US space agency NASA announced on Thursday that it has awarded the second round of commercial contracts to resupply the International Space Station to three private spaceflight companies Orbital ATK, Sierra Nevada and SpaceX.Every one of these companies gets at least six flights to deliver cargo to the space station, which will begin in late 2019 and extend through 2024, Xinhua quoted NASA as saying.Orbital ATK of Virginia and SpaceX of California, the winners of the first round of NASA's Commercial Resupply Services contracts, have already used their own space capsules to send supplies several times to the orbiting lab about 400 kilometers above Earth.The only new face is Colorado-based Sierra Nevada, which has been developing a mini-shuttle called Dream Chaser.