Vol 22, No 1 (2021)

 Conservation laws were introduced into the theory of differential equations by E. Noether more than 100 years ago and are gradually becoming an important tool for the study of systems of differential equations. They not only allow us to qualitatively investigate the equation, but, as shown by the authors of this article, they allow us to find exact solutions to boundary value problems. For the equations of the isotropic theory of elasticity, the conservation laws were first calculated by P. Olver. For the equations of the theory of plasticity in the two-dimensional case, the conservation laws were found by one of the authors of this article and used to solve the main boundary value problems of the plasticity equations. Later it turned out that the conservation laws can also be used to find the boundaries between elastic and plastic zones in twisted rods, bent beams, and deformable plates. In this paper, we find conservation laws for equations describing the orthotropic elastic-plastic state of a twisted rectilinear rod. It is assumed that the conserved current depends linearly on the components of the voltage tensor. In this paper, we find an infinite series of conservation laws, which allows us to find the elastic-plastic boundary that occurs when an orthotropic rod is twisted.

The paper presents a multiversion model with ranking of alternatives in order of preference, taking into account the dependence of the attributes in the design of software for spacecraft control systems of various classes. The applied software with a set of algorithms, based on the general scheme of the method of branches and borders allow to determine the exact solution of the optimization problem.

To achieve the highest reliability of the software component of spacecraft control systems built with the use of multiversion programming methodology, a large number of versions of software modules are combined into a single structure.

While software complexes even without introduction of redundant elements are characterized as complex systems, there is no need to speak about wide use of enumerative methods for their formation.

Using the proposed modified method of ordered preference through similarity to an ideal solution, will allow to solve the problem of choosing the best computing system from a number of available systems. This approach is becoming increasingly possible because of the tremendous progress in computing design and manufacturing technology. Even the so-called personal computers provide computational capabilities that some time ago seemed impossible even for computers representing a much more powerful class of computing equipment – supercomputers.

In this article authors are considering about information security data integrity problem relevant for electronic archive management. In high-tech industry large electronic photo archives arises as a part of quality management. Photofixation applied for responsible operations control, documenting the technological process, fixing the components state on input and output control, incongruities registration. An image substitution or reuse possibility makes necessary electronic archive proto document integrity control. This illegal actions can be both the result of operator mistake and motivated by intentional a defect concealment. As a solution authors suggest an electronic archive organizing method for storing photo documents. The method based on a digital watermark labeling of full-color images with orthogonal Zernike moments calculated for certain image points (and their neighborhoods). Suggested method can prevent watermark destruction by geometric image transformation (rotation, compressing, reflection etc.). Digital watermark contains both information about technological process on current image and information about other images – this fact lets talk about integrity of whole photo documents set. One of the most important method characteristic is image format invariability and additional metadata files unnecessary what allows user to use standard software for a further work with photo document.

Given that the topic of using methane-hydrogen mixtures as fuel for gas turbine engines used as part of power plants has been actively developed recently, it is necessary to have engineering methods for calculating the fuel system and the combustion chamber of engines operating on such fuel. In this article, we propose a method that allows to perform such calculations. For the calculation, a gas turbine unit (GTU) NK-16ST based on a converted aircraft engine is taken.

The calculation according to this method is made in three stages. At the first stage, the composition is selected and the thermophysical characteristics of the gas in question are determined. At the second stage, the fuel system is calculated, the consumption characteristics of the engine fuel system and the combustion chamber system are built. A comparison of the consumption characteristics built for natural gas and methane-hydrogen mixture is made. This analysis allows us to develop recommendations for optimizing the design of fuel supply equipment and fuel nozzles, in terms of changing the volume of internal channels. At the third stage, the combustion chamber is calculated and recommendations are made about the need to change the front-end device or redistribute air along the length of the flame tube. The burning heat stress parameter is used to estimate the sufficiency of the available volume of the flame tube for operation on a methane-hydrogen mixture and to determine the average gas temperature in the combustion zone of the combustion chamber.

According to the result of the work performed the possibility of operating the NK-16ST gas turbine unit on a methane-hydrogen mixture was confirmed. It is also concluded that for the supply of large volumes of methane-hydrogen mixture, in comparison with natural gas, it is necessary to increase the size of pipelines, metering units, control units and fuel nozzles.

This paper considers the methodology for calculating the de-weighting system of spacecraft elements for ground tests, taking into account the deployment options, de-weighting conditions, types and options of de-weighting systems. An example of calculation for a 3-section solar battery without a beam with incomplete de-weighting and with minimization of moments in the hinges is given. Genetic algorithms are used as an algorithm for determining the parameters of the de-weighting system, which allows obtaining the minimum moments in the hinges. The moments and forces acting in the system were checked by plotting diagrams in the expanded state. In addition, a check for compliance with the specified distance, based on design constraints, between the points of application of the weighting forces was made.

