Research and Development of a Combined Fuel Cell and Satellite Thruster System

Abstract

Various different challenges are being faced in the space industry, concerning the increased difficulty level of missions that are planned, down-scaling of the satellites and especially considering the toxicity of fuels used in the spacecraft. To systematically tackle these problems, requirements are set for a ‘CubeSat’ sized satellite for which a sustainable and environmental friendly power and propulsion system has to be developed. Many ‘green’ propellant options are there to deliver the power, of which mainly Hydrogen Peroxide (H2O2) is considered a suitable option, because of its high energy density and reaction products being only water and oxygen. Besides being used in the propulsion system as propellant, the H2O2 could then also be used as fuel and oxidizer to generate electric power in an additional system.
The exothermic decomposing liquid is currently under investigation to provide thrust and electricity using catalyst materials, which experiences degradation of performance over time. Therefore, different long-lasting solutions have been experimented with, based on thermal decomposition of the H2O2 and improved electro-reduction methods. This way, a green solution would be present to undertake various missions using small spacecraft that need around 1N of thrust, while simultaneously delivering up to 60W of extra power during its operation. Multiple Proof of Concept (PoC)’s were therefore developed to understand the processes and acquire the voltage, current and temperature data, generated and required by the systems. The energy required for ignition of the H2O2 using various resistance wires was recorded visually and with thermocouples. A drop test study was done for better understanding first, after which a safe injection setup was constructed where different conditions could be looked into. Various fuel cell structures were tested in a different experimental setup before this, to try and reach the extra power the thermal ignition requires. A demonstration of the various ways this system could be optimized was then done, mainly by changing input parameters. Cooperation of the systems was looked into by combining them and checking feasibility of incorporation in a CubeSat. Several electrochemical related properties prove to have large effects on the power density and potential and a maximum of 4.5mW was reached. Similarly, the ignition conditions of the propellant will have to be looked into more, since the 24.8W currently needed for small mass flow rate decomposition, is excessive already.
This makes the incorporation in a combined system design difficult, but worth investigating, because of the many possibilities it brings forth. Based on the study performed so far it is concluded that providing enough sustainable electrochemical power for an efficient thermal decomposition is challenging, but feasible. The required conditions and achieved results with H2O2 will be presented in this research as well as recommendations to future work on this upcoming field of study. Utilizing a second propellant such as ethanol would be the next step in upgrading the system performances and lower the ignition energy required, whilst increasing the electrical energy obtained from the fuel cell.