Category Energiya-Buran

The RLA’s LOX/kerosene engines were to be the first such engines developed under Glushko in almost 15 years. In the mid to late 1950s Glushko had supervised the development of the RD-107/RD-108 engines for the R-7 missile and derived launch vehicles (sea-level thrust around 80 tons) and the RD-111 for the R-9ICBM (sea-level thrust 144 tons). All of these were four-chamber LOX/kerosene engines using an open combustion cycle, in which the gases used to drive the turbopumps are vented overboard. This system is also known in Russian terminology as “liquid-liquid”, because both the fuel and the oxidizer are injected into the combustion chamber in a liquid state. However, the development of the RD-111 was plagued by serious prob­lems, including high-frequency oscillations in the combustion chamber, intermittent combustion, and the need to protect the chambers and nozzle walls from overheating.

In the early 1960s Glushko turned his attention to closed-cycle engines, in which the gases used for driving the turbines are routed to the combustion chamber to take part in the combustion process. This, together with the increased chamber pressure, produced much higher specific impulses than had been obtained earlier. One of the propellants entered the combustion chamber in a liquid form and the other in a gaseous form (which is why this system is also called the “gas-liquid” system by the Russians). Given the painful experience with the RD-111, Glushko was wary of using LOX/kerosene for these even more powerful engines. Instead, he decided to con-

centrate on storable propellants based on unsymmetrical dimethyl hydrazine (UDMH), which he had already mastered while developing open-cycle engines for the R-12, R-14, and R-16 missiles. In fact, Glushko’s preference for storable over cryogenic propellants can be traced back all the way to his years as a rocket pioneer at the GDL and RNII rocket research institutes in the 1930s.

All this had dire implications for the N-1 program. Glushko’s reluctance to build closed-cycle LOX/kerosene engines and Korolyov’s refusal to use the highly toxic

storable propellants for the rocket effectively ended the cooperation between the two chief designers. It forced Korolyov to rely on LOX/kerosene engines of the much less experienced OKB-276 Kuznetsov design bureau in Kuybyshev (which actually were of the closed-cycle type).

For the remainder of the 1960s, Glushko was mainly engaged in building closed – cycle engines with storable propellants for a variety of missiles and launch vehicles of the Chelomey and Yangel bureaus. Except for the R-7 derived rockets, all Soviet space launch vehicles that were operational around the turn of the decade (Kosmos, Tsiklon, Proton) were powered by such engines. They had been derived from nuclear missiles, which traditionally use storable propellants to enable them to be launched at short notice.

Energomash didn’t end its boycott on LOX/kerosene engines until the late 1960s, by which time enough experience had been gained with the closed-cycle combustion principle for engineers to feel confident enough to apply it in powerful LOX/kerosene engines. An opportunity to build such an engine arose in 1969, when the Chelomey bureau drew up plans for a mammoth rocket called UR-700M, intended to send Soviet cosmonauts to Mars. One version of the rocket that Chelomey looked into would have 600-ton thrust LOX/kerosene engines in the first and second stages. In 1970 Glushko’s engineers worked out plans for such an engine called RD-116 or 11D120, which presumably was a modified LOX/kerosene version of the single­chamber RD-270, a hypergolic engine earlier planned for Chelomey’s (unflown) UR-700 Moon rocket [31]. Although the UR-700M remained no more than a fantasy, Energomash was reportedly also ordered to investigate the possibility of using the same engine on the first stage of the N-1, which had suffered two launch failures in 1969. A small cluster of RD-116 engines would be enough to replace the N – 1’s thirty NK-15 first-stage engines [32].

In the end the idea was dropped because it would also have implied a radical redesign of the N-1 rocket. However, it does seem to have whetted Glushko’s appetite to continue studies of such engines, the more so because a new policy was emerging in the early 1970s to abandon storable propellants in favor of cryogenic and hydro­carbon propellants in new, dedicated space launch vehicles.

As a result, work on high-thrust LOX/kerosene engines at Energomash resumed in earnest in 1973. The studies focused not only on standard kerosene, but also an advanced synthetic hydrocarbon fuel known as tsiklin or sintin. Based on furfural and propylene, it had a higher specific impulse than ordinary kerosene, but was also much more expensive.

In the course of 1973 proposals were presented for single-chamber, two-chamber, and four-chamber versions of a 500+ ton thrust LOX/kerosene engine. There was serious debate between the proponents of the single and four-chamber versions, which both had their advantages and drawbacks. A key meeting at Energomash in the second half of 1973 opted for the four-chamber version. After all, Energomash had had experience with multi-chamber engines since the 1950s. Furthermore, there had been numerous problems with the development of the 640-ton single-chamber RD-270 for the UR-700. Finally, by using four smaller combustion chambers it would be easier to test them by modifying test models of existing combustion chambers for storable propellants. The meeting also approved a so-called “modular design” for the engines, making it possible to use them in a standardized fleet of rockets [33].

