Spacecraft to Launch, Propelled by Sun and Sails

On Tuesday, a group of private space enthusiasts will launch a new kind of spaceship, pushed along by eight giant sails fueled by light particles. Because such craft don't need to carry fuel, backers hope that solar sailing technology could one day put travel to distant solar systems within reach.

A rocket launched from a Russian submarine under the Barents Sea will send the Cosmos 1 on its way. Once the craft is in orbit some 500 miles above Earth, its eight triangular blades, each incredibly thin and made of mylar, will deploy.

Photons will hit the sails and bounce off, giving Cosmos 1 a push forward that slightly but continuously accelerates it through space. After three years, such a solar sailing ship could cruise along at a 100,000 mph.

But the Cosmos 1 isn't expected to reach those speeds. Louis Freedman of the Planetary Society, the group sponsoring the mission, says radiation is likely to destroy the Cosmos 1's fragile sails after a few months. Tuesday's launch is really a proof of concept. "We're willing to fly for just a few days, go nowhere, but prove the concept of controlled solar sail flight," Freedman says. "Sort of in the spirit of the Wright Brothers, who flew 12 seconds and went nowhere, but it was rather significant."

Web Extra: Setting Sail in Space

By Katie Unger

The Cosmos 1 craft expected to lift off from a Russian submarine on Tuesday will be equipped with sails powered by the sun. These solar sails are like big plastic mirrors that use light particles from the sun to push the spacecraft forward. But researchers are also working on another kind of sun-powered sail, called a plasma sail. It would harness energy not from the sun's light, but from the solar wind -- the charged particles that flow constantly off the sun.

Plasma sails don't look like the billowing sails of a boat, or even the giant plastic triangles used on Cosmos 1. In fact, a plasma sail can't be seen, because it is made up of heated gas and a magnetic field.

Like Cosmos 1, a plasma-powered craft would be small and lightweight, because it wouldn't need to carry any propulsion fuel. But it would need to carry a magnet to generate the balloon-like electromagnetic field around the craft. Injecting the plasma, or hot gas, into the magnetic field would "inflate" it, creating a giant "sail" tens of miles wide. The charged particles of the solar wind would bounce off the magnetic field lines, propelling the craft forward. The solar wind's constant flow would allow the ship to accelerate continuously, picking up speed as it heads towards the outer reaches of the solar system.

A plasma sailing vessel could go stunningly fast. A trip to Mars could take a mere 50 days instead of the six months that's possible with today's technologies, says Robert Winglee, director of the University of Washington's Research Institute for Space Exploration. He's head of a team that has drawn up plans for a plasma sail.

Because bigger sails make for a faster spacecraft, the huge size of plasma sails offers an advantage over solar sails. Using plasma and magnets to make a giant sail might prove easier than trying to make and deploy a plastic solar sail 30 miles wide.

Still, solar sails are way ahead of plasma sails, which have barely left the drawing board. Winglee says plasma researchers have struggled because the sails are complicated to think about. "It's easy to visualize a mechanical surface," like a plastic solar sail, he says. "It's very much harder to visualize a plasma-magnetic system."

And it's also hard to figure out how to test a plasma sail. Les Johnson, who manages NASA's In-Space Propulsion Technology Projects Office at the Marshall Space Flight Center in Huntsville, Ala., says some technical issues are holding back the plasma sail idea. One problem: There aren't big enough vacuum chambers on Earth to test a miles-wide magnetic sail. But Johnson says plasma sails are "a cool idea," and he predicts NASA will give them another look in a few years.

Katie Unger is an intern for NPR's Science Desk.

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