A demonstration intended to show the viability of "propellant-free" space transport in the near future is planned for 2014, with the launch of the world's largest solar sail. NASA's Sunjammer will deploy a huge, ultra-thin solar sail once in space, and be able to use the pressure of sunlight on that sail to propel the device.
Using the energy of the sun to propel a sail has already been successfully used on a smaller scale, as an earlier forerunner to the Sunjammer, the Nanosail-D, demonstrated in 2011. The Nanosail-D deployed a 100 square foot sail and orbited on a 240 day mission around the Earth.
But this newest iteration of the solar sail is huge in comparison. The Sunjammer is seven times the size of any previous solar sail design, and features a sail measuring over 120 feet on each side. This enormous sail is capable of catching the 'solar wind' from an area measuring almost a third of an acre.
Weighing in at 70 pounds, the Sunjammer is "about the size of a dishwasher" when folded up, and is designed to be deployed, along with its 175 pound support module, by a rocket in low-Earth orbit. Once the device begins unfolding, the sail, made from Kapton, will unfurl to the working size of about 13,000 square feet. Kapton is an ultrathin reflective film (just 5 microns thick) made by DuPont that is both strong enough to act as a sail, while also light enough so that it doesn't add drag to the device.
The maximum thrust from a solar sail, even at this large size, isn't much, with NASA stating that Sunjammer will experience only about 0.01 newton of thrust, but for propelling devices for unmanned data gathering and monitoring missions, it could be just what's required.
The Sunjammer project is being developed by NASA and L'Garde Inc., with an expected launch as a secondary payload on a Falcon 9 rocket in 2014. The mission is to the Earth-Sun Lagrange Point 1, about 1.8 million miles from Earth, and the Sunjammer team expects to be able to run through a number of tests on the equipment on the journey.
And for those of you who recognize the name Sunjammer from the short story by Arthur C. Clarke, about a solar yacht race in space, you'll also appreciate the other payload going up on the mission: The cremated ashes of Star Trek creator Gene Roddenberry and his wife Majel Barrett Roddenberry will be taking a deep space journey on the Sunjammer's maiden voyage.