Sailing among the stars: How photons could revolutionise space flight

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The spacecraft to be launched on Monday, called LightSail 2, was developed by the Planetary Society.[br][br][br] [br][br]A few days from now, a SpaceX Falcon Heavy rocket will lift off from Florida, carrying a satellite the size of a loaf of bread with nothing to power it but a huge polyester "solar sail." It's been the stuff of scientists' dreams for decades but has only very recently become a reality.[br][br]The idea might sounds crazy: propelling a craft through the vacuum of space with no engine, no fuel, and no solar panels, but instead harnessing the momentum of packets of light energy known as photons -- in this case from our Sun.[br][br]The spacecraft to be launched on Monday, called LightSail 2, was developed by the Planetary Society, a US organization that promotes space exploration which was co-founded by the legendary astronomer Carl Sagan in 1980.[br][br]But the idea itself has been around for a lot longer than that.[br][br]"In the 1600s, Johannes Kepler talked about sailing among the stars," Bill Nye, the chief executive of the Planetary Society, told AFP.[br][br]And building a solar sail doesn't require cutting-edge tech as you might imagine.[br][br]It's essentially a large square of very thin film (less than the width of a human hair), which is also ultra-light and reflective.[br][br]It has an area of 32 square meters and is made from Mylar, a brand of polyester that has been on the market since the 1950s.[br][br]As photons bounce off the sail, they transfer their momentum in the opposite direction to the bouncing light.[br][br]"The bigger and shinier and lower mass the spacecraft, the more of a push it gets," explains Nye.[br][br]The thrust provided by these photons is tiny -- but it's also unlimited. "Once you're in orbit, you never run out of fuel," he said.[br][br]Japan's space agency launched a solar sail in 2010, dubbed Ikaros, but others haven't been able to fully test the concept.[br][br]"It's a romantic idea whose time has finally come," said Nye. "We hope this technology catches on."[br][br]Unlimited energy[br][br]Its predecessor was LightSail 1, launched in 2015. But its mission, which lasted a few days, experienced problems and was intended only to test deployment of the sail.[br][br]Source : timesnownews.com

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