Rotary-Wing-UAVs-for-Microgravity-Experiments

In recent years, a boom in space exploration around the world, has increased the demand for reduced-gravity (or microgravity) testing platforms for scientific research, payload and equipment testing and educational purposes. Reduced-gravity tests can either be done in-situ (on the International Space Station, CubeSats, etc.) or on Earth (in drop towers, using aircraft flights, etc.). However, all the currently available options are expensive and have limited accessibility. Unmanned aerial vehicles (UAVs) can fulfil the need for a cheap, easily accessible reduced-gravity test platform. This study aims to investigate the feasibility of rotary-wing UAVs as microgravity test platforms for simple payloads for education and scientific research on reduced-gravity. This study uses a simulation-based approach to leverage the Unity Game Engine to model a simple quadcopter for various 1D microgravity manoeuvres. Flights are conducted with varying drag coefficients, take-off weights and a range of reduced-gravity levels in the simulation and key parameters are measured and analysed. \ \ Through comparisons with the maximum speed, ceiling altitudes, thrust, power and energy capabilities of cheap, readily-available rotary-wing UAVs it is found that such flights are also feasible in real-life operations. The study has found that a simple quadcopter can provide microgravity level of 0 g with a quality of $10^{-2} g$ for a duration of 1.5 s and a quality of $10^{-1} g$ for a duration of 3 s despite the presence of large drag forces. Further work could include an investigation into the attitude stabilility (pitch, roll and yaw) of the UAV during these flights to analyse the type of payload that could be safely tested on such a platform. Additionally, more complex algorithms with less noise sensitivity could be chosen and automated tuning could be investigated. This study could be directly used in microgravity research and indirectly applied to battery optimization strategies for UAVs used for delivery, surveillance, etc. The method used in this study could be useful for digital twin creation of more rotary and fixed-wing UAVs.