Introduction to the Energy Management System of the Trial Version of China’s New-generation Manned Spacecraft
Shanghai Institute of Space Power-Sources is in charge of the overall research and development for the energy management function of the trial version of China’s new-generation manned spacecraft. As one of the five major functions of the spacecraft, the energy management function has realized a series of high-reliability designs on the basis of the power subsystem of Shenzhou spacecraft. It has also achieved multiple breakthroughs to meet the special demands of the trial version of new-generation manned spacecraft and completed the progress from Shenzhou spacecraft to the new-generation manned spacecraft in aspect of energy management function.
More secure: the only power system in China with “double security” of both main power supply and auxiliary power supply
It is no exaggeration to say that the energy management function of the new-generation manned spacecraft is highly reliable and highly secure, since it is the only power system with “double security” of both main power supply and auxiliary power supply in China at present.
“The energy management function of the trial version of new-generation spacecraft provides an auxiliary power which can carry out tasks independently in case that the main power completely failed. That means that there are two sets of power systems, the main power supply and the auxiliary power supply, and both can work independently, double security may it be called,” said Zhong Danhua, the Director Designer of the energy management system of the trial version of new-generation manned spacecraft.
In the main power supply of the spacecraft energy management function, redundancy design of multiple-unit balanced control and multiple-unit reliability has been adopted. The energy management function of the trial version of new-generation manned spacecraft has the maximum redundancy in China nowadays. There are three units in the body of the main power supply, with three sets of independent controller and solar arrays. In case that any unit fails, the remaining two units can complete the flight mission independently. Meanwhile, balanced design has been adopted for the three units, both balancing among three units and balancing in two units are available, in combination with redundancy design of multiple units, the consistency of discharging and recharging among multiple units has been ensured. It is not only “double security”, “multiple security” should it be called.
Innovative: “air supporting table + extended metal plate”is used for the first time in manned space platform
As the PLUS version of Shenzhou spacecraft, the trial version of new-generation manned spacecraft is twice the size of Shenzhou spacecraft in construction with 6 to 7 seats on-board comparing to 3 seats of Shenzhou spacecraft. The constructional design of the new module has brought a great challenge to the docking of solar array wing with the module, “the way that the traditional solar array wing furls and installs would cause the ground deployment hanging device of the solar wing interfering with the module while furling, make it unable to furl and install properly”, said Shu Bin, the chief designer of energy management function.
Our researchers conducted a series of surveys and found that while most spacecrafts had adopted the traditional hanging deployment solution, while some satellites had adopted air supporting deployment solution. The hanging deployment needs to resolve hanging interference problem above the concave module, while air supporting deployment needs to resolve the problem that the air supporting table could not extend into the concave module. Which one is better? It was hard to choose for a while! The researchers analyzed and discussed the whole process from production to launch of the solar wing, and after close negotiations with staff in charge of final assemblies of the capsule and solar wing, the solution of “air supporting table + extended metal plate” was determined to be used for the first time on a manned spacecraft.
The air supporting table, on which the solar wing is supported through an air supporting pad, weighs up to 15 tons. The supporting pad forms air film by compressing air and makes the whole solar wing floating. The solar wing can then move and dock on the air supporting table, and realize deployment with zero friction. Shu Bin said, “the use of air supporting table can avoid the interference of solar wing with the module while furling. To ensure a highly accurate flatness, we have adopted the manufacturing process that combines the natural granite platform with artificial granite frame.”
While implementing the extended metal plate, considering the operational risk and time consumption arouse from repeated assembly and disassembly, the team of energy management system invited personnel in charge of capsule final assembly and overall design to the site in Shanghai, and carried out in-depth discussions about details of solar wing stowing. In the end, the problem was successfully resolved by integral translation of the capsule and precision rotating platform and time consumption for solar wing stowing was shortened to 2 days from 7 days, and the process of launch site was optimized. As to the concern of adaptation due to various models of air connection in Shanghai, Beijing and Hainan Province, air supply by air cylinders has been adopted to resolve this problem, and it has largely reduced supporting demand. The energy management system has ideally settled the stowing problem of solar wing under the condition of complex spacecraft shape.
