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Air Bags for Planetary Defense
Gallowglass writes "The Canadian paper, the National Post, is reporting on a plan to divert asteroids headed towards Earth. According to the story, the proposer, a Dr. Hermann Burchard, suggests deploying an inflatable mylar bag a few kilometers in size, and using it to push the projectile aside. An air bag for earth? The deployment mechanism isn't detailed in the story."
...shows that smaller asteroids may experience neck injuries or even death from the fast deploying air-bags.
I think the idea would be to make some attempt to match it's speed, then contact and start the engines firing to push it off course.
Rather than think of it like a car's air bag, think about it as a way to spread out the pressure along the surface of the object. A rocket on the surface of a comet or loosely bound asteroid may just disintegrate the parts, yielding little benefit.
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This is the wrong problem, in my opion; he assumes you've got massive amount of rocket fuel to wast. What we really need to do is figure out how to take some of the mass of the asteroid and accelerate it, using this as the reactant to change the path. Sort of like installing a rail gun on the asteroid, and firing off bits of asteriod like b-b's to get the asteroid to move in the opposite direction.
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Thank you for your contribution. Now please prepare a report on why, exactly, incoming asteroids would be hot enough to glow. Be prepared to show whether or not that will be relevant at the time that the plastic hits the asteroid.
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Answer: Airbags for Planetary Defence
I once did some back-of-the-envelope calculations about deflecting asteroids with a physicist friend of mine.
Our presumed target was a 1 mile dinosaur killer that is about to hit Earth in a few months and we want to impart enough kinetic energy to change its trajectory so that by the time it reaches Earth it will miss it by a few thousand miles of safety margin.
Well, it turns out that it takes so much energy that even the biggest thermonuclear devices barely have enough energy to do it, even assuming we could convert it efficiently to kinetic energy.
A nuke going off in space is just a big flash. No real blast. You need some working mass to convert it to kinetic energy. Using the mass of the asteroid itself is dangerous because you don't want it to break into multiple fragments.
Here our calculations probably become much less accurate because we took some shortcuts and made some assumptions that may be way off, but the result we got is that we needed to send some tens of thousands of tonnes of working mass (e.g. water) along with the nuke to convert its energy to momentum with reasonable efficiency.
Needless to say, this is beyond our current launching capabilities.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
suggests deploying an inflatable mylar bag a few kilometers in size, and using it to push the projectile aside
No, what we should do is build a giant pool-cue stick and knock another asteroid into the first asteroid, deflecting it into the side pocket.
And exactly how do they intend on getting a giant steering wheel into space?
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