The control of a space vehicle can be divided into two parts. The most obvious part includes the rockets and airfoils that directly steer the vehicle and control its speed. Less apparent are the computer systems that control the rockets and airfoils. These systems rely on measurements from various instruments, as well as knowledge of the vehicle's planned route, to determine how the rockets and airfoils should be used.

In a way, these computer systems act collectively like a car driver who relies on what she knows and senses to make decisions about car speed and direction. The driver then uses the steering wheel, gas pedal or brakes to act on these decisions, just as the computer systems would use the rockets or airfoils of a space vehicle. Similarly, while a car driver can refer to landmarks and street signs to determine if the car is...