Category Energiya-Buran

The RD-170 (also known as 11D521), designed and manufactured by KB Energo – mash in Khimki near Moscow, was a LOX/kerosene engine employing the staged combustion cycle. Providing 740 tons of thrust and a specific impulse of 308.5 s at ground level, it remains not only the most powerful LOX/kerosene engine built to date, but also the highest-thrust liquid-fuel engine flown on any launch vehicle in the world.

Although Energomash had gained significant experience with staged-combustion cycle engines burning hypergolic propellants, the RD-170 marked the bureau’s first foray into closed-cycle LOX/kerosene engines. The only other closed-cycle LOX/ kerosene engines built in the Soviet Union until then had been much less powerful single-chamber engines such as the ones used on the Blok-L and Blok-D upper stages (built by the OKB-1 Korolyov bureau) and the NK engines for the first three stages of the N-1 rocket (developed by the Kuznetsov bureau in Kuybyshev). The United

States has never built a staged-combustion cycle LOX/kerosene engine. The only powerful LOX/kerosene engine ever flown by the United States was the F-1, five of which powered the first stage of the Saturn V. This was an open-cycle engine inferior in most aspects to the RD-170.

The RD-170 consisted of four combustion chambers, one turbopump assembly, and two gas generators. The turbopump assembly incorporated a single-stage active axial-flow turbine, an oxidizer pump, and a two-stage fuel pump. Connected to the assembly were low-pressure oxidizer and fuel pumps to increase the pressure of the propellant and thereby prevent cavitation of the turbopump assembly. The turbo­pump was driven by two oxidizer-rich gas generators. Originally, it was planned to have a single gas generator consuming 1.5 tons of propellant per second, but this would have been too big. In the RD-170 the entire oxidizer supply and just a small fraction of the kerosene (6% of the overall propellant mass) passed through the gas generators. The turbopump produced about 257,000 horsepower, which the Russians like to compare with the combined horsepower of three of their heavy nuclear icebreakers.

The RD-170 could be throttled down to 50 percent of rated thrust and could be gimbaled about 8° with the help of hydraulic actuators. The engine could be gimbaled in two axes, whereas the Zenit’s RD-171 had only single-axis gimbal capability. Therefore, each RD-170 required a total of eight hydraulic actuators, two for each combustion chamber. Unlike the RD-171 nozzles, those of the RD-170 entered the air stream impinging on the rocket when they were swiveled, requiring the use of more powerful actuators to counter the aerodynamic pressures.

With a nominal flight burn time of 140-150 seconds, the engine was designed to be used at least ten times, a capability confirmed during bench tests. Although the RD-170 was used only for the two Energiya missions in 1987 and 1988, its nearly identical twin (the RD-171) continues to fly today on the two-stage Zenit launch vehicle and its three-stage Sea Launch version. A derived version with just two combustion chambers (the RD-180) now powers America’s Atlas-5 rockets and a single-chamber version (the RD-191) is expected to become the power plant of Russia’s Angara family of launch vehicles (see Chapter 8). [4]

Although Buran lacked main engines for ascent, it did have engines and thrusters for on-orbit maneuvers and attitude control functions. Buran’s propulsion system was known as the Combined Engine Installation (ODU or 17D11) and consisted of an integrated set of orbital maneuvering engines, primary thrusters, vernier thrusters, and associated plumbing.

While the overall number and general location of these engines were similar to those of the Space Shuttle Orbiter’s Orbital Maneuvering System (OMS) and Reac­tion Control System (RCS), there were some fundamental differences between the two vehicles, notably the types of propellant used. Orbital maneuvering and attitude control engines on manned spacececraft have traditionally used hypergolic propel­lants or hydrogen peroxide, which can be stored for long periods of time and do not require complex ignition and turbopump systems. The Space Shuttle Orbiter uses a hypergolic mix of nitrogen tetroxide and dimethyl hydrazine for both its OMS and RCS engines. Although Soviet designers also planned to use hypergolic propellants in their original orbiter concepts (OS-120 and OK-92), they eventually opted for a combination of liquid oxygen and a synthetic hydrocarbon fuel known as sintin. This marked the first time that such propellants were used in any type of orbital maneuvering and attitude control system. Next to the absence of main engines, this was probably the most significant difference between Buran and the Space Shuttle Orbiter.

