Space is not completely empty. Laced throughout the near-vacuum are occasional atoms and molecules of various types, many of which are useful to travelers far from civilization. Many fleets include at least one molecular ram-scoop to collect such molecules for use. Many capital ships include a small ram-scoop on their prow to collect useful materials, but occasionally ships are purpose built to scoop out large swaths of interstellar material. For example, there are several nebulae that contain large quantities of alcohol, and a number of entrepreneurs ply these regions in purpose-built ram-scoop ships collecting it as a rare and expensive luxury good. Many generation-fleets include a scoop-ship as well, in order to add a small amount of useful supplies for the long journey between the stars.