The Skylark of Valeron by E.E. Smith — Read

Day after day a spherical space ship of arenak tore through the illimitable reaches of the interstellar void. She had once been a war vessel of Osnome; now, rechristened the _Violet_, she was bearing two Terrestrials and a Fenachrone -- Dr. Marc C. DuQuesne of World Steel, "Baby Doll" Loring, his versatile and accomplished assistant, and the squat and monstrous engineer of the flagship _Y427W_ -- from the Green System toward the Solar System of the Fenachrone. The mid-point of the stupendous flight had long since been passed; the _Violet_ had long been "braking down" with a negative acceleration of five times the velocity of light.

Much to the surprise of both DuQuesne and Loring, their prisoner had not made the slightest move against them. He had thrown all the strength of his supernaturally powerful body and all the resources of his gigantic brain into the task of converting the atomic motors of the _Violet_ into the space-annihilating drive of his own race. This drive, affecting alike as it does every atom of substance within the radius of action of the power bar, entirely nullifies the effect of acceleration, so that the passengers feel no motion whatever, even when the craft is accelerating at maximum -- and that maximum is almost three times as great as the absolutely unbearable full power of the _Skylark of Space_.