Vol 23, No 4 (2022)

The editors of the journal "Siberian Aerospace Journal" and the staff of the Siberian State University. M. F. Reshetneva

During the operation of rocket and space technology, electronic computing systems, power supply systems, heat supply systems, transport systems and many others, failures occur, there are threats of attacks, security threats and many other impacts that are random in nature and have a negative role in their work. Such impacts lead to restoration processes in which the operating time of the restored elements before their failure, the number of failures, the time and cost of restorations are random variables. In the theory of probability and in the mathematical theory of reliability, when studying restoration processes, the restoration function (the average value of the number of random failures) plays a special role. We especially note its importance in optimization problems when choosing a strategy for carrying out recovery processes. So one of the most important criteria for optimality is the average number of failures, the average cost of restoration, cost intensity, availability factor. We also note the problem of the need and timing of preventive restorations. Within the framework of the mathematical theory of reliability, models of restoration processes are considered taking into account the cost of restorations with varying distribution functions of the time to failure of the restored elements and the costs of restorations. For the models under consideration, a formula for the cost function (average cost of restorations) through the restoration functions of two general restoration processes is obtained, which allows proving theorems on the asymptotic behavior of the cost function, well known for the asymptotic behavior of the restoration function of the general restoration process, where the restoration time is not taken into account. The obtained asymptotic theorems for the average cost of restorations are generalized to the introduced alternating (when the random time of restorations is also taken into account) restoration process, taking into account the cost of restorations with changing distribution functions of the time to failure of the restored elements and the costs of their restorations.

Currently, the development of large-sized space structures and, in particular, transformable reflectors is actively developing. A feature of these devices is a small volume during transportation and large dimensions in the expanded working condition. Therefore, it is important to carry out a reliable and smooth deployment, adjust the shape of the active radio-reflecting surface with a given accuracy, and adjust the orbital position. In outer space, the system is constantly exposed to radiation, there is a large temperature difference in near-Earth orbit, there is a solar wind, which mainly affects the radiation pattern. In this paper, the process of deployment of the reflector spokes in the presence of disturbances and measurement errors is considered. The solution to the problem is presented using the separation theorem. To estimate the parameters of the system in the presence of measurement noise, the Kalman filter is applied. Its performance is shown at various values of the noise intensity. A random process such as white noise was selected as external disturbances and measurement noises. The control problem is solved using the optimal control algorithm according to the hierarchy of target criteria. The possibility of minimizing energy costs by means of interval switching on of measuring sensors is shown. The results of numerical simulation are presented.

Due to the constant tightening of flight safety requirements in the country and abroad, due to the constant growth in air traffic, more and more requirements are placed on the reliability, non-failure operation of air navigation systems and methods for updating their air navigation databases. Also, the question arises of the relevance of the databases used in accordance with the AIRAC cycle, since in the case of using non-updated aeronautical information in the FMS, VSS, SNA, SRPBR systems, the risk of emergency situations or disasters increases. In the article, the author proposes to consider the issues of improving aircraft navigation systems and updating databases using computing systems such as FMS? Russian aircraft use VSS-95-1V, onboard ground proximity early warning systems (EPWS) and onboard satellite navigation systems operating with an orbital satellite constellation (GPS, Glonas). All of them are equipped with aeronautical databases, which, in accordance with the AIRAC cycle, are updated on the ground by engineering and technical personnel every 28 days, the frequency of updates is made depending on the receipt of changes in navigation data for the operation of these systems. The issues of analysis of operational characteristics, analysis of methods for transmitting data to onboard aircraft systems, development of aeronautical data transmission system, development of a remote transmission control system, Development of data transmission algorithms, theoretical and experimental justification for choosing a transmission system model are considered. The use of the considered complex leads to a qualitatively new level of efficiency, reliability of updating aeronautical databases in the FMS, SNS, SRPBZ, VSS systems, which will undoubtedly affect the increase in flight safety, as well as the regularity of flights, in the absence of aircraft downtime according to the criterion of operational database updating AIRAC cycle data.

