China’s space lab Tiangong-2, is coming back to Earth on July 19, if all goes as planned (link in Chinese).
Unlike Tiangong-1, which China lost contact with before it burned up somewhere over the South Pacific in April 2018, this one’s return is designed to be in a controlled manner.
Any debris from Tiangong-2 is expected to fall east of New Zealand, in a region authorities estimate to be within a longitude between 160° to 90° W and latitude between 30° to 45° S—thousands of kilometers from land.
The two labs, which shared the same “Heavenly Palace” name, formed the stepping stones for China’s own space station. Next year, China is expected to launch the core of its station, which it hopes will put the country on the same footing as the other major space powers. The US and Russia long have been working together on the International Space Station (ISS), which China has been shut out from by US law.
Inside Tiangong-2
Designed to last two years in orbit, Tiangong-2 lifted off in September 2016 from the Gobi desert space center in Jiuquan, four years after China launched Tiangong-1. Spacecraft often operate for a longer time than originally envisioned, as also was the case with Tiangong-1. NASA says the ISS is to be retired in 2024, but activities could be extended to 2028 or beyond.
Both Chinese labs were around one-tenth the length of the ISS, which at 357 ft is about as long as an American football field. Tiangong-2, more advanced than its predecessor, hosted China’s longest crewed mission. Two astronauts spent 30 days on board after traveling to the station on the Shenzhou-11 spacecraft in October 2016. (That’s still far from the Russian record: Valery Polyakov spent 438 days in the Mir space station in the 1990s.)
For the manned mission, Tiangong-2 was outfitted with a treadmill and fridge, state media Xinhua reported. To use the treadmill, astronauts hooked a rubber band over their shoulders to stay on the machine and jog in microgravity. They were the only crew ever to be on board the Tiangong-2 and they returned to earth in November 2016.
China launched its first cargo spacecraft Tiangzhou-1 to refuel the lab in April 2017. Tiangong-2 “enabled the exhaustive testing of automated refueling, which is essential for the big space station and this was entirely successful,” said Brian Harvey, author of China in Space: The Great Leap Forward.
Coming back in a controlled manner
Jonathan McDowell, an astrophysicist at Harvard University, said Tiangong-2 is orbiting along a relatively high orbit, at around 380 kilometers (240 miles), not much lower than the ISS at 410 kilometers (250 miles). Once its re-entry engines are fired, the lab will burn up over the ocean within 30 minutes. He noted that it’ll be hard to track it because “there will be no sign of impending re-entry until it is all over.”
Morris Jones, an Australian space analyst, said China can use the controlled re-entry to obtain crucial data. “They can monitor the rate of descent and how it breaks apart. This data is useful for understanding other re-entries,” Jones said in an email to Quartz.
Both labs helped pave the way for China’s space station, which it wants to get in place soon. A recent report from Spacenews, however, suggested that the Long March 5 launch vehicle (also known as CZ-5) isn’t ready. Deployment of the rocket, designed to transport the station’s core module, was delayed after a May launch failure.
“It seems that fixing the CZ-5 is taking much longer than expected, but they want to get it right,” Harvey said of Chinese space officials. “In the overall scheme of things, a delay of another year is frustrating, but of no long-term significance.”