A research fellow presents bricks made from simulated lunar soil, a potential building material for future habitats on the moon. The bricks have a density comparable to that of ordinary ones, but their compressive strength exceeds that of standard red bricks and concrete bricks by more than three times. Photo: CCTV

Bricks made from simulated lunar soil, a potential building material for future habitats on the moon, are scheduled to be sent to China's space station for exposure experiments, with the first brick anticipated to return to Earth by the end of 2025.

The bricks made from simulated lunar soil have a density comparable to that of ordinary bricks, but their compressive strength exceeds that of standard red bricks and concrete bricks by more than three times, with one square centimeter able to support over one ton of weight, according to China Central Television (CCTV).

The combination of these durable bricks employs mortise and tenon techniques, making them more suited for the structural design of future lunar bases, said Zhou Cheng, a professor from National Center of Technology Innovation for Digital Construction, as reported by CCTV.

However, building a house on the lunar surface could face challenges due to drastic temperature changes on the moon, with temperatures exceeding 180 C during lunar days and reaching -190 C at lunar night. 

As the moon rotates and orbits, day and night occur on different parts of its surface, with lunar day and night each about two Earth weeks long. 

Without atmospheric protection, significant levels of cosmic radiation and many micrometeorites would also hit the surface of the moon, and there is frequent moonquake activity. All of these will place demanding requirements on the mechanical, thermal and radiation resistance properties of lunar surface construction materials.

As these bricks are set to travel to the Tiangong Space Station aboard the Tianzhou-8 cargo craft to test their suitability for building habitats on the moon, Zhou outlined three key properties of the bricks that will be verified, including the potential degradation of their mechanical properties, their heat preservation and insulation effectiveness, and their ability to withstand cosmic radiation on the moon.

The whole process of making such bricks by vacuum hot pressing and sintering is divided into three steps, Zhou explained. Researchers need to weigh the simulated lunar soil and then place it in the mould according to its weight. They have to press it into the mould container as the lunar soil is very loose.

The researcher will then put it into the vacuum hot-pressing furnace. After locking the whole vacuum experimental device, it can be heated up and sintered, Zhou introduced.

The lunar soil material that the researchers modeled in the lab is similar to the Earth's soil, which is dispersed. To process it, researchers must subject it to high temperatures. 

Zhou noted that the process does not involve any additional material additives, making it a highly promising construction method for future lunar base development, allowing the use of in-situ resources on the moon, such as lunar soil, solar energy, minerals to build a house, eliminating the need to transport prefabricated building components from the Earth. 

Such an approach could greatly reduce the cost of lunar surface construction. These simulated bricks will be exposed to experiments in space to accumulate scientific data for building houses on the moon in the future, so as to optimize the actual scheme, according to CCTV.

Whether for scientific research or construction on the moon, transporting materials from Earth is impractical, Wang Yanan, chief editor of Beijing-based Aerospace Knowledge magazine, told the Global Times on Sunday. Given the current capacity of rockets, the valuable room of each launch should be reserved for personnel, essential equipment, and supplies. 

Therefore, lunar soil is an abundant and easily accessible building material, which solves the problem of obtaining raw materials in situ on the moon, Wang noted.

The total planned exposure period for the bricks is three years, so every year researchers will return one sample panel exposed on the space station to Earth and conduct related experiments, Zhou said.

The research team also designed the bricks in two shapes: columnar and flaky. The pillar-shaped lunar soil bricks are primarily intended for mechanical testing, while the larger-exposed flakes are used to assess thermal and radiation effects, according to CCTV.

In addition to their various forms, these bricks are made from five simulated compositions of lunar soil and undergo three distinct sintering processes, providing more accurate scientific data for the construction of future lunar bases.

China's lunar exploration program will carry out two more launch missions to lay the groundwork for the International Lunar Research Station (ILRS), with the first launch expected to take place as early as 2026, announced the China National Space Administration in September.