Scientists ponder the question, “What advances in power technology are required to send human and robotic explorers throughout the solar system?” Human missions beyond Earth’s neighborhood will require power not only for onboard systems, but also for propulsion and for systems to support humans when they arrive wherever they’re going. “To pursue ambitious human missions across the solar system, perhaps returning to the Moon, perhaps going on to Mars, will require hundreds to a thousand kilowatts on the surface and hundreds to thousands of kilowatts for transportation systems,” says John Mankins, chief technologist for the Advance Systems Program at NASA headquarters. You can’t just plug into the nearest electrical outlet, he added. You have to bring your own power source. Ideally, you’d like to find something that could provide power for both propulsion and operations.