Overview of electric pump units for spacecraft thermal control systems

The paper reports a brief description of spacecraft operating conditions, the main reasons of heating and thermal gradient appearance and need to reassign the thermal energy. Active thermal control systems and their advantages are considered, spacecraft for which the use of this type of thermal control systems is a priority. The electric pumping unit is pointed as a key unit of active thermal control systems. The electric pump unit is considered from the as the electromechanical system, its key elements are pointed. A description of the preferred pump types is reported and the types of active thermal control systems are briefly discussed. The foreign and domestic operating experience of spacecraft electric pumping units, the features of their designs are considered, the most common types of key elements are determined. Based on the results of the review, it is concluded that the most relevant layout of the electric pump unit is a centrifugal electrical pump with a brushless DC motor and hydrodynamic bearings. It is also indicated that the electric pump unit is a product with a long lifetime, which complicates the task of monitoring the technical condition in order to prevent failure.

Determination of the optimum ball radius for researching materials using ball indenting

The article discusses the study of the effect of a change in the radius of the ball in the injecting of the sample on the curve in the coordinates «load – indentation depth», the deviation of the indentation depth during elastoplastic indentation from the indentation depth with the elastic indentation and the amount of the axial deformation of the ball. The study was conducted using the Ansys Mechanical APDL program implementing the fenite element method. In the process of the study, it was found that with a change in the radius of the ball, there is no obvious change in the behavior of the sample material, and the deviation of the indentation depth during the elastoplastic indulgence from the indentation depth during the elastic indentation is not dependent on the size of the ball radius. There was also an effect of changing the radius of the ball on the size of the axial deformation of the ball and proposed a formula for determining the size of the axial deformation of the ball for the ball of any diameter, which will determine the actual depth of the ball into the ball when using the balls of different radius.

Analysis of the umbrella-type reflector opening process on a stand with an active gravity compensation system

During the verification of the functioning of the transformed structures in ground conditions, it is necessary to minimize the effect of gravity in order to exclude the occurrence of additional loads on the hinge assemblies and opening mechanisms. To perform this task, when testing a transformable umbrella-type reflector, stands with an active gravity compensation system are used, in which the gravity compensation force is applied to each spoke of the reflector. However, when compensating for the gravity spokes of the reflector, the fixing point of the suspension cable does not coincide with the center of mass of the spoke, which leads to the appearance of additional moments of forces acting on the suspended structure. Therefore, as an object of research, a part of the reflector was considered, consisting of a spoke, with cords of a formforming structure attached to it and a mesh. A 3D model has been developed, using which the positions of the center of mass of the structure under consideration were determined in the key phases of the reflector opening. A computational analysis of the driving forces and moments acting on the structure in the process of disclosure is carried out. The degree of influence of the suspension point position on the inaccuracy of gravity compensation has been established. The results of the analysis presented in the article can be used as initial data for the development of an algorithm for the operation of an active gravity compensation system, which will be able to take into account the position of the suspension point and the center of mass of the structure relative to the axis of rotation of the spoke during the opening of the reflector, by changing the gravity compensation force.

Development and modeling of non-metallic form-forming rigger for manufacture of polymer composition reflectors for satellite antennas

Reducing the time for carrying out the strength analysis of a structure in the process of manufacturing shaping tooling using modern tools of virtual computer design and modeling, namely mathematical 3D modeling in a small-scale production with the use of additive technologies, is the main task. With the help of numerical discretization, the investigated model is divided into a finite set of elements, which can take any form of the element and be defined in different reference systems. This will make it possible to predict approximately numerically the behavior of the material during its deformation under the action of the given loads applied to the 3D model. The use of additive technologies with the use of modern computer modeling, which is based on software, is an urgent task. This approach will make it possible to develop equipment with a complex geometric shape, bypassing the stage of writing control programs and performing labor-intensive operations for the primary processing of the product. This method is based on the process of constructing a 3D model of the shaping tooling that repeats the shape of the reflective surface of the reflector, using modified high-temperature engineering plastics. The process of evaluating the effectiveness of the developed model is shown on the basis of strength calculations, safety factor, deformation, static stress and displacement. The results of the work can be used in the design and manufacture of dimensionally stable products of complex geometric shapes from non-metallic materials used in the aerospace industry.

Optimal deployment of the spoke of a largesized transformable reflector according to the hierarchy of criteria

The article discusses the process of controlling the angular motion of the spoke of a large-sized space-based reflector, taking into account bending vibrations. Currently, large antennas are actively used for receiving and transmitting data. When launching large structures into space, the problem arises of reliably deployment the spokes, since they are packed in a small volume to be able to be installed in a launch vehicle. Due to the possibility of various abnormal situations, such as jamming of elements, engagement of the net, it is necessary to re-deployment the antenna. Therefore, it is important to develop control algorithms that can reliably solve the problems of direct and reverse motion. In the process of deployment and bringing together the elements of the reflector, various deformations appear in the structure. When the antenna spokes are brought together, lateral oscillations make the largest contribution to the oscillatory of the transient process. Currently, elastically deformed elements are used to deployment large-sized reflectors, and a control program is also used. This prevents the control from being adjusted when the deployment conditions change. The paper investigates the possibility of minimizing the vibrations of a structure during its deployment by using optimal control algorithms in real time. The forward and reverse motion of the antenna elements is performed by means of a two-criteria hierarchy optimization. The results of numerical simulation of the optimal rotation of the reflector spoke are presented. The proposed algorithm allows you to choose the optimal control in emergency situations for various types of large reflectors.

