Category Energiya-Buran

It was not until 14 March 1985 that the 4M stack was once again erected on the UKSS for the long-awaited fueling tests of the core stage’s oxygen and hydrogen tanks. While the Russians had plenty of experience with loading liquid oxygen tanks, they were newcomers to fueling big hydrogen tanks, the more so because they used a special type of subcooled liquid hydrogen. After an initial series of tests in which the hydrogen tank was conditioned with nitrogen and hydrogen gas, the core stage was declared ready for the fueling tests. Between mid-April and late September 1985 the 4M core stage underwent nine fueling cycles. These included both partial and full loads of the hydrogen and oxygen tanks separately as well as one complete load of the entire core stage. After each test, engineers carefully checked the condition of the core stage’s outer insulation layer. While the insulation remained intact during and after fueling, some debonding was observed during draining of the tanks.

The 1985 pad tests were rounded out in the first days of October with several other tests of the core stage, including a nitrogen purge of the stage’s tail section and two test firings of the hydrogen igniters, needed to burn off any excess hydrogen gas accumulating on the launch pad prior to engine ignition. A derailing incident during the roll-back of the 4M stack on 5 October did not result in any damage to the vehicle [8].

The US Defense Department estimated in the early 1980s that the HLLV would fly first in 1986-1987, followed by the Soviet orbiter in 1987-1988. Ironically, this prediction was more realistic than what was being planned by the Russians, who had a history of setting optimistic timelines for their space projects. When the Energiya-Buran program was approved in February 1976, the goal had been to fly the maiden mission in 1983, but this date started slipping soon. A government decree in December 1981 moved the target date to 1985 and another one on 2 August 1985 set the mission for the fourth quarter of 1986 [26]. Even that must have been a completely unrealistic goal given the progress made by that time in rocket and orbiter testing. A major factor in the delays probably were the serious problems with test firings of the RD-170/171 engines in the early 1980s, although other technical as well as budgetary issues must also have come into play.

As mentioned in the previous chapter, original plans apparently called for launching the first two missions of Energiya with mock-up orbiters that would remain attached to the rocket and re-enter together with it. Later those plans were dropped in favor of launching a real orbiter on the first Energiya mission. Then, as Buran ran into delays, it was decided to turn a test model of Energiya (6S) into a flightworthy version (6SL) and launch that with the Polyus/Skif-DM payload, moving the Buran mission to the second flight of Energiya.

On 10 January 1989 NPO Energiya general designer Valentin P. Glushko passed away at age 80. On 8 April 1988 Glushko had suffered a stroke in his office, but wasn’t found until four hours later. He underwent complex neurological surgery the following day, but never made a full recovery. Glushko spent most of the final months of his life in hospital, watching the Energiya-Buran mission on television rather than witnessing it first hand [6].

Glushko’s death set in motion an internal battle within NPO Energiya to name his successor. On 23 January 1989 leading officials at NPO Energiya sent a letter to the Central Committee, VPK, and MOM, recommending Yuriy P. Semyonov as Glushko’s successor. After a six-year stint at Yangel’s OKB-586, Semyonov had

joined Korolyov’s OKB-1 in 1964 and had quickly risen through the ranks of the design bureau, possibly helped by the fact that he was the son-in-law of the influential Politburo member Andrey Kirilenko, who also was the de facto head of the Soviet space program in his capacity as Central Committee Secretary for Defense Matters from 1979 to 1983. Semyonov began his career at OKB-1 as a leading designer of the Soyuz spacecraft and the L-1 (“Zond”) circumlunar vehicles, going on to become the chief designer of Soyuz and Salyut in 1972. After the split of the Energiya and Buran offices within NPO Energiya in 1981 he also became chief designer of Buran.

