Category Energiya-Buran

KB Energomash, situated in the Moscow suburb of Khimki, was responsible for the design of the RD-170 engines of the Blok-A strap-on boosters. The bureau originated as OKB-456 in 1946 and was headed from the beginning by Valentin P. Glushko, who had begun his career as a rocket engine designer at the Gas Dynamics Laboratory in Leningrad in 1929. OKB-456 developed all the engines for the Soviet Union’s early ballistic missiles and derived space launch vehicles. In January 1967 OKB-456 was renamed KB Energomash (KBEM). In May 1974 it was united with the old Korolyov bureau (then named TsKBEM) to form the giant conglomerate NPO Energiya. While Glushko became the new head of Korolyov’s former empire, he appointed Viktor P. Radovskiy as chief designer of the Energomash subdivision. On 19 January 1990, one year after Glushko’s death, Energomash again separated from NPO Energiya and

became known as NPO Energomash. The following year Radovskiy was replaced by Boris I. Katorgin, who led the organization until 2005.

KB Energomash had a so-called “Experimental Factory”, originally known as “Experimental Factory 456” and renamed OZEM in 1967. It produced test models and the first flightworthy versions of new rocket engines. However, since the factory’s production capabilities were relatively limited, serial production of engines was usually farmed out to other organizations. Being the most complex engines designed yet, the RD-170 and its Zenit cousin (the RD-171) were no exception. Even for the experimental engines the manufacture of the combustion chamber was entrusted to the “Metallist” factory in Kuybyshev, which had already built combustion chambers for the N-1 rocket. The production of the chambers was overseen by the “Volga Branch’’ of Energomash in Kuybyshev.

In 1978 it was decided that serial production of the RD-170 and RD-171 would eventually be transferred to PO Polyot in the Siberian city of Omsk, which until then had specialized in building small satellites and the 65S3/Kosmos-3M launch vehicle. Polyot’s task was dual. It delivered components to the KB Energomash factory for the engines manufactured there and at the same time produced complete engines itself. PO Polyot’s first RD-170 rolled off the assembly line in 1983 and during that same year KB Energomash set up a branch in Omsk, mainly to produce the blueprints necessary for serial production of the engines. Between 1983 and 1992 PO Polyot manufactured eleven RD-170 and about forty RD-171 engines. While many of those were used in test firings, none of them was ever completely installed on an Energiya or Zenit rocket. However, virtually all individual components of these engines were later used in the assembly of RD-171 engines for the Sea Launch version of Zenit. Energomash’s Experimental Factory produced its last RD-170 in 1990. Its director during the Buran years was Stanislav P. Bogdanovskiy (1968-1992) [4].

Buran had two back-up landing sites, an “eastern” site not far from the Soviet Pacific coast and a “western” site in the Crimea. The eastern site was situated south of Lake Khanka very close to the small town of Khorol, a little over 100 km north of Vladivostok. The aerodrome was originally used in the 1960s as a temporary home base for the Tu-95MR bomber and later hosted Tu-95RTs Navy reconnaissance planes, Tu-16 planes belonging to the Pacific fleet, and fighter jets of the Air Defense Forces. In the 1980s it was modified for its role in the Buran program by lengthening the existing runway and installing equipment of the Vympel navigation system. The runway was 3.7 km long and 70 m wide. The western site was located near the town of Simferopol in the Crimea and featured a 3.6 km long and 60 m wide runway. There is conflicting information on whether the two sites were ready in time for Buran’s maiden mission in November 1988, but they should have been available for the first manned missions in the early 1990s [18].

Also considered was the possibility of landing Buran on ordinary runways, not specially adapted for the orbiter and not equipped with the navigation facilities needed to assist in a hands-off landing. A requirement formulated for Buran’s test pilots was to land Buran on such runways at nighttime without any illumination [19].

The lead research institute for aerodynamic, dynamic, and structural testing of launch vehicle components was the Central Scientific Research Institute of Machine Building (TsNIImash) in Kaliningrad. Studies of the aerodynamic behavior of the Energiya-Buran stack during various phases of the launch and also of the strap-ons after separation were conducted in several wind tunnels and saw the use of more than 80 scale models in about 11,000 experiments overall. Dynamic tests involved the use of 1: 10 and 1: 5 scale models of the Energiya-Buran system. Individual RD-0120 and RD-170 engines were subjected to vibration tests.

For structural testing of core stage components, the Russians were forced into a different strategy than NASA. The US space agency built full-size test articles of the External Tank’s LOX tank, LH2 tank, and intertank, which underwent individual structural load tests at the Marshall Space Flight Center in 1977. However, the Russians did not have the facilities to do the same with their core stage elements

and therefore elected to do their structural tests (called “21”) using smaller pieces of the tanks. These included top and bottom sections of the LH2 tank joined together, a half-size LOX tank, an intertank section with parts of the LOX and LH2 tanks attached, a tail section with a mock-up LH2 tank bottom section attached, and a shortened LH2 tank. All these sections were manufactured at the Progress plant in Kuybyshev and tested either there or at TsNIImash. For the TsNIImash tests, which also included thermal testing, the sections were transported from Kuybyshev to the Moscow area by barge, the same one used to transport Buran orbiters from Tushino to Zhukovskiy. Subsequently, they were picked up by heavy MI-10 helicopters and airlifted to Kaliningrad.

