Nano rocket thruster can run on water, fit on a fingertip

The new ICE-Cube thruster developed by Imperial College runs on water, offering a green and efficient propulsion system for small satellites.
Rizwan Choudhury
ICE-Cube Thruster: Mini space thruster that runs on water.
ICE-Cube Thruster: Mini space thruster that runs on water.

Source: Imperial College/ESA 

A team of researchers from Imperial College London has developed a tiny rocket engine that runs on water, which could be used to maneuver small satellites in space.

The engine called the Iridium Catalysed Electrolysis CubeSat Thruster (ICE-Cube Thruster) is based on electrolysis, a process that splits water into hydrogen and oxygen using an electric current.

Role of electrolysis

At the heart of the ICE-Cube Thruster is an electrolyzer that operates on a mere 20-watt current. When water is subjected to this electrolysis process, it is split into hydrogen and oxygen gases, which serve as the propellant. The hydrogen and oxygen are then fed into a combustion chamber and nozzle less than 1mm in length to produce thrust. This negates the need for bulky storage tanks that hold gaseous propellants, usually a significant obstacle in miniaturizing propulsion systems.

Tailored for the burgeoning small satellite market

The ICE-Cube Thruster is designed to meet the needs of the rapidly growing small satellite market, which consists mainly of nanosats weighing under 10 kg. These miniature satellites have very strict constraints on size, weight, power, and propellant, which make integrating a conventional propulsion system difficult.

Data reveals that the annual number of spacecraft deployed is predicted to triple from its numbers in 2016. More notably, nanosatellites, weighing less than 22 lbs (10 kg), accounted for approximately 90% of spacecraft launched in 2017. These bite-sized satellites have stringent requirements—compact size, low power consumption, and eco-friendly propellants—that the ICE-Cube Thruster efficiently satisfies.

The ICE-Cube Thruster offers several advantages over other propulsion systems for small satellites. First, it uses water as a propellant, which is non-toxic, easy to store, and widely available. Second, it has a high level of performance, as hydrogen and oxygen are the most efficient chemical propellants. Third, it requires only a fraction of the power of comparable electric propulsion devices, which is well within the range of nano-satellites. Fourth, it can be fabricated using micro-electronics techniques, which allow for high precision, scalability, and low cost.

What sets the ICE-Cube Thruster apart is its manufacturing process. A micro-electrical mechanical systems (MEMS) approach was employed, a technique common in the microelectronics sector. This innovative method enables the thruster components to be assembled with sub-micrometer precision, allowing for scalability and batch production at astonishingly low costs.

Nano rocket thruster can run on water, fit on a fingertip
The ICE-200 thruster which uses the same manufacturing techniques.

Toward a flight-ready mode

The ICE-Cube Thruster was developed under ESA’s General Support Technology Program (GSTP), which aims to de-risk new technologies for space applications. The thruster underwent a test campaign at Imperial College London, where it achieved 1.25 millinewtons of thrust at a specific impulse of 185 seconds on a sustained basis.

To put the scale into context, this thrust is half a billion times less than what was utilized in the engines of the iconic Space Shuttle. Yet, its size and efficiency make it a potentially transformative invention for the CubeSat industry.

The experimental data gathered during this activity will help guide the development of a flight-representative model of the propulsion system, including the electrolyzer. This development will be led by URA Thrusters in collaboration with Imperial College London.

The ICE-Cube Thruster is a micro-scale version of the ICE-200 Thruster, a higher thrust (1N) variant also developed at Imperial College London. The ICE-200 Thruster uses the same principle of water electrolysis and iridium catalysis but has a larger combustion chamber and nozzle.

The ICE-200 Thruster has been selected by ESA for its Lunar Pathfinder mission, which will demonstrate lunar communications services in 2024. The thruster will provide attitude control and orbit maintenance for the Lunar Pathfinder spacecraft.

The ICE-Cube and ICE-200 thrusters are examples of how water can be used as a green and efficient propellant for space missions. The researchers hope that their technology will enable new applications and capabilities for small satellites in the future.

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