Development of UV-curable inflatable wings for low-density flight applications

The concept of an unmanned spacecraft launched to Mars or Venus to release an aircraft designed to fly an exploratory mission is nearing reality. Recent projects involving unfolding rigid-wing aircraft have demonstrated high-altitude, low-density flight capabilities. An alternate approach for the wing design is an inflatable composite wing impregnated with a UV-curable resin. With this approach, wings are pressurized for deployment, then rigidize with exposure to UV radiation from the sun. Once rigid, the wings no longer require pressurization to maintain their shape. A project named BIG BLUE (Baseline Inflatable-wing Glider Balloon-Launched Unmanned Experiment) to develop and verify technologies for inflatable, UV-rigidizable wings culminated in a demonstration flight on May 3, 2003. The flight experiment included three stages: 1) balloon-launched ascent to 55,000 ft, 2) deployment of inflatable-rigidizable wings and continued ascent to 89,603 ft and 3) release from the balloon and return to earth under a parachute. The test article consisted of an unmanned aircraft including the folded wings, an inflation system, microprocessor control, sensors, cameras, GPS and communications radios. In this paper, aspects of the UV-curable composite wing design are presented including stress and thermal analyses and laboratory tests to determine cure times. Results of the demonstration flight are also included.