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 article dwells on the problem of enhancement of durability for the mechanical rubber articles, which is directly related to the enhance of rubber resistance to various types of heat aging. Heat resistance during compression is most important for rubbers used for seals of various types: rings, collars, armored collars, gaskets for aviation and rocket technology hardware. Stress relaxation and the accumulation of relative residual deformation of rubbers, caused by the kinetic rearrangement of chemical bonds, are extremely sensitive to the influence of high temperatures. The main cause of the defects is the loss of elastic properties of the seals because of the accelerated heat aging of the nitrile group under conditions of long-term exposure to elevated temperatures in conditions of hot climate. The results of accelerated climatic testing of specimens of mechanical rubber articles, as well as the results of climatic endurance testing of the units for the period simulating 20-year service life are specified, and the main types of defects which result in the loss of performance properties of the mechanical rubber articles are as follows: great (up to 100%) residual deformation of intersections, cracking, loss of elasticity. The warranty life of fuel system units, made of ИРП-1078 nitrile rubber, does not exceed 12 years. Replacing the existing rubbers with rubbers created on the basis of more heat-bearing rubbers is the most promising way to improve the performance properties of the mechanical rubber articles under the high temperatures. The new D2301 rubber is based on fluorosiloxane rubber. It provides high thermal stability and, especially, the ability to maintain high performance properties for a long time under the simultaneous impact of hostile environment and high temperatures. The results of climatic endurance testing of fuel system units, equipped with rubber articles made of D2301 rubber, fully justify the increase of the specified service life of the specified units from 12 to 16 years. It is recommended to introduce D2301 rubber into the effective normative documentation and continue studies in order to extend the nomenclature of mechanical rubber articles made of D2301 rubber to provide the reliable sealing of units during the service life of 16 years or longer.

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 article is devoted to optimization of a trajectory of the antiaircraft guided missile performed in design phase. The review of existing solutions on this issue confirmed the topicality of the problem. The analytical solution cannot be obtained, therefore, according to modern tendencies, optimization by numerical method of original development was performed. The basis of the method is two-level optimization which is carried out, in turn, by two different numerical methods and for two different criteria functions. At the top level, by method of random search and as a variant, by method of coordinate descent, the search was carried out for a fixed set of intermediate for the specified flight range trajectory points which co-ordinates in aggregate provide the necessary optimum. At the bottom level, for each pair of consecutive intermediate points, the boundary problem of falling into distant point by one-dimensional optimization was solved. The coordinate descent method was used for search for the simplified flight program. As optimization criteria for top level, minimum flight time or maximum final speed, for bottom  terminal criterion were used. The control program selected the angle of attack  program. As a result, the optimum and suboptimum (additionally ensuring minimum calculation time) trajectories and flight programs to maximum range and different altitudes were obtained. The analysis of results showed practical proximity of trajectories of minimum flight time and maximum final speed.

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 comparison has been made of mechanical characteristics based on yield strength values of prospective aluminum alloys and steels with the stresses arising in pipeline parts. The conclusions have been drawn about the principal feasibility of manufacturing the pipelines of given materials and replacing the steels with the high-strength aluminum alloys for majority of the parts.

Annotation: This work deals with the problem of cylindrical shell stability within Donnel-Vlasov linear theory based on updated equilibrium equations and dynamic approach to their solution. The new theoretical results of critical stress determination that are well agreed with experimental data are presented here. The plot of critical stress as a function of dynamic behavior of specific shell is shown here. The wave generation parameters for the moment of equilibrium loss for each specific case are also presented in this work.

Annotation: This paper describes the effective approach for the technology of the rocket airframe development testing, based on the method of numerical modelling, which enables the virtual experimental runs prior to the beginning of the development testing to check the performance of the standard airframes and predict issues of concern. The method is realized based on the computer models developed in the ANSYS Workbench environment. Based on the offered method the complex mechanical system, which attaches the cluster projectiles in the conditions of the temperature exposure and heat cycling, underwent the virtual tests. Computational models, criteria and test procedures necessary for the analysis of the mechanical condition and prediction of the performance of the actual airframe of the warhead were developed. Moreover, computational models consider all the design and technological features of the airframe: layout of the projectiles attachments, initial stress-strain state of the system after the tightening of the threaded connections, friction between the components of the system and their mutual displacement, temperature dependence of the physical and mechanical characteristics and ultimate stress of materials. For the specified loading conditions during the ground operations with the warhead, the most dangerous computational cases are determined which have been implemented during the virtual tests. Test results were used to conduct the static analysis of the mechanical condition, strength and conditions for performance of the actual structure of the attachment under the impact of the operating levels of temperature exposure and heat cycling. Results of the virtual tests confirm the performance of the projectiles attachment system and are introduced into production in the phase of engineering development.