A long ship, and a moon to steer her by

The earliest fractional C capable intra-solar craft, also known colloquially as "stack ships", were little different in their basic construction from the vessels that pioneered Earth orbit and trans-Lunar travel. They were constructed from modules, just as those earlier craft had been, but were powered by far more sophisticated drive systems which made travel throughout the solar system a relatively routine affair, taking no more than a few months to reach even the objects of the Kuiper Belt.