China's first cargo spacecraft Tianzhou-1 to launch in April

China's first cargo spacecraft Tianzhou-1 will be launched in April in what will be a crucial test of key technologies needed for the country's future space station.

The cargo spacecraft, with a take-off weight of 13 tonnes, can ship material of up to six tonnes for future space missions.

"The carrying capacity of Tianzhou-1 is designed based on the scale of the space station, in the principle of achieving the highest carrying capacity with the lowest structural weight. There is an index for the spacecraft's carrying capacity, which is called payload ratio. The payload ratio of Tianzhou-1 can reach 0.48, which is a relatively high figure in the world," said Bai Mingsheng, chief designer of Tianzhou-1 at China Aerospace Science and Technology Corporation.

Payload ratio refers to the ratio of the cargo weight to the weight of the spacecraft. A high payload ratio means high carrying capacity of the spacecraft.

The figure is higher than that of the existing spacecraft of Japan and some European countries.

Tianzhou-1 has been specifically designed for refueling and resupplying the future Chinese space station.

The most important task of the Tianzhou-1 spacecraft is to dock with the orbiting Tiangong-2 space lab, which late last year hosted two astronauts for China's longest human spaceflight mission.

It will refuel the space lab in a bid to verify the on-orbit transfer of liquid propellant technology, which is one of the key technologies required in building the future space station.

"Two days after the launch of Tianzhou-1, it will dock with the Tiangong-2 space lab. The whole process takes about two months. After the completion of the two-month docking, we will check the status of the equipment and refill the propellant," said Bai.

China plans to complete its own space station by around 2020 and put it into service around 2022. — Reuters