This shows the evolution of the UR-500 space launch vehicle. For many years, Westerners believed that the clustered modules of the first stage were strap-on boosters. These were in fact only propellant tanks and not self-contained stages. Publication information: Image from the files of Peter Gorin. Image and caption from Challenge to Apollo: The Soviet Union and the Space Race, 1945- 1974 (NASA SP-2000-4408) by Asif A. Siddiqi. Please note that the image number assigned to this image is not an official NASA number. It is for GRIN database purposes only.