It wasn’t until 21 August 1989, after another appeal from leading NPO Energiya officials the month before, that Semyonov was officially named general designer of NPO Energiya, following in the footsteps of Korolyov, Mishin, and Glushko. One also wonders if there wasn’t unequivocal support from Minister of General Machine Building Vitaliy Doguzhiyev, a former classmate of Semyonov, although he left the post to Oleg Shishkin in July 1989. The official history of NPO Energiya (edited by Semyonov!) largely attributes the 7-month power vacuum at NPO Energiya to Boris Gubanov’s attempts to split off his rocket design department from the bureau and incorporate it into an independent design bureau for the creation of heavy-lift launch vehicles and upper stages. After the death of “rocket man’’ Glushko, Gubanov had evidently become worried about the future of his department within NPO Energiya, which did not only work on Energiya itself, but also on various derived launch vehicles that had no immediate relevance to the piloted space programs that were NPO Energiya’s main focus.

The June 1989 government decree resulting from the May meeting of the Defense Council had basically given the go-ahead for further development of such systems, but according to Gubanov’s memoirs the plans were scrapped by the so-called Scientific Technical Council of NPO Energiya on 18 August 1989 (three days before Semyonov’s official appointment). The only exception was Energiya-M, a lightweight version of Energiya. Gubanov describes this move as the “initial castration” of the Energiya program. According to the official NPO Energiya history the Council

divided the company’s space-related activities into five levels of priority:

(1) Energiya-Buran and Mir.

(2) Heavy payloads for Energiya, including a geostationary communications

platform.

(3) The Mir-2 space station and the further modification of Soyuz.

(4) Work on future air-launched systems (including reusable ones), spaceplanes,

“reusable multipurpose space systems’’, piloted Mars missions, further improve­ment of Energiya-Buran (including work on a reusable strap-on booster).

(5) Other work, including that on the Blok-D upper stage.

In September, Semyonov canceled plans for the GK-199 mission, ordering instead preparation of the Energiya vehicle 2L for the launch of a massive geostationary communications platform by the end of 1992, even though the development of such a platform and the upper stages to place it into the required orbit were only in an embryonic stage.

On 28 August 1989 Gubanov wrote a letter to Gorbachov, warning him that the Energiya program was to suffer the same fate as the N-1 unless action was taken to make it economically viable. He once again outlined plans for Energiya-M, cargo versions of the standard Energiya, and fully reusable versions of Energiya, arguing that such systems could save costs by orbiting heavier satellites with more built-in redundancy and hence longer lifetimes. Effective development of such rocket systems, Gubanov once again stressed, could only be performed by a specialized design bureau. Gorbachov directed the task of looking into that possibility to Oleg Baklanov, who was now the Central Committee Secretary for Defense Matters after having served as Minister of General Machine Building from 1983 until 1988. One option considered was a merger of three organizations based in Kuybyshev—namely, the Volga Branch of NPO Energiya, the Central Specialized Design Bureau (TsSKB), and the Progress factory. The idea met with stiff opposition from Semyonov and TsSKB chief Dmitriy Kozlov, the latter having already refused to become involved in Energiya in the mid-1970s.

On 29 September 1989 a new structure was officially approved for NPO Energiya. Responsibility for the orbiter was now in the hands of Department 351 under the leadership of V. N. Pogorlyuk. Gubanov remained in his function as chief designer of the entire Energiya-Buran system, but the sections working under him on future versions of Energiya were abolished. A final decision on the creation of a new launch vehicle design bureau was to be made at a meeting of the Central Committee in March 1990, but no consensus was reached, leaving the issue unresolved. At a meeting on 7 May 1990 the Scientific Technical Council of NPO Energiya decided that the formation of such a bureau was “inexpedient”. Gubanov was eventually dismissed from NPO Energiya on 5 March 1992 for his involvement in a deal between the Progress factory and an organization called Kazakhobshchemash to sell Soyuz rockets to Kazakhstan, although Gubanov himself saw it as just an excuse to get rid of him. With that move the post of “chief designer of Energiya-Buran’’ was officially abolished. Gubanov retired and passed away in 1999 [7].

