Voyager probes are under the weight that is otherwise necessary for human life support systems (i.e. fully covering that "we" operative word), Voyager probe travel under the speed that may be considered useful in any way (for human travel or otherwise), and finally (and probably most importantly), the current speed of the Voyager probes is not only the speed buildup provided by their chemical rockets but also of gravitational slingshots around more than one planet.