The Defense Advanced Research Programs Agency (DARPA) will soon be awarding a contract to develop an unmanned aircraft called the Vulture that's capable of flying for five years at a time without stopping, according to the aviation magazine Flight.

Essentially, the Vulture is a satellite released into the atmosphere and not into space.  But unlike satellites, the Vulture will have to maintain enough power to overcome the Earth's gravitation pull.

Specifications for the Vulture include the ability to remain in flight for over five years at a time, while performing intelligence, surveillance, reconnaissance, and communication missions. It must also be capable of carrying a 1,000-pound payload and withstand the heavy winds that occur at 60,000 to 90,000 feet - the altitude the Vulture is expected to remain in.

Since DARPA has ruled out the use of anything radioactive or blimplike to power the Vulture, contractors looking to develop the technology will likely propose energy sources derived from fuel cells or solar panels. Advancing the development of these technologies will, with any luck, further advance their widespread use in a myriad of commercial applications.