2015. № 82
The paper considers the problem of a barbell shaped artificial satellite plane motions control. The satellite is modeled as a weighable rod with two point masses, fixed at its ends. The third mass point can move along the rod. The satellite motions in relation to its center of mass take place in Newtonian gravitational field. The barbell shaped satellite has two stable equilibrium positions in circular orbit.
The authors discuss the possibilities of a pendulum oscillation build-up and damping parametric control in the vicinity of low equilibrium position. Problems of the gravitational stabilization with reference to plane disturbances of diametrically opposite relative equilibrium positions of the satellite in a circular orbit are studied.
A continuous control law of a moving mass is formulated according to a swing-by concept. We implement the control law by continuous variation of the distance between the satellite center of mass and the moving mass. This control represents the function, depending on the phase state vector representative point of the barbell shaped satellite.
The goal of this paper is building new control laws with preset properties. These laws should realize the processes of the satellite oscillation build-up and damping in the vicinity of low equilibrium position. Moreover, they should provide the satellite re-orientation, while it moves from one equilibrium position to the other, diametrically opposite, as well as gravitational stabilization of the satellite two opposite equilibrium position in relation to the local vertical.
We solved the problem by the method of Lyapunov’s functions of the classical theory of stability.
In this paper control laws of oscillation build-up and damping, diametrical reorientation and gravitational stabilization in relation to the local vertical of the dumbbell shaped artificial satellite are built. The Lyapunov’s functions that prove the asymptotic stability and instability of the satellite two equilibrium positions in cases of its damping and oscillation build-up correspondingly are selected. It is shown that with controlled movements according to the first law the asymptotic damping of oscillation amplitude of satellite occurs under any initial conditions of the movements. When implementing control according to the second law the growth of the oscillations amplitude and transition from oscillatory to rotational motion takes place. Theoretical results are illustrated by graphical representation of the numerical results.
The results presented in the paper can be used for modeling and control of plane pendulum movements of various space mechanical systems.
Keywords: barbell shaped satellite, moving mass, gravitational torque, Lyapunov's function, asymptotical stability
Deformable body mechanics
In some aircraft engineering problems it is necessary to take into account different unsteady state effects. Such effects can occur, for example, when the aircraft contacts with small solid particles from the atmosphere. In such problems sometimes one has to take into account the movement of the load, produced by such particles. Also such problem can be interested in high-speed transport engineering. In general formulation of the problem, it is extremely difficult to analyze such effects.
In this paper the unsteady state response of a half-space due to a concentrated moving load is proposed. The half-space material is assumed isotropic, elastic and homogeneous. By means of the proposed method we found the solution of the problem and analyzed all possible singularities of the solution for different speed modes.
This problem is formulated in terms of elastic potentials. The load is modeled by means of Dirac’s function. In this formulation, the load has a random law of motion. After the problem is formulated, the superposition principle is applied. In this principle the Lamb’s problem solution is used as a Green’s function. After the general analysis, it is necessary to assume some definite law of motion of the load.
As an example, the case of load movement with constant velocity has been studied. The solution has been obtained and the result is analytical. A part of great interest play singularities of the solution on different speed modes and on some critical velocities. Such critical velocities like- speed of Rayleigh wave, and speed of elastic waves.
Such results can be used in transport engineering. Effect of Rayleigh wave as a result of train wheels and rails contact. Our results can help to find avoid such undesirable effects.
This is first time this problem was fully analyzed. In different papers only quasi-stationary or steady response was researched. Some authors obtained approximate solutions, our result is analytical and accurate.
Keywords: moving load, unsteady problem, superposition principle, singular integrals, regularization, solution singularities
Static and dynamic behavior of shallow shells under the influence of quickly changing temperature and force impacts
The paper investigates two classes of shallow shells, such as bicurved and constant twisting shells, based on desultory thermoelasticity.
The bicurved shell is subjected to linear temperature field through shell thickness as well as quickly changed power load along spacial coordinate on two opposite edges.
The constant twisting shell stays in convective heat exchange state with the environment through main surfaces. At a certain time instant, the external surface of the shell is subjected to a concentrated force for a time interval. During this time interval an abrupt change of temperature occurs (loss and restoration of thermal protection). It leads to temperature difference change.
Thermal conductivity and thermoelasticity solutions were obtained by trigonometric series superposition methods with variable coefficients over spacial coordinate and products of polynomials by the Heaviside functions. In case of constant twist shell we used double trigonometric series wing coefficients variable over time coordinate. Equations for coefficients of approximating series were obtained in closed forms that are extremely convenient for quantitative analysis. We obtained numerous 3D static images of bicurved shell deflection surface, and graphs of forms of deflection and middle surface points movement of a constant twist shell versus geometric parameters, BIO number and thermal and force effects.
Quantitative analysis of the obtained analytical solutions has revealed a number of regularities in the behavior of shallow shells subjected to quickly changed temperature and force effects useful for engineering analysis in well-known technical areas.
Keywords: generalized functions, thermoelasticity, shallow shell, statics, dynamics, amplitude, frequency
Fluid, gas and plasma mechanics
The paper presents the result of numerical calculation of isothermal and high-temperature turbulent jets based on average Navier-Stocks equations with modified turbulent viscosity model SST. The results of numerical computation were compared with experimental data. This work gives recommendations on using corrections to compressibility and temperature effects.
Correct modeling of supersonic jets is a difficult problem that includes accurate physical modeling of turbulence processes and shock waves. Parameters of isobaric supersonic jets have strong dependence on turbulence models. Thus, in this work we selected isobaric jets to simulate with LES and different RANS turbulent models.
After comparison with experimental data, the following have been detected:
1) k-w SST model with standard Wilcox corrections increases jets potential core length for supersonic high-temperature jets and decrease without these corrections.
2) This drawback for isobaric jets can be fixed by changing critical Mach number of turbulence fluctuations (Mt0), or by using Abdol-Hamid temperature corrections, that include total temperature gradient.
3) Developed recommendations for changing Mt0 depended on total jet temperature when Mach number is around two.
4) LES (WALE) model for isothermal jets have good compliance with experimental data. Though, high-temperature jets LES model increases the scale of turbulence and thus decreases the length of jets potential core.
Keywords: supersonic jets, turbulence, isobaric jets, jet potential core
In the linear approximation, we investigate the stability of elastic thin metal strip that is mounted in an absolutely rigid surface. The band has a periodic hinge reinforcement, thus, the band consists of a series of identical spans, separate span will be called a plate. All the edges of the plate is set hinged support. We consider small oscillations of the plate, which are described by the equation of motion of the Kirchhoff-Lyave. Oscillation occurs adjacent plates in opposite phase.
The band is streamlined with one hand supersonic flow, and the other is set to a constant pressure, which balances the band in a flat undisturbed state. Feed gas flows steadily perpendicular to the front edge of the plate. Gas modeled nonviscous and perfect. Perturbations of the gas is sufficient to consider potential. In the linear approximation of the motion is described by the wave equation.
Unsteady nonviscous gas pressure acting on the oscillating plate obtained from gas dynamics, has the form of two-dimensional integral of a combination of deflection plate and its derivative, with a core of special functions . This two-dimensional integral can be reduced to one-dimensional in the case of the strip, is a series of rectangular plates. Such a statement can be considered as a first approximation to the study of flutter isolated rectangular plate. Expression for the pressure in the limit of M → +∞ gives the formula piston theory, but at Mach 1 < M < 2 nothing to do with the piston theory is not, moreover, in this range, there is another type of flutter (singlemode), which is different from classical coupled mode flutter of plate. Single-mode flutter largely been studied in two-dimensional problem in ,  and , , experiments were conducted confirming its presence. In this paper we study the three-dimensional setting.
Further, given the fact that the pressure is expressed through the deflection plate, get one closed integro-differential equation of oscillations of the plate. Thus, the problem of stability in the linear approximation is the problem of finding the complex natural frequencies of the equation. This problem is solved numerically by the Bubnov-Galerkin method. The system is unstable if and only if at least one of the natural frequencies has a positive imaginary component.
In conclusion, in the linear approximation, we consider the problem of the stability of elastic bands. To calculate the pressure acting on the deflection of the plate, use the exact theory of potential flow of gas. For the first four frequency domains of instability in the plane (Lx; M) for different values of Ly. Where Lx and Ly --- dimensionless length and width of the plate (physical length and width divided by the thickness of the plate), --- the Mach number of the incident flow.