Still, all these were no more than internal decisions within Energomash that didn’t stand much chance of being implemented until the bureau merged with TsKBEM to form NPO Energiya in May 1974 and Glushko got the opportunity to advance his RLA idea. But even at this stage there was no consensus what the LOX/kerosene engines should look like. Some of the disagreements centered around such things as the pressure in the combustion chamber and the type of combustion cycle. Some claimed the pressure in the combustion chamber shouldn’t exceed 200 atmospheres, making the engine more reliable. However, a lower pressure translates into bigger combustion chambers and less payload, and the compromise reached was to have a pressure of 250 atmospheres. Others felt the engine should use a fuel – rich combustion cycle, lowering the risk of turbopump burn-throughs. That was countered by the argument that an oxidizer-rich preburner engine is more efficient and easier to reuse because it leaves behind less soot residue [34].

There was also more fundamental debate over the thrust of the engine. Some felt that the task of building a four-chamber engine with a single, powerful turbopump assembly was too challenging and instead preferred single-chamber engines in the 150-ton thrust range with smaller, individual turbopumps. In other words, rather than having a handful of very powerful engines, it would be better to install a large number of low-thrust engines [35]. One concern with the high-thrust engines was that they would expose the rocket to serious vibrations in case of a sudden emergency shutdown, making it necessary to strengthen the rocket’s structure and lower its payload capacity [36].

Bearing in mind these two schools of thought, two design departments at Energomash got down to studying engines in two thrust classes. Department 729 focused on engines ranging in thrust from 112.5 to 263.5 tons: the RD-128, RD-129, and RD-124 for the first stage of the RLA family and the RD-125, RD-126, and RD-127 for the second and third stages. Department 728 initially concentrated on an engine with a phenomenal thrust of 1,003 tons (the RD-150), but then scaled back its ambitions to a 600-ton thrust engine called RD-123 [37]. This is the engine that finally got selected in 1975 for use in the first stage of the Soviet space shuttle stack and the progenitor of the eventually developed RD-170. A determining factor in this choice must have been the negative experience of flying many low-thrust engines on the first stage of the N-1. Moreover, Glushko must have feared that if the choice did fall on the low-thrust engines, there would have been attempts to de-mothball the Kuznetsov bureau’s N-1 engines rather than introduce his new LOX/kerosene engines. However, the debate would flare up again in the early 1980s when the RD-170 was plagued by serious development problems (see Chapter 6).

ENERGIYA CORE STAGE

The core stage was designed jointly by NPO Energiya in Kaliningrad and its Volga Branch in Kuybyshev, with manufacturing taking place at the Progress factory in Kuybyshev. With a length of 58.7 m and a maximum diameter of 7.75 m, it was the backbone of the Energiya-Buran stack, providing structural support for attachment with the strap-on boosters and orbiter. It was very similar in design to the Space Shuttle’s External Tank (ET), with the exception of a tail section housing the engine compartment. The core stage was made up of an upper liquid oxygen (LOX) tank, an unpressurized intertank, a lower liquid hydrogen (LH2) tank, and a tail section containing the four RD-0120 engines. The wet mass was 776 tons.

Both the LOX and LH2 tanks were made of a 1201 aluminum alloy. The 552m3 LOX tank could hold about 600 tons of oxidizer. It consisted of a forward ogive section (itself made up of three sections), a cylindrical section (itself made up of two sections), and a spherical aft dome. All sections were welded together. The tank had anti-slosh baffles to dampen any motions of the LOX that might throw the rocket off course. The LOX feed line exited the LOX tank at a 7° angle to the longitudinal axis of the tank to facilitate oxidizer supply during the final moments of the launch. It ran to the tail section right through the LH2 tank. This is a major difference with the Space Shuttle External Tank’s LOX feed line, which emerges from the ET’s intertank area to convey the oxidizer to the aft right-hand ET-Orbiter disconnect umbilical. The LOX feed system had gas accumulators to dampen longitudinal oscillations (“pogo’’). These were located in the lower part of the LOX feed line in the bottom of the LH2 tank and also in the engines’ turbopump inlet ducts.

The intertank was the structural connection joining the liquid hydrogen and oxygen tanks. Flanges were affixed at the bottom and top of the intertank so the two tanks could be attached to it. Also installed in the intertank was the instrumenta­tion for the core stage’s flight control system. Prior to launch the intertank was

Energiya core stage 93

purged with nitrogen gas to prevent the build-up of moisture and explosive mixtures of hydrogen and oxygen gas.

The 1,523m3 LH2 tank, which could hold about 100 tons of liquid hydrogen, consisted of spherical aft and forward domes and a large cylindrical section. The tank walls were machined in a waffle-grid pattern, something not employed in the ET hydrogen tank until the introduction of the Super Lightweight External Tank in 1998. Although LH2 is so light that sloshing does not induce significant forces, Energiya’s LH2 tank, unlike that of the ET, did have anti-slosh baffles.

