Chinese scientists have made improvements for the porthole of the Shenzhou-23 spaceship at the launch site to avoid potential emergency situations caused by space debris.

The Shenzhou-20 spaceship's return capsule viewport window suffered a suspected impact from space debris during its mission last year. The three Shenzhou-20 astronauts returned safely aboard the Shenzhou-21 spaceship on November 14, 2025, and later on November 25, China launched the Shenzhou-22 spaceship to provide a return vessel for the three Shenzhou-21 astronauts, who are currently in orbit.

To avoid such a potential emergency during the Shenzhou-23 mission, the porthole improvements were implemented ahead of schedule.

According to the original plan, the porthole upgrade was scheduled for implementation on the Shenzhou-24 spacecraft. However, after the Shenzhou-20 experienced an in-orbit space debris impact that affected the astronauts' return, the team conducted a comprehensive assessment and decided to advance the upgrade to Shenzhou-23 to ensure a smooth and safe mission.

"The previous version of the viewport window had one layer of anti-ablation glass, while we increased that to two layers for the new window for dual redundancy," said He Yu, chief commander of Shenzhou spacecraft of the China Aerospace Science and Technology Corporation.

"In addition, we have taken an extra protective measure as a final safeguard inside the capsule. These make up a three-layer anti-ablation function, adding an extra insurance for the astronauts to work and live safely and securely in orbit, and to return safely," He said.

Under normal circumstances, the viewport windows are installed at the spacecraft assembly workshop in Beijing before the capsule is assembled with other ones. But, since the Shenzhou-23 had already been manufactured and placed on emergency standby at the Jiuquan Satellite Launch Center, the porthole upgrade was conducted after all three modules had already been assembled – a process much more difficult due to the confined space inside the capsule.

The return payload transport capability of the Shenzhou-23 spacecraft has also been enhanced. 

"The previous functional specification was 50 kilograms. Now it exceeds 100 kilograms, and the payload volume is three times larger than before," said He.

The increased payload volume refers to the available space for carrying items. He explained that the improvement in downmass capability stems from two key modifications: the miniaturization upgrade of the cabin's instrumentation system and the intensive reconfiguration of interior space layout. Together, these changes freed up weight and spatial resources, enabling the Shenzhou-23 to bring more scientific experiment payloads and other items back to the Earth upon its return.

Astronauts Zhu Yangzhu, Zhang Zhiyuan and Lai Ka-ying will carry out the Shenzhou-23 manned mission to China's space station, and one of them will stay in the space station for a year.