Keywords: panel flutter, flutter of plate, onemode flutter, flutter with one degree of freedom
While designing and constructing new aircrafts and space-rockets sometimes it is useful to perform a preliminary modeling of the design as applied to future exploitation conditions. This measure allows the designer to spot problem areas in the structure and flaws in organization of working process early in project development cycle.
In this document the problem of estimation the effectiveness of different type of fuel injection is considered. To solve stated problem a mathematical model is put together, including Navier-Stockes equations, chemical kinetics and turbulent model. In chemical kinetics the reactions of hydrogen combustion and air dissociation are taken into account. Hydrogen combustion is described by seven elemental reaction equations. Air dissociation described by five equations. This amount of equations allows for 80% of total impact on flow by chemical transformations, which is enough for a preliminary calculation. The chosen turbulent model is SST — Menter turbulent model, because it describes both freestream and near wall flows sufficiently enough. To solve the problem via numerical methods a tetra-mesh of 500 thousand elements was built. Computations were performed in quasi-stationary mode.
Verification of the mathematical model was performed using data from experiments conducted in the Institute of Theoretical and Practical Mechanics combustion laboratory, Siberian Branch, by P.K. Tret’yakov. The combustible used in experiments was hydrogen. Studies were conducted for adjacent and supersonic hydrogen injection into a scram-jet. The experiment facility was a profiled supersonic nozzle, from which hot air was dispensed. On the symmetry axis a pylon was mounted, thru which hydrogen came into the flow.
Some results of numerical simulation of supersonic combustion were given in this article. They correlate with experimental data fairly well. Based on these results it is possible to perform a numerical simulation of supersonic combustion in a scram-jet engine using the proposed mathematical model.
Keywords: hypersonic flow, Navier-Stokes equations, equations of chemical kinetics, Hydrogen combustion
Dynamics, strength of machines, instruments and equipment
Analysis of emergencies consequences resulted in space-based nuclear power plant reactor ground impact
Implementation of Nuclear Power Sources (NSP), including Nuclear Space Power Plants (NSPP), as onboard sources of electric power at space crafts (SC) requires nuclear and radiation safety assurance of such systems. Among other issues, it is required to assess a state of the nuclear reactor and its radioactive materials after emergencies related to an impact effect on construction.
The paper considers consequences of emergencies related to NSPP’s nuclear reactor ground impact. Emergencies occur due to failures of rocket carrier stages or unsanctioned NSPP exit from a nuclear safe orbit, such as NSPP collision with space debris (SD) fragments. Consequently, the NSPS’s nuclear reactor or its burnt section, containing an active zone (AZ), may fall down to the Earth surface.
2D model numerical experiments allow gaining a state of the reactor after an impact interaction with three types of surfaces (hard — granite, semi-hard — sandstone, water), draw conclusions on a radiation hazard level of the destroyed object, and then foresee measures for mitigation of radiation accident consequences.
Studies of consequences of reactor ground impact include the following stages:
— Development of a geometric model adequate to a calculation method;
— Calculation of shock-wave process parameters using special software developed;
— Analysis and interpretation of the obtained results in terms of radiation hazard.
On studying the reactor destruction process during the impact in 2D formulation we consider several models resulting from intrinsic properties, namely: cylinder models representing the cross section of the reactor, and two-dimensional model.
Geometric models of the reactor, developed according to the principles given in the paper and considered in the aggregate allow assessing the hazard of the destroyed object and a state of its nuclear material with a high degree of confidence.
Numerical modeling of the ground impact demonstrates that a destroyed AZ will be in undercritical state in all cases due to separation of the neutron-reflecting block and presence of safety bars containing Boron-10.
Keywords: nuclear space power plants, safety, emergencies, space debris, impact, radiation consequences
Some specificities of the finite difference approximation of the boundary conditions of conjugation of elements of complex structures for the solution of nonlinear initial-boundary value problems
Some new methods of construction of conservative finite difference schemas and iteration procedures are presented. The mentioned methods are developed for the numerical simulation of static and dynamic deforming of compound cage structures that are widely used as supporting frames for aerospace complexes, for instance in launchers. It is supposed that the frames are made from the reinforced concrete; this fact does not reduce the applicability domain of the developed mathematical models. The Timoshenko’s beam model is used as a base element of the compound structure, therefore the effect of the low shear rigidity that is common for various structural materials (fibrous composites, reinforced concrete, e t. c.) can be efficiently accounted. The mathematical model is based on the nonlinear relationships of the middle flexure beams theory, the hypothesis of elastic behavior for the concrete, and the one of elastic-plastic behavior for the concrete reinforcement. The deformation plasticity theory is used to consider the elastic-plastic strain state of the reinforcement; the plastic strains initiation is modeled by the Mises yielding condition while the unloading is elastic. In the same time the initiation of cracks in the concrete is considered as well as their closure.
The Lagrange principle is used to derive the equilibrium equations for the compound structures, and the dynamics equation are constructed using the Hamilton’s variation principle. Various types of structural element conjugation are considered and the corresponding formulations of the boundary conditions are introduced.
To construct the discrete analog of the stated problem the finite difference approach is used for the spatial and time variables. The conservatism of the resulting schema and the convergence of solutions to exact ones are secured by the variation difference method. The accurate finite difference approximations for different conjugations of structural elements and the initial conditions are presented. The use of the quasi-dynamic formulation of the pseudoviscosity method for the static strain state of the compound structures allows one to construct the single-type iteration procedure for solution of both linear and nonlinear problems. The estimation of the optimum parameters of the iteration procedure are obtained and the convergence acceleration algorithm for the pseudoviscosity method is proposed for nonlinear static problems. In the same time the approximation of the second order time derivatives in the grid equations of motion by the finite difference operators of the second order of accuracy allows one to construct the unified finite difference schema for static and dynamic problems. This property of the developed method is useful for the computation of reinforced concrete structures of launchers subjected to the dynamic loads because of the possibility of efficient accounting of the initial static stress state induced by the gravitation.
The proposed algorithm of numerical solution of nonlinear initial-boundary value problems allows one to estimate the residual bearing capacity of compound frame structures after intensive dynamic loading of various type including the seismic ones.
Keywords: mathematical modeling, finite difference method, pseudoviscosity method, nonlinear deformation, composite reinforced concrete structures, approximation, stability, convergence
Combined numerical and experimental investigation of the deformed state and buckling of the meshed cylindrical shell subjected to the axial compression
A cylindrical shell of meshed structure with small axial and radial global stiffness is investigated both numerically and experimentally. The pre-buckling deformed state, the loss of the global stability of the equilibrium state with a straight shell’s axe, and the post-buckling state are studied. The experimental measurement correspond to the axial kinematic loading of the shell with one fixed end and other end moving with the fixed small velocity, so that any dynamic effect can be neglected. The deformation pattern is constructed on the groundwork of the performed tests and plotted in the frame «axial deformation — axial force». A critical force corresponding to the loss of the global stability of the initial equilibrium state of the shell is found as well as the ultimate bearing capacity of the meshed structure loaded by the axial force.
The test data are used to validate the finite element model of the meshed shell that is used as a basis of numerical simulation of the buckling and the post-buckling state. The finite element modeling is performed for both linearized and fully nonlinear problem’s statement accounting the plasticity of the shell material, the non-steady contact interaction of the cells of the meshed structure during the axial compression, and the effect of the dry friction on the global bearing capacity of the structure. The effects of all the mentioned nonlinearities are investigated, and the three-dimensional stress-strain state of the meshed structure is studied; the area of plastic flow are found. The deformation pattern corresponding to these numerical results is constructed and compared with the experimental measured one. Using the obtained results the numerical model is improved, the friction coefficient is adjusted, and finally the good correlation of the test data and the numerical simulation is obtained. On the groundwork of these results the methodology of the numerical simulation of the buckling and post-buckling of meshed shells with small axial and radial rigidities is proposed.
Using this methodology the numerical simulation of the meshed shell made from the titanium nickelide is performed. The buckling and the post-buckling state of the shell are simulated on the basis of the model of the superelasticity of the titanium nickelide. The area of the superelastic behavior are found. The deformation pattern is constructed on the groundwork of the numerical simulation results and plotted in the frame «axial deformation — axial force».
