> suddenly your concentrated 1GW beam is pointing at an apartment building. Wait ... have you calculated the antenna size required to produce a beam able to pi

> suddenly your concentrated 1GW beam is pointing at an apartment building. Wait ... have you calculated the antenna size required to produce a beam able to pick out an apartment building, at microwave wavelengths, from orbital heights? Consider the distances and the available microwave frequencies, and you'll see that you cannot get a beam narrow enough to resolve an apartment building from orbital heights, with any reasonable dish size. Remember that, at sufficient distances, all antennas become cosine emitters with no ability to concentrate their energy in a specific location. This is true for lasers, x-ray emitters and it's certainly true for microwave emitters. My point is that a practical system such as we're discussing must have a large receiving array to accommodate the beam size at ground level. It's not going to be anything resembling a death ray.