Category Energiya-Buran

Although NPO Energiya’s favored design was by now a delta-wing vehicle virtually identical in shape to the US Space Shuttle Orbiter, the Mikoyan engineers that had been transferred to NPO Molniya had their own ideas. In February 1976 Yuriy

Blokhin, the head of DPKO Raduga’s space design bureau in Dubna, had already written a report for the Central Committee stating that the 75 million rubles invested in Spiral were the only practical basis in the USSR for the creation of a reusable space transportation system [60]. However, by this time the designers were bound by the payload requirements and mission goals for the shuttle spelled out by the February 1976 party/government decree and the small air-launched Spiral was way below specifications. Therefore, the former Mikoyan engineers hatched a plan to build a much enlarged version of the Spiral lifting body capable of carrying the required amount of payload and launch that with the new heavy-lift rocket [61].

In the weeks after the decree was issued the “big Spiral’’ (code-named “305-1”) and NPO Energiya’s delta-wing orbiter (“305-2”) were the subject of a comparative analysis carried out by NPO Energiya, NPO Molniya, TsAGI, and TsNIIMash. There seems to have been division within the newly created NPO Molniya itself, with the former Mikoyan people strongly lobbying for the Spiral-based system and the Myasishchev branch supporting the delta-wing orbiter. In fact, NPO Energiya designers had been consulting with Myasishchev’s specialists on the delta-wing design since 1974. The former Mikoyan engineers, backed by TsAGI, pointed to the significant experience accumulated over the past ten years in research on Spiral (BOR missions, wind tunnel tests, etc.), while the NPO Energiya people argued that copying the shape of the American vehicle could save at least two years, reasoning it made no sense “to re-invent the wheel’’. The whole matter turned into a fierce debate between Lozino-Lozinskiy and Sadovskiy, which was eventually put to rest by MAP minister Dementyev, who left the final decision to Glushko. Being no expert in aerodynamics, Glushko in turn delegated the decision to the Council of Chief Designers, which by a simple majority of votes selected NPO Energiya’s delta-wing vehicle on 11 June 1976 [62]. However, one source claims the final decision was not made until late 1978 [63].

The January 1976 OK-92 plan was taken as the basis for the orbiter’s design, but a couple more changes were made. The solid-fuel emergency separation motor was removed from the orbiter and the hypergolic propellants for the orbital propulsion system were replaced by LOX/vintin, with all the engines drawing their propellant from common tanks. The two D-30KP turbojet engines were replaced by a pair of Lyulka AL-31 turbojet engines, already under development at the time for use on the Sukhoy Su-27 fighter. They were mounted in special niches on either side of the vertical stabilizer and covered with thermal protection material. The engines were eventually installed on a full-scale test model of Buran (BTS-002) used for approach and landing tests in 1985-1988, which also had two additional afterburner-equipped versions of the engine to take off on its own power. However, only months before the maiden space mission of Buran, it was decided not to install the AL-31 engines (see Chapter 7).

For regions exposed to temperatures of up to 370° Buran had multiple-layer, square­shaped panels of flexible insulation, similar to the Felt Reusable Surface Insulation (FRSI) employed by the Shuttle. Known as ATM-19PKP, the material was similar to that used for the felt pads under the tiles and was applied to the upper payload bay doors, portions of the upper wing surfaces, and portions of the mid fuselage.

Carbon-carbon

The areas where Buran incurred the highest heating during re-entry (up to 1,650°C) were the nosecap and the leading edges of the wings. As on the Orbiter, these parts were covered with a reinforced carbon-carbon (RCC) material. Until 1978 efforts focused on an RCC material known as KUPVM-BS, but despite its high thermal resistance and strength, it turned out to be too difficult to use. Eventually, the choice fell on a material called GRAVIMOL, an acronym reflecting the names of the three organizations that developed it (NII Grafit, VIAM, and NPO Molniya). There were some small differences in the composition of the RCC material used in the nosecap and the wing leading edges (GRAVIMOL-B in the wing leading edges). The material’s density was 1.85 g/cm3. The RCC had a coating of molybdenum disilicide to prevent oxidation. As on the Shuttle Orbiter, each wing leading edge was covered with 22 RCC panels.

