Re: [FT] Lasers

On 24 Sep 2002 at 11:30, laserlight@quixnet.net wrote:
> I'm looking for an article on realistic useful range for lasers in
> space...I remember something about focus problems making it difficult
to do
> much beyond X thousand kilometers but I don't recall the substance and
> evidently I'm not asking Google for the right key words.  Suggestions?

The range varies with the wavelength of the laser and the size of the 
focusing element. The range for a desired intensity of energy at the 
target is the  proportional to	diameter of focussing lens / 
wavelength of light.  

So you need a big lens and small wavelength (i.e. UV is better than 
visible, X-Ray is better than UV, etc.)

For reasonable SF figures of all the above you can get ranges of 
about 1000 km. Of course at that sort of range keeping your laser, 
with its big lens, on the target for any useful amount of time is 
another problem.

Anything better than that requires either
* the ability to produce lasers which use very short wavelengths (X-
Rays or even Gamma rays) or 
* stupidly big lenses, or 
* huge amounts of input energy most of which will be waste, or
* gravitational lensing (should be easy in any setting where anti-
/artificial gravity technology exists) or 
* some other change in the laws of physics.

	Steve
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Steve Pugh   <steve@pugh.net>	<http://steve.pugh.net/>