Leonard David's INSIDE OUTER SPACE

Image taken by mini-rover of Change’-6 lander/ascender spacecraft on the far side of the Moon.
Image credit: CNSA

China’s new set of lunar collectibles, scooped up by the country’s Chang’e-6 Moon sample mission, owes a tip of the space helmet visor to a research team at the Hong Kong Polytechnic University (PolyU).

In collaboration with the China Academy of Space Technology (CAST), a “Surface Sampling and Packing System” for the task was set in stone – or set in lunar regolith that is!

Chang’e-6 scooping operation on Moon’s far side.
Image credit: CNSA/CLEP

On June 3, following the soft landing of the Chang’e-6 probe on the Moon’s far side, the PolyU-developed system accomplished the tasks of automatic sample collection and packaging on the lunar surface.

If all goes according to plan, samples from the first-ever lunar far side mission are returning to Earth on June 25.

Artwork depicts the parachuting to Earth of the Chang’e-6 capsule toting its lunar collection.
Image credit: CNSA/CCTV/Inside Outer Space screengrab

Sealing and packaging

PolyU was involved in the design and manufacturing of Samplers A and B, together with two accompanying high temperature near-field cameras for multiple-point surface sample collections, and automatic vision guidance of the lunar topside sampling.

The sampling process started with the near-field cameras mounted on the lander/ascender’s robotic arm next to Samplers A and B.

Yung Kai-leung introduces PolyU-developed “Surface Sampling and Packing System” for the Chang’e-6 mission. Image credit: PolyU

These cameras guided the sampling and sample deposition into the sample container, part of the primary sealing and packaging system.

Upon the completion of the sampling process, the tightly-sealed container was then vision-guided by the near-field cameras for automatic and precise insertion into the Chang’e-6’s ascender. That spacecraft segment subsequently rocketed off the Moon with its cache of lunar collectibles.

Group photo of Yung Kai-leung (center) and his research team at PolyU’s Industrial Center.
Image credit: PolyU

Lunar soil storage

PolyU researchers have also used advanced topographic mapping technologies to evaluate and identify the best landing sites for spacecraft.

That work has supported China’s lunar exploration missions, including Chang’e-3, Chang’e-4 and Chang’e-5, as well as the Mars exploration mission, Tianwen-1.

PolyU-developed a “Surface Sampling and Packing System.”
Image credit: PolyU

In 2021, PolyU established the Research Center for Deep Space Explorations and in the following year established the Joint Research Center of Advanced Aerospace Propulsion Technology in collaboration with the Academy of Aerospace Propulsion Technology.

The Space Resources Laboratory of the PolyU Deep Space Exploration Research Center has set up a lunar soil storage and sample analyzer capability to properly store and study lunar soil in depth.

“The far side of the Moon lacks any protection like magnetic fields or atmosphere at all, and features lots more impacts from meteors. The basin that was visited this time is a huge crash crater on the far side of the Moon, which is very old, possibly capable of ejecting substances from the deep lunar crust, or even from the lunar mantle,” Yung told CCTV.

Image credit: PolyU

“For this reason, I hope that with the retrieval of lunar mantle material, we will have some clues as to what exactly is inside the moon,” Yung commented.

Express mail cargo

Launched from south China’s Hainan Province on May 3, the Chang’e-6 mission’s lander-ascender combination later touched down in the South Pole-Aitken (SPA) Basin on the Moon.

After completing its collection of lunar specimens, the ascender blasted off from the lunar surface with its express mail cargo.

Artwork depicts ascender reaching orbiter to enable return of lunar samples.
Image credit: CGTN/Inside Outer Space screengrab

The ascender then re-united with the Chang’e-6 orbiter for the sample transfer. The mission’s returner segment is awaiting the optimal time to start its journey back to the Earth.

Drilling process

The far side grab-bag of Moon bits and pieces was completed within two days, done by two methods of sampling: use of a drill to collect subsurface specimens and the grab of samples on the surface with a robotic arm.

According to China Central Television (CCTV), the drilling process used a set of sampling equipment consisting of three layers, with a designed length of 8 feet (2.5 meters). The outer layer is the drilling rod, closely followed by the core tube, and the core tube is wrapped with a core bag.

As the drill bit was drilling downward, the core bag was also moving downward along with the core tube, and the sample was pushed into the bag. Once the sampling was completed, the core bag was wrapped and positioned onto the primary sealing device.

Chang’e-6 drilling gear.
Image credit: CCTV/Inside Outer Space screengrab

Plasticity and toughness

“During the drilling process, the drilling rod must be wear-resistant and difficult to deform. Excessive deformation would hinder the retrieval of lunar soil. The drilling rod must possess sufficient plasticity and toughness to prevent any cracking throughout the entire drilling operation,” said Ma Zongyi, a researcher with the Institute of Metal Research of the Chinese Academy of Sciences.

In order to ensure capability and stability of the drilling rod while further reducing its weight, the researchers developed tough aluminum-based composite materials. The wear resistance and strength of the drilling rod made from these materials can rival that of steel, while reducing the weight by 65 percent, reported CCTV.

Image credit: CCTV/Inside Outer Space screengrab

53-day journey

Researcher, Jiang Haichang, also with the Institute of Metal Research of the Chinese Academy of Sciences, told CCTV:

“The tube is integrally molded. And it is very long. In order to reduce weight during the lunar landing process, the wall of the tube needs to be very thin, which poses significant challenges in the manufacturing process. We have to update the molds and fixtures accordingly,” said Jiang.

The Chang’e-6 returner capsule, toting lunar samples collected in the South Pole-Aitken Basin on the Moon, is slated for touch down at a landing area within Siziwang Banner in north China’s Inner Mongolia Autonomous Region.

That parachute landing will signify the end of Chang’e-6’s 53-day journey of flying to the Moon and back.