Search Results (2,156)

With the tightening of international environmental requirements for civil aviation and the implementation of initiatives aimed at reducing specific greenhouse gas emissions, the transition to hybrid power plants for regional aircraft is becoming increasingly relevant. This paper proposes an approach to the integrated energy assessment of a parallel hybrid turboprop power plant at the conceptual design stage while taking the aircraft mission profile into account. The considered power plant includes a gas turbine engine, a reversible electric machine located on the same shaft as the reduction gearbox and propeller, an electrical energy storage system, and power electronics. The mission profile is represented as a sequence of segments—takeoff, climb, cruise, descent, and approach/landing. For each segment, energy balances are formulated and allowable operating ranges for the gas turbine and electric subsystems are defined. The key parameter is the hybridization factor, which determines the share of power transmitted to the propeller from the electric machine in different mission segments. The primary integrated performance metric is the energy consumption per ton-kilometer of transported payload. The analysis shows that for ranges up to 500 km, the hybrid configuration reduces specific energy consumption per ton-kilometer by up to 9%. Full article

Stiffened plate structures widely used in military aircraft are frequently subjected to severe shock environments, such as those generated by gunfire or explosive blasts, which can significantly compromise the integrity and reliability of onboard equipment and devices. Accurate characterization and prediction of the shock response, especially the damping behavior of such structures, remains a critical yet challenging problem in aeronautical engineering. This study presents an integrated experimental–numerical framework for analyzing the shock response and damping characteristics of representative stiffened plates under shock wave excitation. Controlled shock loading is applied using a shock tube, with real-time acceleration responses measured at multiple locations on both plain and rib-reinforced plates. A high-fidelity finite element model is developed, and three commonly used damping models—Rayleigh Damping, wave attenuation Model, and Maximum Loss Factor Model—are systematically evaluated. Damping parameters are identified through a Particle Swarm Optimization (PSO) algorithm, using the shock response spectrum (SRS) as the performance metric. Experimental results reveal that the incorporation of reinforcing ribs can reduce peak acceleration responses and significantly enhance the damping performance, particularly in the mid-to-high frequency range. The identified damping parameters further show that the maximum loss factor model provides superior agreement with experimental SRS data compared to traditional approaches. The proposed methodology offers a robust method for modeling damping behavior in stiffened plates, providing practical insights for the design of aircraft structures exposed to shock environments. Full article

Composite hat-stiffened panels are widely used in civil aircraft structural design as typical closed-section stiffened components with high load-carrying efficiency. To accurately predict the post-buckling bearing capacity and optimize the tapered termination design of such panels, this paper investigates the failure process of composite hat-stiffened panels with tapered ends through physical modeling and numerical analysis. A nonlinear failure analysis model is established by introducing the failure mechanisms of adhesive interfaces and composite laminates. The modeling method is verified against experimental results, showing discrepancies of 2.7% for buckling load and 3.5% for post-buckling failure load, respectively. Based on the validated numerical approach, parametric studies are carried out to analyze the effects of termination taper parameters on buckling and post-buckling mechanical behaviors. The results indicate that the termination taper design effectively adjusts the stiffness matching between stiffeners and skin and relieves local stress concentration. The optimal taper angle of 120° is recommended, where the failure load increases by 22% to 141.8 kN compared to the baseline configuration, significantly improving its post-buckling load-carrying capacity. The findings of this study can provide technical references for the design of stiffened composite panels with tapered stringer terminations in aerospace engineering. Full article

This paper presents the Goddard RISC-V (GRV) a compact, portable, and highly customizable fault-tolerant 32-bit RISC-V processor, specifically designed for embedded space applications. The design integrates advanced fault-tolerance mechanisms to mitigate arbitrary Single Event Transient (SET) and Single Event Upset (SEU) errors while ensuring data integrity. Importantly, fault tolerance is achieved entirely at the design level, eliminating the need for SEU-hardened semiconductor processes, custom cell libraries, or specialized back-end tools. The implementation prioritizes portability and resource efficiency, enabling compatibility with various FPGA and ASIC technologies. This initiative aims to provide NASA with a suite of portable, modular, and scalable alternatives to proprietary solutions. These solutions are designed for broad adaptability across multiple platforms, such as compact scientific instruments, miniaturized deep-space technologies, CubeSats, control and automation systems, and other applications constrained by low-resource processing environments. Full article

Aircraft design is regulated by federal law and must comply with complex regulatory documentation. The complexity of the certification process has resulted in a growing interest in digital transformation, for which models are often used to provide explicit structure. Ontological modeling is one of the most promising approaches for the digital transformation of regulatory documentation. This paper presents a novel approach to ontology development that applies ontology design patterns to construct a knowledge representation of regulatory documentation, with a focus on guidance material. The approach includes five main processes: (i) the selection of a regulatory document; (ii) the use of a natural language processing tool; (iii) a contextual analysis; (iv) the identification of patterns in the natural language; and (v) the development and implementation of ontology design patterns. The modeling approach is demonstrated using the ARP4754B: Guidelines for Development of Civil Aircraft and Systems guidance material document and is validated with a use case AC21.101-1B—Establishing the Certification Basis of Changed Aeronautical Products guidance material document. The modeling approach is then verified against an established set of regulatory documentation modeling requirements. The systematic ontological modeling approach presented in this paper enables digital transformation of regulatory documentation, a necessary step for a more efficient and effective certification process. Full article

