Ironmonger

Taran, the only spaceship on Earth, is sent by its owners to investigate an anomaly that has turned up in the Sun's system. Astronomers believe that it is not a naturally occurring body. The five member shake-down crew, who took Taran aloft the first time during a competitor's raid, are at the controls again. The anomaly turns out to be a garbage scow, the crew dubs "Ironmonger." It came from another system where space wars are being fought. Ironmonger collects derelict warships. Taran is pulled in too. The crew has four problems: Find water for fuel to get home, fight off the various aliens who were also collected, overcome the attractor beam they can't fly against and turn Ironmonger so none of that alien technology comes anywhere close to Earth.