China has successfully sent a cargo craft to dock with and refuel its Tiangong-2 space lab,taking a crucial step towards establishing a permanent space station by 2022.Lifting off from China’s new Wenchang Satellite Launch Center on April 20,2017,the Tianzhou("Heavenly Boat")-1 cargo resupply spacecraft first rendezvoused with Tiangong("Heavenly Palace")-2 in