The core module and control hub of Tiangong, China’s first permanent space station, is called Tianhe, or ‘Heavenly Harmony’.
Its launch on April 29 meant that Tiangong is a huge step closer to becoming fully operational next year. The only alternative is the US-led International Space Station, although it is due to retire in 2024, leaving Tiangong potentially as the only space station in orbit.
Despite Tianhe’s harmonic name, its launch created a ruckus of cosmic proportions. The issue was that as well as getting the Tianhe into orbit, China also sent a large part of the delivery rocket – a Long March 5B – into space with no apparent way of controlling its eventual return to Earth.
The 23-tonne, 10-storey vessel was left to orbit the Earth, coming lower with every pass, before breaking up and falling into the Indian Ocean near the Maldives on May 9.
The uncontrolled descent stirred America’s NASA to publish a statement criticising China’s space programme for a lack of transparency and accusing it of “failing to meet responsible standards” with regard to space debris.
Beijing hit back accusing the West of double standards. “When a piece of [Elon Musk’s] SpaceX rocket landed on a farm in Washington in March this year American media used romantic descriptions such as ‘lighting up the night sky like a meteor’. But when it comes to China, the tune is completely different,” a spokeswoman for the Chinese Foreign Ministry said.
Normally rockets sent into orbit are programmed to reactivate as they approach the earth’s atmosphere so they can enter at a preset angle or be guided away from populated areas. The goal is to have as much of the rocket as possible burn up on re-entry and have the remaining debris fall into the sea or uninhabited regions.
The three-tonne upper stage of the SpaceX Falcon 9 rocket that fell back to Earth on March 25 was, like its predecessors, programmed to do this. But it appears to have malfunctioned, meaning it returned in an uncontrolled manner.
The Long March 5B by contrast does not seem to have been designed with re-entry controls in place. Or if it had, then it has malfunctioned twice, the first time in May last year when the inaugural launch of the rocket model put an 18-tonne piece of ‘staging’ into orbit – only for it to come crashing back to Earth in an uncontrolled manner a week later.
China has not been clear whether the Long March 5B parts are supposed to return to Earth this in this way or whether they should have been guided to a safe area.
The assumption now amongst foreign experts is that China is choosing not to build guided re-entry capability into the design and is instead taking a calculated risk that the debris will burn up on re-entry and fall somewhere over an ocean.
An interview with a rocket designer from the Chinese Academy of Launch Vehicle Technology carried by Xinhua this week appeared to confirm this. “Achieving controlled re-entry of the debris is difficult unless you are willing to lose a large part of the rocket’s carrying capacity. We try to avoid damage by tracking and monitoring the rocket in the final stages,” he said.
Further compounding international concern around the rocket was the fact that Chinese authorities released no statement for nine days after the launch, only breaking their silence via the Foreign Ministry two days before the debris came down.
The Long March is thought to be the fourth largest piece of space debris to return to Earth, the largest being the 77-tonne US Skylab, which returned in a hair-raising semi-controlled descent in 1979 – showering wreckage over southwestern Australia.
China is planning two further Long March 5B launches in 2022 to send two experimental modules, named Wentian and Mengtian, to join Tianhe in orbit.
It remains to be seen if those launches live up to the names of their payloads: ‘Quest for the Heavens’ and ‘Dream of the Heavens’.
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