Another institute playing a key role in Energiya-Buran testing was the Scientific Research Institute of Chemical Machine Building (NIIkhimmash) at Novostroyka near Zagorsk (now Sergiyev Posad), some 100 km north of Moscow. Having origin­ated in 1948 as a branch of the NII-88 rocket research institute and independent since 1956, this remains the largest test facility for rocket engines on Russian territory.

It has over 50 test stands for rocket engines and their components and also several thermal vacuum chambers and other facilities for spacecraft testing. When it came to simulating conditions during launch, one of NIIkhimmash’s main tasks was to study the acoustic environment during lift-off. This was done using a test stand called SOM-1 in which a 1:10 model of Energiya-Buran sat on a simulated launch table and was lifted several meters above the ground by a special hydraulic system. Another facility at Nllkhimmash (“Stand R”) simulated the separation of the Blok-A strap-on boosters from the core stage using full-scale mock-ups of the boosters.

Also involved in simulating the lift-off environment was the Scientific Research Institute of Chemical and Building Machines (NIIKhSM), situated in Zagorsk itself. This had a test stand called SVOD, which featured another 1: 10 model of Energiya – Buran equipped with small solid-fuel rockets to mimic conditions during lift-off. NIIKhSM was also responsible for testing various launch pad systems such as the sound suppression water system and the fueling systems.

The Russians never carried out full-fledged fueling tests of core stage propellant tanks until full-scale models of the Energiya rocket were placed on the launch pad at Baykonur in the mid-1980s. This also differed from the situation in the United States, where NASA did fueling tests of complete External Tanks at the Marshall Space Flight Center in 1977. In order to save costs, the Progress factory only built a test stand designed to fill the tanks with liquid nitrogen at temperatures of —180°/—190°C, which was significantly lower than the —255°C required for liquid hydrogen [1].

Heat shield testing went much further than the experiments with the OK-TVA and OK-TVI models at TsAGI and NIIkhimmash. Smaller pieces of thermal insulation were tested in plasma generators at TsNIIMash in Kaliningrad, the Institute of Mechanical Problems in Moscow (IPMekh), and other test stands at NPO Molniya in Tushino and the Siberian Scientific Research Institute of Aviation (SibNIA) in Novosibirsk. Besides that, Ilyushin-18D and MiG-25 aircraft were used to test tiles and felt reusable surface insulation at subsonic and supersonic speeds. The thermal insulation was installed on areas of the aircraft that were subjected to the highest dynamic pressure and acoustic loads from the engines. NASA similarly tested Shuttle tiles on F-15 Eagle and F-104 Starfighter jets.

Since the US Space Shuttle’s Thermal Protection System was very similar to that of Buran, the Russians probably watched the first Shuttle missions with more than casual interest. In a 1984 National Intelligence Estimate on the potential for the transfer of US space technology to the Soviet Union, the CIA concluded that the Soviets had benefited considerably from surface heating data from the STS-2 and STS-3 missions publicly released by NASA in June 1982. The report quoted NASA officials as estimating that the data could save the Soviets the equivalent of $750 million in R&D cost and considerably reduce development time [16].

Whether that was true or not, it didn’t stop the Russians from pursuing their own test program. Unlike NASA, the Russians had the unique opportunity to test Buran’s heat-resistant materials during actual re-entries from orbit using scale models of the canceled Spiral spaceplane. In the late 1960s and early 1970s they had already flown
scale models known as BOR (Bespilotnyy orbitalnyy raketoplan or “Unmanned Orbital Rocket Plane”) on suborbital trajectories. These were BOR-1 (a wooden mock-up), BOR-2 (a 1:3 scale model), and BOR-3 (a 1: 2 scale model) with ablative heat shields. In 1975 plans were completed at the Flight Research Institute (LII) for an orbital test bed known as BOR-4, which was a 1: 2 scale model of Spiral. Even though the future of the Spiral program was very much in limbo by this time, BOR-4 test flights would also have been applicable to the giant lifting body proposed by NPO Molniya in early 1976. When that was dropped in favor of the delta-wing Buran, it looked as if BOR-4 would remain on the drawing boards forever.

However, the Russians soon realized that in order to test the heat shield they did not necessarily need a vehicle that exactly copied Buran’s outlines. The most impor­tant thing was to ensure that the heat-resistant materials would be exposed to the same type of temperatures for about the same period of time. Moreover, the nose section of the BOR-4 test vehicle did more or less match the contours of Buran’s nose section. Therefore, it was decided in 1977 to develop two types of scale models in support of the Buran program:

– BOR-4, a 1: 2 scale model of the Spiral spaceplane, to test Buran’s heat shield materials.

– BOR-5, a 1: 8 scale model of Buran, to test its aerodynamic characteristics.

Design

Just like the Spiral spaceplane, BOR-4 was a flat-bottomed lifting body with a vertical fin and foldable wings. It was 3.859 m long with a launch mass of about 1,450 kg

and a landing mass of 795 kg. The BOR-4 vehicles made it possible to test the three main types of thermal insulation used on Buran—namely, tiles, felt reusable surface insulation, and reinforced carbon-carbon. Black tiles (using both the TZMK-10 and TZMK-25 substrate) covered the belly, white tiles (with TZMK-10 substrate) were installed on the sides, and ATM-19 felt insulation protected the upper part of the vehicle. Carbon-carbon GRAVIMOL material was used only on the nosecap, since the wing leading edges were too thin for installation of such material.