Cryogenic propellants offered a number of advantages. They gave the orbital maneuvering engines a better performance than those of the Shuttle (although

thruster performance was virtually identical) and were safer to handle by ground personnel because of their non-toxicity. Moreover, the LOX could be cross-fed to the storage tanks of Buran’s electricity-generating fuel cells, providing extra redundancy to the power system and, indirectly, to the life support system, which drew oxygen and water from the fuel cell system. The drawbacks were that the plumbing was more complex, making the ODU 1,100 kg heavier than the Shuttle’s RCS/OMS system. Also, the mix did not ignite spontaneously on contact, such as was the case with hypergolic propellants, but required an electric ignition source. In addition to that, extra measures needed to be taken to prevent the cryogenic oxidizer from boiling off during long missions.

It is interesting to note that in the 1990s US Shuttle engineers considered a cryogenic OMS/RCS as a long-term Shuttle upgrade. This would have used a combination of LOX and ethanol and would have enabled the forward RCS, aft RCS, and OMS engines to draw propellant from common tanks, just as on Buran. It is not clear if this upgrade was in any way inspired by the design of Buran’s ODU.

Like the Space Shuttle Orbiter, Buran was a versatile vehicle that could have been used for a wide range of orbital operations. The following possible tasks were later identified by the Russians:

(a) Deployment of satellites or other cargos: the maximum payload was 30 tons into a 50.7° inclination 200 km orbit and 16 tons into a 97° orbit. The payload bay could house a payload with a maximum length of 15 m and a maximum diameter of 4.15 m. Because of the less stringent center-of-gravity requirements resulting from the absence of main engines, Buran’s maximum payload capacity was actually higher than that of the Space Shuttle.

(b) Servicing satellites in orbit

(c) Returning satellites back to Earth. The maximum mass that could be returned from a 50.7° inclination 200 km orbit was 20 tons.

(d) Space station missions: resupply, assembly, crew exchange, crew rescue.

(e) Missions to assemble large structures in space.

(f) Autonomous scientific missions.

Three basic types of operational mission durations were envisaged for the vehicle. The first would be short-duration missions (up to 3 days) to place heavy payloads into orbit, deliver emergency supplies to space stations, or rescue space station crews. Such missions would be characterized by multiple operations and maneuvers in a relatively short time span, heavily taxing both the crew and the ground and also requiring many of them to be conducted automatically.

Medium-duration missions (up to 8 days) were expected to be the most frequent ones and would have several objectives or one particularly time-consuming and demanding goal. Typical medium-duration flights would include routine missions to space stations, multiple satellite deployment missions, satellite-servicing missions, assembly flights, etc. Although comparable in the number of operations with the short-duration flights, the longer time in orbit would make it possible to more evenly spread the workload for the crew.

Finally, long-duration missions (9 to 30 days) would primarily be devoted to scientific, materials-processing, and biotechnological experiments, which take a relatively long time to produce the necessary results. For this purpose, the Russians were planning to develop a Spacelab-type module to be placed in the cargo bay. The longest missions would have required the installation of an extra cryo kit for the fuel cells. The number of maneuvers performed during this type of mission would have been very low. In terms of the daily workload for the crew and the ground, such missions would have been comparable with a routine workday on a space station.

Range safety restrictions at the Baykonur cosmodrome, mainly dictated by the impact zones of the strap-on boosters, limited the possible orbital inclinations of the spacecraft to 50.7-83°, 97°, 101-104°, and 110°. The vehicle could have operated at altitudes between 200 and 1,000 km, although the higher of these would have necessitated the installation of extra propellant tanks in the cargo bay [29].

