Space Rats represent a minority portion of the Spacers. While your typical run of the mill Spacer serves aboard pristine and readily serviceable star ships, the Space Rats have craft that are in "less than splendid" condition. The typical Rat ship is a hodge-podge assembly of second-hand parts that rarely match up to the hull they have been attached to. Evidence of major repair & reconstruction is readily visible via various discoloring and shoddy overlapping on the hull panels. More often than not the drives do not match, they may be of the appropriate size specified for the craft in question but chances are each one began life on different vessels before being mated to the ratty hull.
The ship crews tend to run heavy on engineering skills, for they are needed on such craft due to their age and random mish-mash reconstruction efforts. As such, Space Rat crews work a little harder than standard Spacer crews...but their reward is satisfaction of a job well done on a ship that cost a fraction of what a new/newer ship would have set them back.
