Relatavistic Impactors : would the craters be radioactive?

[EzinX]

Suppose a group of beings with advanced technology decided to bombard earth. Rather than using fission/fusion bombs, they use a mass driver so long and powerful that the projectiles exiting it travel at 0.99c . The projectiles are iron slugs.

Since any object made of matter traveling above 86% of the speed of light has more energy than the equivalent mass in antimatter, how would this terrible energy be expressed upon impact? Would it cause spontaneous fusion or fission between the matter it impacts? Would the neutrons released cause enough neutron activation to be significant?

To throw in some numbers, each projectile has 100 megatons of kinetic energy relative to the earth.

[Scotius]

https://what-if.xkcd.com/1/

I guess that means yes. There would be a lot of radioactivity - not that it would matter to anyone anymore.

[sndrtj]

That suggests the iron slugs wouldn't get much further than the upper atmosphere. Interesting thought.

[rodion]

i think what you would basically get in that situation is the equivalent of a short-lived omnidirectional particle collider beam, with a gamma ray burst followed immediately by any matter around the impact site being packed with enough energy to ignite a whole chain of exotic particle interactions. you wouldn't just get radioactive events, you'd get a whole zoo of particle and nuclear physics events, many of which humanity would likely have never been able to observe before (or ever again). what it would do to ground zero in the medium or long term i can hardly imagine but i think it's fair to assume there would be unstable radioactive species amongst the debris.

[EzinX]

That suggests the iron slugs wouldn't get much further than the upper atmosphere. Interesting thought.

Presumably you could adjust the slug speeds so that time dilation keeps them cohesive until they reach the lower atmosphere.

[EdFred]

Presumably you could adjust the slug speeds so that time dilation keeps them cohesive until they reach the lower atmosphere.

I don't think time dilation has anything to do with it. The slugs would get eaten away by the air molecules just like the baseball. The solution is larger slugs.

[EzinX]

I don't think time dilation has anything to do with it. The slugs would get eaten away by the air molecules just like the baseball. The solution is larger slugs.

From the slug's reference frame, their encounters with the air molecules take the same amount of time as always to resolve, converting the slugs to gas and then probably subatomic particles.

But from the earth's reference frame, the slugs take longer to break up.

[sndrtj]

From the slug's reference frame, their encounters with the air molecules take the same amount of time as always to resolve, converting the slugs to gas and then probably subatomic particles.

But from the earth's reference frame, the slugs take longer to break up.

That also means the ball, from Earth's reference frame, can interact (because interaction takes time from the ball's reference frame!) with air molecules only at a slower rate.

[Tommygun]

I think the Tunguska event might be a good starting point to imagine what would happen.

It has been estimated to have release around 15 Megatons of energy.

It can't be confirmed, but there were a number of unusual deaths that were similar to radiation exposure, electromagnetic pulse like anomalies and reports of compass not working for a time.

I think it would be completely vaporized in the air almost instantly and hitting the ground wouldn't really matter.

In fact, air bursting weapons do more damage over a larger area.

I'm guessing the fusion reaction would be cleaner than what you would see with a fusion bomb.

You might even want to look at the Tsar Bomba atomic test that air burst a weapon of up to 58 megatons.

Edit: I wonder if making the slugs out of cobalt would make any difference in the fallout?

Edited December 9, 2014 by Tommygun