Tiangong-2, the second target aircraft launched for China's manned space program, is China's first manned space science experimental space laboratory with supplementary function[1]。
Tiangong-2 was launched at Jiuquan Satellite Launch Center on September 15, 2016[2]；Terminate data service on July 16, 2019[3]；On July 19, 2019, it was controlled to depart from orbit and reenter the atmosphere, falling into the planned safe sea area in the South Pacific[4]。
Tiangong-2 is one of the main aircrafts in the phase of the space laboratory missionShenzhou 11、Tianzhou-1It is the first real space laboratory in China, undertaking the important mission of verifying the technology related to the space station[1]。
On July 7, 2016, Tiangong No. 2 was shipped from Beijing[5]。
On July 9, 2016, Tiangong-2 completed the research and development work before leaving the factory. It was safely transported by railway to the manned space launch site of Jiuquan Satellite Launch Center to carry out the final assembly and testing work in the launch site area.
On August 6, 2016, the Long March II F T2 carrier rocket that launched Tiangong II arrived at the Dongfengchang area[6]。
On September 9, 2016, Tiangong II Long March II F T2 carrier rocket was vertically transferred to the launch area[6]。
On September 14, 2016, Tiangong-2 rocket launch completed the propellant filling of Long March 2 FT2 rocket[7]。
On September 15, 2016, Tiangong-2 was launched from Jiuquan Satellite Launch Center[2]。
On September 16, 2016, Tiangong 2 carried out two orbital controls and entered the on orbit test track[8]。
Shenxi docking
On October 19, 2016, Tiangong 2 and Shenzhou 11 completed automatic rendezvous and docking, forming a combination, and Shenzhou 11 astronauts settled in[9]。
On October 23, 2016, Tiangong-2 released accompanying satellites[10]。
On November 17, 2016, Tiangong 2 and Shenzhou 11 were separated and the rapid orbit change control verification test was completed[9]。
Sky boat docking
On April 22, 2017, Tiangong 2 and Tianzhou 1 completed the docking task, forming a combination[11]。
On April 27, 2017, Tiangong-2 and Tianzhou-1 completed the first in orbit propellant supplement test[11]。
On June 19, 2017, Tiangong II and Tianzhou I completed the round flight and the second rendezvous and docking test.
On June 21, 2017, Tiangong 2 and Tianzhou 1 were separated.
On September 12, 2017, Tianzhou-1 and Tiangong-2 completed the autonomous rapid rendezvous and docking test task.
Complete the mission
On July 16, 2019, Tiangong No.2 terminated data service[3]。
On July 19, 2019, Tiangong II was controlled to depart from orbit and reenter the atmosphere, and a small amount of debris fell into the planned safe waters of the South Pacific[4]。
flying commission
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Flight procedures
Shenzhou 11 docking
1. After its launch, Tiangong II entered the initial orbit of 200 km perigee and 350 km apogee.
2. The track change enters the running track with a height of about 380km.
3. After the docking of Tiangong II and Shenzhou XI, the total flight time of Tiangong II is 33 days, including 30 days of stay in Tiantian II and 3 days of independent flight.
4. Detached from Shenzhou 11, Tiangong 2 returned to its long-term orbit, switched to an independent operation mode, continued to carry out space science experiments and applied technology experiments, and waited to participate in the Tianzhou 1 mission[12]。
Docking of Tianzhou-1
1. It will rendezvous and dock with Tianzhou-1 in two days to form a combination, carry out two months of on orbit flight and complete various tasks.
2. Tianzhou-1 evacuated from Tiangong-2, docked with it on the other side, and completed the flying around experiment.
3. The combination is separated again and switched to independent operation mode[13-14]。
Independent operation
1. Tiangong II was controlled to depart from orbit and reenter the atmosphere, falling into the planned safe waters in the South Pacific[13-14]。
Main tasks
The main tasks of Tiangong 2 include two aspects:
1. Carry out large-scale space science experiments, space application experiments, and aerospace medical experiments;
2. Assessment and verification of key technologies for the construction and operation of space stations, such as astronauts' medium-term stay, propellant replenishment and on orbit maintenance[15]。
Mission purpose
1. Accept the visit of Shenzhou 11, complete the mid-term stay of astronauts, and assess the life, health, work security and other related technologies of the crew for long-term flight;
2. Accept the interview of Tianzhou-1 to examine and verify the on orbit supplement technology of propellant;
3. Carry out space medicine, space science experiments and space application technology, as well as on orbit maintenance and space station technology verification and other tests[16]。
technical conditions
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Cabin composition
Tiangong No. 2 adopts the configuration of experimental module and resource module, with a total length of 10.4 meters, a maximum diameter of 3.35 meters, a solar wing span of about 18.4 meters, a weight of 8.6 tons, and a design in orbit life of 2 years.
