Breaking Point

Breaking Point is a science fiction novella written by James E. Gunn, an American science fiction writer, editor, scholar, and anthologist. His work as an editor of anthologies includes the six-volume Road to Science Fiction series.

Excerpts from the book:

The ship was proof against any test, but the men inside her could be strained and warped, individually and horribly. Unfortunately, while the men knew that, they couldn't really believe it. The Aliens could—and did.

They sent the advance unit out to scout the new planet in the Ambassador, homing down on the secret beeping of a featureless box dropped by an earlier survey party. Then they sat back at GHQ and began the same old pattern of worry that followed every advance unit.