making a very powerful sun beam

Hi there, 
I  have a question and perhaps you could be of help to me, So my question is ,  is it possible to use cheap Mylar blankets(parabolic form) to concentrate the sun light, so as it would be able to cut through metal. My idea is to use 3 Mylar sheets each  1m square  which will reflect the light towards another  one which will work as a collector and then further concentrate the light to about half a millimeter.  Doing the math (0.5mm²/3m²) is more than 16 million (ok there  will be a lot of loss , lets say 50 percent). The question is, is this worth trying cause i don't want to waste time and money on this. So if someone knows why this wont work , it would be very helpful.
thanks in advance

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Kiteman2 years ago

You won't get it focussed well enough to *cut* metal, but it is possible to melt metal with focussed sunlight.

Even if all you did was char some sticks, making the collector would not be a waste of time - it would make a cool instructable, with an even cooler video of you sticking various objects in the focal point to see what happens.

caitlinsdad2 years ago

16 million what? Solar ovens get hot enough to boil water or cook food. Focused sunlight is not the same as laser light. What kind of metal and what thickness are you planning to cut?

Z3r01f1n1ty (author)  caitlinsdad2 years ago

about 2 mm, laser light is just filter light, meaning all the protons going in the same direction and having the same wave length, (hope i am not saying anything stupid), so is there a way to filter the sun light and if possible cheap. and by the way what i meant with 16 million was : taking 3 m square of sun light and concentrating it to 0.5 mm square is like the pressure you apply on 3 m square area will now be apply to 0.5 mm square thus increasing the pressure by a factor of 16 millions-> there will be a lot of loss in the process but if even only 10 percents would make it, you would still have an increase in pressure cause by the light with factor x million. and I saw a documentary a year ago about a company in Germany cutting a 3 cm thick cast iron with only the sun light, they had 24 x ( 1 m square) parabolic mirror and the beam just went through like butter.

You confuse one thing with the other - light has nothing to do with pressure, otherwise we not have so much trouble focussing it correctly, see the Hubble telescope.

For example:
You focus the light coming from a large mirror, prefereable by using something like a satellite dish in the first place.
If the curve of the mirror is even enough and you can keep track of the sun in real time you can get a focal point of under 2mm.

The problem is that is point is just just - a point, not a laser with directed light.

Please refer to Wikipedia on how a gas laser with mirrors produces a focussed laser beam.

That is why, for commercial application a massive array of relativly small mirrors is used.

Still you have light beams from different directions going through the focal point - this will never result is a straight cutting line on any material unless it is really thin.

To get the light from the mirrors focussed in a way that results in a usable beam pattern you need extreme accuracy to move the mirrors.
Of course you add one or two more mirros in the pathway of the light altering it's course to a more parallel line to the others, but again you need extreme accuracy.

Z3r01f1n1ty (author)  Downunder35m2 years ago

So this project will never see the light, too bad. Thanks for sharing your knowledge and time.

If you followed the Mythbusters on TV you would know it does not work.

A sun-oven to produce electricity and heat uses sodium chloride that is melted by the heat of the sun.

To that they use severl hundreds of mirrors - each and every one of them with an automatic tracking system to keep the sun in focus and the beam on the right spot on the tower.

You want to cut through metal, so you need a focussed beam with no divergence (or little) - like a laser.

Get an old big satellite dish, cover it with your reflective Mylar foil and see how much heat it produces in the focal point - after that you will abandone your project unless you have few hundred more of those dishes and some tracking systems.