Since the core stage was suborbital, another element that needed to be developed for Buran-T besides the GTK were the upper stages to place payloads into orbit. One of these was a modification of the Proton rocket’s Blok-DM upper stage. Having a diameter of 3.7 m and a length of 5.56 m, it was to carry between 11 and 15 tons of LOX/kerosene. Its engine was to have a thrust of up to 8.5 tons and have the capability of being ignited up to seven times. It could also act as a retro- and correction stage for long-duration deep-space missions, in which case it would need a special propellant-cooling system.

The other upper stage, known as 14S40 or Smerch (“Tornado”), was to use liquid oxygen and hydrogen. It was only one in a family of cryogenic upper stages that the KB Salyut design bureau (part of NPO Energiya in the 1980s) had been tasked to develop by a government decree in December 1984. The others were Shtorm (“Gale”) for the Proton rocket, Vikhr (“Whirlwind”) for Groza (an Energiya with two strap – ons), and the 11K37 (a “heavy Zenit’’) and Vezuviy (“Vesuvius”) for Vulkan (an Energiya with eight strap-ons). Manufacturing was to take place at the Krasnoyarsk Machine Building Factory.

By late 1985 KB Salyut came up with a plan for using the cryogenic 11D56M engine, an improved version of the 11D56 engine developed back in the 1960s by KB Khimmash for the N-1 rocket. With its thrust of 7.1 tons and specific impulse of 461 s, it was well suited for KB Salyut’s own Proton, but did not meet the requirements that NPO Energiya had laid down for Smerch. In July 1988 Minister of General Machine

Building Vitaliy Doguzhiyev directed NPO Energiya and its Volga Branch to propose its own upper stages for Buran-T and Vulkan. NPO Energiya set its sights on the RO-95, an open-cycle LOX/LH2 engine under development at KBKhA in Voronezh.

With a thrust of 10 tons and a specific impulse of 475 s, the RO-95 outperformed the 11D56M by a considerable margin and was also optimized for use in Vulkan’s Vezuviy upper stage. Unlike the upper stage that KB Salyut had proposed, NPO Energiya’s Smerch had the LOX tank on top, which was more favorable in terms of center-of-gravity requirements and also made it easier to ignite the engine in zero gravity. In this configuration Smerch was 5.5 m wide and 16 m long with a propellant mass of up to 70 tons. The engine could be re-ignited up to ten times. Technical requirements for the RO-95 were sent to KBKhA in December 1988 and test firings of the engine were expected to begin in 1991-1992. Yet in February 1989 Doguzhiyev seems to have turned around his earlier decision by limiting work on cryogenic upper – stage engines to KB Khimmash’s 11D56M, arguing that there were no payloads in the pipeline for Buran-T and Vulkan that justified the development of an entirely new engine.

Initially, three upper-stage configurations were studied for Buran-T: only the Blok-DM derived stage for low-orbiting payloads (up to 1,000 km), only the Smerch for payloads destined for geostationary orbit, lunar libration points, and lunar orbit, and the two stages combined for lunar-landing missions, flights to Mars and Jupiter. Payload capacity would have been about 88 tons to low Earth orbit, 18-19 tons to geostationary orbit, 21.5-23 tons into lunar orbit, 9-10 tons to the lunar surface, and 10-13 tons into Martian orbit [57].

Now operated by RKK Energiya, the MIK OK Buran processing building has once again become a very active facility, processing hardware for both manned and unmanned programs. The dilapidated building was even given a fresh coat of paint in 2004, making it look as good as new, at least from a distance.

In the early 1990s, bay 104, where orbiters used to undergo electrical tests, was modified to enable final launch preparations of Proton-launched space station modules, which before that used to be processed in the Proton area of the cosmodrome. The first module to be processed here was Mir’s Spektr module in 1995, followed later by Priroda and the Russian ISS modules Zarya and Zvezda. At least one more Russian ISS module, the Multipurpose Laboratory Module (the original Zarya back-up vehicle), will pass through the MIK OK before its expected launch in 2009. After processing is completed, the modules are trans­ported to the MIK 92A-50 Proton assembly building for integration with the launch vehicle.

