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 pyrobolts, or explosive bolts, belong to the pyrotechnical devices with monolithic case consisting o f the cap, as a rule with hexagonal surface, and of cylindrical part with thread. The pyrobolts are separated into parts using the pyrotechnical charge placed inside the case. Owing to the simple design, reliability and short action time, the pyrobolts have found wide application in aerospace engineering for separation of assemblies and bays, in particular, stages, head modules, launching boosters, etc. So, for example, about 400 pyrobolts are used in the Proton launch vehicle. The designs of pyrobolts are markedly different. By method of explosive substance action on case structural elements, the pyrobolts are divided into two types: the pyrobolts using the shock wave formed at detonation of brisant explosive substance for case wall destruction and the pyrobolts using the pressure of gases arising at pyrotechnical charge blasting. By method of separation into parts, they are divided into fragmenting pyrobolts with ridge-cut, with piston, and shear pyrobolts. The paper deals with the design of various types of pyrobolts, their disadvantages are considered. The Yuzhnoye SDO-developed pyrobolt of shear type with segments is presented that uses radial shear forces of segments located in the hole of cylindrical part to separate the case parts. The above segments a re actuated using a rod with sealing rings and a piston connected to the rod through a rubber gasket; the piston moves under pressure of gases formed during pyro cartridge action. The following calculations are presen ted: strength analyses with determination of case load-carrying capacity; power analyses with justification of pyro cartridge selection for pyrobolt actuation. In the developed pyrobolt of shear type with segments, the case parts are separated without considerable shock loads and without high-temperature gases and fragments release into environment, ensuring reliable separation of bays and assemblies without damaging sensitive equipment.

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 exploratory and experimental investigations were conducted into design of propellant tank made of composite polymer materials for work in cryogenic environment at operating pressure of 7.5 kgf/cm2 . When determining the configuration of a liner-free composite propellant tank, the main requirement was ensuring its leak-tightness at internal excess pressure and cryogenic temperature effect. The world experience of creating similar designs was analyzed and the requirements were defined imposed on configuration of propellant tank load-bearing shells. Before defining the final configuration, the types of materials, reinforcing patterns, and possible ways to ensure leak-tightness were analyzed, and preliminary tests were conducted of physical and mechanical characteristics of thin-wall samples of composite materials and tubular structures with different reinforcing patterns. The tests of carbon plastic samples were conducted at different curing modes to determine the most effective one from the viewpoint of strength characteristics and the tests for permeability by method of mouthpiece were conducted. The tests of pilot propellant tank showed that the calculated values of deformations and displacements differ from the experimental values by no more than 10 %. Using the parameters measurement results from the tests on liquid nitrogen, the empirical formulas were obtained to calculate linear thermal expansion coefficient of the package of materials of load -bearing shell. The empirical dependences were constructed of relative ring deformations at load-bearing shell middle section on pressure and temperature. The tests confirmed correctness of adopted solutions to ensure strength and leak-tightness of propellant tank load-bearing shell at combined effect on internal excess pressure and cryogenic temperature, particularly at cyclic loading. The materials used and propellant tank manufacturing technologies ensure leak-tightness of load-bearing shell at liquid nitrogen operating pressure of 7.5 kgf/cm2 and strength at excess pressure of 15 kgf/cm2 and allow conducting approbation of prospective stage of the integrated launch vehicle.

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: One of the tasks of the development tests conducted on a launch pad is verification of its strength properties. The tests are carried out after the launch pad was manufactured and assembled on-site as well as during the whole operating period (if necessary). Load mode was chosen in consideration of cost and possibility of providing the required loading conditions. Two modes of creating the required test load were examined: usage of weights with corresponding mass (load simulators) or special devises (which have smaller mass as compared with load simulators). The descriptions, basic characteristics, advantages and disadvantages of composite and bulk weights and pad loading device are given. This article studies the pad loading device under development. This device enables to conduct static nondestructive tests on the launch pad in order to check its strength after manufacturing and during the whole operating period. The device consists of the load-bearing frame, hydraulic system, locks, control system and measurement system. Advantages of the pad loading device include low materials consumption, low cost in comparison with composite weights (with large load values), provision of the required modes for applying and removing the test load, controlled separate loading of each support of the launch pad, high mobility, short duration of testing, possibility of using launch pads of other rocket complexes with lower or equal test load values for testing. Therefore, the pad loading device enables to achieve the required test load values while having considerably smaller dimensions and mass as compared with composite weights and bigger functional possibilities as compared with bulk weights. Small overall dimensions and operability reduce the number of needed personnel and equipment.

Annotation: The article describes the problems of manufacturing large-size nozzle blocks by classical for Ukrainian space industry method of high-temperature brazing. The Yuzhnoye SDO-selected way of solving this problem and the first strides on the way to organization of new production using innovative technologies of laser welding and surfacing are presented. The step-by-step sequence and procedure of research work to develop and test a new technology of cooled nozzle block manufacturing are described. Four phases are identified, out of which the first two phases have already been successfully performed. The laser welding and surfacing technology will allow avoiding the use of costly and unique equipment and will allow reducing and optimizing the technological manufacturing cycle rejecting the long –term and energy-consuming technological operations. The scientific-and-technological works performed showed the principle feasibility of making connection between the external jacket and internal wall of a nozzle block using laser welding. The test samples manufactured confirmed the high strength characteristics, which had been preliminary obtained by the theoretical calculation methods. The sections obtained by surfacing demonstrate good metallurgical connection between the layers. On the test samples, the technique was tried-out allowing repairing defect areas in a welded seam obtained by laser welding method. This is especially important from the technological and economic viewpoints, as the technology of high-temperature brazing applied currently does not allow making guaranteed repair of brazed joints.

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: The remote control method of launch vehicle hydrosystem detachable joints airtightness by mass spectrometer at the Launch Complex in conditions of limited access to hydrosystem elements is under consideration. The additional design development of hydrosystems prior to article roll-out to the launch side is provided for control.