Just like the Shuttle’s ET, the Energiya core stage was covered with a combina­tion of polyurethane spray-on foam insulation (Ripor-2N, PPU-17) and ablative material (PPU-306) for thermal insulation and thermal protection. This reduced boil-off losses during the countdown, maintained the propellants at the proper temperatures for normal engine operation, limited ice formation on the outer surface, and protected the core stage against the flames from the strap-on boosters’ separation motors. The original plan not to apply thermal insulation to the upper part of the LOX tank was abandoned due to fears that ice might break off from that part of the core stage and damage the orbiter’s fragile heat shield. Various non-destructive methods were used to test these materials after they were applied: electric methods to check their thickness, radioisotope techniques for density, and acoustic methods to detect debonding.

Shedding of tank insulation became a big issue in the US after the February 2003 Columbia accident, caused by a piece of foam insulation breaking off the tank and inflicting lethal damage to one of the Reinforced Carbon-Carbon panels on the Shuttle’s left wing. Russian sources do not mention whether Energiya’s foam insula­tion was less or more prone to shedding simply because this was not a matter of major concern in the pre-Columbia days. Moreover, any foam loss that might have occurred on the two Energiya launches in 1987 and 1988 would have been virtually impossible to photographically document because the first launch took place in darkness and the second in poor weather conditions. Tile damage suffered by Buran on its sole mission has usually been attributed to ice falling off the core stage and the launch pad and not to foam impacts.

Electric power for the core stage was provided by four simultaneously operating turbogenerators driven by air, nitrogen, hydrogen, and helium gas. In order to simplify the design and reduce mass, common plumbing was used for all four gases. Each generator weighed 330 kg and provided 24kWt of power.

The cryogenic propellants were loaded at lower temperatures than on the Space Shuttle (—255°C vs. —253°C for the liquid hydrogen and —195°C vs. —182°C for the liquid oxygen). This made the propellant denser and also significantly reduced boil – off losses. Techniques for subcooling liquid oxygen were pioneered by the Russians with the R-9 missile in the early 1960s, but Energiya marked the first use of subcooled liquid hydrogen. The liquid hydrogen was subcooled by passing it through two double-walled cooling devices in which tubular heat exchangers were immersed in a bath of liquid hydrogen boiling at reduced pressure.

Loading of the core stage began several hours before launch with a slow-fill mode to condition the tanks. When the core stage was 2 percent full, the fueling process was

sped up to 19,000 liters per minute for the liquid oxygen and 45,000 liters per minute for the liquid hydrogen. This fast-fill mode continued until 98 percent of the pro­pellant was loaded. Topping off continued until T — 3m02s for the LOX tank and T — 1m52s for the LH2 tank.

After the start of fueling, electrically powered pumps in the main engines began to circulate the liquid hydrogen in the fuel tank through the four engines and back to the tank to chill down the liquid hydrogen lines, ensuring that the path was free of any gaseous hydrogen bubbles and was at the proper temperature for engine start. The LH2 was recirculated to the tank rather than returned to ground facilities because it loses a lot of pressure during the circulation process. The engines’ LOX lines were also thermally preconditioned, but the LOX used for this purpose was dumped overboard.

In the final minutes of the countdown the tanks were pressurized to maintain their structural integrity during launch, minimize the build-up of volatiles in the tanks, and to prevent cavitation of the main engine low-pressure boost pumps. Pre-launch pressurization was performed with ground-supplied helium and began at T — 2m23s for the LOX tank and T — 1m20s for the LH2 tank. After lift-off the LOX tank was pressurized with hot gaseous oxygen produced by heat exchangers in the main engines and the LH2 tank with gaseous hydrogen tapped from the turbines of the main engine LH2 boost pumps. At lift-off the LOX tank was pressurized to 2.6 atmospheres and the LH2 tank to 3.1 atmospheres. During launch the pressure in the LOX and LH2 tanks was maintained between 1.41-1.55 atmospheres and 2.25-2.39 atmospheres, respectively.

Each tank had a dual-function vent and relief valve at its forward end. It could be opened by ground-supplied helium before launch for venting or by excessive tank pressure for relief during launch. Excess hydrogen gas left the core stage via the intertank area, while excess oxygen gas was directly vented overboard [1].

Buran had a Water Supply System (SVO) that consisted of the Potable Water System (SPV), designed to provide drinking water to the crew, and the Process Water System (STV), intended to supply water to the thermal control and hydraulic systems.

The bulk of the potable water on Buran was to be produced as a byproduct of the fuel cells, which use oxygen and hydrogen to generate electrical power. Before ending up in one of two reservoirs inside the crew compartment (one prime, one back-up), the near-distilled water passed through a cleansing unit filled with hydrogen gas and then through another unit where it was enriched with silver ions. The water was extracted from the reservoirs via a manually operated pump and then passed through a cooling device or a heater. It could be used either for drinking or for preparing food. A 10-liter back-up supply of potable water was to be pumped into Buran before launch.

