Design and Development of a Transition Propulsion System for Bimodal Unmanned Vehicles

An impulsive thruster propulsion system that could be used in a multi-modal UAV capable of sustained aerial flight, locomotion in water and deployment from a tube filled with compressed air is under development. This paper covers the design and optimisation process of the propulsive system, as well as its modelling with analytical and CFD simulations to predict the performances. The system is designed to fulfil vehicle mission requirements in terms of altitude and velocity after water/air transition. The thruster uses a common CO₂ cartridge available off-the-shelf to accelerate water stored inside a water chamber along with an inflator to activate and regulate the mechanism remotely for efficient and sustained thrust. Water is chosen as vectorial fluid since it is available from the surroundings. Water chamber sizing process uses an analytical model calibration through CFD approach to refine an analytical model and predict propulsion performances. After thruster sizing, an experimental prototype was fabricated and tested for model validation. A comparison and discussion of the results as future work is also proposed with areas for improvement and development.