Problem Statement
The present report aims to analyse the design of a liquid blow-down propulsion system based on LOX-RP1 to be operated in vacuum. Firstly, an overview of the literature concerning nozzle losses, uncertainties in metallic additive manufacturing and blow-down architectures is illustrated. Subsequently, the nominal design of the entire propulsion system is performed, rigorously discussing the technical choices behind the design of the architecture, nozzle, combustion chamber, injection plate, feeding lines and tanks. The constraints set in the technical specifications are taken into account throughout the whole design phase. The engine has to respect stringent requirements: an initial thrust of 1 kN, an initial chamber pressure of 50 bar down to a minimum of 20 bar. Moreover, the 80% of a cylinder 2 m long and 1 m wide is considered for the allocation of tanks, combustion chamber and convergent section of the nozzle. The 20% of empty space is left vacant for all those components necessary for the effective operation of this propulsion system. Once the geometry is fixed, an iterative method is implemented to study the evolution of thermodynamics, fluid dynamics and performances of the system. The rationale behind this decision derives from the necessity to correctly handle the uneven pressure and mass flow rate change of fuel and oxidizer due to the blow-down evolution. A critical analysis of the results and the trends of all the parameters will be presented in the report. Finally, a further analysis of the uncertainties due to additive manufacturing is performed and a study on the possibility of realizing engine cooling with RP1 is carried out.