How does process water treatment contribute to space exploration? Measurement of conductivity, pH and turbidity of lunar water – a case study

Could ice trapped in rocks on the Moon revolutionise future space missions?

Imagine you are an astronaut on a mission to the Moon. Around you stretches an endless lunar landscape, dotted with craters and rocks. Although Earth is visible, it seems distant, almost surreal. In this harsh and inhospitable setting, water becomes a priceless commodity. This is all the more true as technology advances and plans to conquer space become bolder – with longer manned missions, the construction of bases on the Moon, and perhaps even flights to other planets – the demand for water is growing.

Access to clean water in space is not just a matter of survival for astronauts. It is the key to the development of sustainable space exploration, which minimises the impact of missions on Earth and opens up new opportunities for us. Transporting water from Earth for space missions is extremely expensive and risky. Every kilogram of cargo delivered into orbit involves expenditure and the risk of failure during launch or transport. Furthermore, space exploration cannot come at the expense of Earth – we must strive for a sustainable approach that minimises our impact on the planet. What is more, reducing the amount of water transported would free up valuable space in rockets, allowing additional research equipment to be taken on board, which would increase the scientific and exploration capabilities of each mission. Therefore, searches for alternative sources of water in space have been conducted, during which it was discovered that there is ice beneath the surface of lunar rock, known as regolith. Obtaining water from these sources would reduce the cost of space missions, limit the consumption of Earth's resources and reduce the amount of cargo transported from our planet.

The LUWEX project: a revolution in water extraction on the Moon

To put this concept into practice, the European Commission funded the pioneering LUWEX (Validation of Lunar Water Extraction and Purification Technologies for In-Situ Propellant and Consumables Production) project. Its main objective was to develop technologies for extracting, purifying and storing water from lunar regolith. Research teams from Germany (German Aerospace Centre – project coordinator, Technical University of Brunswick), Poland (Wrocław University of Technology, Scanway Sp. z o.o.), Italy (Thales Alenia Space Italia) and Austria (LIQUIFER Systems Group) participated in the project. Thanks to international cooperation, the LUWEX project has significantly accelerated the development of technologies necessary for sustainable exploration of the Moon and paved the way for future space missions based on the use of local resources.

Technical and logistical challenges in obtaining water on the Moon

Obtaining and treating water on the Moon presented numerous challenges. Firstly, water is found there exclusively in the form of ice, which required the development of specialised extraction methods. Secondly, regolith contains contaminants that had to be removed to make the water safe for consumption. The purification process had to be energy-efficient and reliable to withstand the harsh lunar conditions. An additional challenge was logistics – transporting equipment to the Moon and ensuring its operation in extreme temperatures and vacuum conditions. This required close cooperation between international scientific and industrial teams.

What was the significance of conductivity, pH and turbidity in the purification of moon water?

Although some of the tasks planned for the project were carried out in a laboratory on Earth at the Wrocław University of Science and Technology, the requirements for the quality of the water obtained were just as strict as those that will apply during actual space missions. Monitoring water quality was therefore a key element of the process that determined whether the technology would work on the Moon.

Three particularly important parameters were monitored during the tests: conductivity, pH and turbidity. These parameters were chosen because they provided quick, reliable and comprehensive information about both the chemical and physical condition of the water, while also enabling immediate identification of any technical problems in the water extraction and purification system. The conductivity of the water indicated its degree of mineralisation, i.e. the amount of dissolved salts and ions. Very low conductivity was required, especially when the water was to be subjected to electrolysis, as it ensured efficient decomposition into hydrogen and oxygen and protected the electrodes from contamination.

Ph, or the level of acidity or alkalinity of water, should have been as close to neutral (approx. 7) as possible. This pH value guaranteed that the water was safe to drink and that the treatment process had been carried out correctly, without the introduction of undesirable chemicals.

Turbidity, in turn, indicated the content of solid particles and suspended solids. Low turbidity indicated that the mechanical filters were working properly and that the water was clear and free of physical contaminants, which directly affected its safety and comfort of consumption. Thanks to continuous monitoring of this parameter, it was possible to quickly detect any mechanical failures, such as the ingress of regolith particles or damage to seals.

Continuous monitoring of these parameters allowed scientists to assess the effectiveness of individual stages of the purification process on an ongoing basis and to respond quickly to any technical problems. This made it possible to obtain water of the highest quality – ready for use in future space missions.

What requirements were set for measuring devices in the LUWEX project?

In the LUWEX project, the selection of appropriate measuring devices was crucial to the success of the entire undertaking. The research team from the Wrocław University of Technology thoroughly analysed the solutions available on the market, guided by several important criteria. First and foremost, the sensors had to ensure high accuracy and stability of measurements. The durability and reliability of the devices were also important, as they had to operate without interruption for long periods of time in a demanding environment. The team also paid attention to the manufacturer's experience in industrial applications, which increased the likelihood that the devices would perform well in conditions similar to those encountered during actual space missions. Another important factor was the ability to integrate seamlessly with the central control and data acquisition system so that measurements were available in real time and could be analysed immediately. By meeting these requirements, the measuring devices effectively supported the entire technological process.