Space Launch, Russia

• Escape velocity
If the Earth's gravity is to be overcome entirely then sufficient energy must be obtained by a spacecraft to exceed the depth of the gravity potential energy well. Once this has occurred, provided the energy is not lost in any non conservative way, then the vehicle will leave the influence of the Earth. The depth of the potential well depends on the vehicle's position, and the energy depends on the vehicles speed. The kinetic energy exceeds the potential energy then escape occurs. At the Earths surface this occurs at a speed of 11.2 km/s, but in practice a much higher speed would be needed due to airdrag.