The obtained results as well as the proposed methodology of the finite element simulation of the mechanical behavior of meshed shells during the post-buckling deformation accounting the effect of the dry friction forces in the local contact area of touching cells can be used for the computation of special elements of power plants of aerospace technic as well as for the elements of the surgical technic like the coronary stents.
Keywords: cylindrical shell, meshed structure, plasticity, phase and structure transforms, deformed state, contact interaction, dry friction, buckling, finite element method
Influence of form rolling wave on a rectangular plate sound insulation properties of complex structure
Currently, the level and dynamics of development of new advanced aircrafts are making increasingly high demands on the degree of increase in noise and vibration protection. The same problems arise in other areas of new technology (machinery, transportation, automotive, and others.), Where it is necessary to ensure effective shumovibroizolyatsiyu.
In recent years, all these industries there a growing interest in the use of new functional materials that allow to obtain the desired level of noise and vibration protection design elements created by the organization of the right kind of their internal structure. This leads to the need to develop new sophisticated mathematical models to describe the behavior of structural elements taking into account the peculiarities of their structure. One such model used in this study.
This paper investigates the sound insulation properties of a rectangular plate, surrounded on both sides of the acoustic environment. The plate has a complicated three-layer structure (bearing layers elastic isotropic and anisotropic filler). Variants of the impact on the flat plate, cylindrical or spherical harmonic waves. For solutions used decomposition unknown functions in trigonometric series.
The purpose of work is to develop an analytical method for determining the absorption coefficient of sandwich plate in the acoustic environment, and the definition of its sound insulation index depending on the type and frequency of the incoming wave.
To solve the problem of the analytical methods used, which are based on the description of the occurrence of wave processes in various media via wave equations.
A method for modeling the process of absorption of vibrations in the audio range for different parameters of the plate and different types of waves, affecting the barrier. This method can be used in the problems of choice of optimum parameters of three-layer absorber.
The practical value lies in the fact that the evaluation methods obtained sound-insulating properties of the sandwich plate by reacting it with a different shape and frequency of wave action.
The resulting methodology allows the design of effective sound-absorbing barrier in the acoustic environment in the frequency band of interest impinging sound waves.
In this paper, based on the analysis of the interaction of elastic wave plate, a model of the elastic wave passing through a three-layer orthotropic plate with soft filler and symmetrical structure in the thickness.
We study the effect of the geometry of the incoming sound wave in the sound insulating properties of three-layer barriers.
Keywords: soundproofing, honeycomb, sandwich plates, cross-compression, trigonometric series
Aeronautical and Space-Rocket Engineering
It is known that on horizontal flights with low velocities vortex wake of main rotor rolls up, making two secondary vortex cores on the periphery of each wake. Top intensity of these cores is observed on the flight velocity V ≈ 10 m/s. There can be episodes when tail rotor of a helicopter is nearby one of these vortex cores. In this situation tail rotor happens to be in powerful unsteady field of induced velocities produced by vortex core and this may lead to sharp change in its aerodynamic characteristics, including significant rotor’s thrust drop. This fact can provoke flight accident, connected with tail rotor’s loss of efficiency and uncontrolled rotation of a helicopter.
The aim of the paper is computational modeling of main and tail rotors’ interference horizontal flight regime on low velocities with sliding.
The research has been conducted on the basis of non-linear blade vortical model of a rotor created at the department «Helicopter Design» of MAI and software package based on it.
For main and tail rotor’s of MIL MI-2 helicopter there was been modeled horizontal flight with angle of attack of main rotor αH = 0° and flight velocity V = 10 mps and slide (yawing) angles βH = −90...90°. As a newest of computation there were obtained dependencies of tail rotor’s thrust change (due to interference for two variants of its rotational direction) on slide (yawing) angle in relation with isolated tail rotor’s thrust at the same regimes. There is observed change of relative thrust due to interference from 68% to 174% (where thrust of isolated rotor is taken as 100% in each computational point) depending on tail rotor’s rotational direction’s, flight velocity V and slide (yawing) angle βH.
For the most typical regimes there is demonstrated a form of free vortical wake of main and tail rotor’s. There are analyzed reasons of interference and its influence on aerodynamic characteristics of tail rotor.
The results of research can be used in the process of rational directions of tail rotor’s estimation and evaluation resources of handling in yaw (directional controllability) in flight at different regimes with yawed low velocities flight.
Keywords: main rotor, tail rotor, computational methods of rotor's aerodynamics, non-linear vortical model, horizontal flight regime with a helicopter slip, rotors’ interference, aerodynamic characteristics
Numerical simulation of aerodynamic asymmetry and a method for providing lateral stability of maneuverable aircraft
The purpose of the work is studying of the possibility of providing lateral stability of maneuverable aircraft at high angles of attack due to the differential cluster deflection of wing leading edge flaps.
Working method consists of the analysis and numerical experiment.
Results of the work. The aerodynamic asymmetry is one of the reasons limiting the admissible angle of attack of modern maneuverable aircraft with wings extension.
Modern airplanes use deflection of wing leading edges to provide smooth steady airflow around the wing leading edge. We suggest to deflect only root section of the wing leading edge, which will allow fix the airflow separation on the front edge of the end sections and to symmetrize flow vortex structure.
A comparison of averaged values and the range of variation of asymmetric roll and yaw moments, as well as the lift-drag ratio of the test aircraft in various configurations deviation sections of wing leading edge flaps is performed.
The calculations were carried out using the method of detached eddy simulation, which allows you to accurately determine the frequency amplitude of asymmetric moments. The features of computational grids were used to calculate the aerodynamic characteristics of the aircraft by means of the method of detached eddy simulation are shown.
Analysis of the oscillation spectrum of the asymmetric rolling and yawing moments was carried out using a continuous wavelet transform.
Application area of the results. The results of this work can be implemented in scientific and design organizations engaged in development of aerodynamic configurations of maneuverable aircraft and control systems, as well as at aviation universities for educational process improvement
1. Maneuverable aircraft reaching high angles of attack is accompanied by asymmetric rolling and yawing moments.
2. The differential deflection of wing leading edge flaps of the wing at high angles of attack allows reduce the average values of the amplitude and low-frequency components of asymmetrical lateral moments acting on the aircraft.
3. The differential deflection of wing leading edge flaps leads to a slight decrease in the aerodynamic qualities of the aircraft.
Keywords: aerodynamic asymmetry, wavelet analysis, deflection of the wing leading edge flaps, detached eddy simulation
Methodical specifics of numerical simulation of a flow field near the rotor at a hover mode within the framework of computational grid methods with regard to vortex structure
A numerical simulation technique of a flow over a lifting rotor in hover mode is considered within the framework of Numeca FINE/Turbo software. For its validation, the test experiments by Caradonna and Tung for rigid 2-blade rotor are used.
This work is aimed at systematization of the factors determining accuracy of numerical solution for flow over lifting rotor problem, and testing numerical technique, which has a potential to attain an industrial applicability.
The main conclusion based on the review of present-day works lies in the priority of adaptation of computational grid in the area of vortexes. Resolution of tip vortexes at the scope of one rotation is sufficient for getting reliable values for pressure distribution coefficients and integral characteristics at hover.
The system of Reynolds averaged Navier-Stokes equations closed with Spalart-Allmaras and SST turbulence models was used as model of gas motion. The entire computational domain containing rotor blade is considered in rotating coordinate system with the terms responsible for action of the centrifugal and Coriolis forces taken into account. The numerical method is built on the basis of central differences scheme with artificial viscosity and local time stepping technique. The multigrid technology was used for its acceleration. Calculations in non-stationary formulation were performed to verify the obtained results.
Structured multi-block grids of H-topology with O-layer around blades generated semi-automatically with adaptation to boundary layer and vortex system region were used for calculations. Resolution of boundary layer by grid was ensured at the level y+ < 1 throughout the whole blade span (on average y+~0.1).
For evaluation of industrial suitability of numerical techniques criterion we proposed the criterion based on accuracy of pressure coefficient surface distributions: |δCp|<0.05. It corresponds to the typical experimental data error and ensures reasonable accuracy of integral characteristics.
Obtained numerical results stay in satisfactory agreement with experimental data. The structure of streamlines is in agreement with theoretical considerations. Coordinates of tip vortex correspond to Kocurek-Tangler model up to angular size of γ @ 360°.