Bay 104 now also houses the processing area for Soyuz and Progress vehicles, which used to be situated in the old MIK-2A assembly building in the center of the cosmodrome. This is where the vehicles are placed after arriving from RKK Energiya for final outfitting and testing. Four vehicles can be prepared here simultaneously. Less than two weeks before a Soyuz launch, the prime and back-up crews go to bay 104 to perform fit checks aboard the spacecraft, giving them a chance to see how the flight vehicle is configured. Once tests are completed, the spacecraft are sent to Site 31 of the cosmodrome for fueling and then return to the MIK OK for installation of the launch vehicle adapter and payload shroud. Next the combination is moved to the nearby MIK RN low bay 1 for mating with the Soyuz launch vehicle. The first vehicles to undergo launch preparations in Bay 104 were Progress M-40 and Soyuz TM-29 in late 1998. Also used for Soyuz/Progress preparations are bays 103 and 105. Bay 105 continues to serve as an anechoic chamber for compatibility tests of radio systems, and bay 103, the former Buran assembly bay, now houses a vacuum chamber.

Finally, bay 103 and bay 102 (the former a thermal protection system bay) are used to prepare RKK Energiya’s Blok-DM upper stages and Yamal communications satellites. Iridium satellites were processed here as well [80].

In 1993 the Russian Space Agency initiated a research and development program called Oryol (“Eagle”) to devise a strategy for the development of reusable space transportation systems in the 21st century. While the program was mainly aimed at technology development, several design bureaus were also invited to work out poss­ible schemes for a Russian Aerospace Plane (RAKS), although it is hardly likely the intention was to actually build one. The focus was both on SSTO and two-stage-to – orbit (TSTO) concepts.

Schemes for vertically launched, partially reusable TSTO systems were devised by RKK Energiya, KB Salyut (which became part of the Khrunichev Center in 1993), and TsNIImash. All these revolved around the use of winged flyback boosters and expendable second stages, capable of placing about 25 tons into low 51° inclination orbits. All the concepts relied on the use of LOX/LH2 engines, with the RD-0120 figuring prominently in three of the four schemes. The payloads could either be traditional satellites placed under a payload fairing or spaceplanes. Primarily intended for space station support, these Reusable Orbital Ships (MOK) would have an expendable instrument and cargo compartment.

Attention was also given to air-launched systems. It would seem that NPO Molniya got some funding under Oryol to continue work on its air-launched MAKS versions. Meanwhile, the Mikoyan bureau studied a fully reusable TSTO system called MiGAKS, consisting of a turbojet/ramjet powered hypersonic carrier aircraft and a spaceplane with rocket engines. The aircraft would propel the spaceplane to Mach 6 before releasing it and would then return either to its home base or to a runway downrange. The Mikoyan bureau studied hypersonic planes burning a combination of kerosene and hydrogen (total take-off mass 420 tons) or hydrogen alone (take-off mass 350 tons). Payload capacity to a low 51° inclination orbit was 12.3 tons for the first version and 10 tons for the second version.

In the SSTO area, the Mikoyan bureau came up with an unmanned spaceplane called MiG-2000. Weighing 300 tons at take-off, the 54 m long vehicle would be accelerated to Mach 0.8 by a liquid-fueled rocket sled, with ramjets propelling it to Mach 5 before rocket engines burning LOX and subcooled liquid hydrogen took

over to boost it to orbit. Payload capacity was 9 tons to a low 51° inclination orbit and cross-range capability was up to 3,000 km.

RKK Energiya proposed a 1,400-ton SSTO spaceplane called MKR (Reusable Space Rocket Plane). This would be launched on its own vertically, powered by seven tripropellant LOX/LH2/kerosene engines with a sea-level thrust of 250 tons each. Externally resembling a Buran orbiter, most of the mid and aft fuselage was occupied by propellant tanks, leaving room only for a 8.0 x 4.5 m payload bay. Payload capacity was anywhere from 10 to 18 tons to low 51° orbits, depending on whether the vehicle was manned (maximum crew of three) or unmanned. Missions would last no longer than seven days. Cross-range capability was 2,000 km [22].

