Don't Be Subtle, Nuke That Asteroid

Quotes from the linked story:

"Firstly, what if the resulting explosion rips the asteroid to shreds, but big chunks of asteroid then rain down on Earth, blanket bombing entire continents? Choosing whether to get hit by one big asteroid or a shower of smaller (but still rather big) asteroid chunks isn't a choice I'd want to make."

Personally, I wouldn't want you in a position to make that choice! I'll explain why as we go...

I submit that fracturing an asteroid has advantages. When you fracture an object you increase its surface area. This has a huge advantage for reentry friction due to the Earth's atmosphere. It is far easier to disintegrate a small object than a very large one.

Multiple small objects stand a very good chance of either disintegrating or being reduced in magnitude if they do strike. The Earth's atmosphere has the potential to absorb a huge amount of energy from an asteroid if the asteroid can be fractured into small enough components.

Secondly, a fracture may very well propel a significant amount of that mass off of the direct hit trajectory.

Third, a multiple nuclear hit strategy could be employed with follow up shots to further fracture remaining large objects should it be needed.

"Secondly, what if the USA fired a missile at a medium-sized asteroid, only to deflect it into China? Wars have started over much less."

I would not use the possibility of failure as an excuse for not trying our best to avert the problem. That doesn't mean that we ignore failure modes, but you can only minimize failure, never remove its possibility completely.

"Thirdly, we don't have a very good understanding about the structure of asteroids. An asteroid composed of very loose rock held together under a mutual gravity (a "rubble pile") will act very differently to a solid, metallic asteroid when faced with a huge explosion. President Obama's plan to send NASA astronauts to an asteroid to study it up close suddenly seems like a good idea."

I think understanding the enemy is essential. I am not convinced that scrapping all our planned manned missions and suddenly pulling Bruce Willis out of retirement is sane.

I think if you want to understand asteroids we can do it cheaper, faster, and more effectively with robotic missions. When we get to a point where a robot isn't good enough, then a manned mission may be in the cards.

As the writer admits, there are different types of asteroids. So, how many manned missions will you need to cover our bases? Would that be as economical as robotic missions?

I would rather save our manned missions for Mars, where the return volume of scientific information and discovery would be much higher than some barren rock that may not be representative of the fate we face. I think Obama is smoking hope with his plan. It shows ignorance and a lack of leadership.

"Also, a recent study showed that a direct hit by a nuclear weapon might rip the offending asteroid apart, but it could re-form if the bomb wasn't big enough."

The best reason to use a nuclear warhead is because there is little or no time to do anything else that may be better. A fractured asteroid is not going to reconstitute itself in a matter of weeks or even months.

If we have that much time, we should be able to explore other alternatives that have a higher probability of success.

"So what is it to be? Do we use nuclear weapons? Or do we find more subtle ways to deflect asteroids?"

That question shows no forethought. We do both! We want as many arrows in our quiver as we can afford. The more robust our toolbox, the more likely we have a viable solution when it is needed.

Additionally, some tools work better than others depending on circumstances. It would be folly to limit ourselves to only one response. This isn't a 'this or that' question.

"Unfortunately, it is highly unlikely there will be a "live" nuclear test in space, so it is doubtful we'll know the true impact of a nuclear asteroid strike."

This is true, but we are already talking about reduction in nuclear arsenals and many of our warheads are getting past their "Best if Used by" date. Maybe a test or two would not be a bad idea after we have done out theoretical predictive homework first.

However, this article seems intent on just raising objections to their use in the first place and the objections are not very cerebral at that. I don't think that we should just roll over if faced with a potential asteroid strike. Rather, we should employ everything at our disposal to insure our species survival.