Most satellites built to date manoeuvre in space using two very different types of thrusters and propellants. High thrust functions are met by extremely toxic chemical fuels (Hydrazine) that are costly and challenging to handle as they are lethal to humans from brief exposure. Where high fuel efficiency is required and low thrust can be accepted, electric propulsion (EP) thrusters are used, fed by expensive high purity noble gas (Xenon), stored at very high pressure. These two entirely separate systems are both present on many larger spacecraft platforms to cover the full required ranges of thrust and fuel efficiency. Alternative low-cost and non-toxic propellants have been increasingly adopted for small satellites, where their price and handling advantages have a particularly high impact. Our project's ultimate goal is to replace both Xenon and Hydrazine with water, the ultimate green, low-cost propellant, for both chemical and electric propulsion functions in large satellites. The proposed HYDRA system concept electrolyses water on-demand during a mission into oxygen and hydrogen. The project is focussed on the EP sub-system: development of a Water ElecTrolysis Hall Effect Thruster (WET-HET), which ionises and accelerates positively charged oxygen to the very high speeds required for fuel efficiency. This is combined with an electron-emitting hollow cathode device, fed with hydrogen, required to keep the spacecraft charge-neutral. Both of these device types have not been used with those propellants in spaceflight to date. For the higher thrust impulses required by the satellite, these two gasses will in addition be used in a chemical bipropellant thruster, ICE. This allows a spacecraft to fly with both fuel efficient electrical and high thrust chemical propulsion options, but a single low pressure water propellant tank, propellant management system, and associated hardware. This completely novel overall architecture allows a full spectrum of mission scenarios that are not possible with either technology alone, without the cost and mass penalties of flying two completely separate systems and propellants, at the very low propellant price and high storage density of water. The project focusses on the technical and engineering challenge of adapting existing technology concepts of Hall Effect thrusters and neutralizers to run on the unconventional oxygen and hydrogen fuels, in prototypes with sufficiently high performance and lifetime. Work will focus on all aspects of these two device designs from material selection to manufacturability, and culminate in extensive test campaigns in vacuum chambers to simulate the conditions of space.