R-7E AND THE EARLY LENA PROBES

On March 8, 1957 Korolev’s OKB-1 founded a new department to develop manned satellites and spacecraft for lunar exploration. It was headed by Tikhonravov, and in April he submitted the first plans. These required that the basic 8K71 R-7 rocket be fitted with a third stage, and by the summer of 1957 technical plans were completed. The third stage would be mounted on top of the sustainer using an open truss so that its engine could be started before the sustainer was shut down – a measure designed to prevent the cavitation in the propellant tanks that would occur in zero-G if ignition were to be delayed until after the core stage had shut down.

Work began on two different vacuum-performance engines for the third stage, one by Glushko s design bureau, OKB-456, and the other by OKB-1 itself, working with Semyon A. Kosberg’s OKB-154 in Voronezh. The decision to build two versions of the third stage originated in a clash between Korolev and Glushko concerning the development of Glushko’s engine, resulting in a bitter rivalry that persisted through the development of the ill-fated N-l Moon rocket and contributed to the ultimate failure of the Soviet manned lunar program. Glushko wanted to develop a powerful 10-ton thrust engine using new hvpergolic fuels, unsymmetrical dimethlyhydrazine (UDMH) and nitric acid, instead of the standard kerosene fuel used by Korolev and Kosberg’s 5-ton thrust engine. However, Korolev was wedded to the LOX-kerosene combination and disliked Glushko’s toxic fuel, calling it “the devil s own venom”. He doubted that such a new engine could be developed in time for his schedule, which called for the first test of the three-stage rocket in June or July 1958, the launch of a lunar impact probe in August or September, and a flyby mission to photograph the far side of the Moon in October or November. He ordered the development of a 5-ton thrust engine at OKB-1 based on the R-7’s verniers. He was aware of developments at Kosberg’s aviation design bureau, w’hieh was working on a restartable LOX-kerosene engine using a new turbopump based on jet engine designs. To speed his ow7n development at OKB-1, Korolev engaged К os berg. As a neophyte in the rocket engine business, К os berg initially demurred, but Korolev persuaded him to collaborate on an engine that could operate in vacuum. For his part, Glushko was not happy with this parallel work, especially since OKB-154 was outside the circle of space developers. Glushko felt that he was due deference from Korolev, and he considered Korolev*s overtures to Kosberg an insult. But Korolev’s instincts proved correct. Glushko was struggling with problems when Kosberg’s engine became available for use in August 1958. It used a higher density kerosene to yield the needed thrust levels. The development of a third stage based on Glushko s engine was finally canceled in 1959.

Korolev’s ambitious schedule had to take second priority to developmental tests required to make the basic R-7 an operational ICBM. During the first half of 1958. his lunar plans were constantly threatened by difficulties with numerous changes to the engines and failures in development flight tests. A prototype of the lunar rocket with a dummy third stage equipped with avionics and telemetry, but no propulsion, was launched on July 10. 1958, powered by an improved set of booster and sustainer engines but these failed a few seconds into the flight, bringing down both the rocket and the timetable. Korolev shot for the Moon at the earliest opportunity on the very first flight of the new third stage on September 23, 1958. This and a second attempt on October 12 failed when the boosters fell apart and all flights had to be suspended until the problem was analyzed and fixed. Frustratingly, the cause turned out to be longitudinal vibrations in the strap-on boosters caused by the addition of the third stage. With this problem fixed, a third attempt failed on December 4, 1958, when the second stage engine shut down prematurely. On January 2, 1959. the rocket worked properly and although Luna 1 did not impact the Moon, the 6.000 km flyby was a sufficiently impressive achievement for the Soviets to declare that this had been the objective.

This R-7E. which tvas an 8K71 with a Block E third stage, was designated 8K72 and informally known as the ‘Luna’ launcher. It could put 6 tons into low Earth orbit and send 1.5 tons into deep space. It was used exclusively for the first generation of Luna probes in 1958 1960 including the successful Luna 1, 2 and 3. It came to an ignominious end with an explosive failure less than one second into the flight of the final such probe on April 19. 1960. The booster and core stages w’ere upgraded and the third stage improved, including upgrading its engine, to produce the 8K72K three-stage heavy lift orbital version of the R-7. This was used to launch the manned Vostok orbital spacecraft and the first Soviet photoreconnaissance satellites, known as the Zenit 2 series.