Category Energiya-Buran

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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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.

Between 1984 and 1993 NPO Energiya studied several relatively small spaceplanes that were primarily intended to replace Soyuz and Progress for space station support. These had the general designator OK-M (Small-Size Orbital Ship).

The basic OK-M was a 15-ton spaceplane launched by the Zenit rocket. The interface between the vehicle and the rocket was an adapter equipped with four 25-ton solid-fuel motors that could be used to either pull the ship away from the

rocket in an emergency or to provide extra thrust during launch by being activated shortly after second-stage ignition. Aerodynamically, OK-M was a mini-version of Buran, having delta wings with elevons and a vertical stabilizer with rudder/speed brake. The outer surface was covered with Buran-type heat-resistant tiles. The ship could carry a crew of two in the cabin and—if required—four more cosmonauts in a pressurized module inside its 20 m3 cargo bay. The nosecap of the vehicle would be retracted to expose an androgynous docking port. OK-M had two orbital maneuver­ing engines and 34 thrusters, all burning nitrogen tetroxide/UDMH. Power was to be provided by 16 batteries, although solar panels were also considered. Payload capacity was 3.5 tons to a 51.6°, 200 km orbit and just 2 tons to a 450 km Mir-type orbit.

Better satisfying the logistics requirements of space stations were two heavier spaceplanes called OK-M1 (31.8 tons) and OK-M2 (30 tons). Jointly developed with NPO Molniya, they were very similar to the air-launched MAKS-OS spaceplane.

However, NPO Energiya felt that such vehicles should be launched with conventional rocket systems until various mass-related and other technical issues associated with the air-launch technique were solved.

The main difference between OK-M1 and OK-M2 was the launch profile. For OK-M1 Energiya studied a rather unwieldy-looking two-stage-to-orbit configuration known as the Reusable Multipurpose Space Complex (MMKS). This consisted of a huge external fuel tank with the small spaceplane strapped to one side and a Buran look-alike vehicle to the opposite side. The external tank contained liquid oxygen, liquid hydrogen, and kerosene to power tripropellant engines in both vehicles. The Buran-sized vehicle was to act as the system’s first stage. It essentially was a Buran without a crew compartment carrying extra liquid oxygen and kerosene tanks in the cargo bay to feed four main engines in the tail section. After separating from the external tank, it would return to Earth using two jet engines mounted on either side of the mid fuselage. Next the OK-M1 would fire its two main engines to reach orbit. Safety features for OK-M1 included ejection seats for the crew and an emergency separation system.

OK-M2 was to be launched atop an Energiya-M rocket with conventional strap – on boosters or winged flyback boosters. The adapter connecting it to the rocket was virtually identical to that in the Zenit/OK-M configuration and also included solid – fuel motors that could be used either in a launch abort or for final orbit insertion. Another option was to install ejection seats in the vehicle, which would allow the use of a much simplified and lighter adapter section.

Because of the different launch technique, OK-M2 required no main engines, which translated into a higher payload capacity—namely, 10 tons to a 250 km, 51.6° inclination orbit vs. 7.2 tons for OK-M1 (6 and 5 tons, respectively, for Mir-type altitudes). Other differences were a LOX/kerosene orbital maneuvering/reaction control system for OK-M1 (2 OMS engines and 18 thrusters) vs. LOX/ethanol for OK-M2 (3 OMS engines, 27 thrusters). Both vehicles could accommodate four crew members in the crew compartment and another four in a pressurized module in the 40 m3 cargo bay. The power supply system relied on a combination of fuel cells and batteries. Just like MAKS-OS, both ships had foldable wings [13]. In 1994 a proposal was made to launch OK-M2 with a European Ariane-5 booster outfitted with Energiya strap-on boosters [14].

Concurrently with the OK-M studies, NPO Energiya worked out plans for a ballistic reusable spacecraft called Zarya (“Dawn”). This looked like an enlarged Soyuz descent capsule with a small expendable instrument section attached to it. Weighing 15 tons, it would be launched by Zenit and make a vertical landing using a cluster of 24 liquid-fuel braking engines rather than parachutes. The heat shield would be similar to that of Buran. Zarya was mainly intended for space station support, but also was to fly autonomous missions in the interests of the Ministry of Defense and the Academy of Sciences. Maximum crew capacity was eight.

Indications are that Zarya was considered a much more likely contender to replace or complement Soyuz/Progress than the OK-M spaceplanes. While OK-M was no more than a conceptual study, Zarya development was sanctioned by a government decree in January 1985 and even went beyond the “preliminary design’’ phase. Zarya was eventually canceled in January 1989 due to a lack of financing, although Valentin Glushko’s death that same month may have contributed to the decision [15].

