A new concept for interplanetary and interstellar missions is discussed. Based on a compact spherical tokamak fusion reactor, this concept can potentially revolutionize human space igh ts by providing safe and aordable in-space transportation. The goal of this paper is an assessment of the concept employing the recent advances in fusion research. This concept, in contrast to other fusion concepts, utilizes the natural drift motion of charged particles in order to create a directed ux of energetic particles. The momentum of either energetic positive particles or fusion neutrons can be used either directly for propulsion or to heat the hydrogen propellant. One-way trip times are expected to be on a short time scale, such as one to three months for the trip to Mars. Both the exhaust velocity and thrust of the engine may be modulated. This permits the engine to be optimized for a wide variety of missions.