The Solar Death Ray

Ant writes the "Solar Death Ray is made of 112 mirrors mounted on a platform 4 feet wide and 6 feet tall. Each mirror is a square roughly 3.5 inches on edge. All these mirrors focus the sun to a single spot 5 feet, 6 inches from the mirror platform. A wooden fork extends from the mirror base to the area near the focus and serves as a mounting point for Solar Death Ray targets. The mirror platform is mounted to the support frame on a pivot that allows the platform to be angled. The whole system is mounted on a set of wheels. The goal of the Web site was to show the results of the targeted items when the solar death ray was used."

Comments

Stirling Engine

[Skyshadow]

Wonder how much juice you could generate if you were to mount a stirling engine at the end of this sucker. Seems like it'd be a lot cheaper/easier to implement than normal high efficiancy solar cells if you could work out a reasonable and reliable sun tracking system.

Ha! You call that a solar death ray?

[Michael Woodhams]

THIS is a solar death ray: 10 metres of high-precision parabolic polished aluminium. (And there are bigger ones out there in the world too.)

I've observed there. Because it is radio astronomy, we could observe before sunset and after sunrise, but for some reason we had strict instructions to never let the sun fall on the dish. (That includes the back, but that was to do with thermal distortion of the dish, rather than frying the focus.)

I also used my HP48SX calculator (running a terminal emulator) to command the telescope to slew. Because of this, I claim the CSO as world's the largest and most expensive peripheral for a pocket calculator.

Larry Niven strikes again; Ringworld sunflowers.

[AtariAmarok]

Larry Niven invented the "flashmob" years ago. Now, it looks like someone has come up with something similar to his Ringworld "Sunflowers", which consisted of petal-ringed mirrors which could focus on prey and turn it into ash fertilizer.

Feh, Kid's stuff

[loraksus]

This one is a bit bigger!

The parabolic reflector gaves at the focal point a maximum flux of 1000 W/cm2. The experimentations takes place at the focal zone (18 m in front of the paraboloid. The range of available temperature is from 800 to 2500 C (the maximum reachable temperature is 3800 C) for a maximum thermal power of 1000 kW.
(Did someone just say holy fucking shit?)
Picture of the Odeillo Solar Furnace

Not so tiny

[PxM]

Given that he was able to set a rag on fire, I'm guessing that the Mythbusters team did something incorrectly regarding the focusing of their mirrors. And your link says they used a circular configuration which is only good in limited cases since the light is focused in a line (which isn't really focus) rather than a point. This was parabolic setup which is why he was able to melt plastic and set a rose on fire.

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Wired article as proof

Re:Not so tiny

[RodgerDodger]

We don't know what technology the Greeks had; we know very little about them. What we do know indicates that this was possible.

They certainly knew geometry and optics. What they didn't know was glass. Crystal lenses have been discovered all over the Mediterranean.

Discovering how a parabolic array (lots of flat mirrors lined up along the curve of a parabola) focuses light is something that Archimedes could have confirmed - all it takes is an inquistive mind and observation. Getting a few hundred soldiers to position shields correctly would have been fairly trivial.

Why wouldn't it have become a popular weapon? It's not reliable enough. You need to have lots of mirrors, room to set them up in a parabolic curve, lots of bright sunlight, and a relatively slow moving target that will cross a known point at the right time. It's not easy but it would be possible.

Consider that triremes didn't usually sail at night - an invading fleet might well have pulled up not far from the harbor for the night, with intent to sail in an hour or two after dawn.

See:

http://www.mlahanas.de/Greeks/Mirrors.htm
http: //www.trmkt.com/902manu.html

And google for "ancient greek lens"

Re:MythBusters?

[ChipMonk]

Maybe not igniting them directly, but...

How about blinding the sailors on board, who then run around in a panic and knock over the pot of charcoals used for igniting the flaming arrows? Carcoals ignite the ship's deck instead, or someone's clothes, the fire spreads, voila. No more battleship.

Definitely not new

[Jon Abbott]

This is a solar furnace, of which there are many in use today. The biggest one in the world is the Odeillo Solar Furnace located in Odeillo, France. The top 3 in use in the United States are at Sandia National Labs, Georgia Tech and the White Sands Missile Test Range. Awesome stuff!

One amusing side note is that Frank Gehry's popular postmodern buildings have been noted to act as solar collectors, effectively frying people passing by on the sidewalk.