How China's astronauts train in a deep cave for space missions

Twenty-eight Chinese astronauts have recently completed a nearly month-long extreme environment training program inside a deep cave in Wulong, southwest China's Chongqing Municipality. Divided into four groups, they took turns staying continuously in the cave for six days and five nights. Far from a routine expedition, the exercise was designed as a highly realistic simulation of space missions.

With an average temperature of just 8 degrees Celsius and humidity reaching 99 percent, the cave's darkness, confinement and constant risks closely mirrored the isolation and challenges of spaceflight. Working in teams of seven, the astronauts followed real space mission schedules, carrying out more than a dozen intensive tasks including cave exploration, environmental monitoring and simulated space-to-ground communications.

Selecting the training site took months. Experts surveyed more than 10 caves across seven provinces and cities, seeking terrain complex enough to test astronauts while meeting strict safety standards. A critical hidden risk was radon, a radioactive gas. Candidate caves were monitored for a full year to ensure radon levels were completely safe before the cave in Wulong was finally selected as the training site.

The training posed serious challenges for the participants. Astronauts crawled through narrow rock crevices barely wide enough for one person, climbed and rappelled down cliffs tens of meters high using rope techniques and tackled carefully designed "surprise missions." These included sudden scenarios such as a simulated teammate injury to test emergency decision-making, or the transfer of "special materials" – moving an open bottle of water through rugged, confined passages without spilling a single drop. Each task placed teamwork, communication and adaptability under intense pressure.

Psychological resilience was another major focus. In darkness, astronauts experienced shifting mental challenges. Some reported that the early stage was dominated by cold and damp conditions that disrupted sleep, while later they developed distorted perceptions of time. Psychologists supported the teams through daily group discussions and continuous monitoring. Notably, astronauts from different cohorts bonded quickly, forging trust through shared challenges.

To support the training, more than 700 kilograms of equipment and supplies were delivered to the underground base using a combination of drone hoisting and human relay transport. All waste generated during the mission was carefully packed and removed, ensuring both scientific training and cave conservation.

From deep underground to outer space, this "downward" exploration was conducted to prepare for future "upward" journeys. The training enhanced astronauts' ability to cope with unknown risks, providing valuable experience for long-term space station missions and future crewed lunar exploration.