Protection of precision spacecraft equipment from internal sources of vibration

The work is devoted to the protection of a spacecraft from the influence of unacceptable internal vibration sources. The urgency of reducing the vibration activity on board the spacecraft to improve the accuracy of the target equipment is indicated. A particular problem of vibration protection of the spacecraft platform from a vibration source – an electric pump unit of a liquid thermal control system – is being solved. The basic requirements for electric pump unit vibration protection have been determined. Possible ways to reduce the level of vibration excited by the electric pump unit on the surface of the spacecraft fixation are considered. Particular attention is paid to such vibration protection methods as damping and vibration isolation, implemented by installing special vibration protection devices between the source (electric pump unit) and the object (spacecraft) – vibration isolators and vibration dampers. The principles of operation of vibration dampers and vibration isolators, the most common materials for vibration dampers are described. Examples of constructive solutions for linear single-axial vibration isolators are considered, recommendations for the use of promising products are developed. Particularemphasis is placed on the use of metal rubber as a material for vibration isolators. With regard to a specific design of electric pump unit, a diagram of the spatial structure of vibration isolation is proposed. Formulas for calculation are given in detail, a mathematical model of the vibration isolation system is developed. The procedure for calculating the parameters of the system has been formed. Based on the model, the maximum possible level of vibration suppression in the mid-frequency region was determined. Minimum required number of operable pixels was identified for monitoring the water surface with sufficient accuracy and reliability.

Wave theory of the laminated plates with approximate consideration of the transverse shear

Composite materials are widely used in the production of aircraft for various purposes. Having several unique properties, composites, due to their heterogeneous structure, are poorly resistant to shock loads. Impulse action spreads inside the material in the form of stress waves, which are reflected on internal inhomogeneities, can overlap, and create very significant bursts of stress. This often leads to the well-known types of failure – spalling and delamination. Practice shows that these fractures occur almost immediately after the loading impulse. To verify the spalling strength, it is necessary to consider the initial unsteady phase of the response to the external impulse. There are sufficiently reliable theories to verify this strength; usually, they do not take transverse shear into account, otherwise the solution becomes unnecessarily cumbersome and poorly observable. Nevertheless, attempts are often made to refine the calculations by approximate consideration of transverse shear. This article presents the wave theory of laminated plates with approximate consideration of transverse shear. The possibility of specifying the calculation of impulse-loaded plates is considered. The inconsistency of the resulting model is proved.

The reliability evaluation of the water surface remote monitoring satellite equipment

The work is devoted to the reliability and effectiveness of the water surface remote monitoring space system. Analysis of existing monitoring methods has shown a high potential for using nanosatellites to solve the problem. As an object of study, 3U CubeSat was chosen with a payload placed on board in the form of a hyperspectral camera. To assess the reliability of the system, a mathematical model on the failure rates of subsystems is proposed. The structural and parametric reliability of the object was investigated in the Windchill Risk and Reliability software complex, taking into account the cyclogram of work and the specifics of the degradation process of individual components due to the influence of an aggressive space environment. To assess the effectiveness of the nanosatellite application, the dependence of the accuracy of determining water pollution on the operability of the photodetector was analyzed, since the photodetector is the central link in the transmission of optical information. The effective measurement of brightness spectral coefficients over the entire service life of nanosatellite is also obtained. Minimum required number of operable pixels was identified for monitoring the water surface with sufficient accuracy and reliability.

Stages of information support of development of on-board equipment for spacecraft

The ground-experimental testing of the elements of space technology is a crucial stage in the creation of space products, in fact, this is the ground «flight» of the devices being created. And how well the operating conditions will be reproduced at this stage and the successful functioning of the devices under the expected conditions is ensured, its successful operation in real flight during the service life depends. The radio electronic devices of the onboard equipment of the spacecraft are one of the essential elements that ensure the fulfillment of target tasks, which should confirm their readiness for the forthcoming work at the stage of groundbased experimental testing. The article discusses the stages of information support for the development of spacecraft onboard equipment, showing the ways to improve the technology of ground-based experimental testing of spacecraft onboard equipment. It is shown that at the present stage of development of the space industry, it has become possible to introduce the methodology of mathematical planning of an experiment into engineering practice. A backlog of applied work on radio-electronic topics h as appeared, showing the possibility of revealing in a full factorial experiment the influence of internal uncontrollable parameters (factors) of electronic components on the experimental results. This removed the obstacle to the implementation of the capabilities of the method in research and improvement of radio electronic devices onboard equipment.

Modeling the deployment of a two-link spoke of a large-sized space reflector taking into account the backlash

This article discusses the process of deployment a two-link spoke of a large-sized transformable space-based reflector. In view of the high costs of carrying out field tests, the construction of correct mathematical models is an urgent task. Currently, the creation of large-sized systems is actively developing. Such systems consist of several interconnected links. When delivered to a given orbit, the large-sized system is folded for placement in the launch vehicle. After entering the orbit, it is deployed to the specified operating state. A mathematical model has been developed for the deployment of the spoke, improved in terms of taking into account the separation of parameters depending on the length and time, which makes it possible to study the arising vibrations of the structure. It is important to take into account the backlash in the connections. Even small gaps in the spoke link connections can lead to a manifold increase in the stabilization time of the system. The developed mathematical model makes it possible to consider various conditions for linking links, change the mass-dimensional parameters and materials of the spoke. The results of modeling are presented, showing the correctness of mathematical models. Conclusions are made about the admissibility of using mathematical models for spokes consisting of a larger number of links.