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Space yacht Ikaros ready to cast off for far side of the sun

Interplanetary cruise of Japan's solar-powered 'sail craft' aims at deeper knowledge of Venus

The space craft Ikaros with its 20-metre sail, will be driven forward by both photon propulsion and solar power generation. Photograph: Jaxa

Japan hopes to turn the wildest fantasies of science fiction into reality today with a "space yacht" that will draw on the power of the sun to take it to Venus and, perhaps, far beyond.

A Mitsubishi H-2A rocket carrying Ikaros (an acronym for Interplanetary Kite-craft Accelerated by Radiation of the Sun) is set to blast off from Tanegashima island in south-west Japan at 6.44am local time.

The long-awaited launch is seen as part of a mission that could change the course of interplanetary exploration.

If it is successful, Ikaros will be carried through deep space at high speed with the help of a 20-metre sail, propelled by the pressure from solar particles.

The flexible membrane sail, which at 32.5 micrometers is about half the thickness of a human hair, is covered with thin-film solar panels that will create a hybrid of electricity and pressure, according to Jaxa, the Japanese space exploration agency.

Solar photons will bounce off thousands of tiny mirrors to give Ikaros the thrust it needs to complete manoeuvres such as rotating and hovering.

"This will be the world's first solar-powered sail craft employing both photon propulsion and thin-film solar power generation during its interplanetary cruise," Jaxa said on its website.

Although the name of Japan's craft may give rise to anxiety (Icarus, the figure from Greek mythology, having fallen into the sea after flying too close to the sun) Jaxa officials say they are confident the high-tech version will stick to its planned trajectory.

The craft will spend a few weeks rotating before unfurling its sail. If all goes to plan, the craft will use draw on the energy provided by the sun's photons to gather speed during its six-month journey. Experts believe that by developing hyper-powerful sails drawing on laser light instead of sunlight, solar yachts could one day reach speeds of 500,000mph.

After passing Venus, Ikaros is expected to continue its voyage for three years towards the far side of the sun, although contact is likely to be lost after a year.

Jaxa officials say that, if the technology proves viable, they could send a similar craft, Akatsuki, to Jupiter by 2020.

That mission could deepen our understanding of how Venus, thought to have once resembled Earth, became the mysterious, cloud-covered, planet of today. The probe is equipped with instruments that will observe the planet's atmosphere from distances of between 186 miles and 49,710 miles.

"Once we can explain the structure of Venus, we will be able to better understand Earth," said Akatsuki's project scientist, Takeshi Imamura. "For example, we may discover the reasons that only Earth has been able to sustain oceans, and why only Earth is abundant in life."

The $16m project will be the first to deploy the new technology deep in space. Previous space yachts have achieved no more than orbiting Earth, while Nasa and Europe's space agency appear to have resigned themselves to losing out to Japan in the race to test solar sails in outer space.