Thermal barriers

Flexible thermal seals protected the vehicle in between certain types of thermal protection material and also in areas containing movable parts. Brush-type seals covered small gaps between sections of the payload bay doors and also in the vertical stabilizer, body flap, and elevons. Seals made of quartz fibers protected areas between the thermal protection system and various doors and hatches. Seals composed of silicon carbide fibers were used in areas exposed to extremely high temperatures such as the gaps between the RCC panels on the wing leading edges and areas where the RCC material bordered on the tiles. An ablative material capable of withstanding temperatures up to +1,800°C covered the gaps between the elevons [14].

The orbiter’s primary navigational aids were three so-called “gyro-stabilized platforms” (GSPs). Comparable with the Shuttle’s three Inertial Measurement Units (IMUs), they provided inertial attitude and velocity data to the guidance, navigation, and control software. Just like the IMUs, the GSPs were isolated from rotations by four gimbals and used a set of gyros to maintain the platform’s inertial orientation. Attitude data was provided by so-called resolvers and velocity data by a set of accelerometers. Whereas the Shuttle’s IMUs are mounted on a navigation base forward of the flight deck control and display panels, Buran’s GSPs were installed in a small module in the payload bay, attached to the outer wall of the aft flight deck just under the aft-looking window.

Since Energiya’s own GSPs were much more accurately aligned prior to launch than those of Buran, the orbiter primarily relied on data from Energiya’s navigation sensors for accurate azimuth alignment during launch. Buran’s on-board computers continuously compared navigation data originating from Energiya with that obtained by the orbiter’s own sensors and then made the necessary corrections.

In-orbit alignment of the GSPs was conducted with star trackers and a radio altimeter, attached to the right and left sides of the GSP module. While the Shuttle Orbiter also uses star trackers for IMU alignment, the radio altimeter was unique to Buran. The star trackers, concentrated in a so-called Stellar-Solar Instrument (ZSP), measured the line-of-sight vector to at least two stars. Using this information, the on-board computers calculated the orientation between these stars and the orbiter to determine the vehicle’s attitude. Comparison of this attitude with the attitude measured by the GSP provided the correction factor necessary to null the GSP error. The ZSP had a door which was opened after opening of the payload bay doors.

The radio altimeter (Vertical Radio Altimeter or RVV), providing local vertical measurements, acted as a back-up to the star trackers for GSP alignment and thereby increased the reliability of the navigation system. GSP re-alignment required at least two measurements of the local vertical, ideally with an interval of a quarter orbit. However, the RVV only provided reliable information over bodies of water, making it necessary to accurately time the measurements. Shortly after a GSP alignment session, the RVV could also be used for autonomous navigation, updating the vehicle’s state vector. State vector updates were also performed with a Sunrise/Sunset Detection Instrument (PRZS), an optical device that compared the expected and actual moments of sunset and sunrise as seen from the orbiter. This was also unique to Buran.

When orientation was lost completely (e. g., due to a computer failure) and could not be restored with the star trackers or radio altimeter, Buran could rely on an infrared horizon sensor system (Local Vertical Sensor or PMV) reacting to the Earth’s radiation to re-establish orientation to a point where the radio altimeter could take over. Not available on the Space Shuttle, this system could be used during unmanned missions.

Navigational aids to be used for proximity and docking operations in orbit were a radar system known as the Mutual Measurement System (SBI), the Cosmonaut Visual Rangefinder (VDK), and the Visual Navigation Measurement System (NIVS). The latter was permanently mounted on a special porthole in the aft flight deck and had to be manually aligned with the GSP module by the crew.

Just like the Shuttle Orbiter, Buran had three-axis rate gyro assemblies and body – mounted accelerometers to measure angular rates and accelerations for use in flight control algorithms [23].

For entry the accuracy of the GSP-derived state vector was insufficient to guide the spacecraft to a pinpoint landing. Therefore, data from other navigation sensors were blended into the state vector at different phases of entry to provide the necessary accuracy. Because of the requirement to perform unmanned landings, Buran had a more elaborate system of landing navigation aids than the Space Shuttle Orbiter:

A rescue option unique to the Soviet space program was the ability to send a Soyuz spacecraft to an incapacitated orbiter. That plan could have been set in motion in any scenario where Buran would have been unable to return to Earth, such as a propulsion system failure, major damage to the thermal protection system, etc. In any given situation, it would have taken the Soyuz at least several days to reach Buran, making it necessary for the crew to conserve power and consumables until the rescue craft arrived. After crew evacuation, Buran could then either have been sent on a destructive re-entry over unpopulated regions or—if deemed feasible—safely brought back to Earth unmanned.

