space mirrors are perfect as weapons, with ALL of the details worked out in various sci fi, and of course a late soviet experiment that showed the ability to turn night into day for a far northern siberian town without frying anybody, as the device did have focusing capability that they were able to use without any accident, that we know of, and any other testing that may still be secret. of course the ultra cheap defence against this or any space based weapons system is rockets that make orbit with 50tons of crushed rock and gunpowder as a payload, and just render leo as a satelite shredder zone for the next 25 years, and there are very few countrys that could not do this on short notice, so play nice everybody as the endless rationalisations for better nastier weapons will run up against ,as the french say " the argument that ends all discussion"