Imagine a meteor, or a comet, tumbling its way thru our solar system, almost invisible against the darkness of space. A mass bigger than a mountain, moving at tens of thousands of kilometers for hour. Let’s say that this piece of rock is mainly composed by iron ore and silicates. Then imagine what kind of damage this meteor could do if its trajectory put it too near our planet.
Do you remeber the dinosaurus?
In the movies and in a great number of sci-fi novels the solution is clear. Hit that goddamned meteor, maybe with an atom bomb to be sure. The explosion will destroy it, doesn’t it? We will be safe until the coming of the next piece of rock, aren’t we? Well, it will not work. We will still be in danger.
Officially speaking, there are no weapons in Earth’s orbit. Even if they were, the missiles will be aimed at targets located on our planet. By the way, the entire project of such weapons will be devoted to hit enemies on the surface and such a design cannot be converted to hit high speed targets from outer space. So, if we want to hit an incoming meteor, assuming that we can spot it with enough time to act, we will have to launch some kind of multi-staged missile from Earth, having the last stage as an autonomous vehicle with enough fuel and onboard resources to hit the target. Even if such vehicle was available, our reaction time will be misurable in months. A pity that we don’t have anything ready by now. We don’t even have a working prototype.
The whole concept of hit-that-rock is quite arguable. The recent success of the ESA Rosetta mission demonstrate that we can handle complex trajectories in space and that we can manage high-precision approach to a fast moving object (in this mission, it was about the comet P67).
But what happen when you hit a meteor? And what do you use to smash a mountain-sized solid
object to pieces? Size matters. A small meteor can be shattered by a direct impact, without any explosive involved. Think about what could happen if two objects collide with a combined speed of tens of thousands kilometers for hour. The kinetic energy level is enough to crush such a meteor to small pieces. But said fragmentation will irregular, producing pieces of any size from pebbles to rocks big enough to survive the shock of atmosphere impact. A bigger meteor or comet will require a bigger effort to be smashed, with the same problem about the fragments multiplied for a factor tied to the size of the target. The more the fragments, the wider the area of the final impact and the bigger of collateral damages. Are we so sure that hit the meteor will be a great idea?
Again, it has been suggested to use a nuclear weapon to stop a meteor. The idea of a big flash in the sky and the consequent annihilation of the target may look perfect for a movie. Reality is different. It’s true, a nuke can obliterate large parts of the intended target and it’s also true that we haven’t a more powerful weapon to use against this kind of menace. The problem is about radiations and the cloud of high-radioactive fragments that will be the logic results of such
a bomb. The image of a billion hi-speed and hi-radioactive debris that reach our planet is a vision of doom.
So, how do you stop a meteor?