Of course, a Soyuz rescue could only have been conducted in certain well-defined circumstances. First, it assumed that Buran was equipped with an APAS docking adapter. Second, the ship needed to have at least some level of control (navigation systems and steering thrusters) enabling it to be positioned for the active Soyuz vehicle to dock with it. Third, the crew should have numbered no more than two cosmonauts, since the three-man Soyuz had to be launched with a “rescue com­mander” to assist the stranded pilots in boarding the Soyuz. In the late 1980s/early 1990s the Russians had a cadre of “rescue commanders’’ for emergency flights to Mir who could quite easily have been cross-trained for Buran rescue missions. The Soyuz rescue scenario seems to have been worked out specifically for the early two-man test flights.

Even if Buran carried more than two crew members, a Soyuz rescue was not entirely out of the question, at least if the ship was on a space station mission. Fuel reserves permitting, the Soyuz could have evacuated all crew members by making repeated flights between the stricken Buran and the space station. This was only in the very unlikely event that the vehicle had a problem preventing it from landing and could not reach the station or return to it. Otherwise, the Buran crew could simply

have stayed aboard the space station until rescue arrived. Taking into account the fact that the bulk of Buran missions would have been to Mir and Mir-2, this is a luxury that most Buran cosmonauts would have had long before NASA even began thinking about the “safe haven” concept in the wake of the 2003 Columbia accident.

The Russians took the Soyuz rescue option very seriously. They were even planning to simulate it during the second mission, in which the ship would have launched and landed unmanned but would have been temporarily boarded by a Soyuz crew while in orbit (see Chapter 5). If Buran had ever flown its two-man test flights, a Soyuz vehicle would very probably have been on stand-by at the Baykonur cosmodrome to come to the rescue. The early Buran pilots would have needed some limited Soyuz training, even if the Soyuz would be piloted by a rescue commander. This is probably one of the reasons Buran pilots Igor Volk and Anatoliy Levchenko made Soyuz flights in 1984 and 1987, although the primary goal of these flights was to test their ability to fly aircraft after a week in zero gravity (see Chapter 5).

Of course, it should be understood that, while all these abort scenarios were theoretically possible, it is far from certain that all of the situations described above would have been survivable. Much would have depended on the exact circumstances. Also, at least several of them were only feasible with a limited number of crew members on board (two to four). On the whole, though, it can be said that Buran crews would have stood a better chance of surviving in-flight emergencies than any Space Shuttle crew to date [32].

This test stand is located outside not far from the MIK OK and was used for test firings of the ODU propulsion system (both maneuvering engines and thrusters) and the Auxiliary Power Units. Although these systems also underwent non-integrated tests at other locations in the Soviet Union, the Russians deemed it necessary (unlike

NASA) to conduct test firings with these systems installed on the vehicle. Such tests would not only have been conducted prior to the maiden mission of a new orbiter, but also after each mission, mainly to clean the internal plumbing. The test stand had its own propellant fueling systems [10].

Rocket Assembly and Test Facility (MIK RN/MIK 112)

The Energiya assembly building (11P591) was originally built for the assembly of the N-1 rocket in the 1960s. Measuring 190 x 240 m, the building accommodates five parallel bays, three high bays (heights given between 47 and 60 m) and two low bays (heights given between 27 and 30 m). Externally, the building hasn’t changed much since the N-1 days, but because of the fundamentally different design concepts of the N-1 and Energiya, the inside had to undergo a complete overhaul. Low bay 1 was used for assembly of the strap-on boosters, low bay 2 and high bay 3 for integration of the core stage, and high bays 4 and 5 for final assembly of the entire Energiya vehicle and mating with Buran. Bay 1 was operated by NPO Energiya’s ZEM factory, and the other bays by a branch of the Progress factory.

The strap-ons arrived at the cosmodrome in several sections: the modular part from Yuzhnoye in Dnepropetrovsk and the aft skirt, nose section, parachute containers, and other elements from ZEM in Kaliningrad. The core stage similarly required much work in the MIK RN, where engineers had to attach the tail section with its RD-0120 engines to the hydrogen tank and subsequently attach the hydrogen tank to the oxygen tank/intertank structure.

The final assembly process began with one left and one right strap-on being placed on a special stand, after which the core stage was inserted in between them. Subsequently, the remaining two strap-ons were placed on top of the others and in the final step Buran was lowered onto the core stage with a special crane. The rocket was attached to a mating unit (Blok-Ya) that connected pneumatic, hydraulic, and electrical systems on the launch vehicle with the launch complex. Measuring 20.25 x 11.5m and weighing 150 tons, the Blok-Ya was a massive struc­ture, containing 1,123 pipes with a total length of about 12km. Finally, a crawler transporter parked outside the building was placed under the structure to begin the roll-out [11].

