As low-cost carriers (LCCs) continue expanding their networks and enhancing profitability through connecting services, passenger demand has become a critical factor in flight connection planning. However, demand is inherently uncertain due to economic cycles, seasonal fluctuations, and external disruptions, creating challenges for network design. This study proposes a flight connection planning model tailored to LCC operations that explicitly accounts for demand uncertainty. The model determines the optimal set of connecting itineraries to introduce over the existing network of flights, identifies promising transfer airports, and provides passenger allocation strategies across flights. We apply the model to Spring Airlines’ real-world network to evaluate its effectiveness. Results show that the proposed model outperforms the deterministic benchmark in feasibility and stability under varying demand scenarios. Specifically, under the same constraint of selecting up to 10 transfer airports, our model increases the number of connecting itineraries by 59.5% compared to the deterministic model and achieves a more balanced passenger distribution. Across 10 representative demand scenarios, the average standard deviation of load factors is reduced by 26.1% compared to the deterministic benchmark. Moreover, the deterministic solution yields a 22.9% failure rate for planned connections, while our model maintains 100% feasibility. These findings highlight the model’s value as a resilient, practical decision-support tool for airline planners.
Modern aircraft design, including both manned aircraft and unmanned aerial vehicles (UAVs), faces computational challenges balancing aerodynamic efficiency, structural integrity, and weight optimization within practical timeframes. Conventional high-fidelity methods create bottlenecks that limit the design space exploration essential for UAV development. This paper presents a computational framework that integrates mesh-free structural analysis with generative knowledge-based engineering (KBE) and surrogate modelling for the optimization of rapid automated UAV wing design. The methodology combines the formalization of classical aerodynamic and structural mechanics knowledge with programmable CAD integration using the open-source Python package CadQuery. The developed framework automatically generates parametric wing geometries, extracts geometric properties, including cross-sectional moments of inertia and volumes, and performs structural analysis without mesh generation or finite element preprocessing. Aerodynamic loads are estimated using reusable meta-models from CFD studies stored as B-spline approximations in SplineCloud, enabling decoupled workflows and rapid evaluation.The mesh-free algorithm implements the numerical integration of beam bending equations, incorporating distributed aerodynamic and gravitational loads with variable cross-sectional properties. This eliminates the computational overhead of mesh generation while maintaining sufficient accuracy for preliminary design. The workflow is embedded in a KBE wing model, automating geometry generation and structural evaluation for swept wings with variable materials and geometries. The validation studies used three NACA airfoil families (2410, 2412, 2415) across aspect ratios (6-9), sweep angles (12°-18°), and spans (500-2500 mm). Individual evaluations completed in ~20 seconds versus hours/days for FEM simulations, achieving 2-3 orders of magnitude efficiency improvement. Generated 2nd-order meta-models enable sub-millisecond response evaluations suitable for iterative optimization requiring thousands of evaluations. This research advances automated design methodologies, providing computationally efficient alternatives to high-fidelity approaches while maintaining engineering accuracy for preliminary optimization. Open-source implementation ensures accessibility for the UAV design community. Future work will focus on FEM validation, aeroelastic coupling, and extensions to complex configurations.
Refractory high-entropy alloys（RHEAs） are widely used in the aerospace field due to their excellent high-temperature performance. This study employs multi-wire arc additive manufacturing（M-WAAM） technology to fabricate Ta1.5Mo1.5Nb0.5Zr2Ti refractory high-entropy alloy. Using equipment such as optical microscopy（OM） and high-speed cameras，the influence rules of base current，peak current，and peak time ratio on forming quality are investigated. The optimal process parameters for preparing the Ta1.5Mo1.5Nb0.5Zr2Ti alloy are determined（base current 100 A，peak current 300 A，and peak time ratio 35%）. Metallographic characterization demonstrates that the fabricated components exhibit excellent forming quality，with unmelted area ratio below 10% and porosity less than 0.5%. To address the melting point differences among various wires，hot-wire technology is employed to facilitate the melting of high-melting-point Ta/Mo wires. For the first time，we propose a“single droplet pre-alloyed transfer”mechanism，elucidating the thermodynamic process of discontinuous liquid bridge transition and subsequent formation of a unified molten droplet from four simultaneously fed wires. Based on the thermodynamic mechanism of synchronous four-wire discontinuous liquid bridge transition forming a unified molten droplet，a“single droplet pre-alloyed transfer”mode is established. Parts deposited under this droplet transfer mode demonstrate good macroscopic morphology and fewer internal defects. Through force analysis of molten droplets，we establish a mechanical model incorporating key factors including gravity，electromagnetic force，and plasma flow force， demonstrating that synchronous non-continuous liquid bridge transition of four wires constitutes a sufficient condition for the formation of a unified molten droplet. Additionally，the developed bead width prediction model provides quantitative guidance for process optimization. This work establishes an important theoretical foundation for M-WAAM of RHEAs.
