Zenith Star

[Forest Green]

Cause a 500 kilowatt beam of a few centermeters can do the same damage as a 3 meter 5 megawattter due to putting more energy in less space.

That's why shorter wavelengths are better (assuming they're at an atmospheric window) because the optics don't have to be as large to focus the beam.

 

[Scott Kenny]

But how much precision would be needed to ensure the beam hits the right spot? RVs are moving fast and could have last-second maneuvering. Wouldn’t that make consistently hitting a vulnerable section tricky, even with modern tracking?

The idea is to hit the missiles before they release RVs to begin with, but RVs don't do a lot of jinking until they hit atmosphere. Just some relatively small adjustments of the entire bus to make sure they're released on the proper course to land where they're wanted.

That's why shorter wavelengths are better (assuming they're at an atmospheric window) because the optics don't have to be as large to focus the beam.

Larger optics are better for handling the thermal load, though, and also give you a lot more range.

The two major determinants of laser effective range are laser wavelength (the smaller the better, near-UV or even UV-C is far better than mid-IR) and targeting mirror diameter (the larger the better).

 

[Forest Green]

You also have to bear in mind the atmospheric window though. Near UV suffers higher absorbtion than 1,000nm.

 

[Scott Kenny]

You also have to bear in mind the atmospheric window though. Near UV suffers higher absorbtion than 1,000nm.

True, but 1200nm results in ~100km effective range of a laser before spot size growth plus pointing errors exceeds target size (for a 1m diameter target and 1m diameter pointing mirror!)

200nm on the other hand results in a ~1800km effective range under same conditions.