SVILUPPO CONCETTUALE DI UN ENDOREATTORE BIPROPELLENTE AUTOPRESSURIZZATO A PEROSSIDO DI IDROGENO ED ETANO

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In recent years space missions become more ambitious so the need for reducing the costs and increasing the capabilities of rocket systems through the enhancement of their propulsion performance, safety and reliability represents a major aspect in the development of competitive space engines. A variety of factors have resulted in an increasing interest in the exploration of alternatives to widely employed cryogenic and hypergolic propellant combinations. These factors include heightened sensitivity to cost, environmental concerns and personnel protection from the hazards associated with the use of present highly toxic propellants. The current standard in high-performing, storable bipropellants is the combination of nitrogen tetroxide (NTO) and hydrazines (N2H4, MMH and UDMH); these propellants are extremely toxic, carcinogenic and explosive so they presents disproportionately high costs especially for small and medium size satellites. In this range of satellites, hydrogen peroxide (HP, H2O2) is widely recognized to be one of the most promising non-toxic (‘green’) storable propellants due to its lower total costs. Hydrogen peroxide used as monopropellant has a specific impulse of the order of 180 seconds but used as oxidizer in a bipropellant engine it has a specific impulse of the same order of a NTO- N2H4 system. At the moment Alta S.p.A. is working on the development and testing of advanced catalytic beds for H2O2 decomposition and their application to monopropellant rocket thrusters. The expertise acquired in this sector gave the possibility to analyze and assess the propulsive and operational performance of innovative green bipropellant thrusters with Fuel Vapour Pressurization (FVP) of hydrogen peroxide and ethane (C2H6), where the catalytic reactor provides the oxidizing stream for C2H6 combustion. Fuel vapour pressurization systems consists in the use of just one tank for both propellants and it exploit the high vapour pressure of ethane to transfer both the fuel and the oxidizer into the combustion chamber. This pressurization system provides a significant reduction of the costs and of the overall system mass. The present thesis is concerned with the conceptual analysis of the FVP system, in particular with the analysis of the tank temperature and pressure drift, and the preliminary measuring of a 50 N thruster prototype. Chapter 1 is an introduction about the performances of hydrogen peroxide bipropellants rockets while in the chapter 2 are showed the physical and chemical properties of hydrogen peroxide and ethane. In chapter 3 is illustrated the analysis of the pressure drift of the tank whit the hypothesis that the oxidizer-fuel ratio remain constant during the mass extraction from the tank. Chapter 4 shows the same analysis of chapter 3 but without the hypothesis about the constancy of the oxidizer-fuel ratio; it also illustrates the differences in the performance with the choice of the mass regulation system. Chapter 5 e 6 illustrate the design of the bipropellant rocket and the performance’s analysis. The first appendix describes the method used for evaluate the viscosity and the thermal conductivity of the mixture of gas in the combustion chamber, useful to calculate boundary layer and thermal parameters. The thesis work is a part of an Alta’s wider project end it has been carried out under the supervision of Prof. Luca d’Agostino, eng. Angelo Pasini and eng. Lucio Torre