How China responds to cracks in the window of Shenzhou-20
Print Edition
CHINA’S first emergency space launch began with something barely noticeable: a small triangle-shaped mark on a window of the Shenzhou-20 return capsule.
On November 5, one day before the planned return of the Shenzhou-20 crew, astronauts conducting routine checks discovered the mark on the window’s edge.
The crew — Chen Dong, Chen Zhongrui and Wang Jie — had been in orbit for more than 180 days and had just completed a handover with the newly arrived Shenzhou-21 astronauts at China’s Tiangong space station.
The astronauts took photographs from various angles, and the station’s robotic arm captured images from outside. Ground engineers reviewed these images and identified the mark as “penetrating cracks.”
Jia Shijin, chief designer of the manned spacecraft system from China Academy of Space Technology, told China Central Television that the shape “looked like a small triangle.”
As a precaution, mission controllers postponed the return for 12 hours to ensure safety.
Shenzhou windows feature a three-layer design, with the outer layer serving as part of the heat shield. Jia explained that the cracks posed a higher risk during re-entry to the atmosphere, where temperatures can exceed 1,000 degrees Celsius. In a worst-case scenario, the cracks could spread, causing the outer pane to detach — with this leading to the failure of the inner pressure-sealing glass, resulting in cabin depressurization and the ingress of high-speed gases.
After checking past data, engineers concluded the design had no flaws and that a tiny piece of space debris, likely less than 1 millimeter wide, was the probable cause.
By November 8, the capsule was declared unsafe for carrying astronauts back to Earth.
“It came very suddenly,” Ji Qiming, assistant director and spokesman for the China Manned Space Agency, said in a recent CCTV interview.
“But it was already covered in our contingency plans. When needed, we have procedures in place to respond.”
Supplies on the space station were stable as the life-support system recycles water and produces oxygen through electrolysis. Food stocks were also sufficient for the six astronauts from the two crews. The astronauts continued experiments and trained for possible changes to the return plan.
On November 10, China activated its emergency protocols. The Shenzhou-20 astronauts began preparations for their return using the Shenzhou-21 spacecraft.
Meanwhile, at the Jiuquan Satellite Launch Center in northwest China’s Gansu Province, teams initiated a compressed 16-day schedule to prepare the unmanned Shenzhou-22 for launch to provide a new return vehicle for the Shenzhou-21 crew.
On November 14, mission control instructed Shenzhou-21 to undock from the Tiangong space station.
The spacecraft carried the three Shenzhou-20 astronauts and four laboratory mice that had exceeded their planned experimental timeline. To support the animals during the delay, the astronauts used some of their water and soybean milk.
The return capsule landed at 4:40pm on November 14. Recovery teams quickly located it, and the astronauts exited in good condition. All mice also returned in healthy condition.
The crew spent 204 days in orbit, setting a new record for the longest duration of a single Chinese mission. Chen Dong became the first Chinese astronaut to spend more than 400 days in space.
On November 25, the unmanned Shenzhou-22 was launched, carrying supplies, medical kits, fresh vegetables, fruits and a special device designed to reinforce the cracked window of Shenzhou-20.
Using external keys kept on the station for emergency scenarios, the orbiting astronauts opened the Shenzhou-22’s hatch after the craft docked with the space station.
Shenzhou-20 will return later without a crew so that engineers can collect real re-entry data. The results will guide future improvements as the amount of space debris in low Earth orbit continues to increase.
The incident also created a gap in China’s crew numbering sequence. Since crew names correspond to their spacecraft numbers, there will be no “Shenzhou-22 crew” recorded.
“The empty designation will serve as a reminder that even after many successful missions, risks in space operations remain, and standards must stay high,” said the chief designer Jia.
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