Internal documents obtained by the authors show that there was fierce debate between LII/MAP and NPO Energiya/MOM in the 1980s over crewing for the first manned missions. It was all very reminiscent of similar disagreements between the Korolyov design bureau and the Air Force over crewing for Voskhod and Soyuz missions in the 1960s. The documents show that the Council of Chief Designers decided on 26 January 1983 to assign only LII test pilots to the first two manned Buran missions, but that NPO Energiya disagreed with the plan in September 1983, putting forward its own flight engineers to occupy the second seat. By the autumn of 1985 NPO Energiya had mustered enough support to secure a joint decision from MOM, MAP, and the Ministry of Defense on the formation of four preliminary crews for the first two manned flights:

Somewhat later the pairings were changed as follows:

Volk Levchenko Stankyavichus Shchukin

Ivanchenkov Strekalov Balandin Krikalyov

Another source claims the crews initially were Volk-Ivanchenkov, Levchenko – Strekalov, Stankyavichus-Balandin, and Shchukin-Lebedev, with Lebedev being replaced by Krikalyov in 1986 [45].

On 6 December 1985 the Military Industrial Commission (VPK) went along with the plan, ordering formation of final crews by December 1986 based on the training results obtained by then. The first phase of training for the NPO Energiya engineers would see theoretical, simulator, and aircraft training. LII demanded that the flight engineers fly a total of 398 hours on five different aircraft, but in the end five engineers (Ivanchenkov, Strekalov, Balandin, Krikalyov, and Lebedev) accumulated just 11 hours of flying time during 26 flights on four aircraft in November 1986. In June 1987 Volk and Ivanchenkov flew 10 different landing profiles on the PDST simulator at NPO Molniya, which according to Volk’s official protocol showed that the engineers would not be able to safely land Buran in case of an emergency.

Based on the preliminary results of the training program, both MAP and the Air Force recommended in 1987 only to fly experienced LII test pilots on the first Buran missions. With their limited aircraft training, the engineers were not even considered capable of flying in the co-pilot seat of the Tu-154LL training aircraft or the BTS-002. Although the prime landing mode even for manned missions was automatic, MAP and the Air Force argued that the crew would have to take manual control if they were diverted to an emergency landing site not equipped with the necessary navigation equipment to support hands-off landings. Moreover, it was felt that the second crew member needed flying skills equal to those of the commander in order to deal with various off-nominal scenarios. Among those were malfunctions in the commander’s flight displays and control panels and a situation where the commander was partially disabled by space motion sickness. A joint LII/TsPK research program called “Dilemma” had shown that the engineers would not be able to render the necessary assistance to the commander in case of these and other emergencies.

Predictably, NPO Energiya and MOM, citing the December 1985 VPK decision, ignored the conclusions of MAP and the Air Force and insisted on a continued training program for the engineers, including simulated flights on the PDST simu­lator and real flights on the Tu-154LL and BTS-002. One of the arguments in favor of including a flight engineer on the first manned flight (then scheduled to be mission 1K2) was that it would be a conservative 3-day flight, with most systems operating in the automatic mode. On the other hand, LII used the same argument to claim that the limited engineering tasks planned for the flight might just as well be performed by a test pilot. At any rate, the Council of Chief Designers ordered on 23 March 1988 to draw up a new training schedule for the NPO Energiya engineers, but it looks as if NPO Energiya pursued its plans with less vigor as the months went on. The launch date for the first manned mission kept slipping and the exact flight plan remained vague, complicating the formation of a training program. Moreover, by the end of the 1980s virtually all of the NPO Energiya flight engineers involved in Buran had

either been reassigned to the Mir program or left, with only Ivanchenkov remaining until 1992 [46].

In later interviews the LII pilots did not hide their opposition to Energiya’s push to include engineers in the first crews. Volk said that at one point he went to Minister of General Machine Building Oleg Baklanov, asking him what the use of flying engineers was. According to Volk, Baklanov quoted Glushko as saying that “they would keep an eye on the devices.’’ Losing his temper in a subsequent argument with Glushko over the crew assignments, Volk told the chief designer: “Then let Strekalov and Ivanchenkov fly! And if there is a crash or whatever, then of course the news will be all over the world’’ [47].

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].