Process water was needed for the flash evaporators of the Thermal Control System and the hydraulic system. It was stored in four separate units containing four 25 liter tanks each, giving a total capacity of 400 liters. Since Buran needed this water for cooling during launch, some 370 liters were pumped into the tanks on the ground, with the fuel cells being capable of supplying an additional 30 liters during the final countdown and ascent. During on-orbit operations the STV collected additional water from the fuel cells, dumping overboard any excess supplies. The process water was distilled and saturated with silver ions. It was pushed out of the tanks with compressed air [18].

For satellite deployment missions Buran would have been equipped with an extend­able turntable that would first lift the payload out of the confines of the cargo bay. After deploying the payload’s appendages and checking all on-board systems, the satellite would then have been spun up and released with the help of springs.

Buran was also supposed to be outfitted with a robotic arm system to deploy and retrieve payloads. One of its primary tasks would have been to lift space station modules out of the vehicle’s cargo bay and attach them to available docking ports and also to provide a stable platform for spacewalking cosmonauts. Developed by the Central Scientific Research Institute of Robotic Technology and Technical Cyber­netics (TsNII RTK) in Leningrad, the so-called On-Board Manipulator System (SBM) was similar in design to the Shuttle’s Canadian-built Remote Manipulator System (RMS). Measuring 15m and weighing 360 kg, it had six joints and could lift a payload of up to 30 tons. Maximum translation speed was 30 cm per second without a payload and 10 cm per second with a payload. The SBM would be operated manually from a console in the aft flight deck with two joysticks, one to move the arm itself, and

the other to operate the grapple fixture. Three cameras, one on the wrist and two in the cargo bay, would have assisted in these operations. It was also possible to operate the arm automatically using software stored in the on-board computer. During unmanned missions the arm could even have been controlled from Mission Control via the on-board computer system. With the Shuttle never having been designed to fly unmanned, the RMS did not provide that capability, although the technique was later introduced for the International Space Station’s Remote Manipulator System (SSRMS), which was first remotely operated from the ground in March 2006.

The major difference with the RMS was that even on standard missions Buran would have carried two arms, one on the left, the other on the right longeron to provide more flexibility in loading/unloading operations or provide back-up cap­ability. Although provisions for two arms were incorporated in each Space Shuttle Orbiter, the idea of ever flying two RMS units on a single Orbiter was abandoned in the late 1990s. After the 2003 Columbia accident the remaining Shuttle Orbiters were equipped with a second arm known as the Orbiter Boom Sensor System, but this is solely intended to make camera surveys of RCC panels and heat shield tiles.

The SBM was not flown on Buran’s only mission in November 1988, but was supposed to be installed on the second flight vehicle for a docking mission with the

Mir space station. A working model of the arm was built and installed at TsNII RTK on a special test stand capable of simulating weightless conditions [26].

NPO Energiya’s major subcontractor for the Buran project was NPO Molniya, situated in Tushino in the northwest outskirts of Moscow. The organization was established on 24 February 1976 under the Ministry of the Aviation Industry by the merger of three existing organizations:

– MKB Burevestnik: set up in 1954 in Tushino as the design bureau aligned with Factory nr. 82, renamed the Tushino Machine Building Factory (TMZ) in 1963. The factory serially manufactured surface-to-air missiles and target drones. In 1966 the design bureau and TMZ became involved in the improve­ment and production of the Sukhoy design bureau’s T-4 supersonic bomber, the airframe of which was built with new titanium alloys using new auto­mated welding techniques. Burevestnik was headed from 1965 to 1986 by Aleksandr V. Potopalov.

– MKB Molniya: established in 1948 in Tushino as OKB-4 to design various types of helicopters, but in the early 1950s began specializing in air-to-air and air-to-surface missiles. Placed in charge of the organization in 1955 was Matus R. Bisnovat, who after his death in 1977 was replaced by G. I. Khokhlov.

– Experimental Machine Building Factory (EMZ): set up in 1966 by the merger of a branch of the Khrunichev factory and KB-90, which until then had been part of Branch nr. 1 of Chelomey’s OKB-52 design bureau. Branch nr. 1 was the former OKB-23 design bureau of Vladimir M. Myasishchev, which among other things had worked on the Buran cruise missile and various spaceplane projects, and was absorbed by OKB-52 in 1960. The Khrunichev branch and KB-90 were situated next to one another in the Moscow suburb of Zhukovskiy and had been responsible for modernizing aircraft built at Khrunichev and also performing test flights from a nearby airfield. Myasishchev, who had been placed in charge of TsAGI after OKB-23’s merger with Chelomey’s bureau, was appointed head of EMZ in June 1967. The bureau was involved in the design of several heavy and high-altitude aircraft. Following Myasishchev’s death in 1978, the organization was headed by Valentin A. Fedotov (1979-1986) and Valeriy K. Novikov (1986-2006).

