Outcasts of Heaven Belt — Joan D. Vinge

Paradise Lost

They came from the distant plant called Morningside on a desperate quest for aid from Heaven Belt. Heaven Belt -- the fabulous asteroid system that was, so legend said, as rich as old Earth. But before the starship Ranger could even explain its mission, it was attacked by the people of the outermost asteroid. For civil war had long since transformed the Belters into isolated societies slowly dying out for lack of technology and natural resources.

Crippled, with most of its crew dead, the Ranger soon became a valuable technological prize fought over by everyone in the Belt. And for the Ranger's crew, what began as a mission of hope became a breathtaking race for survival.