Parabolic mirrors concentrate sunlight to power lasers
Legend tells of Greek engineer and inventor Archimedes using parabolic mirrors to create "heat rays" to burn the ships attacking Syracuse. Though the underpinnings of that claim are speculative at best, a modern-day team of researchers at the Scientific and Production Association in Uzbekistan has proposed a more scientifically sound method of harnessing parabolic mirrors to drive solar-powered lasers.
Small scale analogs of giant reflector telescopes, these proposed ceramic lasers would convert an impressive 35 percent of the Sun's energy into a laser light, providing a considerable increase in the maximum power produced by current-day solar pumped lasers, which typically achieve only a 1-2 percent efficiency.
As outlined in the AIP's Journal of Renewable and Sustainable Energy, the new solar lasers would concentrate light with a small parabolic mirror 1 meter in diameter that has a focal spot approximately 2-3 centimeters in diameter. The concentrated light would then strike a two-layer ceramic disk known as a Neodymium and Chromium co-doped YAG (yttrium aluminum garnet) laser material.
One side of the disk would have a highly reflective coating; the other side would be anti-reflecting. When sunlight penetrates through the ceramic material, it excites the electrons in the material, causing them to emit laser light of a specific wavelength (1.06 micrometers). To control the searing heat produced by the concentrated sunlight, the ceramic disk would be mounted atop a heat sink through which water would be pumped.
The laser light would then travel to a prime focus and be reflected back to the ceramic surface before exiting the solar collector at an oblique angle. It's this "double pass" path that produces the gain in efficiency, enabling a greater fraction of sunlight to be converted into laser light. Potentially, parabolic reflector lasers could be harnessed for the large-scale synthesis of nanoparticles and nanostructures.
More information: “Transformation of concentrated sunlight into laser radiation on small parabolic mirrors” by Shermakhamat Payziyev et al. is accepted for publication in the Journal of Renewable and Sustainable Energy.
Provided by American Institute of Physics
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Sep 12, 2011
Rank: 5 / 5 (2)
Still, this is an interesting application - for daytime research anyhow.
Sep 12, 2011
Rank: 4.5 / 5 (4)
I think "modern" people significantly underestimate the cleverness and fortitude of our forebears. After all, the siege of Syracuse lasted for several months, so a desperate genius with lots of helpers would have had plenty of time to get his mirrors/lenses working.
Sep 12, 2011
Rank: 5 / 5 (5)
The MythBusters concluded with a "Busted" conclusion.
Sep 12, 2011
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Sep 12, 2011
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This will finally allow us to make war with lasers, using the power of the sun. Unfortunately, we won't be able to fight during bad weather or at night.joking of course ;)
Sep 12, 2011
Rank: 5 / 5 (2)
Gives new meaning to the term "Eco-Warrior"!
Sep 12, 2011
Rank: 4.5 / 5 (6)
For some reason I don't place the myth busters intellect and engineering prowess to be any where near the noted genius of Archimedes.
Sep 12, 2011
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Dan Rojas and his wife Denise were able to replicate it over a distance of a few scores of yards within a few minutes of trying.
It didn't even take anything fancy. He took regular flat mirrors and made some frames that allowed him to introduc a slight bend to the mirrors, etc.
Within a few minutes he had a mockup-up target fully engulfed in flames, with temperatures over 1070f...
The mythbusters just don't know enough about optics...nor did the MIT guys apparently.
http://www.youtub...CPX8r_9s
and
http://www.youtub...k1l0LjEs
A wall of such mirrors could have easily been used to catch fire to ancient wooden vessels, which were often pitched for water proofing.
The other thing is that burning human eyes woudl be a lot easier than burning wood. You could just as well blind the enemy army.
Admittedly, this test is at 100ft, so it would take a lot more mirrors to out-range say, archers with burning arrows...
Sep 12, 2011
Rank: 5 / 5 (3)
There would certainly be an issue with blinding the occupants though. I think it could be effective even if it doesn't burn the ships.
I'd like to see a mixture of the 2 methods. Use Dan's mirrors with the MythBusters' setup against a real ship on real water at real distances.
Sep 12, 2011
Rank: 5 / 5 (1)
Oh, what a shame.. lol. I guess it would be a lot more effective in the middle east, no?
Sep 12, 2011
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This could have been more of a psychological or "defensive" terror weapon, rather than destroying ships as a primary purpose.
Figure it's the ancient world, you're in a wooden boat trying to attack the enemy, wh en all of a sudden a small fire breaks out, and then the first two guys that try to throw water on it get their eyes burned out, you'd probably be scared to death, even if the fire wasn't big enough to be a threat.
However, someone would need to demonstrate this as an effective terror weapon with a greater effective range than the flaming arrows fired from the early composite bows of the time period.
For simply firing an arrow with an oil soaked tip which is burning at maximum range, I believe a composite bow could make a shot of perhaps 100 yards, depending on the wind.
In theory, the death ray was limited only by the horizon and the focal length of the mirrors.
Sep 12, 2011
Rank: 4.2 / 5 (5)
The point is that using modern mirrors to prove/disprove the old legend really proves nothing. The best mirrored surfaces they would have had back then would me many times duller than a modern mirror.
Even even if you had hundreds of these and even if they knew how to focus the beam, they would still need to keep all the mirrors aimed on the one spot (more or less) for a significant period of time to get any heating. You have the problem of constant ship movement as well as each person's ability to maintain aim on some agreed spot way off in the distance.
And to be effective, it would need to work at a long distance because once the fleet is close enough to shore, it's already too late. It's also harder to aim at multiple vessels closer in. And the sun better be shining!
Sep 13, 2011
Rank: 1 / 5 (1)
I disagree.
he showed in the video that you can make a highly reflective mirror from just a piece of metal.
you realize the lighthouse at Alexandria was constructed around this time frame? These people were not completely ignorant of how to focus light.
Saying the Sun better be shining is a no brainer, but that's no different than using flame arrows to try to catch the ships on fire, because if it's raining, that doesn't work either.
Sep 15, 2011
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Uh, a dichroic mirror in space plus this light-pumped tech could give useful energy transfer-- Beam-riding solar sails ?? Asteroid nudging ??
{ FWIW, 'sail'... }
Sep 16, 2011
Rank: 5 / 5 (1)