At 20:59 on April 25, 2024, the Shenzhou-18 manned spacecraft, which carries three astronauts, was successfully placed into the designated orbit by the Long March 2F launch vehicle, signaling a complete success of the launch mission. Astronauts Ye Guangfu, Li Cong, and Li Guangsu will complete the on-orbit rotation with the Shenzhou-17 crew. Six astronauts will stay in orbit together for a short term, presenting the Shenzhou spacecraft with a brand new challenge. 

After entering the application and development stage of space stations, China has successfully launched three Shenzhou manned spacecraft. These spacecraft dock with the space station and berth at both the forward and radial docking ports alternately, providing personnel transportation services for the operation of the space station. Shanghai Academy of Spaceflight Technology is responsible for the development of the electrical power subsystem, docking mechanism subsystem, propulsion module structure and assembly, communication subsystem for tracking telemetry and command, propulsion module cable network and distributor for three modules of the system circuit subsystem of Shenzhou manned spacecraft. 

Long service life, high capacity

The power system of Shenzhou is fully upgraded

The electrical power subsystem is one of the most critical subsystems among the 14 subsystems of the spacecraft. It plays the role as the main power source for the whole spacecraft during its orbital flight, the emergency power supply that can ensure the safety of astronauts in critical stages, the power source for the return module to return and land after its separation from the propulsion module, and the power source of initiating explosive devices for the orbit module and return module, making it the heart of the spacecraft.

As a veteran of the electrical power subsystem, the nickel-cadmium batteries have successfully provided stable power support for 17 missions of the Shenzhou spacecraft. With the extensive application and thorough validation of long-life, high-capacity lithium-ion batteries, the electrical power subsystem of the Shenzhou manned spacecraft has been fully upgraded after 4 years of effort. The energy storage batteries of the main power source have been changed from nickel-cadmium batteries to lithium-ion batteries, with a capacity increase of over 30%. The diaphragm system of zinc-silver batteries in other power sources now exhibits improved oxygen resistance, resulting in a 20% increase in the service life. In the subsystem, six new fault countermeasures related to charge control and protection have been added, which greatly improves the adaptive ability of safety control strategies. Meanwhile, the modularization of electronic products and the increase in battery energy density have resulted in a reduction of over 50 km in the total weight of the spacecraft.

A small change can have an overall impact. The upgrade of the power source system has also imposed a significant impact on the propulsion module assembly. Inside the propulsion module of the Shenzhou spacecraft, in addition to the 40 engines of different sizes, there is also the electrical power subsystem, and other important equipment of multiple key systems for communication between spacecraft and ground station, attitude and orbit control, temperature control, and environment control, making it a real power hub of the spacecraft. To adapt to changes in various subsystems, the development team of the Shenzhou spacecraft of SAST rearranged the devices on the instrument panel of the propulsion module. Particularly, in response to the diverse devices of the electrical power subsystem and the complex requirements for the mechanical and thermal environment, they thoroughly considered the requirements for the distribution of mass centers of the module, load-bearing of structural mechanics, and optimization of cable layout, which matches the improved adaptability of the electrical power subsystem to form a perfect combination, and ensures the reliable and stable operation of power equipment inside the propulsion module.

Ensuring utmost accuracy

Achieving smooth and orderly docking

The Shenzhou-18 manned spacecraft is the second spacecraft realizing radial docking in the application and development stage of space stations. During radial docking, the obstruction of spacecraft measurement sensor by the hundred-ton space station combination, as well as mutual influence between plumes during the operation of the engine in the space station combination will pose significant challenges to the docking process. To eliminate the risks posed by these impacts, the performance parameter deviations of the 192 sensors, 18 actuating mechanisms, and 260 springs of each docking mechanism are minimized through development productization and process standardization, and 31 ground standard capture buffer tests have been conducted, validating that the docking mechanism has capture buffer abilities under 31 different complex conditions. So far, the androgynous peripheral docking mechanism has successfully completed 31 space docking tasks and 27 separation tasks in orbit, with stable status and reliable operation.

It’s worth mentioning that with the increasingly mature rendezvous and docking, and ground-space telemetry and telecontrol technologies of spacecraft, the air-to-air communication system will transmit the absolute positioning data of the spacecraft, critical control status data, telecontrol commands, telemetry data, etc. during the rendezvous and docking process, thus establishing a bidirectional communication link between the manned spacecraft and the space station. A “Magpie Bridge” for real-time voice communication is thus established for astronauts inside the manned spacecraft to communicate with astronauts inside the space station via the air-to-air communication link in a mission.

Deployment within 8 seconds

Ultra-long standby for 200 days

A rotating backup mode that “one spacecraft is launched, with the other standby for emergency rescue” was adopted for manned spacecraft early in the space station critical technology validation stage. In October 2023, the Shenzhou-17 manned spacecraft embarked on its journey. Over the following 200 days, the Shenzhou-18 manned spacecraft remained stationed in the earth orbit, ready for emergency rescue missions at any time. Generally, once the spacecraft is placed onto the orbit, the reliable deployment of solar panels in orbit is a crucial step to ensure energy supply. To ensure the reliable deployment of the spacecraft’s solar panels in orbit during long-term standby, the development team of SAST employed digital methods to control the variance of measured data of key products’ important indicators within one-thousandth during the product development phase. Then, based on the test results of ground components, they calculated the time required for the in-orbit deployment of spacecraft. Validated in the flight of multiple manned spacecraft, the solar panels have the ability for rapid and stable deployment and locking within about 8 seconds in orbit, demonstrating the ultra-long standby capability of the solar panels. This effectively validates the product’s lifespan and environmental adaptability under emergency standby conditions.

Nowadays, space flight is no longer an unreachable dream for humanity. Soon, the eighteenth Shenzhou spacecraft has set sail again, heading towards the Tiangong space station. As the “vessel of life” for astronauts to travel between Earth and space, the Shenzhou manned spacecraft is embracing increasingly mature technology and superior performance. However, for the development team of manned spaceflight, each spacecraft is more than just a replica. During the process of technical research, the team continuously explores and innovates, striving for precision and perfection, while always pursuing high reliability of spacecraft. These efforts are not only their response to the demands of the era and mission but also serve as milestones for their experience of the splendid moments in manned spaceflight development.