This photo taken on June 25, 2024 shows the retrieval site of the returner of the Chang'e-6 probe in Siziwang Banner, north China's Inner Mongolia autonomous region. (PHOTO: XINHUA)

By LIN Yuchen & Fu Yifei

According to China National Space Administration, on June 25, the Chang'e-6 returner, carrying the sample of lunar farside, successfully landed in Siziwang Banner, Inner Mongolia. The return journey from space to the predetermined landing site was complex and fraught with challenges. According to the China Aerospace Science and Technology Corporation (CASC), a series of advanced technologies ensured the safe return of Chang'e-6.

'Space skipping stone' method

The returner re-entered Earth's atmosphere at nearly the second cosmic velocity, using a technique called "semi-ballistic skipping reentry." This method involved the capsule "skipping" across the atmosphere like a stone on water, using atmospheric drag and heat to slow down. The guidance, navigation, and control (GNC) system developed by CASC played a crucial role in executing this complex maneuver.

Crafting the ultimate heat shield

The returner had to withstand extreme temperatures during re-entry. Drawing on the experience of the Chang'e-5 mission, researchers designed a heat- and ablative-resistant "coat" for the capsule, according to the different burning resistance and heat insulation requirements of its different parts. A precise welding technique is required to ensure the thin-walled structure could endure the intense heat and pressure.

Parachute system to ensure safe landing

Once the returner entered the atmosphere, the parachute system developed by CASC took over the duty of decelerating. It consisted of a two-stage deceleration process: an initial small parachute to slow the capsule and a larger main parachute to reduce the speed to a safe- landing velocity. Additional components, such as recovery controllers and ejection systems, worked in unison to ensure a precise and safe popping up of parachutes.
The successful return with lunar samples from the moon's far side marks a new milestone in space exploration.