NanoSail-D – A Solar Sail in Space

NASA researchers in collaboration with a team from Ames Research Center are planning to launch a solar sail dubbed NanoSail-D from Omelek Island in the Pacific Ocean during a window extending from July 29th to August 6th. If successful, NanoSail-D will be the first sail in space to be propelled by sunlight, thus not only extending the possibilities of space exploration even further but also making history.

A similar mission was attempted on June 21, 2005 with the launching of Cosmos 1 by the Planetary Society and Cosmos Studios.The spaceship was intended to prove that solar sailing was possible by entering earth’s orbit rather than reaching the stars. Cosmos 1 was supposed to fly into space at the tip of a submarine-launched Volna rocket. Unfortunately, it never did go into orbit since the first stage of Volna rocket didn’t complete its scheduled burn.

NanoSail-D will travel onboard a SpaceX Falcon 1 rocket and is supposed to unfurl four gossamer wings from its pod while in space. When opened the solar sail will spread out to about 100 square feet. The material used for the structure is aluminum and space-age plastic, making it very light-weight as apparent since the entire spacecraft weighs less than ten pounds. A short NASA movie showing the solar sail in action on the ground is available at their website.

The fact that there is no friction in space means that a solar sail-ship can go on and continue accelerating, reaching much greater distances in far less time than a rocket can, which is limited by the amount of fuel it can carry.

“It’s not so much about how far a sail will go compared to a rocket; the key is how fast,” says Edward “Sandy” Montgomery of NASA’s Marshall Space Flight Center. “The Voyagers have escaped the solar system, and they were sent by rockets, but it’s taken more than three decades to do it. A sail launched today would probably catch up with them in a single decade. Sails are slower to get started though. So, for example, between the Earth and the moon, rockets might be preferred for missions with a short timeline. It’s a trip of days for rockets, but months for a solar sail. The rule of thumb, therefore, would be to use rockets for short hops and solar sails for the long hauls.”

Another possible advantage of this technology is using a drag sail as a means to de-orbit micro-satellites that stay in orbit long after they completed their missions, thus constituting a collision risk for spacecrafts. “NanoSail-D will demonstrate the feasibility of using a drag sail to decrease the time satellites clutter up Earth’s orbit. Although our sail looks like a kite, it will act like a parachute (or like a drag sail) in the very thin upper atmosphere around Earth. It will slow the spacecraft and make it lose altitude, re-enter the Earth’s atmosphere and burn off in a relatively short period of time,” further explains Montgomery.

The solar sail concept is interesting not only as a technological achievement but also as an open scientific question. Several years ago the prominent physicist Thomas Gold, a member of the U.S. National Academy of Sciences from Cornell University claimed that a solar sail which isn’t made of a perfect mirror could heat up within seconds and stop moving. Most physicists however believe Gold was wrong in his claim; Gold passed away in 2004 and will not be able to see the first test of NASA’s NanoSail-D which might disprove his theory.

TFOT recently covered a method for generating electricity using the sea as a giant solar-energy collector. It is considered that the technology, termed “Ocean Thermal Energy Conversion” (OTEC), may enable the establishment of an efficient energy storage system across the world, supplying enough energy for our entire planet. TFOT also reported on JAXA’s Space Solar Power Systems (SSPS) Project – aimed at creating the world’s first space-based power generation system, which will continuously absorb solar energy and send it to earth in the form of a powerful laser beam.

More information on NASA’s NanoSail-D can be found at the official Science@NASA website.