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

TFS

[mpeg4codec]

To save you all the horror and pain of reading TFA (since TFS doesn't state), Schweickart is suggesting we either push or pull them away with unmanned spacecraft.

Re:TFS

[AKAImBatman]

I hope you realize that Pournelle and Niven didn't just make that up? Project Orion was a very real attempt to develop nuclear pulse propulsion. It is still a viable option for space travel, as long we're not talking about a ground-launch using nuclear pulses. To get the sucker into orbit, we might have to resort to something a bit more mundane. Like a dozen SRBs or somesuch.

The reason for nukes

[Chairboy]

Nukes have been a popular options because:
1. We have them.
2. They have a high ISP (a measure of efficiency) when used as propulsion against a large object. Paradoxically, the ISP for Orion-style nuke propulsion increases with the size/mass of the object.
3. They're much more portable compared to most other types of methods.

Schweikart has identified the REALLY valuable truth, that we need to improve our detection method. We also need to develop deep space capability because the further out we can intercept them, the less energy is needed to perform the deflection. Lower energy can also mean less danger of fracturing the mass.

Re:The reason for nukes

[burdock]

Redirecting an asteroid on an Earth impacting trajectory was discussed in depth quite a few years ago in Scientific American magazine. There are a variety of ways to deal with such an asteroid, depending on size, composition, and how advanced the warning is.

There are two main responses: redirection and pulverization. If the asteroid is structurally week and small it can be pulverized so that the pieces will burn up on atmospheric entry. This has the advantage that it can be done with little advance warning. One novel proposal involved a 3 dimensional mesh built around tungsten nodes. It would be compact for launch yet still spread out and stay grouped together for a long distance strike.

Redirection is necessary for large or durable asteroids. Spin would make it difficult to have a vehicle in contact with it redirect it over time. Reliable redirection would require delivery of multiple kinetic payloads over time. Each payload strike would have the danger of fracturing the asteroid; widening the potential Earth-impact damage.

Focused, reflected, solar energy has been proposed to redirect ice based asteroids with much advanced warning. Even X-ray cannons have be proposed, along with other laser based solutions. A thermonuclear device ignited adjacent to an asteroid would vaporize a layer off its exposed surface, redirecting the asteroid. This would even be effective against iron-ore asteroids. There is also less likelihood of fracture than kinetic impact. Close asteroids can be acted upon multiple times for faster redirection.

A nuclear solution has the advantages of being effective at long range and at ranges to close for the other listed methods to be effective. It is less likely to cause fracturing and would work against any material composition.

Reliable long range detection would allow other methods to be effective, but thermonuclear warheads are a mature technology, would be effective at short range and we do not have to station them in space ahead of use.

Re:I always wondered

[mosb1000]

A nuclear warhead intended to deflect an asteroid could be designed to penetrate the asteroid prior to detonation. Blasting away debris from the surface of the asteroid would allow you to "push" it effictively.

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). Also none of the resulting pieces are likely to have exactly the same trajectory as the original asteroid. Depending on the angle of impact, they will be moving at a different speed or in a different direction than the original.

Re:I always wondered

[Sibko]

Oh man, oh man. I'm literally facepalming right now. Facepalming SO HARD.

Nuclear explosions follow the inverse square law. The further you are from the source, the less radiation is hitting you. Nuclear weapons on Earth derive most of their destructive power from the shockwave they create in our atmosphere. However, they are still incredibly powerful reactions, and if you're close to one in space, it will still fry you.

Project Orion would not 'take years to accelerate.' Unless you meant to add 'to a tenth the speed of light' at the end of that sentence. As it stands, Project Orion is the fastest, most practical spaceship would could design and build today. Chemical rockets don't even come close to what Project Orion is capable of.

And the Orion doesn't have a 'reflector', it has a pusher plate. It's a heavy metal plate, on the end of a gigantic shock absorber, coated in oil or similar [To reduce ablation.] that absorbs the energy from the nuclear explosion so that everyone on board the ship doesn't get splattered by the intense acceleration. The ship is ultimately pushed by a plasma wave created by the explosion.

An asteroid would be no different. Except that the surface might vaporize and act as additional reaction mass. The biggest problem I can envision with using a nuke to propel an asteroid is the difficulty you might have in predicting its new course.

That would take a lot of delta-V

[Beryllium Sphere(tm)]

Making it miss is a matter of nudging its orbit just enough that it doesn't intersect Earth any more. Capturing it requires slowing it down all the way to Earth-orbit speed. In space, just because something goes nearby doesn't mean it's easy to catch.