Annotation: Amid acute problems that arise in the field of rocket and space technology, mechanical engineering, and other fields and require a workable engineering solution, the problem of prediction and prevention of the unpredicted collapse of the structural members of the structures subjected to loading is considered. Prediction of the load-carrying capacity and residual life of the space frames during the long-term operation is based on the analysis of the stress and strain state, using readings from the strain and displacement pickups installed in the most loaded zones. In this case the yield strength of the structural material or the fatigue strength of the material may be considered as the criterion of the maximum load. At the same time the loss of stability of the compressed structural members used in the load-carrying thin-walled structures are among the potentially dangerous failure modes. In these cases such failure occurs unexpectedly without any visible signs of change in the initial geometry. Application of the adequate diagnostic techniques and methods of prediction of the maximum loads under compression conditions will make it possible to avoid the structural failures. In this case an assembly under test may be used for other purposes. To perform static strength testing, the rocket and space companies use costly compartments of as-built dimension. Therefore, keeping compartments safe solves an important problem of saving financial costs for hardware production. Nowadays this problem is particularly acute when ground testing the new technology prototypes.

Annotation: The study of thermal strength of the hold-down bay is considered. The hold-down bay is a cylindrical shell with the load-bearing elements as the standing supports. The case of the hold-down bay consists of the following structural elements: four standing supports and the compound cylindrical shell with two frames along the top and bottom joints. The purpose of this study was the development of a general approach for the thermal strength calculation of the hold-down bay. This approach includes two parts. Firstly, the unsteady heat fields on the hold-down bay surface are calculated by means of the semi-empirical method, which is based on the simulated results of the combustion product flow of the main propulsion system. The calculation is provided by using Solid Works software. Then the unsteady stress-strain behavior of the hold-down bay is calculated, taking into consideration the plastoelastic deformations. The material strain bilinear diagram is used. The finiteelement method is applied to the stress-strain behavior calculation by using NASTRAN software. The thermal field is assumed to be constant throughout the shell thickness. As a result of the numerical simulation the following conclusions are made. The entire part of the hold-down bay, which is blown by rocket exhaust jet, is under stress-strain behavior. The stresses of the top frame and the shell are overridden the breaking strength that caused structural failure. The structure of the hold-down bay, which is considered in the paper, is unappropriated to be reusable. The hold-down bay should be reconstructed by reinforcement in order to provide its reusability.

Annotation: The strength of real solids depends essentially on the defect of the structure. In real materials, there is always a large number of various micro defects, the development of which under the influence of loading leads to the appearance of cracks and their growth in the form of local or complete destruction. In this paper, based on the method of singular integral equations, we present a unified approach to the solution of thermal elasticity problems for bodies weakened by inhomogeneities. The purpose of the work is to take into account the heterogeneities in the materials of the elements of the rocket structures on their functionally-gradient properties, including strength. The choice of the method of investigation of strength and destruction of structural elements depends on the size of the object under study. Micro-research is related to the heterogeneities that are formed in the surface layer at the stage of preparation, the technology of manufacturing structural elements. Defectiveness allows you to adequately consider the mechanism of destruction of objects as a process of development of cracks. In studying the limit state of real elements, weakened by defects and constructing on this basis the theory of their strength and destruction in addition to the deterministic one must consider the probabilistic – statistical approach. In the case of thermal action on structural elements in which there are uniformly scattered, non-interacting randomly distributed defects of the type of cracks, the laws of joint distribution of the length and angle of orientation of which are known, the limiting value of the heat flux for the balanced state of the crack having the length of the “weakest link” is determined. The influence of heterogeneities of technological origin (from the workpiece to the finished product) that occur in the surface layer in the technology of manufacturing structural elements on its destruction is taken into account by the developed model. The strength of real solids depends essentially on the defect of the structure. In real materials, there are always many various micro defects, the development of which under the influence of loading leads to the appearance of cracks and their growth in the form of local or complete destruction. In this paper, based on the method of singular integral equations, we present a unified approach to the solution of thermal elasticity problems for bodies weakened by inhomogeneities. The purpose of the work is to take into account the heterogeneities in the materials of the elements of the rocket structures on their functionally gradient properties, including strength. The choice of the method of investigation of strength and destruction of structural elements depends on the size of the object under study. Micro-research is related to the heterogeneities that are formed in the surface layer at the stage of preparation, the technology of manufacturing structural elements. Defectiveness allows you to adequately consider the mechanism of destruction of objects as a process of development of cracks. In studying the limit state of real elements, weakened by defects and constructing on this basis the theory of their strength and destruction besides the deterministic one must consider the probabilistic – statistical approach. With thermal action on structural elements in which there are uniformly scattered, non-interacting randomly distributed defects of the cracks, the laws of joint distribution of the length and angle of orientation of which are known, the limiting value of the heat flux for the balanced state of the crack having the length of the “weakest link” is determined. The influence of heterogeneities of technological origin (from the workpiece to the finished product) that occur in the surface layer in the technology of manufacturing structural elements on its destruction is taken into account by the developed model. The solution of the singular integral equation with the Cauchy kernel allows one to determine the intensity of stresses around the vertexes of defects of the cracks, and by comparing it with the criterion of fracture toughness for the material of a structural element, one can determine its state. If this criterion is violated, the weak link defect develops into a trunk crack. Also, a criterion correlation of the condition of the equilibrium defect condition with a length of 2l was got, depending on the magnitude of the contact temperature. When the weld is cooled, it develops “hot cracks” that lead to a lack of welding elements of the structures. The results of the simulation using singular integral equations open the possibility to evaluate the influence of thirdparty fillers on the loss of functional properties of inhomogeneous systems. The exact determination of the order and nature of the singularity near the vertices of the acute-angled imperfection in the inhomogeneous medium, presented in the analytical form, is necessary to plan and record the corresponding criterion relations to determine the functional properties of inhomogeneous systems.