The tiles were not applied directly to the BOR’s airframe, but to a thin layer of aluminum of the same composition as that used in Buran’s airframe. In between this aluminum layer and the actual airframe was an ablative heat shield material (PKT-FL) that had been planned for the original BOR-4 vehicle to be flown in the framework of the Spiral program. This provided the necessary redundancy in case any of the Buran heat shield material burnt through during re-entry. The area between the nosecap and the airframe was filled with insulating material made of heat-resistant fibers. Since the wings were much thinner than the rest of the airframe, they were filled with a porous felt material impregnated with a water-based substance. Evaporation of that substance provided enough cooling for the wing during re-entry in case the Buran thermal protection material proved ineffective.

BOR-4 was equipped with 150 thermocouples, installed mainly on the airframe and just under the coating of some of the tiles. In addition to that it had acceler­ometers, angular velocity sensors, pressure sensors, and sensors that indicated the position of the wings. Information obtained from the sensors was recorded on board and sent back to earth in “packages” to tracking ships and also to a ground station during re-entry.

On 26 October the State Commission in charge of test flights of the Energiya-Buran system met at Baykonur to set a launch date for the mission. Such commissions were set up routinely in the Soviet Union to oversee launch preparations for specific projects. The composition of the Buran State Commission reflected the importance attached to the flight. Established in December 1985, it was headed by none less than the Minister of General Machine Building himself, initially Oleg Baklanov, replaced in April 1988 by Vitaliy Doguzhiyev. In all, the commission numbered 44 people, including 9 ministers, 10 deputy ministers, the President of the Academy of Sciences, leading Ministry of Defense officials, and several general and chief designers (Glushko, Gubanov, Semyonov, Lozino-Lozinskiy, Konopatov, Radovskiy, Barmin, Andryushenko, and Lapygin). The “technical leader” of the State Commission, somewhat comparable with a “launch director” in the US, was NPO Energiya head Valentin Glushko. However, the 80-year old Glushko, who had suffered a stroke only months earlier, was recovering in a Moscow hospital and had to be replaced by his deputy Boris Gubanov. Final preparations at the pad were the responsibility of the military teams of the so-called 6th Test Directorate under the leadership of Major – General Vladimir E. Gudilin.

Despite last-minute concerns over problems with another ODU test firing near Leningrad on 19 October, the commission declared Energiya and Buran ready to go. With meteorologists predicting excellent weather conditions, the commission set the launch for 29 October at 6:23.46 Moscow time (8:23.46 local time at Baykonur, 3: 23.46 gmt), a decision announced by TASS the same day. Lift-off was timed such that the launch could be observed by the orbiting crew of the Mir space station (Vladimir Titov, Musa Manarov, and Valeriy Polyakov). Mir would be a minute or two short of a Baykonur flyover at lift-off time, allowing the crew to watch virtually the entire launch. Mir’s orbit had been adjusted on 16 October to permit close coordination during the brief Buran flight, including launch and retrofire. However, the observations from Mir were not a strict requirement and the launch was not likely to be scrubbed if that objective could not be met. The main constraint for the launch window was to ensure a landing at Baykonur well before local sunset, ideally around noon. Speaking to reporters later that same day, Doguzhiyev did not hide the tension felt around the cosmodrome:

“No one is indifferent or passive at the cosmodrome… Behind outward calm

there is much nervous pressure. Even we [State] Commission members find it

difficult to answer questions’’ [41].

Among the final tasks to be accomplished at the pad in the last three days prior to launch was the retraction of the 145 m high rotating service structure, a relic of the N-1 days, which was now moved back to its parking position, fully exposing Buran to the elements. Strict safety measures were in place to protect personnel against any potential accidents on the pad. The region around the launch complex was divided into four safety zones. Zone 1 (2 km radius around the pad) was completely evacuated 12 hours before launch. By that time any personnel involved in final countdown operations were required to go to hermetically sealed and heavily armored bunkers, from where all final launch preparations (including fueling) were controlled. The bunkers were said to be capable of surviving impacts of rocket debris. Zone 2 (5 km radius) was cleared of personnel at T — 8 hours as final preparations got underway for loading of liquid hydrogen. Zones 3 and 4 (8.5 km and 15 km radius) were evacuated at T — 4 hours and T — 3 hours to ensure safety of people in case of an explosion during engine ignition and during the early stages of ascent. The rules were much stricter than at the Kennedy Space Center, where people are allowed to watch Shuttle launches in open air from a distance of just about 5 km.

Two days before the planned launch, concern arose over some equipment in Buran’s automatic landing system. VNIIRA, the design bureau in charge of the system, requested installing back-up equipment aboard the orbiter and first test that aboard a Tu-134B aircraft. Although this required activation of all the navigation and landing support systems at the Yubileynyy runway, the landing tests were authorized given the potentially catastrophic consequences of a failure in the auto­matic landing system. The back-up equipment was successfully tested during several approaches to the Yubileynyy runway on 28 October.