In order to meet the need of propellant supplement verification test, Tiangong-2 carried out adaptive transformation on the propulsion subsystem based on the backup products of Tiangong-1 target aircraft;In order to meet the needs of medium-term stay, we have significantly improved the livable environment for carrying people, and have the ability to support two astronauts to work and live in orbit for 30 days[12]。
Tiangong II was launched by Long March II FT2 carrier rocket;The rocket is a two-stage carrier rocket specially used for manned spaceflight, with a total length of 52.03 meters, a take-off weight of 489.1 tons and a delivery capacity of 8.6 tons[12]。
Docking target
Shenzhou 11
The technical status of Shenzhou 11 is basically the same as that of Shenzhou 10 spaceship. According to the task and product development needs, some technical status has been changed. It stops at Tiangong 2 to perform a 30 day combined flight mission and has the ability to fly independently for 5 days.
The technical status of Long March II F T2 is basically the same as that of the previous T1 rocket, Y11 rocket and the previous Y10 rocket. In order to further improve safety and reliability, some technical status changes have been made;The Long March 2F carrier rocket is a bundled two-stage liquid carrier rocket, with a core stage diameter of 3.35 meters and four boosters bundled. The diameter of the boosters is 2.25 meters[17]。
Tianzhou-1
Tianzhou-1 is a fully sealed cargo spaceship, which adopts a two compartment configuration of cargo compartment and propulsion compartment. Its design life in orbit is one year. The spaceship is 10.6 meters in length, 3.35 meters in diameter at the maximum, and weighs 13.5 tons under the maximum loading state. It is composed of cargo compartment and propulsion compartment, with a carrying capacity of 6 tons[18]。
Flight carriage
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Tiangong 2 carries 14 application loads weighing about 600kg, as well as aerospace medical experimental equipment and on orbit maintenance test equipment, including the following items:
1. The space cold atomic clock is the first cold atomic clock in orbit in the world. According to the test results in orbit, the daily stability of the cold atomic clock is calculated to reach 7.2E-16.
2. The Polarization Detector for Gamma Ray Bursts (POLAR) jointly developed by China and the EU is the first special polarization detector for cosmic gamma ray bursts with wide field of view and high efficiency in the world.
3. Three award-winning experimental projects in the Space Science and Technology Design Competition for Hong Kong Middle School Students, including space sericulture, double pendulum experiment and water film reaction[19]。
Tiangong No.2
technological achievements
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technological innovation
1. A number of bold innovations have been carried out in the leakage rate, structural form and structural weight of the sealed cabin, and a structural scheme of "integral bulkhead" sealed cabin has been proposed, which has reduced the structural weight by more than 20%.
2. A thin-walled airship structure with a diameter of more than 3 meters has been developed to meet the requirements of large space and light and solid. At the same time, strict noise control indicators for living quarters and instrument areas have been formulated to control the noise within the minimum indicator range to the maximum extent.
3. In view of the many changes in the objectives of the space laboratory stage, the adaptability of the thermal control system has been enhanced to achieve accurate temperature control of the compressor temperature interface and the temperature of the sealed cabin;The intelligent thermal control core control equipment realizes the self diagnosis, isolation and disposal of the thermal control equipment's on track fault, and realizes the high reliability of the "air conditioning system"[20]。
Space support
1. It has loaded 14 space application payloads in the fields of space science research and space exploration, earth observation, earth science research and application of new technology experiments, as well as space medical experiment equipment, and will carry out a number of space science experiment activities;
2. The pipeline of the propulsion subsystem shall be modified adaptively, and the compressor and other equipment shall be added to complete the technical verification of propellant replenishment in cooperation with the cargo spaceship;
3. The manned livable environment has been optimized, the dining and sleeping environment has been improved, and the exercise equipment and entertainment facilities have been added. These changes can make the 30 day life of astronauts in the Tiangong more comfortable, convenient, and colorful;
4. The liquid circuit verification system consisting of mechanical, electrical, hydraulic and other components, as well as the manipulator operation test terminal have been built to carry out on orbit maintenance tests, which will accumulate experience for the subsequent on orbit maintenance design of the space station[12]。
Scientific research achievements
Quantum key distribution
The quantum key distribution test space terminal carried by Tiangong 2 cooperates with the quantum key distribution ground terminal through the high-precision automatic tracking and pointing (ATP) system to establish a quantum channel between the ground station and the target aircraft, and on this basis, the space ground quantum sub key distribution test was carried out.
This experiment took the lead in breaking through the key technologies related to quantum key distribution in China, and was verified in orbit.Successfully realized two-way high-precision tracking and pointing, quantum key distribution and laser communication[21]。
The scientific research team of Academician Pan Jianwei of the University of Science and Technology of China and the team of Academician Wang Jianyu, Dean of the Hangzhou Institute of Advanced Research of the University of Chinese Academy of Sciences, realized the experimental demonstration of the space ground quantum secure communication network through the "Tiangong II" and the compact quantum key distribution (QKD) terminals on four satellite ground stations.Relevant papers will be published in the international academic journal Optics in August 2022.[24]
Gamma burst polarization detector
Tiangong-2 carried the world's first wide field of view and high-efficiency special cosmic gamma ray burst (GRB) polarization detection instrument, which detected 55 GRBs in total, observed the pulse signal of the crab shaped lucky pulsar, and used the pulsar signal experiment for orbit determination for the first time in China, with orbit determination accuracy of about 10km, and detected several solar X-ray bursts[21]。
Thermocapillary convection experiment
On Tiangong-2, China carried out the thermocapillary convection experiment under the condition of space microgravity for the first time, studied the instability mechanism of thermocapillary convection under the environment of space microgravity, expanded the cognitive field of fluid mechanics, and achieved research results of international advanced level.