Keywords: main rotor, aerodynamic characteristics, numerical methods, Numeca FINE/Turbo
Rocket and space engineering
Results forming scheme and technical solutions advanced spacecraft for the delivery and functioning lunar rover
The purpose of this work is the formation and selection of scheme and technical solutions (STS) spacecraft (SC) for the delivery and functioning of perspective lunar rover (LR) so that the weight of the transported payload LR was the highest.
At the first stage of the work carried out analysis of the components of the spacecraft systems with LR at various stages of functioning, analysis of the influence of their construction schemes on the total weight. When choosing STS system components SC with LR significantly affects the mass of opportunity of integration of systems, also it is necessary to take into account their interdependence.
In the second phase of the selected STS perspective spacecraft with LR as an element of the space complex of the domestic program of lunar exploration. In order to reduce the time and cost to develop considered the opportunity of use the developed landing platform (LP) spacecraft «Luna-Resource/1P» to deliver a perspective lunar rover. The problem is reduced to the determination of volume of necessary adaptation LP and development mobile platform LR to provide the maximum possible mass transported payload. In solving the problem have been chosen:
— arrangement of LR on the LP;
— volume of the necessary adaptation LR;
— options for creating service and special systems LP and LR.
The result of the work performed are STS perspective SC with LR to provide the maximum possible mass transported payload as well as the tools and methodology for the formation and selection STS any other spacecraft for the delivery and functioning planetary rovers.
Keywords: spacecraft, landing platform, lunar rover, scheme and technical solutions
Aircraft engines and power generators
Comparative analysis of pressure pulsations in designs of the tubular guide channels of the LRE screw centrifugal pump
An important task is to improve the LRE feed system turbopump vibration reliability. The most powerful source of vibration are high-speed screw centrifugal pumps. In the spectra of pressure pulsations, vibrations and dynamic deformation of the screw centrifugal pump casing dominate tonal components at the blade passing frequency and their higher harmonics. These fluctuations are due to unsteady hydrodynamic interaction non-uniform flow outgoing the centrifugal impeller with guide vane channels. Application of tubular guide channels allows smoothing the pressure pulse of the rotor blade passage, reducing the amplitude of the pressure pulsations and vibrations and significantly improving the dynamic strength of the structure. The mechanism of reduction of pressure pulsations and vibration of the pump casing when using tubular channels guide unit revealed. The numerical simulation of unsteady flow in the pump is undertaken to assess the designs and provide further optimization. Numerical analysis was performed using the method of «sliding grids». The calculation results and comparative analysis of variants of the guiding unit of the high-speed screw centrifugal pump outlined. In the computational experiments identified signals and spectra of pressure pulsations at different points of the pump outlet path, energy parameters and energy loss in the pump outlet path.
Keywords: srew-centrifugal pump, tubular guide channels, pressure pulsations, blade passing frequency
Keywords: helicon discharge, the mathematical model, non-uniform electric and magnetic fields, pulsed coaxial plasma accelerator
Experimental research of acoustical characteristics by power plant of aircraft «An-2« in static conditions
Work is devoted a community noise problem of light propeller aircrafts. In the paper the basic results of acoustical characteristics experimental research by light propeller aircraft (LPA) of «An-2» in static conditions are presented. Spectral and power characteristics of LPA power plant (PP) acoustical radiation and also directional characteristics are obtained.
The problem due to decrease noise of PP is rather actual for a general aviation LPA, whereas ICAO norms act on maximum community permissible noise levels of such planes . The given work is continuation of author researches [2,3,4] by acoustic characteristics of LPA power plants.
Measurements of LPA «An-2» acoustic characteristics have been carried out. The plane PP involves an internal combustion engine (ICE) «ASH-62IR» with 4-bladed propeller of variable pitches «AV-2». Measurements of acoustical characteristics were conducted at the various engine power settings determined by a rotational speed of a crankshaft.
As a result of the executed research it is installed that the basic share of energy (to 75 %) acoustical radiation of thу light propeller aircraft PP at moderate values of a Mach numbers of a rotor velocity (M) It is wet M<0,72 it is concentrated in the field of low frequencies (16-100 Hz) and the important role is played here harmonious and low-frequency broad-band by making radiations of a propeller and the reciprocating engine. At high rotor velocity Mach numbers, (M≈0,8) to ~94 % of acoustical energy of the PP it is radiated by a propeller, in the core, on harmonics of frequency of following of blades. The primary source of broadband acoustical radiation in the field of medium frequencies to 1000 Hz is the vortex sheet behind a propeller, and in the field of high frequencies over 1000 Hz a prospective source is interacting of a vortex sheet behind a propeller with system of an air cooling of the engine. The estimation of the contribution of various spectral components of acoustical radiation in total sound power of the aircraft PP is executed.
It is installed that acoustical efficiency of the aircraft «An-2» PP with 4-bladed propeller on the maximum power condition is equal ≈ 0,055 % that in 2-3 times more low, than at aircrafts with 2-bladed propellers.
Keywords: a propeller, propeller noise, piston power plant noise, light propeller aircrafts noise
Low-pressure compressor (LPC) operation has some peculiarities. First, the LPC stages operate with cold air. For this reason, transonic or subsonic flow exist in LPC. Second, the flow in LPC has complex spatial structure. LPC blade geometry is described by a large number of parameters. For this reason it’s difficult to pick up optimal combination of parameters manually. The solution of this problem is the usage of optimization methods to find the optimal combination of parameters. This approach was tested in this work. The main goal of this work was the LPC modernization for new parameters of gas turbine engine. The goals of the LPC modernization were as follows:
• the LPC total pressure ratio increase of 4% in comparison with the original LPC.
• the LPC rotation frequency increase of 2% in comparison with the original LPC.
• the LPC mass flow rate decrease of 11%.
• the LPC efficiency increase of 1%.
The LPC modernization was performed using optimization methods that implemented in the software package IOSO. To perform optimization the LPC numerical model was created using NUMECA FineTurbo software. It was verified before optimization by comparison of calculated and experimental LPC characteristics. The LPC numerical model was parametric and allowed changing geometry of all LPC blades. The total number of optimization variable parameters described the LPC geometry was 61. The optimization goals were the increase of LPC efficiency and decrease of mass flow rate. Thus, LPC efficiency and mass flow rate were used as the optimization criteria. The set of unimprovable solutions (Pareto set) was obtained as a result of solving optimization task. Pareto set was a compromise between the efficiency increase and the mass flow decrease. Each point from Pareto set had a correspondence with LPC unique geometry represented as an array of optimization parameters. One point of the Pareto set met all the required parameters of modernized LPC. The LPC geometry that guaranteed the efficiency increase of 1,3 %, the total pressure ratio increase of 4% and mass flow rate decrease of 11% in comparison with the original LPC was obtained as a result of the study.
Keywords: gas-turbine engine, axial flow compressor, numerical modeling, optimization, computational model, efficiency, IOSO, blade airfoil
Modern cryostatting systems find important applications in power and space transportation systems. The cryostatting system is a closed hydraulic loop for the thermal management and control of thermal modes of superconducting cable lines, cryogenic rocket and space units fuel tanks. The working medium is liquid nitrogen. One of the main components of such a system is the criorefrigirator. In the criorefrigirator compression scheme is used with following expansion of neon in the turboexpander, machine with gas-static bearings. Urgent task in the design phase is to determine the pressure fluctuations in the flow of the turbo expander and dynamic loading of the structure. This paper presents the numerical simulation of unsteady gas-dynamic processes in the turbo expander radial turbine flow. Expansion turbine consists of mounted on the same shaft the radial turbine impeller and centrifugal compressor first stage, that also serves as a gas-dynamic brake. Gas is fed to the expander casing through two pipelines. Further, it is accelerated in the nozzle cascade and enters the turbine impeller blades. After expansion and reduction the temperature, the exhaust gas passes through the axial diffuser. Rotor speed is 25,200 rev / min. The geometry of the computational domain is developed in order to capture the main features of the flow in the working fluid cavity, including the geometry of fourteen working blades and eight vanes of the nozzle cascade. The computational domain is divided into three sub-regions: the casing of the nozzle cascade, rotor, exhaust part. The problem is solved with the use of so-called sliding surfaces which serve for transmitting the data from the rotor, where the calculation is carried out in a rotating coordinate system into the stator zone accounting an angular displacement and sub-grid interpolation. Time step chosen from the condition to ensure the angular displacement in one time step within a single cell of the computational grid. The instantaneous velocity, pressure, temperature and Mach number fields are obtained with calculations. Few points in the nozzle vane channel oblique zones are selected to fix pressure pulsations. The spectral analysis of the data reveal that the tonal component with blades passing frequency dominates the spectra of pressure pulsations, its amplitude is above 7000 Pa. Calculation of loading on nozzle blade gives the amplitude of force 2 N and amplitude of momentum 0.03 N m
Keywords: criorefrigirator, turbo-expender, sliding surface, numerical modelling, pressure pulsation spectra, blade passing frequency
Determination of the thermal contact resistance between the composite materials C-Si-C and titanium alloy
Details connections made of new materials, which lack the information of their behavior in the connections, are often used in the problems of calculation of the thermal state of the construction of aviation and aerospace technology. Thereby, the problem of determining the thermal contact resistance between quite perspective materials — carbon-carbon composite materials and titanium alloys is considered.