On the eve of the launch, Soviet officials backed down from their earlier promises to provide live television coverage of the launch and were now planning to show the recorded launch 35 minutes after the event. The landing would not be carried live either. As expected, the planned launch time of 3: 23 gmt went by without any comment from the Soviet media. Anxiety grew as nothing was heard in the following 45 minutes or so. Finally, shortly after 4:00 gmt, TASS broke the silence by issuing a brief two-line statement:

“As has been reported earlier, the launch of… Energiya with the orbital ship Buran had been planned for 6.23 Moscow time on 29 October. During pre­launch preparations a four-hour delay of the launch has been announced.’’

This now theoretically put the launch time at 7: 23 gmt, raising serious doubts among observers that the launch would take place that day at all. According to the original flight plan, landing would have taken place at 6: 49 gmt, but the launch delay would now move this to around 11: 00 gmt (16: 00 local time at Baykonur), close to sunset. At around 7: 30 gmt, shortly after the rescheduled launch time, TASS reported what had been obvious all along:

“During final launch preparations for the rocket carrier Energiya with the orbital ship Buran there was a deviation in one of the launch support systems. As a result of this an automatic command was issued to stop further work. At the present time work is underway to eliminate the problems. A new launch date and time will be announced later.’’

It wasn’t until later in the day and in press interviews the following days that officials began providing details about the exact cause of the scrub. It turned out the countdown had been halted at T — 51 seconds because a platform had failed to properly retract from the rocket. When it came to describing the exact nature of that platform, Soviet space officials, not used to communicating problems to the media, did a poor job. Talking to a Pravda reporter, Vladimir Gudilin, the head of launch pad operations, said:

“51 seconds before the launch one of the servicing platforms did not move away from the rocket. To be more precise, it visually moved away, but the signal confirming this did not reach the computer checking the launch readiness of all systems. Until the last seconds this platform holds an aiming platform, controlling the gyroscopes. The computer [did not receive the retraction signal] and instantaneously stopped the launch program” [42].

Despite the fact that the Soviet orbiters had long been mothballed by the time ISS construction began, one piece of Buran technology does play a vital role in station

operations. This is the Androgynous Peripheral Docking System (APDS—Russian acronym APAS), a Russian-built docking mechanism that allows Space Shuttles to dock with the US-built Pressurized Mating Adapters (PMAs) on the ISS “node” modules. Built at RKK Energiya under the leadership of Vladimir Syromyatnikov, the first APAS (APAS-75) was developed back in the 1970s for the Apollo-Soyuz Test Project. A modified version (APAS-89) appeared in the 1980s to enable Soviet orbiters to dock with the axial APAS docking port of Mir’s Kristall module. In the end, Buran never flew to Mir and the Kristall APAS docking port was used only once by Soyuz TM-16 in 1993.

In July 1992 NASA initiated the development of the Orbiter Docking System (ODS) to support Shuttle flights to Mir. Mounted in the forward end of the payload bay, the ODS consists of an external airlock, a supporting truss structure, and an APAS docking port. While the first two elements were built by Rockwell, the APAS was manufactured by RKK Energiya. Although Energiya’s internal designator for the Shuttle APAS is APAS-95, it is essentially the same as Buran’s APAS-89. While the ODS was slightly modified for Shuttle missions to ISS, APAS remained unchanged. There was even a suggestion to launch Buran to Mir to test the docking system prior to the beginning of the Shuttle-Mir flights [31].

The APAS consists of a three-petal androgynous capture ring mounted on six interconnected, ball screw shock absorbers that arrest the relative motion of the two vehicles and prevent them from colliding. The APAS-89 differs from APAS-75 in several key respects. It is much more compact (although the inner egress tunnel diameter is more or less the same), has twelve structural latches rather than eight, the guide ring and its extend/retract mechanism are packaged inside rather than outside the egress tunnel, and the three guide petals are pointed inboard rather than outboard [32].

Russian plans to sell their entire Buran Docking Module to NASA fell through, but its design did serve as the basis for the construction of the Russian Pirs airlock module, docked to ISS in September 2001. This retains the central part of the adapter’s spherical section (2.55 m in diameter). Mounted to its aft end is a small section of the Buran airlock’s cylindrical tunnel (without the extendable part) and attached to the front end is the forward part of a Soyuz-TM/Progress-M orbital module. The design was more complex than that of the Docking Module of Mir (316GK), which did not have to be used as an airlock and was merely an extension to the Kristall module to facilitate Shuttle dockings [33].

In the course of Energiya’s history several studies were made of configurations in which the core stage was flanked by just two strap-ons, providing payload capacities of between about 30 and 60 tons. The first version, called RLA-125, was proposed in 1976 and another one known as Groza (“Thunderstorm”) appeared in the mid-1980s. Groza, using a standard core stage with four RD-0120 engines and two strap-ons, had a reported payload capacity to low orbit of up to 63 tons. The Cargo Transport Container strapped to the side would be a downsized version of that developed for Buran-T. Groza required virtually no modifications to the existing Energiya pads. All that needed to be done was to bolt the strap-ons more firmly to the pad because the rocket would be more susceptible to high winds. Because of this, launch weather rules were also tightened.

