The next generation of spacecraft will travel faster than ever before. But they might not be propelled by rockets. If Dean Alhorn has his way, they'll be powered by light. Alhorn is an engineer at NASA's Marshall Space Flight center. He designs solar sails. They're basically big silver kites in space that are pushed along by the sun's rays. And Alhorn says they might change spaceflight in the very near future.Produced by David Levin. NOVA is produced by WGBH in Boston. Funding for NOVA is provided by ExxonMobil, David H. Koch, the Howard Hughes Medical Institute, the Corporation for Public Broadcasting, and public television viewers.Learn about other new types of propulsion that NASA is testing, and how they might help us get to Mars. Go to pbs.org/nova/sciencenow