Control systems of the spacecraft "Buran"
Energia-Buran system on the launch pad. Photo by NPO Molniya
On November 15, 1988, the first and only orbital flight of the Soviet reusable spacecraft Buran took place. With the help of the Energia launch vehicle, the ship went into orbit, made two orbits and returned to Earth, after performing a horizontal landing at the airfield. The flight was fully automatic using unique onboard controls.
Difficult tasks
The development of a promising reusable rocket and space transport system, which resulted in the appearance of Buran, started in 1976. The specially created NPO Molniya, headed by General Designer G.E. Lozino-Lozinsky. Dozens of other scientific and design organizations were also involved in the project. For example, the Design Bureau of Chemical Automation (Voronezh) and the Research Institute of Mechanical Engineering (Nizhnyaya Salda) were responsible for the development of the propulsion system.
The program participants had to form the optimal image of the future ship, as well as implement it in the form of a full-fledged project. At the same time, it was necessary to solve a lot of technical problems of various kinds. So, in accordance with the terms of reference, the future Buran should have been made manned, but it was planned to use an autopilot with wide functions. The ship was supposed to have an automatic flight, descent and landing mode.
"Buran" after the first flight. Photo by NPO Molniya
In general, the development of control systems was divided into several main areas. The first involved the development of rudders and related systems for a glider designed to fly in the atmosphere. The second task was the creation of a complex of shunting engines for work in space. Within the framework of the third direction, on-board electronics, computing tools and software for them were developed. These funds were supposed to provide control over the operation of other control systems.
The design of all systems was completed in the first half of the eighties. This made it possible to start building the BTS-002 analogue aircraft for subsequent tests in the atmosphere. In addition, the construction of a full-fledged spacecraft has begun.
Aerodynamic control
"Buran" was built according to the "tailless" scheme with a low-lying delta wing, which had a variable sweep of the leading edge. There was a keel on the tail section of the fuselage. With such an aerodynamic shape, the orbital aircraft could make a gliding flight in the atmosphere, which was required for a regular landing.
The tail of the "Buran". The keel with rudder, control and orientation engine blocks, elevons and balancing shield are clearly visible. Photo by Wikimedia Commons
To control the landing, "Buran" received fairly simple and familiar means. Large-area elevons were placed on the trailing edge of the wing: their synchronous or differential deflection made it possible to control roll and pitch. Between the elevons, on the tail of the fuselage from below, they placed the so-called. balancing shield. With its help, controllability at super- and hypersonic speeds was improved. On the keel was the rudder. It consisted of two symmetrical vertical parts that could diverge to the sides and perform the tasks of an air brake.
All steering surfaces were hydraulically driven. To improve reliability, Buran received three independent hydraulic systems with their own pumps, pipelines, etc. The hydraulic actuators responsible for driving the rudders were remotely controlled by electrical signals from the main control systems.
Control in space
For work, maneuvering and orientation in orbit, Buran received the so-called. integrated propulsion system (APU). It included two sustainer engines with a thrust of 90 kN each in the tail. The ship also received 38 control engines and 8 precision orientation engines. These units were placed in the forward fuselage with nozzles on the top and on the sides, as well as in two characteristic tail shrouds.
Hydraulic drive of one of the aerodynamic rudders. Photo by Wikimedia Commons
The main work in orbit was assigned to the control engines of the 17D15 type. They were located in different parts of the airframe and were directed in different directions. Turning on certain engines for the required time, the crew or the autopilot had to change the orientation of the ship. Also, control engines could duplicate marching engines, but with a loss of performance.
Product 17D15 was a gas-liquid rocket engine powered by hydrocarbon fuel and oxygen. The thrust of one such product reached 4 kN with a specific impulse of up to 290-295 sec. During the flight, the engine could turn on up to 2 thousand times. The total resource is 26 thousand inclusions.
The orientation engine was similar in design to the control engine, but differed in smaller dimensions and other characteristics. Its thrust reached only 200 N with a specific impulse of 265 seconds. At the same time, 5 thousand inclusions were allowed per flight. Due to the lower thrust, a more accurate orientation of the ship in space was provided, sufficient for carrying out certain work.