Although several people from the former OKB-23 were apparently transferred to EMZ, none of the three organizations had been involved in any of the numerous spaceplane projects studied in the Soviet Union in the 1960s. Therefore, over 100 Spiral veterans were transferred to NPO Molniya from MMZ Zenit (the Mikoyan design bureau) and its former space branch in Dubna, which in 1972 had merged with MKB Raduga (another former branch of Mikoyan’s bureau) to form DPKO Raduga. These people occupied leading positions within NPO Molniya, first and foremost Gleb Lozino-Lozinskiy, who became general designer and director of the organization. He was replaced as general director by Aleksandr V. Bashilov in 1994, but remained in the post of general designer until his death in 2001 at age 91. Also invited to work for NPO Molniya were specialists from Branch 1 of Chelomey’s bureau, NPO Energiya, TsNIIMash, and several other organizations.

NPO Molniya was responsible for the “aircraft-related” elements of Buran: the fuselage, crew compartment, aerodynamic surfaces, landing gear, and hydraulic systems. In addition to that, it oversaw the development of the payload bay doors, the thermal protection system, the power distribution system, and the pressurization and ventilation system. The bulk of the work on Buran within NPO Molniya seems to have been assigned to EMZ, which was involved in the development of the crew module shell, manual flight controls, environmental and thermal control systems, the emergency escape system, and the turbojet engines needed for the approach and

landing tests with the BTS-002 Buran model. EMZ was also in charge of modifying the VM-T aircraft for ferrying Buran and elements of the Energiya rocket to Baykonur. Potopalov’s Burevestnik team was responsible for developing the vehicle’s primary load-bearing structure.

Even after being absorbed by NPO Molniya, the individual design bureaus that constituted the organization did not all abandon their former lines of work. EMZ continued to develop a variety of aircraft, and MKB Molniya continued to work on air-to-air missiles, although most specialists involved in this work (including Khokhlov) were transferred to another design bureau (MKB Vympel) in the early 1980s.

Production of the airframe took place at the Tushino Machine Building Factory (TMZ), which had built a wide variety of aircraft, surface-to-air missiles, and target

missiles since its establishment in 1932, briefly branching out into trams and trolley­buses after the war. Key aircraft manufactured at TMZ were Sukhoy’s T-4 from 1966 to 1974 and Mikoyan’s MiG-23 from 1975 to 1982. Aside from assembling the airframe and all airplane-related elements of Buran, TMZ was also responsible for installing heat-resistant tiles on Buran’s aluminum skin. TMZ received components for the airframe from more than 450 aviation enterprises across the Soviet Union.

Although TMZ was an existing facility, most buildings needed for the con­struction of Buran seem to have been built from scratch. The most important ones were building nr. 110 (general assembly), nr. 111 (final assembly + production and installation of heat-resistant tiles), nr. 112 (assembly of the crew cabin), and nr. 112a (pressure and strength tests of the crew cabin).

TMZ never delivered flight-ready orbiters, mainly because the VM-T carrier aircraft were not powerful enough to transport fully-equipped orbiters to the Baykonur cosmodrome. Final outfitting was carried out at the cosmodrome’s Buran assembly building by engineers of both ZEM and TMZ. Directors of TMZ during the Buran years were I. K. Zverev (1974-1982) and Suren G. Arutyunov (1982-1999). NPO Molniya also had a so-called “Experimental Factory’’ that among other things built various test stands for Buran (such as the PRSO and PDST landing simulators) and manufactured the Auxiliary Power Units.

One problem in transporting Buran to the launch site was that there was no suitable airfield in the vicinity of TMZ. Therefore, the orbiter had to be transported from Tushino (in the northwest outskirts of Moscow) to Zhukovskiy (southeast of Moscow, some 20 km from the outer ring road around the city). First, a special transportation device moved the orbiter through the streets of Tushino to the banks of the Moscow River. Several streets in the Moscow suburb had to be widened to give the vehicle with its 24 m wingspan enough clearance. The vertical stabilizer was removed for the entire trip from Tushino to Baykonur. Subsequently, the spacecraft was placed on a special barge equipped with ballast tanks, increasing its draught

sufficiently for it to pass under the bridges of the Moscow River. The barge then transported Buran to Zhukovskiy, floating right through the heart of the nation’s capital. Most of these transports took place when the Energiya-Buran program was still a state secret, which is why the orbiter was hidden from view by a huge cover that didn’t betray its true shape [3].

Linking the various facilities was an impressive network of roads and railways, some left over from the N-1 days, others built specifically for Energiya-Buran. Twelve meter wide roads connected the MIK OK with the landing facility, the MIK RN, the test-firing stand, and the MZK. Buran was transported with its landing gear retracted on a special 126-ton, 58.8 m long platform with 32 wheels that was pulled by a truck. Maximum speed with the vehicle mounted on top was 10 km/h.

