- They are considered to be K-class Expedition Ships.
- Since civilizations that use such ships generally have limited means and technology for producing NAFAL starships, most are used for colonization purposes.
- The term also applies to ships where a small living crew stays awake while the rest (...the majority of those aboard) stay in suspended animation. Most examples of Sleeper Ships with FTL propulsion use this arrangement. 
- There are tales of nanotech approaches that stock a ship with seeds and machines in order to build a civilization at the destination. If there actually were any ships like this, they would technically not be Sleeper Ships, as there would be nobody sleeping on the ship, but most of the details would be otherwise identical. 
Library Data Referral Tree
- Colony Ship
- Habitable Zone (Goldilocks Zone)
- Planetary Engineering (Terraforming)
A ship containing a full complement of personnel intended to make a (usually sub-light) journey across space.
- Since such journeys take years, or even decades, the passengers, and sometimes the crew are put into hibernation in Low Berths for the duration of the journey.
- Such ships are smaller (and thus more affordable, and thus more common) than Generation Ships, where the passengers and crew live full lives during the journey.
- The two terms Sleeper Ship and Generation Ship are often, incorrectly, interchanged and used to refer to either type of ship.
Generation vs. Sleeper Ships
Generation Ships are sometimes referred to, incorrectly, as Sleeper Ships, which are similar, except that the majority or all of the passengers and crew are put into low berth hibernation for the duration of the journey. 
In cases where a small portion of those aboard are awake, it is often common to be awake in shifts. For instance, the complement might include 5 crews, each of which handles 1/5th of the voyage then wakes up the next crew before sleeping out the rest of the trip. If the voyage takes 40 years, the crews will only have aged 8 years each, and remain available to participate in the new colony's early years. This also provides backup capability if something goes wrong, similar to the Frozen Watch but on a longer time scale. 
There are also cases where the voyage will only take a few years (sometimes a few weeks), and while the colonists may have skills useful at the colony most of them are not useful aboard ship. The colonists hibernate to reduce life support costs, and to facilitate use of smaller ships, while the crew remains awake for the entire voyage. In these cases, the crew - who are adjusted to shipboard life among the stars, and thus might make poor colonists - may continue flying the ship (possibly returning to where the colonists came from) after their cargo is delivered. 
This is sometimes used to build a colony up in stages with smaller ships. As an extreme example, a ship might carry only 1,000 colonists and their equipment at a time, to a colony 1 week-long jump away from the colonists' origin, building up to 1,000,000 colonists over 100 back-and-forth trips over the span of 40-50 years (2,000 weeks, plus time to load and unload 1,000 times each). These same ships are typically capable of much longer journeys; only the logistics of scheduling multiple trips in a reasonable time span limits their range for such operations. 
History & Background (Dossier)
Colony Ships establish colonies on new worlds, settlements to sustain life and provide socioeconomic commerce.
Polity Users of This Technology
The following species are known to use, have used, or posses the technology to manufacture sleeper ships: