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

Don't /. the site

[AstroDrabb]

Use the Coralized link here!

The myth is dead! Long live the myth!

[elflet]

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.

Re:The myth is dead! Long live the myth!

[b1t r0t]

Apparently it worked when it was tried in 1973 (see middle of page).

A Greek scientist, Dr. ioannis Sakkas, curious about whether Archimedes could really have used a "burning glass" to destroy the Roman fleet in 212 BC lined up nearly 60 Greek sailors, each holding an oblong mirror tipped to catch the Sun's rays and direct them at a wooden ship 160 feet away. The ship caught fire at once.....Sakkas said after the experiment there was no doubt in his mind the great inventor could have used bronze mirrors to scuttle the Romans

Re:The myth is dead! Long live the myth!

[kd5ujz]

They were testing the effects of SOUND on the plants, not the effects of breathing on them. Its obvious that if they crack open a bottle of CO2 inthe corner of the room, the plants will grow better.

They DID show that plants that are exposed to sound grow better, and ones that are exposed to death metal grew the best.

Re:Magnification

[Yotsuya]

Mirrors do the same as magnification, it concentrates the sun in one place.

Anyway, it's been done before:
http://www-personal.umich.edu/~bclee/lens .html

Re:Magnification

[jafiwam]

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....

Re:Gluttonous REAL GENIUS plug...

[temojen]

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.

Magnification does nothing

[gnuman99]

Magnification does nothing. It is light intensity that counts. You may use a magnifier to focus the light from a larger area to a smaller area - you don't magnify it. The mirrors do the same thing.

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)

Re:Magnification does nothing

[The_Wilschon]

Exactly. In order to get the same power output from a completely magnification based setup, you'd need a magnifier with area about equal to the area of all the mirrors put together. The only really feasible way to do this is to use a fresnel lens, a normal lens would either be much too thick in the middle (because the thickness is proportional to the radius, and we're talking a pretty good sized lens) or else the focal point of the lens would be pretty far away...

Re:Stirling Engine

[loraksus]

These folks should know ;)

Your museum sucks.

[douglips]

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"

Re:Take it to the Nth Degree!

[Delilah Jones]

Yeah, I'm checking this out right now.

http://www.wentworth.nsw.gov.au/solartower/faq.p hp

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.

Re:Ultimate Geek Toy

[ucblockhead]

Not true. It has to go through more atmosphere if it is at a lower angle of incidence.

1 killowatt "deathray"

[goombah99]

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.