The Cometeers by Jack Williamson 1977

In this, the second of Jack Williamson's Legion of Space series, the reader will encounter such marvels as a spaceship twelve million miles long.

The secret weapon that controls the universe... a superhuman traitor to all mankind and of course, the greatest trio of swashbuckling adventurers in all of science fiction, the Legionnaires of Space themselves.

Thrill to their breathtaking adventures as they defy mortal peril and fantastic danger in the fight against the dread powers of the invincible Cometeers and a monstrous threat to the security of the Solar System.