Aerospace Systems最新文献

In this paper, a method is proposed for calculating the bearing capacity of composite reinforced wing box panels under compression after impact, which has improved calculation accuracy and accelerated analysis time. The paper describes a method for two-phase calculation of the bearing capacity of reinforced panels, taking into account defects, based on the transfer of the stress–strain state from the global model to the local one. To implement the method, a discrete finite element mesh of the study area and a local model of the reinforced skin are created. The method of two-phase analysis of the bearing capacity of reinforced skins with applied impact defects consists of two main components. The first phase is a static calculation of the global shell model of the entire structure under critical loading conditions—the design case that takes place during the flight of the aircraft at small positive angles of attack, in which the aircraft realizes the maximum lift and torque for a given aircraft. In the second phase, a detailed local solid model of the studied area of the reinforced skin is prepared and a dynamic impact analysis is performed. Next, compressive force flows or displacements are transferred from the global model to the closed contour of the local zone and a solution is made in a dynamic or static formulation. This article presents the developed method of global–local modeling, which makes it possible to analyze the bearing capacity of reinforced skin after impact with a more detailed grid without sampling the global model, which speeds up and refines the calculation.

The main objective of this paper is to evaluate the aerodynamic performance of a modified blended wing-bodied re-entry vehicle by computational fluid dynamics. This analysis examines the airflow properties like pressure, density, and temperature under hypersonic flow. The study of a blended wing model at different Mach speeds and angles of attack is also included in the research paper. All the simulations in this paper are performed using the computational fluid dynamics tool of ANSYS CFX. Shear stress transport (SST) turbulence computational fluid dynamics model has been used for numerical analysis. Various inlet conditions are applied to get the aerodynamic parameters. The results revealed that the best Re-entry condition is from 10 to 20 degrees angle of attack at Mach 22, and the vehicle is very stable at a high angle of attack and Mach number. The obtained results have been validated with the public domain literature. The blended wing body has been thoroughly examined in various important locations, particularly the spacecraft nose and flap sections.

Reliability is an applied scientific direction. Here, the methods of research of systems under conditions of occurrence and elimination of random events are used and developed: failures of components of these systems. Basic research methods and conclusions of reliability theory are of general nature and can be applied in any field of engineering. In this paper, a team of authors considered an urgent problem of modern production, which is an overestimated number of full-scale tests, which entails an increase in the cost of products. The aim of the work is to create a method for evaluating complex technical systems based on the results of testing its elements, in particular electrical circuits. The practical significance of the work is expressed in the application of the method in analytical calculations of the reliability of component parts based on test data in the design of new complex technical systems and complexes. Also, in the work, the types of system failures are briefly considered and classified, and a method for experimental assessment of system reliability is given. The most significant factors for the stage of statistical processing are considered and analyzed. The following is a review of the literature on the issue under study and several examples of the use of the method in practice, with confirmation of the accuracy of the result by practical testing. As a result of the work, it was obtained that if the estimates of the probabilities of failure-free operation of all elements of the system are the same, then the estimates of the probabilities of the states of systems with a failure of the same number of elements are also the same. As a conclusion, practical recommendations on the application of the method are presented, but also the experience of the authors in the operation of complex technical systems shows that the operational reliability is almost always lower than the level obtained from the calculation results. The inaccuracy is explained by the imperfection of the production technology and the low reliability of reference information.

When designing the compressed thin composite skin of a multispar flap box of a small aircraft, its buckling due to compressive forces at loads below the operational level is admissible. This work considers smooth orthotropic rectangular panels loaded with longitudinal compressive strength. To determine the optimal parameters of the panels, a method based on a postbuckling state involving an analytical solution of geometrically nonlinear problems obtained by the Bubnov–Galerkin method was used. In this paper, methods for determining the minimum thickness of orthotropic panels, for which supercritical behavior is permissible when subjected to compressive forces, are developed. They include, firstly, the approaches using various strength criteria given the static loading, secondly, methods allowing for the variation of the width of the panel when considering two levels of loading: ensuring limitations of buckling at the first level of loading and static strength conditions in the case of geometrically nonlinear behavior at the second level of loading, and thirdly, methods taking into account the requirements of fatigue cycling. Here, also two levels of loading may be considered, at which stability and strength are ensured under postbuckling behavior, according to the parameters of fatigue loading and permissible stresses with respect to fatigue strength. These methods are reduced to solving analytical ratios with respect to the thickness shown on the example of hinge-supported composite panels. Since the obtained analytical relations are associated with the initial stage of postbuckling behavior, the paper provides an expression for compressive forces, at which the number of half-waves can be increased under geometrically nonlinear behavior. Of practical significance is the possibility of determining the optimal parameters of smooth orthotropic panels under static and fatigue loading at the early stages of design.

The results of fatigue strength estimates, required for ensuring durability design goal of composite materials made upper and lower panels of the prospective supersonic transport aircraft (PSTA) wing are presented. Developed estimates of the fatigue properties are based on the approximations gained from published sources. Fatigue strength (S–N) equations for composite panels of the PSTA wing are deduced, which might be followed by procedure of compliance to service design goal. The methods developed are used to compare intact and required fatigue strength of original carbon fiber reinforced plastic (CFRP) and one with modified properties by nanoparticles inclusion. Finally, the sensitivity of the developed fatigue strength estimates to chosen parameters is studied. Developed methodology can be utilized during preliminary strength analysis of the PSTA wing panels.

