Under ESA’s General Support Technology Program (GSTP), researchers at Imperial College London are developing a micro-scale rocket engine called the Iridium Catalysed Electrolysis CubeSat Thruster (ICE-Cube Thruster).
Designed to maneuver the smallest classes of satellites, this tiny space thruster utilizes the propellants of hydrogen and oxygen produced by the electrolysis of water. Avoiding any need for bulky gaseous propellant storage, an associated electrolyzer runs a 20-watt current through water to produce hydrogen and oxygen to propel the thruster.
The entire thruster chip is about the length of a fingernail, with its combustion chamber and nozzle measuring less than 1mm in length. The thruster is so small in scale that it could only be assembled using a MEMS (Micro-Electrical Mechanical Systems) approach, borrowing methods from the microelectronics sector.
In a test campaign, the ICE-Cube Thruster achieved 1.25 millinewtons of thrust at a specific impulse of 185 seconds on a sustained basis – that’s half a billion times less thrust than the engines used on the Space Shuttle. Testing took place through an ESA General Support Technology Programme De-Risk activity to prove the thruster’s feasibility in laboratory testing.
The ICE-Cube Thruster is designed 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, weighing less than 22 lbs (10 kg), accounted for approximately 90% of spacecraft launched in 2017.
These tiny satellites 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 unpressurized, non-toxic propellants.
The ICE-Cube thruster meets these requirements by using an electrolyzer to split water into its constituent molecules of hydrogen and oxygen in space and feed these directly to the thruster. This system has several benefits, including the ease of storing a non-hazardous propellant in compact, lightweight tanks and the high performance of hydrogen/oxygen. Additionally, water electrolysis requires only a fraction of the power of comparable electric propulsion devices, which is well within the power range available for nano-satellites.