BIMODAL UNMANNED VEHICLE: PROPULSION SYSTEM INTEGRATION AND WATER/AIR INTERFACE TESTING Antonio Bacciaglia ∗ , Dian Guo ∗∗ , Pier Marzocca ∗∗ , Cees Bil ∗∗ , Alessandro Ceruti ∗ ∗ School of Engineering/DIN Department University of Bologna Forli/Bologna, Italy ∗∗ School of Engineering RMIT University Melbourne, Victoria 3083 Keywords: Unmanned vehicle, Bio-inspired vehicle, Bimodal vehicle, Testing, Transition Abstract A multi-modal UAV capable of sustained aerial flight, locomotion in water and deployment from a tube filled with compressed air is under devel- opment. This paper covers the design and inte- gration process of a CO 2 thruster previously de- signed in a vehicle designed to fulfil mission re- quirements in terms of altitude and velocity after water/air transition. The thruster uses a common CO 2 cartridge available off-the-shelf to acceler- ate water stored inside a water chamber for ef- ficient and sustained thrust. Water is chosen as vectorial fluid since it is available from the sur- roundings. Analytical model, described in the paper, evaluates water to air transition phase in terms of trajectory, reached altitude and velocity. After thruster performances evaluation thanks to the analytical model, an experimental prototype was fabricated and tested for model validation. High speed camera is used to track vehicle transi- tion and Kinovea software exports resulting data from a recorded video to spreadsheet formats for scientific study and post-processing. A compar- ison and discussion of the results as future work is also proposed with areas for improvement and development. 1 General Introduction Nowadays, the Unmanned Aerial Vehicles (UAV) technology can be considered an effective tool which can be exploited for 3D (Dull, Dirty, Dan- gerous) air missions. UAVs can be used for a wide range of applications such as pollution/air data collection, monitoring, photographic and video recording, border surveillance. Also a set of space applications could fit the UAV capabil- ities: several studies on vehicles to explore the atmosphere of planets can be found in literature. One of the new frontiers in the development of UAVs is represented by hybrid or multi-modal UAVs. Such a kind of UAVs is capable to op- erate in different mediums like air and water, air and ground, ground and water. Bimodal UAVs can avoid the use of two unmanned platforms in a variety of missions [1]. Just to provide an exam- ple, the capability of collecting data in sea water and further in the air, in case of chemical/nuclear disaster, could present the advantage of shorten the time required to provide a detailed situation awareness. The missions which can be accom- plished in an effective way by bimodal UAVs does not belong to earth only, but they can be suitable for space missions as well. One single vehicle, which could be used to explore the Mars 1