Solar Sail Spacecraft Set for Launch

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The program "truly signifies the swords-into-plowshares [idea] by using assets designed to destroy worlds to become instruments of scientific progress," said James Cantrell, president of Strategic Space Development, a consulting firm based in Hyde Park, Utah. Cantrell is a management consultant to the Cosmos 1 program.

Simple Principle

Cosmos 1 has eight rotating, solar-sail "blades." Triangular in shape, the blades are about 50 feet (15 meters) long. They are made of aluminum-reinforced Mylar and are about a quarter the thickness of a trash bag. The spacecraft itself weighs only about 220 pounds (100 kilograms).

The principle of solar sailing is fairly simple: A spacecraft is pushed along by photons, or light "particles," emitted by the sun. The pressure of the photons as they bounce off the solar sails propels the craft, which theoretically doesn't need an engine.

In the case of Cosmos 1, scientists hope to fly the spacecraft for a few orbits around the Earth. Their goal is simply to demonstrate that the technology works.

"It's a modest goal—get it up there and fly a little bit under sunlight pressure and increase the orbit energy," Friedman said. "But I remind everybody that the Wright brothers only flew 12 seconds and went nowhere. But that flight was very important."

"Our goal is to do the same thing: to prove a technology that will later be used in many, many ways in much more elaborate developments," he added.

The solar sail spacecraft has another advantage over a chemical rocket: continuous acceleration. Sunlight striking the sails applies thrust continuously, enabling the sail (and spacecraft) to accelerate all the time.

In a hundred days a sail could top a speed of 10,000 miles an hour (16,000 kilometers an hour). In a year a sail could reach 36,000 miles an hour (58,000 kilometers an hour), and in three years it could top 100,000 miles an hour (160,000 kilometers an hour).

Giant Lasers

In theory solar sails could be used to boost or decrease the orbits of spacecraft. In a few decades, the scientists predict, sail-powered spacecraft may be used as interplanetary shuttles. Researchers add that one day the technology could even be used for interstellar flight.

One major problem is that once a theoretical solar-powered spacecraft gets much beyond the orbit of Jupiter, solar energy becomes too weak. Interstellar light sails would have to be powered by lasers.

"When sunlight grows too faint, powerful lasers could push your sail at even higher speeds," Friedman said. "The sail attached to your spaceship would be several kilometers wide, among the largest structures ever built, but as [thin] as spiderweb silk."

While that technology could be a century away, Friedman says he and his Cosmos 1 colleagues plan to aim a microwave beam on the spacecraft's sails to accelerate it.

"If we can actually measure the acceleration of a microwave beam on the spacecraft, that would be the first interstellar propulsion experiment," Friedman said.

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