The control of the ODE was carried out centrally with the help of appropriate instruments. The operation of the installation was controlled by the crew and / or automation, depending on the activities and tasks performed.
Crew simulator cockpit. Photo by Wikimedia Commons
Computing complex
A most complex control system was created for the Buran, which ensures flights in all modes and the solution of auxiliary tasks, the implementation of scientific or practical activities, etc. It included more than 1250 different devices and devices, digital computing tools, as well as numerous cable routes, etc. Various devices from the control system were distributed almost throughout the airframe of the ship.
The basis of the control system was the onboard central computer complex (OCCC), divided into two systems, central and peripheral. Each such system was built on the basis of two BISER-4 computers. Such an architecture of the onboard digital computer ensured high reliability and fault tolerance of the complex as a whole. Product BISER-4 developed by NPTsAP them. Academician Pilyugin was a 32-bit machine with a CPU performance of 37x104 op./sec. Power consumption - 270 W, weight - 34 kg.
BTsVK collected and processed data from various sensors, tools and systems. He was responsible for navigation in space and in the atmosphere, controlled the condition of components and assemblies, exchanged data with ground facilities of the complex, etc. The complex also controlled the operation of aerodynamic rudders and ODU. In the manual flight control mode, the BTsVK was supposed to convert the actions of the crew into commands for the actuators. The automatic mode provided for completely independent work.
For BTsVK, original software was created in the form of an operating system and a set of additional programs. The total amount of software was outstanding for that time - approx. 100 MB.
Schematic diagram of control systems. Graphics Buran.ru
The software complex ensured the operation of the hardware, the interaction of the onboard digital computer with various devices, etc. Among other things, it implemented automatic flight control algorithms in all modes. Of particular interest is the possibility of automatic descent from orbit, flight in the atmosphere and landing at a given airfield. It is curious that only an automatic landing mode was originally provided. Manual added later at the insistence of the customer.
Proven by practice
In 1984, NPO Molniya, with the assistance of other participants in the Buran project, built an analogue aircraft BTS-002, also known as OK-GLI or "0.02". It was a copy of an orbital aircraft, modified for horizontal takeoff and flight in the atmosphere. BTS-02 almost completely repeated the design of the Buran and had all the necessary controls, a computer system, etc. At the same time, it was equipped with turbojet engines.
On November 10, 1985, cosmonauts Igor Volk and Rimantas Stankevičius took the BTS-002 into the air for the first time. In June of the following year, on the fourth flight, semi-automatic planning was first tested - the pilots retained control of the aircraft, but some of the tasks were transferred to automation. At the end of 1985, experiments were carried out with automatic flight to the airfield; manual control was turned on only before touching. Finally, on February 16, 1987, in the tenth flight, the BTS-002 landed on its own for the first time. Until the spring of 1988, more than a dozen similar flights were completed to test systems and algorithms.
Gyroscopic inertial navigation device Sh300 (in the foreground), created for the Buran. Photo by Wikimedia Commons
Finally, on November 15, 1988, the first and only space flight of the orbital Buran took place. After two orbits around the planet, the ship automatically descended and landed at the Baikonur airfield. At the landing stage, the BTsVK received data on weather conditions at the airfield from ground facilities, correctly assessed them and performed an unexpected maneuver. "Buran" independently built an optimal approach and performed a landing against the wind.
Technology of the past
Unfortunately, Buran's first space flight remained the only one. In the future, for a number of reasons, the bulk of which can in no way be called objective, the Energia-Buran program was curtailed, and more work was not resumed. Orbital, atmospheric and other samples of the ship went to eternal parking, and some were lucky to become a museum exhibit.
However, even with this outcome, the bold and promising Buran program showed its potential. Soviet industry has demonstrated its ability to develop such equipment and bring it to at least testing. Using available and newly developed technologies and components, our enterprises have been able to create a space system with unique capabilities.
However, in the future, the experience of the Buran project, incl. in the context of control systems, as a whole remained unclaimed. In the first years or decades after the only launch of Energia-Buran, the industry did not have the opportunity to fully develop this direction. Then new technologies and a more advanced element base appeared with much greater potential.
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