Saturday, August 27, 2011

Green Futures: Cutting-edge design is based on the light exerts pressure as the driving force

The force is with us, even if it is very small indeed. Scientists have long been aware that radiation of any kind exerts pressure, and light is no exception. In the 1920s, the Soviet rocket-designer Friedrich Zander suggested that a spaceship could be propelled solely by sunbeams and over time could reach very high velocities.

Sure enough, May 2010, the Japan Aerospace Exploration Agency launched the world 's first spacecraft designed to use solar power as the primary driving force. IKAROS - or the 'Interplanetary Kite-craft by radiation from the sun \ Accelerated' - developed a polyimide-sail and set out for Venus, which it has achieved, as expected, in December. The sail is 14 square meters, but only 7.5 microns thick, and its highly reflective surface doubled the thrust power of the sun there, all of 0.112 gram force.

Now a team of researchers at the Rochester Institute of Technology in New York has revealed another trick can make a light. Take a transparent rod, semi-circular in cross section and thinner than a human hair, and a beam directly on them. As the stream of photons flowing through them, the pressure they exert first turns, until she finds her balance and then she does not push in the direction of the stream, but to a certain angle. It 's not unlike the way the air flow around an airfoil creates' lift '.

Tiny as this effect, such a 'lightfoil' applications were not only in the near vacuum of space, but also on the Earth. "The advantage of these rods" said Ortwin Hess, professor of physics and Leverhulme Chair in metamaterials at Imperial College London, "is that you can use a lot of them together." And on the nano-scale, adds He can also add very small effects have a huge impact.

So, what is that good? The pressure exerts light is tiny, and there are only two contexts in which it can be used: in space where there is an almost total vacuum, and therefore almost no resistance to the force it applies, and in nanotechnology, where things this need have moved very little mass.


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