In 1953, Captain 2nd Rank Osipenko was given command of one of the largest submarines, the B-12. He earned an impeccable reputation in the Pacific Fleet as a competent and skilled commander. In August 1955 he was appointed captain of the first Soviet nuclear submarine “K-3”. The crew was trained in Obninsk at the world’s first nuclear power plant and a special simulator.

 
In August 1957 the first Soviet nuclear submarine was launched. Leonid Gavrilovich commanded the nuclear submarine for two years, sailing to the Arctic, to Novaya Zemlya, and to the Greenland Sea. In June 1959, “for the courage and bravery shown while testing special equipment” he was awarded the title of the Hero of the Soviet Union. The same year he was appointed commander of the Navy Training Center in Obninsk, and three years later he was promoted to the rank of Rear Admiral.

 
Leonid Gavrilovich Osipenko headed the Naval Center in Obninsk for 20 years. In the early 1980s, the staff of the Obninsk City Museum visited Leonid Gavrilovich to collect materials on the subject of “The First Honorary Citizens of the City”. At that time Osipenko’s work and the activity of the Navy Training Center in Obninsk was a classified subject and it was impossible to obtain the exhibits. Leonid Gavrilovich found a way out: he took a submarine badge off his tunic and gave it to the museum, saying that it was a very dear item to him, the badge of a submarine commander.