RE: Nanotech Arms Race

Billy Brown (
Mon, 25 Jan 1999 12:47:20 -0600 wrote:
> I was talking about nuclear energy in the more general sense;
> not neccesarily controlled use. Personally I find the idea of a mosquito
> flying through my window carrying a multi-ton-yield fusion bomb rather
> scary than a nanobot running off a miniature nuclear reactor. People had
> previously assumed that any hostile nanobot would be limited to chemical
> levels rather than nuclear..

Ah. I see your point.

I think, however, that we are still safe. There are some formidable problems with nano-scale (or even micro-scale) nuclear devices, and they seem to be more a matter of fundamental physics than simple engineering constrains.

First, there is a size requirement for the fuel. A fusion reaction releases most of its energy in the form of hard x-rays, which are then absorbed by the rest of the fuel, which produces the heat that sustains the chain reaction. If you make the device too small the x-rays aren't captured, and you can't produce a chain reaction. Even with nanotech, its hard to see how you could make a device less than a few inches in diameter without this problem being fatal.

Second, there is a power storage problem. Current bomb designs use a small fission bomb to produce the energy that starts their fusion reaction. A laser ignition system would need a similar amount of power, but it has to get it from a non-nuclear source. That means you need a capacitor system much bigger than the bomb itself - and we've already seen that the bomb has a minimum size.

Third, as you noted, there is a diminishing yield problem. Even nuclear weapons only produce so much bang per pound, and if you start measuring the bomb size in micrograms it gets pretty puny. A robot mosquito might carry as much punch as a truck bomb, if you could make a bomb that small - but that's no big deal with reasonably advanced nanotech. Anything much smaller than that won't even produce an explosion - it will simply produce a flash of radiation when it detonates.

Billy Brown, MCSE+I