Annotation: This article analyzes the results of studies, which are based on numerical methods of analysis, of the stress-strain state of thin-walled shell structures. This article also discusses analytical solutions that apply asymptotic approaches and a method of initial parameters in a matrix form for solving a problem of equal stability of reinforced compartments of combined shell systems of the rocket and space technology within the scope of the research being carried out jointly by teams of Yuzhnoye State Design Office and Zaporizhzhya National University. The primary attention is paid to the use of FEM-based direct numerical methods and the research results for which analytical methods can be useful for making a preliminary assessment of the bearing capacity of load-bearing structures, and in some cases for their rational design. This article does not contrast numerical and analytical approaches but about the possibility of using them effectively. The article talks about possible ways of using the up-to-date technique of machine learning (Machine Learning Technology) in the calculation and experimental methods for determining the characteristics of the rocket and space technology.

Annotation: The shell structures widely used in space rocket hardware feature, along with decided advantage in the form of optimal combination of mass and strength, inhomogeneities of different nature: structural (different thicknesses, availability of reinforcements, cuts-holes et al.) and technological (presence of defects arising in manufacturing process or during storage, transportation and unforseen thermomechanical effects). The above factors are concentrators of stress and strain state and can lead to early destruction of structural elements. Their different parts are deformed according to their program and are characterized by different levels of stress and strain state. Taking into consideration plasticity and creeping of material, to determine stress and strain state, the approach is effective where the calculation is divided into phases; in each phase the parameters are entered that characterize the deformations of plasticity and creeping: additional loads in the equations of equilibrium or in boundary conditions, additional deformations or variable parameters of elasticity (elasticity modulus and Poisson ratio). Then the schemes of successive approximations are constructed: in each phase, the problem of elasticity theory is solved with entering of the above parameters. The problems of determining the lifetime of space launch vehicles and launching facilities should be noted separately, as it is connected with damages that arise at alternating-sign thermomechanical loads of high intensity. The main approach in lifetime determination is one that is based on the theory of low-cycle and high-cycle fatigue. Plasticity and creeping of material are the fundamental factors in lifetime substantiation. The article deals with various aspects of solving the problem of strength and stability of space rocket objects with consideration for the impact of plasticity and creeping deformations.

Annotation: The measurement errors upon conducting flight tests for launch vehicles are evaluated by considering the interferences and uncertainties in the measurement system procedure. Formal use of this approach can lead to unpredictable consequences. More reliable evaluation of errors upon conducted measurements can be achieved if the measurement process is regarded as a procedure of successive activities for designing, manufacturing, and testing the measurement system and the rocket including measurements and their processing during the after-flight analysis of the received data. The sampling rates of the main controlled parameters are three to ten times higher than the frequency range of their changing. Therefore, it is possible to determine the characteristics of the random error components directly on the basis of registered data. The unrevealed systematic components create the basic uncertainty in the evaluation of the examined parameter’s total measurement error. To evaluate the precision and measurement accuracy of a particular launch, the article suggests specifying the preliminary data on measurement error components determined during prelaunch processing and launch. Basic structures of algorithms for evaluation of precision and measurement accuracy for certain mathematical models that form the measured parameters were considered along with the practical case when static correlation existed among the measured parameters.

