China's Tiangong-2 space lab and Tianzhou-1 vehicle have completed a second refueling test, Chinese space officials said.

This second robotic refueling trial wrapped up Thursday (June 15) after about two days "and cemented technical results from the first refueling," according to China’s state-run Xinhua news agency.

Tianzhou-1, China's first cargo spacecraft, was lofted into Earth orbit on April 20 from the Wenchang spaceport in south China’s Hainan Province. The freighter's first auto-docking with Tiangong-2 took place on April 22, followed by the two spacecraft completing their first in-orbit refueling on April 27. [China's Tiangong-2 Space Lab in Pictures]

29-step program

During its two-month flight in space, Tianzhou-1 is scheduled to refuel the space lab three times, China's CCTV-Plus has reported.

Each test is scheduled to demonstrate a different aspect of China's approach to space refueling. The refueling procedure requires 29 steps to complete and lasts for several days each time.

In-orbit refueling has been deemed as a major need by Chinese space officials to further the nation's space-station plans. China aims to have a multi-module complex up and running in Earth orbit by the mid-2020s.

On Sept. 15, 2016, China launched its uncrewed Tiangong-2 space lab to Earth orbit. Learn all about the spacecraft, which China views as a key step toward building a bona fide space station, in our full infographic here

Leonard David is author of "Mars: Our Future on the Red Planet," published by National Geographic. The book is a companion to the National Geographic Channel series "Mars." A longtime writer for Space.com, David has been reporting on the space industry for more than five decades. Follow us @Spacedotcom, Facebook or Google+. This version of this story was posted on Space.com.