To date, the problems associated with the safety of unmanned aerial vehicles (UAVs) are quite acute. As a rule, when it comes to commercial small-sized UAVs, wireless communication channels are used to control them. Most often, communication is implemented at a frequency of 2.4 GHz using the Wi-Fi protocol. Such a UAV is quite easy to detect by analyzing the radio frequency range or the data link layer. An attacker, however, may not even have specialized equipment and use open source software. The detected UAV becomes the target for attacks. If it is known that the UAV operates as a wireless access point, then all Wi-Fi-specific attacks become relevant for the UAV. In this study, it is proposed to use the technology of creating false information fields as the first line of defense to increase the resistance of the UAV to attacks. This technology will allow to hide a legitimate UAV communication channel behind a lot of fake ones. The goal is to create fake access points with the characteristics of real ones and emulate data transmission over the channels on which these access points are deployed. In addition to the fact that the technology allows to hide a legitimate UAV communication channel, it will also allow to mislead the attacker. It is important to make the intruder think that not a single UAV is approaching him, but a group. If the intruder attempts to attack decoys, attacker will compromise himself and be able to be detected. Thus, you can use the UAV as a bait. As a result of the pilot study, channels were identified on which the creation of fake access points is most effective. Using small computing power and the necessary antenna, you can achieve high results. This article demonstrates the effectiveness of creating 9 fake access points. A comparison was also made with real wireless network traffic. We can say that the emulated activity is quite close to the real activity.

The paper investigates the need to create a method of simulating the starry sky for testing spacecraft and conducting tests of orientation and stabilization systems in laboratory conditions.

Modern space exploration and, as a consequence, the complexity of technical requirements for flight support facilities are constantly increasing, respectively, the requirements for ensuring the accuracy of determining the position and orientation of the spacecraft are increasing.

The history of the development of astroorientation devices and, in particular, stellar sensors is given. The modern stage of development of stellar sensors came with the advent of matrix radiation receivers: CCD and CMOS video matrices. Such stellar sensors are no longer tied to individual, predefined stars, but determine their orientation from images of groups of stars visible in the field of view of the device. Examples are given for their field of application, namely, determining the orientation of the sensor, pointing some device mounted on a spacecraft, and others.

Modern requirements for astrogation are given. The basic principles of ground-based testing of the spacecraft orientation and stabilization system using starry sky simulators are considered.

This is a stage of development and autonomous tests on a hardware and software stand of semi-natural modeling. To date, the ISS JSC enterprise has a complex modeling stand for conducting these types of spacecraft tests, using methods of both mathematical and semi-natural modeling, which includes various simulators of the starry sky.

The development of these simulators has a long history, a comparative table of previously used simulators is given. The structures of both past and modern simulators of the starry sky are shown.

The conclusions state the need to create a method that will simulate the rotation of the spacecraft at speeds up to 15–30 °/s. This method will allow testing the orientation and stabilization system of modern spacecraft.

The work discusses the problem of providing the required first natural frequency of bending vibrations of the beam under the action of a longitudinal force by introducing the necessary stiffness of the supports. Considering and combining the equations of free vibrations of the beam and the equations describing the loss of its stability, the operability condition was obtained because of providing a minimum given value of the first natural frequency of vibrations considering the action of the axial force. In this case, the achievement of the zero frequency of natural vibration corresponds to the loss of stability, which allows solving both problems. This problem is mathematically complex, and in the known scientific literature its solution is usually given only in graphical or tabular form. The problem lies in the nonlinear dependence of the coefficients of supports on the stiffness during vibrations and loss of stability. To solve this problem, the approximation of the nonlinear coefficients of the supports by the least squares method and the obtaining of quadratic approximating functions was used. As a result, the problem of determining the required stiffness of the supports brought to a fourth-degree resolving algebraic equation, for which an analytic solution exists. The obtained solution allows the stiffness of the beam supports, which provides the required value of the first natural frequency of vibrations of the beam and its first critical load in the form of external compressive force or temperature effects. Replacing the nonlinear dependencies of the support coefficients with the stiffness of the supports with simpler quadratic functions led to relatively simple analytic dependencies that allow the resolution equation to be transformed according to the particular problem being solved. At the same time, quadratic functions influenced the calculation error, to reduce which, the range of the support stiffness under consideration was limited and divided into three zones. The results of calculations using the proposed analytical solution were compared with numerical calculations using finite element method. The comparison of the calculation results showed an error of not more than 5 % for the considered range of stiffness of the supports, which is quite enough for engineering calculations of beam structures. To limit the error of the result, it is recommended that the stiffnesses of both supports be equal or of the same order.

