July 14, 2010

Ikaros Achieves Photon Acceleration

An unmanned probe launched by Japan's space agency had a successful test of its innovative solar sail propulsion system, after getting its first acceleration push from sunlight, the agency announced.

Based on observations of the Ikaros solar sail, the Japanese Aerospace Exploration Agency (JAXA) confirmed the probe has received a growing speed boost from light radiated by the sun.

"The small solar power sail demonstrator 'Ikaros,' which successfully deployed its solar sail, was confirmed to accelerate by [the] solar sail receiving solar pressure," JAXA officials said in an update on July 9. "This proved that the Ikaros has generated the biggest acceleration through photon during interplanetary flight in history."

The effect is created by the escalating push of light photons striking the solar sail. When measured together, it adds up to a small continuous thrust that does not require use of fuel by the Ikaros craft.

Engineers used Doppler radar to study the movement of the Ikaros craft. They determined that sunlight is pressing on the probe's solar sail with a force of about 0.0002 pounds of force.

Louis Freidman, co-founder of the Planetary Society, on the society's website, wrote: "This is a significant milestone on their flight "“ probably the next-to-last step before complete controlled solar sail flight is achieved (turning the spacecraft to add or subtract velocity in a controlled manner)."

Ikaros weighs nearly 700 pounds and has thin film solar cells built into its kite-like frame to generate electricity. The sail measures 46 feet by 66 feet. It is the first solar sail to actually be used on an interstellar mission.

JAXA launched the craft in May along with the Venus-bound orbiter Akatsuki, which is due to reach Venus orbit in December. JAXA officials hope to follow Ikaros with an even more impressive solar sailing mission in the future.

Freidman said scientists have long-known that photons of light can be manipulated for acceleration in space, but Ikaros is the first to attempt an interstellar solar sailing flight. "The acceleration by sunlight pressure on spacecraft has been known about ever since the beginning of the space age. It is, however, a new proof of engineering "“ harnessing the force of light pressure force to modify a sail craft's path in a controlled way," he wrote.

Both NASA engineers and the Planetary Society have been working to design and fly their own versions of solar sail craft. The Planetary Society is currently developing the LightSail 1 Mission using a NASA solar sail.


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