Every once in a while you hear someone talking about sending missions outside the solar system. Our present speed limitations are fairly well discussed, but lets say someone wanted to plan a 300 year Oort Cloud mission using current propulsion technology. Do we have the technology to power a probe so its instruments would still have energy after all that time? Does anyone know the reasonable maximum battery life we could achieve today? What about the unreasonable maximum battery life, you know, if someone gave you a $10 trillion budget.