The electric-pump cycle is a rocket engine configuration that uses an electric motor to power the pumps instead of a turbine. This offers several expected advantages such as simpler design, lower development costs, and easier restartability, but comes with reduced performance compared to conventional cycles. Previous research has primarily compared the electric-pump cycle to the gas generator cycle and has been limited to direct comparison. To extend the previous research a Rocket Cycle Analysis Tool was developed called RoCAT. It models the last-named cycles as well as the open expander cycle for a broad scope of thrusts, burn times, and chamber pressures, and several propellants. In addition, RoCAT optimizes several inputs for each cycles individually for a fairer comparison. Besides analyzing the electric-pump cycle's current performance, this research also estimates its performance in the future based on historic trends in its key technologies like the battery and electric motor.

The current state of in-orbit refuelling involves launching propellant from the Earth’s surface in a single use refuelling craft, often to transfer hydrazine to the customer. This method is a logical first step however this architecture is not reusable, and it centres around a toxic and carcinogenic propellant. An architecture is proposed where hydrogen peroxide, a green oxidiser useful in both propulsion and power systems, is created from water ice in the solar system and refuelled with a reusable refuelling craft. First order sizing of the craft is conducted showing the viability of refuelling routes from Deimos, Phobos and the Moon. Prototype testing of a propellant transfer mechanism has shown the promise of using a piston-based transfer system, and the results of testing are used to better estimate the mass of a potential reusable refuelling craft.

Some propellants currently used in space propulsion have the disadvantage of being dangerous to humans and the environment. A wellknown example of this are hydrazine and its derivatives which are toxic, corrosive, and carcinogenic. These disadvantages have led to a search for less hazardous storable liquid propellants, often referred to as green propellants. A green propellant is safer to use and handle and will therefore bring down the costs related to production, storage and handling. The main reason for the use of hydrazine is its hypergolicity with common oxidizers like NTO and nitric acid. Hypergolicity is the property that a fuel and oxidizer ignite spontaneously when brought in contact without the need for an external source. This property is beneficial since it eliminates the need for an ignition system, thereby making the propulsion system more simple, reliable, and cheaper. It is therefore desired that a replacement propellant also shows this property with common oxidizers.
During this thesis two methods are explored with the goal of creating a green hypergolic propellant combination. One based on catalytically enhanced ethanol and high concentration hydrogen peroxide. The other based on a pyrophoric liquid that is added to ethanol. There have already been efforts made before by adding catalyst particles or a strong reducer to a hydrocarbon fuel like kerosene or ethanol. The problem with using catalyst or strong reducer particles is the difficulty of creating a homogeneous mixture. Due to the liquid nature of the parent fuel, the particles will start to separate from the fuel and sink to the bottom of the container. To overcome this problem an organic gelling agent is added to the fuel to increase its viscosity, thereby increasing the sedimentation time. This will not only increase the shelf life of the fuel but also decrease the vapor pressure, making it less flammable and safer to work with, and reduce storage problems like propellant sloshing and spilling. Increasing the viscosity also makes it more difficult to transfer the fuel through the feed system and achieve proper atomization. However, by applying shear force on the fuel it shows shear thinning behavior, decreasing the viscosity close to that of the parent properties making it easy to use in existing propulsion systems designed for liquids. A second effect of the organic gelling agent is that due to its energetic nature it participates in the combustion. Therefore, the amount of catalyst needed can be reduced to a negligible amount while still achieving good performance properties like ignition delay time. This is verified by means of a drop test.
As a second approach, instead of adding solid catalyst particles a pyrophoric liquid is added to ethanol. A liquid allows for easier mixing and creating of a homogeneous mixture resulting in a longer shelf life compared to using catalyst particles. The pyrophoric liquid also fully participates in combustion resulting in increased performance compared to catalyst particles that do not combust. Due to the reactive nature of the pyrophoric liquid this propellant formulation is expected to be able to achieve hypergolicity with multiple common oxidizers. This results in a versatile system which can be used in current propulsion systems without extensive modification required. By eliminating the need for an ignition system, the propulsion system is simplified and its reliability is increased.

An important topic in the field of rocket propulsion is the development of a new green advanced hypergolic rocket propulsion system. The current hypergolic propellants have one large drawback, namely the toxic properties. The injector has a crucial role in the performance of a liquid engine. Therefore, the next step in the development of this novel propulsion system is the development of the injector. The purpose of this master thesis is to design, manufacture, and test this novel injector. The injector is designed to operate in monopropellant and bi-propellant modes, which is supported by the new green hypergolic propellants. In total, four different configurations of the injector are developed. Different testing objectives are defined for the experiments to test all the injector configurations. These testing objectives are atomization behavior, atomization performance, the mixing process in bi-propellant mode operation, and atomized flow in combination with the heating element.

The German Aerospace Centre (DLR) has in the past years been performing test runs with their experimental sub-scale combustion chambers to measure and investigate the effects of unstable combustion. Some of these investigations are focused on the heat flux to the chamber walls, changes in which can cause a significant shift in chamber wall strength and even melting, and can thus lead to structural failures. As a continuation of research regarding this phenomenon, the DLR combustion chamber version D (BKD) is used to investigate changes in heat flux, and its test data have been made available for this research. Using the test data, finding a relation between measured steady state heat flux and controlled chamber conditions became feasible, and changes in heat flux related to combustion instabilities can be identified. However, although these changes in heat flux are often observed and are described in literature as a known effect of combustion instabilities, there are currently no validated explanations as to why these effects take place. In an effort to provide this explanation, the results of a previously completed investigation regarding the DLR combustion chamber version H (BKH) are evaluated, as they allowed determination of a relation between combustion length and magnitudes of acoustic pressure oscillations. In this research, the results obtained for combustion length are converted to a model regarding varying heat flux profiles and modified as to implement them for BKD. Finally, the model predicted increases in heat flux during time periods when increases are observed experimentally, showing agreement with the experimental data. Besides this, a conversion in the model allowed reconstruction of a localised heat flux profile, which showed an increase in local heat flux near the injector face plate. This matches effects described in literature and observed in the experimental set-up after a test run with combustion instabilities. With this validation of the model, the theory developed and tested in this thesis work could prove a significant advancement in the understanding of effects of combustion chamber instabilities and their impact on the engine integrity and performance.

Geolocation of Radio Frequency (RF) emitters, is finding the geographical location of said emitter. This thesis explores the concepts of geolocation, specifically, Space-Based geolocation of earth-surface emitters by means of measuring the Angle-of-Arrival using a Uniform-Rectangular Antenna Array. Initially the literature is explored, the significance of Geolocation is made clear and the research outline and scope is defined. Afterwards, Angles-of-Arrival finding algorithms are investigated and implemented, specifically the subspace algorithms: "MUltiple SIgnal Classification" (MUSIC) and "Estimation of Signal Parameters via Rotational Invariance"(ESPRIT). These algorithms are thoroughly explained, a model is obtained and implemented into a Simulation framework. The Simulation Framework is used to create a Graphical Tool used to calculate performance figures of Space-Based Geolocation. By using the obtained Simulation, a sensitivity analysis is produced. This sensitivity analysis observes the effect of design parameters of a satellite platform and geolocation payload on the geolocation performance. This sensitivity analysis is used to find the optimal approach when designing a geolocation payload. This approach can be used to synthesize a geolocation payload design that maximizes performance.