Until the late 1950s the OKB-52 of Vladimir Chelomey was a relatively minor design bureau specializing in anti-ship cruise missiles. However, by the end of the decade Chelomey’s star began to rise, something that he owed at least partially to the fact that Khrushchov’s son Sergey began working at the design bureau in 1958. Brimming with ambition, Chelomey set his sights on intercontinental missiles and space projects. From the outset he focused his research on winged spacecraft, not just for missions in Earth orbit, but also for flights to the Moon and planets.

In 1958-1959 OKB-52 began working on two projects called Kosmoplan and Raketoplan. Kosmoplan was a rather futuristically looking family of spacecraft primarily designed to fly to the Moon, Mars, and Venus and then return to Earth. During re-entry the winged landing vehicle would be protected from thermal stresses by a jettisonable container shaped somewhat like a furled umbrella and it would land on a conventional runway using turbojet engines. One early version of the Kosmoplan was also intended for military reconnaissance missions in low Earth orbit. Initial Kosmoplan missions would be automated, with the eventual goal being to switch to piloted flights, first for the Earth-orbital version and later for the deep – space versions.

Raketoplan was initially conceived as a suborbital vehicle to carry passengers and cargo over intercontinental distances and, more importantly, to perform bomb­ing missions. Launched by a conventional rocket or a winged fly-back booster, it would perform suborbital ballistic flights with aerodynamic braking, maneuvering and landing on a runway using turbojets. Two versions were studied, one for a range of 8,000 km and the other for a range of 40,000 km.

Chelomey received official support for the projects with a government and party decree of 23 June 1960, which saw a clear shift in emphasis from civilian to military space projects compared with the space plan outlined in the December 1959 decree. It

called for the development of two unmanned deep-space versions of the Kosmoplan (“Object K”) by 1965-1966, one with a mass of 10-12 tons and the other with a mass of 25 tons. The vehicles were to be launched by a new Chelomey rocket with a launch mass of 600 tons. Raketoplan (“Object R”) was now eyed as an orbital spaceplane with a mass of 10-12 tons. An unmanned version would be ready in 1960-1961, a piloted variant in 1963-1965, and an anti-satellite version in 1962-1964 [22].

However, these goals turned out to be overly ambitious and another government decree on 13 May 1961 ordered OKB-52 to limit this work to a piloted version of the Raketoplan for military missions in Earth orbit and for deep-space missions. By 1963 engineers had completed the preliminary design for four variants of such a vehicle: two single-seat Earth-orbital versions for anti-satellite and bombing missions, a two – seat scientific spacecraft for circumlunar flight, and a seven-seat passenger ballistic spacecraft for intercontinental ranges. The first three were to be launched by the Chelomey bureau’s UR-500/Proton, the fourth by the UR-200. Despite the name Raketoplan, the circumlunar spacecraft appears to have been a wingless vehicle for a ballistic re-entry from lunar distances, one that would later evolve into a vehicle called LK-1 that had a shape reminiscent of the US Gemini capsule.

By early 1964 the Raketoplan project was left with only military goals, namely orbital reconnaissance and anti-satellite missions. At this time OKB-52 was planning two versions, the unmanned R-1 and the manned R-2, both weighing 6.3 tons. The R-1 was a model of the piloted version designed to test all essential systems in orbit. The R-2, manned by a single pilot, would fly 24-hour missions in a nominal orbit of 160 x 290 km.

Two test vehicles were developed in the framework of the Raketoplan project to test heat shield materials, flight control systems, and maneuvering characteristics at hypersonic speeds. One was a 1,750 kg model called MP-1, a cone-shaped vehicle with two graphite rudders and a set of speed brakes at the base resembling an unfurled umbrella. The MP-1 was launched by an R-12 missile from the Vladimirovka test site near Kapustin Yar (Volgograd region) on 27 December 1961. Having reached a

maximum altitude of 405 km, it successfully re-entered the atmosphere at a speed of 3,800m/s and safely landed on three parachutes 1,880 km downrange. This marked the first ever re-entry test of an aerodynamically controlled vehicle. It came about two years before the US Air Force began similar flights under the so-called START program.

