R-7 ICBMS AND SPUTNIK

The first ICBM built in the USSR was the R-7, affectionately named Semyorka’ by its makers. It was designed and built by Sergey Korolev’s design bureau, OKB-1, in great secrecy in the 1950s. Its multi-stage design was quite different than the scheme used in the IJS where the stages were stacked on top of one another. The R-7 used a ‘packet’ design in which identical propulsion units were clustered around a central core unit and dropped from the core after burnout. The core continued to burn as the second stage. This concept was suggested by Tsiolkovsky, and championed by M. K. Tikhonravov working at the Defense Scientific Research Institute (NII-4) starting in the late 1940s. Korolev adopted the idea at OKB-1, and in the early 1950s directed feasibility studies by Keldysh’s Department at the Mathematics Institute (MIAN) of the Soviet Academy of Sciences to examine the utility of variants of the scheme. In 1952, work at these three institutes resulted in a preliminary design that evolved tw о years later into the definitive design of the R-7. The Soviet government approved construction of the R-7 on May 20. 1954. with the project designation 8K71. *

The R-7 launcher had a central core propulsion unit 33 meters tall, including the w arhead, with four identical strap-on booster propulsion units around the bottom 20 meters. Each strap-on unit w’as an integral propulsion stage with an RD-107 engine and its own tanks for kerosene and liquid oxygen. The central core was powered by a nearly identical RD-108 engine delivering somewhat less thrust but sustained over a longer time and optimized for high altitudes. Each RD-107 had a pair of gimbaled vernier engines for steering and trim, and the RD-108 had a set of four such engines. The main engines were built by Valentin Glushko’s OKB-456. and each had a cluster of four combustion chambers fed by a single turbopump. All engines, boosters and core, operated for lift-off. The four boosters would burn for about 2 minutes before dropping off, leaving the central core as the second stage sustainer, which continued for several minutes until it had achieved the required velocity and altitude.

The first model of the R-7 was delivered in December 1956 and used for captive tests. The first flight model followed in March 1957. The first three launch attempts failed. On the first, on May 15. 1957, the flight was cut short after 103 seconds when a booster engine failed. The second vehicle was removed from the pad on June 11 after three aborted launch attempts. The third attempt on July 12 failed when the vehicle began to rotate rapidly and shed its boosters. The fourth attempt on August 21 was a qualified success, with the rocket delivering the payload along the desired trajectory, but the payload disintegrated during re-entry. A fifth test on September 7 led to the same result. In these latter tests, how ever, the rocket itself had performed satisfactorily.

R-7 ICB Ms and Sputnik 35

From the very beginning of ICBM development in the late 1940s, Korolev clearly had in mind using his rocket to access space. He repeatedly lobbied the government for support and on January 30, 1956, in response to a letter to the Politburo signed by Korolev, Keldysh and Tikhonravov, a decree was passed for the development of an artificial satellite designated Object D and a special version of the R-7 to launch it. With Object D development proceeding rather slowly, Korolev, fearing that von Braun in America might place the world’s first satellite into orbit, was eager to try to

do so while his R-7 was undergoing its early test flights, and he decided to launch a very simple satellite, essentially a small sphere containing a radio transmitter, after the first successful test flights. Launch vehicle 8K71PS serial number Ml-IPS (PS for ‘Prostcishyi Sputnik*. meaning provisional satellite) was modified by removing unnecessary warhead targeting equipment and test instrumentation, reprogramming the burn sequence, and replacing the dummy warhead with the satellite and shroud. It lifted off on October 4, 1957 and opened the ‘space age’ by placing Sputnik into a slightly lower orbit than planned after the sustainer shut down 1 second early.