Lithium battery is "new", and the power supply of Shenzhou spacecraft has entered a new era

On the 25th, at the Jiuquan Satellite Launch Center, the Shenzhou-18 manned spacecraft was lifted off by the Long March-2F carrier rocket. In 21 years, 13 manned missions, the Shenzhou manned spacecraft has successfully sent 22 astronauts and 35 people into space, with a mission success rate of 100%.

The power supply of the Shenzhou spacecraft has been improving, and its ability to cope with the complex environment of space has been continuously upgraded, and the management experience of coping with the high-density launch and development of models has become more and more mature. "Through local improvements, gradual iterative upgrades, so that 'feel good' continues to resound in space," said Zhong Danhua, a technical expert at the Eighth Academy of China Aerospace Science and Technology Corporation.

Hello, Lithium Battery!

The successful launch of Shenzhou-18 is an important milestone in the power supply of the Shenzhou spacecraft. The large-capacity, long-life, and high-reliability lithium-ion battery will take over the "baton" of the large-capacity cadmium nickel battery of the "veteran of the 17th Dynasty" of the Shenzhou spacecraft and start a new journey of power supply for the Shenzhou spacecraft.

However, the new "member" lithium-ion battery is not a "new recruit" in the aerospace industry with a "blank resume". Zhong Danhua introduced that the long-life and large-capacity lithium-ion battery used in the Shenzhou spacecraft has been successfully applied in spacecraft such as space stations and cargo spacecraft, and its safety and reliability have been widely verified, "higher specific energy, longer cycle life, better high-rate charging, and about 50 kg of weight reduction for the whole ship, which further meets the mission needs of the Shenzhou spacecraft in the application and development stage of the space station." ”

New "members" start another new journey. The power supply research and development team of the 811 Institute continued to explore and upgrade the charging control mode of lithium-ion batteries again, "using the all-hardware charging control mode, and the safety redundancy adopts the triple redundancy control mode, each of which can work independently and back up each other, which is equivalent to the 'triple insurance' for the safety of the battery." In each charging control mode, it fully integrates the rigorous style of excellence and meticulousness of the 811 research and development personnel, adopts fault-tolerant design such as multi-mode redundancy, and upgrades the structure of the charging controller accordingly, as well as the connection mode between the modules, etc., Zhong Danhua revealed, "This is the highest safety and reliability in the current domestic full hardware control system." ”

Compared with other spacecraft, the working environment of the power supply of the Shenzhou spacecraft is more complex. There is a large load of autonomous power supply when a single ship flies, there is a grid power supply to accept the space station when the shading is serious and the lighting conditions are poor, as well as the safe power supply on the way back, emergency power supply in the event of a failure, etc., all of which require the "excellent staff of the space station" lithium-ion battery and his "predecessor" cadmium nickel battery to accept the same rigorous assessment. Adhering to the concept of "not causing trouble to others", the upgrading and replacement of lithium-ion batteries can only give full play to the maximum initiative of the original "one acre and three points of land" of the original nickel-cadmium battery, which can be described as challenging.

Behind the success of every mission is the persistence of countless people who go all out. From product development to delivery, the R&D personnel of the 811 Institute spent four years to complete a large number of ground tests and verifications, and completed various matching tests with the whole ship. "Use the maximum charge and discharge rate to assess, use the longest shelving time to tighten, and use the temperature upper and lower boundaries of lithium-ion batteries in various working modes to verify, and interpret the characteristics of the 'Space Life Boat' with the highest requirements for reliability and safety and the highest working standards from the subtleties," Zhong Danhua said.

Advances in power supply are used to better help manned space projects

Looking back on the history of the Shenzhou manned spacecraft, since the Shenzhou-1 flight in 1999, in the past 20 years, along with the mission needs of all stages of the manned space project, the power supply of the spacecraft at each stage contains exploration and breakthroughs. What has changed is the continuous improvement of the product capability of the spacecraft power supply, the continuous progress and innovation in the field of manned spaceflight on the mainland, and the constant is the high reliability and high safety standards that have been adhered to.

In the first stage of the manned space project, the power supply from Shenzhou 1 to Shenzhou 7 has experienced a story from scratch and starting from scratch. On the basis of comprehensively absorbing the development experience and lessons at home and abroad, the research and development team determined the spacecraft power supply system mode with a variety of power supply combined power supply after several rounds of demonstration and research, including a silicon solar cell with a photoelectric conversion efficiency of about 15% for the spacecraft, a 65 Ah nickel cadmium battery, and a zinc-silver battery with the longest service life in China at that time, and the power supply capacity of the whole ship was greater than 1200 watts. These filled the gaps in a number of domestic space power supplies at that time. The next few ships have successively overcome the problems of connecting different types of power supplies to the grid, meeting the needs of expanding the launch window, simulating and simulating power failures, and further improving the reliability and safety design, so as to achieve the goal of making Shenzhou "go up" and "come back".

With the full development of the second phase of China's manned spaceflight project, it is necessary to provide larger-scale power supply capacity in order to realize the manned rendezvous and docking mission between two spacecraft and solve the problem of space applications with a certain scale and short-term manned care. Since Shenzhou 8, the power supply system of the spacecraft has undergone a major upgrade on the basis of the previous stage. The power supply structure has been upgraded from two units to three units, using a three-junction gallium arsenide solar cell with a photoelectric conversion efficiency of about 28%, the capacity of the nickel-cadmium battery has been upgraded to 70 Ah, the service life of the zinc-silver battery has been increased by 100%, and the power transmission and control functions of the power supply have also been redesigned. "It can meet the load demand of more than 1,800 watts for the whole ship, and establishes a baseline for the power system of the subsequent spacecraft. It is also from this point on that the upgraded spacecraft power supply system has joined hands with the Tiangong-1 target vehicle with stronger power generation capacity and the Tiangong-2 space laboratory, allowing astronauts to have a hot meal in space at any time.

Since 2020, the curtain has been slowly opened on the construction of the space station. On the basis of the second phase, Shenzhou 12 to Shenzhou 15 will further improve the ability of the power supply to adapt to different use environments. The power supply has the rapid launch capability of long-term standby and emergency rescue at the launch site, and at the same time, it can adapt to the complex occlusion situation and carry out grid-connected power supply with the space station under the state of "one-word configuration", "L-shaped configuration" and "T-shaped configuration". "Whether it is radial docking, forward docking, inertial flight, and ground flight, the power supply has passed the key technology verification of the space station and the complex assessment of all flight conditions in the construction stage, and has successfully ensured the safety of energy supply at the spacecraft system level, and has performed 'robustly'."

Entering the space station application and development stage, the Shenzhou spacecraft began batch production. In order to better withstand various complex external forces in the normal operation stage of the space station, the power supply of Shenzhou-16 and Shenzhou-17 has successively upgraded the drive system and drive mechanism of the solar cell wing to ensure the robustness of the power supply.

It is worth mentioning that Shenzhou 18 not only iteratively upgraded the battery of the main power supply and its charging control mode, but also extended the life of the zinc-silver battery used in the return power supply, emergency power supply, and pyrotechnic power supply again, "The service life of the zinc-silver battery has been increased by 20%, which can support the Shenzhou spacecraft to dock in orbit for a longer time." Through the gradual improvement of the power supply product capability, we will continue to broaden the use boundary of the mission and better help the entire space station engineering task," said Zhong Danhua.