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Breakthrough will pave the way for the implementation of water – primary source of oxygen and hydrogen – as a more cost-effective fuel, and open up new pathways to provide in-space transportation, mobility and logistics through resources that can be extracted in celestial bodies

LONDON, SINGAPORE – 21 MARCH 2023 – A consortium made up of commercial enterprises and academics from the UK and Singapore has made history by achieving ignition and stable sustained operation of a Hall effect thruster (HET) running fully on the by-products of water electrolysis as a propellant. The consortium led by URA Thrusters Ltd (URA), in collaboration with the Imperial College London (ICL) and Aliena Pte Ltd (Aliena), successfully executed the test campaign at the Imperial Plasma Propulsion Laboratory (IPPL) in the final few weeks of 2022.

A satellite engine, also known as a spacecraft propulsion system, acts to generate thrust and offers mobility to satellites enhancing their operations in space. Specifically, HETs have a rich heritage of being utilized in the most prolific of missions and has been widely acknowledged as one of the most commonly employed mode of electric propulsion systems for satellites, due to their designs that make them reliable and robust for the most demanding of space missions. HETs in space today typically use expensive noble gases (such as xenon or krypton) as fuel, that are ionized while the ions are then accelerated to extremely high velocities out of the spacecraft – generating thrust. This new thruster however, AQUAHET, operates solely on the by-products of water (ura in the basque language) electrolysis.

The idea of a HET operating on water electrolysis, with oxygen flow to the anode and hydrogen to the cathode, was first proposed within the Imperial Plasma Propulsion Laboratory and published at the Reinventing Space Conference in 2018. The thruster is now being developed into a commercial product, with the commercialization effort being led by URA Thrusters Ltd. AQUAHET, the thruster built by URA, is optimized to operate on oxygen, and is coupled with a hollow cathode (the electron emitter that maintains the thruster’s operation), built by Aliena, that runs on hydrogen. Such gases can be obtained by splitting water molecules using electricity, in an electrolyser, which is also being developed by URA in collaboration with the European Space Agency (ESA). The experiments performed at the IPPL showed, for the first time, the stable operation of such a HET using oxygen and hydrogen in a stoichiometric ratio at power levels of approximately 1.2 kilo-Watts.

The propulsion subsystem has further demonstrated capability to produce forces in the excess of 50 milli-Newtons and specific impulse beyond 3000 seconds at power levels up to 3.2 kilo-Watts, providing a high fuel efficiency. This demonstrates great potential to replace existing xenon or krypton HETs with a new subsystem that operates on a sustainable and non-dependent propellant, water. AQUAHET will be the perfect companion for the next generation of medium and larger (>200 kg) satellites such as Geostationary (GEO) telecommunication platforms or exploration missions.

The usage of the by-products of water electrolysis (hydrogen and oxygen) as a propellant is deemed revolutionary on multiple fronts. Firstly, water can be stored in an unpressurised vessel prior to launch, allowing for launch complex and launch vehicle regulatory protocols to be bypassed. Doing so will also allow for alternative geometries for propellant tanks to be implemented, to maximize the space utilized in various spacecrafts. Next, water is a much more cost-effective propellant which is found as an abundant resource on Earth as well as other celestial bodies, paving the way for security over such fuels for various players choosing to deploy such a system. Finally, the dual by-products of water electrolysis can unlock opportunities to drive other modes of propulsion on the deployed spacecraft, giving rise to wide attainable operational windows for thrust and specific impulse through multi-modal propulsion.


The testing performed, and outstanding results collected by the consortium using the disruptive URA Thrusters AQUAHET and Aliena cathode technologies has shown that the potential for a fully sustainable electric propulsion future is now within our grasp,” said Dr James Sadler, CTO of URA. “These results will open up the next stage of the development of the AQUAHET engine towards a commercial product that has the potential to revolutionise the space industry in the next 10 years.”

This experimental demonstration of water as a high efficiency propellant for spacecraft propulsion opens up exciting possibilities for space exploration.  Water is found abundantly throughout our solar system, including the Moon and Mars.  Gathering propellant in space, rather than spending the energy to carry it with us from Earth, opens the possibility for much more ambitious space missions than anything that’s been achieved,” said Dr Aaron Knoll, Reader in Spacecraft Engineering and Head of the IPPL at Imperial College London.

The successful test campaign in the UK that demonstrated the suitability of water as a propellant with a Hall thruster is a watershed moment for the community.” said Dr Lim Jian Wei Mark, CEO of Aliena. “We count it as a great privilege to be able to work with a professional consortium of experts from ICL and URA as we break new ground as part of the EUREKA GlobalStars program supported by Enterprise Singapore and Innovate UK.” Commenting on the results of the test campaign, CTO of Aliena, Dr George-Cristian Potrivitu added: “With the successful testing campaign of AQUAHET, Aliena demonstrated her strong technological entitlement in the field of hollow cathode technology for Hall effect thrusters. Hydrocat, as the cathode is called, maintained operation with hydrogen as fuel and emitted currents up to 8 amperes. We are very proud to have been contributed to this great achievement for the world of satellite propulsion and we are looking forward to bringing this new technology to space.”

With the successful execution and completion of the joint coupling test campaign at the IPPL, the consortium aims to further the development of such a system as it closes in on flight readiness. With the huge upside of using water as a propellant, coupled with the legacy merits (from Hall thrusters) of achieving high thrust-to-power-ratio and large specific impulse for extended operations in space, the system can become a promising and attractive choice of propulsion for emerging space missions. The consortium looks forward to early engagement with prospective customers and the continued developmental work ahead to bring such a system to market.

About URA

URA Thrusters Ltd was founded in 2019 as a spin-off of the AVS group with the aim of becoming an industry leader in water-based propulsion systems for a broad range of spacecraft types. URA combines heritage in high-precision engineering for science instrumentation taken from the AVS group with in depth space propulsion knowledge from its world-class research collaborators (Imperial College London, Surrey Space Center). Maximizing this unique perspective, URA is working to produce state-of-the-art thrusters and propulsion systems in a cost-effective manner, aiming to provide solutions from the best of both worlds: old-space and new-space. To date, URA’s propulsion catalogue includes both electric and hybrid chemical-electric propulsion systems for platforms that range from nano to GEO class sizes.

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About the Imperial Plasma Propulsion Laboratory

The Imperial Plasma Propulsion Laboratory (IPPL) was established in 2017 by Dr Aaron Knoll with a view to tackle the most pressing challenges faced by engineers and scientists today in the field of spacecraft propulsion. The IPPL, which sits within Imperial College London’s Department of Aeronautics, provides expert competency in propulsion science to the wider space community through strong collaborations and partnerships with academia and industry. As a result of these collaborations, the IPPL has obtained a wide range of experience in the design, modelling and experimental investigation of Electric Propulsion (EP) devices for spacecraft applications. More specifically, research within the IPPL covers a range of topics which include alternative propellants for spacecraft EP, innovative MEMS based electrolysis micro-propulsion, and hybrid electric + chemical propulsion architectures for future space exploration.

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About Aliena

Aliena Pte Ltd is a Singapore based space propulsion provider that aims to bring space closer to home for satellite operators and terrestrial businesses. Their novel propulsion systems aim to equip disruptive next-generation satellites with advanced manoeuvring capabilities that can empower satellite operations of tomorrow. A technology spin-off from Singapore’s Nanyang Technological University (NTU), Aliena currently operates out of a privately-owned jet propulsion test facility that gives the R&D and manufacturing environment to provide their systems to the most demanding of customers internationally.

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