Laser weapons are getting closer to reality

[fiVe]

So, hypothetically, we could one day (maybe) be debating who makes the best laser--Surefire or Maglite?

 

[CMcDermott]

benEzra - the coherant nature of a laser means that it's power doesn't fall off porportionally to the square of the distance - the light stays together and spreads very little so it retains all of it's energy. On the moon, in orbit or on the next ridge over, the same laser would deliver the same amount of energy (except for what the atmosphere absorbs/reflects etc) to the target. A much bigger problem for a moon based laser would be getting it aimed precisely enough to be sure of what it was going to hit 400,000 kilometers away. Thats roughly 0.0000005 minutes of angle for an 8 inch target zone at that distance,

I can see a laser CIWS type system for ships, and a version for vehicles to protect against missles and shells. But you will still need the current bullet ammo systems for use in fog, rain, snow, dust/sand storms etc where the laser becomes useless. Current smoke screens wouldn't greatly reduce the laser since it works in the infrared region of light, and that goes through todays smokescreens fairly well. Of course the camaflauge people are already working on smoke that is opaque to infrared to hide from todays infrared goggles - and this new type of smokescreen will work against infra-red lasers as well.

 

[HankB]

if the mirror "armour" on your troops or tanks etc absords 10% of the laser and melts, that still means there's 90% of the laser reflected back at whoever fired it

Angle of reflection = angle of incidence, so unless the reflective surface is perfectly normal to the input beam the reflected ray will go off in some random direction. The way around this is to use some sort of retroreflector, such as a cube corner mirror or prism array. Of course, such an array wouldn't make for good camouflage . . .

Would a moon based giant laser be a sort of death star? Can it reach that far?

In principle, yes. The problem is, for maximum effectiveness, you want the beam waist at the target - that produces maximum energy density. Now, single mode lasers (the kind you want, for minimum beam spread) are basically gaussian beams, so if you want a small beam waist down around the Earth or in low earth orbit, you need a really BIG aperture on the moon, along with the appropriate beam-shaping optics. This is actually pretty easy to compute, not so easy to fabricate.

Aiming at a moving target on earth from the moon will be difficult - the time between observation, firing, and verification of a hit (or miss) would be around four seconds, even with things moving at the speed of light.