There was other SSTO research in the 1990s apparently not funded under Oryol. Khrunichev’s KB Salyut worked on a vertical take-off/horizontal landing system reminiscent of America’s VentureStar, and the Makeyev bureau designed a vertical take-off/vertical landing system called Korona similar to the American DC-X and its Delta Clipper prototype [23]. Finally, NPO Molniya did paper studies of sled – launched SSTOs (VKS-R) as well as vertical take-off/horizontal landing systems (VKS-O) [24].

Perhaps the most exotic SSTO concept was Ajax, originally conceived in the late 1980s by Vladimir L. Frayshtadt at the holding concern Leninets in Leningrad, but not made public until the 1990s. The basic principle is that Ajax turns the kinetic energy produced by the incoming airflow into chemical energy and power. Hydrocarbon fuel circulating under the skin is decomposed into several constituents by aerodynamic heating (“endothermic fuel conversion”) and routed to a so-called magnetohydrodynamics (MHD) propulsion system, consisting of an MHD genera­tor, a scramjet, and an MHD accelerator. The MHD generator extracts energy and thereby slows down the airflow before it enters the combustion chamber, circum­venting the problems associated with mixing fuel and air at high Mach numbers.

Subsequently, the extracted energy is re-injected into the system by the MHD accel­erator (located behind the combustion chamber) which speeds up the airflow. Another novelty on Ajax is the creation of plasma at the leading and trailing edges of its body to ensure a smoother air flow across the fuselage [25].

The Oryol program was finished in 2001. The general conclusion was that the best way to go forward in the near future was to develop partially reusable TSTO systems with flyback boosters and conventional rocket engines. Including space – planes as a means of satellite deployment in TSTO systems would only be effective if they could lower launch costs by 5-7 times compared with expendable launch vehicles and if they could be made five times more reliable, both of which are unattainable goals at the present time. Therefore, preference was given to TSTO systems with conventional satellite deployment techniques. The partially reusable Angara rockets using the Baykal flyback stage were seen as a first step in that direction. SSTOs were considered worth developing only if their dry mass could be made 30 percent lower than that of systems like the Space Shuttle or Energiya – Buran, which is unrealistic for the time being. The most promising SSTO designs were considered to be vertical take-off/horizontal landing systems [26].

Under the Federal Space Program for 2001-2005 Oryol was followed by another research program called Grif (“Vulture”), focusing among other things on studies of new, heat-resistant materials, construction materials, and air-breathing engines [27]. The latest Federal Space Program (2006-2015) only envisages the development of a partially reusable TSTO system with a flyback booster, an indication that SSTO has been shelved for many years to come. A tender to develop the TSTO is to be held in 2009 and the system is supposed to be fielded in 2016, although this is subject to further review. Payload capacity should be 25-35 tons to low orbit and launch costs should be reduced 1.5 times by avoiding the expenditures associated with clearing first-stage impact zones.

A possible contender is the RN-35, a TSTO system designed by the Keldysh Research Center in 2001-2003. Having a payload capacity of 35 tons, it would have a winged flyback booster burning liquid oxygen and methane. This may eventually be followed around 2030 by the RN-70, a similar system with a 70-ton payload capacity. There may be cooperation with the French CNES space agency under a program known as Ural [28]. At any rate, given the conclusions of the Oryol studies, it is unlikely that spaceplanes will be part of the TSTO program.

Ever since the death of Korolyov in 1966, TsKBEM had been run by Vasiliy Mishin, a long-time associate of Korolyov. Eight years on, his position had been significantly weakened by the deadly accidents in the Soyuz and Salyut programs and the repeated failures of the N-1 rocket. Although Mishin was a talented engineer and the seeds for

many of those failures had been sown under Korolyov’s leadership, he clearly lacked the authority and the managerial qualities of his predecessor. His predilection for alcohol had not done his reputation any good either. On 17 May 1974 the Soviet leadership decided it was time to act. Mishin was sacked as general designer of TsKBEM and replaced by Valentin P. Glushko, who until that time had headed the KB Energomash organization, the main design bureau for Soviet rocket engines. With Glushko’s arrival, Energomash was absorbed by TsKBEM, which was renamed NPO Energiya.

