Propulsion system design of the LuNaDrone

The LuNaDrone is a liquid propelled and compact size drone, able to fly autonomously. Its mission is the exploration of lunar caves since they could potentially represent shelters for human life on the Moon, guaranteeing protection from radiations and impact of micrometeorites. This thesis is focused on the search for an actual working design for the LuNaDrone propulsion system. A preliminary study on this topic has already been done by Gabriele Podestà in his thesis, which provided for a vague idea of how the propulsion system should have been. The first part of this dissertation is about a brief mission overview and a presentation on how the spacecraft had already been designed. Consequently, is presented a new 50N main thruster design, in collaboration with T4i, which follows the ArianeGroup 20N canted nozzle concept. It will have a completely custom combustion chamber, with propellant inlet perpendicular to the nozzle outlet. Having this new configuration for the main engine permits to design a completely new propellant tank, which will no longer be toroidal but cylinder shaped. It will consist in two pieces, the container and a cap, in order to insert a separation element between the pressurant and the propellant. Then, an almost definitive and simplified design for the fluidic line is analyzed, choosing a COTS product for each component, whenever it is possible. Knowing the performances of each valve, the various pressure drops are determined and the resulting minimum propellant tank pressure is calculated. Subsequently, the main bell nozzle is optimized in terms of length, analyzing how the decrease in expansion ratio would negatively affect specific impulse, but would greatly increase the mass of storable propellant. In the end, a primary external structure is modelled and the attitude control system is designed. It has been calculated the minimum required thrust to provide, aiming to compensate the unwanted couples; furthermore, the maximum firing time has been determined, in order to meet the rotation angle precision and the angular velocity requirements.