November 28, 2022

Construction of Chinese space station enters final phase with module launch

A Long March 5B rocket hauls the Mengtian module into orbit for China’s Tiangong space station. Credit: China Manned Space Agency

China launched a heavy-lift Long March 5B rocket Monday with the Mengtian lab module, the final major element to complete the initial assembly and outfitting of the Chinese Tiangong space station. The lab module docked with the space station complex 13 hours later.

The Mengtian module rode into orbit in the nose cone of a Long March 5B rocket, China’s powerful launcher, which fired off its launching stand at the Wenchang space center on Hainan Island, China’s southernmost province. The 176-foot-tall (53.7-meter) rocket took off at 3:37:23 a.m. EDT (0737:23 GMT; 3:37:23 p.m. Beijing time) Monday as the orbital track of the Tiangong space station passed over the launch site.

The rocket headed east over the South China Sea, powered by 2.4 million pounds of thrust from the core stage’s twin YF-77 hydrogen-fueled engines and eight kerosene-fed YF-100 engines on four strap-on boosters.

The four boosters cut off and jettisoned about three minutes into the mission, and the core stage burned all its propellant about eight minutes after liftoff, before releasing the Mengtian lab module for the rest of the journey to the Tiangong space station.

The 58.7-foot-long (17.9-meter) Mengtian module partially extended solar arrays to begin generating electricity. The spacecraft, which weighed some 50,700 pounds (23 metric tons) fully fueled, performed a series of orbit adjustment maneuvers using on-board thrusters to line up for docking with the Tiangong space station.

The module linked up with the forward port of the space station’s Tianhe core module at 2:27 p.m. EDT (1827 GMT), about 13 hours after launch, according to the China Manned Space Agency.

The Tiangong space station orbits about 240 miles (380 kilometers) above Earth at an inclination of 41.5 degrees, a slightly lower altitude and inclination than the International Space Station.

Mengtian, which means “dreaming of the heavens,” will be used for space science and application experiments, Chinese officials said. It also has a cargo airlock to transfer equipment into and out of the space station, multiple slots for internal experiment racks, and attachment posts for unpressurized instruments outside the module.

Chinese astronauts Chen Dong, Liu Yang, and Cai Xuzhe living on the Tiangong complex monitored Mengtian’s arrival, then were expected to become the first crew members to float into the station’s new module.

After docking at the station, the Mengtian module will fully unfurl its solar panels to a span of about 180 feet (55 meters) tip-to-tip. A robotic arm will later relocate new laboratory to a different position on the port side of the Tianhe core module, giving the Tiangong space station its distinctive “T shape” in orbit.

Artist’s illustration of the Chinese Tiangong space station in its current configuration, with the newly arrived Mengtian module on the left. Credit: China Manned Space Agency

Mengtian is the last of three large pressurized modules needed to complete the initial construction of the Tiangong station. The Tianhe core module launched on a Long March 5B rocket in April 2021, and the Wentian laboratory section launched on a Long March 5B in July.

Like the newly arrived Mengtian module, Wentian first docked with the space station’s forward port in July, then was relocated to a side position.

The Chinese astronauts on the space station completed two spacewalks in September to install equipment and perform tests outside the complex. The crew that arrived in June on China’s Shenzhou 14 spacecraft will be replaced as soon as late this month by three new astronauts set for launch on the Shenzhou 15 mission.

The Shenzhou 14 crew members will undock and return to Earth in December to complete a six-month expedition.

Before the crew rotation, China plans to launch an unpiloted Tianzhou resupply ship to dock with the Tiangong station. That launch is currently scheduled for Nov. 12.

As expected, the launch of the Mengtian lab module Monday left the Long March 5B rocket’s massive core stage in orbit. It is circling Earth at a low altitude, and is expected to fall back into the atmosphere as soon as this weekend. Most of the rocket will burn up in the atmosphere, but debris from the uncontrolled re-entry could fall on land or in the sea between 41.5 degrees north and south latitude.

The launch of the Mengtian module was the ninth flight of a Chinese Long March 5 rocket, and the fourth in the Long March 5B configuration, which flies without an upper stage. The design means the large core stage of the rocket reaches orbital velocity before deploying its payload.

The core stages on the previous Long March 5B missions in 2020, 2021, and in July re-entered the atmosphere within days of launch. Suspected fragments from those rockets was discovered in the Ivory Coast, Malaysia, and Indonesia, but no injuries were reported from the debris falls.

The Long March 5B’s core stage measures about 100 feet (30 meters) long and has an empty mass of about 23.8 tons (21.6 metric tons), making it one of the largest and most massive human-made objects to ever re-enter the atmosphere in an uncontrolled manner.

A similar uncontrolled re-entry is expected for the Long March 5B core stage used on Monday’s mission.

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Follow Stephen Clark on Twitter: @StephenClark1.

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