[Reading Science] China's Space Debris 'Nuisance' to Worsen in the Future

Cause of Changzheng 5B Launch Vehicle, Likely to Be Launched More Frequently
Chinese Official: "Responding to Rapidly Growing Demand for Large-Scale Launches"
Estimated for 'Guowang' Space Internet Project Requiring 13,000 Small Satellites
At Current Rate, Global Alerts Expected Monthly
New Upper Stage and Technical Alternatives Available

Space debris presumed to be remnants of a Chinese space launch vehicle that crashed in India earlier this year.

[Asia Economy Reporter Kim Bong-su] The recent large-scale space debris alert originating from China that shocked the world is expected to occur more frequently. There are concerns that such alerts could sound globally about once a month in the future.

On the 14th, according to space news outlet SpaceNews, Liu Bing, Chief Designer at the China Launch Vehicle Technology Research Institute, recently revealed to Chinese media plans to use the Long March 5B launch vehicle for deploying multiple cluster satellites into low Earth orbit. Liu stated, "In the coming years, the Long March 5 series rockets will be used intensively to meet China's rapidly growing and large-scale launch vehicle demand."

Although Liu did not specify the exact purpose, attention is focused on China's space internet service construction project called 'Guowang Project,' which will use as many as 13,000 small satellites. Similar to how the US company SpaceX launches over 50 Starlink satellites at once on a Falcon 9 rocket, China may also use the Long March 5B launch vehicle to build Guowang. In this case, China is expected to launch the Long March 5B at least once a month, similar to SpaceX.

The problem is that the Long March 5B launch vehicle has been the source of three large-scale space debris reentry alerts worldwide over the past two years. Unlike other rockets, its first stage does not separate early but ascends to the target orbit to deploy its payload (satellites), then unpredictably reenters the atmosphere and falls back to Earth within about a week. Especially since it is over 30 meters long and weighs 23 tons, debris may survive atmospheric reentry and fall to the surface. Experts estimate that the probability of debris from the conventional Long March 5B causing casualties on the ground ranges from at least 1 in 230 to as high as 1 in 1,000, which is significantly higher than the internationally accepted risk threshold of 1 in 10,000. The rocket was launched three times last year in April, this year in July, and at the end of last month to deploy modules for China's independently developed Tiangong space station, which is why space debris reentry alerts sounded globally each time.

[Image source=Yonhap News]

Fortunately, debris has not yet fallen in densely populated areas, but serious damage is feared in the event of an accident. Especially if China uses the Long March 5B in the same manner as it did for the Tiangong space station to launch small satellites for Guowang, the worst-case scenario could see large-scale space debris fall alerts sounding worldwide once a month. In fact, on the 4th, Spanish aviation authorities temporarily banned flights after the likelihood increased that debris from a Long March 5B rocket would pass through their airspace during reentry.

There is an alternative. If China combines the recently developed upper stage Yuanzheng-2 with the Long March 5B first stage, it can separate the first stage early like other launch vehicles, thereby avoiding the creation of 'uncontrolled large space debris.' However, the size of Yuanzheng-2 remains a variable. If it is too large, there could still be risks of debris falling after atmospheric reentry. Chinese authorities have not yet disclosed the specifications of Yuanzheng-2. China may also consider artificially adjusting the trajectory so that the first stage falls within a designated area near the Wenchang Launch Center on Hainan Island, or reigniting the engine to control the timing and location of atmospheric reentry and debris fall.

Meanwhile, China plans to launch the Xuntian Space Telescope, which will be attached to the Tiangong space station, using the Long March 5B launch vehicle before the second half of next year, making another large-scale space debris alert inevitable.