"[T]hus... any intelligent species would develop at least the rocket technology capable of... a travel velocity ves of 3 x 10-4c. At this velocity the travel time to the nearest stars would be between 104 and 105 years. This... would necessitate... self-repair capacity... Nuclear power-souces would supply the power... If power utilization during the free-fall period was... low, even chemical reactions could supply the power."