ok now we now know the third vessel is going to be called odysey, now this is my theory on their naming scheme.
The first class was called prommethius, which is a titan/legend
the second class is called daedalus which is a historic figure/inventor
the third class should be journeys or myths - like the odysey or the trojan
the forth class should be mythical beasts - such as hydra or krakken
the fifth class should be mythical places - such as olympus or hades (the place not the god)
the sixth class should be based on heros or superheros - like heracles or perseus
the seventh class should be gods - like athena and apollo
the ship class could be interchanged with the world ship so i would only have to wait another 4 ships to get something called athena on the show - btw i think athena is the best name for a ship defending earth (being goddess of wisdom,protection,warfare, and patron of soldiers and crafts).