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Tuesday, 14 May, 2002, 08:30 GMT 09:30 UK
Starship dream moves closer
Solar sail (BBC)
Solar sails could make space travel much cheaper
test hello test
By Helen Briggs
BBC News Online science reporter
The first attempt to fly a craft pushed by the light of the Sun is on target for an autumn launch.

Experts at the American space agency (Nasa) and the European Space Agency will be watching closely to see if the low-budget mission succeeds.

In a privately sponsored venture, the Planetary Society in the United States wants to send a solar sailing ship into orbit around the Earth.

Solar sailing is the technology that can take us to the stars

Dr Louis Friedman, Planetary Society
The experiment could pioneer a new generation of space travel using spacecraft that are propelled by the our star's energy in the same way that ships on the sea are pushed by the wind.

The technology relies on ultra-thin, mirror-like solar sails that trap individual particles of light from the Sun.

In theory, the photons should transfer their energy to the sails, pushing the spacecraft along.

Destination stars

Sci-fi fans have long dreamed of using such a means to explore the stars.

It is conceivable that a spacecraft might be able to travel, say to Mars, propelled by conventional fuel.

Omega nebula captured by Hubble Space Telescope (AP/Nasa)
Even deep space may be accessible
To travel further, however, would stretch the limits of chemical propulsion as well as human imagination.

The idea is to use energy from the Sun to power spacecraft travelling to the outer planets and beyond.

Sunlight would become too weak beyond the realms of Jupiter but one theory for interstellar travel is to direct space lasers at the sails.

The principle sounds fantastical but there is now genuine enthusiasm within the science community that solar sails will one day make voyages into deep space a reality.

Dream technology

The Cosmos 1 mission will take the first step towards the dream of a free ride through space.

The project is a joint venture of the Planetary Society and Cosmos Studios, a group of film-makers and writers set up by the widow of scientist and writer Carl Sagan.

The craft will begin its journey on board a rocket fired from a submarine in Russian waters.

If all goes to plan, the solar sail spacecraft will separate from the rocket where it will unfurl and fly for a few weeks or months around the Earth pushed by the Sun.

Solar sailing: The principle
Light particles from the Sun hit the surface of the sail
They bounce off the reflective surface, pushing the sail and giving the spacecraft thrust
Turning the sail at different angles to the Sun steers the craft
Planetary Society executive director Dr Louis Friedman gave an update on the mission at a meeting of the Royal Astronomical Society in London, UK.

He said the Russian-built spacecraft had passed preliminary tests.

"Solar sailing is the technology that can take us to the stars," Dr Friedman told BBC News Online. "That's the dream of solar sailing."

He said they were starting "in the harbour of Earth orbit", where they wanted to demonstrate the technology of using sunlight to manoeuvre the craft.

"In future missions, we have the goal of being able to get out of Earth's orbit, go on to interplanetary space and ultimately out to interstellar missions," Dr Friedman, a former Nasa scientist, added.

Scientific applications of solar sails include sending a spacecraft to orbit the Sun or perhaps even to deflect an asteroid on a collision course with the Earth.

Professor Colin McInnes, who organised the meeting, heads a programme at Glasgow University that is investigating solar sail technology.

He said the first "serious science mission" using solar sails was much closer than many people imagined.

Cosmic message

He said a mission to collect samples from asteroids or icy comets was a possibility.

"Because the solar sail propulsion is open-ended you could use the same spacecraft - the same set of instrumentation - to hop from one asteroid to the next, doing comparative science," Professor McInnes told BBC News Online.

As well as lofty scientific goals, there is strong commercial interest in developing solar sailing ships.

By skimping on rocket fuel, they could make the most expensive form of transportation ever invented a little cheaper.

One US company - Team Encounter - plans to send a solar sail loaded with photographs, messages and DNA from fee-paying customers into interstellar space.

The cost of leaving a cosmic message in a bottle is advertised at a paltry $50 (35).

See also:

12 May 00 | Sci/Tech
Setting sail for the stars
16 Feb 02 | Boston 2002
Humans will 'sail to the stars'
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