Fueling of the SpaceX rocket has begun. The SpaceX Falcon 9 is a partially reusable, two-stage rocket. It is powered by nine SpaceX Merlin engines. Its first stage uses rocket-grade kerosene and liquid oxygen, while the second stage uses liquid oxygen. The Falcon 9 can lift payloads of up to 50,300 pounds to low-Earth orbit, and 18,300 pounds to geostationary transfer orbit, or GTO. The first stage separates and re-enters Earth’s atmosphere, landing vertically.