'Sunjammer,' the largest solar sail to date, will set out for space in 2014

In the vacuum of space, solar sails substitute radiation from the Sun for the wind used by earthbound sails. In 2014, NASA will launch Sunjammer, the largest solar sail yet: each side measures 124 feet, made of material just 5 microns thick. While Sunjammer has been in the works for some time — and far smaller solar sails have gone up in years past — Space.com recently profiled the project, which ultimately could let ships move through space without needing expendable fuel.