As part of our continued investment, we recently open-sourced our solar-powered aircraft design methods, named Facebook High Altitude Long Endurance (FBHALE), after presenting two papers on the multidisciplinary optimization (MDO) based technology at the American Institute of Aeronautics and Astronautics (AIAA) Aviation Conference. By open-sourcing this design framework, we can help the rest of the HAPS community optimize during the design process as well.
The need for MDO
Recent progress in battery technology, solar-cell efficiency, and composite materials has dramatically increased the feasibility of solar-powered perpetual flight. However, even with these improvements, ensuring that a solar-powered aircraft can use as little power as possible to perform in even the harshest conditions — such as the winter solstice — still demands the highest aircraft performance. This means maximizing aerodynamic performance (lift-to-drag ratio) and minimizing structural mass to support maximizing energy storage capability. However, increasing aerodynamic performance is detrimental to overall structural weight, and vice versa. Therefore, careful trade-offs need to be considered to ensure optimal system performance.
We developed an MDO design framework to address these challenges early and to avoid redesigns. The design process is inherently an optimization opportunity and, since we are looking for the best aircraft design that can achieve our target requirements, we are utilizing an optimization routine to both maximize objectives and satisfy constraints.
This framework incorporates low-speed aerodynamics, composite-structure design principles, and all the simplest physical models that still rely on relevant physics.
Overall Logic, Disciplinary Modeling
Because of the numerous variables involved in the design process of high-altitude aircraft, this work can be challenging. In the figure below, we have illustrated our strategy to effectively handle the number of dimensions in this phase.