the unmanned craft is designed to orbit the earth and land like one of nasa s space shuttles. it s reusable. it s carrying a prototype solar sail, let s hope sails can use the sunlight to propel spacecraft in the future without using any fuel which is heavy and expensive. call it a wrap. david letterman says good-bye. the late shows will never be the same again. more on that when we come back. part adventure. it s part geek and part chic. it s part relaxation and part exhilaration. it s part sports car and part suv. and the best part? the 2015 gla. it s 100% mercedes-benz.