PUMP FED PROPULSION SUBSYSTEM FOR A TELECOM PLATFORM - PRELIMINARY DESIGN AND PERFORMANCES ANALYSIS

In the current state of art, the bipropellant chemical propulsion subsystem for telecom platforms is commonly pressure fed for both the apogee kick and the station keeping manoeuvres. A pressure fed system is characterized by the presence of the Pressure Control Assembly, which includes all the components (e.g., pressurizing gas tanks, valves, piping, etc.) needed to maintain the propellant tanks pressure at a fixed value, typically not over 24 bar. Moreover, the latter pressure needs to be high enough to feed the engines considering all the pressure drops due to the components. As a result, the pressure fed system has a lot of bulky components and this can be an issue for two reasons: the system mass and the number of components. The first one should be as small as possible to maximize the mass dedicated to the payload, while the second one has to be minimized in order to reduce the costs. The goal of this project is to explore the possibility of a full pump fed system, feeding both the main engine and the thrusters, both simultaneously and separately. This system needs to keep lower pressures in the whole fluidic line while maintaining the same performances of a pressure fed system, as highlighted by the first test campaigns. This kind of architecture allows also to reduce the mass of the system and the number of bulky components. The chosen configuration consists in one electric driven pump for each line, chosen thanks to tests and trade-off, in order to keep separate fuel and oxidizer, limiting the risk of contamination. Moreover, one pressure damper for each line is needed with the aim of damping the pressure ripples caused by the pump functioning. This reason is not the only one that leads to the use of pressure dampers, in fact they are essential also to allow the functioning in pulse width modulation of the thrusters. To prove the correct functioning of this architecture an EcosimPro model of the system has been realized. Initially the apogee kick motor and the thrusters models have been made and analyzed with the aim of doing a preliminary design of the fluidic lines and their components. After that these two models have been fused together to realize the model of the complete system. This latter schematic allows to do the final analysis and to define a more precise design of the fluidic lines. Moreover, the system operations have been defined and the obtained results have shown a good agreement with the performances of the reference engines data sheets, satisfying all the requirements of the components (e.g., pump inlet pressure, engines inlet pressure and mass flow rate, etc.).