Vol 21, No 4 (2022)

The article presents the theoretical foundations of automated design of on-board equipment layout in spacecraft compartments in terms of topology. The purpose of the work is to create a flexible arrangement model that would allow solving the problem for any configuration of the structure, taking into account the engineering and operational restrictions imposed on the objects located in a limited space. The technology is formalized according to the methods of the foundations of topology and in this work is demonstrated for a two-dimensional case by comparing it with a reference design-layout scheme. The functional, installation, dimensional, thermal, vibroacoustic requirements are taken into account with the mass-centering restrictions of the layout. In the course of the study, a new approach to describing the design process of assembling on-board equipment was obtained, which can be fully digitized and then integrated into known computer-aided design systems. It has been verified using the example of the power supply system of the “Yantar-2k” spacecraft.

The tasks performed by modern military aircraft are currently expanding, as they are solved both in the air and in the aerospace, at high altitudes and at high flight speeds. However, in this case, the use of turbojet engines operation on aviation kerosene is not possible because of the high temperatures of aircraft structural elements due to aerodynamic heating that leads to the destruction of kerosene and the impossibility of using it as fuel. It is necessary to search for alternative fuel options, one of which is cryogenic fuel. This article substantiates the possibility of using cryogenic fuel, in particular hydrogen, for aerospace plane engines. Hydrogen has higher energetic qualities compared to aviation kerosene. The necessity of cooling the air before it enters the engine at high flight speeds of the aircraft has been proved. A design of the heat exchanger for cooling the air entering the compressor is proposed, and a method for its thermal calculation is developed, which is necessary when designing the structural layout of aerospace plane propulsion system.

The purpose of this work is to determine the influence of the optical characteristics of a thin multilayer solar sail on its orbital motion. First of all, the influence of the coefficients of reflection, scattering and absorption is investigated. These coefficients are computed on the basis of a mathematical model of the optical characteristics of a multilayer epitaxial thin film which is a solar sail itself. The paper considers the effect of temperature changes and sail surface degradation on its optical properties. Modeling of changes in optical characteristics is carried out drawing on an example of heliocentric flight from the Earth to Mercury applying locally optimal control laws. Applying the transfer matrix method and considering the distribution of solar spectral radiation optical parameters for two distinct constructions of a solar sail were obtained (aluminum and silver front coating).  

The study addresses the effect of thermal treatment on the mechanical properties and grain size of magnesium rich alloys with small scandium additions 1570, 1580 and 1590. The effect of preheat temperature (within 260…440 °С range) and soaking time (within 2 – 100 hours range) on yield strength, tensile strength and relative elongation of the alloys under investigation  was analyzed. Mechanical properties were determined using uniaxial tensile tests in accordance with ISO 6892-1. In addition, for some modes the microstructure was studied for Al3Mg2 β-phase presence and distribution by optical metallography methods depending on thermal treatment conditions. The studies demonstrated that supersaturated solid solution in the 1570 alloy decomposes faster in the entire studied temperature range, and after 48 hours soaking, its strength properties start degrading. At the same time, the 1580 and 1590 alloys are much more thermally stable, with slightly lower yield strength after long soaking time, while tensile strength remains unchanged. The conditions of 260 °C annealing temperature are not favorable for plastic properties, severely degrading (due to β-phase formation) in the 1570 and 1580 alloys. Plastic properties degradation is not so evident at higher soaking temperature, however, the 1590 alloy maintains the highest plasticity indices.

Microcells were designed for subsequent modeling of piezoelectric and optical elements on their basis. The development of piezoelectric and optical elements from microcells was carried out and models were prepared for 3D printing. These designs can be used in practice as piezoacoustic or piezoelectric sensors if piezoelectric powder is added to their composition, for example, in ultrasonic flow meters, or used to create optical structures, for example, diffractive optical elements. The key characteristics and coefficients of piezoelectric structures, such as dielectric constant, conversion coefficient, dielectric loss coefficient, mechanical Q-factor, frequency constant, electromechanical coupling coefficient, piezoelectric charge coefficient, piezoelectric stress coefficient, elastic compliance coefficient, degradation rate, Curie point are analyzed. Elements produced by 3D printing will have properties different from those of elements produced by standard methods. These structures open up new opportunities for the development of ultrasonic research, mechanical engineering and instrument making.

Approximate analytical models are proposed for two types of multi-channel queuing systems with partial mutual assistance between channels and waiting in limited-size and unbounded queues. The incoming flow of requests is a superposition of several simplest flows. It is assumed that normative numbers of channels for servicing a customer that differ depending on the flow of incoming customer requests are established. In the systems of the first type the normative number of channels is not necessary: a customer is accepted for servicing if there are free channels in the system and the number of channels is smaller than the normative one. Service time is distributed exponentially with the average inversely proportional to the number of allocated channels. In systems of the second type the service of a customer is always performed by the channels of the normative number. Service time can be distributed arbitrarily (not only exponentially) with the average irrespective of the number of allocated channels. The paper presents the results of comparative analysis of the results of dealing with some tasks of designing service systems in a wide range of input data using simulation modelling and calculations based on approximate analytical models that allowed evaluating the application area of the latter and making a conclusion about their satisfactory accuracy. Examples of the use of models of technological processes of airport ground handling as queuing systems of the considered types are given.