One of Glushko’s first orders was to suspend all work on the N-1 rocket and the associated L-3 and MOK projects. After the back-to-back failures in 1969, two more N-1 flights in June 1971 and November 1972 had ended in first-stage failures. However, Glushko’s move had as much to do with past rivalries as with sound engineering reasons. Energomash had been excluded from taking part in the N-1’s development because of a major disagreement between Korolyov and Glushko in the early 1960s over the types of engines and propellants to be used and the relations between the two men had remained strained until Korolyov’s death. Therefore, Glushko’s assignment to the top job at Korolyov’s former bastion was an ironic twist of fate, to say the least.

After his arrival at NPO Energiya, Glushko started a one-year effort to map out a future course for the Soviet manned space program. Apart from the ongoing Soyuz/ Salyut effort, there was no consensus on what that future should be. For this purpose NPO Energiya was reorganized into five departments. Aside from the Apollo-Soyuz and Salyut departments, headed by Konstantin Bushuyev and Yuriy Semyonov, respectively, Glushko established a department that would study various concepts for a reusable space transportation system akin to the American Space Shuttle. This was headed by Igor Sadovskiy. A fourth department, overseen by Ivan Prudnikov, would focus on the establishment of a lunar base, and a fifth department, led by Yakob Kolyako, would study a new generation of heavy-lift launch vehicles called RLA to replace the N-1. The new structure was approved on 28 June 1974 by MOM minister Sergey Afanasyev [7].

A LUNAR BASE OR A SHUTTLE?

Although studies of reusable space transportation systems were underway by the time TsKBEM was reorganized into NPO Energiya in May 1974, at that time they were certainly not considered the main priority. Glushko himself was opposed to the development of a Space Shuttle equivalent and in the first week following his appointment had even disbanded Burdakov’s shuttle team, only to reinstate it on the insistence of Igor Sadovskiy, who in turn was placed in charge of the shuttle department [8].

Glushko feared the shuttle program would jeapordize plans to establish a per­manent base on the Moon. Despite the suspension of the N-1 project, the manned lunar program was not dead. Not only was a lunar base considered an appropriate response to the short-duration Apollo flights, for Glushko personally it would be a sweet revenge on Korolyov’s star-crossed N-1/L-3 effort. Initially at least, Glushko had the support of Dmitriy Ustinov, who in his capacity of Communist Party Secretary for Defense Matters served as the de facto head of the Soviet space program from 1965 until 1976. A long-time ally of Glushko, Ustinov may very well have been instrumental in getting him the top job at NPO Energiya. Opening a top meeting at NPO Energiya on 13 August 1974, Ustinov said:

“In recent days the Politburo has held serious discussions on our space problems … It was said at the Politburo that, taking into account the successful landings of the Americans, the task of conquering the Moon remains especially important for us. Whatever task we carry out, this will remain our main general task, but in a new [form].’’ [9]

Even though work on a lunar base was already underway at the KBOM design bureau of Vladimir Barmin, Prudnikov’s department at NPO Energiya set to work. By the end of 1974 it completed preliminary plans for a permanently manned lunar base called Zvezda (“Star”) that would see three-man crews working on the surface of the Moon for up to a year before being changed out. The plan included a Lunar Expedition Ship (LEK) to transport the crews to the Moon and a lunar base consisting of a Lab-Hab Module, a Lab-Factory Module, a manned lunar rover, and a small nuclear power plant to provide power to the various elements of the base. The scheme required multiple launches of a massive rocket in the RLA family capable of putting 230 tons into low Earth orbit, 60 tons into lunar orbit, and 22 tons on the lunar surface [10].