The modular part of the Energiya strap-on boosters was designed by KB Yuzhnoye in the Ukrainian city of Dnepropetrovsk. This originated in 1954 as OKB-586 and under the leadership of Mikhail K. Yangel pursued the development of ballistic missiles using storable propellants as well as derived launch vehicles such as the Kosmos and Tsiklon series of boosters. Renamed KB Yuzhnoye in 1966, it was also in charge of developing a wide array of military and scientific satellites. Yangel died in 1971 and was succeeded by Vladimir F. Utkin, who headed the organization until 1990.

Yuzhnoye’s production facility was the Yuzhnyy Machine Building Factory (YuMZ or “Yuzhmash”), originally founded in 1944 as the Dnepropetrovsk Automobile Factory. In 1951 it was renamed Factory nr. 586 and ordered to switch to the serial production of OKB-1 missiles (the R-1 and R-2). Several years later it began producing missiles and eventually launch vehicles and satellites for KB Yuzhnoye. During the Buran years Yuzhmash was headed by Aleksandr M. Makarov (1961-1986) and Leonid D. Kuchma (1986-1992), the later President of the Ukraine. Eventually, serial production of the modular part of the Energiya strap – ons was also to be transferred to PO Polyot in Omsk, but this apparently never happened.

The Cosmonaut Training Center was the first to select a dedicated group for the Buran program. On 23 August 1976, just six months after the official approval of the Energiya-Buran program, nine pilots were chosen, the first selection by TsPK in six years. They were:

• Leonid Georgyevich Ivanov;

• Leonid Konstantinovich Kadenyuk;

• Nikolay Tikhonovich Moskalenko;

• Sergey Filippovich Protchenko;

• Yevgeniy Vladimirovich Saley;

• Anatoliy Yakovlevich Solovyov;

• Vladimir Georgyevich Titov;

• Vladimir Vladimirovich Vasyutin;

• Aleksandr Aleksandrovich Volkov;

All of them were young, relatively inexperienced Air Force pilots in their mid to late twenties. The rationale behind their selection at this early stage may have been that they would need several years to advance their flying skills while the more experienced LII and GKNII test pilots conducted the early Buran test flight program.

Not surprisingly, it was decided that the cosmonauts would first have to undergo test pilot training before beginning the standard cosmonaut training course. They began studying and training at TsPLI in Akhtubinsk in September 1976, becoming Test Pilots 3rd Class (the lowest test pilot rank) in June 1977. In addition, in August they conducted parachute training. From October 1977 until September 1978 they then underwent the standard basic cosmonaut training course (“General Space Training” or OKP) at TsPK.

After graduation most members of the group (Ivanov, Kadenyuk, Moskalenko, Protchenko, Saley, Solovyov, and Volkov) returned to Akhtubinsk to resume test pilot training with the goal of becoming Test Pilots 2nd Class. It was during this follow-up course that Sergey Protchenko was medically disqualified and dismissed from the cosmonaut team in April 1979 [3]. More than a year later, on 24 October 1980, the group suffered another loss when Leonid Ivanov was killed in the crash of a MiG-27 in Akhtubinsk.

On 22 June 1981, Kadenyuk, Moskalenko, Saley, Volkov, and Solovyov were awarded the title Test Pilot 2nd Class. After that, the first four went on to conduct Buran-related training, but Solovyov was transferred to the Salyut space station program, together with Titov and Vasyutin.

Leonid Kadenyuk was the next to be dismissed. He left the cosmonaut team in March 1983 after he had divorced his wife. In the Soviet Union of the 1970s and 1980s, getting a divorce usually resulted in the end of a cosmonaut career for those who were still awaiting their first mission.

The 1976 selection had been limited to the Air Force and it was therefore decided that another screening would take place in the Soviet Navy and Air Defense Forces

[4]. As a result, on 23 May 1978 one additional candidate from each of these two branches of the military was added to the detachment:

• Nikolay Sergeyevich Grekov (Air Defense Forces);

• Aleksandr Stepanovich Viktorenko (Navy).

In October 1978 the two began training in Akhtubinsk, graduating as Test Pilot 3rd Class on 2 July 1979. They then returned to Star City, where they underwent OKP, finishing that in February 1982. Viktorenko almost died in a bizarre accident during a medical check-up in 1979. He was wearing a band with electrodes around his body to have an ECG made when a 220-volt current was accidentally sent through it. Apparently his heart stopped and he was brought back to life using CPR. According to Viktorenko the incident cost him quite some time in training as the doctors wanted to be 100% certain that he had not suffered any ill effects from the incident [5].

