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Manned spacecraft system chief designer discloses Shenzhou-20 porthole crack details: report

Global Times

By Global Times Published: Dec 01, 2025 01:14 PM

It was a crack - measuring less than 1 millimeter - that went through all the way on the porthole of the Shenzhou-20 spacecraft reentry module, and the most likely cause of the crack was space debris, Jia Shijin, chief designer of the manned spacecraft system, with the China Academy of Spacecraft Technology under the state-owned space giant China Aerospace Science and Technology Corp (CASC), revealed details of the space emergency response of Shenzhou-20 spaceflight mission in an recent interview with the China Central Television (CCTV.)

The three astronauts of China's Shenzhou-20 mission landed safely on Earth aboard the Shenzhou-21 spacecraft on November 14, marking the first successful implementation of an alternative return procedure in the country's space station program history.

And on November 25, China launched the Shenzhou-22 spacecraft from the Jiuquan Satellite Launch Center in Northwest China, marking the first emergency launch mission in the country's manned space program.

On November 5, the return mission of Shenzhou-20 was hit with an emergency pause button. During a routine inspection of the spacecraft's reentry module the day before the planned return, the crew discovered a localized anomaly at the edge of the porthole. Jia received the on-site photos immediately after the astronauts reported this sudden situation.

At that time, it was not called a "crack" yet, Jia told the CCTV. "There was just a triangular mark, size of which was not very big. After an initial review of the downloaded images, it proved difficult to identify what exactly they depicted. It looked as if some kind of paint or lacquer sticking on top of it."

According to the CCTV report, the Shenzhou-20 crew took pictures of the mark from different angles and under different light conditions, and they also used the camera attached to the space station robotic arm to take pictures from outside of the cabin.

After the images were sent back to Earth, the ground system organized domestic experts on glass materials to study and evaluate such damage, according to the report.

First of all, we had to make a judgement on whether it was a crack. And if it was a crack, is it a through one or just a surface one. Finally, we reached a consensus that it was a through crack - the entire glass has been fully penetrated from its inner surface to its outer surface, the chief designer said.

We were astonished and could not even believe it. The probability of our spacecraft being hit is already extremely low — let alone the porthole, which is even more unlikely, Jia said.

According to the CCTV report, the spacecraft's porthole features a three-layer structure, with the outermost layer serving as a thermal protection shield. During reentry into the atmosphere, the porthole endures frictional temperatures exceeding 1,000 C, and the thermal protection shield acts as the first line of defense. This crack has essentially created a breach in the safety system, said the report.

Within 12 hours after determining the crack, the mission command decided to postpone the return.

Next, a most important task facing the project is to conduct a safety assessment of this crack, reviewing the entire development and production process of the Shenzhou-20 spacecraft's porthole, including test data, photos and all related materials, Jia stated.

After thorough review, we have even greater confidence in our product, its original design philosophy, the design solution, or the ground-based test and verification work we had conducted, Jia said. The most likely cause of this crack is space debris, because this glass has extremely high hardness and is also very thick.

When we conducted ground tests trying to simulate a crack in the glass, ordinary tools couldn't produce one at all, and we had to use a hammer, he said.

Jia revealed that our preliminary judgment is that the space debris was smaller than 1 millimeter in size, but its speed was extremely high.