Category Energiya-Buran

Although the Energiya-Buran program remained shrouded in secrecy for much of the 1980s, US intelligence specialists had a fairly good idea of the system’s character­istics and capabilities, mainly thanks to detailed American reconnaissance satellite images of both Baykonur and the Flight Research Institute (LII) in Zhukovskiy. The latter was identified in the intelligence literature as Ramenskoye, which is the name of LII’s airfield in Zhukovskiy and (confusingly) also of a neighboring town and railway station.

The first clear evidence for the existence of a large shuttle came in the late 1970s, when construction of the runway and launch pads at Baykonur got underway. The Energiya-Buran pads were identified as “Complex J’’ (the same code name given to the N-1 pads) and the UKSS pad as “Complex W’’. By 1982 spy satellites had even spotted the construction of the back-up runway in the Soviet Far East. [14].

The first public assessment of the system’s capabilities was given in Soviet Military Power 1983, published in early 1983. Since the first test models of Energiya were yet to be rolled out to the pad, analysts still had a poor understanding of the system’s configuration and capabilities. Drawings showed the Soviet shuttle mounted on an external tank with two rocket boosters, with the main engines apparently on the orbiter itself. The lift-off weight of the system was estimated to be just 1,500 tons compared with the NASA Shuttle lift-off weight of 2,220 tons. Combined with an estimated lift-off thrust of between 1,800 and 2,700 tons (compared with roughly 3,000 tons for the Shuttle), this translated into a staggering payload capacity of 60 tons, twice that of the Space Shuttle Orbiter. The Soviet shuttle was believed to have a substantially different wing design with an 80-degree sweep. The heavy-lift launch vehicle (HLLV) was depicted as a 95 m high core vehicle with three 35 m high liquid propellant boosters and a top-mounted payload with a maximum mass of between 130 and 150 tons [15].

By the middle of 1983 several events led to a much better understanding of the Soviet shuttle system. Spy satellites had acquired detailed images of a test orbiter sitting atop a VM-T carrier aircraft during tests earlier in the year and had also spotted an incident in which the pair accidentally skidded off the runway in March 1983. Moreover, the first test versions of Energiya had been rolled out of the assembly building in the first half of the year. A CIA National Intelligence Estimate in July 1983 now correctly concluded that the orbiter had a configuration very similar to that of the US Space Shuttle Orbiter and that the main engines were on the core rather than on the orbiter. The report was wrong in stating that the rocket had only two strap-on boosters and that the core was outfitted with “at least two and probably three engines”. This may have been related to the fact that the Energiya rolled out in May 1983 had only three nozzles installed on the core stage {see Chapter 6). The report referred to the spherical sections above the core stage nozzles as “pod-like

US Defense Department representation of Soviet shuttle on the pad. Illustration from Soviet Military Power 1986 (source: US Department of Defense).

objects” that were erroneously interpreted as part of a recovery system for the LOX/LH2 engines [16]. In Soviet Military Power 1984 lift-off weight and thrust were now estimated at 2,000 tons and 3,000 tons, respectively, resulting in an orbiter payload capacity of 30 tons. The HLLV was still expected to be a nearly 100 m high rocket with six or more strap-on boosters and a payload capacity of 150 tons, a configuration that was actually more reminiscent of the Vulkan rocket.

It was not until the 1986 edition that Soviet Military Power published a drawing of a 100-ton capacity HLLV where the orbiter was replaced by a side-mounted cargo pod. This was also the first edition that got the dimensions of the rocket/orbiter stack more or less right, although the first Energiya-Buran combination did not make its appearance on the Baykonur launch pads until summer/autumn of 1986, after the report had been published. The following year potential payloads for the cargo version of the rocket were said to be modules for large space stations, components for a manned or unmanned interplanetary mission, and even directed-energy ASAT and ballistic missile defense weapons.

