Credit: CCTV/Inside Outer Space screengrab

Another step toward China’s space station program has been successfully accomplished. The country’s Tianzhou-3 cargo spacecraft was launched on Monday, delivering supplies to the construction site of the Tiangong orbital outpost.

The craft docked with the country’s space station’s core module Tianhe at 10:08 pm on Monday, 6.5 hours after its launch, according to the China Manned Space Engineering Office. The cargo ship docked onto Tianhe’s backward facing port using the automatic fast docking process.

Credit: CCTV/Inside Outer Space screengrab

Multiple launches

A Long March-7 Y4 rocket hurled the Tianzhou-3 spaceward, blasting off from the Wenchang Spacecraft Launch Site in the southern island province of Hainan.

Prior to the launch, on September 18, the Tianzhou-2 cargo craft separated from the rear docking port of Tianhe core module and docked with its front docking port – making way for the newer supply craft.

Credit: CCTV/Inside Outer Space screengrab

China launched its space station core module Tianhe on April 29. The country plans to complete the verification of key technologies and the in-orbit construction of the space station through multiple launches within two years. The Earth-circling facility is slated to be completed by the end of 2022.

Five tons of cargo

The Tianzhou-3 cargo spacecraft has been fine-tuned for its mission to deliver supplies and prepare for the following Shenzhou-13 crewed mission next month.

“Compared with its predecessor Tianzhou-2, Tianzhou-3 is also fully loaded with nearly five tons of cargo including more than 200 packages,” said Yang Sheng, general chief designer of the cargo spacecraft system of the China Academy of Space Technology under the China Aerospace Science and Technology Corporation.

“According to the plan, the Shenzhou-13 crew will stay in orbit for six months, and we have to make an adjustment accordingly to the supplies delivered by Tianzhou-3 to ensure their healthy stay in orbit during this period,” Yang told China Central Television (CCTV).

Credit: CCTV/Inside Outer Space screengrab

Construction project

Cheng Tangming, chief designer of the Long March-7 carrier rocket told CCTV that the space station construction is in full swing.

“This was the fifth launch for the construction project, which will be followed by seven other launches to be completed next year. We will turn into the next launch mission right away,” Cheng said.

On Sept 18, the Tianzhou-2 cargo craft separated from the rear docking port of Tianhe and docked with its front docking port.

At this stage of station construction, the rendezvous and docking of Tianzhou-3 and the Tianhe core module required the rocket to be launched within a short and pre-calculated time frame.

Docking of Tianzhou-3 cargo spacecraft with core module.
Credit: CNSA/China Media Group/CCTV/Inside Outer Space screengrab

“The deviation of the rocket entering orbit must not exceed four seconds. This is a very high accuracy requirement,” said Zhang Borong, designer-in-charge of the orbit of Long March-7 rockets. “Only if the launch is accurate on time, can the cargo spacecraft effectively dock with the space station. There are very high requirements for the launch time, the orbit entry time, and the accuracy and position of the orbit entering process.”

Credit: CCTV/Inside Outer Space screengrab

Propellant carried by Tianzhou-3 will be used for the combination of the space station core module Tianhe and cargo crafts, and its engines will be used by the core module for attitude and orbit control, and regular in-orbit maintenance, so as to ensure safe operation of the combination, said Yang.

In addition, engineers have also developed an intelligent cargo management system to facilitate astronauts in finding their items. A QR code is printed on the surface of each of the 40-plus lockers installed in the 40-cubic-meter cargo. By scanning the code, astronauts will easily identify what’s inside.

Fast automated rendezvous

Shortly after takeoff, Xu Xiaoping, deputy chief designer of the cargo spacecraft system at the Fifth Academy of China Aerospace Science and Technology Corporation (CASC), said the newly launched cargo vehicle will go through multiple steps before docking with the already orbiting core module and Tianzhou-2 supply vehicle.

Credit: CCTV/Inside Outer Space screengrab

“We will continue this fast automated rendezvous and docking of ours. We started to give the instruction for rendezvous and docking about 15 minutes after the spacecraft entered the orbit just now. After about 45 minutes, we may start the first orbital transfer. Through a total of six orbital transfers, we will finish the remote-controlled, automated instruction in three hours and 45 minutes. After another three hours, we may start our capture of the docking mechanisms. About 15 minutes after the capture step, the docking will be completed in success. Then we will do some settings for its postures. Then the Tianzhou-3 spacecraft can form a combination with the core module and Tianzhou-2 to operate in orbit,” Xu said in a CCTV interview.

Credit: CCTV/Inside Outer Space screengrab

The Wenchang Spacecraft Launch Site has carried out 13 launch missions since 2016. And the launching of the Tianzhou-3 cargo spacecraft will be the 14th.

“China’s space missions have evolved from single tasks to big projects, such as the space station construction involving the participation of two launch sites, Jiuquan and Wenchang, three types of rockets, space station, cargo spacecraft, Shenzhou spacecraft and other spacecraft, which is a very complicated systematic project. For us, it is an unprecedented project,” Mao Wanbiao, deputy director of Xichang Satellite Launch Center, told CCTV.

China’s space station is projected to be completed in late 2022.
Credit: CAST









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