This thesis report is written as part of the Master Aerospace Engineering - Space Flight of the Delft University of Technology. The thesis was started in November 2020 and completed by June 30, 2021. The space industry is dominated by traditional highly toxic propellants, namely hydrazine. Due to its carcinogenic nature, REACH makes provisions for a ban on hydrazine, increasing the pressure on finding a feasible alternative propellant. Additionally, due to more awareness about environmental sustainability, there is an urgent need for "green propellants" for space applications. The objective of this thesis is to investigate and develop a novel green hybrid hypergolic bi-propellant system with a viscoelastic nature of the fuel. The thesis focussed on determining the formulation of the novel bi-propellant, which was found to be highly concentrated hydrogen peroxide as the oxidizer and gelled alcohol in which a catalyst is suspended as fuel. The fuel's viscoelastic nature is achieved by using gelling technology and characterized based on a rheology study. A suitable catalyst is found and the performance of this catalytically induced hypergolic propellant is evaluated by means of a multi-drop test. In the end, promising performance results were obtained with fuel having critical gelling concentration and critical catalysts concentrations well below what is described in the literature. ... Read more