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Message: <blockquote data-quote="stealthflanker" data-source="post: 243460" data-attributes="member: 4204">So, what determine the beamwidth (Half angle width or whatever it called) Of this new laser ?For "old" Laser such as ABL..Mirror diameter and laser wavelength determines the beamwidth along with diffraction limit (1.2) .. One can calculate the beamwidth  (in Micro radian unit)  by dividing that wavelength (micron) with mirror diameter (meter) then multiply the result with 1.2 to take account of diffraction.After knowing the beamwidth one can roughly estimate beam radius (How big the hole made by the laser) by multiplying that beamwidth converted to radian with range in meters, from there beam area can be estimated by simple circle area.After knowing beam area, we can estimate how much power of the laser reach the target, this require laser power, beam area and a coefficient of material absorbance (Say aluminum absorb only 5% radiation at 1.3 micron laser wavelength).Anyway i make simple excel spreadsheet for that purpose :3http://www.mediafire.com/view/r25cdq2f6xkokra/LaserCalc.xlsx The spreadsheet however discount the atmosphere absorbption and any beam broadening effect produced by atmosphere.. So this sheet might not be satisfactory for calculating ground based laser. But i see it can give more accuracy for higher altitude (say tropopause to up to the space)</blockquote>

Verification: What year did the first man go to space? (answer has 4 numbers)