Such a concept is known as a sleeper ship. An alternative to this idea is that the crew live normal lives aboard the starship. This normal life will include having children and as the original astronauts age and die, the children will grow up and be trained to operate the starship. In this way, when the ship finally arrives at its destination, a whole new generation of humans, who were not even born when the starship left Earth, will be running the ship. These designs are known as generation ships.
Propulsion systems are still in the theoretical stage at the moment.
Chemical engines, such as are on the space shuttle, are not powerful enough to provide the thrust necessary for interstellar travel. Another idea is to use powerful lasers and huge collecting mirrors. In the same way that sailing ships use sails to collect the wind so these starships would use mirrors to collect the photons of light. The radiation pressure of the photons would then propel the starship. There are also highly exotic ideas which lie on the tantalising fringes of modern theoretical physics.