How Fast Must a Spacecraft Travel to Reach Orbit?

To reach Earth orbit, a rocket must accelerate to about 8 kilometers (5 miles) per second--about 25 times faster than the cruising speed of a passenger jet. To escape Earth's gravity, it must travel even faster. To accelerate even a small payload (the object being sent into space) to such speeds takes a huge amount of energy, which rockets carry in the form of propellants.

(Rev. 09/22/96)