In keeping with Soviet tradition, the Energiya-Buran stack was assembled and rolled out horizontally and then erected after arriving at the launch pad. The transportation device used for this was a giant crawler transporter (TUA) left over from the N-l days and built by the Novokramatorskiy Machine Building Factory in the Donetsk region (Ukraine). The transporter weighed 2,756 tons (without the stack), measured 56.3 x 90.3 m and was 2l.2m high. It was towed by four 100 horse­power diesel locomotives, moving at a maximum speed of 5 km/h over rail tracks separated 18 m apart. There were two TUA transporters, parked outside high bays 4 and 5 of the MIK RN. The MIK RN was linked by railway with the MZK, the two Energiya-Buran launch pads, and the UKSS [17].

After the cancellation of the Energiya-Buran program in l993, some of the facilities were mothballed and left to rust, but others have since been modified for new programs (see Chapter 8).

For most rocket, satellite, and spacecraft programs, the Soviet philosophy was to limit ground testing to the bare minimum and “fly the bird and see how it behaves”, no matter how many test flights were required before declaring it operational. For Energiya-Buran the Russians could hardly afford to do the same, if only because of the astronomical cost of the system and the serious implications of losing one or several vehicles in a small fleet of precious reusable spacecraft. Moreover, the Energiya-Buran system represented a leap in technology the likes of which had not been seen in the Soviet space program. It featured the country’s first reusable spacecraft (and a big one at that), the world’s most powerful liquid-fuel rocket engine (the RD-170), the first big domestic-built cryogenic engine (the RD-0120), the use of a vast array of new materials, and so on. Finally, the N-1 debacle, at least partly attributable to a lack of ground testing (particularly of the first stage), was firmly etched in everyone’s memories and a sure sign of the need to approach things differently when the next program of comparable proportions came along.

Therefore, for Energiya-Buran, the Russians had no choice but to shift the emphasis from in-flight to ground-based testing, requiring a major investment in infrastructure and hardware. Although the Russians undoubtedly benefited from more than seven years of US experience with Space Shuttle missions before Buran was finally launched, they clearly left no stone unturned when it came to testing their hardware, even for systems that were very similar to those flown on the Shuttle. In fact, in many respects the Energiya-Buran test program was more exten­sive than the Shuttle’s. Still, even that didn’t stop the Russians from sticking to their tradition of flying a piloted vehicle unmanned on its first mission, unlike NASA, which for the first time in its history put a crew on a first-flight vehicle with Columbia in 1981.

Rather than rely heavily on computer modeling, the Russians built at least seven full-scale test articles of Buran to investigate a variety of manufacturing, assembly, and flying quality characteristics as well as handling procedures. A similar approach was followed for space stations and their modules. By contrast, NASA built just two full-scale Orbiters for test purposes—namely, Enterprise (OV-101) and Structural Test Article 099 (later turned into OV-099 Challenger).

The seven full-scale vehicles were:

– OK-M (serial nr. 001): a full-scale model for structural tests at NPO Mol – niya. It mainly served as a test bed for the 002 vehicle used in the approach and landing tests. It had the same mass characteristics as the real vehicle, carrying mass models of on-board equipment. Later, it was supposed to be used for underwater EVA training in a hydrotank facility at Star City, but it was rebuilt as a tourist attraction and delivered by barge to Gorkiy Park in Moscow in 1993, where it can still be seen today.

– OK-GLI (serial nr. 002): a full-scale model used for approach and landing tests in 1985-1988 (see pp. 297-309).

– OK-KS (serial nr. 003): a full-scale model for electric and software tests, delivered to NPO Energiya in August 1983. Also used for electromagnetic interference tests. OK-KS served as a test bed to troubleshoot numerous problems that cropped up during the construction of the first flight vehicle. Various software programs for the maiden flight were tested on OK-KS.

– OK-ML1 (serial nr. 004): a full-scale model flown to Baykonur by the VM-T Atlant in December 1983 for preliminary fit checks of ground equipment in the Buran assembly building and on the runway. On one occasion it was mated with an Energiya for dynamic tests both at the UKSS and the left Energiya-Buran pad. For a while it had mock-up turbojet engines installed on either side of the vertical stabilizer.

– OK-TVA (serial number 005): a model for thermal, acoustic, and static vibration tests at TsAGI. To facilitate testing, OK-TVA was not assembled as a single vehicle, but split into several real-size sections that could be tested individually: a forward fuselage with crew cabin, mid and aft fuselage, two wings, a vertical stabilizer, elevons, a body flap, a nosecap, and several sections of the leading edges of the wings. The components were covered with standard thermal protection material, among other things to see whether that would be affected by slight deformations in the underlying aluminum skin.

Thermal and static vibration tests took place in the TPVK-1 vacuum chamber. It was 13.5m in diameter and 30 m long and exposed components to temperatures ranging from — 150°C (using a liquid nitrogen cooling system) to +1,500°C (using 10,000 quartz lamps with a total capacity of

13.0 kWt). The test rig could apply 8,000 kN of force horizontally and

2.0 kN vertically and took the airframe to 90 percent of design load limits. Acoustic tests were carried out in the RK-1500 acoustic chamber. With a floor space of 1,500m2, it was equipped with 16 sound generators that subjected the components to 162 dB sound levels at frequencies of 50 to

2.0 Hz.

– OK-TVI (serial nr. 006): a model for thermal vacuum tests at Nllkhimmash. This consisted of a mid and aft fuselage, a vertical stabilizer, and payload bay doors with radiator panels. Some sources also mention a forward fuselage with crew cabin, although that is not seen in photographs and must therefore have been tested individually. The fuselage sections were equipped with Buran’s thermal control system to see whether that could deal with the temperature extremes in space. The components were installed in the KVI thermal vacuum chamber. With a volume of 8,500 m3, this is the largest such facility in Europe.