The other vehicle was named M-12 and looked quite similar to its predecessor, except that the umbrella-shaped braking panels were replaced by four titanium rudders. Using the same missile and launch site as the MP-1, the 1,700 kg M-12 was launched on 21 March 1963, but was lost during re-entry, probably because of a problem with its heat shield. The data obtained during the tests were also applicable to OKB-52’s research on maneuverable warheads. This was particularly the case for the M-12, which was seen as a subscale model of the AB-200 warhead. The MP-1 and M-12 were significant in that they were the only hardware ever launched in support of the multitude of Soviet spaceplane projects conceived in the late 1950s and early 1960s.

The Raketoplan project was discontinued in 1964-1965. There appear to have been several reasons for this. First, Chelomey lost much of his political support when Khrushchov was overthrown and replaced by Brezhnev in October 1964. Second, the design bureau was heavily involved in other manned space projects such as the LK-1 circumlunar program and the Almaz military space station. Finally, many of the military objectives planned for Raketoplan were already being or about to be performed by unmanned satellites such as OKB-1’s Zenit (for photographic recon­naissance) and OKB-52’s own US (for ocean reconnaissance) and IS (for anti-satellite missions). The whole research database on Raketoplan along with a number of Chelomey’s specialists were transferred to the Mikoyan design bureau [23].

By the middle of 1975 two competing designs had emerged within NPO Energiya for a Soviet response to the Space Shuttle. In Glushko’s vision the orbiter would be just one of the payloads for his RLA rockets, mounted on top of the rocket as a conventional payload. If a winged orbiter was going to be mounted atop an RLA booster, it would place very high loads on the core stage, especially during the phase of maximum aerodynamic pressure. Therefore, the core stage would have to be strengthened, making it even heavier than it already was and decreasing the rocket’s payload capacity [52]. Therefore, the top-mounted orbiter would have to be a wing­less, vertical-landing lifting body. This configuration was backed by NPO Energiya luminaries such as Boris Chertok, Yuriy Semyonov, and Konstantin Bushuyev, who were convinced the USSR was not capable of building a reusable space transporta­tion system akin to the Space Shuttle [53]. It would also eliminate some thorny organizational problems, requiring minimal involvement from the Ministry of the Aviation Industry.

Another option under consideration was to mimic the Space Shuttle as closely as possible, namely to build a winged orbiter with main engines which would be strapped to an external fuel tank with strap-on boosters. Known as OS-120, it would enable the Russians to benefit from research and development done in the US and thereby minimize risk. While backed by Igor Sadovskiy, it was Glushko’s nightmare, since this design left no room for the family of launch vehicles he had been dreaming of for many years. The philosophy behind the OS-120 was that the Soviet Union would solely be able to match the US Shuttle’s capability to place 30 tons into orbit and return 20 tons back to Earth and nothing more. After all, the 100 to 200-ton payload capacity of the heavy RLA rockets, mainly needed for establishing lunar bases and staging manned interplanetary missions, was of little interest to the Soviet military.

With Buran being only one of many possible payloads of Energiya, flight control functions were divided between the rocket and the orbiter, each using their own set of computers. This is very different from the integrated US Space Shuttle system, where the Orbiter’s General Purpose Computers are in control of all flight events. Being the most complex rocket ever built by the Russians, flight control proved to be a daunting task, facing designers with many unprecedented problems.

Originally, the flight control systems for both Energiya and Buran were to be built at NPO AP (Scientific Production Association of Automatics and Instrument Building), a Moscow-based organization headed between 1948 and 1982 by Nikolay A. Pilyugin. However, in 1978 the development of Energiya’s control system was entrusted to NPO Elektropribor, an organization based in the Ukrainian city of Kharkov and originally founded as OKB-692 in 1959 (now called NPO Khartron). Since the early days it had been headed by Vladimir Sergeyev, replaced in 1986 by A. G. Andryushchenko. The chief designer of the Energiya control system was Andrey S. Gonchar and a leading role in its development was also played by Yakov E. Ayzenberg, who would go on to lead the organization in 1990. Production of the hardware took place at the Kiev Radio Factory. NPO AP built the orbiter flight control system and remained in overall charge of the Energiya-Buran flight control system [5].

The core stage had a primary computer (called M6M) and a computer charged with continuously monitoring the operation of all Energiya’s engines and shutting any one of them down if needed. Each Blok-A strap-on booster had a M4M computer in its nose section. There was continuous interaction between the com­puters in the core stage and the strap-on boosters. Crucial commands such as nominal or emergency shutdown of both core stage and Blok-A engines and separation of the boosters were issued by the core stage computers [6].