As the training went on, it was becoming increasingly apparent that Buran’s first flights would be significantly delayed. Since TsPK was becoming confronted with a shortage of commanders for Soyuz and Salyut, it was decided in late 1983 to transfer all members of the 1976 and 1978 selections to the space station program. In the following years, they would become the core of the cosmonaut detachment, with several of them flying record-breaking missions (for details on further careers see the cosmonaut biographies in Appendix B).

Like the RD-0120, Energomash’s RD-170 engines for the strap-on boosters under­went a step-by-step test program, moving from autonomous tests of individual components to full-scale test firings at increasing rates of thrust. Bench tests were not only carried out with the engines alone (at Energomash’s own test facility), but also with the engines mounted on the modular part of the strap-ons (at

Nllkhimmash). Test firings of complete strap-ons at Baykonur’s UKSS pad were ultimately canceled, at least partially because the RD-171, the near twin of the RD-170, had already undergone flight testing on the first stage of the Zenit rocket. The road to success for the RD-170 proved much more arduous than for the RD-0120, with several setbacks plunging the program into deep crisis in the early 1980s.

For most of the 1980s the BOR-4 vehicles were widely interpreted in the West as subscale models of a military spaceplane to be launched by the Zenit rocket, a program that was believed to run parallel to the Energiya-Buran effort (see Chapter 7). But, even as BOR-4 led a life of its own in the imagination of Western analysts, the Russians were considering using the spacecraft for other missions. One vehicle, possibly the one that had originally been supposed to fly the fifth BOR-4 orbital flight, was modified for an experiment to evaluate radio transmissions during atmospheric re-entry from a suborbital mission. Dubbed BOR-6, it was equipped with two large antennas extending out and downward from the nose. Using a special cooling system, these antennas were designed to see if radio signals could penetrate the plasma sheath that envelops spacecraft during re-entry and causes radio black­outs. Construction of the spacecraft was finished by 1990, but it was never launched due to the collapse of the Soviet Union and the ensuing shutdown of the Buran program. The Russians also looked at the possibility of converting BOR-4 type vehicles into space-to-ground weapons as part of a Soviet “Star Wars” program (see Chapter 8).

With the political climate changing and the Russians scrambling to find new customers for their space technology, BOR-4 was offered on a commercial basis to the international community in the early 1990s. The European Space Agency weighed the possibility of using BOR-4 vehicles to test the heat shield of Europe’s Hermes spaceplane, but these plans never materialized.

Interestingly enough, as early as 1983 the BOR-4 recovery images inspired engineers at NASA’s Langley Research Center to clandestinely build small models of the subscale spacecraft. Over subsequent years they analysed and improved the design in over 1,200 wind tunnel and computer tests to refine the shape of the outer mold line. This resulted in plans for a 10-ton spaceplane called HL-20, a lifting body closely resembling BOR-4 and considered in the early 1990s as a crew transportation system and crew rescue vehicle for the Freedom space station. Also known as the Personnel Launch System (PLS), it would be launched by an expendable rocket such as the Titan-4 and be capable of carrying a crew of 10. Although a full-scale mock-up of the HL-20 was built, the design was not selected for further development as the Russian Soyuz spacecraft was picked as the lifeboat for Freedom and eventually the International Space Station. Later in the 1990s Langley proposed a 42 percent dimensional scale-up of the HL-20 called the HL-42, but this seems to have been a short-lived effort.

The BOR-4/HL-20 design was once again picked up by the Orbital Sciences Corporation in the late 1990s for a “Space Taxi” proposed initially under NASA’s Space Launch Initiative and later as a candidate for the Orbital Space Plane that would complement the Shuttle by carrying crews to and from orbit, but the project was canceled after the February 2003 Columbia accident.

