19y.o. kid covers a satelite dish with mirrors and creates "death ray"

[ryuke]

Come on, now. Polished shields? You mean, tightly-toleranced parabolic shields with a focal length of at least a hundreds feet, and lapped to mirror finish?

It's a cool story. It's also pretty ridiculous. And even aside from the pretty blatant infeasibility, have you wondered why this wasn't an incredibly common method of destroying ships, if it worked? If this was successful, why didn't it essentially dominate naval force for the next thousand years, becoming very well-documented in the process?

He's right, partly. It was Archemedies, but its said he made one big parabolic mirror, or sorts, and sunk an invading fleet from land, its proclaimed as the first WMD

Heres some more mirrors
Archimedes and his Burning Mirrors, Reality or Fantasy?

[Golden Mean]

Greetings!

I bought a few Fresnel lens a couple years back and did some experimentation. Using an 11 inch diameter lens, I was able to measure temperatures over 1100 degrees in full Sun. The lens cost about $20.
I have design plans to build a simple solar tracking system for it, but got side-tracked by other projects.
I recommend a Fresnel lens over a parabolic dish for the ease of use and cost as well as time.
Warning... USE WELDING GOGGLES if you plan to experiment with concentrated solar energy!!! It WILL fry your retinas if you are not careful!
Also, have to watch where you put your hands and other materials, animals coming around like dogs or cats or kids, etc.
Treat it like a very dangerous high powered laser!

One last little note... One of the experiments I tried was roasting a marshmallow. Didn't work. I'm embarassed to say it took me a minute or two to figure out what was going on as wood would ignite in an instant poof!... but the marshmallow would just sit there.... not even get warm!

Marshmallows are so white that it acted like a mirror and reflected most of the energy off. As soon as I put a tiny tiny speck of dirt on it... it quickly grew black around it and poof!

Yes, they are fun to play with! :?)
Have a great day!
Ahimsa.
~ Golden

[gravityblock]

Thanks for correcting me. Most things do have both a negative and positive
component to them, if not all things, like electricity. I do not understand how you will do it at a larger scale than the nano scale done in the article.

FRC

I was thinking about splitting the light at the focal point into two beams which each will travel on a waveguide of a different length to cause the two light beams to become out of phase to create a repulsive force. The more out of phase with each other, the stronger the repulsive force. I am assuming of course, the strength of the repulsive force is also proportional to the intensity of the light at the focal point. If not, then it can only be done on the nanoscale. Only way to know, is to do the experiment. The experiment is probably easier said than done, but I see no reason not to try. I'll probably throw other things at it also, such as having each of the light beams to propagate through a different medium, such as one beam through water and the other beam through air, etc. If it fails, then I'm sure it will still be a good learning experience.

GB

[QMC]

I bought a few Fresnel lens a couple years back and did some experimentation. Using an 11 inch diameter lens, I was able to measure temperatures over 1100 degrees in full Sun.

Big fresnel lenses are great fun. With one from a projection tv, some friends and I melted pennies on a clear day. Nice job actually measuring the temperature you produced. And that's a good tip on the welding goggles; we did the same.

[mbrownn]

I am being silly here, but I’m sure it would work. After you concentrate the sun with a lens or parabolic mirror, you could use a diverging lens or convex mirror of the same focal length to make the beam parallel. This could be then reflected in the direction you want with a mirror. If this was done at the focal point it would be as powerful as any industrial cutting laser. Great for cockroaches and other undesireables.

Be careful pointing it at any reflective surface.

[kcarring]

Hi kcarring,

I am interested in the home made turbine you mentioned. I tried searching the Mother Earth News website but did not find any info about a home made turbine for steam. I found a little info about wind and water turbines. Were the plans in the magazine or did you have to order them from MEN? If it was in the magazine do you remember what issue? I saw where they have back copies on cd available now. Was this turbine similar to the Tesla Turbine as his design looks pretty easy to make for a home built project?

On another note do you think it would be possible to use a large metal block of cast iron or other metal as a heat sink to stabilize the temperature and have holes drilled through it to let the water circulate instead of the salt storage. I realize you could only use this in the daytime to charge your battery bank. It just seems like it would be a lot easier than dealing with all the problems you reported having with the salt.

Thanks for any info you care to share.

Carroll

P.S. Why did you say the turbine was dangerous?

>> As far as I know it had nothing to do with Tesla's design whatsoever, and the issue was very old, 70's or 80's at least. ME News used to be quite full of off the wall projects, way more so than nowadays. It really wasn't that good of a design OR I made some bad errors, one or the other case was definitely true. Or, my welds were bad. The thing is.. steam has unbelievable force behind it, that was the learning experience for me. It flew part the third time I used it. I quickly learned, too, that pressure relief valves do not necessary discharge any faster than something blows to smithereens: another consideration. When pressure accumulates very fast, as in a turbine, in theory the pressure relief valve SHOULD go first, as it is set to discharge at a lower PSI than the rest, but... this unit was not engineered well because the entire turbine blew apart all at about the same time.

