30 BEIJING REVIEW AUGUST 1, 2019 http://www.bjreview.comA
fter blazing through the atmosphere, the
debris of the retired Tiangong-2 space
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on the evening of July 19, staging a glorious
homecoming.
The space lab, launched on September
15, 2016, had hurtled in orbit for more
than 1,000 days before commencing its
controlled deorbiting, which is a crucial
step since a spacecraft out of control may
pose a danger to other spacecraft in orbit
and to humans on the ground, said Zhu
Congpeng, chief designer of the space lab.
“To let Tiangong-2 retire by choice is to
ensure the absolute safety of its termina-
tion,” Zhu told the media.
This is the second time that China
has completed controlled deorbiting of a
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for Tianzhou-1, a space shuttle that ferried
supplies and fuels to Tiangong-2.Preventing hazards
Before its deorbiting, Tiangong-2 and its re-
maining payloads still functioned normally
and the propellant it carried was still suf-
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years, said Zhu.
But it had completed its mission, and
as time went by, it would have become
less reliable, and once it became defunct,
it would be out of control and gradually
fall into Earth’s atmosphere. At that point,
some materials with high melting points
may not combust completely, and the
resulting debris may injure people on the
ground, he explained.
It also took a lot of resources to keep
monitoring and testing the spacecraft;
now. After the deorbiting, these resources
can be released and invested in other mis-
sions, he said.
To guarantee a safe re-entry into the
atmosphere, a flight control team from
the China Academy of Space Technology
carried out a number of simulations and
drafted a detailed flight control plan, ac-
cording to Zhu. During the deorbit, they
adjusted the spacecraft’s speed and angle
so that its debris eventually fell into an un-
inhabited area.
The deorbiting prevented the space-
craft from becoming a hazard in space,the lab, which were captured by video cam-
eras and broadcasted online.
While in space, the duo raised six
silkworms in a transparent cylindrical
container, where the creatures grew and
spun cocoons. They also cultivated let-
tuce, thinning the seedlings and injecting
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was harvested and brought back to Earth
for further study. In addition, they tested a
brain-computer interface, an experiment
allowing astronauts to operate computers
with their minds.
Tiangong-2 was also a platform where
a number of other cutting-edge science
experiments were conducted including
Earth-space quantum key distribution, a
cold atomic clock, and gamma-ray burst
(GRB) observation.
Quantum key distribution is a secure
communication method using quantum
science to encrypt and decrypt messages.
A cold atomic clock is said to be the
most accurate timekeeper in the universe.
While a mechanical watch loses almost oneZhu said, noting that currently, Earth is
surrounded by more than 20,000 pieces of
space debris with diameters larger than 10
cm, and such debris can destroy any space-
craft it collides with.
It will take a decade for the debris in low
Earth orbit 400 km from Earth to descend
naturally into the atmosphere and burn up,
and it will take those in higher orbits even
longer, Zhu said.Conducting experiments
While it was in space, the lab served as
a platform for conducting more than 60
space science experiments and techno-
logical tests, according to Xinhua News
Agency.
In 2016, it accommodated two Chinese
astronauts for a month, marking the lon-
gest stay in space by Chinese astronauts.
Jing Haipeng and Chen Dong arrived at the
space lab in October of that year on board
Shenzhou-11 during China’s sixth manned
space mission. They lived and conducted
scientific and technical experiments fromChina’s space lab has been safely deorbited By Wang Hairong
A Safe Retirement
XIN
HU
AAn image simulating the docking of space shuttle Shenzhou-11 with space lab Tiangong-2 on October 19, 2016NATION