Small air-launched unmanned aerial vehicles (UAVs) face challenges in range and endurance due to their compact size and lightweight design. To address these issues, this paper introduces a multi-phase wind energy harvesting trajectory planning method designed to optimize the onboard electrical energy consumption during rendezvous and formation flight of air-launched fixed-wing swarms. This method strategically manages gravitational potential energy from air-launch deployments and harvests wind energy that aligns with the UAV’s flight speed. We integrate wind energy harvesting strategies for single vehicles with the spatial–temporal coordination of the swarm system. Considering the wind effects into the trajectory planning allows UAVs to enhance their operational capabilities and extend mission duration without changes on the vehicle design. The trajectory planning method is formalized as an optimal control problem (OCP) that ensures spatial–temporal coordination, inter-vehicle collision avoidance, and incorporates a 3-degree of freedom kinematic model of UAVs, extending wind energy harvesting trajectory optimization from an individual UAV to swarm-level applications. The cost function is formulized to comprehensively evaluate electrical energy consumption, endurance, and range. Simulation results demonstrate significant energy savings in both low- and high-altitude mission scenarios. Efficient wind energy utilization can double the maximum formation rendezvous distance and even allow for rendezvous without electrical power consumption when the phase durations are extended reasonably. The subsequent formation flight phase exhibits a maximum endurance increase of 58%. This reduction in electrical energy consumption directly extends the range and endurance of air-launched swarm, thereby enhancing the mission capabilities of the swarm in subsequent flight.
Hugo Cintas, Frédéric Wrobel, Marine Ruffenach
et al.
The device downscaling of electronic components has given rise to the need to consider specific failures in onboard airplane electronics. Single Event Effects (SEE) are a kind of failures that occur due to radiation in the atmosphere. For the purpose of ensuring onboard electronic reliability, there is a clear need for new tools to predict the SEE rate, at both avionic altitudes and at ground level. In this work, we develop a new tool: RAMSEES (Radiation Atmospheric Model for SEE Simulation), which simulates the atmospheric radiative environment induced by cosmic rays. This multiscale and multi-physics phenomenon is simulated using the Geant4 toolkit, allowing the creation of a database to characterize the radiation environment in the atmosphere as a function of altitude. We show the need to simulate very high-energy particles such as 100 TeV space protons, because they are the main contributor of radiation at avionic altitudes as well as at ground level. Our approach shows a good agreement with the experimental data, the standards, and other models, and it also points out some discrepancies, especially below 18 km of altitude. RAMSEES can be the basis of the estimation of the SEE rate from ground level to the stratosphere, at any given position and time.
The application of thin composite material laminate secondary bonding technology to the main loadbearing structure of small UAV wings has important engineering applications for reducing the manufacturing costs of wing box section. A single-lap structural tensile shear test is carried out using a 2 mm sheet made of carbon fibre twill. The suitability of three different types of adhesive for the sheet is analyzed, as well as the effect of adhesive thickness and laminate lay-up angle on the strength of the secondary glue joint, and the simulation is verified by ABAQUS software. The results show that, using SY-23B epoxy structural adhesive, the adhesive layer thickness is 0.2 mm, the lay-up method is [(0/90)]<sub>8</sub>-[(0/90)]<sub>8</sub>, the bonding performance is optimal, the structural shear strength can reach 18.2 MPa, which can meet the small UAV stress box section bonding strength requirements,the secondary bonding formed wing stress box section has the advantages of light weight, low cost.