Traditional solar simulators for thermal vacuum tests of spacecraft are based on gas-discharge lamps. Due to the characteristics of such lamps, they can only be installed outside the thermal vacuum chamber. High-efficiency LEDs can be installed directly in the thermal vacuum chamber, which can significantly improve the luminous and operational characteristics of solar simulators. Obtaining a spectrum close to the spectrum of the extraterrestrial Sun (AM0) is one of the primary and most difficult tasks in ensuring that the luminous characteristics of the solar simulator meet the requirements. The article considers a previously proposed model of a combined emitter consisting of halogen lamps and assemblies of high-performance LEDs of various wavelengths. We have proposed a method for determining the spectral match for AM0 solar simulators and determined the requirements for LED assemblies intended for use in the combined emitter. Simulation with a sample of the most suitable commercially available LED assembly, at the nominal power level of halogen lamps, showed a good spectral match, which deteriorates significantly with decreasing lamp power. At the same time, many programs and methods of thermal vacuum tests require simulation of different irradiance levels. Taking this into account, the authors developed an experimental LED assembly. Simulation of the combined emitter with this LED assembly showed the best results. The required spectral match is maintained at various irradiance levels. The achieved characteristics of the developed LED assembly are not limiting and can be improved by further optimization.

Study of the materials for spintronics operating under extreme conditions based on manganese selenides substituted with gadolinium are investigated. The technology of synthesis of solid solutions based on solid-phase reactions using MnSe and GdSe compounds is presented. As a result, Mn_1-xGd_xSe solid solutions with concentrations x = 0.05; 0.1; 0.15 and 0.5 were synthesized. The synthesis was carried out under vacuum conditions of 10^–2 Pa. The products of the primary synthesis were subjected to thorough grinding into powders, from which tablets were made under pressure for homogenizing annealing at 1370 K. After two hours of exposure, the synthesis products were tempered in cold water. At the final stage, homogeneous strong ingots of grayish-silver color were obtained. X-ray phase analysis of synthesized solid solutions of the Mn_1-xGd_xSe system was performed in Cu-K_a radiation in the point-by-point measurement mode with a scanning step along the angle Δ2θ = 0,03 degree, the time of information collection at the reference point Δτ =3 seconds. The spatial symmetry group and the parameter of the elementary crystal cell of solid solutions of the Mn_1–xGd_xSe system from X-ray diffraction analysis are determined. The dependence of the parameter value of the crystal lattice of solid solutions on the concentration of gadolinium ions is found. The specific magnetization was measured by the ponderomotor method in a magnetic field with an induction of B = 0.86 Tesla and the magnetic susceptibility of the samples was determined in the temperature range of 80 ≤ T ≤ 950 K. The cycles carried out in the heating – cooling mode did not detect a change in properties. The Neel temperatures and the paramagnetic Curie temperature are determined from the Curie – Weiss law depending on the concentration of a rare earth element. A decrease in the temperature of the magnetic phase transition is established.

Zirconia has a high dielectric constant and high thermal stability. There are many methods for the synthesis of nanocrystalline materials from zirconium dioxide. These include hydrothermal synthesis, gas-phase chemical reactions, cryochemical synthesis, plasma chemistry methods - these methods are expensive and complex. In this work, we propose a relatively simple method for controlling the growth of zirconium dioxide nanocrystals by synthesis in polymer templates (template synthesis of inverse opals). Inverse opals have unique physical and chemical properties, so they can be widely used in optics, optoelectronics, biological research, catalysis, functional ceramics, which is also relevant in the rocket and space industry. As a starting material, we used a water-alcohol solution of zirconium oxychloride, with which we impregnated templates of monodisperse submicron spherical particles of polymethyl methacrylate. After impregnation of these templates, the solution solidified in a limited pore space of 20–40 nm. After that, we fired the resulting templates to remove the polymer matrix. In this case, structures consisting of zirconium dioxide nanocrystals were formed. Using the methods of scanning and transmission electron microscopy, we assessed the morphology of the obtained materials, and showed that under conditions of limited diffusion, zirconium dioxide forms crystals with a size of 10–30 nm. Also, depending on the calcination temperature, materials with different crystalline modifications are obtained. As a result, we have shown that aqueous-alcoholic solutions of zirconium oxychloride are a convenient means for obtaining nanocrystalline materials, including inverse opals from zirconium dioxide, by template synthesis.