The first nuclear powered spacecraft, Tansit 4A used ships and aircraft for navigation, was lauched 29 June 1961. In preparation for the celebration of the 50th anniversary of the launching of the first nuclear powered spacecraft attached as a PDF scan of “Space isotopic power systems” by Capt. R. T. Carpenter from the May 1963 issue of Astronautics and Aerospace Engineering, the then monthly magazine of the American Institute of Aeronautics and Astronautics (AIAA). (That entire issue is devoted to “Space Electrical Power.)
P.S. Please excuse the size of the attachment — it was scanned at 300 dpi by a space power expert.
The PDF is posted here with permission of the AIAA (20110608)