Research postgraduate Charlie Muir is working on this project, sponsored by the European Space Agency.

The Iridium Catalysed Electrolysis CubeSat Thruster (ICE-Cube Thruster) is a micro-scale rocket engine which is being developed at Imperial College London under ESA's General Support Technology Program (GSTP).

The thruster utilises the propellants of hydrogen and oxygen produced by the electrolysis of water and is designed to produce a thrust of only 4.5mN. Designing a thruster to function at this scale is a unique challenge and requires a very different approach compared to the typical rocket engines most people are accustomed to - to put it into perspective the space shuttle main engine (RS-25) has approximately half a billion times more thrust than ICE-Cube. 

 

The reason for such a small-scale thruster is to meet the needs of the rapidly growing small satellite market. The annual number of spacecraft deployed in 2020 is predicted to be over three times the number in 2016, of this growing market nanosats (<10 kg) constitute the vast majority of spacecraft launched (~90% in 2017). These tiny satellites (usually the size of a briefcase) have very strict constraints which make integrating a propulsion system difficult. A propulsion system is required to be very small, operate on very low power and in most cases use unpressurised, non-toxic propellants. 

The ICE-Cube thruster meets these requirements by using an electrolyser to split water into its constituent molecules of hydrogen and oxygen in space and feed these directly to the thruster. The immediately obvious benefits of the system are primarily the ease of storage of a non-hazardous propellant in compact, lightweight tanks as well as the very favourable performance of hydrogen/oxygen. Water electrolysis also requires only a fraction of the power of comparable electric propulsion devices which is well within the power range available for nano-satellites.

Fabricating such a tiny thruster is not feasible using conventional manufacturing techniques (the combustion chamber and nozzle are less than 1mm in length) and can only be achieved using a MEMS (Micro-Electrical Mechanical Systems) approach. This is the same fabrication approach used to manufacture micro-electronics such as processors, and it allows silicon wafers to be machined with sub-micrometer precision. The approach is also inherently scalable and allows thrusters to be produced in large batches at an exceptionally low unit cost. These fabrication techniques have been set out through the development of the ICE-200 thruster which is a higher thrust (1N) variant developed at ICL.