A folding wing aircraft can autonomously change its configuration in flight to respond to different flying environments. Hinge moment during morphing process is an important basis for driving mechanism design and structural strength check, and its calculation depends on the simulation of the morphing process. Existing studies mostly use the simplified lifting surface method for aerodynamic modeling. In this paper, the CFD-based simulation method is studied, and the results are compared with those by the lifting surface method. First, the unsteady aerodynamic modeling method of the folding wing based on the CFD method is studied, an effective description method is given to define the wall mesh motion caused by wing folding and aileron deflection, and an unfolding–refolding strategy is proposed to improve the quality of the internal mesh in the case of large folding angles. Then, the CFD aerodynamic model is coupled through a developed coupling calculation program with the flexible multibody structure model for the simulation of a flight-morphing process. The comparison with the results of the lifting surface method shows that hinge moments obtained according to the two aerodynamic models are markedly different. Analysis of the difference shows that airfoil thickness considerably affects aerodynamic loading distributions and hinge moments of folding wing aircraft. The lifting surface method ignores airfoil thickness, which will cause large simulation errors in hinge moments.
As the development of science and technology has reached the point where the desire to travel to Mars has become a tangible reality, the physical limits of human movement are also part of the systematic research based on the space environment. The critical issues of radiation, altered gravity, hostile environment, isolation or confinement, and distance from Earth (travel time) are the five major hazards for astronauts during spaceflight. The prepared technology of space medicine is significant for physical health. However, how would the lone space exploration (2.5 to three years) affect the mental conditions of the astronauts? How can the space community keep astronauts safe from psychological obstacles, such as depression, conflict, resentment, bipolar disorder, obsession, and addiction? This paper explores the environmental factors of a healthy lifestyle (well-being) of the spacecraft. It presumes that a successful mission often relies on positive interactions between crew members and between the crew and ground personnel. The paper considers the mental sustainability from stress, emotions, and perceptions to improve human tonicity or vitality and argues a new mental strategy in space exploration policy that the role of an astronautical religion beyond human intelligence and artificial intelligence (AI) could be a psychiatric anchor (in a moral, ethical, and self-sacrificial context) of each astronaut and leadership of the space team as a psychoanalytical countermeasure, along with physical exercise, hobbies, pets, and virtual and augmented reality (VR/AR) entertainment, especially in the case of unexpected crises where science and technology fail its general function.
Sergio Cuevas del Valle, Hodei Urrutxua, Pablo Solano-López
et al.
Deep space missions are recently gaining increasing interest from space agencies and industry, their maximum exponent being the establishment of a permanent station in cis-lunar orbit within this decade. To that end, autonomous rendezvous and docking in multi-body dynamical environments have been defined as crucial technologies to expand and maintain human space activities beyond near Earth orbit. Based on analytical and numerical formulations of the relative dynamics in the Circular Restricted Three Body Problem (CR3BP), a family of optimal, linear and nonlinear, continuous and impulsive, guidance and control techniques are developed for the design of end-to-end rendezvous trajectories between co-orbiting spacecraft in this multi-body dynamical environment. To this end, several modern control techniques are effectively designed and adapted to this problem, with particular emphasis on the design of low cost rendezvous manoeuvres. Finally, the designed hybrid rendezvous strategies, combining both discrete and continuous control techniques, are effectively tested and validated under several start-to-end deep space testbench mission scenarios, where their performance is compared and quantitatively assessed with a set of performance indices.
This paper proposes a method of structural modification for the assignment of natural frequencies and mode shapes based on frequency response functions (FRFs). The method involves the addition of masses or stiffness (supporting stiffness or connection stiffness), the simultaneous addition of masses and stiffness, or the addition of mass-spring substructures to the original structure. Firstly, the proposed technique was formulated as an optimization problem based on the FRFs of the original structure and the masses or stiffness that needed to be added. Next, the required added masses and stiffness were obtained by solving the optimization problem using a genetic algorithm. Finally, numerical verification was performed for the different structural modification schemes. The results show that, compared to only adding either stiffness or masses, adding both simultaneously or adding spring-mass substructures obtained better optimization results. The advantage of this FRFs-based method is that the FRFs can be directly measured by modal testing, without knowledge of analytical or modal models. Furthermore, multiple structural modifications were considered in the assignment of natural frequencies and mode shapes, making the application of this method more applicable to engineering.
R. Sabari VIHAR, J. V. Muruga Lal JEYAN, K. Sai PRIYANKA
Flutter is the phenomenon where the body will experience uncontrolled motions after reaching a certain velocity known as the critical velocity. The focus of this work is on studying the influence of position of camber of an airfoil on its flutter behaviour. Four different NACA five digit airfoils were selected based on the variation in position of camber and were analyzed at different air speeds. These airfoils were studied for their pitch and plunge behaviour which are the base for understanding the flutter characteristics of any body and the flutter characteristics are derived from those results.