On 25 December 1984 the Soviet government released a major decree on rocket and space systems to be developed in the period 1986-1995. One of these was planned to be a series of rockets with payload capacities between 30 and 60 tons, although it is not clear what payloads exactly were being considered. Three systems were adopted for parallel studies: a modernized version of the Proton rocket, several heavier versions of the Zenit (11K37), and Groza. As mentioned earlier, these boosters were to use a standardized series of cryogenic upper stages, Shtorm for Proton and Vikhr for the 11K37 and Groza.

The preliminary design for Groza was completed in December 1985. However, on 18 August 1988 the Ministry of General Machine Building ordered NPO Energiya to modify the rocket in order to make it compatible with more realistic payloads of between 25 and 40 tons. This made it necessary to reduce the number of RD-0120 engines to one or two and hence make the core stage smaller. The first idea was to reduce the diameter of the core stage to 4.1 m or 5.5 m and lower the propellant mass to between 200 and 450 tons. However, since this would have required different manufacturing techniques, it was decided to retain the standard Energiya core stage diameter of 7.7 m. By late 1989 engineers were focusing on a version with one RD-0120 engine and a propellant mass of around 240 tons. With the core stage (called Blok-V) only about half as high as that of Energiya, the payload had to be stacked on top rather than strapped to the side. At the intersection between the core stage and the payload bay the rocket would taper off to a diameter of 6.7 m, the same as that of the 14S70 Cargo Transport Container of Buran-T. With a length of 25 m,

the payload bay was probably almost identical in dimensions to the Cargo Transport Container for Groza. The concept was approved by the Council of Chief Designers on 19 July 1990. Initially called Neytron (“Neutron”), the new rocket eventually became known as Energiya-M.

Four configurations were considered for the payload section, one in which the satellite would occupy the entire bay and have its own engine system (N-11) and three where the satellite would be attached to various upper stages (N-12, N-14, and N-15).

The N-12 was a Blok-DM modification with an engine known as the 11D58MF and was also planned for use on Zenit, Proton, and the original Angara. It allowed the rocket to place 29 tons into low Earth orbit or up to 3 tons into geostationary orbit. The N-14 was a Blok-DM modification with the standard 11D58M engine and was identical to the second stage of the 204GK upper-stage combination planned for Buran-T. It was capable of delivering a 5.5-ton payload to geostationary orbit. The N-15, able to launch 6.5 tons into geostationary orbit, was a LOX/LH2 upper stage but no further information on this is available. It is known that in 1992 work got underway on a LOX/LH2 upper stage known as Yastreb carrying the RO-97 engine of KBKhA. This stage was primarily intended for Proton, Zenit, and Angara, but with slight modifications could also be mounted on Energiya-M. However, it was smaller than the N-15 and also had its propellant tanks configured differently.

As early as 1990 a mock-up of Energiya-M was ready for tests at Baykonur. It was placed both on the UKSS pad and Energiya-Buran pad 37. It was only afterwards, on 8 April 1991, that the government issued a decree ordering NPO Energiya, KB Yuzhnoye, and KB Salyut to come up with competing proposals for boosters in the 25 to 40-ton payload range. This basically was a repeat of the order given in the 25 December 1984 decree, although in a somewhat lighter payload class. KB Salyut and KB Yuzhnoye had apparently also been optimizing their Proton and 11K37 designs. Eventually, on 6 July 1991 the Ministry of General Machine Building opted for Energiya-M. Between 1991 and 1993 preparations were made for starting production of flight models.

During that period, NPO Energiya worked out plans to launch a 30-ton space – plane (OK-M2) atop the rocket and also to turn the two strap-ons into reusable flyback boosters, something which appears to have been studied as early as 1989. Another idea was to launch the rocket from an ocean-based platform near the equator. This would not only allow Energiya-M to loft heavier payloads, but would also resolve the political problems associated with flying it from Baykonur, which became foreign territory after the collapse of the Soviet Union. One exotic mission considered for the ocean-launched Energiya-M was to deposit radioactive waste into heliocentric orbits, eliminating the risks involved in launching such dangerous payloads over populated territories. These studies formed the basis for the creation of the international Sea Launch venture, which would eventually use the three-stage Zenit rocket.

Despite the fact that Energiya-M used existing hardware and infrastructure and outperformed rockets like the Titan-4 and Ariane-5, it was ahead of its time. At the time there was simply no demand for the types of satellites that the rocket could place into orbit. On 15 September 1992 the Russian government started yet another com­petition to develop a family of even lighter rockets, which would eventually evolve into the Angara series. By late 1993 government funding for Energiya-M was stopped, with Russian Space Agency officials stating there was no demand for the rocket on the market. The following year NPO Energiya made an ultimate attempt to attract Western customers to Energiya-M and other Energiya variants, but to no avail. The prototype Energiya-M still stands today inside the Dynamic Test Stand at Baykonur [66].

The plans underwent further changes with the inception in the mid-1980s of the more capable An-225 Mriya carrier aircraft. Although conceived in the first place to transport Buran and elements of the Energiya rocket from the manufacturers to the Baykonur cosmodrome, designers may have had air-launch capability in the back of their minds from the outset.

The Mriya-based system was dubbed the Multipurpose Aerospace System (Mnogotselevaya aviatsionno-kosmicheskaya sistema or MAKS). The rocket was now replaced by an expendable external fuel tank (VTB), perched on top of which was either a reusable spaceplane (MAKS-OS) or an expendable unmanned cargo canister (MAKS-T). Also envisaged was a fully reusable unmanned winged cargo carrier with integrated propellant tanks (MAKS-M).

