June 11, 2010

Japan Successfully Deploys Solar Sail

Japanese scientists are celebrating the successful deployment of their Ikaros solar sail.

The 2,100-square foot membrane is attached to a small disc-shaped spacecraft that was put into orbit last month by an H-IIA rocket.

Ikaros will demonstrate the principle of using sunlight as a simple and efficient means of propulsion.

The technique has been long seen as a way to move spacecrafts around the Solar System without using chemical fuels.

The mission team will be watching to see if Ikaros produces a measurable acceleration, and how well its systems are able to steer the craft through space.

The Japan Aerospace Exploration Agency (JAXA) said in a statement that its scientist and engineers had started to deploy the solar sail as of June 3.

JAXA said on June 10 that confirmation was received that the sail was deployed successfully.  It added that some thin-film solar cells embedded in the membrane were even generating power.

The deployment occurred about seven 4,349,000 miles from Earth.

The principal behind the solar sail is simple.  Photons falling on a highly reflective, ultra-thin surface will exert a pressure. The force is tiny but continuous, and over time should produce a considerable velocity.

Solar sails will never replace conventional propulsion systems like chemical thrusters, but they do have the potential to play a much greater role in certain types of space missions.

Louis Friedman, from the space advocacy group The Planetary Society, is a big supporter of the technology.  The society's LightSail-1 is a smaller mission than Ikaros that could launch by the end of this year.  He told BBC News that "the potential that we all seek is the ultra-lightweight, very fast spacecraft that doesn't use fuel. That's the future of interstellar travel; that's the long-term goal. The intermediate goals are to be able to use this technology to 'hover' in interplanetary space at particular points for monitoring, say, the Sun or monitoring the Earth's geomagnetic poles or magneto-tail; and then also to fly between the planets without using fuel."

Some satellites in geostationary orbit above the Earth already use flaps on the end of their solar panels to catch the pressure of sunlight to maintain their correct attitude.

This leads to considerable saving on the fuel that would otherwise have to be sent surging through the satellite's thrusters, and operators have found this strategy can extend the longevity of some missions by many months.

However, deploying a large membrane in space is a challenging task.

The circular Ikaros launched with the sail wrapped around it.  The plan was to unbutton the four weighted corners of the membrane and allow them to fly outwards as the central module turned. 

Japanese scientists now hope they can control the spinning film.  If the sail starts to become unstable, then it could start to bend and fold, which would ruin the experiment.

Ikaros was a piggyback payload to Japan's Venus orbiter, Akatsuki.

The two crafts were launched into space on May 21st from the Tanegashima Space Center.

Akatsuki is on schedule to arrive at Venus in December.  Key goals include findings definitive evidence for lighting and for active volcanoes.


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