[kcarring]

This is an interesting article:

Solar Steam Turbine, Examining the Curnutt Solar Furnace, distributed energy, solar electrical generator project, Ken Rieli, Phoenix Turbine Builders Club

[kcarring]

"On another note do you think it would be possible to use a large metal block of cast iron or other metal as a heat sink to stabilize the temperature and have holes drilled through it to let the water circulate instead of the salt storage. I realize you could only use this in the daytime to charge your battery bank. It just seems like it would be a lot easier than dealing with all the problems you reported having with the salt."

first off, steam engines vs. steam turbines are worth some consideration, but the problem with either is VOLUME.



to get the volume, you'll need a buffer.

Based on my experience, i think you'd need a lot of mirrors/lenses to do on demand production of steam for a small engine, but im not going to say it's impossible, im sure if it was really well thought out, it could be done. I see one company seems to offer it... back in this thread a ways...

Turbines are better suited to large application (i learned that afterwards).

Here's a consideration.

Many, many thrid world countries have community solar ovens. That end of it is not so complex. Think of that... an oven that sits there, everyday, hot enough to cook. Of course this is most likely near the equator... however, the point is, the buffer, the available heat... it's very doable and gives the entire system stability.

[kcarring]

Here is a working solar thermal steam engine, 12kw.

YouTube - STEAM ENGINE 12KW GENERATOR Solar Mirror Array

[citfta]

Thanks

@ kcarring

Thanks for the links. Some very good and interesting info there. I appreciate it.


Carroll

[kcarring]

In the 1970's,the department of energy tried this ame thing in the California desert. They took a standard water tank(used in most towns),set it up in the dsert and surrounded the tank with mirrors in a 360 degree circle. They were set at a distance far enough to allow some mirrors to be reflecting on the tank all the time.No tracking of the sun was needed. On top of this tank set a huge turbine. It only took about 30 minutes from the time the sun came up to start producing electricity. The only problem was that they had to pump water from a river,a long ways away, to fill the tank. It used more water than they could pump economically,plus it put a trmendous amount of steam into the air, as they did not try to recapture any of it. They abandoned the project shortly thereafter.They claimed it was capable of producing enough electricity to power a large city.Good Luck. stealth

Interesting. Rather crude sounding too. Steam reclamation is pretty essential, and certainly not the most difficult part by any means. My first project involved a home-made steam turbine, which, in fact was absolutely ridiculous on two accounts: 1. You need to build sucha thing out of stainless steel with quality welds, steam power is insanely dangerous when combined with inadequate materials 2. Turbines work best, and make the most sense in large applications. A steam engine would be the preferred device on a small unit.

[mbrownn]

Yes like myth busters, the best way to debunk a device is to build one that does not work (no magnets).

Remember the best way to boil water was coal in the 19th century, oil in the 20th and nuclear in the 21st. The sun does not effect climate, CO2 is killing the earth and my 4WD is melting the ice caps on mars.

[mikrovolt]

To Buglar,
I absolutely love the deathray device video,
I think the young man deserves a nobel prize.

I saw one of those satalite dishes in the trash one day and
thought it must be good for something.

The sheer simplicity the wagon the little mirrors the demeanor
and the awesome display in that video really made my day.

[bugler]

I was thinking this morning that the dish could be used to heat a home.
I thinkg it would be a very easy and cheap device to construct.

Maybe we could open a thread about that.

How to heat your house with a parabolic mirror (or any other shape)?

[mikrovolt]

aim the parabolic mirror at what ?

what about a heat tube such as
a vacuum tube solar heat or evacuated solar tube and concider the geometry
you will notice the tubes are long and spread out.
If you aim the parabolic mirror at it would work better with a more concentrated shape.

It all started with a modified light bulb
This s the first battery charger rectifier tube 1917
http://www.oneillselectronicmuseum.c...blue/blue1.jpg

Aim the parabolic mirror at something like these these shapes:

Large Vacuum tube | Flickr - Photo Sharing!
http://steampunkworkshop.com/userfiles/audion.jpg
http://farm4.static.flickr.com/3127/...24d7f959_b.jpg


I have many times thought that solar to electric conversion
may be possible using thermal solar and pv along with a vacuum tube, I see it as a
large thermionic tube were the mass of the heater element gives
slight orange glow so the electrons are emmited across a vacuum.
a dipole is set up and is maintained by dc pulse into a
hartley oscillator arrangement using bifiliar coil.

like a thin 4 inch by 4 inch square tubing brazed end caps to form a cube.
this would be enclosed in a double walled glass evacuated enclosure.
Behind this are PV cells to pick up the excess light.