Base on the Moon: Brick by Brick

Have you ever watched science fiction movies featuring bizarre and spectacular alien architectures or read novels that transport you to space life? The line between fiction and reality is blurring as China embarks on an ambitious journey to construct bases on the moon. Led by the National Digital Construction and Innovation Center at Huazhong University of Science and Technology, the team, under the guidance of Academician Ding Lieyun, chief scientist at the center and leader in the development of lunar soil bricks, set to revolutionize lunar construction.

What Lunar Soil Bricks Are?

Lunar soil bricks are a type of building material developed by Chinese scientists for the construction of future moon bases. These bricks are created by sintering a material that closely mimics the composition of actual lunar soil.

Why are such bricks necessary? Building structures on the Moon is no easy feat. Engineers must contend with extreme temperature swings, low gravity, the vacuum of space, intense radiation, moonquakes, and even impacts from micrometeorites. Traditional building materials from Earth wouldn’t survive these harsh conditions, making lunar-specific solutions like these bricks a critical breakthrough.

Interestingly, lunar soil bricks share a similar density to conventional building materials, such as red bricks, grey bricks, and concrete blocks. However, their strength is where they truly shine. These bricks boast a compressive strength of more than three times greater than standard red or concrete bricks. They can support over a ton of weight on just one square centimeter of their surface. This impressive durability makes them perfectly suited for the Moon’s demanding environment.

How Lunar Soil Bricks Are Made?

What does it take to craft lunar soil bricks? The Moon’s complex surface environment demands exceptionally high performance from these bricks. So, how are they formed? The process involves vacuum hot-press sintering and can be broken down into three main steps.

First, the simulated lunar soil is carefully weighed and placed into a mold. Since lunar soil is highly loose and granular, it must be compacted in the mold to form a stable preform. Engineers ensure uniform pressure is applied during this stage to create a solid base.

Once compacted, the preform—still encased in the mold—is transferred to a vacuum hot-press furnace. Insulation is added to maintain consistent heat, and the entire apparatus is sealed. The furnace is then heated to temperatures exceeding 1000°C to sinter the material.

Scientists found that using an electromagnetic induction furnace can raise the temperature to over 1000°C in about 10 minutes. Tests have shown that sintering in an inert gas environment produces the highest strength, reaching over 100 MPa. In a vacuum, effective sintering can occur at 1000–1100°C, and adding pressure can further shorten the sintering time.

The team, led by Ding Lieyun, has conducted extensive trials using three sintering methods: vacuum sintering, inert gas sintering, and air sintering. Each approach has been carefully evaluated for its effectiveness, with inert gas sintering demonstrating the greatest material strength. The final specifications of lunar soil bricks must align with the Moon’s environmental requirements, ensuring they can withstand extreme conditions such as low gravity, high vacuum, and wide temperature fluctuations.

What In-Situ Forming Technique Is?

The in-situ forming technique refers to a construction method that utilizes locally available resources to create building materials directly on-site. In the context of future lunar research stations, this approach enables the use of lunar regolith, solar energy, and other lunar minerals to fabricate construction components.

Why is this method essential? Transporting prefabricated building materials from Earth to the Moon is both costly and logistically challenging. By relying on lunar in-situ resources, the need for heavy payloads is eliminated, significantly reducing the overall cost of construction on the Moon.

Simulated “lunar soil bricks” are currently undergoing space exposure experiments to evaluate their performance under harsh space conditions. These tests will provide critical data on how the bricks behave and degrade, helping scientists refine their properties and optimize construction methods. This research is paving the way for the practical implementation of lunar base construction, ensuring that future designs are both efficient and resilient.

Overcoming Challenges in Lunar Base Construction

Building a lunar base is no small feat, requiring solutions to overcome extreme temperature fluctuations, low gravity, high vacuum conditions, intense radiation, moonquakes, and impacts from micrometeorites. Designing suitable structures for the lunar surface has been an ongoing challenge for Ding Lieyun’s team. Their experiments have included dome, arch, and columnar designs, each iteratively tested to balance environmental compatibility with ease of construction.

