Scaling sediment mobilization beneath rotorcraft for Titan and Mars

Abstract

Using rotorcraft to explore extraterrestrial bodies will allow future missions to explore terrain that is inaccessible to traditional lander/rover missions, and will enable spacecraft to explore much larger distances than previous missions. The upcoming Mars 2020 Rover mission will include the Mars Helicopter (named Ingenuity), a small ( < 2 kg) counter-rotating co-axial vehicle, which, if successful, will be the first rotorcraft to fly on a non-terrestrial body. The Dragonfly mission, recently selected through the NASA New Frontier’s program, is expected to fly a much larger vehicle on Titan ( ∼ 750 kg) arriving in the early 2030s. On Earth it is commonly observed that both sub-scale and full-scale rotorcraft can mobilize sediment, to varying degrees of magnitude, when a vehicle is operating over regolith. In order to determine the feasibility of performing sediment mobilization experiments (e.g. saltation investigations) beneath a rotorcraft through intentional sediment mobilization (due to the wake produced by the rotating rotors) for future missions, the scaling of aerodynamic and aeolian parameters should be accounted for. Furthermore, in an extreme case, this analysis can also be used as a low-fidelity method to begin to understand any potential risk associated with brownout (large-scale sediment mobilization due to the helicopter rotor wake) to the rotorcraft itself. In this work, a scaling analysis is presented that allows a vehicle designer to quickly investigate the magnitude of sediment mobilization beneath a rotorcraft, without requiring detailed CFD simulations. The analysis confirms that the upcoming Mars Helicopter and Dragonfly missions could be used for sediment mobilization experiments.