The OS was a 26-ton, two-man spaceplane with a length of 19.3 m, a height of 8.6 m, and a wingspan of 8.6 m. As on Spiral and BOR, the wings could be folded back for re-entry. The thermal protection system was the same as that of Buran, although a different material was needed for the much thinner wing leading edges. Behind the crew compartment was a 2.8 x 6.8 m payload bay. The original plan was for the spaceplane to have three Kuznetsov NK-45 LOX/LH2 main engines with a vacuum thrust of 90 tons each. That idea was turned down in favor of a tripropellant LOX/LH2/kerosene engine called RD-701, developed at NPO Energomash on the basis of the RD-170. Although this lowered the mean specific impulse, it still resulted in better performance because the external tank became much lighter by reducing the amount of liquid hydrogen, which is a low-density fuel taking up a lot of volume.

The RD-701 is a twin-chambered, staged, combustion cycle engine. Each chamber has a pair of turbopumps. One pump processes liquid oxygen and kerosene, which is turned into an oxygen-rich gas at 700 atmospheres after passing through a preburner. The other pump feeds liquid hydrogen to the main combustion chamber at ambient temperatures. The RD-701 has two modes of operation, combining first and second-stage engine characteristics in one package. During the initial phase it burns 81.4 percent liquid oxygen, 12.6 percent kerosene, and 6 percent liquid hydro-

gen, producing a total thrust of 400 tons with a specific impulse of 415 s. Then it switches to a combination of just liquid oxygen and hydrogen, with the thrust decreasing to 162 tons, but the specific impulse climbing to 460 s, helped by the deployment of a nozzle extension.

A typical MAKS-OS launch profile would see Mriya climb to an altitude of 9 km and assume the proper pre-launch attitude. The spaceplane would then ignite its main engine while still riding piggyback on the aircraft, making it possible to check its performance before separation. Some ten seconds later the 275-ton combination of spaceplane and external tank would be released from the Mriya to begin the trip to orbit. The engines would shut down before the spaceplane reached orbital velocity, allowing the external tank to burn up over the ocean across the world some 19,000 km from the launch point. The OS would then perform two burns of its two hydrogen peroxide/kerosene orbital maneuvering engines to place itself into orbit.

The basic version of the OS was designed to launch and retrieve small and medium- size satellites. Payload capacity was 8.3 tons to a 200 km orbit with a 51° inclination and 4.6 tons back to Earth. For space station missions there were two configurations. In one of them (TTO-1) the payload bay would house a small pressurized module capable of carrying four passengers plus cargo. This would be used for crew rotation or rescue missions, although the latter required additional fuel supplies for quick maneuvering. In the other (TTO-2) the payload bay would remain unpressurized and carry structures such as solar panels, antennas, or propellant tanks for refueling a space station. In both configurations a docking adapter was installed just behind the crew compartment. Also considered was an unmanned OS without a crew compart­ment and with a slightly enlarged cargo bay to fly heavier payloads (9.5 tons into a 200 km, 51° inclination orbit). Before committing MAKS-OS to flight, NPO Molniya planned to fly a suborbital unmanned demonstrator (MAKS-D). This would have the same size and shape as the OS, but would be equipped with a single RD-120 Zenit second-stage engine fed by propellant tanks in the payload bay.

In the MAKS-T configuration the OS was replaced by an unmanned cargo canister equipped with an RD-701 tripropellant engine and an upper stage for inserting payloads into the proper orbit. Maximum payload capacity was 18 tons to a 200 km, 51° inclination orbit, and 4.8 tons to geostationary orbit. For geo­stationary missions the Mriya would fly to the equator to make maximum use of the Earth’s eastward rotation and be refueled in flight.

MAKS-M was a fully reusable, unmanned, winged cargo container with integrated propellant tanks, designed to deliver payloads to low orbits (5.5 tons to a 200 km, 51° orbit). Situated in between the propellant tanks was a cargo bay slightly larger than that of the OS. An earlier version of this (VKS-D) had the cargo bay on top of the propellant tanks. NPO Molniya designers even floated the idea of transforming VKS-D into a suborbital intercontinental passenger plane capable of carrying 52 passengers to any point on the globe within 3 hours at a price of $40,000 per ticket.

NPO Molniya had plans to further upgrade the MAKS system by fitting the Mriya with more powerful NK-44 engines and eventually by replacing Mriya with a giant twin-fuselage triplane called Gerakl (“Heracles’’) with a phenomenal 450-ton cargo capacity. A similar plane had already been studied for air launches in the early 1980s under the name System 49M. In the even more distant future the hope was to finally realize the old Spiral dream by developing an air-launched system based on a hypersonic carrier aircraft (VKS-G) [6].

The RLA concept fitted well in a new philosophy to replace the existing fleet of Soviet launch vehicles by a new generation of rockets. By the early 1970s the Soviet Union was operating five basic types of fundamentally different launch vehicles each derived from a specific intermediate or intercontinental ballistic missile: the Kosmos and Tsiklon rockets (based on the R-12, R-14, and R-36 missiles of the Yangel bureau), the Vostok/Soyuz family (based on the R-7 missile of the Korolyov bureau) and the Proton (based on the UR-500 missile of the Chelomey bureau). While the R-7 based rockets used LOX/kerosene as propellants, all the others relied on storable hypergolic propellants.