By the first half of 1975 NPO Energiya had devised a so-called “Integrated Rocket and Space Programme’’, which included the plans for the RLA rocket family, the Zvezda lunar base, and reusable spacecraft. It was submitted for approval to the Ministry of General Machine Building and the Ministry of Defense. Apparently, the hope was that all these elements would be approved. However, by this time Zvezda, Glushko’s pet project, stood little chance of surviving. Not surprisingly, the lunar base received no support whatsoever from the military. Neither did it receive the blessing of the Academy of Sciences (in the person of Keldysh) and Ustinov’s initial support had dwindled for a variety of reasons [11]. Clearly, many had been sobered up by the fact that the estimated price tag for the project was 100 billion rubles [12]. In fact, very few people apart from Glushko himself seem to have believed in the ambitious plans he outlined after becoming chief of NPO Energiya.

By 1976 the design of the RLA-130 had evolved such that it was becoming an ever more daunting task to unify the design of the strap-on boosters and the first stage of

the 11K77 medium-lift launch vehicle. For one, the strap-ons would now carry the 740-ton thrust RD-170, providing much more muscle than what was needed for the 11K77 first stage and shifting the latter’s impact zone in Kazakhstan [64]. However, the biggest problem was that because of their location in the RLA-130 stack the strap-ons experienced high bending loads, which made it necessary to make the tank walls tougher than was necessary for the 11K77. NPO Energiya proposed to con­struct the tanks out of a lightweight, but strong 1201 aluminum alloy that was also used for the core stage tanks, but KB Yuzhnoye’s manufacturing facility did not possess the welding technology needed to build such tanks [65].

At one point the differences seemed so irreconcilable that KB Yuzhnoye chief designer Vladimir Utkin was on the verge of ending his co-operation with NPO Energiya. His bureau was simply not up to the task of building two fundamentally different rocket stages. To Glushko the idea of using the 11K77 first stage as a test bed for the strap-ons was so critical that Yuzhnoye’s withdrawal jeopardized the very existence of the RLA-130. There simply was no other organization that could build the strap-ons. Fortunately, Glushko and Utkin were able to hammer out a com­promise during an exhausting two-day meeting at KB Yuzhnoye in Dnepropetrovsk [66]. The tank walls would be made of an aluminum-magnesium alloy with a waffle – grid structure and would be somewhat thinner on the 11K77. Other than that, the 11K77 first stage would use virtually the same engines and propellant feed systems. In the end, the commonality between the stages was about 70-75 percent.

On 16 March 1976 the Soviet Communist Party and government issued another decree, which gave KB Yuzhnoye the final go-ahead for the development of the 11K77 rocket. Coming just about a month after the decree on the Soviet shuttle, it seems to have formalized agreements that had been made in the previous months on unifying the 11K77 and RLA-130 designs. That same month Yuzhnoye gave Energomash the required parameters for the first and second-stage engines. The first-stage engine, the RD-171, was almost identical to the RD-170 of the RLA-130 with the exception that it could be gimballed in only one axis rather than two.

The second stage was to be powered by the single-chamber RD-120 LOX/ kerosene engine. Its development was assigned to Energomash rather than KBKhA

in Voronezh, with the latter getting the RD-0120 in return. One of the reasons was that the development of this engine should get underway as soon as possible so that engineers might learn the necessary lessons for the larger RD-170/171. In support of its test program for the heavy-thrust first-stage engine, Energomash had already developed a prototype LOX/kerosene engine that had characteristics very similar to those required for the Zenit second stage. This was based on the RD-268 nitrogen tetroxide/UDMH engine, which was being serially produced for the first stage of Yuzhnoye’s MR-UR-100 ICBM. Finally, the second stage was also to carry a four – chamber RD-8 vernier engine for thrust vector control, developed in-house at KB Yuzhnoye [67].

The preliminary design (“draft plan”) for the 11K77 was finished in February 1977. The March 1976 decree had called for a maiden flight in the second quarter of 1979, but numerous problems (mainly with the first-stage engine) would eventually delay that until April 1985 (see Chapter 6).