The boosting of the fuel efficiency of in-service aircraft is an issue of great commercial and ecological importance. One of the ways to achieve this is by adjusting the flight parameters and flight planning to the particular performance level of every single airplane. Main contributors to the aircraft performance deterioration are the aerodynamic and power plant deterioration. In this paper a mathematical modelling approach for the estimation of the effect of turbofan engine deterioration on passenger aircraft performance is proposed. Based on previous flight models developed by the authors, the present model simulates the deterioration of CFM-56-like turbofans on an Airbus A319-like airplane, and makes possible to compare the performance of airplanes with deteriorated and not deteriorated engines over various flight missions. A representative scenario is explored as an illustration. The model can be further developed to include the aerodynamic deterioration of the aircraft as well as other operational factors.
First published online 29 January 2020
High-speed electric machines are gaining more and more importance in several application fields thanks to various factors. For example, it is often desirable to get rid of gear-boxes between high-speed turbines or compressors and the coupled electric machinery in favour of a direct-drive arrangement for better efficiency, higher reliability and easier maintenance. At the same time, raising the speed of the electric machine is an effective way to reduce its torque, and hence its size and weight, for any given power rating. This especially applies to electric motors and generators to be used in hybrid or electric vehicles and in moreelectric aircrafts, where room and weight restrictions make high power density a crucial design target. The field of high-speed electric machinery is very broad encompassing a large variety of technologies, applications, power ratings and performance requirements. In any case, the design of these machines is particularly delicate because materials and components in them are subject to extraordinary thermal, mechanical and electromagnetic stresses and tend to work close to their physical operating limits. For instance, high rated frequencies cause large magnetic losses in the stator core and eddy-current losses in stator conductors and rotor active parts, resulting in possibly dangerous temperatures; rotor surfaces may overheat also due to air friction losses at high rotational speeds. On the other hand, centrifugal forces induce mechanical stresses in rotating components causing wear, fatigue and possible early failures. Finally, the need to reach very high speeds may cause the rotor to temporarily cross or approach its critical speeds, resulting in possible vibrations and lateral dynamic instability of the whole shaft line. Accurately evaluating all of these aspects is mandatory for a safe design and must require a multi-physics approach due to the close interactions among electromagnetic, thermal, ventilation and mechanical phenomena. The design process is made ever more challenging by the frequent requirement to minimise the machine cost and maximise its power density together with other performance indices, leading to the need for a multi-objective constrained optimisation approach. This implies that hundreds or thousands of designs are to be comparatively explored in search for the optimal solutions and, to make such a wide exploration feasible, computationally-efficient methods need to be used for the analysis of each design. This Special Issue features thirteen peer-reviewed papers which provide some specific technical insights into the general topics and challenges mentioned above regarding the design, analysis and operation of high-speed electric motors and generators for state-ofthe-art and emerging applications. The first paper, ‘Maximisation of Power Density in Permanent Magnet Machines with the Aid of Optimisation Algorithms’, by F. Cupertino et al., clearly addresses the potentials and limits of power density maximisation in high-speed surface permanentmagnet machines for aeronautical use. It emphasises how, as the rated speed grows, the retaining sleeve thickness needed to secure the permanent magnet against centrifugal force grows as well, leading to larger air-gaps and thus posing a limit on the power density increase. An optimisation process, including both electromagnetic 2D finite-element analysis (FEA) simulations and analytical mechanical formulas, is proposed to identify the speed that produces the maximum achievable power density. The power density optimisation of a surface-permanent magnet machine for aeronautical use is also addressed in the second paper, ‘Optimisation Method to Maximise Torque Density of High-Speed Slotless Permanent Magnet Synchronous Machine in Aerospace Applications’, by D. Lee et al. Here the focus is on an outer-rotor machine topology with a slotless stator and a Halbach-array permanent-magnet arrangement. The optimisation approach is different as the speed is treated as a constraint, together with stator copper losses, rotor mechanical stress levels, inner and outer machine radii and core length. The internal machine dimensions, as well as the magnetisation directions of Halbach-array magnetic segments, are taken as design variables to maximise the power density through a 2D FEA-based