One of their most promising concepts, the “Moon Jar,” features a double-dome structure incorporating 12 design parameters. This design maximizes interior space while minimizing stress, optimizing thermal insulation, and reducing material weight. The use of lightweight materials and minimal resource consumption further enhances its feasibility.

For construction, 3D printing emerges as a key technology. However, it must overcome significant hurdles: rockets currently lack the capacity to transport heavy equipment, and materials must meet specific flow and stability requirements. For instance, lunar soil needs sufficient flowability to be extruded during 3D printing. If it flows poorly, the structure cannot be formed; if it flows too well, it collapses. Achieving the right balance of flowability and stability is a complex task requiring extensive research.

Ding’s team has proposed an innovative 3D printing method that begins with foundation reinforcement using slurry injection, followed by structure printing directly on the lunar surface. For domes, an inflatable airbag is used as a mold, onto which layers are printed to complete the structure. While this method allows for the construction of various shapes, challenges such as the continuous nature of 3D printing, the difficulty of single-pass large-scale forming, and high energy consumption persist.

To address these issues, the team has creatively drawn inspiration from traditional Chinese masonry and mortise-and-tenon techniques. By sintering lunar soil into bricks with interlocking structures, they propose an assembly-based approach. These bricks, with their intricate joints, can be robotically assembled into stable structures. 3D printing can then be employed to reinforce connections, ensuring structural integrity while reducing the risks associated with one-time large-scale formation. This hybrid technique represents a significant step forward in lunar base construction, combining traditional principles with cutting-edge technology.

Exposure Experiments: A Critical Step in Lunar Soil Brick Research

Exposure experiments play a pivotal role in evaluating lunar soil bricks, designed to withstand the Moon’s extreme environmental challenges. Lunar days can reach scorching temperatures of over 180°C, while nights plummet to -190°C. The absence of an atmosphere subjects the Moon’s surface to intense cosmic radiation, frequent micrometeorite impacts, and high-frequency moonquakes. These factors place stringent demands on the mechanical, thermal, and radiation-resistant properties of lunar construction materials.

Space-based testing is essential to validate the performance of lunar soil bricks under such conditions. These tests provide critical insights for material selection and process optimization, enabling the development of robust structures for lunar bases. The current batch of bricks, created using simulated lunar soil modeled on samples returned by the Chang’e-5 mission, includes three sample panels comprising 74 smaller specimens. These samples feature various shapes, such as sheets, columns, and spheres, reflecting diverse potential applications.

Recently, these lunar soil bricks were successfully sent to the Chinese Space Station aboard the Tianzhou-8 cargo craft. Over the next three years, they will undergo exposure experiments in space to simulate the degradation they might experience in the lunar environment. This testing aims to evaluate their long-term stability and reliability.

During the experiment, the bricks will be directly exposed to the harsh conditions of outer space, including cosmic rays, solar radiation, and micrometeorite impacts. Researchers will conduct periodic inspections, gathering data on their degradation over time. Key parameters to be measured include changes in dimensions, weight, structural integrity, thermal conductivity, and radiation damage.

This data will be invaluable in refining the design and manufacturing processes of lunar soil bricks. By understanding how these materials respond to space conditions, scientists can enhance their performance, ensuring they meet the rigorous demands of lunar construction. These findings will lay a solid foundation for building resilient and sustainable lunar habitats in the future.

Upon the completion of the space exposure experiment, the first batch of lunar soil bricks subjected to space conditions is expected to return to Earth by the end of 2025. These bricks will be brought back aboard a spacecraft.

Once retrieved, researchers will conduct comprehensive analyses of the bricks to assess their potential for practical application in the lunar environment. This detailed investigation will focus on evaluating their performance under the Moon’s extreme conditions and determining their suitability for future lunar base construction.

The findings from these studies will provide critical scientific evidence and technical guidance for the design and implementation of lunar habitats. By leveraging these results, scientists can further optimize materials and construction techniques, ensuring the feasibility and durability of lunar infrastructure in the decades to come.