Space travel gets solar-powered

United States and Russian scientists are planning the ultimate in fuel-economy travel: they hope to launch a space sailing ship driven only by the pressure of sunlight later this year.

Cosmos 1, an unfurled fan of 15 metre sails, each far thinner than a dustbin bag but stiffened and coated with mirror material, could be launched from a Russian nuclear missile submarine.

A rocket designed during the Cold War to attack Britain or the US will be fired from beneath the Barents Sea with the furled sail in place of its warhead.

The Russians will use a second piece of Cold War rocketry—designed to take spy satellites out of orbit—to push the spacecraft to its ideal orbit of 800km, far above the last wisps of the Earth’s atmosphere.

Then it will unfurl its sails. According to theory, as the solar rays hit the mirrored surface of the sails and then bounce away, they will exert pressure. Even in the pure vacuum of space this pressure will be barely perceptible: five millionths of the push exerted, for instance, by an apple in the palm of a hand.

But under this lighter-than-featherweight touch, the spacecraft will begin to move.
The 100kg object will accelerate at a barely measurable fraction of a millimetre per second, but will gain speed with every second in the sun. By the end of the first day it will have increased its velocity by 160kph. In 100 days, it could reach 16 000kph.

Cosmos 1 is a venture by the Planetary Society—an independent international group of enthusiasts and space veterans—backed by a film and television company called Cosmos Studios and working with the Russian Academy’s space research, Russian contractors and the Russian navy.

Space sailing ships were first proposed in 1924, more than 30 years before the first successful rocket launch.

Rocket fuel is the biggest single cost in a space mission, and the United States, European and Japanese space agencies all have solar sailing projects. The first to go up, however, will be an entirely private venture.

A suborbital test in 2001 failed, but only because the third stage of the rocket failed to separate. The Cosmos 1 team had hoped to launch last year, and then again earlier this year. Launch could still slip to early 2005.

“We had a couple of setbacks in difficulties with the radio system development, and the software testing took longer than planned,” said Louis Friedman, the director of the Planetary Society, who once worked on a Nasa solar sail project. “Also the Russians, with our agreement, kept adding capabilities to the spacecraft. Progress isn’t really slow—developing anything new is a complex process in which hope always exceeds reality.”

The spacecraft has now passed all its electronic tests. The sails and control console, made in Russia, will be packed and shipped to the launch area. Progress will be tracked by Russian ground stations, the US air force and US government agencies. The best hope is that once launched, Cosmos 1 will spiral away from Earth for a month: proof that theorists got their sums right.

The sails could be adjusted like helicopter blades to alter flight direction and speed.

Solar sails are, for the moment, the only hope for interstellar missions. Although far slower than a chemically powered rocket, a space clipper would continue to accelerate as long as there was sunlight. Craft like Cosmos 1 could reach Pluto in five years. The fastest orthodox mission planned so far would take nine years.

Ann Druyan, a founder of Cosmos Studios and the wife of the late astronomer and writer Carl Sagan, said: “If Cosmos 1 succeeds it will be visible throughout much of the world to the naked eye, a signal flare of hope for the wise use of science and high technology. Over the past four years I’ve imagined Cosmos 1‘s vast silvery sails unfurling in space countless times. If it does come to pass, it will be a thing of beauty and a milestone of progress on the long human journey to the stars.” - Guardian Unlimited Â

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