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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."
Use the Coralized link here!
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It's really only a "death ray" if you're really really tiny. Mythbusters did a great job of blowing the myth apart, with a much larger mirror array arranged in a proper fresnel configuration. It douldn't set fire to much of anything, even when they put gasoline on the target.
That's not Wierd Science, it's Real Genius, genius.
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Mirrors do the same as magnification, it concentrates the sun in one place.
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Anyway, it's been done before:
http://www-personal.umich.edu/~bclee/len
Claude Angers
This myth was busted on Discovery Channel's Mythbusters in episode 16:
http://dsc.discovery.com/fansites/mythbusters/ep isode/episode_03.html
Aside from making a giant palette of mirrors (and unsucessfully attempting to ignite a small boat), they tried to no avail to be sprayed by a skunk.
That show is classic.
Well... the whole point is energy per unit area on the object.
This is focused light via reflection, not refraction as would come from a magnifying glass or lense.
This contraption probably wouldn't gain much by using a lense. Extra square footage of mirrors would increase it's delicious fry-it power though....
No, because they would get very HOT, and the efficiency goes down dramatically with increasing temperature.
Actually the Mythbusters were trying to take out a wooden boat that was a couple hundred meters (that part I'm not sure of). They wanted it to catch fire. This guy is concentrating the energy and melting stuff, not actually setting anything on fire (except the clue board). Setting fire to a wooden boat far away is a lot tougher than melting a rubber ducky.
Better patent that idea before someone else makes use of it.
Government of the people, by corporate executives, for corporate profits.
No, it was a laser... very intense highly colimated (parallel) light. This site is about a parabolic reflector, which makes the light converge on a small area. Lasers can target any point in line with the beam. With a parabolic reflector, the light gets weaker (less concentrated) as you move past the focus. Beyond the distance between the reflector and the focal point the light is weaker than the origional light. Of course this is a faceted reflector, so the light isn't really weaker, it's just less and less likely that any point on a plane parallel to the relector will be illuminated the further away from the focal point you are.
The magnifying glass would have to be the same area as the sum of the areas of the facets.
Proof: Take a microscope and set it to 500X. Point the objective at the sun. Do you death rays spewing from the eyepiece? (Answer: no). To find out why, read the first paragraph or ask someone that *really* knows. (Hopefully someone that took some optics (physics) or astronomy)
These folks should know ;)
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Ah, after some more reading, the myth itself that he did it with a circular configuration which they showed to be impossible. I guess they didn't know about parabolic reflections in those days. However, since a parabola is defined as the set of points equidistant between a point (the focus of the death ray) and a line (the infinitely far light of the sun reflecting off an imaginary flat mirror) this means that all the tangents of a parabolic curve (the flat mirrors in this case) will always cause the light source to reflect at a single point. This is why well designed radio dishes and telescopes use parabolic reflectors to concentrate the light. Reflectors also don't have the problem of different frequencies reacting differently like normal lenses.
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Wired article as proof
No offense here to Larry Niven (big SF fan here) but Archimedes has prior art for them since 2200 years or so.
What sort of lame museum exhibits things you can buy for $5 on ebay?
Tetris the Classic PC Puzzle Video Game 5.25" 3.5"
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Yeah, I'm checking this out right now.
p hp
http://www.wentworth.nsw.gov.au/solartower/faq.
It doesn't use mirrors, but a covered substrate which captures the hot air (greenhouse effect), and funnels it into a large central tower.
The hot air (no water/steam required in this design) then moves the turbines.
Looks pretty sweet.
http://augustwestproducts.i8.com
Not true. It has to go through more atmosphere if it is at a lower angle of incidence.
The cake is a pie
I assure you that mathematicians in Archimedes' day knew all about the properties of parabolas.
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polished aluminum is used because its sub-mm but not extremely sub-mm (ie, optical).
its been awhile, so i forget the exact formula, but basically your surface can be as rough as some fraction of the wavelength you're trying to focus. Hence, wide waves can use dirty and/or rough surfaces (such as arecibo, which is just a hole in the ground and some perforated aluminum panels) and still work just fine, even when soiled as a huge bowl in the ground is bound to become.
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See my post for a great site describing the use of this weapon on more interesting specimens.
the death ray is 4 feet mirror is 4 feet by 6 feet. It looks to have a bout 50% of its area covered with cheap mirrors, which I'll assume are about 80% refelective. that makes it about a square meter of effective reflectivity. the solar flux near the equator is about 1 kilowatt per sq meter. This is focused down to an area of about 6 inches square or about the size of a stove burner. A typical stove burner probably runs at about 1.5 KW. so basically this thing has the heat delivery of a burner. Actually a bit less since the object itself may be reflective over a large part of the spectrum. So call it maybe half a stove burner. Still plenty to fry plastic, your hand, or even start a fire.
Some drink at the fountain of knowledge. Others just gargle.
No, the original poster was only mentioning it for the fourth time. And they posted it no more than 2 minutes after the original mention of Mythbusters.
I agree with the grandparent - the post really didn't need to be moderated redundant. Some moderators seem to be under the delusion that just because a post is 3/4 of the way down the page that it was posted *after* all the comments above it, and somehow the poster must have submitted despite all the references that already existed.
Read the posting times, and cut the guy some slack.
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Actually, no, because he is using flat mirrors, not parabolic ones. This means that the light is approaching from several different agnles at several different points. In order to refract or reflect into a collimated beam, the mirrors would have to be slightly curved, or he would have to have one large mirror. A reflecting telescope has all of the equipment necessary to make such a device.