Reconnaissance satellite images of Baykonur also gave some idea of how the testing proceeded. In 1984 and early 1985 the SL-X-16 (“Zenit”) medium-lift booster had been observed being alternately removed from and erected on the pad, suggesting Soviet dissatisfaction with the ground test results. This in turn had implications for

the HLLV/shuttle program, which used common engines. Apparently, the belief at this time was that the SL-X-16 was powered by liquid hydrogen/liquid oxygen engines and that these same engines were used both in the strap-ons and the core stage of the HLLV. The fact that no Energiya had yet been seen with an orbiter strapped to the side was also seen as an indication that the program was suffering delays [17]. When a test orbiter did finally undergo the first pad tests in August – October 1986, the news was reported only weeks later [18]. US reconnaissance assets apparently also picked up signs of the Energiya core stage test firings in the first half of 1986, but these were not openly reported until a year later [19].

Buran-related test activities were not always correctly interpreted, especially when the Soviet approach to testing was different than NASA’s. Just weeks before the first ground run of the BTS-002 atmospheric test bed at LII in late December 1984, Aviation Week correctly reported that approach and landing tests of the shuttle were imminent, but wrongly concluded that the vehicle would be dropped from the VM-T carrier aircraft in similar fashion to the test flights of Enterprise in 1977 [20]. In April 1986, by which time BTS-002 had performed numerous ground runs and two

landing tests, Aviation Week referred to reconnaissance photography showing jet engines mounted on either side of the tail, but still believed the vehicle was being dropped from the VM-T. The jet engines were thought to be on board only to test their ability to correct an orbiter’s flight path when returning from space and might or might not be lit prior to separation from the aircraft depending on test objectives [21].

Of course, the information that leaked out via Aviation Week did not necessarily reflect what the US intelligence community really knew. Other observers, taking into account the known capabilities of the VM-T, correctly concluded that it could hardly carry a full-size, full-weight orbiter to sufficient altitude for a safe free flight [22]. Aviation Week did not report the correct flight profile of the BTS-002 until late 1987 after having been informed by Soviet space officials at an international space congress in Moscow. The only mistake remaining was that the tests were said to take place at Baykonur [23].

Western observers had more to go on than just the intelligence community’s interpretation of reconnaissance satellite imagery. Pictures taken of Baykonur by civilian remote-sensing satellites such as the US Landsat and the French SPOT had sufficient resolution to show the construction work going on in support of the Energiya-Buran program. Unlike the spy satellite pictures, these were openly available to the public.

It is not clear how much information on the program leaked to the West through breaches in the Soviet censorship and security apparatus or via human intelligence. One piece of information that did slip through was that the name of the Soviet shuttle was Buran. The name first appeared in a 1983 CIA National Intelligence Estimate and also surfaced in several open Western publications the following years, well before the Russians officially announced it [24]. This information could not possibly have been gleaned from spy satellite photography, because the name was not on any of the test models and was not painted on the first flight vehicle until 1988. Actually, before 1988 Buran was not the name of a specific orbiter, but a generic name used by the Russians to refer to the combination of rocket and orbiter (see Chapter 2).

On 6 May 1989 the Energiya-Buran program was again on the agenda of the Defense Council, chaired by Gorbachov. Appearing before the Council, leaders of the Energiya-Buran program outlined future plans for the system, including the GK-199 mission, the creation of fully reusable versions of the Energiya rocket, and the development of derived launch vehicles such as Energiya-M, Groza, and Vulkan. While acknowledging the success of Buran’s mission and praising the work of the people involved, the Council expressed dissatisfaction with the progress made on devising payloads and missions for the Soviet shuttle. The Council also made some cost-cutting moves, ordering the number of operational shuttle vehicles to be reduced from five (as planned since 1977) to three and curtail Buran’s test flight program to just five missions by combining some of the objectives of the earlier planned missions. At the same time it called for speeding up work on Buran payloads and Energiya – derived launch vehicles.