In January 2006 NASA announced a program called Commercial Orbital Trans­portation Services (COTS) in which two industry partners would receive a combined total of approximately $500 million to help fund the development of a reliable, cost- effective commercial transportation system to support the International Space Station after the retirement of the Space Shuttle in 2010. One of the vehicles studied was SpaceDev’s Dream Chaser. Having the same size and outer mold line as BOR-4 and the HL-20, it would fly six rather than ten passengers in order to save weight. Although Dream Chaser was eventually not selected, SpaceDev founder Jim Benson created a new company called the Benson Space Company that intends to purchase multiple Dream Chaser vehicles from SpaceDev to become the first-to-market with a spaceship designed for both suborbital and eventually orbital flights. Benson hopes it will also be used to transport people and cargo to the International Space Station and to a variety of emerging private-sector orbital destinations [18].

The troubleshooting was not finished until after the October Revolution holiday, celebrated on 7 November. However, as Gudilin said in one interview:

“the time has gone by when launches were hurried along to fit in with holiday dates.”

On 12 November TASS announced that the launch had been rescheduled for 15 November at 6:00 Moscow time (3:00 gmt, 8:00 local time at Baykonur). Visual observations from Mir were no longer a factor in determining the launch time, probably because orbital precession had shifted the station’s flight path such that it now passed over the cosmodrome much earlier than was acceptable for the Buran launch.

The biggest concern as launch time drew closer was the weather. While skies had been crystal clear for the launch attempt on 29 October, a low-pressure front bringing rain and strong winds was now approaching Baykonur from the Aral Sea. At 17: 00 local time (12: 00 gmt) on 14 November meteorologists reported they were seeing a tendency for the front to bypass Baykonur, although nothing could be guaranteed. Four hours later the forecast had remained unchanged and the State Commission decided to press ahead with fueling of the rocket. First to be loaded were the liquid – oxygen tanks of both the strap-on boosters and core stage, followed about two hours later by the kerosene tanks of the strap-ons and the core stage liquid-hydrogen tank. Soviet media made no secret of the iffy weather conditions. On the eve of launch, a correspondent of the Vremya evening television news program reported:

“Everything that depends on people has been done. But the weather is worsening with each passing hour. If the wind rises into a squall and the orbital vehicle… becomes covered with a crust of ice, then the launch time will be changed again.’’

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Gale warning issued at 6:15 am local time (source: wwww. buran. ru).

At midnight local time, with fueling of the liquid-oxygen tanks underway, the forecast took a turn for the worse. The low-pressure front had broken up in two parts, one of which was now headed straight for the launch site. Less than 2 hours before launch the chief weather officer handed over a gale warning to Gudilin. Conditions expected between 7:00 and 12:00 local time (2:00-7:00 gmt) both at the launch pad and the runway were strengthening southwest winds with speeds of 9 to 12m/s, gusting to 20m/s. Meanwhile, weather balloon data also showed unstable conditions up to altitudes of 25 km, with highly variable wind speeds (maximum 70m/s) and wind directions at different levels. With just 30 minutes left in the count­down, observed conditions were overcast skies with a cloud ceiling at 550 meters, drizzle, winds of 15m/s gusting to 19m/s, a temperature of +2.8°C, and visibility of 10 km. The agreed wind speed limit for launch was 15m/s, while for landing the maximum allowed wind speeds were 5 m/s for tail winds, 10 m/s for crosswinds, and 20 m/s for head winds.

The marginal weather conditions were a matter of concern for several reasons. The combination of drizzle and low temperatures posed the threat of significant ice build-up on the rocket, orbiter, and launch pad. Chunks of ice falling off the rocket during launch could cause significant damage to Buran’s fragile thermal protection system. This risk has always been well understood in the Space Shuttle program, where specialized ice inspection teams are routinely sent out to the pad in the final hours before launch. The available information suggests that the Russians considered
a 2 mm ice layer on the rocket acceptable and decided to go ahead based on the prediction prior to fueling that the thickness of the layer would not exceed 1.7 mm. All indications are that no ice inspection teams were sent to the pad and that any later estimates were based solely on close-up television shots of the launch vehicle. Apparently, those images were not always reassuring. As Gudilin later recalled:

“we could see relatively big chunks of ice falling from the rocket and the

orbiter.”

