Re: A Study into the Use of Laser Retroreflectors on a Small Satellite - M.Unwin
At 6:30 PM -0500 7/24/01, Jim Choate wrote: And these are reasonably low power lasers... http://www.ee.surrey.ac.uk/SSC/IJSSE/issue1/unwin/unwin.html The simple fact is that the thermodynamic impact of a laser beam that is several feet across and emitting more photons than the surface of the sun will not be easy to reflect unless immense cooling is taken. Cost/weight factors alone argue it in the negative. More photons than the surface of the sun for HOW LONG? A minute? A second? A millisecond? A microsecond? You confuse fluence with flux, a classic mistake. (A pulse brighter than the sun but lasting only milliseconds will have far less heating effect than other flux level pulses lasting longer. Calculations matter. And, yes, I used to do these calculations when I was refuting Kosta Tsipis' calculations of the late 70s. Fluence matters.) --Tim May -- Timothy C. May [EMAIL PROTECTED]Corralitos, California Political: Co-founder Cypherpunks/crypto anarchy/Cyphernomicon Technical: physics/soft errors/Smalltalk/Squeak/agents/games/Go Personal: b.1951/UCSB/Intel '74-'86/retired/investor/motorcycles/guns
Re: A Study into the Use of Laser Retroreflectors on a Small Satellite - M.Unwin
On Tue, 24 Jul 2001, Tim May wrote: More photons than the surface of the sun for HOW LONG? Continous. If you look at the sun constantly a certain number of photons hit a given area of your retina. Stare at a 1 mW laser and an equal or great number strike that same area. -- Nature and Nature's laws lay hid in night: God said, Let Tesla be, and all was light. B.A. Behrend The Armadillo Group ,::;::-. James Choate Austin, Tx /:'/ ``::/|/ [EMAIL PROTECTED] www.ssz.com.', `/( e\ 512-451-7087 -~~mm-'`-```-mm --'-
A Study into the Use of Laser Retroreflectors on a Small Satellite - M.Unwin
And these are reasonably low power lasers... http://www.ee.surrey.ac.uk/SSC/IJSSE/issue1/unwin/unwin.html The simple fact is that the thermodynamic impact of a laser beam that is several feet across and emitting more photons than the surface of the sun will not be easy to reflect unless immense cooling is taken. Cost/weight factors alone argue it in the negative. Remember, that laser is hotter than the surface of the sun area for area. You'll need cooling systems comparible to the aircraft carrying the laser (consider the cooling of the main or final steering mirror alone in aircraft weight). Even the finest mirrors will not stand up to that uncooled, and even then not for long. Consider the expansive impact on the cryogenic fuel components. How much are they over-rated? -- -- Nature and Nature's laws lay hid in night: God said, Let Tesla be, and all was light. B.A. Behrend The Armadillo Group ,::;::-. James Choate Austin, Tx /:'/ ``::/|/ [EMAIL PROTECTED] www.ssz.com.', `/( e\ 512-451-7087 -~~mm-'`-```-mm --'-