The plan was now to fly Energiya 2L with the GK-199 payload in 1990, giving the team an extra opportunity to man-rate the rocket for future Buran missions. The second unmanned orbiter mission was now delayed to the first quarter of 1991 and apart from a docking with Mir would feature a link-up with a manned Soyuz “rescue vehicle’’ (see Chapter 5). This mission, designated 2K1 (the first flight of orbiter 2K) had already been approved by the Military Industrial Commission on 22 February 1989. The first manned Buran flight was now scheduled for the first half of 1992. LII internal planning documents drawn up around this time show the unmanned mission was scheduled for April/May 1991 and the manned flight for May 1992, with crew training to begin in December 1990. The decisions of the Council were consolidated by a government decree in June 1989, which laid out plans for the use of Buran until the year 2000 [5].

For cargo missions the orbiter would have been replaced by a so-called Cargo Transport Container (GTK or 14S70) that could house a variety of payloads. This configuration was known as Buran-T (T standing for “transport”) before the name Energiya was adopted in 1987. The interfaces between the rocket and the payload would have been virtually identical to those on Energiya-Buran. Two diameters were considered for the GTK—namely, 5.5 m and 6.7 m—with the final choice falling on the latter, which turned out to be the most favorable in terms of aerodynamic and other characteristics. The container was 42 m long and had an internal volume of about 1,000 m3. The two main sections of the container were to be jettisoned after the rocket passed through the thickest layers of the atmosphere. The GTK was not used on the maiden flight of Energiya with the Skif-DM/Polyus payload, which flew the launch profile unprotected, except for a shroud on the upper FSB section. Strictly speaking, this was not a standard Buran-T configuration [56].

The Energiya assembly building is now run by the Samara-based TsSKB/Progress organization. As mentioned earlier, the three high bays were rendered useless by the roof collapse in May 2002, which among other hardware destroyed the only flown Buran orbiter. In 2004 the Russian Space Agency earmarked funds to refurbish high Bay 3 for processing future satellites built by TsSKB/Progress, but there are no signs that any work is being done. No plans have been announced for repairing the other two high bays and these may be demolished. By the end of 2006 the debris from the roof collapse had reportedly still not been cleared.

Low bay 1 now houses the processing area for Soyuz launch vehicles flying from pad 5 (the “Gagarin pad”) on Site 1, which is now used for Soyuz and Progress launches to the International Space Station and also for occasional launches of civilian satellites built by TsSKB/Progress (Foton, Resurs). Soyuz rockets destined for the Gagarin pad used to be assembled in the old MIK-2B building in the center of the cosmodrome. Although the new assembly hall is much roomier than MIK-2B, it is much farther away from the Gagarin pad, making the roll-out procedure more cumbersome. The roll-out now takes about 2 hours, compared with 30 minutes in the old days. The first vehicle to be rolled out from the modified low bay 1 was Progress M1-10 in June 2003.

Low bay 2 was modified in the late 1990s to process payloads for Starsem, a Russian/European company founded in 1996 by Arianespace, EADS SPACE, TsSKB/Progress, and the Russian Space Agency to commercially market the Soyuz launch vehicle. There are three Starsem clean rooms here: a 286 m2 Payload Processing Facility (PPF) with two independent control rooms to permit parallel operations, a 285 m2 Hazardous Processing Facility (HPF) to fill satellites with toxic hypergolic propellants, and a 587 m2 Upper Composite Integration Facility (UCIF) for integration with the Fregat upper stage and upper fairing encapsulation. Mating of the upper composite with the first three stages of the Soyuz launch vehicle takes place in the Soyuz assembly building on Site 31 on the “right flank” of the cosmo­drome. Starsem exclusively flies from pad 6, situated on Site 31 [79].

Research on aerospace planes in the Soviet Union got a fresh impetus in the mid-1980s, presumably in response to similar work started in the US in 1982 at the Defense Advanced Research Projects Agency (DARPA) under the name Copper Canyon and then transferred to NASA and the Air Force as the National Aerospace Plane (NASP) in 1986. President Ronald Reagan mentioned the project in his State of the Union speech on 4 February 1986, calling it:

“a new Orient Express that could, by the end of the next decade, take off from Dulles Airport, accelerate up to 15 times the speed of sound, attaining low Earth orbit or flying to Tokyo within two hours.’’

