Leadership

A modern Archimedes builds a solar death ray

The legacy of Archimedes lives on in the solar death ray inventions of Eric Jacqmain. Geekend contributor Edmond Woychowsky calls Jacqmain's R5800 Solar Death Ray fascinating and scary.

When I was a kid, I could amuse myself for hours on sunny days if I had a magnifying glass and an ant hill. On those days, I was Ra, Apollo, and Surya all rolled into one person. Maybe that's why the story of Archimedes' death ray has always fascinated me. Ah... to have the power to bring one of the most powerful nations in the world to its knees.

I thought of Archimedes when I watched the video of 19-year-old inventor Eric Jacqmain's R5800 Solar Death Ray. His invention had approximately 5,800 one centimeter square mirrors lining the inside of a satellite television dish, a simple aiming mechanism, and a wheeled base. The R5800 was destroyed in a storage shed fire in December 2010, and Jacqmain says the solar death ray was very likely the cause of the fire.

The R5800 Solar Death Ray is fascinating and scary. Jacqmain created the means to set alight the Roman navy, although the focal length is only about an arm's length, meaning that you'd need to almost be on the ship to set it on fire. While I'm not an expert on military tactics, I'm pretty sure the Romans would have something to say about this drawback. However, imagine if the focal length was at least 100 meters -- people moving back and forth would be able to torch a score of ships at a time. By the time the Romans figured out what was happening, they'd be swimming.

The video of Jacqmain's R5800 Solar Death Ray also reminded me of the MythBusters failed attempts (in 2004, 2006, and 2010) to reproduce Archimedes' legendary solar death ray. Maybe Archimedes knew more about optics and focal points than most people suspect.

Jacqmain is not discouraged that his R5800 destroyed itself. In the Daily Mail article about his invention, Jacqmain says the next solar death ray he builds will contain approximately 32,000 mirrors. Ants and ancient fleets beware... Archimedes' legacy lives on.

26 comments
Bill_R
Bill_R

I've been away from physics/optics for quite a while, so please correct me if I'm wrong, but it seems to me that the power (e.g., in kilowatts) delivered to, say, a 1 sq.cm. target located *at* the focus and aligned perpendicularly to the line of sight to the reflecting mirror/array should be independent of the distance from mirror to target, provided that we can disregard the attenuation of energy due to absorption by air molecules (O2, N2, etc.) and dust along the conical (in outline) light path (visible, fleetingly, at about 1:13 in the clip) from mirror to target, hence the "basically" proviso in my subject line. If the power delivered by sunlight falling on the, say, 1 sq.m. mirror is reflected without absorption by the mirror, then precisely the same amount of power will be delivered to the 1 sq.cm. target, minus the above-mentioned attenuation. Of course, the power *per unit area* delivered to a target *in front of or behind* the focus will fall off in inverse proportion to the square of the distance from the target *to the focus* (not the distance from the target to the mirror), again ignoring absorption by intervening air molecules, dust particles, etc. Note that, at around 1:29, Eric's thumb briefly enters the cone of light with no apparent ill effects. That's because his thumb is some distance in front of the focus, where the power per sq.cm. has decreased considerably, thanks to the inverse-square falloff with distance *from the focus*. If he were to build a shallower, but still *precisely* parabolic, mirror with a 10x longer focal distance, he could, in principle, perform the same feats at 10x the distance; however, this would be much more *dangerous*, since the apical (solid) angle of the cone of light would be roughly 1/10 that of the present apical angle (since "x" is roughly proportional to "sin(x)" for small angles "x"), and it would be difficult to pinpoint the precise location of the focus at that great a distance and difficult to ensure that a hand or other body part would not enter the (extremely narrow) cone of light near the apex/focus, and thus very dangerous to the experimenter or other persons or things nearby. (The *rate* of falloff of power delivered per sq.cm. of target would be 10x less per cm. from the focus, and thus the *danger zone* would extend much further in front and behind the focus because of the narrower angle.) So, *DON'T* build and/or use such a dangerous shallow mirror.