Each booster had a single inertial guidance platform (17L27) built by NPO Elektromekhanika in Miass (Chelyabinsk region). The core stage’s intertank area housed three inertial guidance platforms (KI21-36) developed by NPO Rotor in Moscow and based on similar systems built for the 15A35 (SS-19 “Stiletto”) and 15A18 (SS-18 “Satan’’) missiles. Pre-launch alignment of the booster platforms took place with an optical system (17Sh14) (precision 7′) and that of the core stage platforms with an automatic system (17Sh15) (precision 45”) The automatic system consisted of three instruments mounted on a black plate outside the intertank area of the core stage. The plate was detached from the core stage and retracted to the launch tower with less than a minute to go in the countdown after the final pre-launch alignment. Failure of the plate to properly disengage led to the abort of the first Buran launch attempt on 29 October 1988 [7].

With the N-1 failures fresh in their memories, Soviet designers went to great lengths to protect the rocket against the consequences of leaks and engine failures. There was a so-called Fire and Explosion Warning System, consisting of gas and fire detectors and a system to purge the tail sections of the core stage and boosters with nitrogen and extinguish fires with freon. This was activated both during the count­down and launch. Installed on the pad was a hydrogen burnoff system to eliminate hydrogen vapors exhausted into the RD-0120 engine nozzles during the start sequence. This differed from the hydrogen igniters on the Space Shuttle launch pads in that the hydrogen was burnt off well away from the engine nozzles [8].

Energiya was also equipped with a so-called Engine Emergency Protection System, comprising a wide range of sensors in the engine compartments to monitor pressures, temperatures, turbine rates, etc. In case an anomaly was detected, any of the engines could be shut down immediately before failing catastrophically. Depend­ing on the moment when the shutdown took place and the type of payload carried (an orbiter or unmanned payload canister), the flight control system could then decide on a further course of action. This could involve shutting down the diametrically opposed engine to continue controlled flight, increasing the burn time of the remain­ing engines to deploy the payload in a lower or even nominal orbit, initiating a return to launch site maneuver, guiding the rocket to a safe impact area, etc. This would not only ensure the safety of the crew, but also facilitate post-flight analysis of the failure. The system was designed to deal with over 500 types of anomalies and was said to be a major improvement over the analogous “KORD” system on the N-1 rocket.

The safety systems were not only used during launch countdowns and ascent, but also during bench tests of the RD-170 and RD-0120 engines and test firings of the core stage and strap-ons. The bench tests, especially those of the RD-170, showed that the Engine Emergency Protection System could not always respond to rapidly escalating problems such as turbopump burn-throughs or cracks in the turbopump rotors, a problem that had not been fully solved by the time Energiya made its two missions [9].

The two orbital maneuvering engines (Russian acronym DOM, also referred to as 17D12) were a further development of NPO Energiya’s 11D58 engine used in the Blok-D, an upper stage for the Proton rocket and later also employed by Sea Launch’s Zenit-3SL. Each having a vacuum thrust of 8.8 tons and a specific impulse of 362 s, they performed final orbit insertion, orbit circularization, orbit corrections, and the deorbit burn, and were also supposed to be activated in certain launch abort scenarios to burn excess propellant. A long-term objective was to use the DOM engines to provide additional thrust during a nominal launch, a technique that NASA introduced with the Shuttle’s OMS engines on STS-90 in 1998.

Usually, only one of the two was required for any given standard burn, with the other acting as a back-up. Simultaneous ignition of both engines was only required in launch emergencies. The DOM ignition process began with a 20-25 second burn of two primary thrusters to force the LOX and sintin out of their tanks. The engine used a closed-cycle scheme, re-routing the gases used to drive the turbopump to the combustion chamber. During each burn the propellant tanks were pressurized with gaseous helium. In order to save helium, gaseous oxygen was used to pressurize the LOX tank for the deorbit burn. The engine nozzles could be gimbaled up to 6 degrees in two axes (pitch and yaw) for thrust vector control. Each DOM was designed to be ignited up to 15 times during a single mission.

A nominal re-entry could be initiated whenever Buran’s ground track carried it over or near one of three runways available in the Soviet Union. The primary landing site was at Baykonur, with back-up sites available in the Soviet Union’s Far East and in the Crimea (see Chapter 4). The ship had a maximum cross-range capability of 1,700 km, but that was only required for an emergency return back to Baykonur after a single revolution when the vehicle was launched into a polar orbit. For more common inclinations below 65° a cross-range capability of 1,050 km was sufficient.

