Greylorn by Keith Laumer, Science Fiction, Adventure, Fantasy, Space Opera

DESPERATE MISSION TO THE STARS
Earth is doomed.
A scourge called the Red Tide is devouring the planet.
The only hope of the dying population is to find a lost colony in the stars.
However the starship Galahad sent to find that colony has a problem.
Mutiny!
Commander Greylorn must bravely deal with a discouraged crew . . .
And then even a bigger problem.
Dreadful aliens called the Mancji living in a high-G environment who seem to have developed a taste for human flesh.