Journey To Mars

Launching from Earth is the most fuel-intensive process in the whole journey as the spacecraft must overcome the massive gravitational attraction of the Earth. To do this, it must use carefully engineered fuel systems, guidance and navigation systems and aerodynamic design principles. While many people think that launching from Earth is a simple feat of just going straight up high enough, this is not the case. In fact, the spacecraft has to go fast enough sideways in order to keep falling but missing the Earth. The graphic below illustrates that if you launch a cannon from the surface of the Earth at a fast enough speed (ignoring air resistance), it will eventually come back around. This is exactly what a spacecraft must do to get into orbit, but also get high enough so that the atmosphere contributes very little drag.