In this long exposure photo, a Long March 7 rocket climbs into the sky over the Wenchang spaceport on Hainan Island with the Tianzhou 2 cargo ship. Credit: Xinhua
China’s robotic Tianzhou 2 cargo ship launched Saturday on top of a Long March 7 rocket and docked with the core module of the country’s space station eight hours later, delivering fuel, crew supplies, extravehicular spacesuits, and other gear in preparation for the arrival of three astronauts in June.
The resupply mission is the second of a series of 11 launches planned by China through 2022 to assemble and outfit the space station. The Tianhe core module on a heavy-lift Long March 5B rocket to begin construction of the Chinese orbital complex.
The automated cargo freighter lifted off at 8:55 a.m. EDT (1255 GMT; 8:55 p.m. Beijing time) Saturday from the Wenchang spaceport on Hainan Island, China’s southernmost province. A 174-foot-tall (53-meter) Long March 7 rocket carried the 14.9-ton (13.5-metric tons) Tianzhou 2 spacecraft into orbit.
Chinese officials timed the launch for the moment the Earth’s rotation brought the Wenchang launch base under the orbital plane of the Tianhe space station module, allowing the Tianzhou 2 spacecraft to pursue the space lab on a fast approach that took just eight hours.
The mission was originally supposed to launch May 19, but Chinese officials scrubbed the launch attempt due to a technical issue.
The Long March 7 rocket’s six kerosene-fueled engines — two on the core stage surrounded by four strap-on boosters — generated 1.6 million pounds of thrust to power the launcher off the pad.
The launch vehicle steered toward the southeast and soared into space over the South China Sea. The Tianzhou 2 spacecraft separated from the Long March 7’s second stage about 10 minutes after liftoff, then unfurled solar panels to produce its own electricity.
A Long March 7 rocket takes off Saturday with the Tianzhou 2 supply ship. Credit: Xinhua
The supply ship completed a sequence of thruster firings to fine-tune its approach to the Tianhe core module, and lined up for an autonomous docking at 5:01 p.m. EDT (2101 GMT) Saturday.
Chinese state media reported the cargo ship used a microwave water and other instruments for its precise approach to the Tianhe module. Tianzhou 2 also used data from China’s Beidou navigation satellites.
The connection of the 34.8-foot-long (10.6-meter) Tianzhou 2 cargo craft with the 54.4-foot-long (16.6-meter) Tianhe module created a complex stretching more than 89 feet (27.2 meters) long. The Tianhe module is orbiting Earth at an altitude of approximately 230 miles (370 kilometers) at an inclination of 41.5 degrees to the equator.
The Tianzhou 2 spacecraft is China’s second Tianzhou-class supply ship to launch. The first, Tianzhou 1, launched in 2017 and docked with China’s Tiangong 2 space lab, a precursor to the larger 73-ton (66-metric ton) space station China constructing now.
Tianzhou means “heavenly vessel” in Chinese.
Tianzhou 2 delivered 14,638 pounds (6,640 kilograms) of propellant and dry goods to the Tianhe core module, according to the China Manned Space Agency. The payload included about 10,339 pounds (4,690 kilograms) of cargo inside Tianzhou 2’s pressurized compartment, and 4,299 pounds (1,950 kilograms) of orbital maneuvering propellant to be pumped into the Tianhe module’s tanks.
The Tianzhou spacecraft is similar in purpose to cargo freighters that fly to the International Space Station, such as the Russian Progress supply ship and the commercial Cygnus and Dragon carriers built by Northrop Grumman and SpaceX.
In design and capability, the Tianzhou is most like Russia’s Progress and Europe’s now-retired Automated Transfer Vehicle, which carried dry goods, water and propellant to the orbiting outpost. The U.S. commercial supply ships and Japan’s HTV logistics vessel cannot refuel the space station.
The docking of the Tianzhou 2 cargo freighter sets the stage for the launch of a three-person crew to the Tianhe module in June.
“We will transport support materials, necessary space parts and equipment first, and then our crew,” said Hao Chun, director of the China Manned Space Agency, according to a report published by the state-run Xinhua news agency.
The Tianzhou 2 cargo ship during prelaunch preparations. Credit: CASC
The three astronauts training to launch on China’s Shenzhou 12 mission next month plan to live and work aboard the Tianhe module for three months, the longest human spaceflight in the history of the Chinese space program.
The equipment delivered by the Tianzhou 2 cargo spacecraft included two spacesuits to be worn by astronauts venturing outside the Tianhe module on spacewalks. Tianzhou 2 also carried space parts of the module’s life support system, and food for the three astronauts.
The Shenzhou 12 astronauts will unpack the Tianzhou 2 cargo ship after they arrive next month.
Tianzhou 2 docked with the rear port on the Tianhe module, and Shenzhou 2 will link up with the lab’s forward port.
Once the Shenzhou 12 astronauts return to Earth in September, Tianzhou 2 will detach and fly to the forward port, where it will transfer propellant into the Tianhe module.
The robotic arm on the Tianhe module will also grapple the Tianzhou 2 spacecraft and move it to a connecting port on the side of the space lab, testing the manipulator system before the arrival of two more permanent laboratory modules next year.
The Tianzhou cargo ship is designed to operate in low Earth orbit for up to a year.
After the departure of the Tianzhou 2 and Shenzhou 12 spacecraft, China plans to launch the Tianzhou 3 and Shenzhou 13 missions to join up with the Tianhe module later this year. Shenzhou 13 will carry three astronauts for a six-month mission in orbit, according to the China Manned Space Agency.
Next year, China plans six more launches to support the space station program. Two Long March 5B rockets will boost the Wentian and Mengtian lab elements to dock with the Tianhe module, completing assembly of the three-segment space station.
There are also two more cargo spacecraft and two more Shenzhou crew capsules scheduled to launch in 2022.