Reduction of Structural Mass Fraction for Extreme Solar HALE Flying Wings

Extreme HALE (high-altitude, long-endurance) aircraft typically require very long and thin wings. These super-lightweight wings tend to be highly susceptible to elastic instability (i.e., buckling). The maximum load such wings can sustain before buckling is generally much lower than the maximum load they can experience before yielding. Furthermore, for the critical high-altitude portion of a mission, the gust loads are very small, and the characteristic dimension of the gusts is large compared to a HALE aircraft. However, during ascent and descent, the aircraft must handle much stronger gusts as well as gusts that may be small compared to the aircraft wingspan. Designing for these peak gust loads can substantially increase an aircraft’s structural mass fraction. The goal of this proposed effort is to use inflatable technology to either provide a temporary increase in strength to a flying-wing aircraft that is structurally optimized for the low loads of high-altitude flight, or, alternately, to allow the structure to deliberately buckle and self-recover when it encounters a wind gust. Aurora Flight Sciences, teamed with Vertigo, Inc., proposes to develop wing structures suitable to HALE flying wings that use inflatable components to achieve this goal with no degradation in aircraft performance or reliability.