Breakthrough and mastered the key technologies of space experiments such as liquid bridge construction, liquid level maintenance and instability reconstruction in microgravity environment, further improving the space experiment capability and technical level of China's microgravity fluid science[21]。
Comprehensive Material Experiment
Most of the samples in the comprehensive material experiment carried out by Tiangong No.2 are the first in the world, such as new nano composite optical materials, high-performance thermoelectric conversion materials, multi-component multiphase alloys, etc. The main results of this experiment are:
1. High quality material crystals were grown, new material preparation processes were verified, and many new discoveries in material science experiments were obtained.
2. In terms of important functional crystals and other materials, the properties of samples prepared in space have been significantly improved or the microstructure has been improved.
3. Based on the data of space measurement, experiment and ground experiment, the thermal environment simulation calculation model of the first space material experimental furnace in China was established, and the basic law of the influence of gas pressure in the furnace on the maximum temperature of the furnace under space microgravity and ground gravity environment was obtained, which significantly improved the ability of space material scientific experiments in China[21]。
Arabidopsis and rice
Arabidopsis and rice were transported from Shenzhou 11 to Tiangong 2, and cultivation experiments were carried out.
In this experiment, artificial light, efficient water circulation and tracing were used, and the first "seed to seed" full cycle cultivation experiment of higher plants in China was completed in 6 months.
In this experiment, China found for the first time that the flowering of Arabidopsis was significantly delayed under the condition of long days in space;It was found for the first time that the plant life span under microgravity conditions was significantly longer than that of the ground control group;It is the first time to find that space microgravity has a significant effect on rice water spitting and its tropism growth.At the same time, for the first time in the world, the plant flowering gene promoter was successfully used to drive the expression of green fluorescent protein;It was found for the first time that the space microgravity environment significantly promoted the development of leaf vein network.
The effective use of space limited resources to maximize plant production provides important evidence and guarantees human long-term exploration of space[21]。
Space Earth Science and Applications
With the help of multiple remote sensing equipment, Tiangong 2 has achieved fruitful scientific achievements and significant application benefits, mainly including:
1. Multi angle wide band imager is a new type of integrated remote sensor with broad band spectrum and multi angle polarization imaging. It has realized the verification of 12 new systems of multi angle optical polarization remote sensing technology for the first time in China, and has opened up a new way to obtain important land, ocean and atmosphere information.
2. The 3D imaging microwave altimeter is the first wide swath 3D radar imaging altimeter used for ocean observation in the world. It adopts the innovative technology of short baseline, small angle interference, new height tracking and aperture synthesis.The development direction of the new generation radar altimeter plays an important role in improving China's marine environment monitoring, forecasting and forecasting capabilities.
2. The multi band ultraviolet edge imager is the first load with the ability of ultraviolet edge observation in China. It is the first time in the world to use a large field of view to simultaneously detect the ultraviolet annular and forward edge radiation characteristics of the global mesosphere.It has obtained the global atmospheric density, ozone and aerosol vertical structure and three-dimensional distribution, and has extensive application value in the fields of atmospheric trace gas monitoring, atmospheric and environmental forecasting, space weather, etc[22]。
Technical verification
Tiangong 2 completed a number of technical verifications during the mission, mainly including:
1. Release the companion satellite on the spacecraft.Accompanying star release, stay and accompanying flight tests were carried out, and clear images of the combination were obtained. At the same time, new micro satellite technology tests and verification were also carried out.
2. By carrying out the space fine manipulation manipulator test of human-machine cooperation, China has realized the human-machine cooperation on orbit maintenance task for the first time, established a human-machine cooperation on orbit maintenance system integrating information management, manual control, teleoperation and autonomous control, formed a typical human-machine cooperation system, and laid a technical foundation for the development of future space station humanoid robots.
3. It also cooperated with the Tianzhou-1 cargo spaceship to realize the on orbit propellant supplement task of Chinese spacecraft, comprehensively broke through and mastered relevant technologies, and fully verified the propellant supplement in the subsequent space station stage[22]。
Task significance
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The launch of Tiangong-2 is a key battle to fully complete the tasks of the space laboratory phase. It will lay a solid foundation for the construction and operation of China's subsequent space stations and accumulate valuable experience. It is of great significance for promoting the sustainable development of China's manned space industry[16]。(Comment on the official website of China Manned Space)
Tiangong-2 realized orbit determination by using the pulse signals of the Crab Nebula pulsar observed for the first time in China, which promoted the development of pulsar observation and navigation technologyExhibition.[23]
