Keldysh was a Soviet mathematician and physicist who was one of the key figures in the development of the Soviet space program. He was part of group of applied mathematicians that worked on many large scientific soviet progects. He created the Calculation Bureau which addressed most of the mathematical problems related to the development of Soviet nuclear weapons.
Stamp  Description 

Russia, 4k, 1981 Scott: 4906 A2328 

Russia, 12r, 2011 Scott: 7254 A3533 