Meteorite shower over Chelyabinsk on February 15, 2013. Credit: Aleksandr Ivanov (via Creative Commons licence)

NASA is now working with the Department of Energy on possible ways of dealing with a short-notice asteroid strike. In a move reminiscent of Hollywood, the agencies may consider some genuinely nuclear options.

The partnership is between NASA and the National Nuclear Security Administration (NNSA), a Department of Energy Agency that works both to maintain the safety of the United States’ nuclear arsenal and to reduce the dangers posed from nuclear weapons by other countries and groups.

One of the NNSA’s key skills is maintaining safety and effectiveness with little or no practical testing, something that’s even more relevant when you start talking about nuclear weapons in space.

The agencies aren’t putting much effort into the Deep Impact/Armageddon style of asteroid that would wipe out the Earth. Instead they are concentrating on the more common risk of asteroids and comets between 50 and 150 meters. That’s a range where the object is large enough that the impact could be devastating in a populated region, but small enough that by the time they are spotted, there could be less than a year before impact.

The primary tactic to be explored through the partnership is using kinetic impactors, defined as “spacecraft interceptors launched on hypervelocity-impact trajectories.” In simplified terms, that means firing something into the asteroid to break it up, divert its course, or a combination of the two, the goal being to reduce the impact on Earth to less damaging levels.

There’s a limit to that strategy: the bigger the asteroid, the bigger the impactor needs to be, and at some point it becomes impractical. Using a nuclear weapon could be an alternative: not to “blow up” the asteroid as such, but rather to explode near to the object and create such heat that part of the surface vaporizes. That could change the size and mass of the asteroid enough to change its velocity and in turn its course.

One problem is that we don’t know enough about the make-up of asteroids to be certain how this would work; the effectiveness would likely vary depending on the makeup of the asteroid’s surface.

As for the more direct “fire a nuke right into the asteroid” approach, the problem is that the nuclear bomb would have to be travelling below a certain speed at impact to avoid destroying the fusing mechanism and thus disarming the bomb. Unfortunately that would be far too slow to allow the nuclear weapon to reach the object in time without a warning time in the decades.

Nuclear options aside, National Geographic quotes NASA’s David Morrison as saying the best short-term action would be to launch a space telescope that would take only five years to catalog all near-Earth objects. Such a project is in the development stage but would need around $500 million in funding.