Deorbit preparations began with the crew realigning the GSPs, retracting an­tennas, closing the payload bay doors, and preparing hydraulic systems for re-entry. When descending from an altitude of 250 km, about one hour would elapse between the deorbit burn and touchdown, with the vehicle covering a total distance of about 20,000 km and reducing its speed from Mach 25 to zero. After the deorbit burn, performed with the help of the DOM engines, Buran needed some 25 minutes to reach the official boundary between space and the atmosphere at 100 km, at which point it was still at a range of 8,500 km from the runway. It was only then that the three Auxiliary Power Units were activated.

The return through the atmosphere was divided into three phases: “Descent”, “Pre-Landing Maneuvering”, and “Approach and Landing”. These correspond roughly to the three major phases of a Shuttle Orbiter return (“Entry”, “Terminal Area Energy Management”, and “Approach and Landing”).

“Descent” was the hypersonic phase of the re-entry (Mach 28-Mach 10 at 100km-20km altitude) where the vehicle was exposed to the highest temperatures and achieved maximum cross-range. The flight control system guided the orbiter through a tight corridor limited, on the one hand, by altitude and velocity require­ments (in order to make the runway) and by thermal constraints, on the other hand. Buran’s angle of attack was kept at a high value (39°) during most of this phase to keep the temperatures within acceptable limits, while roll reversals were used to bleed off air speed and thus reduce kinetic energy. When the vehicle reached Mach 12, the angle of attack was gradually lowered from 39° to 10° to increase the lift-to-drag ratio. As the atmosphere thickened, the ship gradually transitioned from 20 aft attitude control thrusters to conventional aerodynamic control surfaces. The thrusters were used up to an altitude of 10 to 20 km. Between altitudes of about 80 and 50 km Buran was enveloped in a sheath of ionized air that blocked all communications with the ground. After coming out of the blackout, the ship’s RDS system began beaming pulses to transponders on the ground to furnish the on-board computers with range data. Azimuth and range data from the more traditional RSBN beacon navigational aid system were only used as a back-up to the RDS data.

During the “Pre-Landing Maneuvering” phase (Mach 10-Mach 2 at 20 km-4km altitude) Buran gradually transitioned from hypersonic to supersonic speeds and lined itself up with the runway for the final approach and landing. At this stage it intercepted one of two so-called “Heading Alignment Cylinders’’ (TsVK), imaginary cylinders to align the vehicle with the runway. Which of the two was chosen mainly depended on the wind direction. By the end of this phase Buran reached an “entry point’’ 14.5 km from the runway to begin the final descent. Primary navigational input throughout this phase still came from the RDS rangefinder system, backed up by the RSBN for azimuth and range data and by the RVB high-altitude altimeter and

SVSP air data system for altitude data. The SVSP probes were deployed at an altitude of 20 km.

The Approach and Landing phase saw the orbiter moving from hypersonic to subsonic speeds and finally coming to a stop on the runway. It began with a steep glideslope of —17° to —23° degrees (depending on landing mass), allowing the ship to correct any small trajectory errors it still had at the entry point. At an altitude of 400-500 m a pre-flare maneuver was started to position the vehicle for a shallow glideslope of —2° in preparation for landing. A final flare at an altitude of 20 m led to touchdown some 1,000 m past the runway threshold at a speed between 300 and 330 km/h. Wind speed limits were 5m/s for tail winds, 20m/s for head winds, and 15m/s for crosswinds. After touchdown, speed was brought down to zero by the brake chutes and the main gear brakes, with the speed brakes only used in manual landings. Steering during roll-out was provided by the nose gear steering system and by differential braking. The maximum roll-out distance was 1,800 m. The navigation aids during Approach and Landing were the RMS microwave system for altitude and azimuth, the RDS rangefinder system for range and the RVM low-altitude altimeter for altitude.

The landing could be performed in automatic, flight director, or manual mode. Automatic mode was the preferred mode even for manned missions (see Chapter 7). Flight director systems, also used in aviation, provide visual indications on the pilots’ displays of what the autopilot would want to do if it were flying the vehicle under the current settings. In other words, the pilots fly the vehicle manually but are guided by the autopilot. Simulations showed that the use of this mode throughout descent would be monotonous and tiring and should be restricted to the final approach and landing, especially if visibility was poor. Moreover, this mode did not give the crew the necessary psychological comfort because it could not always anticipate unexpected events. In manual control the pilots themselves determined the flight path using information on the expected touchdown point and remaining energy and also by relying on navigational aids, outside visual clues, and data uplinked from the ground. If all that information was available to them, they could switch to manual mode at an altitude of about 20 to 30 km. In emergency situations they could land the vehicle using only navigational aids or information provided by Mission Control [30].