neither one will hit Mars. The same holds for any number of parts an explosion could make.

Next time, just send a big H bomb toward the incoming comet! Don’t worry about small pieces, they will be million of miles away.

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## 5 thoughts on “Comets, Asteroids and H bombs”

1. A big comet, 10 kilometers wide, 30 years before the impact, would need 10 tons of TNT – not 10 kT, only 10 T! – to be pushed away from the collision course. This holds in quite ideal conditions of course, but never the less!

The same size comet 3 years away would need 100 times more explosive. It goes inversely with the square of time before the impact. A Hiroshima size bomb would be more than enough even for a dino-size comet one year away.

But please, use some MT devices, early in the game. Why to bother with small margins?

What if some debris will fly off the rock after the detonation of a Czar size bomb near the Halley? Those orbits, of those pebbles are almost certainly totally strange. No need to worry about them, they are just a small minority of all other flying rocks.

I think the questions here is: Do we have the technology to guide a (or better – a lot of) strong enough H-bomb(s) fast, precise and reliably enough for it to destroy a smaller comet/meteor or deflect a bigger one.

How much time and how much kT (or even MT) and precission do we really need?

You don’t want to guess here – You have to be reasonly sure (well, of course we’ll try if it comes to that, but You know what iI mean…)

• We have hit an asteroid with the car size object, already.

https://en.wikipedia.org/wiki/Deep_Impact_%28spacecraft%29

We have robot landed, too.

https://en.wikipedia.org/wiki/Hayabusa

We have plenty of rockets and a lot of bombs. Still, I would use at least 10 times more rockets than necessary. Wouldn’t mind to kick the dead horse some more in the case of a large comet intention coming down to Earth.

OTOH, it is very clear now, that one hundred or so mines, remotely controlled from here, on the surface of any small asteroid, would enable us to drive this rock through the Solar system. Popping a mine or two, waiting, popping again …

We could orbit them around the Earth, smash them to the Moon. It would take us a few decades or centuries maybe, but that’s nothing. The technology we already have.

3. Underweather says:

I think the main trouble with deciding to blow an asteroid up(esp with a nuclear bomb) is that before the event the orbit is kind of known, after the impact the result becomes totally unknown, a set of randomly moving new objects(a sum actually).

It’s in the human nature to fear the unknown, so the decision to or not “to bomb” may have some deep psychological roots, an action which turns the known into the unknown is usually not desirable.

But fundamentally I agree with your view. Nice blog, btw.