Why is it designed as a mortise and tenon structure- An article reveals the secrets of the -lunar soil bricks- that are about to fly into space

“Moon soil bricks” are emerging as a potential construction material for building on the lunar surface, significantly harder than regular concrete bricks. Soon, these “moon soil bricks” will be taken aboard the Tianzhou-8 cargo spacecraft to the Chinese space station for exposure experiments. What sets these bricks apart from ordinary ones, and why take them to space?

Introducing the “Moon Soil Brick”: An Extraordinary Construction Material

Can the “moon soil bricks” that could be used to build on the moon resemble the bricks we have here on Earth? To uncover the secrets of these bricks, we spoke with experts at the National Digital Construction Technology Innovation Center at Huazhong University of Science and Technology.

Professor Zhou Cheng, from the National Digital Construction Technology Innovation Center, explained, “What I have here are simulated ‘moon soil bricks.’ Their composition mimics that of actual lunar soil, and we synthesize them through a process of sintering.”

Common bricks used in everyday construction, like red bricks, blue bricks, and concrete bricks, have a density comparable to these moon soil bricks, but they boast over three times the compressive strength of standard red and concrete bricks, with the ability to withstand over 10 tons of pressure per square centimeter.

Professor Zhou continued, “The strength of these simulated ‘moon soil bricks’ is significantly higher than that of the red and blue bricks we use on Earth. The two bricks we have here feature a mortise and tenon structure, which is advantageous for assembling future lunar base constructions.”

The Journey to Space: Validating Three Key Properties of Moon Soil Bricks

Why are the moon soil bricks traveling aboard the Tianzhou-8 to the Chinese space station? What tests must they undergo to prove their capability for lunar construction? Experts say the space mission aims to validate three critical properties of the moon soil bricks.

Building on the moon entails facing extreme temperature variations, with daytime highs exceeding 180°C and nighttime lows dropping to -190°C. Additionally, without atmospheric protection, the lunar surface is bombarded by cosmic radiation and micro-meteorites, along with high-frequency moonquakes—all posing tough challenges to the mechanical, thermal, and radiation properties of lunar construction materials.

To determine whether the moon soil bricks can withstand the challenges of lunar construction, they are set to be sent aboard the Tianzhou-8. After completing the space experiments, the first moon soil brick is expected to return to Earth by the end of 2025.

Professor Zhou outlines the three key properties to be validated:
1. **Mechanical Properties**: This is vital for construction, assessing whether the bricks’ mechanical performance degrades over time.
2. **Thermal Properties**: We aim to evaluate their insulation and heat resistance capabilities.
3. **Radiation Impact**: Given the vacuum environment of the moon, we need to understand how the cosmic radiation affects the performance of the moon soil bricks.

Behind the Scenes: How Moon Soil Bricks Are Created

Given the complex conditions on the moon’s surface, the performance of moon soil bricks must meet high standards. So, how are these bricks made?

“The moon soil bricks are produced using a vacuum hot-press sintering method,” explains Professor Zhou. “The process consists of three steps. First, we weigh the simulated lunar soil, then place it into molds according to that weight. Since lunar soil is very loose, we must compact it within the mold.”

He adds, “Engineers apply uniform pressure to create an effective compact. Once the molding is completed, the mold is placed in a vacuum hot-press furnace, which is equipped with insulation. After sealing the vacuum apparatus, we increase the temperature to sinter the bricks.”

The simulated lunar material resembles terrestrial soil—dispersed in nature—and must undergo high-temperature processing. Using methods such as induction sintering, temperatures can be raised to over 1000°C in about ten minutes, allowing the moon soil bricks to be created.

“This process involves no additional materials, ensuring it’s a 100% in-situ forming method, making it a promising construction approach for future lunar bases.”

Leveraging Space Experiments to Overcome Challenges

While detailing the brick manufacturing process, researchers mentioned the “in-situ forming method.” This refers to the capability of constructing lunar facilities using resources directly from the moon, such as lunar soil, solar energy, and minerals, eliminating the need to transport prefabricated components from Earth. This approach could drastically reduce construction costs on the lunar surface. The upcoming space exposure experiments with these simulated moon soil bricks will gather vital research data for actual lunar habitation projects.

Professor Zhou mentioned, “These samples are set to accompany the Tianzhou-8 on its mission for exposure experiments in space. We have prepared three sample plates for this purpose, and we design the entire exposure duration for three years. Annually, one sample plate will be brought back to Earth for further analysis after exposure at the space station.”

To make the most of this invaluable opportunity, the research team is sending two forms of moon soil bricks—cylindrical and slab-shaped—into space:
– The cylindrical bricks will primarily undergo mechanical testing.
– The slab-shaped bricks, with larger exposed surfaces, will be used for thermal and radiation effect tests.

In addition to their different shapes, these moon soil bricks incorporate five distinct simulated lunar soil compositions and three different sintering processes, providing accurate data for the future construction of lunar bases.

Professor Zhou clarified, “We are using five different components, including those mimicking the lunar mare, like the site where Chang’e 5 landed, which primarily consists of basalt. We also include compositions resembling those that will be used by Chang’e 8 and Chang’e 7, which will land on the highlands, primarily characterized by plagioclase.”

He concluded, “Similar to Earth, soil composition varies across different regions on the moon. Investigating the degradation patterns of these bricks in the space station environment will give us solid scientific data for material selection and process optimization.”