This is an excerpt from EERE Network News, a weekly electronic newsletter.

June 30, 2010

Japan Successfully Deploys a Solar Sail in Space

The Japan Aerospace Exploration Agency (JAXA) has successfully deployed a solar sail in outer space. While solar energy has successfully powered small cars and airplanes, nobody has yet managed to use the sun's energy to propel a spacecraft, although that goal is now within reach of JAXA. The agency's Small Solar Power Sail Demonstrator, or IKAROS (Interplanetary Kite-craft Accelerated by Radiation of the Sun), was launched on May 10 and passed its initial operation check on May 21. On June 3, the agency began deploying the solar sail, and on June 10, JAXA confirmed that the solar sail was successfully expanded.

A low-quality photo of a large square of foil-like material floating in space. The square is supported with four masts that run from a central cylinder to each corner of the square, and part of the center of the square is cut out, revealing the support structure.

Japan’s space agency used a small tethered camera to capture this photo of its deployed solar sail. Enlarge this image.
Credit: JAXA

The concept of a solar sail, which could use the pressure of sunlight to propel a spacecraft, has long been a dream of both scientists and science fiction writers. Though the concept is roughly 100 years old, IKAROS will be the first practical demonstration of the technology. The sail was deployed by spinning its cylindrical launch vehicle to 25 rotations per minute, then allowing angular momentum to spread the sail out from that central hub to form a square measuring about 35 feet on each side. The sail is made of an extremely thin, flexible plastic and includes thin-film solar cells on part of its surface to generate electricity. Over the next five months or so, JAXA will attempt to prove the technology by accelerating the craft and steering it toward Venus. See the JAXA press release and JAXA's IKAROS Web site.

Meanwhile, European engineers are aiming to set another first by flying a piloted solar-powered airplane through one day and one night. The Solar Impulse HB-SIA is scheduled to take off on the morning of July 1 on a flight that will continue until the morning of July 2. During the day, the aircraft will charge its lithium-polymer batteries, then increase the amount of available energy by climbing to an elevation of nearly 28,000 feet. During the night, the craft will run on battery power while slowly descending, greeting the morning at an elevation of just under 5,000 feet. The Solar Impulse HB-SIA is essentially a flying wing, with solar cells covering its entire 207-foot wingspan. The craft is made from carbon fiber composites and is powered by four propellers, each driven by a 7-kilowatt motor. The solar-powered aircraft is meant to test the flight characteristics and performance of the technology in preparation for a future craft that will be designed to fly around the world on solar power. See the Solar Impulse blog, the Web site, and a fact sheet on the Solar Impulse HB-SIA (PDF 1.3 MB). Download Adobe Reader.