Around the turn of the decade plans were being drawn up for new generations of satellites with more complex on-board equipment and longer lifetimes, requiring the use of heavier, more capable launch vehicles. By early 1973 a research program called Poisk (“Search”), conducted by the Ministry of Defense’s main space R&D institute (TsNII-50), had concluded that future satellites should be divided into four classes: “light” satellites up to 3 tons, “medium-weight” satellites up to 10-12 tons, “heavy” satellites (up to 30-35 tons), and “super-heavy” satellites (not specified). The last three classes were not served by the existing launch vehicles.

The new family of launch vehicles was to have two key characteristics. First, in order to cut costs to the maximum extent possible, it would use unified rocket stages and engines. Second, it would rely on non-toxic, ecologically clean propellants, with preference being given to liquid oxygen and kerosene. The reasoning behind this reportedly was that “the number of launches of [space rockets] would be much higher than the number of test flights of nuclear missiles with [storable] propellants.” What also may have played a role were a series of low-altitude Proton failures that had contaminated wide stretches of land at or near the Baykonur cosmodrome. The basic conclusions of the study were approved on 3 November 1973 at a meeting of GUKOS [45]. Although not stated specifically, the long-range goal of this effort seems to have been to phase out all or most of the existing missile-derived launch vehicles.

Initially, the primary focus apparently was on unifying the light to heavy class of rockets, because at the time these decisions were made super-heavy rockets and reusable shuttles were still a distant and vague goal. It would seem that three design bureaus were ordered to come up with proposals for such a family of launch vehicles under a competition called Podyom (“Lift”). Both Branch nr. 3 of TsKBEM in Kuybyshev (which became the independent TsSKB in July 1974) and Chelomey’s TsKBM put forward plans to refit their respective Soyuz and Proton launch vehicles with the Kuznetsov bureau’s LOX/kerosene NK engines originally built for the N-1 rocket. The former Yangel bureau in Dnepropetrovsk (now called KB Yuzhnoye and headed by Vladimir Utkin) also weighed the idea of using NK engines (which after all were around and had been tested), but in the end favored the new generation of LOX/ hydrocarbon engines being designed by Energomash [46].

Actually, by this time Yuzhnoye had been working for several years on a new medium-lift launch vehicle (11K77) burning storable propellants. In December 1969 it had been ordered by GUKOS to develop a new rocket capable of placing 8 tons into low polar orbits and 2 tons into highly elliptical Molniya-type orbits. The initial idea in 1970 was to build a three-stage rocket with 3.6 m diameter modules. The following year attention turned to a rocket derived from the bureau’s R-36M, a new ICBM that had been approved by a government decree in September 1969. By retaining the 3.0 m diameter of the R-36M’s rocket stages, no fundamentally new manufacturing techniques would be required. The 11K77 would now consist of a pair of R-36M first and second stages stacked on top of one another plus a newly developed third stage. In 1972 Yuzhnoye also designed a slightly less powerful rocket designated 11K66, essentially a two-stage R-36M with increased propellant load capable of orbiting 5.9 tons.

When Yuzhnoye made the switch to LOX/kerosene under the Podyom program in 1974, it opted for a vehicle maintaining the 3.0 m diameter of the rocket stages, but employing parallel staging. This version of the 11K77 would fly the single-chamber LOX/kerosene engines then being designed at Energomash. The second stage, acting as the core, would have a 130-ton thrust RD-125 engine, and the two first-stage modules flanking the core would each have three 113-ton thrust RD-124 engines. These engines had combustion chambers of roughly the same size and pressure as those of the R-36M first-stage engine. Payload capacity to low orbit was now 12 tons.

By early 1975 Energomash’s Department 728 had made enough progress on the powerful 600-ton thrust RD-123 for Yuzhnoye to incorporate it into the 11K77 design. This made it possible to replace the two modules of the 11K77’s first stage by a single module, although its diameter would have to be increased to 3.9 m, which was the maximum that could be transported by rail. The second stage would now be placed on top the first stage, turning the 11K77 into what the Russians call a “mono­block’’ booster. After a convoluted development path, the rocket had now acquired the configuration in which it later became known to the world as Zenit. It could also serve as the basis for a lighter rocket (11K55) and a heavier version (11K37), with the three covering the whole payload range from “light” to “heavy” (see Chapter 8) [47].

Being in the heavy to super-heavy class, Glushko’s RLA family was not part of the Podyom competition, but as plans for a large Soviet shuttle gained more support in 1975, so did the idea of unifying the first stage of the RLA rockets with that of the future medium-lift rocket. It is unclear if this consideration played a significant role early on in the Podyom competition. If it did, TsSKB and TsKBM had betted on the wrong horse by anticipating that whatever followed the N-1 would also carry NK engines, while Yuzhnoye had made the right choice by picking the new Energomash engines. However, the history of the 11K77/RLA unification is a complicated chicken-and-egg story, with sources differing on whether the initiative to unify the first stages came from Glushko or Utkin. At any rate, Yuzhnoye emerged as the winner of the Podyom competition in 1975, no doubt because its medium-lift rocket could now act as a test bed for the first stage of the rocket that would power the Soviet space shuttle to orbit.

