Greylorn - Keith Laumer

Commander Greylorn has a problem. No, actually he has two of them. It's not enough that the remaining residents of Earth have pinned their last hope of salvation on him and his mission. He has to find a colony that presumedly was established at an unknown star two centuries before and beg their help. But first, he has the small matter of a mutiny on board his starship, and people are trying to kill him!
Written in an era when radios used vacuum tubes, the scientific component of the story is quaint and dated. But Laumer makes the centerpiece of his tale the retelling of how, four years out on the voyage, his crew decides it wants to give up and go home when it meets an alien race... that apparently breeds humans in captivity as food animals!
Beating the aliens, shanghaiing the crew, finding the colony and saving Mother Earth - just the ingredients for a rattling good yarn! (summary by Mark F. Smith)