TESTING THE RD-0120

Before the beginning of the Energiya-Buran program the only liquid oxygen/liquid hydrogen engines developed in the Soviet Union had been the 7.5-ton thrust 11D56 of KB Khimmash and the 40-ton thrust 11D54 and 11D57 of KB Saturn, intended to be used on upper stages of the N-1 rocket. Therefore, the development of the 190-ton thrust RD-0120 for Energiya’s core stage, assigned to KBKhA in Voronezh, was a major challenge, partly because much of the infrastructure needed for testing the engine was not yet in place. This required a step-by-step approach to certifying the engine for flight. The first step was to test individual components of the engine, followed by test firings of experimental engines at increasing rates of thrust, and ultimately test firings of flightworthy engines both individually and mounted in clusters of four on Energiya’s core stage at Baykonur’s UKSS pad.

Since the RD-0120 was the first powerful Soviet cryogenic engine, many com­ponents that would usually be installed straightaway in experimental engines now had to be tested individually first. Particular attention was paid to the ignition system in the combustion chamber and the gas generator as well as to the operation of the low-pressure turbopumps. The components for these tests were built both by KBKhA’s own Experimental Factory and by the Voronezh Machine Building

Factory and tested at various locations in the Soviet Union, including KBKhA’s own experimental base in Voronezh.

While KBKhA had its own rocket engine test stands near Voronezh, none of these could be converted for test firings of this radically new engine, nor was it deemed expedient to build the new facilities there. Instead, test firing stands for the RD-0120 were built by two other organizations. One was the Scientific Research Institute of Machine Building (NII Mashinostroyeniya or NIIMash) in Nizhnyaya Salda north of Yekaterinburg. This organization had become independent in 1981 after having been a branch of the Scientific Research Institute of Thermal Processes (NII TP), which was how the former NII-1 was renamed in 1965 (in 1995 it was again renamed as the Keldysh Research Centre). NIIMash mainly specialized in reaction control thrusters for satellites and manned spacecraft (including Buran).

NIIMash had two test stands (nrs. 201 and 301) for firing the RD-0120 in vertical position. Construction got underway in 1977 and 1981, respectively. The test stands allowed the engines to be gimbaled and had diffusers to simulate operating conditions at higher altitudes. Stand nr. 301 was capable of handling longer duration test firings (over 1,000 seconds) and maximum gimbal angles. RD-0120 engines were delivered to Nizhnyaya Salda from the manufacturing plant in Voronezh by Antonov-8 cargo planes.

The other organization was NIIkhimmash near Zagorsk. It had a cryogenic complex called KVKS-106, already used before the Energiya-Buran program for testing the 11D56 and 11D57 cryogenic engines. KVKS-106 comprised five test facilities, one of which had two test stands (V-2A and V-2B) for full-scale test firings of the RD-0120 in horizontal position. Others were used to test individual components of the engine and the core stage. The engines were transported from Voronezh to NIIkhimmash by road.

The bulk of the testing was to be carried out at Nizhnyaya Salda, but, as the construction of the facilities there ran into delays, it was decided to test the first engines at the existing cryogenic complex of NIIkhimmash. The first test engine (with

a shorter-than-nominal nozzle) was delivered to Nllkhimmash in the autumn of 1978 and underwent a first brief test firing (4.58 seconds) at the V-2B stand in March 1979. The initial tests at Nllkhimmash were conducted at just 25 percent of rated thrust, but allowed to test such things as the ignition and shutdown sequence. The adjacent V-2A, capable of supporting tests at 100 percent thrust, was ready in 1984.

The first test firing at NIIMash’s test stand nr. 201 took place on 19 January 1980, also at low thrust. By early 1981 the engine was being tested at 70 percent thrust, and it wasn’t until May 1984 that the RD-0120 worked at 100 percent thrust for 600 seconds (with the nominal operating time during launch being 467 seconds). Considerable delays in reaching nominal thrust were caused by problems with the impeller of the liquid hydrogen pump, a rotating disk with a set of vanes that produces centrifugal force within the pump casing. The problem was eventually solved by using a different type of titanium to manufacture the component.

Although the RD-0120 test program took longer than expected, it does not appear to have been a major factor in the delays of Energiya’s first launch. By the time of that maiden launch in May 1987 the Russians had accomplished 523 test firings of 103 different RD-0120 engines with a total duration of 73,891 seconds. NIIMash’s test stand nr. 301 saw its first test firing on 30 July 1987. Records set during that same period were a 100-second test at 123 percent rated thrust in September 1987 and a maximum-duration burn of 1,202 seconds in January 1988. By early October 1988, about a month before the maiden flight of Buran, a total of 126 engines had undergone 635 test firings lasting a total of 120,454 seconds. By comparison, NASA accumulated 110,253 seconds of burn time on the Space Shuttle Main Engines in 726 test firings before STS-1.

The RD-0120 test program continued at Nllkhimmash even after the cancella­tion of the Energiya-Buran program under a deal between KBKhA and the US Aerojet company to study the feasibility of using the engine on future American launch vehicles. Several test firings were also performed in the mid-1990s in the framework of the joint European-Russian RECORD program (Russia-Europe Cooperation on Rocket Engine Demonstration), led by the French SEP company. In those tests, the engine was equipped with European instrumentation to allow European engineers to create a detailed software model of the engine and gain experience with staged-combustion cycle cryogenic engines for possible use in future reusable systems. The final test firing of the RD-0120 was conducted at Nllkhimmash in 1997. The maximum accumulated test time for a single engine was about 5,000 seconds and the maximum number of ignitions for a single engine was thirty [2].