Lasers are basically worthless

Lasers are basically worthless Because of divergence, effective laser power decreases brutally with distance (constant divergence angle => inverse square falloff). With higher frequencies, you get lower divergence, but unfortunately, higher frequencies are hard to generate and in many ways are less damaging (though that's way beyond scope). Since the engagement envelope is measured in tens/hundreds kilometers, your laser basically needs to be a thousand, a million, or a billion times as powerful, just to do the same amount of damage at range. Example: A diffraction-limited 532nm green laser with a 2mm aperture has a minimum beam divergence of 0.085 milliradians. This corresponds to a factor of 23 million billion reduction in flux density over the mere 1.3 light-second distance from Earth to the Moon. So the whole thing about light-speed lag playing a role in laser targeting is garbage, because your city-sized 22-terawatt death-star-laser literally looks like a laser pointer at a distance of 1 light-minute. Oh sure, you can do a lot better by increasing the aperture (at inverse square again, but thankfully not scaling with distance). And, in fact, any even remotely practical laser weapons system operates with huge apertures and a lens or mirror to move the beam waist towards the target (all of which are vulnerable themselves)--but you're still going to play a losing battle with diffraction, and CoaDE correctly shows a depressingly abrupt asymptotic drop to zero with distance. But the even larger problem is the heat generated. A laser outputs only a tiny portion of its power as coherent light. The rest is dumped as heat, which goes into radiators. To radiate a literal power-plant's worth of thermal energy into space requires several square kilometers of radiator. That makes you a huge, immobile, sitting duck that still can't defend itself because lasers are worthless. Example: A space station with an enormous 1 GW ultraviolet laser was disarmed easily, at range, by a lone gun skiff with a 3mm railgun, firing in the general direction of the radiators. The point is it's not worth it. Enemies can't dodge anyway, so you might as well use something that actually retains all its destructive power at range and doesn't produce an obscene amount of waste-heat. The only case I've found for lasers is blinding (but again, not really damaging) drones and missiles.