– OK-MT/OK-ML2 (serial nr. 015): a full-scale model flown to Baykonur by the VM-T Atlant in August 1984 for fit checks of ground equipment at the cosmodrome. It was rolled out to the pad on several occasions and used among other things for crew boarding and evacuation exercises and for load tests of the ODU engine compartment and the Auxiliary Power Units. It was also transported to the runway for crew egress training and simulation of other post-landing activities.

In addition to the full-scale models, the Russians built several crew modules for test purposes. The following have been mentioned by Russian sources, although it is not entirely clear if all were actually built or used:

– MK-KMS: crew module at NPO Energiya equipped with operational con­trol, display, and computer systems and also incorporating an airlock and docking module. A visual display system simulated the outside environment during all phases of the flight. MK-KMS was intended for training crews and Mission Control personnel. It had the same communication links with Mission Control in Kaliningrad as the ones available to Buran during an actual flight.

– MK-M: a Buran crew module placed in a vacuum chamber (VU-1000) for tests of the life support systems and medical support systems (presumably located at Myasishchev’s EMZ). It also contained an airlock and a docking module. The crew module was placed vertically in the chamber, which was 10 m wide and 11m high. Crews entered and egressed the crew module via a small tunnel attached to the mid-deck side hatch. MK-M closely mimicked a real crew cabin, carrying standard life support and thermal control systems.

Any of those systems located outside the crew cabin were also installed in the chamber in roughly the same position with respect to the crew cabin as in a real orbiter.

The cabin carried mock-ups of equipment not related to the life support system. MK-M allowed crew members to wear Strizh pressure suits that could be immediately pressurized in case of a leak. The water delivered to the crew compartment was produced in actual Buran fuel cells. It is not clear if the test stand was ever used for crew training. The plan was eventually to turn it into a so-called ground-based “analog” of vehicles in orbit, among other things to facilitate troubleshooting activities.

– MK-1KA: a crew module with nose section mounted vertically on a turntable to practice crew evacuation from the vehicle.

– MK-KB: a crew module containing mock-ups of equipment needed for the 002 vehicle.

– MK-GN: a crew module placed in a hydrolab for EVA training.

– MK-KB. E: a crew module for electrical tests, later integrated into the OK-KS vehicle.

– MK-KB. U: a crew module to study the placement of equipment and crew work stations in the cabin [15].

None of these preparatory activities were reported by the Soviet media as they happened. Although Buran was no longer a state secret, Soviet space officials adopted a carefully limited posture concerning their plans. As the new policy of openness came into effect, some space officials and cosmonauts had begun confirming the existence of a shuttle in interviews and informal conversations in the mid-1980s. The official disclosure of the Soviet shuttle was left to Glavkosmos, an organization often described in the West as a Soviet equivalent to NASA, although it was actually the international relations arm of the Ministry of General Machine Building. Speak­ing at a Moscow press conference on 8 April 1987, Glavkosmos official Stepan Bogodyazh finally acknowledged that the Soviet Union was developing a reusable spacecraft and would announce the launch in advance. Bogodyazh’s statement was confirmed on 13 May 1987, when the TASS news agency reported the imminent launch of the first Energiya rocket and added it would be used in the future to orbit reusable spacecraft. In January 1988 Glavkosmos chief Aleksandr Dunayev told another Moscow news conference the first Soviet shuttle would be launched soon. Two months later he said the mission was still expected shortly, although engineers were encountering problems daily. He also promised that (unlike the maiden Energiya launch) the shuttle launch would be broadcast live on Soviet television.

Despite these occasional statements, Soviet officials provided little if any tech­nical details on their shuttle system. All this changed with the release of a government decree in early July 1988 that officially declassified the Energiya-Buran program [39]. By the end of that month the newspaper Pravda published an in-depth article on the Energiya-Buran system by chief designer Boris Gubanov, who confirmed earlier statements that Buran’s first flight would be unmanned:

“The role of manned flights on such carriers is not yet fully clear, such is the opinion of many specialists. A blind imitation of air travel is not relevant here. Space technology has gone its own way. Automatic ships were the first to enter space and humans followed only later. In the future, space will mainly be the working field of automatic spacecraft and transportation systems. The role of humans will probably be linked to research and specific maintenance and repair work… Today’s task is to accomplish the landing of an orbital ship in auto­matic mode without the involvement of pilots, and later that of separate units and stages. Nowadays, automatic flights from take-off to touchdown are also performed with aircraft, such as the Tu-204.’’

