This work is concerned with studying the static and dynamic characteristics of the gas-dynamic (interceptor) subsystem of a combined system for thrust vector control and identifying ways to increase its efficiency. The combined control system includes a mechanical and a gas-dynamic subsystem. The gas-dynamic thrust vector control subsystem is the most important and reliable part of the combined control system. Consideration is given to disturbing the supersonic flow by installing a solid obstacle (interceptor) in the middle part of the rocket engine nozzle. An important advantage of this method to gas-dynamically control the rocket engine thrust vector is that the thrust vector control loss of the specific impulse is nearly absent because the control force is produced without any consumption of the working medium. Injection through the interceptor protects it against exposure to the nozzle supersonic flow and produces an additional lateral force. By now, the optimum height of the mass supply opening in the interceptor that maximizes the control force has not been determined, and the dynamic characteristics of this system have not been studied. The aim of this work is to find the optimum position of the opening for working medium supply through the interceptor that maximizes the added control force and to determine the effect of the transfer functions of the interceptor system components on the characteristics of the control force production transient. As a result of the study of the static characteristics of the supersonic flow disturbance in a nozzle with an interceptor through which a secondary working medium is injected, it is concluded that in terms of thrust vector control efficiency and interceptor protection the injection opening should be situated in the upper part of the interceptor. The transfer function of interceptor control of the liquid-propellant rocket engine thrust vector is obtained with account for the production of an additional control force by the injection of a liquid propellant component. It is found that the loss of stability of the operation of an injection interceptor unit depends on the transient of the working medium injection control valve.
Solving new problems of rocket space stage control calls for improving rocked engine thrust vector control actuators in order to reduce energy consumption for control, simplify their design, and improve their dynamic performance and reliability. As a result of previous studies, in which the authors of this work took part, a new bifunctional thrust vector control system based on a combination of a mechanical and a gas-dynamic thrust vector control system was proposed and substantiated. That solution on thrust vector control improvement made it possible to realize the advantages of the constituent subsystems, while eliminating their disadvantages. This paper focuses on the drawback of the new concept of thrust vector control, which consists in the need for heavy-mass drives to rotate engine components. The paper presents and substantiates a new solution on eliminating the above drawback by transferring the function of the rotary drives to the gas-dynamic system. In doing so, the large force that rotates the engine on the hinge is produced by the gas-dynamic system in a pulsed mode, thus eliminating large energy consumption (during the operation of the gas-dynamic system) for engine rotation. The rocket stage is stabilized by control forces of small amplitude and high frequency produced by the gas-dynamic control system. So the bifunctional thrust vector control system is transformed into a system that is entirely gas-dynamic, except that a hinge joint is used to rotate engine components (in the case under study, the combustion chamber). The elimination of drives reduces the mass of the thrust vector control system, increases its reliability, and allows one to carry out its complete dynamic testing under terrestrial conditions because there is no need to rotate the engine during its operational development. The thrust vector control energy consumption (engine specific impulse loss) of the proposed system does not exceed that of an economy mechanical system (where the trust vector is controlled by engine rotation)..
Space hardware improvement is largely determined by a further increase in the efficiency of rocket propulsion systems. Extending the functional capabilities of propulsion systems is of special importance to stage flight control. The main advantage of thrust vector control by rotating the engine mounted on a cardan joint is the possibility of producing sufficiently large control forces with a minimum of specific impulse loss caused by the control process. The advantage of the gas-dynamic control system is its high dynamic performance. The new control system concept considered in this paper consists in combining the two above-mentioned control systems (the mechanical one and the gas-dynamic one) into a single bifunctional thrust vector control system (BTVCS). The BTVCS, which is an integral part of the rocket stage flight control system, must produce control forces needed to implement the flight program and counteract disturbances acting on the stage with an optimum distribution of functions between its two constituents: the mechanical system and the gas-dynamic system. In doing so, it is necessary to minimize the power consumption for control without affecting the control quality. The aim of this work is to substantiate the advantages of possible BTVCS layouts and the proposed procedure of separate analysis of the BTVCS input signals, which is the heart of the BTVCS structural schematic. It is shown that for a space rocket stage the BTVCS allows one, with a minimum of power consumption for control, to implement the combined task of counteracting deterministic disturbances (produced, for example, when a part of the payload is detached) and stabilizing the motion in cases where random disturbances of wide frequency spectrum act on the rocket stage. A new approach to BTVCS input signal analysis and a control signal generation algorithm are proposed. The static component extracted from the total BTVCS input signal is counteracted by the mechanical thrust vector control system, which basically implements the task of guiding the space stage along the desired trajectory. The dynamic component of the signal, which is due to random (as a rule, highfrequency) disturbances, is counteracted by the gas-dynamic thrust vector control system and basically implements the stage stabilization task. The procedure was verified by the example of telemetry data on the pitch angle of the first combustion chamber of an 11D520 liquid-propellant rocket engine.
This paper presents the main results of the investigations conducted at the Department of Power Plant Thermogas Dynamics of the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine over the past five years with the aim to solve some problems involving rocket engine gas flow control. The stability and controllability of a Cyclone-4-type rocket space stage with a large variable mass asymmetry were studied. It was shown that combined thrust vector controls that include a mechanical and a gas-dynamic system make it possible to enlarge the space stage stability region, to improve the controllability characteristics and the reliability of the space stage control system as a whole, to solve the problem of active damping of stage structure lateral vibrations, and to significantly simplify the ground tryout of the engine (with a large nozzle divergence ratio). A bifunctional system of rocket engine thrust vector control was developed. The system separately counteracts the static and dynamic components of disturbing actions on the control object (rocket stage) and provides its motion stability. The mechanical part of the system may be based on the rotation of the engine or thrust-producing parts thereof, and its gas-dynamic part may be based on disturbing the supersonic flow in the engine nozzle with obstacles of various types mounted on the inside wall of the nozzle. Different designs of the gas-dynamic part were substantiated and patented, thus allowing one to choose the optimum alternative at the design stage of a rocket engine thrust vector control system. The new concept of rocket engine thrust vector control was shown to be applicable to different launch vehicle stages, both liquid-propellant and solid-propellant ones.
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