(Source: CGTN)

The Tianzhou-1 will function as the main cargo transport and propellant supplier for China's planned space station.

Tianzhou-1 is approximately 11 metres high, with a maximum diameter of 3.35 meters. Weighing 13 tons when fully loaded, Tianzhou-1 is so far the largest and heaviest spacecraft in China - much bigger than the Tiangong-2 space laboratory and Shenzhou spaceship. The cargo spacecraft consists of two parts. The propeller is installed in the top module, while the lower part with a larger diameter is the cargo space.

China's Shenzhou manned spacecraft, the spacecraft currently in use, can only send three astronauts and 300 kilograms of goods at a time. If astronauts are to stay for longer periods at the space station, they will need a large amount of food, water, oxygen and backup materials. This, in turn, requires a cargo ship with greater carrying capacity. The Tianzhou-1 is specially designed to provide supplies for China's future orbiting space station and will be able to send 5 tons of cargo into space.

"The carrying capacity of Tianzhou-1 is designed according to the size of our space station. It seeks to carry as much as possible in the minimum size. There is a special indicator called a payload ratio when it comes to the carrying capacity of the Tianzhou-1. We will reach a payload ratio of 0.48 in the future, which is a world leading standard," Bai Mingsheng, Tianzhou-1 chief designer of China Aerospace Science and Technology Corporation, said.

The payload ratio is calculated by dividing the weight of the payload by the mass weight of the spacecraft. It is a significant index when assessing a cargo spacecraft. The higher the number, the more efficient a cargo spacecraft is. 0.48 suggests a first-class carrying capacity that surpasses spacecrafts presently used in Europe and Japan. Meanwhile, the Tianzhou-1 introduces the design concept of building blocks and will have three cargo capabilities to fulfill the different needs of the space station.

"This pressurized cargo, for example, has outstanding transport capacity and can carry a large amount of daily necessities. A semi-pressurized one, on the other hand, is separated into two rooms so that it can store some big maintenance spare parts, such as solar panels. And there is also an unpressurised cargo for large-scale experiment equipment. Different cargo capabilities can fulfill different needs in the future," Bai said.