The modeling of rough surface between two contiguous samples is performed. The finite —element model considering the peculiarities of surface micro relief is built. A thermo-mechanical calculation resulted into values of relative surface s shift, the actual contact area and temperature field is carried out.
Taking into account these temperatures contact thermal resistance for a wide range of pressures was calculated. Verification of the results was performed by comparing the correlation analysis with the results of the thermal contact resistance counted on the analytic dependence of a number of authors.
The presented method of thermal contact resistance calculation allows to find the values between the different materials used in the aviation and space industry. The results of calculations and comparisons with known dependencies showed that the method is adequate and its application does not require specific knowledge about the state of the contacting surfaces.
Keywords: contact thermal resistance, the contact area, the rough surface modeling
The aim of experiments performed was to develop the method of ramjet engine model testing in the wind tunnel with the simulation of incoming air flow and with thrust characteristics measurement.
Design / methodology / approach
For these tests the universal model of axisymmetric ramjet with the possibility of different fuels combustion was developed and fabricated. The ramjet of a pulling scheme includes a frontal air inlet and a combustion chamber with length of 380 mm. The model was installed in a wind tunnel by using of two supporting pylons, which by means of strain gauges were attached to the wall of the working section. The strain gauge readings give the total force acting along the axis of the tested model. There are a few openings inside pylons for hydrogen feeding. Model was equipped with thermal sensors and pressure gauges in order to obtain distributions of heat fluxes and static pressures in the engine channel.
Tests were conducted at M = 2.5 in the blowdown wind tunnel T-333 with a working section of Eiffel type. Stagnation pressure was P0 from 0.4 to 0.5 MPa, the stagnation temperature was T0 = 290 K.
A typical experiment with combustion constructed as follows. After wind tunnel working mode release the synchronization system was started that implement automatic feeding of fuel into the combustion chamber and simultaneously the inclusion of a pilot flame inside of the model. Burning of the pilot flame lasts 1 second only. The feeding of main hydrogen and its combustion was continued for a further 2 seconds after turning off the pilot flame.
After treatment, the test results showed that if fuel feeding and hydrogen combustion in the combustion chamber occur, then the drag of the model decreases due to appearance of the inner thrust. The maximum value of the inner thrust reached was 800 N with combustion efficiency of about 0.3-0.4. In the range of test conditions the heat fluxes pattern within the combustion chamber (in the vicinity of the critical section) does not exceed q = 1,3 MW / m2. The static pressure in the combustion chamber during the combustion of hydrogen does not exceed 0.28 MPa. Accordingly, the relative pressure within the chamber of combustion does not exceed the P / Pn = 9.6.
Results of this work will allow us to improve ramjet design methods and technology of ramjet testing in ground facilities with combustion and thrust characteristics modelling.
Originality / value
Taken into account the real complexity of the completed tests with combustion and measurement of ramjet engine thrust characteristics in conditions of incoming air flow they could be classified as unique.
Keywords: ramjet, ribbed air inlet, hydrogen combustion, wind tunnel, inner thrust
Innovation technologies in aerospace activities
Forecast analysis of scientific and technological development of Russia, USA, China and the European Union as the leaders in the world aerospace industry
The paper presents results of the existing international experience research in scientific and technological forecasting development of the space industry. Seven industry forecasts were analyzed in framework of this research made in the Russian Federation and abroad.
The following documents were chosen for the analysis:
1. Forecast of the Russian Federation scientific and technological development in the long term outlook (till 2030) (Conceptual approaches, trends, forecasts and conditions for implementation).
2. Forecast of scientific and technological trend development with significant applied potential in the long term outlook, presented by institutes of the Russian Academy of Sciences.
3. NASA (2010) National Space Policy of the United States of America. Washington.
4. ASI (2009) Strategic vision 2010-2020.
5. Strategic Options for Chinese Space Science and Technology.
6. NASA Strategic Plan 2014.
7. The ESA Technology Tree Version 3-0 Paris European Space Agency.
Deduction about the features of these forecast documents was made by results of the analysis.
1) A difficult search of risks, trends, threats and priorities should be referred to common features. Also there is no obvious connection «product—technology—market» in the forecasts, and because of that it had to be revealed on the base of the experience in the space industry.
2) There is a little congruence of foreign forecast documents with the Russian development plans (because of differences in the signification: foreign documents are accented on the industry, and the Russian ones — on the economy of the country), but there is a good field for comparison of the space industry priorities and key objectives.
3) American forecasts are based on the USA leadership and enhancing understanding of the achieved results in overall areas of the space science and industry, consolidation and performing the USA as trend and vector legislator of space development, including development of international standards.
4) Italian forecast is interesting with the statement of non repeating of research and development directions conducted in other EU countries, and it links own objectives with coordinating of the European Space Agency activities.
5) Chinese forecast is focused on the development of scientific and technological research and developments and does not infringe the issues of manned cosmonautics.
6) European forecast «Technology tree» is an applied document for compiling the strategy or target program of the industry. This form of forecast is recommended to use as an enclosure to the Russian forecast.
In these research the authors assessed the compliance of the Russian forecasts with the forecast of scientific and technological development of the Russian Federation for the period till 2030, with the forecast of longterm social and economic development of the Russian Federation for the period till 2030 and with the state and federal programmes of research and technological orientation.
Keywords: industry forecast of scientific and technological development, space industry, long-term forecast
The purpose of this paper is the choice of optimal design parameters of the hydrogenation reactor to provide a high conversion rate.
At a theoretical preparation phase a hydrogenation reactor simulational model for a selection of optimal temperature conditions with consideration for design specifics (using of «Comsole» and «LabView» engineering software complex) has been built.
A list of the model parameters which variation enables the reactor operating conditions to be close to the optimal ones is as follows:
― the volume rations of feed reagents CO2 and H2;
― the pressure of CO2 and H2 mixture in the reactor upstream ;
― the volume feed rate of the CO2 and H2 mixture to the reactor;
― the type and characteristics of the catalyst.
In the preliminary tests of the hydrogenation reactor prototypes, the following provisions have been obtained:
― an increase in the reaction temperature not lead to an increase in the conversion rate since the optimal heat condition for the conversion rate is reached in the narrow temperature interval inherent in every variety of catalysts;
― on order to obtain a stable authothetmal condition it is necessary to carry out the variable heat exchange along the reaction zone length since a decrease in temperature down to 120-140oC at the end of the catalyst bed allows the most optimal conversion rate be reached;
― the reactor unit proposed previously and enclosed in the capsule being at the same time a CO2 storage tank is considered as unsatisfactory as it is impossible to obtain a constant temperature due to the influence of the variable pressure in the tank on the value of heat exchange;
― the usage of advanced catalysts makes it possible to reduce the process temperature and ensure a quick reaction ignition.
Based on the research data obtained on a new design of the experimental reactor unit permitting usage of various types of catalysts, possibility of temperature monitoring along the length and diameter of the catalytic bed, dimensional and layout characteristics being selected based on models corrected in the course of experimental try-out of reactor operation has been proposed.
Keywords: long term manned spaceflight, regenerative air revitalization system, carbon dioxide reduction system, simulation model
Instrument making, metrology, information and measuring equipment and systems
It is proposed the device for measuring of saltationing grains’ parameters with an upgraded optical system and based on a combination of the interference method and the method of light scattering by particles, crossing the laser beam.
The proposed device consist of a laser, illuminated an acoustic-optic modulator (AOM), which is served voltage of high and low frequency from the control unit, two measuring channels with upgraded optics.
