A space probe to the interstellar medium has proven elusive due to the substantial distances involved. A realistic mission that has some hope of being implemented must have a planned mission length measured in decades at the most. Robotic missions must rely upon proven technology and launch vehicles. Evolutionary advance of some systems may be considered on anew mission, but only as long as the developmental risks appear to be low. Against this backdrop, a scientific requirement for such a mission has been articulated and advocated for 30 years. Propulsion has always been the driving problem. Previous studies have considered ballistic near-Sun gravity assists, large Nuclear Electic Propulsion (NEP) systems, and small solar-sail driven systems. In each case, the propulsion technology has been – and remains – just out of reach. We have provided a first cut of a self-consistent design for such a mission using Radioisotope Electric Propulsion (REP), existing launch vehicle hardware, and a Jupiter gravity assist. While the final speed of the probe is not as high as might be wished, it is sufficiently high to provided new – and potentially transformational – knowledge of our surroundings in interstellar space. More importantly, the required technology advances are evolutionary such that the probe could be built – and launched – as soon as the next launch window opens in late 2014.