The most common role of sleeper ships in fiction is for interstellar or intergalactic travel, usually at sub-light speed.
Travel times for such journeys could reach into the hundreds or thousands of years, making some form of life extension, such as suspended animation, necessary for the original crew to live to see their destination.
Freezing the astronauts would probably involve whole-body vitrification and would, most likely, be frozen at 145 kelvins to reduce the risk of fracturing.
[1][better source needed] Suspended animation can also be useful to reduce the consumption of life support system resources by crew members who are not needed during the trip, or by an author as a plot device, and for this reason, sleeper ships sometimes also appear in contexts involving travel within the solar system or any other system of planets orbiting one star.
There are numerous examples of sleeper ships in science fiction literature and films.