Officials developing a lighter-than-air unmanned vehicle that could be used as a communications relay, peacekeeper or weather observer have completed a design feasibility study and are ready to begin construction of a demonstration vehicle, contractor Lockheed Martin announced today. All the technologies were validated during the concept feasibility phase, which began in 1998, a company release says. The unnamed air vehicle will operate at an altitude of 21 kilometers, or 70,000 feet. This is above the jet stream and severe...