Transit 4A , launched June 29 , 1961 , was the first satellite to use a radioactive power source ( RTG ) ( a SNAP-3 ) . Transit 4B ( 1961 ) also had a SNAP-3 RTG . Transit 4B was among several satellites which were inadvertently damaged or destroyed in a nuclear explosion , specifically the United States Starfish Prime high-altitude nuclear test on July 9 , 1962 and subsequent radiation belt
Starfish Prime
Starfish Prime
Transit (satellite)