New Space and Tech

ICE-Cube Mini-Thruster Could Propel Deep Space Missions With Water

By Elizabeth Howell
September 26, 2023
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ICE-Cube Mini-Thruster Could Propel Deep Space Missions With Water
The ICE-Cube mini-thruster.
Image credit: ESA.

An early-stage space project suggests that future thrusters may be able to use water as propellant.

Finding a way to do so would be particularly advantageous for space exploration, since water abundant throughout the solar system and especially on the Moon – making it easier, in theory, to refuel during space missions traveling far beyond Earth. At the same time, NASA and other partners are planning Artemis astronaut landing missions to the water-rich south pole of the Moon as soon as 2025, depending on hardware and mission development.

The thruster project is called the Iridium Catalysed Electrolysis CubeSat Thruster (ICE-Cube Thruster), and is based at the United Kingdom’s Imperial College. It’s a tiny thruster, just fingernail-sized, and uses only 20 watts of power to produce electrolysis (through hydrogen and oxygen.)

Recently, the European Space Agency announced the success of a test campaign in a laboratory: 1.25 millinewtons of thrust, at a specific impulse of 185 seconds, produced by ICE-Cube “on a sustained basis.” The data may be useful to create a more flight-representative engineering model, in conjunction with URA Thrusters and Imperial.

“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,” the ICE-Cube team wrote in a project description.

“To put it into perspective the space shuttle main engine, RS-25, has approximately half a billion times more thrust than ICE-Cube,” the description continued. RS-25 is also used on the Space Launch System rocket that will launch Artemis missions to the Moon.

ICE-Cube for SmallSats

ICE-Cube aims to not only use an abundant resource, but also to match the needs of the fast-growing small satellite constellation market. Design constraints on the small satellites, especially nanosatellites, tend to make it difficult to include propellant, as they must stay very small and use low power.

Using water electrolysis is not only more environmentally-friendly and makes use of a substance (water and its components) that is easy to store, but the process also requires less power than typical electrical propulsion devices.

The challenge, though, lies in fabrication. The team says the best process is a MEMS (Micro-Electrical Mechanical Systems) approach, which is already used for processors and other micro-electronics.

MEMS “allows silicon wafers to be machined with sub-micrometer precision,” according to the description. “The approach is also inherently scalable, and allows thrusters to be produced in large batches at an exceptionally low unit cost.

The process uses ion etching on refractory metal and silicon wafers. “These etched features are then sputter-deposited with iridium, which serves as an ignition catalyst as well as providing oxidation protection to the walls,” Imperial researchers wrote. “Thruster wafers are then joined through diffusion bonding, producing a single component thruster ‘chip’.”

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