A Capital Ship is a Federation ship that acts as a command post.
The Federation created these as launch points, and special bases in orbit over a planet.
In Operation: StarBlade three Capital Ships launched into orbit and launched Team: GeoSword to deal with RedEye. Shortly after launch they were attacked by the UIMS fleet. But the alien-mechs were defeated by the GeoSword. After RedEye and IceBerg were destroyed, the GeoSword returned to the Capital Ships and the Capital Ship went home.