The clipper is a fast long-range cargo ship: a frigate-size ship with most of a freight ship's hold, far more fuel and nearly twice its speed. Being a frigate, it fits every station's dock.
The clipper is locked behind research. An ARCHON unlocks it with trialled freighter designs of its own: one faster than the blueprint and one with a larger fuel tank, which may be the same design. Light materials raise a design's speed, and heat-resistant materials raise its fuel capacity. A Shipyard then builds it from composite, thrusters, a nav computer and a tank.