More efficient: solar cells of the maximum photovoltaic energy conversion efficiency are applied in the international space for the first time
On the solar wing of the trial version of new-generation spacecraft, there carried the efficient GaAs solar cells of 34% photovoltaic energy conversion efficiency developed by Shanghai Institute of Space Power-Sources in form of charging circuit.
What dose it mean of 34% photovoltaic energy conversion efficiency? Solar wing is the wing and power source for spacecraft to keep flying. The performance and reliability of the solar wing is directly related to the success of the mission of the spacecraft. At present, the solar cells used as the main power supply of the solar wing in China and abroad are mostly of 30% photovoltaic energy conversion efficiency, and the photovoltaic energy conversion efficiency of the solar cell circuit product with the maximum efficiency applied in spacecrafts in the world is 32%.
From 30% to 32%, and from 32% to 34%, there seems to be only a 2% improvement in conversion efficiency, however, the change is a “significant prance over the summit” technically. To achieve technical level of 34% photovoltaic energy conversion efficiency in mass production, and realize the application of the new solar cell circuit, researchers at Shanghai Institute of Space Power-Sources have striven to make a lot of technological breakthroughs, such as, adopting new semiconductor materials of wide/medium bandgap to cover sunlight of short wave and medium wave, further reducing the heat loss of current carriers and enhancing energy efficiency of solar spectrum, tackling the technical difficulties of growing mismatching materials and the deployment of wide spectrum and low reflectivity, and filled the gaps in related products in the international market and taken the leading position worldwide.
The industries of satellite, manned flight and deep space exploration are demanding in the energy capture technology of “efficiency, light weight, high voltage, and mass specific power”, for example, the space station requires larger scale of power supply, and the area of single wing solar cell would be increased to above 100 m2 from the 10 m2 at present, meanwhile, however, to ensure control of the spacecraft attitude, the area of solar array should be reduce as much as possible, thus enhancing the photovoltaic energy conversion efficiency of solar cells becomes an effective way to solve the conflict above” Zhong Danhua said, “In China’s lunar exploration program, the new-generation manned spacecraft, manned moon landing and ascent aircraft mission, the technology of efficient solar cells with mass specific power is the key technology and essential requirement. 34% photovoltaic energy conversion efficiency will effectively improve the power generation capacity of China’s spacecraft and deep spacecraft, and support the renewal of China’s aerospace power system.”
Optimization: with more cost savings and less process
Another highlight of the trial version of new-generation manned spacecraft compared to the previous models is that the process of cell test and launch has been optimized.
“The energy management system of the trial version of new-generation manned spacecraft has been equipped with 8 auxiliary power supplies, which are 320AH zinc-silver storage batteries. As a kind of disposable battery, the service life of zinc-silver battery is only 6 months, however, the test cycle of the whole spacecraft is 1-2 years. We simulate the corresponding features of zinc-silver batteries, and replace them with electronic power supply on ground to deploy relevant function tests. It costs tens thousands yuan to develop a set of battery, and for 15 sets, it means millions yuan cost savings”, said Tan Xiao, Deputy Director Designer of energy management system for the trial version of new-generation manned spacecraft.
As the maiden flight of manned spacecraft in Hainan Wenchang, the island climate of high temperature and high humidity has brought great challenge for nickel-cadmium battery. “The exact activation temperature range of nickel-cadmium battery is 18℃-20℃, and its storage temperature range is -2℃-2℃, which needs to be equipped with special low temperature storage cabinet, however, there are no such conditions in Hainan. Therefore, we changed the process and activated and sealed the batteries in Shanghai first, and transported them to Hainan then” Tang Xiao said, ”In the previous process, activation in the base required a lot of ground equipment, needed 15 approach facilities, 20 cables, 6 ground equipment boxes, and 1 container, meanwhile, 3 operating personnel should be assigned on site, and it took 14 continuous days for a activation cycle, during which non-stop duty cycle operation was needed and the personnel should work overnight shift. The new process eliminates the need of approach facility, avoid personnel allocation and shorten the process for launching.”
Souce：Shanghai Academy of Spaceflight Technology