Aside from ice build-up on the vehicle, there were worries about ice formation on the runway and the general effects of cold weather on vehicle performance. Although Energiya had no solid rocket boosters, the Challenger accident, where cold tempera­tures had contributed to the failure of an О-ring seal in one of the solids, was “in the back of our minds”, as Gudilin puts it in his memoirs.

Another issue were the strong winds both at ground level and in the upper atmosphere. There were fears that ground-level winds could cause the vehicle to hit one of the launch pad structures during lift-off and that unstable upper-level winds could knock the stack off course. Weather officers at Baykonur continuously sent the latest wind data to a team of specialists at NPO Elektropribor in Kharkov, the design bureau that was responsible for Energiya’s guidance, navigation, and control systems. Computer simulations there convinced the team there was enough margin to go ahead, although the observed conditions were clearly outside the experience base for this type of launch vehicle. Winds were also near or above prescribed limits for a return-to-launch-site abort or a nominal landing. That problem was addressed by having Buran approach the runway from the northeast rather than the southwest, turning an out-of-limits tail wind into an acceptable head wind, although even that was on the limit.

The weather on 15 November 1988 violated just about every imaginable meteorological launch commit criterion for a Space Shuttle launch. Leaving aside the temperatures and the wind, two other showstoppers for a Shuttle launch that day would have been the precipitation and the low cloud cover. No NASA launch or flight director in his right mind would even consider launching or landing a Shuttle Orbiter if there is only the slightest chance of precipitation in the vicinity of the launch pad or runway. With the Orbiter moving at high speeds, precipitation has the potential of causing significant damage to the vehicle’s thermal protection system. However, for reasons that are not entirely clear, precipitation was no safety issue for the Russians, even though Buran’s thermal protection system was very similar to that of the Orbiter. Even hail was said to be an acceptable condition, although this may have been bluff more than anything else. In fact, Buran’s tiles suffered serious damage when the vehicle ran into a hail storm during a trip atop the Mriya carrier aircraft in 1989.

Cloud cover was not an issue for the Buran launch because there were no pilots on board who needed a clear view of the runway for a return to launch site or manual landing. The only clouds that meteorologists kept a close eye on were those with lightning potential. The overcast skies did prevent good ground-based optical track­ing during launch and landing, which can be a critical factor in post-flight analysis of anomalies.

Even though conditions were close to violating launch commit criteria, the team decided to fly anyway, despite another gale warning issued just 13 minutes before launch. True, the Russians’ launch weather rules in general were more relaxed than those adopted by NASA or the US Air Force, with some launches known to have taken place in near-blizzard conditions. However, the Buran mission was different from a conventional rocket launch in that the spacecraft was supposed to land like an aircraft.

All this begs the question why officials didn’t wait one or more days for the weather to clear, especially because this was the maiden flight of a vehicle vastly different from anything the Russians had flown before. Speaking shortly after the mission, former cosmonaut Gherman Titov said:

“We deliberately refused to postpone the launch and wait for ideal conditions.

The value of the flight is that its program included the maximum sum of real and

rather difficult tasks’’ [47].

Still, one can only wonder if the team didn’t suffer from what is sometimes referred to in the US as “launch fever’’. Testifying to this is an eyewitness report of one member of the meteorological support team, who claims that some of the observations that morning showed wind gusts of up to 25 m/s. However, the chief weather officer, under pressure to report good news, only presented the launch team with the weather updates that showed the lower wind speed values. The same person notes that Gudilin’s main argument in favor of launching that day was that another scrub could delay the flight until spring. It would require more testing and take them further into late autumn and possibly winter, when weather conditions can get far worse than the ones observed that morning [48].

Another concern with a lengthy delay may have been that the already frail support for the Buran program from the Soviet leadership might dwindle even further and could put the flight on indefinite hold, particularly now that the US Space Shuttle had returned to flight. Still, whatever the real motives were for launching that day, it was a decision fraught with risk [49].

