China is building up its space station in orbit and litter from the flying
construction site over our heads is set to fall all the way back to the
surface of our planet again this week.
For the third time in the past two years, China's space program has sent a
large module to orbit to expand its Tiangong space station using a Long
March 5B rocket, which appears to lack the hardware to make a controlled
reentry and steer itself toward a safe splashdown in a remote part of the
ocean.
Instead, the spent rocket booster weighing over 20 metric tons is expected
to largely burn up as it sizzles through the atmosphere. But it's likely
some of the larger components and other debris will survive all the way to
the surface. Currently, this atmospheric reentry is expected to happen
sometime during a 28-hour window that begins Friday evening, Pacific time,
and runs through most of Saturday, according to predictions from the
Aerospace Corporation, which tracks orbital reentries.
"The uncertainty of where the large debris will ultimately land presents a
level of risk to human safety and property damage that is well above
commonly accepted thresholds," the company
wrote in a statement.
The rocket was used to send Mengtian, the third and final section of
Tiangong, to orbit for installation on a launch that took place Monday. The
booster is roughly the size of a 10-story building.
Similar reentry risks were seen with the launch of the previous two Tiangong
space station modules as well, with a spent rocket landing in the Indian
Ocean on May 8, 2021, and another breaking up over Malaysia, Indonesia, and
the Philippines on July 30, 2022. Another Long March 5B mission also led to
debris falling on western Africa in 2020.
Over the next two days, we can expect that predicted reentry window duration
to shorten considerably as space watchers track the decay of the empty
rocket's orbit and get a better idea of when it will finally submit itself
to the pull of Earth's gravity.
When it does begin its short and fiery trip back to Earth's surface, there's
no real way of predicting where it will end up. The debris field left by a
rocket reentry with this much mass can leave bits and piece strewn over a
debris corridor stretching dozens or even hundreds of miles long.
The last time one of these spent boosters fell back to Earth, in late July,
it broke up over Malaysia and chunks of it were later found on the ground
both there and in Indonesia.
Falling space junk has damaged property, but there has never been a report
of human injuries or death. Earth's population distribution makes it most
likely any trash making it all the way from orbit to the surface ends up
either in the ocean or someplace remote (rural Australia seems popular). That said, this booster is completely out of control and could end up
depositing parts of itself anywhere along its flight path.
At the moment, the potential flight path for reentry covers a pretty wide
swath of Earth including most of the United States, China, India, Southern
Europe, South America, Africa and Australia. Basically, if your latitude is
higher than that of France or Portland, Oregon, you're probably in the
clear. Again, we'll know more about the flight path in the hours right
before predicted reentry.
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| The latest prediction for CZ-5B's reentry Photo credit from The Aerospace Corporation |