Flight testing and simulation of a Mars aircraft design using inflatable wings

Inflatable wings have emerged as an alternate concept for the wing design for planetary exploration aircraft due to the requirement for a minimal packed-volume-to-weight ratio. Previous high-altitude experiments demonstrated the deployment and successful rigidization or pressurization of inflatable wings for flight. Previous low-altitude flight tests also demonstrated high reliability, along with unique capacity for wing shaping to expand flight capabilities. This paper presents two aspects of current development efforts of inflatable wings for Mars exploration: 1)low-altitude flight testing of a concept design of an inflatable-wing Mars aircraft and 2) computational fluid dynamics (CFD) simulations of inflatable-wing geometries. Flight tests were conducted across a range of conditions, including weather and payload. Performance characteristics including stall velocity, maximum velocity and endurance were determined from flight testing and compared to design predictions where possible. Results include the simulation of two different ideal or "smooth" airfoils and two different inflated or "bumpy" wing profiles. Streamlines and velocity profiles were computed for a number of relevant cases to understand the flow field and unique behaviors seen previously in wind tunnel tests of inflatable profiles. CFD and experimental observations suggest that the flow over the "bumpy" profiles has less separation than that of the "smooth" profiles for the low Reynolds number cases studied and that the flow over the "bumpy" airfoils is more unsteady than that over the "smooth" airfoils. CFD results suggest that the presence of the bumps near the leading edge of the airfoil can significantly reduce the dynamic pressures in that region resulting in a loss of lift. Results also suggest that smooth airfoils optimized for certain applications may not coincide with bumpy airfoil with the same baseline profile.