The old joke that the dinosaurs went extinct because we didn’t have a space program may have overstated the need for one. The products of our nuclear weapons program alone might be enough to divert some of the more threatening asteroids. But it probably wouldn’t work the way you think.
Nuclear weapons are obviously very destructive. But why not asteroids? Asteroids would be impossible to destroy, since most of the damage they cause comes from the blast wave propagating through the atmosphere. Also, the environment around an asteroid has a very thin atmosphere, so a blast wave would not occur. However, it would be possible to use the radiation of a nuclear weapon to vaporize part of the asteroid’s surface, creating a very temporary, very hot atmosphere on one side of the asteroid. This could create enough pressure to deflect the asteroid, potentially sending it safely past Earth.
But will it work? Scientists at Sandia National Laboratories decided to tackle a really cool problem with one of the coolest pieces of hardware on the planet. Z Machinecan produce X-ray pulses bright enough to vaporize rock, and they estimate that a nuclear weapon could deliver enough force to deflect an asteroid about 4 kilometers in diameter.
No nuclear weapons! (Nuclear simulations only)
The Z Machine is the heart of Sandia’s Z Pulsed Power facility. It’s essentially a mechanism that stores and releases huge amounts of electrical energy, up to 22 megajoules, almost instantly. Anything in the immediate vicinity is exposed to a very powerful electromagnetic field. In particular, the machine can be used to strongly ionize materials, such as the argon gas used here, to produce powerful x-rays, which act as a substitute for the radiation produced by nuclear weapons.
For the asteroids, the researchers used disks of quartz or fused silica rock. (It’s worth noting that they only took one sample of each, but got fairly consistent results.) A normal person might have just attached the disk to a device that could record the forces it was subjected to and called it a day. But these scientists were more stubborn, and decided that this wouldn’t really replicate the experience of an asteroid floating freely in space.
To recreate this, the researchers used a thin foil to hold a disk of rock in place. When the X-ray burst arrived, the foil evaporated almost instantly, leaving the rock suspended in the air for a period of time. Gravity would still be at work, but the radiation-induced phenomenon that evaporated much of the rock was over before the sample could significantly accelerate downwards. The rock’s movement during this time, and therefore the forces exerted on it by the evaporation of its surface, were tracked by a laser interferometer placed on the side of the disk furthest from the X-ray source.
Now that everything is ready, all that’s left to do is fire up the Z-machine and vaporize the rocks.
