“Space express” launched! Experts explain chang’e-5 orbiter in detail

At 4:30 on November 24, 2020, China successfully launched the chang’e-5 probe into the scheduled orbit with the Long March 5 carrier rocket at Wenchang launch site, and the launch mission was a complete success. Chang’e-5 is the end of the third phase of China’s lunar exploration project, which will realize China’s first unmanned lunar sampling return. Chang’e-5 consists of an orbiter, a lander, an ascent and a reentrant. Among them, the orbiter developed by the eighth Institute of China Aerospace Science and Technology Group Co., Ltd. will undertake the heavy tasks of Earth Moon transportation, lunar orbit rendezvous and docking, and sample container transfer. It is like a bold and cool “space express brother”, who sets out from the earth to the moon orbit 380000 kilometers away, takes a precious sample from the moon, and then delivers it back to earth. According to cha Xuelei, deputy chief designer of the chang’e-5 probe of the eighth Academy of China Aerospace Science and technology group, the work of the orbiter runs through the whole chang’e-5 exploration mission. After the launch, the first mission of this “space express” is transportation. As an autonomous vehicle, it is responsible for carrying lander, ascent and reentrant, completing Earth Moon transfer, midway correction and near moon braking. After entering the orbit around the moon, the combination of the orbiter and the lander lifter is separated, and the reentrant is left on the orbit to wait for “pick-up”. < / P > < p > the combination of lander and ascender arrives on the moon. After the lunar soil sample collection task is completed, the ascender takes off the sample from the lunar surface, rendezvous and docking with the orbiter waiting in the lunar orbit, and transfers the sample container to the reentrant. After separation from the docking module and the ascent, the orbiter will carry the reentrant into the lunar earth transfer orbit; it will be separated from the reentrant at a distance of 5000 km from the earth and will be sent back to the earth. < / P > < p > “in the whole mission of chang’e-5, the orbiter has five separation times and six combination states. It undertakes the key tasks of Earth Moon transportation, separation between spacecraft, rendezvous and docking, and sample transfer. It is one of the most complex space vehicles at present.” Cha Xuelei said that the orbiter, which is responsible for the heavy task, has “three more” characteristics in technology: < / P > < p > first, it has many flight stages. The orbiter is involved in eight of the 11 flight stages of the probe system, including launch, Earth Moon transfer, near moon braking, lunar orbit operation, lunar descent, lunar surface work, lunar rise, rendezvous and docking, lunar waiting, lunar earth transfer and reentry recovery. The other is that there are many states between devices. There are six kinds of combined states of orbiter in the flight process, which undertake the key tasks such as separation, rendezvous and docking and sample transfer. The interface between the orbiters is complex, and the mission process of the orbiter has to undergo multiple orbit changes and attitude adjustments. The orbital flight and attitude control are difficult, and the reliability requirements of aircraft, electrical and thermal interfaces are high. The third is that the separation times are more. The whole process involves five separations, including separation from the rocket, separation from the landing ascent assembly, separation from the support module, separation from the docking module riser assembly, and separation from the reentrant. There are many times of separation on orbit, and the separation environment is complex, so the system design is very difficult. < / P > < p > as a “space express brother” in the chang’e-5 “flying sampling” mission, the most important task of the orbiter is “pick-up”. In the lunar orbit 380000 km away from the earth, the orbiter and the ascent automatically rendezvous and docking, and transfer the samples in the ascent to the reentrant. This is the first automatic rendezvous and docking of a human spacecraft in lunar orbit. The docking and sample transfer mechanisms are developed by the eighth Institute of China Aerospace Science and technology group. According to Zhang Yuhua, deputy commander-in-chief of chang’e-5 probe of the eighth Academy of China Aerospace Science and technology group, the docking mode of the chang’e-5 orbiter and the lifter is quite different from that used in China’s manned space flight. Manned spaceflight adopts “heteromorphic peripheral docking mechanism”. After docking, the two spacecrafts form a channel about 80 cm, in which astronauts can walk. < p > < p > chang’e-5 adopts the “holding claw type docking mechanism”, which realizes the integration of docking and automatic transfer functions by adding a connecting rod pawl type transfer mechanism. These design concepts are the world’s first, docking accuracy can reach millimeter