Laser module illuminates the AOM by an advanced beam, which is served voltages of the two closely located frequencies from the control unit, which allows us to create a interference pattern in the diffracted beam. At the output of the first AOM beams of the first and zero order are standed out. Grains are introduced into the measurement volume with the tube. When grains fly out through two beams, light is scattered on them and enters two measuring channels. The first channel is formed by a lens, photodetected module, phase detector and a frequency control unit, and the second — lens, photodetected module and a digital oscilloscope.
When grains fly out through the interference pattern in the first channel, light, scattered on it, will acquire the Doppler frequency shift, which is proportional to the grain’s speed with flying through measuring volume.
The second measuring channel allows to estimate the size of the saltation grain, using the amplitude and the shape of the pulse signal from the outputs of the photodetected module.
As a result of researching for the first channel we get that photodetector`s minimal detected power is 2,74*10-11 W. The signal-to-noise ratio is 26.37. And it is sufficiently for reliable reproduction of information.
For the second channel photodetector`s minimal detected power is 3,55*10-13 W. The signal-to-noise ratio is 253.5.
Accuracy of velocity measurement is about 5%.
The relative error in measuring the size is 0.86%.
Studies have shown, that using of proposed upgraded optical system of the device may extend the range of measurement saltation particles’parameters.
Keywords: laser module, optical-acoustic modulator, photodetector, lens, frequency meter, phase detector, digital oscillograph
The article deals with issues related to ground based infrared system for Sun tracing in automatic mode. The goal of the automated servo IR-system design is embodiment of regular Sun monitoring and measuring its radiation temperature with allowance for direction pattern overlapping by clouds. It will allow obtaining such atmosphere and meteorological objects characteristics as transmission factor of an optically semitransparent cloud, its optical density, optical thickness, as well as atmosphere transparency factor, atmosphere optical density in spectral range, and atmosphere turbidity factor.
IR-Pyrometer TI-315E mounted on viola-azimuthal mounting constitutes the main part of the complex. The range of measured temperatures is expanded due to compensation light filter up to 500 °К. The small angular size of an observed object required the design of high precision drive for viola-azimuthal installation.
To ensure constant Sun tracking independence we developed a tracking program using Sun ephemerides. It allows fixing Sun radiation temperature fluctuations caused, specifically, either by Earth atmosphere transparency changes, or by Sun disk overlapping by optically semitransparent clouds.
Practical significance of installation consists in the fact, that we suggested a particular solution of the problem. The paper outlines the design of separate units on a structural level with their main characteristics, and defines their interaction to provide operating control of overall system in automated mode. The indubitable advantage of the presented design consists in IR-radiometric system ability to operate during daylight, and its design supposes installation mobility.
Keywords: Sun, guidance, tracking, measurement, errors, infrared setting
The process of restoring the space object localization area in a low-quality picture implies a choice between two below-mentioned hypotheses.
1. Background emission is fixed
2. Object image is found in the picture
In the context of the second hypothesis the space object localization area is selected.
The transition from background to object or vice versa is followed by brightness jump located in the area of background/object border, provided that the background spectra and the hiss spectra are concentrated in a low-frequency region. Thus, we can find the transition from background to object using this assumption. As a result of the algorithm operation the found area of an expected localization of the object image is cut out from the original picture in the form of a square the size of which is multiple of the power of 2.
Definite quality characteristics of solution to the problem are recommended in order to estimate the algorithm efficiency and an informative value of the obtained results.
In the course of the work we’ve synthesized the robust algorithm of selection of a distant object of unknown shape in a low-contrast picture formed in the atmospheric vision system. The algorithm is stable in the context of a probabilistic description of complicated background conditions. A decision-making criterion concerning the image presence in the picture is recommended and the structure of parallel three-channel background information processing is developed. Estimation of the algorithm functioning quality is obtained by means of statistical modeling.
Keywords: optical image, space object, picture plane, processing algorithm, median filter, contour image
Information and measuring and control systems
Accuracy of determining the landing trajectory of aircrafts using a baro-inertial information and computing complex evaluation
This paper examines the problem of evaluating the accuracy in determining aircraft trajectories using a baro-inertial information and computing complex. The solution to the above-mentioned problem is proposed on the basis of application of complex mathematical modeling. Simulation of the motion of an aircraft during the landing flight phase on a glide path was carried out and the aircraft’s altitude estimation errors were obtained.
The algorithm implements simulation of an aircraft’s motion in a non-inertial coordinate system in accordance with the flight plan, the state of the medium of motion (with atmospheric variations), using general nonlinear models of aircraft performance, control system, comprising of aircraft optimal control algorithms for identifying required trajectories and control laws, aircraft stabilization and balance algorithms, measuring and computing complex based on a gyro-inertial block, barometric altimeter and onboard digital computing machine.
The novelty of this study consists in that the air data system (ADS) is simulated as accurately as possible in describing the aerometric part of the information and computing complex by using developed mathematical models of flow around an aircraft and airflow in pipelines of ADS based on numerical solutions of the Navier-Stokes equations.
The algorithm of the inertial block comprises of an algorithm that calculates the orientation angles and an algorithm calculating the velocity and coordinates. Determination of flight altitude based on the readings of the inertial systems is an unstable computing process. In order to ensure accurate determination of flight altitude, a method is used based on the co-processing measurements of the inertial system and air data computer. The study of the influence of aerometric characteristic parameters of the ADS (pitot-static system installation site, the diameter of the hole of the pipelines, pipe lengths, installation angle of the pitot-static system, and so forth) on flight altitude measuring errors (static and dynamic) is reflected in this paper.
The mathematical model of turbulence under development presented in this paper allows simulation of flow around the aircraft and airflow in the pipelines of the ADS.
The implementation of the developed model presented in the paper allows for solution of the above-mentioned problem, namely, for determining the installation site of the pitot-static system, for optimization of the pitot-static system, as well as for the calculation of the measurement errors of the pitot-static system. The calculated values of the errors Δ1Pst, Δ2Pst and dynamic distortions allow the prediction of errors in Pst in the ADC software in the ADC’s onboard computer in oder to implement distortion compensation.
The results obtained from this study allow estimation of characteristic parameters of the ADC impact on flight altitude measurement errors. It is shown that the dynamic distortion has little effect on measurement errors. The distortion on the flow angle of the pitot-static system and interference of the airframe and pitot-static system greatly affect the measurement error. For the accuracy in determining the flight altitude, it is necessary to utilize a co-processing of measurements of the strap down inertial navigation system and ADC.
Keywords: time scale, aircraft landing, baro-inertial system, information and computing complex, pitot-static system
Radio engineering and communication
This paper introduces artificial neural network (ANN) based approach to the problem of direction of arrival estimation. The optimal solution to the given problem is based on estimation using maximization of the likelihood function (known as ML method), which depends on the estimated parameter, i.e. the direction of arrival, and the data calculated based on the received signals. This method allows one to obtain estimation with high accuracy, but it gives no closed form of the estimator owing. Consequently, it has to be calculated via numerical solution of optimization problem which requires a vast amount of computational power. The alternative approach based on multilayer perceptron ANN with a special neuron in its output layer is presented in this paper. This network learned with deterministic learning approach is able to estimate consuming significantly lesser computational power at cost of a small accuracy reduction.
The paper includes theoretical explanation of the proposed approach and the structure of ANN used to obtain the estimator. In order to investigate the efficiency of the proposed approach, a set of numerical simulations was performed using the known model of passive radar system with ring antenna arrays. It is shown that the time required by the ANN estimator to perform a single estimation is 10 times less than time required by ML estimator, while the accuracy reduction is kept lower than 10% within the signal-to-noise ratio from −8 dB to 18 dB. The results also indicate the absence of the significantly important dependency between the accuracy of the estimation and the true value for the ANN estimator.
Keywords: artificial neural network, multilayer perceptron, signals and systems, model simulation, passive radar systems, Cramer-Rao lower bound
Radar support systems are the only source of objective information for the aircrew on their location on the ground and in the air; and for operational control groups — on the situation in the area of their responsibility.
One of the types of information support for an aircraft that allows formation and data delivery on the location of an aircraft on the ground and in the air for the crew, as well as command and control aircraft using the software of highest quality is radio engineering operations. Development of information technologies and their implementation in the subject area of control requires functioning and processing of large amounts of information to ensure aviation systems control. However, to date, the existing approaches to the substantiation requirements, selection criteria and evaluation of radar support of aviation operations need to be further developed. The specificity of the tasks and increased information requirements of the aircraft crew make it necessary to search for new ways of organizing radiotechnical support operations.