BlueCollarCritic
BlueCollarCritic

As usual you provide good info on the topic. QUESTION A: So the increase in area needed to move the focal point far enough to be effective would make the device impractical, yes? I am assuming based on your comments that the increase in surface area and mirrors top move the focal point out further is because of a loss of power/intensity of each beam of light between the mirror on the dish and where it converges with the rest at the focal point. Assuming that is correct then I would ask this, could the required increase of surface area be offset by intensifying each beam of light with something like a magnifying glass? This is just speculation/guessing so the question could be humorous to someone more versed in physics. Thanks Nick

BlueCollarCritic
BlueCollarCritic

WHAT IF - The dish or device holding the mirrors was not fixed in its curvature or size? Instead of having a fixed dish what if the mirrors were on something that was more like the Skelton of a dish shaped circle object that would allow one to change the curvature of the object which would in turn change the distance at which point the reflection form the mirrors converge?

BlueCollarCritic
BlueCollarCritic

I get the part about the distance, that thsi thing is limited in how far it raches based on the size but at best that shoudln;t be called BUSTED since its proven that such a device could in fact brun ships. So whats still in question is the distance and I think its ignorant to rule this one as BUSTED because of that.

cbeckers
cbeckers

Satellite antennas focus energy from a radiation source (satelllite transmitter) on a radio antenna that would otherwise not be sensitive enough to receive the signal. Typically, for a reflector this size, the receiver is about 1 m from the reflector. In this case, the "satellite" radiation source is the sun and...lo and behold...the focal point is where the radio receiver would be (about 1 m from the reflector). The larger the reflector, the more energy is focused on the receiver. Take a look at the antennas used at radio and TV stations to get their satellite feeds. To make a "solar death ray" with a longer focal length would mean building a reflector with a larger radius. To make a death ray that would be workable in the field, the radius of the reflector would need to be continuously variable, so the range of the weapon could vary. Not a practical weapon, but really fun for burning up aluminum cans!

RipVan
RipVan

The device was destroyed in a fire in the storage shed? So it was so powerful that it vaporized its own surroundings WHILE INDOORS???? Hey, I have some room on my credit card! Anyone know of any bridges for sale?

DHOLYER
DHOLYER

Now if you could only aim the device and not have the focal point in one spot. Normally it is fixed as to where the sun is. what if you placed a fiber optic cable at thr focal point, since fiber optic cables are flexible would that not let you aim the concentrated solar energy in any direction. Optics at the output end of the cable may be needed to focus the energy beam. I can see it now Army dudes carrying sun powered lasers into battle and power conducted via fiber optics, but it would be free energy and could only battle in the day light.It may be a stupid idea but it is a Green Energy project. If I was a tester of this device I'd first test it on it's inventor and see how good it works at reducing the quanity of Green Scientist's.

Realvdude
Realvdude

Of course the Mythbusters try to recreate the real scenario. In the last try, they concluded that the death ray was more effective through disorientation and intimidation. As for this, I think most ancient weapons were lethal even at 3 feet. Great use for an old satellite dish though.

jefferydeignan
jefferydeignan

Can you picture having a mini one for lighting a campfire, cooking food, or sterilizing water? Maybe mount the mirrors on a high-temp flexible background with which to adjust its focal length? How about using small prisms? Gets the mind working on theories and uses.

Ed Woychowsky
Ed Woychowsky

A solar tracker, a small round solar panel a little closer than the focal length and way to cool it so that it doesn't become snot on a sunny day?

abc123a
abc123a

I hope some at our DoD is reaching out this kid and making sure that they pick his brains. They could save billions in weapon development.

Dr_Zinj
Dr_Zinj

The Daily Mail that was the source had a few derisive comments about the kid and what he was doing. Sort of an oh hum, big deal, thing. Point is, this is a teenager actually applying the science of optics, with a project a wee bit more complex than just a magnifying glass or a hand mirror. Sure, we have commercial solar furnaces - just not built by a kid in his back yard. And yes, we have solar water heaters for pre-heating your water on your roof, or for cooking in the outback. But those are commercially manufactured items; not built from scratch or even a Heathkit. Me, I'd love to see someone buy a southern facing mountainside in Arizona or New Mexico; and turn it into a waste incineration plant, solar energy generator, or even a foundry operated solely by solar energy.