level. < / P > < p > “the so-called” holding claw “is like the action of holding a stick in our hand. If we exert force in two directions, we can firmly hold the stick in our hand.” Hu Zhenyu, deputy technical director of the chang’e-5 orbiter, explained that “the docking mechanism is composed of three sets of K-shaped holding claws. When the lifter approaches, as long as the three connecting rods on the connecting surface are aligned and the holding claws are tightened, the close connection of the two devices can be realized According to Liu Zhong, technical director of docking mechanism and sample transfer subsystem of 805 Research Institute of the eighth Research Institute, due to the time delay of lunar orbit relative to earth orbit, the time corridor is small, and the timeliness requirement is very high, so the docking and transfer tasks must be completed in one go. All steps should be completed in 21 seconds, 1 second capture, 10 seconds correction and 10 seconds locking. In order to ensure safety, the research team has made 35 fault plans, and all of them are controlled automatically from the start to the rendezvous and docking. < p > < p > in order to complete the extremely complex lunar unmanned sampling return mission, chang’e-5 is like a “transformer”, which needs to complete the deformation process of “separation combination re separation recombination” in space. < / P > < p > in view of the characteristics of the whole mission, such as multiple flight states, multiple interfaces between vehicles, multiple working modes, difficult technical research, ground verification, and new launch and launch site, the orbiter development team of the eighth Research Institute has made breakthroughs in a number of key technologies, making this “space express brother” strong and strong, light as a swallow, brave and super cool. < p > < p > in order to ensure the stable connection of the orbiter and the safe and reliable separation of the two devices during the separation process, the orbiter has five separation surfaces. The research team abandoned the traditional way of cabin connection, and innovatively used multi-point high-strength separation nut for connection. < / P > < p > in this connection mode, different numbers of separation nuts are arranged on each separation surface to meet the requirements of strength and stiffness of connection between compartments. At the same time, the “double acting” release nut contains two sets of unlocking mechanisms, and any set of action can ensure the reliable separation of each separation point on the separation surface. < / P > < p > the design of the orbiter is divided into sections, and each cabin has corresponding requirements for power distribution management, thermal control management and information management. The R & D team innovatively put forward the design idea of distributed integrated electronic stand-alone with regional management and the design idea of regionalization, standardization and modularization of electrical management of the whole device. Through the development of a series of standards and specifications, the integrated electronic system from the inside to the outside neat standard, flexible assembly, easy to expand, stable software, good signal transmission, ignition of initiating devices, control of the mechanism. < / P > < p > in order to control the “weight”, the orbiter must be “as light as a swallow” while requiring a strong carrying capacity. For this reason, the research team used seven innovative technologies for the first time, such as lightweight structure with large load-bearing complex configuration, innovative use of multiple separation complex configuration, first use of multi redundant path composite force transfer structure, and first use of large bearing composite bearing spherical crown technology. Only 46 kg load-bearing spherical crown, can carry 3 tons of tank, with the ultimate bearing capacity of 30 tons, which is comparable to “hanging a weight on the eggshell”. The lunar orbit docking and sample transfer technology is the most important technology for the success of chang’e-5 “flying space sampling return”. As early as January 2011, the 805 Institute of the eighth Institute of the people’s Republic of China began to carry out relevant technical research and engineering development. The research team has broken through the key technologies of light and small weak impact docking, automatic sample transfer with complex interface, and integration of docking and transfer, and has built four test systems, namely, the whole machine characteristic test bench, the performance test bench, the comprehensive test bench and the thermal vacuum test bench. < / P > < p > in the past 10 years, the R & D team of the eighth Research Institute has conducted 661 docking tests and 518 sample transfer tests. Through continuous testing and optimization, the automatic docking and sample transfer process are guaranteed to be safe and sound. Continue ReadingASMC, a lithography maker, was one of TSMC’s 14 top suppliers last year