While Buran was never seriously considered for routine satellite deployment mis­sions, the Russians did look at the possibility of placing big payloads in the cargo bay. Among these were spacecraft developed as part of a Soviet “Star Wars’’ program in which NPO Energiya was given the leading role in 1976. It would have seen the use of space-based assets to destroy enemy satellites, ballistic missiles, and ground-based targets. Making maximum use of existing technology, NPO Energiya tabled proposals for “battle stations’’ that would be based on Salyut and Mir technology.

For anti-satellite operations the idea was to develop two types of Salyut look – alike space stations, one equipped with missiles (Kaskad) and the other with laser weapons (Skif). The stations carried much larger propellant supplies than their

progenitors, but had man-tended capability, being able to house two-man crews for up to seven days. Kaskad stations would target high-orbiting satellites, while the Skif stations were to knock out satellites in low orbits. Experimental versions of these stations would be orbited by the Proton rocket, but the operational ones were designed to go up in the cargo bay of Buran. The Soviet orbiter would also be responsible for refueling missions to these stations. In 1981 work on Skif/Kaskad was transferred to Energiya’s new KB Salyut branch, which dropped the Salyut – based design in favor of 100-ton Energiya-launched spacecraft (see Chapter 6). There are no indications Buran still had any role to play in Skif/Kaskad from that moment on.

For destruction of ground-based targets the NPO Energiya planners came up with a Mir-type core module with four specialized modules docked to a ball-shaped multiple docking adapter. Attached to the axial front port was a module with an additional multiple docking adapter that served as the berthing place for so-called “combat modules’’ resembling Buran orbiters without wings or other aerodynamic surfaces. After undocking from the station, the unmanned combat modules would maneuver to the proper location and then deploy small vehicles tipped with (un­specified) weapons that could re-enter the atmosphere. These could be either ballistic – type vehicles or lifting bodies. One design studied for these re-entry vehicles was based on the BOR-4 lifting bodies. Presumably, the idea was that after deploying the weapons the Buran-based combat modules would return to base to be reloaded with new ones [35].

One big military satellite intended for launch by Buran was Sapfir (“Sapphire”), a 24-ton optical reconnaissance satellite developed by TsSKB in Kuybyshev. This was equipped with a 3 m diameter telescope to photograph targets of interest in great detail. The idea was that Buran crews would regularly visit Sapfir for servicing. Although the telescope for the first such satellite was nearly finished, the project was discontinued after the cancellation of Buran, since the Proton rocket was not capable of orbiting the satellite [36].

Another big payload eyed for launch by Buran was ROS-7K (“Radiotechnical Orbital Station”), a man-tended Salyut-derived space station equipped with a 30 m diameter dish antenna called KRT-30. Capable of serving as a radio telescope and a radar, the KRT-30 was to be used for all-weather remote-sensing, astrophysical, and geophysical observations and target localization for the Soviet Navy. Together with the ground-based components needed to receive, process, and distribute data from the station, the system was called Gals (“Tack”, in the nautical meaning), an indica­tion that its observations in support of the Soviet Navy were seen as its primary mission.

Flying in a circular 600 km orbit inclined 64.8° to the equator, ROS-7K could house two-man crews up to seven days for maintenance operations and could be refueled in orbit. The complete ROS-7K with the stowed KRT-30 fitted in the cargo bay of Buran, although launch by the Proton rocket was studied as an alternative. Buran was also supposed to fly a technology demonstration mission in support of ROS-7K/Gals called “Karat”, but no further details on this are available. Gals was studied at NPO Energiya from 1978 until 1987 [37].

Buran (along with Proton) was also considered to launch a giant space tug powered by a nuclear electric engine. Called Gerkules (Russian for “Hercules”), the tug was to be stationed in a 200 km orbit and one of its tasks was to maneuver 100-ton spacecraft launched by Energiya to geostationary orbit. Given the 35m length of the tug, several missions would have been required to assemble it in orbit. Gerkules studies at NPO Energiya began in 1978 and lasted until at least 1986 [38].

Another exotic payload studied for launch by Buran or Proton was an experi­mental, orbiting solar power station, consisting of a solar tug and a dish antenna (based on the KRT-30). Deployment of the experimental solar power station would have required two Proton or Buran launches [39].