Although touted by the Reagan Administration for its civilian commercial applica­tions and as a possible follow-on to the Space Shuttle for NASA, the 80-20 split of funding between the Air Force and NASA clearly indicates NASP was first and foremost a military program. The objective of the program was to develop a proto­type SSTO vehicle taking off with turbojets, then switching to hydrogen-fueled scramjets at subsonic and hypersonic speeds, with a LOX/LH2 rocket engine performing orbit insertion.

The go-ahead for the Soviet response came in two government decrees on 27 January and 19 July 1986, followed by the release of technical specifications by

the Ministry of Defense on 1 September 1986. Three organizations were tasked to come up with proposals: NPO Energiya, the Yakovlev bureau, and the Tupolev bureau. While nothing is known about the Yakovlev concept, NPO Energiya’s aero­space plane was a 71 m long vehicle with a wingspan of 42 m and a maximum height of 10 m. With a take-off mass of approximately 700 tons (dry mass 140 tons), the vehicle would use a combination of turbojets, scramjets, and rocket engines to reach orbit. It was designed for the deployment of payloads into low orbits (at least 25 tons into a 200 km, 51° orbit), servicing of orbital complexes, intercontinental passenger transport and also for military operations “in and from orbit’’. The project was headed by veteran designer Pavel Tsybin [20].

The project eventually selected for further development was the Tupolev bureau’s Tu-2000. Actually, the bureau was no newcomer to SSTO vehicles, having already performed low-priority studies of horizontal take-off and landing space – planes with a take-off mass of up to 300 tons in 1968-1971. Overall Tu-2000 was very similar in design to NASP, relying on the same combination of engines to go into orbit. It had a vertical stabilizer and small delta wings, with much of the lift provided by the flat-shaped underside of the fuselage. A huge hydrogen tank occupied most of the mid and aft fuselage and would feed both the scramjet and rocket engines. The oxygen tank for the rocket engine was located in the tail section.

The Tupolev bureau proposed to carry out the project in two stages. First, it would develop a 55-60 m long two-man suborbital demonstrator (Tu-2000A) to reach a maximum velocity of Mach 5/6 and an altitude of up to 30 km. With a take-off mass between 70 and 90 tons, the vehicle would be equipped with four turbojet engines, two scramjets, and two liquid-fuel rocket engines. Then the project would move on to an experimental 71 m long two-man orbital version with a take-off mass between 210 and 280 tons and six rather than four turbojet engines. Payload capacity was 6-10 tons to low orbits between 200 and 400 km. Unconfirmed reports suggest the Tupolev bureau also planned a long-range bomber (Tu-2000B) and a hypersonic passenger plane based on the Tu-2000 design.

By the early 1990s the Tupolev bureau had reportedly built a wing torque box made of a nickel alloy, elements of the fuselage, cryogenic fuel tanks, and composite fuel lines. Estimates made in 1995 showed that Tu-2000 related R&D would cost at least $5.29 billion, a high price-tag even if Russia had a healthy economy. Budget realities had also forced NASA and the Air Force to cancel NASP in 1993. Although low-level research on the Tu-2000 may have continued for several more years, this project obviously stands no chance of being realized any time soon [21].

Meanwhile, six Soviet military and civilian research institutes were tasked with performing a study of the Soviet Union’s future space transportation needs to help determine the need for a response to the Space Shuttle. These were TsNIIMash and NIITP (the Scientific Research Institute for Thermal Processes, the current Keldysh Research Centre) under MOM, TsAGI (the Central Aerohydrodynamics Institute) under MAP, TsNII-30 and TsNII-50 under the Ministry of Defense, and IKI (the Institute of Space Studies) under the Academy of Sciences. TsNIIMash was given the lead role.

Actually, the studies centered not solely on shuttles, but on a wide array of expendable and reusable launch vehicles that would provide the most economical access to space in the future. They also extended to various reusable space tugs and expendable upper stages with either liquid or nuclear rocket engines for interorbital maneuvers and deep-space missions. Four future directions were considered for the Soviet Union’s space transportation program:

• the continued use of expendable launch vehicles and spacecraft until the year 2000;

• the continued use of expendable launch vehicles, but with standardized satellites;

• the use of a reusable space transportation system capable of returning spacecraft back to Earth for servicing and subsequent reuse;

• the use of a reusable space transportation system capable of servicing and

repairing satellites in orbit.