This research paper deals with multi-target tracking in a MIMO radar system, which presents complex data that can result in correlation problems and create technical difficulties. The objective is to resolve these issues and prevent divergence in object-tracking scenarios. However, when the cross-path phenomenon occurs, the process of assigning target measurements in MIMO radar systems becomes more complicated, and the interference phenomenon can disturb the received signal and disrupt the state estimation process. We have created a new algorithm called AMC-JPDAF that is a combination of the particle filter with the adaptive Monte Carlo (AMC) method and the joint probabilistic data association filter (JPDAF). This replaces the conventional extended KALMAN filter (EKF) used in EKF-JPDAF. We incorporated an entropy calculation and resampling sub-algorithm to overcome the limitations of EKF-JPDAF, which resulted in a more accurate estimation of two crossing targets and reduced trajectory loss in various tracking scenarios. Our experiments demonstrate that AMC-JPDAF is effective in preventing possible divergence phenomena when simulating two intersecting drones tracking scenarios. We report that the coherent measurement ambiguity is resolved at the crossover point of the trajectories corresponding to each target, giving us a low trajectory loss rate of 3.9%, which is significantly better than the 18.7% and 10.8% reported by simulations that do not affect the trajectory estimation process. We employed the MATLAB software development framework to design a system that satisfies the goals initially established by AMC-JPDAF. We then validated the system's performance by using an experimental database collected from the MIMO-FMCW 8 × 16 radar system.

In the future, the stratospheric airship will be used to accomplish the continuous cruising mission in the widely distributed area. To solve the trajectory planning problem of a single airship continuously cruising multi-target regions, a global trajectory planning algorithm with the minimum energy consumption is proposed under the assumption of constant horizontal wind and cruising altitude. First, the singular perturbation method is used to plan the trajectory of the airship with minimum energy consumption in the long-distance straight cruise phase between each two target regions. This method determines the optimal yaw angle and cruising speed of the airship. Then, quadratic programming is used to solve the trajectory of the airship cruising in the target region by considering the smoothness and continuity of the airship's flight, the requirements of cruising time, and the constraints of speed and acceleration. Finally, the trajectory is optimized by considering the yaw rate constraint to strengthen the dynamic feasibility. Based on the above algorithms, we give a specific trajectory planning case in the last section.

This paper proposes a target orbit design scheme based on Pareto optimization for Earth observation satellites with injection error. To avoid high fuel consumption of satellite from injection orbit to original reference orbit, a new target orbit is designed. This target orbit not only requires low fuel consumption, but also can achieve no leakage coverage to the ground. First, the analytical model of sun-synchronous repeating orbit is established under (J_{{2}}) perturbation. Based on this analytical model, in the neighborhood of injection orbit, the feasible solution set of the target orbit is constructed. This solution set constitutes a discrete search list. Second, a multi-objective optimization problem about fuel consumption and ground coverage is established. As the feasible solutions are constrained in the search list, the optimization of continuous variables in continuous space is transformed into the optimization of finite variables in discrete space, which greatly reduces the optimization time. Meanwhile, a weighted parameter (alpha) is proposed. It represents the decision-maker’s preference for a specific indicator. Then, a preference function of fuel consumption and ground coverage is constructed based on (alpha). The preference function will help the decision-maker to select the most appropriate solution from the Pareto front. Finally, the above orbital elements are corrected under (J_{{4}}) perturbation by differential correction. The simulation results show that for satellites with large injection, maneuvering the satellite to the redesigned target orbit can save 97.36% of fuel compared with maneuvering to the original reference orbit.

Nowadays sandwich structures with foldcores have extensive applications in aviation and aerospace fields, which are considered better than honeycomb sandwich structures to some extent. This paper explores the thermal–mechanical properties of cylindrical sandwich structures (CSS) with four kinds of foldcores, including Axial Miura, Circumferential Miura, Diamond, and Kresling foldcores. Sequential coupled thermal stress simulation and axial compression simulation with ABAQUS are implemented to aluminum CSS with the four kinds of foldcores, which are subjected to mono-direction heat flux. Moreover, the simulation results are compared with that of CSS with honeycomb core, and compared the thermal mechanical properties of different structures and different (N) (the number of unit cell in one circle). It is found that with the increase of (N), the thermal mechanical properties of CSS with Axial and Circumferential Miura foldcores become better. Besides, CSS with multi-layered foldcores exhibit more uniform temperature distribution, which is favored in design of satellite. In addition, the strength and the stiffness of CSS increase as (N) increases and are lower with mono-direction heat flux than without heat flux. Especially, CSS with two-layered Axial Miura foldcores exhibit better thermal–mechanical properties than all the other models.

This study proposed a novel technique to solve the problem of color distortion in the fusion of the GeoEye-1 satellite's panchromatic (PAN) and multispectral (MS) images. This technique suggested reducing the difference in radiometry between the PAN and MS images by using modification coefficients for the MS bands in the definition of the intensity (I) equation, which guarantees using only the overlapped wavelengths with the PAN band. These modification coefficients achieve spatiotemporal transferability for the proposed fusion technique. As the reflectance of vegetation is high in the NIR band and low in the RGB bands, this technique suggested using an additional coefficient for the NIR band in the definition of the I equation, which varies based on the ratio of the agricultural features within the image, to indicate the correct impact of vegetation. This vegetation coefficient provides stability for the proposed fusion technique across all land cover classes. This study used three datasets of GeoEye-1 satellite PAN and MS images in Tanta City, Egypt, with different land cover classes (agricultural, urban, and mixed areas), to evaluate the performance of this technique against five different standard image fusion techniques. In addition, it was validated using six additional datasets from different locations and acquired at different times to test its spatiotemporal transferability. The proposed fusion technique demonstrated spatiotemporal transferability as well as great efficiency in producing fused images of superior spatial and spectral quality for all types of land cover.