SPUTNIK / SCIENCE PHOTO LIBRARY SPUTNIK / SCIENCE PHOTO LIBRARY
Electrical check being made to an SL-4 first stage, the type used to launch Russian Soyuz spacecraft into orbit. The SL-4 is the most-used model of orbital launcher, and was derived from the vehicle that carried Sputnik-1 into orbit in 1957. To the end of 1991, it is estimated that 1042 SL-4 launches had been made, with a success rate of 92.8%, carrying manned Soyuz flights as well as a variety of satellites. The first stage, seen here, consists of a core (top left) surrounded by four strap-on boosters. The boosters use the RD-107 engine, comprising four chambers and two smaller steering verniers. The core RD-108 is identical except having four steering verniers.
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