Experimental Investigation of Regolith-Ice Mixtures under Cryogenic Vacuum Conditions for Lunar and Planetary Exploration

Introduction

A good understanding of the properties of water-ice and regolith mixtures is of paramount importance to support the development of upcoming scientific missions to the Moon and for future in-situ resource utilization (ISRU). Although water was already detected on the Moon by remote sensing observations and in impact ejecta (Colaprete et al. 2010), ground truth based on in-situ measurements is still missing. Water is a valuable resource for both human and robotic space exploration as it can be used as a propellant to fuel rockets or consumable for astronauts. Here, we present the development of a dusty thermal vacuum chamber (DTVC) at the Technical University of Munich (TUM) that will be used to qualify instrumentation developed for future Moon missions and to thermal ice extraction in relevant environments ( mbar, 150K).

Experiment Description

The state-of-the-art facility can reach vacuum levels down to  mbar. To prevent sublimation of ice particles, the regolith sample is cooled by a laboratory thermostat to a minimum temperature of 150 K. The cold plate can host a variety of sample geometries up to a size of 590 mm x 240 mm x150 mm (Figure 1). As the cooling system does not rely on consumables like liquid Nitrogen, the sample cooling can theoretically be sustained for several days.

Figure 1: The cold plate of the experiment with different regolith containers.

The samples can be illuminated by a calibrated halogen lamp with a light power of up to 50 W in the visible range. The position of the collimated light beam (Ø 50mm) is controlled by a movable mirror (see Figure 2). This allows for a maximum illuminated sample region with a diameter of 275 mm. The resulting temperature distribution in the sample is measured by sensors inside the sample as well as an infrared camera.

Figure 2: Overview of the vacuum chamber with illumination (marked in red) and ice retrieval (marked in pink) sections. A zoomed view on the mirror assembly indicates the position control of the mirror.

Planned Experimental Campaigns

In the near future, several novel experiments are planned to use this DTVC setup:

Investigation of Solar Heating for Thermal Ice Extraction:

As part of the EIC pathfinder project Ice2Thrust, this experiment will study the heat distribution in response to solar surface heating and the interaction of water vapor with a cold trap in close vicinity to the surface. The illumination can provide light power up to 20 solar constants, which allows an investigation of various surface power densities on the temperature distribution and water sublimation rates. A separate assembly is mounted on the side of the main chamber to retrieve the ice collected on the cold plate with a linear feed-through. It can be isolated with gate valves, allowing the pressurization and subsequent liquefaction of the collected water ice. The extracted liquid water will be fed to an electrolyser and subsequently be split into Hydrogen and Oxygen to generate thrust in a chemical thruster. This experiment will serve as the world’s first ISRU end-to-end demonstration from extraction up to utilization.

Qualification of Sensors for Water Ice Detection on the Moon:

TUM is developing several permittivity sensor for the detection of water on the lunar surface. These sensors measure the water content by detecting changes in the electric permittivity of the lunar surface via electrodes in direct contact with the soil (Gscheidle et al. 2024). The RPS sensor suite currently developed for ESA uses electrodes mounted on a rover wheel and will undergo development and qualification testing in the DTVC. As part of another development for ESA, an instrumented drill for volatiles and water ice prospecting will also be tested in the DTVC (Biswas et al. 2020).

As the interaction of ice, rocks, and sunlight is also relevant in cometary research (Kreuzig et al. 2021, Knoop et al. 2024), the DTVC facility can also be used to study related physical phenomena relevant to other icy moons and comets.

Investigation and Development of Dust-resistant Mechanisms:

Lunar and planetary regolith are composed of abrasive particles in several size ranges which can significantly impact the lifetime of space mechanisms. Qualification and test of mechanisms in a relevant environment is crucial to ensure proper lifetime on the lunar surface. The DTVC offers this test capability and will also be used to qualify a newly developed slip ring within the RPS project funded by ESA (Sesko et al., 2025).

Conclusion

The DTVC facility is crucial for advancing lunar exploration and ISRU in ongoing research projects. By enabling experiments on water-ice and regolith mixtures, it supports the development of key technologies for detecting lunar water, thermal ice extraction, and durable instrument components. These efforts are essential for the success of future lunar and planetary science missions and developments leading to the utilization of lunar resources.

References

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Kreuzig, C., et al. (2021). The CoPhyLab comet-simulation chamber. In Review of Scientific Instruments (Vol. 92, Issue 11). AIP Publishing. https://doi.org/10.1063/5.0057030

Knoop, C., et al. (2024). Experimental results from the CoPhyLab -Detection of the influences of surface structureson particle ejection in comet-simulationexperiments. Copernicus GmbH. https://doi.org/10.5194/epsc2024-499

Sesko, R., et al. (2025) A dust-tolerant slip ring for Lunar rover wheel-mounted permittivity sensors, accepted talk at European Space Mechanisms and Tribology Symposium, Lausanne, Switzerland

Biswas, J., et al. (2020). Searching for potential ice-rich mining sites on the Moon with the Lunar Volatiles Scout. In Planetary and Space Science (Vol. 181, p. 104826). Elsevier BV. https://doi.org/10.1016/j.pss.2019.104826

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Acknowledgements

The authors gratefully acknowledge the financial support of the European Union (GA number 101161690) for the project Ice2Thrust (S4I2T)