Sea recovery system for small UAV

This report explores the feasibility of a new sea arrest system in which a UAV is arrested by a parasail attached to a ship, and aims to obtain the optimal parasail sizing for the system through aerodynamic testing in a wind tunnel. Extensive literature review was conducted to evaluate the advantages and disadvantages of current sea arrest systems such as the Skyhook used for the ScanEagle, which illustrates the relevance of having a parasail arrest system in the market. The main advantage of the parasail arrest system is that it is able to accommodate larger UAVs with higher approach speeds. In the experiments, the dimensions of the ScanEagle was used as a reference for the calculations. The rig for the wind tunnel testing was assembled manually, along with a scaled model of the parachute and parasail to be tested. Several setups were used during the wind tunnel testing to ensure the accuracy of the data obtained. The mechanism and aerodynamics of the parasail arrest system was also explained using free body diagrams. Through aerodynamic testing of the parachute and parasail, it was observed that the parasail had a significantly higher drag coefficient compared to the parachute. Based on the scaled down models, the CD value of the parasail was found to be 2.727 compared to that of the parachute which was only 0.645, giving a performance increase of more than 300%. This is beneficial to the system as a higher CD value will lead to a higher drag force experienced, assuming the planform area for the parachute/parasail is the same. The drag force will assist in decelerating the UAV, and having a larger drag force means that a smaller parasail could be used in place of the parachute. Furthermore, due to the airfoil shape of the parasail’s canopy, the parasail experienced lift which will allow it to partially carry the UAV’s weight, thus reducing the impact load during the arrest. This will prevent it from crashing into the ship, therefore ensuring a safe recovery process. As there were additional benefits of using a parasail in the arrest system such as the higher drag coefficient and lift force present, it was concluded that the parasail was a more efficient option to use in the arrest system compared to the parachute. The optimum parasail sizing was then calculated based on the ScanEagle’s dimensions.Bachelor of Engineering (Aerospace Engineering