Let’s say we’re having a nice day here on Earth; the Sun is shining, the clouds are sparse, and everything is just looking like a peach:
And then Lucas goes and tells me,
Oh my God, Ethan! It’s Armageddon! An asteroid is coming straight for us! You’ve got to stop it!
Really? Me? Well, how would I do it? Let’s say we’ve got some reasonably good asteroid tracking going on, and we’ve got about 2 months before the asteroid is actually going to hit us. We’d like to do something with the situation on the left, to avoid the situation on the right:
Well, what we really have to do is change the asteroid’s trajectory by a little bit, so that instead of hitting us, it flies-by Earth without ever colliding with us.
This means making a teeny-tiny change in the velocity of the asteroid; we just have to give it a little push. How little? If we can get to the asteroid with a month left, just five miles per hour. If we can get there immediately, with two months left, only 2.5 mph. That’s a pretty small number! But how can we do it?
Asteroids are huge, massive things. The one that came close to us recently, 433 Eros, has a mass of 6 x 1015 kg, or about 100,000 times as massive as Mount Everest! Sure, we might only have to change its speed by a small amount, but how do you do it for something that massive???
Well, we’ve got to smack something into it with enough momentum to change its course by a large enough amount. That means we need something moving with enough speed and enough mass to smack into that asteroid hard enough to make it change course.
Well, we can build rockets with masses up to about 1,000 tonnes, and they typically have payloads of up to about 20 tonnes. (The payload is the part that can get launched into deep space.) We would have to launch that rocket at nearly the speed of light to change the course of that asteroid! NOT COOL!
If we really wanted to stop the asteroid, we’ve got two realistic, and very expensive options:
- Make a rocket massive enough to do the job. How massive would this be? About 100,000 times as massive as the Atlas V rocket shown above. And realistically, that’s how much it would take. This assumes that we can make it fly at typical rocket speeds with perfect control over its trajectory. This will also require about 100,000 times more rocket fuel than we’ve ever used before.
- Load a regular rocket with the largest multi-phase Thermonuclear Bomb ever made, just for this purpose. If we can take a 20-tonne payload and make the majority of it out of fusionable Hydrogen (which can be fused into Helium) that’s 10% efficient, we can get about 5 x 1017 Joules of energy out.
If we blow up the bomb on impact with the asteroid, half of this energy will go into changing its velocity. If we hit it at the right angle and in the right spot, we can change its velocity by up to about 20 miles-per-hour, or just enough to change its course and have it miss Earth.
And that’s my solution to this problem, with the second one being far more feasible and less expensive. Are we going to be serious about protecting the Earth from catastrophic asteroids? If we are, this is the way to do it. And just like all the greatest sci-fi movies ever, this is the scientist cautioning you:
If this device should fall into the wrong hands…