A while back I told you about some rogue asteroids whose threat
to Earth, while mathematically minuscule, is nonetheless real.
This raises the question of what our plan is for stopping
one of these dastardly asteroids if we need to.
It turns out, we have three.
In 2007, NASA presented the United States Congress with 3 ways
to save the world from an asteroid on a collision course with Earth.
Each plan has its upsides and its downsides, but together they cover
pretty much every doomsday scenario Hollywood could dream up.
The first plan proposes using a "slow push"
a strategy that involves sending a spacecraft to a threatening
asteroid and then messing with it to alter its orbit.
For example, one of these methods, called ablation, would use
a huge mirror to focus sunlight on a small spot on the asteroid.
The heat generated from the beam would vaporize material
on the surface, creating a jet of gas and debris
with just enough force to divert the asteroid's path.
Another plan calls for sending a spacecraft that's so massive
that it would serve as a gravity tractor.
By flying a supermassive vehicle alongside an asteroid,
gravity could pull the space rock out of the way.
But the "slow push" scenario that
experts like the most is called the space tug.
In this version, a craft attaches itself to the asteroid and fires
its propulsion systems to nudge the rock onto a different course.
All very elegantly simple, no?
Actually, no.
The problem with "slow push" plans is that they all involve
inventing tricked-out new spacecraft and having them rendezvous
with a rock millions of miles away.
That's a lot of logistics.
Combine that with the fact that these techniques would
only work on rocks less than 300 meters across,
and it's time to look for Plan B.
So, what about brute force?
I mean, we're trying to destroy a rock here
so let's not over think it.
That's where the second plan comes in: kinetic impact.
NASA has actually described this as "the most mature approach,"
but the whole idea of it turns me into an instant seven-year-old.
You just get a Delta IV rocket and saddle it up with
a high-density impactor, say a huge hunk of depleted uranium.
Then aim it away from your face and toward the asteroid and KABLAMMO!
It would be awesome!
But again, there are problems.
Kinetic impacts are only effective on smaller, solid objects,
and some of the bad guys out there roaming around are basically
several square kilometers of rubble held together by gravity.
An impact could potentially just turn them into many,
many little asteroids instead of one big one.
So that leaves us with only one other option.
And you may know what I'm talking about here: the Nuclear Option.
NASA physicists say it would take just a small megaton
neutron bomb to divert the path of even a large asteroid.
In computer models, they found that the nuclear option was
100 times more effective at deflecting asteroids
of all sizes than any of the non-nuclear options.
So there's our solution!
But, obviously, there are some drawbacks here.
First of all, experts point out that you can't just
launch some leftover warhead, you need a specialized nuclear device
on a heavy lift launch vehicle,
and the ability to time the explosion precisely.
And even though the explosion would be most effective
if it took place on the asteroid's surface, or even inside of it,
the official recommendation is to do a standoff explosion,
detonating the bomb during a flyby.
This cuts the risk of blasting the asteroid into a bunch
of radioactive fragments hurtling toward Earth,
which would not be ideal.
But finally there's this little snag:
The international Comprehensive Test Ban Treaty prohibits
nuclear explosions in space, even for scientific research.
So a plan like this would require
international cooperation and approval.
Now, hopefully, the prospect of all our lives turning into
some bad '90s disaster movie would be enough to get
the nations of Earth to work together on this.
But, let's just say I hope we never need to find out.
Thanks for watching this episode of SciShow.
Again, I hope that we never need to use any of this information.
But it's good that we have it anyway.
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