Introduction

After completing lunar surface sampling, the Chang'e 6 lander successfully deployed the Chinese national flag on the far side of the moon. This marked China's first independent dynamic display of the national flag on the moon's far side, following the "fabric version" of the national flag displayed by Chang'e 5 in December 2020.

The "Rock Version" National Flag

Development Process

The "rock version" of the Chinese national flag was created using a composite material primarily made from basalt from the Taihang Mountains, with basalt making up 62% of the material. A team led by Academician Xu Weilin from the State Key Laboratory of New Textile Materials and Advanced Processing Technology at Wuhan Textile University, in collaboration with multiple institutions, spent nearly four years overcoming international challenges in basalt ultrafine fiber spinning, yarn production, weaving, and color construction. They successfully developed a high-quality fabric flag that could be displayed dynamically on the moon without temperature control protection.

Why Basalt?

Material Selection

Compared to Chang'e 5, which reached the lunar surface after seven days in space, Chang'e 6 took 30 days from its launch on May 3rd to land on the moon, significantly increasing the time. The flag needed to endure repeated high and low-temperature cycles during the journey and landing, demanding higher environmental resistance. Basalt, chemically similar to lunar soil, was chosen for its excellent thermal insulation and radiation resistance, making it suitable for the moon's harsh environment. Professor Cao Genyang explained that basalt is abundant on the moon and could be used for constructing lunar bases, saving costs by utilizing local materials instead of transporting them from Earth. The Chang'e 6 basalt flag represents an exploration of in-situ manufacturing on the lunar surface.

Ensuring Successful Display of the "Rock Version" National Flag

Overcoming Challenges

Basalt fibers are inorganic, smooth, brittle, and have high modulus, making it challenging to produce ultrafine yarns and fabrics with high color fastness. The development team innovated with "core-spun technology" and created a "turn core spinning" device to successfully tame basalt fibers. They produced a high-quality fabric flag that withstands extreme conditions such as high vacuum, temperature cycles, and intense UV radiation.

The Chang'e 6 lunar flag, measuring 300mm x 200mm (similar to A4 paper), uses ultrafine basalt fibers with a diameter about one-third that of a human hair. Despite the higher density of basalt fibers, the final flag weighs only 11.3 grams, 0.5 grams lighter than the Chang'e 5 flag.

Basalt Fiber: From Small Stones to Big Industry

Future Applications

While developing the "rock version" national flag for Chang'e 6, the team also explored expanding basalt fiber applications to areas requiring heat resistance and flame retardancy. These include flame-resistant protective clothing and high-flame-resistant luggage, leveraging the ultrafine basalt fibers' ability to withstand high temperatures.

Academician Xu Weilin predicts that basalt fibers, as lightweight and flexible protective materials, will see increasing use in aerospace applications, such as spacesuits, spacecraft, and lunar bases. The potential for basalt fibers in various high-tech fields is vast, promising significant industrial advancements.