NPO Energiya also looked at so-called “Experimental Space Apparatuses” (EKA) that appear to have been prototypes of expensive new satellites that would be thoroughly checked out in orbit by Buran. The crew would, for instance, check if vital systems (such as various appendages) worked and carry out repair work if necessary. The EKA could then later be revisited for maintenance operations or the retrieval of valuable parts for analysis on Earth or reuse on later satellites [40].

Another future assignment for Buran occasionally mentioned by Russian sources was the retrieval of satellites from space. While this may have sounded attractive, such missions usually require that satellites are designed to be picked up by an orbiter—that is, have grapple fixtures for the orbiter’s remote manipulator system and be small enough to fit in the payload bay—and, above all, circle the Earth in orbits that can be reached by it. In practice, that would have virtually limited such

missions to satellites deployed by the orbiter itself and not equipped with a kick motor to be boosted to high orbits. The original 1976 government/party decree on Buran had called for the development of a reusable space tug (11F45) to operate between low and high orbits, but that was never developed. In one interview Yuriy Semyonov mentioned the possibility of retrieving nuclear-powered satellites that threatened to fall back to Earth [41]. The only such satellites operated by the Soviet Union were the US-А radar ocean reconnaissance satellites and it looks unlikely they could ever have been retrieved by Buran, if only because of the radiation threat to the crew.

One other mission studied for Buran was to retrieve elements of the Salyut-7 space station. Launched in 1982, Salyut-7 played host to its final crew in May 1986 before definitively passing the torch to Mir. However, rather than deorbiting it, as had been the usual practice with earlier Salyuts, the Russians boosted the station and the attached Kosmos-1686 spacecraft (a Transport Supply Ship or TKS) to a 474 x 492 km storage orbit in August 1986 to see how well their systems would stand up to a prolonged stay in space and use that experience in designing future spacecraft. Some two weeks after the maneuvers Yuriy Semyonov said in an interview that “in a few years a group of cosmonauts could be sent to Salyut to study the state of the orbital complex” [42].

In December 1988, with Buran no longer a state secret, Semyonov acknowledged that the idea was to send a Buran crew to Salyut-7 in 1995-2000 and retrieve parts of the complex for detailed analysis on Earth, adding this would provide invaluable data on prolonged exposure of materials to space conditions [43]. Some reports at the time suggested the plan was to retrieve the entire Salyut-7 space station, but given the technical complexity of such a mission, that never seems to have been the intention.

However, Salyut’s orbit decayed much faster than predicted due to unexpectedly high solar activity in the late 1980s/early 1990s that caused the upper layers of the atmosphere to expand considerably. On top of that, Kosmos-1686 suffered a failure of its electrical systems in December 1989, making it impossible to use the vehicle’s thrusters to keep the station in a gravity-gradient mode. With little fuel left in Salyut’s own tanks, the complex eventually made an uncontrolled re-entry on 7 February 1991, showering debris over South America.

The unification of the first stage of the medium-lift 11K77/Zenit rocket with the strap-on boosters of Energiya was a sound engineering decision, allowing the RD-170 engine and associated systems to be thoroughly tested in flight before the maiden mission of Energiya. However, the 11K77 was far more than just a test bed for Energiya, having been conceived at KB Yuzhnoye long before Energiya as a rocket in its own right to orbit a new generation of heavier satellites. Before being unified with Energiya’s first stage, the 11K77 had already evolved from an R-36M derived launch vehicle with storable propellants to a LOX/kerosene rocket with a clustered first stage (see Chapter 2). The 11K77 not only pre-dated Energiya, but has now long outlived it, continuing to fly today both in its two-stage domestic version and the three-stage Sea Launch version. Along with the RD-180 engine, it is undoubtedly the most tangible spin-off of the Energiya-Buran program, with a bright future ahead of it more than 20 years after its first flight. Not only did Zenit serve as a pathfinder for Energiya, it was also supposed to be the central component of its own rocket family, including a downsized version (11K55) and several heavier variants (11K37), none of which ever made it off the ground.