NickNielsen
NickNielsen

Maybe I should modify one of these to have a longer focal length (say...3-5 yards) and mount it on the rear bumper. It would definitely deter tailgaters... :^0

NickNielsen
NickNielsen

It may even be possible at longer ranges. But independent of the intensifying technology used, the problem remains that as the distance to the focal point changes, the area of the reflector has to change with the square of that distance to maintain the energy of the beam at a constant level. You also have the problem of getting your target (if animate) to stand still at the focal point of the beam, or to stay [u]in[/u] the beam at all. Even away from the focal point, such a beam would feel more than uncomfortably warm, with the possibility of severe burns increasing as one approaches the focal point. It may be possible to use such a beam as a means of crowd control or dispersal, although the possibility of temporary or permanent blindness exists for those who look directly into the beam. Either way, I wouldn't want to be the one in front of the reflector...

NickNielsen
NickNielsen

But the inverse square law applies, so to focus the same amount of energy at 30 meters as at 3 meters would require the area of the dish surface to increase 100 times . For example, let's assume we have a dish with an area of 1 square meter and a focal length of 3 meters; the radius of our dish is about .564 meters. To move the focal length to 30 meters, the area of the dish must increase to 100 square meters, with the radius increasing to 5.64 meters. It gets unwieldy very fast.

NickNielsen
NickNielsen

This time, pay attention to the discussion at the end. Adam and Jamie call it busted, not because the concept is invalid, but because they were unable to use 2000-year-old technology to make it work. What got busted was the claim, not the concept.

Brainstorms
Brainstorms

You're obviously missing the point.. Our DoD is not about saving billions in weapons development. Au contraire! It's all about SPENDING billions in weapons development. This kid had better watch his back... If he tries to put all those hundreds of U.S. DoD outfits and their hundreds of thousands of employees out of work with his ingenuity... Ulp!

Realvdude
Realvdude

http://www.solarclutch.com/ The primary buyers for the ones available for purchase, are missionaries and other aide groups. Homebrew ones are constructed of cardboard and tin foil; scarce materials in third world countries. A huge benefit are that women and children don't have to take the risk of being attacked while away from the village or town to hunt for firewood.

seanferd
seanferd

Heck, I'd help sell tickets.

AnsuGisalas
AnsuGisalas

Phased Array. The mirrors don't have to be mounted on a parabolic screen... they can be individual mirrors, each in a controllable mount. That also means that each mirror can be bigger... as big as it needs to be. Need more mirror? Deploy more units. Moving target? Not a problem - the phased array can adapt, sweeping it's focal point seamlessly. Of course, you need a computer to calculate the angles, but it's not rocket science... I figure a 486 could do it, if it's not doing anything else.

jos.paglia
jos.paglia

The Inverse Square Law is for energy from a point source radiated outward radially. For this discussion, the sun can be treated as a point source. The Inverse Square Law dictattes the amount of energy that reaches the Earth (in this case). At that point (of the Earth's surface) there is a constant amount of energy (x) per unit area (y). The area of the mirror (y) will always contain (x) energy. If focused (regardless of focal distance), the energy will still be (x). see: http://en.wikipedia.org/wiki/Inverse-square_law "The Inverse-square law generally applies when some force, energy, or other conserved quantity is radiated outward radially from a point source. Since the surface area of a sphere (which is 4r sqaured) is proportional to the square of the radius, as the emitted radiation gets farther away from the source, it must spread out over an area that is proportional to the square of the distance from the source. Hence, the radiation passing through any unit area is inversely proportional to the square of the distance from the point source" The sun's (point source) distance to the Earth (area) is constant to the mirror, reagrdless of the focal length of the *reflected* energy.

NickNielsen
NickNielsen

It is only effective on sunny days, darn it!

NickNielsen
NickNielsen

You are correct that a mirror with size (y) can only reflect (x) energy. That's why the mirror has to increase in size when the focal length increases. In general, regardless of the means of generation, the relative energy level, or the source, a particle loses energy relative to the square of the distance traveled. In greatly simplified terms, the energy in our reflected, [b]focused[/b] beam is equal to the speed of light divided by the square of the distance traveled. So, to focus the [u]same amount[/u] of energy at a greater distance, the size of our mirror must increase relative to the square of that distance.

AnsuGisalas
AnsuGisalas

That ship-lifting powerclaw he had, simply flip over the tailgater... Of course, I usually just slow down. I let them understand that by staying behind me they're subjecting themselves to my whim. And my whim isn't hardly ever to submit to empty threats of lethal force- what they're doing. They can take it, or they can grow some curlies and overtake. Preferably the latter, I don't want idiots driving close to me. ...Yup, ya can vote me down, but you still get to suck fumes at 30 kmph if you try to tailgate me :D

Editor's Picks