December 7, 2019

Chinese space station testbed ends mission with controlled re-entry


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A prototype space lab module for China’s planned space station re-entered the atmosphere over the South Pacific Ocean Friday to end a nearly three-year mission that included a visit from Chinese astronauts and an in-orbit refueling demonstration.

The 34.1-foot-long (10.4-meter) Tiangong 2 module plunged into Earth’s atmosphere at 1306 GMT (9:06 a.m. EDT) Friday and burned up as intended. Debris from the spacecraft fell in a remote zone of the South Pacific Ocean between New Zealand and Chile.

Chinese officials guided the Tiangong 2 spacecraft for a targeted re-entry after the module’s predecessor, Tiangong 1, fell out of orbit in an uncontrolled manner last year, raising concerns about falling space junk.

According to China’s state-run Xinhua news agency, the guided re-entry of Tiangong 2 “demonstrates that China sticks firmly to its international duties and keeps its promise of peaceful and scientific use of space resources,” said Zhu Congpeng, chief designer of Tiangong 2 from the China Academy of Space Technology.

Tiangong 2 was not designed to survive re-entry, and video captured from a camera on-board the spacecraft showed a cloud of ionized gas building up around the module as it fell into the atmosphere. Then the communications signal cut off, as expected, before Tiangong 2 broke apart.

Unlike the situation with Tiangong 1, Chinese space officials elected to deorbit Tiangong 2 when it still had enough propellant to safely maneuver back into the atmosphere.

“Although Tiangong 2 had been in operation nearly one year longer than its designed lifespan, its platform and payloads functioned stably and soundly, and the propellant it carried was still sufficient to support its flight in orbit for another several years,” Zhu said, according to Xinhua. “It’s hard to say goodbye to Tiangong 2, but considering reliability- and safety-related factors, we have to drive it out of orbit now.”

“To let Tiangong 2 ‘retire’ by choice is to ensure the absolute safety of its departure,” Zhu said.

Two rocket firings by Tiangong 2’s propulsion system lowered the spacecraft from its operational orbit roughly 235 miles (380 kilometers) above Earth, beginning Thursday. After an initial maneuver Thursday to move into an elliptical orbit, Tiangong 2 fired its thrusters again Friday for a final deorbit burn, committing the module to re-entry, according to the China Manned Space Engineering Office.

Designed for a two-year lifetime, the bus-sized Tiangong 2 space lab launched Sept. 15, 2016, on top of a Long March 2F rocket from the Jiuquan space base in northwestern China.

The Shenzhou 11 spacecraft and its two-man crew docked with Tiangong 2 a month later for a four-week stay, the longest Chinese human space mission to date.

After Shenzhou 11’s departure, China launched a robotic refueling freighter in April 17 to dock with Tiangong 2 and carry out a series of tests to demonstrate capabilities for servicing China’s future space station.

The Tianzhou 1 refueling spacecraft docked with Tiangong 2 three times, testing maneuvers needed for fast-track rendezvous profiles that will allow future cargo and resupply freighters to dock with China’s planned space station as little as six hours after launch.

While attached to Tiangong 2, the Tianzhou 1 spacecraft pumped rocket fuel and oxidizer into the Tiangong 2 space lab, the first such in-space refueling activity in China’s human spaceflight program.

The Tiangong 2 spacecraft measured about 34.1 feet (10.4 meters) long, and its main body has a diameter of about 11 feet (3.35 meters). The space lab’s two solar array wings extend to a span of about 60 feet (18.4 meters) tip-to-tip.

Tiangong 2 hosted dozens of additional scientific and engineering experiments, including an ultra-precise cold atomic clock that could aid future space-based navigation systems, and a gamma-ray burst detector developed jointly by Chinese and European scientists.

The grounding of China’s heavy-lift Long March 5 rocket has raised doubts over the schedule for the launch of the first element of multi-module Chinese space station. China is building the space station’s core module for launch on a Long March 5 booster, but the rocket has not launched since suffering a failure in July 2017.

Several missions are ahead of the Chinese space station in the Long March 5 manifest, once the rocket resumes operations. They include the launch of a large Chinese communications satellite, the Chang’e 5 lunar sample return mission, and a test flight of the Long March 5B variant, which is configured for missions to haul space station modules into orbit.

A Chinese Mars lander is also supposed to take off on a Long March rocket in July 2020.

China says the human-tended orbiting complex should be completed by around 2022.

Chinese officials announced last month the selection of international science teams to provide at least six research instruments to fly on the Chinese space station. Another three science payloads received conditional acceptance to fly on the Chinese station.

The nine instrument teams selected to fly their experiments and sensors on the Chinese space station include membership from Belgium, China, France, Germany, India, Italy, Japan, Kenya, the Netherlands, Norway, Mexico, Poland, Peru, Russian Federation, Saudi Arabia, Spain and Switzerland.

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Follow Stephen Clark on Twitter: @StephenClark1.


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