For many military, civilian, and commercial applications, unmanned aircraft flying at high altitude with long endurance offer advantages over satellites. These advantages include substantially lower costs for design, construction, and launch. Such aircraft may function as reusable, relocatable, geostationary satellites operating within the atmosphere. We are working for the Ballistic Missile Defense Organization to develop unmanned aircraft platforms for protecting our military forces and our allies from attack by theater ballistic missiles. A team of engineers from AeroVironment, Inc., and LLNL have designed and recently completed flight testing of a solar-powered airplane called Pathfinder. The Pathfinder is a flying testbed for proving key technologies, critical system integration approaches, and flight control issues essential to achieving solar rechargeable flight at high altitude. Fuel cell technology has been demonstrated to the point that unitized rechargeable fuel cells are possible. Such an energy-storage system weighs less than a third the weight of the best rechargeable batteries available. The next step would be to build a plane like Pathfinder that has wing dimensions that can accommodate the weight of the rechargeable energy-storage system while enabling it to operate continuously at altitudes (20 to 25 km).
On February 4, 1994, we successfully flight tested the ASTRID rocket from Vandenberg Air Force Base. The technology for this rocket originated in the Brilliant Pebbles program and represents a five-year development effort. This rocket demonstrated how our new pumped-propulsion technology--which reduced the total effective engine mass by more than one half and cut the tank mass to one fifth previous requirements--would perform in atmospheric flight. This demonstration paves the way for potential cost-effective uses of the new propulsion system in commercial aerospace vehicles, exploration of the planets, and defense applications.
July 1994 in PDF format (1,200K)
and LLNL Disclaimers