High-flying airships could be used as a cheap alternative to satellites, but their propulsion systems and transmitters need more power than solar panels can deliver. The Lawrence Livermore National Lab in California thinks radio energy can help (US 2004/0156400).
A millimetre-band transmitter beams a megawatt of radio energy at an airship hovering at an altitude of 20 kilometres, using a 5-metre water-cooled dish to focus the beam. The beam passes through the fabric of the balloon and onto a layer of foil, which reflects it onto an antenna. There it induces an alternating current that is rectified to produce…
