A mother ship is a vessel or aircraft that carries a smaller vessel or aircraft that operates independently from it. Examples include bombers converted to carry experimental aircraft to altitudes where they can conduct their research (such as the B-52 carrying the X-15), or ships that carry small submarines to an area of ocean to be explored (such as the Atlantis II carrying the Alvin). The mothership may also recover the smaller craft, or may go its own way after releasing it.
The term mother ship dates back to the nineteenth century whaling trade when small, fast ships were used to chase and kill whales. The dead meat from several boats was then brought back to the larger, slower ship for processing and storage until the return to land. This model enabled a far more efficient method of whaling. Though whaling is much lower-scale than in earlier days, the single large storage ship model is still used extensively by fishermen. Such ships are known today as factory ships.
In many languages, such as Chinese, the word "mother ship" refers to an aircraft carrier.
The mother ship concept was used in moon landings performed in the 1960s. Both the unsuccessful American 1962 Ranger landers and the successful Soviet 1966 Luna landers were unmanned spherical capsules ejected at the last moment from mother ships that had carried them to the Moon and crashed onto its surface. In the manned Apollo program, astronauts in the lunar module separated from the command module in lunar orbit, descended to the lunar surface, and returned to dock in a lunar orbit rendezvous with the command module once more for a ride home to Earth.
The term has achieved prominence in science fiction and in UFO lore, which extend the idea to apply to spaceships serving as the heart of a fleet. The concept of mothership (almost always spelled as a single word) clearly implies that the other ships in the fleet are dependent on the mothership for at least some services. Motherships are essentially the sci-fi equivalent to modern flagships. Typically, a mothership will take up station in an area and remain there for long periods, while smaller ships sortie to interesting destinations. Sometimes a mothership is large enough to operate alone, or is so huge that it contains a fleet in its body.
Roles played in a fleet by a mothership may include: