The Air Force has announced that it will do its part for economic stimulus by spending $400 million on a dirigible designed to float 65,000 feet above the Earth, where it will provide constant surveillance of an area (such as the Afghanistan-Pakistan border). ISIS (Integrated Sensor Is the Structure) is being billed as a cross between a satellite and a spy plane, kept aloft by helium and powered by hydrogen fuel cells that are recharged with solar panels. The thing will remain in place for up to ten years providing, as one Air Force scientist gushed, "constant surveillance, uninterrupted." If successful, the Air Force would like to see a whole fleet of these things. DARPA has signed on, agreeing to deliver a prototype by 2014.