Nukes Not the Best Way To Stop Asteroids, Says Apollo Astronaut

MajorTom writes "Right now, we are not tracking many of the asteroids that could destroy earth. But within the next decade, new telescopes will make that possible, and leave us with the tough decision of what to do about objects with an alarming chance of hitting our planet. Last year, NASA said that the best option is to nuke them. This week, Apollo astronaut Rusty Schweickart, explained that there are far better options, and he has started an organization to prove that they can work."

Comments

Re:I always wondered

[MSZ]

Detonate one of them near the asteroid, push it off course

You can rain nukes on that asteroid till it glows, but that won't make much difference. Trick is, in the vacuum of space, nuclear explosion is weak. There is no air to create blast wave and thermal flash, so all you get is some hard radiation and hand-grenade level of blast from vaporized bomb casing. And that's it.

Project Orion would get around this problem by using thousands of little charges, detonated close to the reflector - and it would still take years to accelerate.

A volley of the kind of nuclear warheads we have now would not effectively change course of any asteroid big enough to be a threat.

And blasting it to pieces would make a little difference, only in distribution of the damage - we'd get stoned with a swarm of fragments instead of one big piece, yet the same mass and total energy.

Re:The reason for nukes

[Chairboy]

You appear to misunderstand:
1. How much power is needed to apply an appropriate vector to the Significant (capital S is appropriate) mass.
2. The method used to propagate the blast energy into the asteroid.

The first item depends on the size of the asteroid, but the killers are usually pretty big, and need a big push. The amount of push depends on where in the orbit you find it, of course.

The second item is basically this: You can't rely on the atmosphere to transmit a 'shockwave' to the asteroid. In a vacuum, the actual shockwave is negligible once you get too far away (inverse square) and even up close, is only comprised of the limited mass of the bomb. Again, negligible effect. The actual propulsion comes from mass ejected by the asteroid itself. What would compel said mass to depart fast enough to create a thrust vector? Why, how about the sudden massive heating of one side? With a hydrogen bomb, you get the energy needed. For devices in the 15-20KT range, you're talking atomics, and the amount of usable energy that can be imparted is reduced significantly.

So the job of the bomb is not so much to "blow the asteroid off course", it is to convert the asteroid into a rock-rocket that fires molten asteroilava in one direction to create a vector for the larger mass in another.

Re:I always wondered

[NockPoint]

And blasting it into little pieces would most certainly have an effect, since smaller pieces have more drag, they would be more likely to burn up harmlessly in the atmosphere (same total energy, much wider dispersion).

For a small object, yes.

For a object big enough to seriously worry about, no. Think of it this way. Take a rock the size of the one that killed the dinosaurs. It had roughly 300 million nuclear weapons worth of energy. Break it into a million equal size pieces, and there are a million rocks with 300 times the energy of a nuclear weapon, each of which would be more than large enough to punch through the atmosphere. The damage would be more focused on the surface of the Earth, and less would be "wasted" on deep layers of rock.

Small explosions are much more effective at destroying things than large explosions. That's why cluster bombs were invented.