China is getting ready to launch its first cargo spacecraft, Tianzhou-1, to its Tiangong-2 space station later this week. China’s Xinhua news services says the launch will take place between April 20 and 24. This is a test of robotic in-orbit refueling. No one is aboard the space station or the cargo spacecraft. [UPDATE: China has announced the launch will take place on April 20 at 7:41 pm local time (7:41 am Eastern Daylight Time.]



Tiangong-2 was launched last year and occupied by a two-man crew for 30 days. It has been empty since then. China’s first space station, Tiangong-1, was launched in 2011 and occupied by two three-person crews (two men and one woman each) in 2012 and 2013 for 13 days and 15 days respectively. The Tiangong space stations are quite small – 8.6 metric tons (MT). China is planning to build a three-module 60-MT space station by 2022. Tianzhou spacecraft would be used to deliver fuel and cargo to it.

Tianzhou-1, which is larger (13 MT) than Tiangong, will be launched from China’s new Wenchang Satellite Launch Center on Hainan Island using the new Long March 7 mid-sized rocket. The first Long March 7 was launched last year.



Tianzhou-1 space station cargo spacecraft atop its Long March 7 rocket being transferred from the assembly building to the launch pad at Wenchang Satellite Launch Center, Hainan Island, China, April 17, 2017. Photo credit: Xinhua



Tianzhou-1 will dock with Tiangong-2 three times to test in-orbit liquid propellant refueling. The Soviet Union demonstrated the first robotic refueling of a space station in 1978 when Progress 1 refueled Salyut 6. Russia still uses Progress spacecraft today to refuel the International Space Station’s (ISS’s) station-keeping engines as well as to take supplies to ISS.

Tianzhou-1 can carry 6.5 MT of cargo according to China Global Television News (CGTN). The current version of Russia’s Progress can deliver about 2.5 MT of cargo. Three other spacecraft resupply ISS — SpaceX’s Dragon, Orbital ATK’s Cygnus (one of which will be launched tomorrow), and the Japan Aerospace Exploration Agency’s (JAXA’s) HTV or Kounotori. HTV is the largest of those, capable of delivering approximately 6 MT of cargo.