Lucky Starr and the Moons of Jupiter

Sabotage!!!
Agrav. It was the century’s most important advance in space travel…and an experiment so revolutionary that only the men who huddled beneath the surface of Jupiter Nine were permitted to know its full meaning.
Yet someone else *did* know–knew *everything* , saw *everything* , head *everything* –and was diabolically sabotaging the top-secret mission.
Who or *what* the enemy was, Lucky Starr didn’t know. but one thing was certain. The deadly force was not human…not even remotely human!