Almost certainly, the flight had originally been timed to upstage the return to flight of the US Space Shuttle (mission STS-26), but the ODU problems and several other issues had thwarted those plans. However, unaware of those developments, Western media speculated the Soviet shuttle might still blast off before Discovery. On 20 September the Washington Times reported US spy satellites had photographed the Soviet shuttle on the pad earlier that month and that some US officials expected a launch within a week. This clearly was a mistake, because the stack had been inside the Energiya assembly building since late August. However, the newspaper also quoted Soviet space expert Saunders Kramer as saying the odds of that happening were all but zero. Kramer correctly stated the vehicle had been wheeled out to the pad in the spring and “then inexplicably removed”, attributing the delay to problems with the computer software [40].

On 29 September 1988 all eyes were turned to Cape Canaveral in Florida, where the Space Shuttle Discovery was poised to return America to space 2.5 years after the January 1986 Challenger disaster. Lift-off occurred at 15: 37 gmt, and eight minutes later Discovery safely entered orbit. However, the Russians were intent on stealing at least some of the thunder from NASA’s success, taking advantage of the occasion to finally unveil their counterpart of the Space Shuttle to the world. Television viewers around the Soviet Union were surprised when the evening news program Vremya opened by showing a shot of the Energiya-Buran stack on the launch pad (taken during the May-June pad tests). The name Buran, painted on the side of the vehicle, had been carefully retouched so as not to be visible to the television audience, although it had leaked to the West several years earlier. The picture was accompanied by a terse TASS statement saying preparations for the launch were underway and that the mission would be unmanned. The Buran lead story was followed by footage of a conversation between the orbiting Mir crew and East German leader Erich Honecker. Vremya completely downplayed the news from Cape Canaveral by show­ing a brief clip of the Discovery launch just before going off the air. Interestingly, the following day some Soviet newspapers published exactly the same photograph with the name Buran erased altogether.

The next comment on launch preparations came from LII lead test pilot Igor Volk. Speaking at a meeting of the Association of Space Explorers in Bulgaria in early October, he revealed that 23 October was the target date for the launch when he left the Soviet Union. The Soviet shuttle moved into the background again until 23 October, when the TASS news agency once again repeated that final launch preparations were underway and revealed that the orbiter was called Buran. That same day Vremya showed the first ever footage of Energiya-Buran, including spectacular shots inside the MZK, during the roll-out and on the launch pad.

Although Buran figured prominently in plans for both Mir and Mir-2, there are no indications it was ever supposed to replace traditional transportation systems such as Soyuz and Progress. The idea was that it would be used in parallel with those systems for missions requiring its unique capabilities, such as assembly of large structures, swapping out of modules and delivery and return of large pieces of equipment. While Buran could have made it possible to reduce the number of Soyuz and Progress missions, these vehicles would have continued to play a crucial role in Soviet space station operations. This also explains why the Russians never stopped improving Soyuz and Progress during the development of Buran.

In fact, the International Space Station (ISS) is now pretty much operated as the Russians had set out to do with Mir and Mir-2, being serviced by a combination of large shuttles and smaller capsule-type vehicles. The ISS itself is clear proof that it is impossible to operate a space station with large shuttle vehicles alone. Although such vehicles can deliver larger crews and more supplies than capsule-type spacecraft, it is not economically justified to use them for dedicated crew rotation and resupply missions. Ideally, these tasks should be combined with shuttle-unique assignments and not be seen as mission objectives in themselves.

The biggest problem with Shuttle/Buran-type vehicles is that they can only stay docked to a space station for several weeks at most until their consumables run out. Vehicles like Soyuz and Progress can be largely deactivated after docking to a station and remain attached to it for months on end. This means they are always available for reboost and refueling operations when needed and—crucially for crew safety—can always immediately return a resident crew back home if an emergency situation arises. NASA had originally planned to service Space Station Freedom solely with

the Space Shuttle and leave crews on board in between Shuttle missions. Only after the 1986 Challenger disaster did it dawn on the agency that it would be dangerous to have crews on the station without a lifeboat attached. NASA then found itself scrambling to find a US contractor capable of building a station lifeboat at short notice. Fortunately enough for NASA, political changes in the USSR allowed the agency to adopt Soyuz as a lifeboat for Freedom in 1992 and the vehicle continued to serve in that role as part of the ISS.

The simultaneous operation of large shuttles and capsules also provides redun­dancy. One vehicle can continue to service the station in case the other is grounded. This was vividly demonstrated by the 2003 Columbia accident, after which Soyuz and Progress vehicles served as a lifeline for the station. One can only imagine what things would have been like if both the Space Shuttle and Buran had been around for ISS operations. Having been built to the same specifications as the Shuttle, Buran could have continued ISS assembly work during the Shuttle’s standdown. Of course, this is no more than wishful thinking, because the very conditions that lay at the foundation of Buran’s downfall enabled the creation of the ISS.