As for reusable systems, the institutes explored two vehicle sizes, one able to accom­modate payloads of 30-40 tons (like the Space Shuttle) and another for payloads weighing 3-5 tons. Furthermore, two ways were studied of recovering the first stage, one involving the use of standard recovery techniques, the other requiring the use of reusable flyback boosters.

The six institutes presented their joint findings in June 1974. They concluded that the development of a reusable launch vehicle was only economically justified if the launch rate was very high, more particularly if the annual amount of cargo delivered to orbit would exceed 10,000 tons. However, it was stressed that much also depended on the vehicle’s capability of servicing satellites in orbit or returning them to Earth for repairs. The size of the spaceplane in itself would not determine its effectiveness and would have to depend on the mass and size of the payloads that needed to be launched or returned. Finally, it was recommended to perfect future reusable systems by developing first stages with air-breathing engines and eventually to introduce high-thrust nuclear engines for single-stage-to-orbit spaceplanes.

Basically, the conclusion was that a Space Shuttle type transportation system would not provide any major cost savings even if a relatively high launch rate was achieved and should be seen as nothing more than a first step towards developing more efficient transportation systems. However, the consensus was that if a reusable system were developed, preference should be given to a big shuttle akin to the American one [4].

On 27 December 1973, without awaiting the results of the studies, the VPK ordered three design bureaus to formulate so-called “technical proposals” for a reusable space transportation system. This is one of the first stages in a Soviet space project, in which various preliminary designs are worked out and compared in terms of their technical and economic feasibility. While the VPK order was significant in being the first official government-level decision on a Space Shuttle response, it was far from a commitment to build such a system, but merely an attempt to explore various vehicle configurations that might eventually lead to to a final decision later on. The three bureaus were MMZ Zenit (headed by Rostislav Belyakov after Mikoyan’s death in 1971), Chelomey’s TsKBM, and Mishin’s TsKBEM. They came up with two basically different concepts that reflected the conflict between a small vs. a large shuttle.

MMZ Zenit was best prepared to respond to this order, having worked since 1966 on its Spiral air-launched spaceplane and benefiting from actual suborbital flight experience with the BOR-1, 2, and 3 scale models. Strictly speaking, the space branch that had been set up in Dubna in 1967 to work on Spiral was no longer subordinate to MMZ Zenit, having merged in 1972 with MKB Raduga (another former branch of Mikoyan’s bureau) to form DPKO Raduga. The VPK order must have been a major morale booster for Lozino-Lozinskiy’s Spiral team, which because of a lack of government and military support had been forced to do its work on an almost semi-legal basis. It did require the team to divert its attention from the small air – launched Spiral, which had been primarily designed for reconnaissance, inspection, and combat missions. With the focus now shifting to transportation tasks, a larger version of Spiral with a higher payload capacity was needed. Although the details are sketchy, Lozino-Lozinskiy’s team seems to have studied an enlarged 20-ton version of the Spiral spaceplane launched by the Proton rocket.

TsKBM also set its sights on a 20-ton spaceplane to be orbited by the Proton, which itself was a product of Chelomey’s bureau. However, the spaceplane project seems to have been low on Chelomey’s list of priorities at this stage. Indications are that the bulk of spaceplane research at TsKBM was done in the late 1970s, by which time Buran had already been approved (see Chapter 9) [5].

TsKBEM was to focus on a Space Shuttle sized vehicle to be orbited by the N-1 rocket, but it appears that little, if any, work was done on this. The research was to be done by a small team headed by Valeriy Burdakov, but as Burdakov later recalled, the team’s work was limited to studying the possibility of reusing the first stage of the N-1 and keeping track of foreign literature on reusable space systems [6]. However, big changes were ahead at TsKBEM that would turn these plans upside down.

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].