The magnitude of the exhaust velocity is dependent on molecular and chemical properties of the propellant, and the expansion ratio of the engine. The main requirement for all propellant combinations is to maximize the energy release per kilogram; in other words, the lower the mass for a given energy release, the higher is the ultimate velocity of the vehicle. This also implies that the mass flow rate depends on the density, while the exhaust velocity depends on the energy contained in the hot gas. The main performance parameters can be defined as the thrust coefficient related to the nozzle performance, and the characteristic velocity related to the propellant and combustion performance. The first parameter reaches its optimum when the exhaust pressure is equal to the ambient pressure while the second parameter is defined by the choice of propellant combination. The objective of this work is to investigate, numerically and thermodynamically, different combinations of oxidizers with conventional and alternative fuels, for different rocket propulsion and energy generation systems. Based on the state-of-the-art and the analysis results on the most promising fuel-oxidizer combinations for the future of aerospace propulsion and space transportation, in a technically and environmentally sound manner, conclusions are made.
The need to realize more effective ignition systems and exploit their full potential in aerospace propulsion applications has led to significant developments in laser and power systems. This work aims to investigate experimentally and describe mathematically the effectiveness of laser systems based on varying key parameters and their related effects on the sensitivity, ignition threshold, and combustion performance of boron potassium nitrate, then to define the key variables with the most significant influence on the overall system. Understanding the physics and chemistry behind the combined system of laser power source and optics system, and the considered medium as well as the interaction in between, led to a better apprehension of how an optimal and viable solution can be achieved in terms of ignition delays, burning times, and combustion temperatures, considering laser wavelength, power and energy densities, and the focal length displacement over a changing working distance. This is of paramount importance when operating amid difficult conditions in aerospace propulsion applications or during outer space missions, particularly those involving manned missions, not only in terms of performance and efficiency but also safety, engineering, and economic feasibility.
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