On Friday, July 19, the Chinese space laboratory Tiangong-2 ("Heavenly Palace") entered the Earth's atmosphere under controlled conditions and burned over the South Pacific Ocean. As a result, all of Tiangong-2's tasks were completed, which was China's second attempt to test its ability to conduct research and conduct human operations in low Earth orbit.
According to the China Apparel Space Agency, Tiangong-2 entered the atmosphere at 9:06 pm Beijing time (6:06 am PDT; 09:06 am EDT). Some debris fell into a "safe and predetermined sea area in the South Pacific," but most space laboratories burned during the descent. In total, the station spent more than 1,000 days in orbit, significantly exceeding the proposed 2-year life span, and conducted a terrestrial orbit 16,209 times.
Tiangong-2 was launched in orbit on September 15, 2016 and has achieved impressive feats ever since. These included four successive moorings with the Shenzhou-11 spacecraft and the Tianzhou-1 cargo ship. During its many Earth orbits, Tiangong-2 supported teams of two astronauts, who would live and work in the station for 30 days.
The station has also enabled several key technological advances and has conducted extensive testing during its use. These achievements and those of its predecessor – Tiangong-1 – will lay the groundwork for the development, construction, deployment and operations aboard China's third and final orbital laboratory, the Large Modular Space Station (LMSS).
Astronaut Jing Haipeng, who celebrated his 50th birthday on October 24, 2016 in Tiangong-2:
"As the first entry into Tiangong-2, I am happy that the space lab has completed its tasks, although I miss it too because it was our home in space. My memory of the 30 days spent on Tiangong-2 with Chen Dong is still fresh. We have conducted many scientific experiments such as silkworm rearing and plant growing in space. China is stepping up efforts to prepare for the construction of the space station. We are confident that a space station belonging to the Chinese people will arrive soon. "
Illustration of the artist representing the Chinese space station Tiangong-1 of 8 tons, which should land on Earth at the end of 2017. Photo: CMSE
"The 30 days on Tiangong-2 have been the happiest and most unforgettable experience of my life, and the most precious time to cherish," added astronaut Chen Dong. "Tiangong-2 was the ideal place to realize my dream of space. The Chinese space station, a more powerful home, more advanced and more comfortable for astronauts, awaits us. "
Unfortunately, it was time for the second "Heavenly Palace" to be brought back to Earth before ceasing operations and becoming an abandoned space station. Zhu Zongpeng of the Chinese Academy of Space Technology was the chief designer of Tiangong-2. As he explained in a recent interview with Xinhua:
"It's hard to say goodbye to Tiangong-2, but given the reliability and safety factors, we need to get it out of the orbit. To let Tiangong-2 "withdraw" by choice is to guarantee the absolute security of his departure,
This decision was probably motivated by the re-entry of the Chinese space station Tiangong-1 in April 2018, which took place two years after the end of its operations. In comparison, this event had been somewhat uncontrolled. At first, the authorities were worried because it was not entirely clear if the Chinese still controlled the station.
The screen at the Beijing Aerospace Control Center on October 19, 2016, showing the two Chinese astronauts Jing Haipeng and Chen Dong entering the Tiangong-2 space laboratory. Credit: Xinhua / Ju Zhenhua
As the descent approached, the date of re-entry of the station, its date of fall and the number of surviving debris, raised new concerns. Nevertheless, Tiangong-1 and his successor have now been safely brought back to Earth and the lessons learned will be useful when the LMSS is operational.
The first module (the main cabin) is expected to launch in orbit next year, while the other two (Wentian and Mengtian labs) are expected to launch in 2021 and 2022, respectively. In addition to three docking ports, an EVA hatch and multiple solar panels, China hopes to assemble the entire space station by 2022.
Given that the International Space Station (ISS) is due to retire in 2024, China will be the only country to have a space station in orbit by that date. However, the LMSS system will be much smaller, measuring roughly the same size as the Mir space station, now in Russia's retirement. It will also represent about one-fifth of the ISS mass, which weighs well 400 metric tons (441 US tons).
All this serves to highlight the achievements of the Chinese space program, which follows a "three-step strategy" of development for 20 years. During this period, China sent 11 crewed spacecraft, 2 space laboratories and 14 astronauts into space and brought them home safely.
In the years and decades to come, China will send many other robotic missions into space and even hopes to conduct crewed missions on the Moon. It is also hoped that China will join space agencies such as NASA, Roscosmos, ESA, ISRO and projects such as the International Moon Village and other major space projects.
Further reading: phys.org, Xinhua, CMSA