A flight vehicle is a device that flies in the atmosphere or outside the atmosphere (space). Aircraft are divided into three categories: aircraft, spacecraft, rockets and missiles. Aircraft flying in the atmosphere are called aircraft, such as balloons, airships, airplanes, etc. They fly by the static buoyancy of the air or the aerodynamics generated by the relative motion of the air. Spacecraft flying in space are called spacecraft, such as artificial earth satellites, manned spacecraft, space probes, space shuttles, etc. They are driven by the launch vehicle to get the necessary speed into space, and then rely on inertia to do orbit similar to the celestial body.