Lucky Starr and the Moons of Jupiter

Lucky Starr and Bigman Jones journey to the remote moons of Jupiter to find the spy who is leaking the vital secrets of the hyperatomic engines of a prototype spaceship to the enemy Sirians.

Lucky Starr and the Moons of Jupiter is the fifth book in the Lucky Starr series written by the legendary Isaac Asimov, author of I, Robot, Foundation, and the Galactic Empire series.

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!