optimisation. Design optimisation is covered again in the third paper, ‘Magnetic Circuit Designing and Structural Optimisation for a Three Degree-of-freedom Hybrid Magnetic Bearing’, by Z. Xu et al., but this time applied to magnetic bearings as a key component of many high-speed machines. A correct magnetic bearing design, targeting suitable load capacity and stiffness values, is essential to guarantee a satisfactory rotor-dynamics behavior of the high-speed shaft line. The magnetic bearing is analytically modeled through the magnetic equivalent circuit technique so as to speed-up the particle-swarm optimisation process. The optimal design finally selected is then investigated in more detail through 3D FEA simulations. An innovative approach to achieve magnetically-suspended rotors in high-speed machines as an alternative to conventional magnetic bearings is presented in the fourth paper, ‘1 kW/60,000 min−1 Bearingless PM Motor with Combined Winding for Torque and Rotor Suspension’, by D. Dietz et al. The high-speed motor is equipped with a six-phase stator winding. The multiple degrees of freedom offered by multiphase windings are exploited to generate the torque through a conventional field-oriented control and, at the same time, to produce the radial force required for rotor magnetic levitation. The solution is implemented into a prototype and successfully validated through various tests. The multi-disciplinary nature of high-speed motor design is illustrated in the fifth paper, ‘Design of High Speed Interior Permanent Magnet Motor Based on Multi-Physics Fields’, by F. Zhang et al., which presents the design process for a high-speed interior permanent-magnet motor. The need for a multi-physics approach is emphasised, stressing the importance and interdependence of the electromagnetic, structural, rotor-dynamics, heat-transfer and fluid-dynamics analyses which need to be performed in the design of a high-speed machine. An insight into the rotor-dynamics analysis in high-speed machine design is given in the sixth paper, ‘Rotor-Dynamics Modelling and Analysis of High-Speed Permanent Magnet Electrical Machine Rotors’, by Z. Huang and Y. Le. Predicting the natural frequencies associated with the rotor bending modes (especially the first two) is, in fact, essential to ensure that all steady-state operating points are sufficiently far from critical speeds and avoid the occurrence of dangerous vibrations and mechanical failures. The integration of mechanical and electromagnetic calculations in the design of high-speed synchronous reluctance motors is addressed in the seventh paper, ‘Design Methodology for HighSpeed Synchronous Reluctance Machines’, by C. Babetto et al.
Work on ensuring adhesion of chromium coating on parts piston with a rod made of ВТ3-1, ВТ22 titanium alloys was carried out based on the examination of residual stresses. Ensuring the adhesion of coats was conducted in two stages: at the first stage strengthening treatment was used, and at the second stage optimization of grinding conditions by residual stresses was carried out. A method of predicting process-induced residual deformation by equivalent initial stresses is presented. Residual stresses in a surface layer of specimens cut out of the strengthened parts were studied. It was established that compressive residual stresses in the surface layer ensure the coating adhesion in chromium plating of parts made of titanium alloys. It was shown that ensuring adhesion of coatings on parts made of titanium alloys can be obtained both by strengthening treatment and without it, due to the optimization of grinding conditions. The results obtained made it possible to eliminate surface tempering in the process of grinding parts made of titanium alloys, to ensure favorable technological heredity not only for the parts under examination, but for other parts such as pistons, hydraulic cylinders and rods.
The purpose of this paper is to present the aerodynamic and flow characteristics of a slender body with a 30° swept wing configuration undergoing a limit cycle oscillation using a synchronous measurement and control technique of wing rock/particle image velocimetry/dynamic pressure associated with the time history of the wing rock motion. The experimental investigation was concentrated on 3 main areas: motion characteristics, static and dynamic surface pressures and static and dynamic particle image velocimetry. The tests’ results revealed that the lag in asymmetric twin vortices over the forebody switching from the left vortice pattern to the right one exhibits a hysteresis evolvement during the wing rock motion; the asymmetric triple vortices over the forebody interacted with the flowfield over wings appeared to induce the instability and damping moments. The main flow phenomena responsible for wing rock of wing body configuration were completely determined by the forebody vortices. These exhibit apparent dynamic hysteresis in vertical position, which further influences the wing flows, and the dynamic hysteresis of flows yields the damping moments sustaining the oscillations.
Technology, Motor vehicles. Aeronautics. Astronautics
In the article issues of the organization of imitating modeling complexes for training operators of Remotely Operated Underwater Vehicle are considered. It is reported about practical development of sea exercise simulation in Bauman MSTU.