Thus, the objective need exists for new approaches to evaluate the effectiveness of such type of information to ensure aviation safety.
To evaluate the effectiveness of radar support for aviation proposes an approach based on the achievement of the basic requirements for radio-technical support as to the information processing represented in the forms of information units, information networks and information areas.
— Practical implications
Based on the analysis and implementation of aviation research the paper analyzes the main characteristics of radio-technical support quality as an information processing, and based on the analysis of the three groups overall performance efficiency of the radio-technical support of aviation operations. Based on a thorough analysis of the properties of the information processing, determining the quality of its operation, the system requirements for radio-technical support are defined, and private performance indicators of its operation are selected.
Originality and novelty of the proposed approach mean the development of the methodology for assessing the effectiveness of aviation radar support, different from the existing ones. It allows take into account the maximum number of factors affecting the quality of information for aviation support. The proposed method of radio-technical support of an aircraft efficiency will provide better and faster development of proposals for making a decision on the organization of aviation radio-technical support.
Keywords: radio-technical flight support, aircraft, efficiency, index, system survivability, information exchange
This paper focuses on search and systematization of technical solutions which provide the functioning of present multi-band systems. The paper also shows the main courses of modern antenna industry development.
The initial review and analysis of present dual band and wideband radiators for active phased antenna arrays manufactured in Russia and other countries.
The paper shows main directions of research and prototypes of wideband radiators and their characteristics. This paper also conducts the analysis of wideband and multi-band radiators, which are designated as perspective in Russian literature and in literature of other countries. Each radiator in this paper have its main advantages and disadvantages indicated, from which one may notice that desirable results may be easily obtained with wideband radiators because improvements in their directivity characteristics are only narrowing the operating bandwidth. The increase in construction complexity may help in obtaining the desirable directivity characteristics without bandwidth narrowing. It also may upgrade the narrow-band radiator with required directivity to reconfigurable radiator, which will provide the same directivity for each narrow band, obtained by increasing construction complexity.
Results of this paper may be used in development of the on-board radars apertures, to define their functionality and dimensions.
This review paper indicates that the most frequently used types of radiators for on-board radars are patch radiators. The results of this paper show that there are many types of multi-band and wideband radiators. This paper shows that multi-band radiators manufactured at present are more complex and less efficient than wideband radiators, but provide their bandwidth by construction complexity instead of directivity in wideband radiators, and it gives research direction in this field.
Keywords: Phased antenna arrays, multi-band antennas, wideband antennas
Radiolocation and radio navigation
The article shows the methods of synchronization transmitter devices in distributed radio systems. This systems primarily includes global navigation satellite system (GNSS), ground radio systems navigation (LORAN-C, OMEGA), pseudolite radio navigation system (Locata, DeckFinder), Multilateration system (MLAT). Correct work of those systems requires coherency of the signals which emitted by distributed transmitting devices- initial phases of emitted signals should be functionally interrelated. Process of synchronization provides a quasi-coherent emitting of the radio signal from phase center antennas of distributed transmitting devices. The synchronization algorithm is considered by the example pseudolite navigation systems. The considered pseudolite navigation system consists of two segments. The first one, which called system segment, includes a set of transmitter-receiver devices wich placed near the service area of the system and control and monitoring subsystem. The second one, which called user segment, are includes navigation equipment of the consumer of this system.
The considered algorithm belongs to the class of two way synchronization methods and doesn’t need calibration procedures for receiving and transmitting path of devices, but requires determination of distance between the phase centers of the antennas for each pair of devices.
The article showns that the synchronization accuracy depends on distances measurement errors between the phase centers of the antennas, and on the parameters measurement errors of radio signals from each device(pseudo-ranges and carrier phase). The standard deviation error of the synchronization transmitting devices is estimated at 0.01 ns, which comparable with accuracy of precise synchronization methods, such as TWSTFT (two way satellite time and frequency transfer). Synchronization of the transmitting devices is performed in the background during the main task operation system. This allows to reduce error noise of parameters measurements of radio signal by using filtering algorithms such as Kalman filter.
Keywords: synchronization, time scale, distributed navigation system, pseudolite system, Locata
In our days phase signal measurements are used in many radio systems. For example, in GPS, GLONASS or pseudolite navigation system (like Locata) carrier phase measurements allows to determine three-dimensional vector of coordinates with centimetre accuracy.
Carrier phase measurements have cycle ambiguity property. One of the most common algorithms for ambiguity resolution is the LAMBDA method. However, for correct operation of LAMBDA method requires a large number of measurements. For example, it requires at least 12 satellites for good quality operation in GPS when operating in the L1 band frequency.
In the article describes filter algorithm for determining three-dimensions coordinates vector of a static object. The algorithm is based on processing ambiguous phase measurements and allows minimizing number of measurements. In the proposed algorithm, the likelihood function of state vector is represented as a set of modes (points, particles) as is done in particle filter. In the paper are presented formulas for calculating the characteristics of each mode (point or particle) on a prediction and correction filter steps: position, value of the likelihood function and an integer ambiguity vector. On correction step is performed ambiguity resolution using the LAMBDA method.
In the article is shown results of work the algorithm on the example of processing signals from pseudolites navigation systems with small bases between transmitters. The size of the convergence region of the algorithm for case with 4...8 transmitters and different number of modes involved in the filtering process are shown. It is shown that already at 5 transmitters the convergence time of the algorithm is determined by 10 time samples. Also the case of using contrast ratio (the ratio of height of the two adjacent height mod) as an indicator of true ambiguity resolution was discussed.
Keywords: carrier phase, ambiguity resolution, LAMBDA, nonlinear filtration, pseudolite, local navigation system, GPS, GLONASS, Locata
Analysis of the possibility of using Quasi-Zenith Satellite System QZSS as a source of precise ephemeris for a high-precision positioning mode
Currently, an increasing number of applications, which is necessary to achieve centimeter-level positioning of the receivers of the global navigation satellite systems (GNSS). One way to achieve centimeter-level positioning accuracies is to use the Precise Point Positioning — PPP GNSS receiver mode. This mode of GNSS receiver operation does not require differential corrections from the base station, but its operation requires precise ephemeris. For this information could be used differential corrections transmitted from Japanese satellite navigation system (SNS) QZSS.
The paper discusses the use of data transmitted in the signal MADOCA-LEX SNS QZSS as precise ephemeris for organizing the Precise Point Positioning mode of GNSS receiver. For the analysis was made choice an alternative source of precise ephemeris to obtain positions in the Precise Point Positioning mode for comparing the quality of precise ephemeris transmitted by QZSS system and other sources. As these sources was also used posteriori precise ephemeris from service NRCAN, and real-time precise ephemeris from service CNES. The experiments have showed position accuracy in the PPP mode and the efficacy of the precise ephemeris from QZSS applying to the GNSS GPS and GLONASS.
The experimental results showed that in the Precise Point Positioning mode with precise ephemeris from QZSS system, user position accuracy can achieve in real time is less than 10 cm level and using precise ephemeris from other services is about than 4-5 cm. The loss of accuracy characteristics in PPP mode with precise ephemeris provided by QZSS system in comparison with the service CNES possible due to the fact that the experiment was carried out in Moscow. The quality of precise ephemeris supplied by QZSS in the European territory of the Russian Federation may degrade due to a loose network of base stations in this area. In the Asian area is possible the opposite effect, however, this assumption requires further research.
However, the accuracy of user position using precise ephemeris from QZSS system as correction information for Precise Point Positioning mode, allows using PPP mode to solve a number of tasks requiring high precision positioning.
