A micro-scale rocket engine is being developed at Imperial College London in the U.K. for the European Space Agency. The iridium catalyzed electrolysis CubeSat thruster (ICE-Cube Thruster) is so small — about the length of a fingernail — that it can only be fabricated using micro-electrical mechanical systems originally designed for manufacturing silicon chips.

The tiny thruster is being engineered to meet the needs of a growing fleet of small-scale satellites. Propulsion systems for these nanosats, weighing less than 10 kg, must be very small, operate on very low power and preferably consume unpressurized, non-toxic propellants. The ICE-Cube thruster meets these requirements by using an electrolyzer to split water into its constituent hydrogen and oxygen molecules in space and feed these directly to the thruster. The diminutive dynamo produces a thrust of only 4.5 millinewtons in a design that simplifies storage of a non-hazardous propellant in compact, lightweight tanks.

An added benefit is the low power requirement of the electrolysis process in a device that needs only 20 W of electric current to operate. During testing, the space thruster generated 1.25 millinewtons of thrust at a specific impulse of 185 seconds on a sustained basis.