IKAROS: The First Step to Interplanetary Travel

Fuel is not only a problem for travel on Earth. In order to successfully propel a rocket into space, enormous amounts of fuel are needed. In fact, 95% of a rocket's weight at launch is from fuel. The Solar Sail concept, which has been discussed as early 400 years ago, seems to be the clear solution to such an issue now that the technology has finally been developed.

In layman's terms, solar-powered spacecrafts use the energy of the sun in order to propel through space. This eliminates the need of an engine. These spacecrafts only require three things: a continuous force exerted by the sun, an enormous, ultra thin mirror, and a separate launch vehicle. The electromagnetic radiation contained within light exerts a force on the sails. The photons given off by the sun reflect off of the giant mirror. In the vacuum of space, even a small collision will cause something to move. The bigger the mirror, the more collisions and the faster the spacecraft moves. This method causes the spacecraft to move about 5x faster than a traditional one, all while using significantly less energy.

The next step in solar sail travel is contained in the IKAROS project. The IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), will use a Solar "Power" Sail. The difference between this and a solar sail is that the "power" sail collects electricity in the solar cells of its membrane. But, like the solar sail, it still gets accelerated by the radiation of the sun. The advantage of the "power" sail is that it creates (to a certain extent) a "hybrid" engine. Space missions with such sails will be much more flexible as the engine can rely on both photon acceleration and ion-propulsion engines driven by solar cells. Hopefully, scientists believe, the continuation of research on solar "power" sails will yield much longer space travel missions that would ultimately result in interplanetary travel.

The IKAROS will launch later in 2010 in order to test the effectiveness of the sails. The shape of the membrane is square, with a diagonal distance of 20m. It is made of polyimide a mere 0.0075mm thick. In addition to the thin film solar cells, the steering devices and dust-counter sensors are fitted to the membrane. The sail will rotate at 20rpm for several weeks in space in order to generate solar power with a minimum success level. Within a year, sail navigation and acceleration will occur at full success level.

http://science.howstuffworks.com/solar-sail1.htm
http://www.jspec.jaxa.jp/e/activity/ikaros.html
http://en.wikipedia.org/wiki/Solar_sail