Keywords: global navigation satellite system (GNSS), Precise Point Positioning (PPP), The Quasi-Zenith Satellite System (QZSS), precise ephemeris, GPS, GLONASS
The potential accuracy of the attitude determination of an object by means of global navigational satellite systems (GNSS) is considered in this article. GNSS is now widely used for a variety of technical problems, including the determination of orientation angles (attitude determination) of the object. There are two approaches to solve a problem of the attitude determination. The first approach is classic two-stage algorithms. The phase difference between signals received at spatially separated points is measured during the first stage. The information about angular orientation is extracted from phase shifts on second stage. Another approach is to use single-stage algorithms, immediately giving an estimate of the angular orientation. Such one-stage algorithm is presented in . The accuracy of attitude determination is characterized by a covariance matrix, which is described by quite complex Riccati equations. This fact does not allow getting required estimates of accuracy quickly enough. The purpose of this paper is to obtain general equations for calculating the potential (i.e. Cramer-Rao lower bound) estimation accuracy of GNSS-based attitude determination for an arbitrary number of reception points and their arbitrary location. Equations to describe attitude determination problem, GNSS signal model, likehood function are presented in the paper. Such equations are obtained and their analysis is given in the article. As shown in the article the increase of reception points quantity can decrease the most likely RMS of attitude determination. The RMS value of the orientation angle is approximately 1.5 arc. min. when 10 GNSS signals are received at 6 points with maximum distance between them 2 m.
Keywords: global navigational satellite systems, attitude determination, Cramer-Rao lower bound
Informatics, computation engineering and management
System analysis, control and data processing
Development of a prototype intelligent system operational monitoring and the technical condition of the spacecraft onboard computer
For today, practically any onboard complex belongs to the class of difficult technical systems. Therefore, improvement of quality of functioning and definition of full technical condition of onboard systems is an important problem. In providing the demanded level of quality of functioning and reliability of difficult technical systems the special role belongs to various methods of diagnosing, after all mission of all device depends on work of these systems, and working capacity loss at least of part of onboard system is inadmissible today.
Therefore, the main task of any designer of onboard systems is an assessment of quality of reliability of the onboard equipment. However, ideal «working capacity» and full «not working capacity» in practice meet very seldom, these states are now certain boundary a state on a scale of all possible conditions of the spacecraft rather.
At this stage of development of onboard systems, complete control of a state is exercised through the analysis of telemetric information. We will consider as it occurs. Some information shots about a condition of a certain onboard system prepare, then they are prepared in a format for transfer on a land complex of reception of telemetry, then there is a communication session after that the telemetry is analyzed and if in information there are any shots which it is required interventions of land operators, information transfer about reconfiguration of «critical» system is made. It is not difficult to track a long chain of interactions.
Here it should be noted that all emergencies share on parried, i.e. expected and not expected. In addition, if information in telemetry indicates not expected emergency, time for decision-making on parrying of such situation can extend very strongly in time, this time can be fatal, especially if the device calculated on development of distant space.For the reason that possibility of the automated identification «before — defective» states onboard KA isn’t provided, all this doesn’t give the chance of a prediction of a condition of KA on the following communication sessions and doesn’t allow to take in due time a measure on prevention of hardware failures.
Keywords: intellectual system, diagnostics, monitoring of a status, operational monitoring
Control automation of technological processes
Nowadays additive manufacturing technology is rapidly developing. Therefore questions of using materials, software and equipment for additive manufacturing are actual.
The goal of this work is development of program components for work preparation of additive manufacturing (PCWPAM) differing from the state-of-the-art by the possibility of functional enhancing and adaptation to new production objectives.
To achieve the assigned objectives we solved the following problems:
As a result of this work we obtained software components for process design with the following performance capabilities:
We carried out a validation of generated G-code instructions with extraneous software (Polygon for Designer). The validation demonstrated correctness of methodologies and algorithms included into PCWPAM.
According to generated G-code we carried out the «control» printing of a part without any extraneous software. It proved the efficiency of the developed software components for additive manufacturing process design.
The similarity of additive manufacturing operating procedures allows speaking about applicability of the developed software components for other technologies of layer-by-layer synthesis either.
Keywords: additive manufacturing, software, production tooling, chamber composition, generation of layer by layer view, G-code
Mathematical support and software
FPGA (Field Programmable Gate Arrays) are powerful tool for rapid development and can replace specialized chips of high performance of ASIC (Application Specific Integrated Circuit). The configuration of FPGA can be updated remotely, using the Internet. It makes does FPGA more attractive than ASIC. The configuring bit sequence of FPGA is stored in an external bulk non-volatile memory and transferred to internal static memory after switching on the device. It contains the complete information about a functionality of FPGA, operation modes of input/output ports, coordinations and communications of all used components. In the article the mechanism of conversion of device description in language of the high level in the configuring bit sequence which is written in the external bulk non-volatile memory of FPGA is considered. On the basis of the analysis of the considered conversion the families of bit flows corresponding to the given schematic diagram are selected. As an example unremovable redundance of a bit flow for switching node of a programmable array of connections is considered. The programmable array of connections is responsible for all communications between logic blocks of FPGA. Switching in a node of a matrix is carried out by field transistors, and each connection is controlled by one bit of the configuring bit sequence. Redundance of the configuring bit sequence is defined by number of possible options of switching and number of the involved bits of the configuring sequence. For xc3s1200e chip redundance makes about 35%. It is offered to consider possibility of assembly algorithms implementation of the project on FPGA using the model considering redundance.
Keywords: FPGA bit stream, switching matrix
Mathematica modeling, numerical technique and program complexes
This paper presents a new class of cross-platform Web applications as a component of the National Geographically Distributed Information System for Remote Sensing Data Receiving, Processing, Archiving and Dissemination (ETRIS DZZ) that extends the possibilities of this system. A set of client and server components is proposed for server-controlled automatic local storage and updates of Web application code and data cache to provide offline capabilities and eliminate the need for constant connection to the server to allow client Web applications work offline with the data obtained before during periods of connection failures or in those areas where connection to the server is unavailable.
The requirement of offline ETRIS DZZ data handling is connected, firstly, to the big volume of the requested data (can reach hundreds of megabytes per session), and rather long period of that data relevance. It’s irrational to reload unchanged data each session. Secondly, many end users don’t have the possibility to load a large amount of data because of a bad connection to the server. Apart from the large amount of remote sensing image data with a long period of relevance, there are text and vector analysis results layers, which also have a certain period of relevance, allowing caching, and have a much smaller amount — up to ten megabytes per session. Moreover user each time loading constant overhead, which used to generate client interface, to load and display the data layers and provide a variety of portal services on the client side.
The proposed solution reduces the amount of traffic, the number of requests to server and meets the challenges of cross-platform, fault tolerance, and autonomy of the client application. As a result of this solution various kinds of devices, including mobile devices, can be used as terminals for ETRIS DZZ, store relevant data locally and update this information automatically.
Keywords: Earth remote sensing, satellite data, client applications for satellite data processing systems, mobile applications, offline-capable web applications.
The aim of the study is the geometric modelling of solar illumination on board the spacecraft or their position on the surface (or in the world, such as in the lunar settlements). At the same time explores the issues of their mutual orientation and shading at a given specific geometry of their arrangement. Addressing these issues should serve as a basis for the development of software and software of the automation system placement and orientation of the solar panels and hubs on the ground and on the spacecraft. The purpose of research — to assess the mutual shading of solar panels, both among themselves and with other entities (such as the space station).
The article shows the physical and mathematical formulation of the problem of optimization of placing solar panels in space or on the ground. The article shows that the mathematical formulation of this problem is seen as an optimization problem in mathematical programming, aimed at maximizing the use of these high-power sources in outer space stations and space colonies. The method of decision — geometric modelling space station and solar panels with a specific orientation. As a method of modelling the receptor used geometric model is sampled as the battery accommodation space, and the space station itself.
Based on the geometric model developed by the receptor software system created in C #, which allows to simulate the effective area of the solar concentrators. At the same time it developed a graphical shell, allowing to see the numerical value of the results. When the software package after you enter information about the geometrical dimensions of the station and solar panels (in parametric form), it is converted parametric geometric model in the matrix, and begins scanning stratified sections. Each layer is formed 3D matrix 2D matrix is like a slice of 3D matrix for a given distance. Each section (cut) receptor matrix calculates the area of this section of solar panels, efficient (cumulative) cross-sectional area of solar cells and the accumulated area of the cross sections of the housing space station. This accumulated area I is an effective working area of solar spacecraft given geometry and orientation relative to the sun, taking into account all types of solar shading.
The field of application of the results is to automate the design of spacecraft and geo-electric stations on the ground or space colonies. To develop mathematical and software allows you to estimate the effective area of the solar panels in the specific design parameters of the spacecraft and its orientation relative to the flow of solar energy.
Keywords: design automation, solar power, solar panels, spacecraft, heliostat, orientation, shading, receptor geometric models