Annotation: The structure examined herein aims to keep fuel from entering the space behind the cuff, evacuate the space behind the cuff, reliably fasten the cuff to the thermal protective coating of the bottom in the process of charge forming, easily release the cuff after charge forming, and remove the support structure elements from the casing after charge polymerization when equipping. The structure was tested in the process of fueling the solid rocket motor casing and during charge polymerization. In order to comply with the specified requirements the cuff functions were identified, the structures previously developed were analyzed, and a new structure was designed and improved after testing. The improved structure ensured that fuel did not enter the space behind the cuff; it was removed easily after charge forming. Conclusions proved the suitability of this stricture.

Annotation: During experimental investigation of the dynamic characteristics of a pneumatic test bench for testing liquid rocket engine high-flowrate automatic units, the effect was detected of 20-35% sound speed increase in the gas flow moving along the channel with corrugated wall (metal hose) which is a part of test bench drain system. The article presents the results of experiments and the task of theoretical justification of the effect is solved. It is indicated that its causes may be two mutually complementary factors – a decrease of gas compressibility at eddy motion and oscillations of metal hose wall. The physical model is considered that describes variation of gas elasticity and density in the conditions of high flow vorticity. It is supposed that in the near-wall layer of the channel, toroidal vortexes (vortex rings) are formed, which move into turbulent core of the flow where their size decreases and the velocity of rotation around the ring axis of torus increases. The spiral shape of the corrugation ensures also axial rotation, which increases vortexes stability. The intensive rotation around the ring axis creates considerable centrifugal forces; as a result, the dependence of pressure on gas density and the sound speed increase. The mathematical model has been developed that describes coupled longitudinal-lateral oscillations of gas and channel’s corrugated shell. It is indicated that in the investigated system, two mutually influencing wave types are present – longitudinal, which mainly transfer gas pressure pulses along the channel and lateral ones, which transfer the shell radial deformation pulses. As a result of modeling, it has been ascertained that because of the lateral oscillations of the wall, the propagation rate of gas pressure longitudinal waves (having the same wave length as in the experiments at test bench) turns out to be higher than adiabatic sound speed.

Annotation: In the pneumohydraulic systems of liquid rocket engines and propulsion systems, electromagnetic valves that allow making the pneumohydraulic systems more simple and ensuring multiple ignition of liquid rocket engines have found wide application. The Yuzhnoye-developed electromagnetic valves are designed according to two schemes – of direct and indirect action. In the direct-action electromagnetic valves, the shutting-off device opens (closes) the throat with the force developed by electric magnet. They have gained acceptance in the pneumohydraulic systems with the working medium pressure of ~8.5 MPa, they are of simple design and have high operating speed (0.001…0.05 s). In the electromagnetic valves with amplification, the electromagnet armature is connected with control valve and the main shutting-off device moves due to the force from working medium pressure drop on it. They are used in the operating pressure range of 0.5…56 MPa, at that, the action time is 0.025…0.15 s. For the European Vega launch vehicle fourth stage main engine assembly that has pressure propellant feeding system, the electrohydraulic valve with amplification and drainage was developed. The dependence of this electrohydraulic valve high speed from the line’s output length is decreased to the maximum due to the installation of Venturi nozzle at the output connecting branch. This electrohydraulic valve is operable at the pressure below 8 MPa, the action time is 0.08…0.12 s. The present-day spacecraft gas-jet orientation and stabilization systems use as propulsion devices the electromagnetic valves with nozzles whose thrust is, as a rule, not more than 30 N and the working medium pressure is up to 24 MPa. Yuzhnoye State Design Office developed for 15B36 gas-jet system the electropneumatic valve with amplification and nozzle, which is operable at the pressure below 45 MPa, ensures the action frequency of up to 10 Hz and is capable of creating the thrust of 100 N on gaseous argon. To solve the task of decreasing the dependence of operability and high speed of electromagnetic valves with drainage and amplification on geometry of lines in which a valve is installed, the electropneumatic valve was developed that has spool elements ensuring reliable and quick action with long input lines of 0.004 m diameter. Its mass is 2…2.5 times lower than the mass of analogs. Recently, Yuzhnoye State Design Office develops the apogee RD840 LRE with 400 N thrust, for the conditions of which the direct-action electrohydraulic valve was developed and tested with the following characteristics: pressure – up to 2.15 MPa, consumed power in operation mode – less than 7.1 W, action time – not more than 0.02 s, mass – 0.19 kg. The presented electromagnetic valves by their technical and operational characteristics meet the highest world requirements and have found wide utility in liquid rocket engines and propulsion systems.

Annotation: The paper addresses a new, authors- developed method of mass optimization of rocket bays of wafer structure bearing during operation on locally disposed parking supports. The method allows, due to more rational distribution of materials in the structure in accordance with acting load, decreasing the mass of bays by up to 20%.