The 11K77 is the only thing that ever came out of Podyom. Yuzhnoye’s proposed light-class and heavy-class rockets never flew and the whole idea of a standardized fleet of dedicated, environmentally clean space launch vehicles in the light to heavy class remained a distant dream, probably because it infringed too much on design bureau interests. In fact, most of the IRBM and ICBM-derived launch vehicles conceived in the 1960s continue to fly today, although another attempt is being made to develop a standardized rocket fleet under the Angara program (see Chapter 8).

The Energiya “Blok-A” strap-on boosters were largely designed and built by KB Yuzhnoye and its associated production facility in Dnepropetrovsk, although major elements were also supplied by NPO Energiya in Kaliningrad. Each strap-on booster was 39.4m high and had a maximum diameter of 3.9 m, dictated by railway trans­portation requirements. The wet mass was about 372 tons. The booster consisted of a nose section, an upper LOX tank, an intertank structure, a lower kerosene tank, and

a tail section with the gimbal-mounted LOX/kerosene RD-170 engine. The four boosters were numbered 10A, 20A, 30A, and 40A.

The nose section housed the avionics bay, which among other things contained an M4M computer that interacted with the core stage’s M6M central computer. Also installed in the nose section were flight data recorders, mounted in a special casing that protected them from the force of impact. Two of the four Blok-A boosters were equipped with radio beacons, enabling ground controllers to follow their trajectory after separation from the core stage.

The propellant tanks were made of an aluminum-magnesium alloy, with the walls being about 30 mm thick. The LOX and kerosene tanks had useful volumes of 208 m3 and 106 m3, respectively, holding approximately 220 tons of LOX and 80 tons of kerosene. The upper LOX tank fitted in a concave depression at the top of the kerosene tank and the LOX feed line passed right through the middle of the lower kerosene tank. There were vent and relief valves in the forward domes of both tanks. The kerosene fill and drain valves were in the aft dome of the kerosene tank, and the LOX fill and drain valves in the lower part of the LOX feed line. The LOX feed line also had a damper to suppress “pogo” oscillations.

Embedded in the lower part of the LOX tank were two rows of helium tanks for in-flight pressurization of both the LOX and kerosene tanks. The helium for the kerosene tank was supplied directly, while that for the LOX tank first passed through a heat exchanger in the lower engine compartment. Before launch the tanks were pressurized with ground-supplied helium. Electrical power for the boosters was provided by batteries.

There was a pair of strap-ons on either side of the core stage. Each pair was mechanically linked and jointly separated from the core stage, with the two boosters not splitting until about half a minute later. This was done in order to minimize the risk of any of the boosters hitting the orbiter after separation. The boosters were pyrotechnically separated from the core stage and subsequently activated 11 small solid-fuel motors (seven on the nose section and four on the tail section) to ensure safe separation from the core stage and payload. They came down some 425 km downrange from the launch site.

Although they were mechanically linked, the strap-ons operated independently from one another. The only electrical connections were with the core stage (one interface with 408 contacts for each booster). There were also twelve electrical, pneumatic, and hydraulic connections between each strap-on and the launch pad (eight for propellant, fluid, and gas supply and four electrical connections). The connections were between the nose section and the launch tower and the tail section and the launch table.

From the very beginning of the Energiya-Buran program the idea was that the strap-on boosters would be reusable. The degree of reusability mainly depended on the robustness of the RD-170 engine, which was certified to fly at least 10 missions. After having studied several schemes, designers opted for a horizontal landing system using parachutes, soft-landing engines, and a set of shock absorbers. Parachutes would be deployed from the forward and aft ends of each booster, orienting it to a horizontal attitude for descent. The plan had much in common with the landing

technique for the giant MTKVP lifting body that had been studied before the delta­wing concept of Buran was picked.

The strap-ons were designed from the beginning with special containers in their nose and tail sections to house the parachutes, other recovery systems, and control equipment. The containers were installed on the strap-ons flown on the two Energiya missions in 1987 and 1988 (6SL and 1L), but were loaded with instrumentation rather than recovery equipment. However, there were plans to demonstrate the recovery technique on the 2L mission with the GK-199 payload (see Chapter 8).

The boosters shared about 70 percent of their systems with the first stage of the Zenit rocket. The part of the booster that was largely similar to the Zenit first stage was known as the “modular part” (or 11S25) and included the propellant tanks, pressurization systems, and the engine compartment. The main differences with the Zenit first stage were in the gimbal axes of the engines and also in that the tank walls were slightly thicker because of the bending loads imposed by the strap-on config­uration. Elements unique to the strap-ons included the aft skirt surrounding the engine compartment (which needed to be compatible with the Energiya core stage), the entire nose section, and the parachute containers.

The original requirement was for the Zenit first stage to be reusable as well, but, if it was to use the same recovery systems and recovery zones as the Blok-A, the Zenit would need to have the same speed at the moment of first-stage separation as Energiya (1,800 m/s instead of 2,500 m/s). This would have made it necessary to make the second stage 38 tons heavier, reducing the rocket’s payload capacity to

an unacceptable 7 tons. A later idea to recover only the tail section with the engine was dropped as well because this was expected to produce a return on investment after only about 500 launches [3].