Buran had a so-called Airframe Pressurization and Ventilation System (SNVP). Similar to the Orbiter’s Purge, Vent, and Drain System, it served several purposes:

to maintain proper temperature and moisture levels in the vehicle’s unpressurized compartments on the ground, to cool the aluminum skin after landing, to vent the unpressurized compartments during ascent and re-entry, and to prevent big differ­ences in pressure between the mid and aft fuselage. The SNVP consisted of fourteen inward opening 510 x 200 mm vent doors, six on either side of the mid fuselage and one on either side of the aft fuselage, and a series of air ducts with non-return valves. Half of the vent doors were equipped with filters.

Thermal control of Buran’s unpressurized compartments was particularly important in the harsh climate of the Baykonur cosmodrome. The SNVP was used for this purpose whenever the vehicle was not in the hangar, whether it be on the pad or during transportation from the assembly building to the pad or from the runway back to the hangar. After circulating through the vehicle the air was released via the vent doors. Another task of the SNVP on the ground was to prevent accumulation of hazardous gases inside the vehicle.

By cooling Buran’s aluminum skin after landing, the SNVP played an important role in ensuring the ship’s reusability. The aluminum alloy from which the bulk of Buran’s airframe was made (D16) could not be repeatedly exposed to temperatures higher than +150/160°, even though Buran would face the same kind of heating during re-entry as the Shuttle (whose skin can withstand +175°C). Therefore, it was necessary to extensively ventilate the vehicle with cool air (no warmer than +10°C)

after landing. Ground equipment was hooked up to Buran’s SNVP for this purpose within 8 minutes after touchdown.

The SNVP’s vent doors were primarily used to equalize inside and outside pressure during launch and landing. During launch the doors were opened between altitudes of 200 m and 35 km. In orbit the ventilation doors situated in the mid fuselage were again briefly opened prior to payload bay door opening to dump any residual pressure that might affect the operation of the payload bay door latches. Those same vent doors were opened during the return phase at an altitude of 22.5 km. The ones lacking filters were closed again at 400 m to prevent dust contamination of Buran’s interior. The doors in the aft fuselage remained open throughout the orbital phase of the mission. By creating a near-perfect vacuum in the aft fuselage, it became easier to maintain the liquid oxygen tank of Buran’s propulsion system at cryogenic temperatures.

The SNVP also allowed Buran’s internal compartments to be purged with nitrogen to minimize the fire hazard in both the mid and aft fuselage during the early stages of launch and the final phases of landing. At T — 40 minutes the airflow was stopped, after which the vehicle’s interior was purged with ground-supplied nitrogen until T — 5 minutes. Subsequently, the vent doors were closed to ensure that enough nitrogen remained inside the vehicle during the early phase of launch.

Prior to re-entry the aft fuselage doors were closed until landing, allowing the aft compartment to be purged with nitrogen from an altitude of 30 km. The nitrogen was stored in 15 tanks in the mid fuselage [15].

This measured range from an altitude of 40 km (about 400 km from the runway) all the way to touchdown. The on-board component of the RDS, known as 17M900, consisted of four redundant interrogators and four antennas, weighing a total of 85.5 kg. Up to an altitude of 4 km they sent paired pulses to six distance-measuring equipment units (DME) at Baykonur, which then transmitted paired pulses back to the orbiter on a different frequency. The time required for the round trip of this signal was then translated by the orbiter into distance to the transponder. The system indirectly also provided data on elevation and azimuth.

Three of the ground terminals were deployed off one end of the runway and the other three off the opposite end. One terminal in each set of three was located along the runway centerline, about 20 km away, and the other two were deployed on either side within 60 km from the runway. Each of the six terminals had a unique coded

reply, allowing Buran’s Biser-4 computers to select and use distance measurements from the three terminals whose positions provided the best accuracy. Each of the three selected terminals was interrogated 60 times per second, nearly four times the rate for standard en route distance-measuring equipment used in aviation at the time. Each terminal transmitted via two antennas, one horizontally polarized and the other vertically polarized, enabling Buran to receive a strong signal over its circularly polarized antennas despite extreme pitch or roll maneuvers. When the orbiter reached an altitude of 4 km, the RDS interrogators switched to distance-measuring units on either end of the runway that had the same precision as a microwave landing system. The RDS has no equivalent on the US Space Shuttle Orbiter.