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In the NewsPrivate Mission Aims to Give Solar Sails Their Day in the SunSource: Daniel Cleary, "Private Mission Aims to Give Solar Sails
Their Day in the Sun," Science Magazine ,Science Vol 308 17 June
2005. Assembled by enthusiasts on a shoestring budget, Cosmos 1 could spearhead a new generation of photon-powered spacecraft. In the Star Wars movie Attack of the Clones, the villainous Count Dooku escapes the clutches of the Jedi in a spaceship that unfurls a vast, shiny solar sail to speed its way across space powered by starlight. Next week, something akin to this science-fiction fantasy will take to the skies above Earth. The spacecraft, called Cosmos 1, aims to show that solar sailing is practical in our solar system and beyond. “This is the only technology that can do interstellar flight’ says project director Louis Friedman, who is executive director of the Planetary Society, the nonprofit organization running the mission. Cosmos Studios, aUS. science entertainment company nm by Aim Druyan, widow of Carl Sagan, put up $4 million to bankroll the mission. Russian researchers at the Lavochkin Association and the Space Research institute in Moscow built the spacecraft, which will be launched from a Russian naval submarine aboard a Volna rocket, a converted ICBM from the Cold War. “Solar sails have come a long way in the last few years:’ says engineer Cohn Mclnnes, a solar sail expert at the University of Strathclyde, U.K. At all the major space agencies, he says, scientists are pushing the technology as the only feasible form of propulsion for certain niche missions. “Now it needs the commitmentto go to the next step:’ Mclnnes says. “Cosmos 1 can only do good.” Friedman got hooked on sails in the l970s, while working on a team at NASA’s Jet Propulsion Laboratory designing a solar sail mission to rendezvous with Halley’s comet That mission never got off the drawing board. But after co-founding the Planetary Society in 1980 with fellow space scientists Sagan and Bruce Murray to promote space exploration, Friedman got a second chance in 2000 thanks to Druyan, a member of the Planetary Society’s board of directors. With money from Joe Firmage, a philanthropist who made a fortune in the 1990s Internet boom, Druyan formed Cosmos Studios and made Cosmos 1 its first project. “We could have a real launch, a place in the history of aeronautics, all for the cost of a Manhattan apartment,” she says. Additional funding came from Peter Lewis, an insurance millionaire, and from the society’s 100,000 members. The society suffered a setback in 2001when a practice run aboard a Volna, designed to test unfurling a sail, failed. The current launch date is 21 June, the summer solstice. If Cosmos 1 reaches its intended 825-kilometer orbit intact and is working properly, ground controllers in Moscow and at the society’s headquarters in Pasadena, California, will start the mission. On command, inflatable booms will unfurl eight 15-meter-long triangular sails made of highly reflective Mylar plastic, creating a sail area of 600 square meters—some 1,5 times the size of a basketball court. The team hopes to see whether the pressure of photons bouncing off the sails will boost the craft to a higher orbit. “This has never before been done in controlled flight,” says Friedman. Researchers at several space agencies are eager to follow in Cosmos’s
wake. In April, NASA and contractor ATK Space Systems tested a 20-meter solar
sail in a huge vacuum chamber at NASA’s Plum Brook facility in Sandusky,
Ohio, and a second design from the company L’Garde will be tested later
this month. A team led by The European Space Agency (ESA) is also banking on the technology in collaboration with DLR, Germany’s space agency. Manfred Leipold of German contractor Kayser-Threde says that the agencies carried out a ground test of a 20-meter sail in 1999, and Leipold has since led a team that completed a design last year for a demonstrator mission in space. The mission is now awaiting a funding decision. How did solar sails go from science-fiction favorite to must-have technology? The answer is thrust. Conventional spacecraft must carry all their fuel with them, and some missions are just too fuel-hungry. Although solar sails get only a feeble push from photons, it is unremitting and over time can build up to very high velocities. Researchers say sails are ideal for station-keeping: putting a satellite in one spot and using the sail’s thrust to keep it in position. The National Oceanic and Atmospheric Administration is interested in using sails to station satellites above Earth’s poles, where they can monitor the poorly understood polar climate, watch the moon and auroras around the clock, and even provide a phone link to researchers at the South Pole. Other tempting applications include sending a probe to the sun and then pushing it into a polar orbit to observe the sun’s higher regions. “This is very hard to do with conventional propulsion” because getting into a highly inclined orbit requires so much energy, says Mclnnes. A solar sail also may be the only way to travel for spacecraft headed far in the opposite direction, to the outer reaches of the solar system and into interstellar space. Leipold says ESA is studying such a mission to the heliopause, where the solar wind gives way to interstellar space. Its 250-meter-wide solar sail would boost its velocity to 50 kilometers/second, three times the speed of Voyager 1. NASA too would love to send a craft to deep space; its plans envisage a huge 400-meter-wide sail. Such grand schemes may hinge on the small group of enthusiasts from the Planetary Society. Cosmos Studios has not been able to attract funding to film the preparations or launch, meaning that, as Druyan notes, “we haven’t been able to make a dime off it.” But Mclnnes says that solar sails should get a huge jump in credibility from the mission. “At meetings I can now put up slides with some real hardware:’ he says. |
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