Electro-jet (plasma or ion) thrusters are becoming increasingly common to correct a satellite orbit and perform orbit raising maneuvers to achieve the geostationary orbit. This is due to the greater efficiency of plasma thrusters compared to chemical ones.

When developing a satellite platform, an important place is the matching up of the electrical characteristics of the electric power subsystem (EPS) and on-board consumers. Intrinsically, this issue is an intersystem problem. The lack of proper attention paid to find the timely and correct solution of this problem can complicate the operation of the satellite electric power subsystem. The most important subsystem, which has a significant impact on the operation of the satellite EPS, is the electric-jet propulsion subsystem, since among on-board consumers, this one is the most powerful consumer being switched simultaneously. Transients occurred in the power supply circuits following thruster firing and shut down processes can reach significant values. An electric jet thruster only runs in conjunction with a complex electronic unit – a power processing unit (PPU), which converts the voltage of the on-board power supply into a set of voltages necessary for thruster components to run. Therefore, in the preliminary design of the propulsion subsystem, it is necessary to know the electrical characteristics of transients and ripples in the power supply circuits of the thruster / PPU combination being an electrical load of the Electric power subsystem. It is difficult to obtain the characteristics of such processes by the calculation method. Therefore, an experimental method is the most common and objective method to obtain this information. JSC ISS carried out tests allowing to measure characteristics of transients and ripples under firing, running and shut down of plasma thrusters of different types powered by corresponding PPU’s. These tests were conducted using a vacuum chamber GVU-60. A test power supply was used to simulate EPS operation. This paper presents the results of measurements and analysis of parameters of transients and ripples on PPU power buses used for thrusters and devices of three types. These results are considered to be preliminary. It is shown that the greatest difficulties can arise when operating high-power thrusters. It is concluded that for each new type of thrusters and PPU’s it is advisable to conduct interface tests of the propulsion subsystem and the satellite electric power subsystem.

Ensuring high reliability of unique high-critical products at the design stage is an actual task that the aerospace industry faces. For high reliability indicators, at the design stage, it is necessary to ensure the basic property of the product – its strength, with a high probability of non-destruction. It is provided by introducing the corresponding coefficients – «safety coefficient» and «margin of safety» into the strength calculations. The necessity in these coefficients is based on the spread of values of external loading factors: magnitude of forces, combination of forces, kind of actions, place of connection, etc. In this case, the safety coefficient is related to external factors. The margin of safety refers to internal factors: the spread of the mechanical characteristics of the product material, the spread of the geometric dimensions of the product, etc. To determine, with a given probability, the safety coefficient and margin of safety, it is necessary to know their dependence on the combination of spread of external and internal factors. The purpose of this work is to determine the mathematical connection between the internal factors of the spread and the safety coefficient, external factors of the spread and the margin of safety, the combination of these factors and the probability of non-destruction of structures. In this work the values of internal and external factors, which affect the strength and probability of non-destruction of the product and have the boundaries of the spread of their values, using the tools of probability theories, were characterized as random variables, the values of which are determined by the distribution density, expected value and variance. I this work there was found a high dependence of the product strength on the spread of its geometric characteristics and tools were defined to determine the total spread of the values of the main strength characteristics of the product with a given probability of non-destruction. The practical significance of the results of this work can be achieved in the aerospace industry, in particular, at the design stage of unique high-critical products.

In solid solutions Tm_xMn_1-xS, based on measurements of IR spectra and thermal expansion coefficient in the temperature range 80–500 K, the temperatures of sample deformation and disappearance of the absorption intensity of IR spectra at some frequencies are established. Anomalies in the temperature behavior of the electrical resistance are found, the sign of the current carriers and the mobility are determined from the Hall coefficient. The correlation between the temperatures of coefficient of electrical resistance and lattice deformation has been determined. A model of lattice polarons is proposed. The spectrum of electronic excitations and the density of electronic states in the interaction of electrons with flexural and tensile modes of the octahedron are calculated in the random phase approximation.

The electrooptic response of films of polymer dispersed nematic under conical boundary conditions has been investigated. An axial-bipolar director configuration is formed in nematic droplets. It has been shown that initially, the orientation of droplet’s bipolar axes is chaotic both in the sample plane and relative to the normal to the substrates. The applied voltage U orients the droplet’s bipolar axes parallel to the electric field and the reorientation process is threshold only when the bipolar axis is initially orthogonal to the substrate normal. Accordingly, the samples strongly scatter light in the initial state, and the optical response to an electric field is thresholdless. The samples with a film thickness of 5, 10, 20 and 30 μm have been studied. All the samples under study are characterized by a high transmittance and contrast ratio, which for a 30 μm sample are equal to 84 % and 5536, respectively, and achieved at U = 12 V. The results obtained are relevant for use in low-power optoelectronic devices required for the development of energy-saving technologies in aerospace engineering.