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The robotic Tianzhou 1 refueling freighter launched last week has successfully completed the first in-orbit propellant transfer with China’s Tiangong 2 space lab, a major accomplishment as the country’s engineers hope to finish assembly of a large space station by 2022, officials said Thursday.

The refueling demonstration validates key technologies China will need to assemble and maintain the nation’s planned 60-metric ton (130,000-pound) space station. The core component of the orbital complex, named Tianhe 1, could launch as soon as next year, followed by two more research modules by 2022.

Chinese officials did not reveal details about the refueling activity, such as the amount of propellant transferred and whether the demonstration included both fuel and oxidizer.

China’s state-run Xinhua news agency reported the the refueling test was completed at 1107 GMT (7:07 a.m. EDT; 7:07 p.m. Beijing time) Thursday.

“According to the report from the Beijing Aerospace Command and Control Center, Tiangong 2 and Tianzhou 1’s first in-orbit propellant refueling mission is completed successfully,” said Zhang Youxia, chief commander of China’s human space program. “Now, please allow me to declare the Tianzhou 1 mission is completed successfully.”

Xinhua said the achievement made China the third country, after Russia and the United States, to refuel a spacecraft in orbit. The European Space Agency’s ATV supply ship refueled the International Space Station, but the fuel transfer system was provided by Russia.

The in-orbit refueling procedure took about five days, beginning soon after the Tianzhou 1 freighter docked with Tiangong 2 on Saturday around 240 miles (385 kilometers) above Earth.

The Tianzhou 1 spacecraft, also packed with cargo bags to simulate a supply shipment to China’s future space station, blasted off April 20 on top of a Long March 7 rocket from the Wenchang launch base on Hainan Island, a province in the South China Sea.

Chinese officials said before Tianzhou 1’s launch that the spacecraft would link up with the Tiangong 1 research lab three times during its mission. Xinhua reported that another refueling test is scheduled for June.

Tianzhou 1 is expected to stay with Tiangong 2 for about three months, then depart for around two months of standalone flight before re-entering Earth’s atmosphere to end the mission.

Crews on China’s space station will need fresh equipment, experiments and other supplies during long-duration missions. The longest Chinese spaceflight to date was the Shenzhou 11 crew’s visit to the Tiangong 2 space lab last year, a mission that lasted approximately 32 days.

Future Tianzhou spacecraft will deliver goods to the Chinese station, similar to the way U.S., Russian and Japanese supply ships ferry equipment to the International Space Station.

“For example, the daily supplies of the astronauts, including food and clothing, extravehicular spacesuits, as well as drinking water with special tanks,” said Bai Mingsheng, chief designer of the Tianzhou 1 spacecraft at the China Aerospace Science and Technology Corp. “We will see if the Tianzhou 1 spacecraft meets the demand of transporting and resupplying various goods through this launch.”

Tianzhou means “heavenly vessel” in Chinese.

The simulated cargo aboard Tianzhou 1 represents the equipment a three-person crew would need for one month in space, officials said. The payloads include crew provisions, water tanks and oxygen and nitrogen vessels designed to replenish the space lab’s breathable atmosphere.

With a launch mass of nearly around 28,460 pounds (12,910 kilograms), Tianzhou 1 was the heaviest spacecraft ever launched by China, slightly bigger than the Tiangong 2 space lab itself.

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