A potential weapon of war?
posted at 9:20 pm on May 28, 2011 by Steven Den Beste
This is the next step in a minor debate with Instapundit. This response is quite long, so I figured I’d post it here instead of mailing it to him.
It’s been said that a lot of great ideas can be killed off just by running the numbers. So let’s run a few, shall we? The question is whether a steerable 13 terawatt beam can be used as a weapon. A lot of that depends on how wide the beam is when it reaches the planet. So let’s try some examples, and see what kind of power density you’d get, OK? Just to make sure everyone is on the same page, a "terawatt" is a trillion watts. 13 terawatts is 13,000,000,000,000 watts.
If the beam is half a kilometer squared (250,000 square meters), then the power density is 52 million watts per square meter.
If the beam is a square kilometer (a million square meters), then it’s 13 million watts per square meter.
If the beam is 100 square kilometers (a hundred million square meters), then it’s 130,000 watts per square meter.
And if the beam is 100 square kilometers, then the system is impractical because the receiving stations would be infeasible.
My microwave oven has an internal area of about a quarter of a square meter, and it’s 1100 watts. It does a really good job of cooking food, and if anything alive was put in there, it wouldn’t survive long. That’s a power density of about 4000 watts per square meter (rounded). The 100 square kilometer beam described above would have about 30 times that power density. The quarter square kilometer one would have 13,000 times the power density.
Well, on the old O’Neill/JPL solar power satellite studies, the beam density was very low — low enough that birds could fly over the receiver without being harmed. But that plan involved satellites in geosynchronous orbit. I don’t know if it applies to lunar power-beaming.
The location doesn’t matter. What does matter is that those studies assumed power generation on the order of hundreds of megawatts. This hypothetical 13 terawatt beam is 4 orders of magnitude stronger.