Hypersonic aircraft represent a cutting-edge technology in aerospace engineering. Coupled heat transfer is a critical physical phenomenon in such aircraft. However, existing studies face challenges in predicting aerothermal behavior. Based on a specific geometric configuration, an axisymmetric model and the ideal gas assumption, this study establishes a numerical simulation model for coupled heat transfer in hypersonic wide-speed-range cruise aircraft. Through numerical simulations, the heat transfer characteristics of the aircraft under Mach numbers of 6, 7, 8 and 9 are analyzed, revealing the evolution of the temperatures at characteristic points and surfaces as the Mach number increases. Additionally, this study analyzes the heat transfer characteristics of metallic materials such as Inconel 718, 17-4PH, 93WNiFe and TA19, revealing differences in thermal protection performance among aircraft made of different materials under hypersonic conditions. Correlation functions relating nose temperature to time and surface temperatures to Mach number are fitted. The results indicate that as the Mach number increases, the aerodynamic heating temperature of the aircraft rises, and the aerodynamic heating effect at the stagnation point becomes more pronounced. Among the materials studied, 17-4PH exhibits the best overall thermal protection performance. This study provides methodological support for thermal prediction of hypersonic aircraft. Full article

In high-altitude interception, low atmospheric density limits the effectiveness of aerodynamic control, making thruster-based attitude control essential. In systems using single-use impulse-type lateral thrusters, each actuator can be fired only once, generates a fixed thrust magnitude, and is subject to a limit on the number of simultaneously active thrusters. Therefore, selecting an appropriate set of thrusters to track a desired control moment can be formulated as a cardinality-constrained combinatorial optimization problem. This paper proposes a depth-first search (DFS)-based branch-and-bound algorithm for sparse thruster selection. The objective is to minimize the tracking error between the generated and desired control moments while penalizing the number of active thrusters. To improve computational efficiency, thrusters are ordered by moment magnitude, and a problem-specific lower bound is derived from the residual moment and an upper bound on the achievable contribution of the remaining thrusters. This bound enables effective pruning of unpromising branches. The search space is further reduced by reformulating the problem using symmetric thruster pairs that generate opposing moments. Numerical results show that the proposed method achieves accurate moment tracking while significantly reducing computation time compared with the exact mixed-integer quadratic programming (MIQP) benchmark. Mixed-integer linear programming (MILP) is also included as an additional mixed-integer linear surrogate comparison. Full article

Multirotor unmanned aerial vehicles (UAVs) suffer from significant control performance degradation during aggressive maneuvers, primarily due to aerodynamic nonlinearities and coupling effects. Conventional fixed-gain PID controllers struggle to simultaneously satisfy performance and robustness requirements across the wide flight envelope. To address this challenge, this paper presents a novel hierarchical safety-constrained reinforcement learning (RL) framework for adaptive PID tuning: the inner loop employs fixed gains, the outer loop leverages proximal policy optimization (PPO) for online adaptive gain scheduling, and linear matrix inequality (LMI) constraints delineate robust parameter boundaries for the adaptive exploration. Importantly, the LMI feasibility strictly guarantees theoretical stability for the fixed inner-loop parameters at the linearization vertices within a linear parameter-varying (LPV) framework. Concurrently, the online outer-loop RL stage is protected by safety boundaries and a Lagrangian penalty mechanism acting as an effective engineering safeguard rather than a rigorous global stability proof. Comprehensive high-fidelity simulation benchmarks demonstrate that, compared with a baseline fixed-gain PID controller, the proposed framework reduces overshoot by 18.5% in high-speed step responses and improves the overall mean RMSE by 15.0% across 100 randomized mixed-trajectory trials (with improvements of up to 40.9% in highly dynamic scenarios), yielding consistent gains in trajectory tracking accuracy and disturbance rejection despite uncertain model variations. By seamlessly blending control-theoretic hard constraints with RL-based soft-parameter tuning, the proposed architecture offers a safe and highly adaptive solution for large-envelope flight control, demonstrating strong engineering relevance. Full article

Multi-body separation of flight vehicles is challenged by potential collisions that critically affect dynamic stability. This study develops a numerical method for simulating coupled aerodynamics, kinematics, and collision dynamics. Building upon a conventional computational fluid dynamics/rigid body dynamics (CFD/RBD) framework, the proposed approach integrates a collision dynamics model based on impulse–momentum theory and Coulomb’s friction law, together with a parallelized collision detection algorithm employing edge-face bounding boxes. A loosely coupled staggered solution scheme is established to effectively overcome the limitation of overset mesh in handling colliding bodies. The method is validated through store separation and rigid sphere collision, confirming its capability in resolving aerodynamic/kinematic coupling and normal/tangential collision responses. Application to a cluster munition separation case reveals shell behaviors at distinct initial velocities and identifies a critical safety boundary when the initial shell separation velocity reaches 3.25 times the projectile velocity, defining kinematic and aerodynamic threshold criteria for collision-free separation. Quantitative error analysis shows that the velocity and angular velocity errors from the aerodynamic approximation remain below 2.5% of the collision-induced increments, confirming the method’s engineering accuracy. Flowfield analysis shows that lower velocities result in severe shock interference and collision, whereas higher velocities enable rapid clearance, aerodynamic recovery, and clean separation. Full article

The Rocket-Based Combined Cycle (RBCC) engine is a promising propulsion system for hypersonic and space launch applications due to its capability to operate efficiently over a broad range of flight conditions. This study investigates the influence of total temperature and total pressure on flow patterns in the rocket-ejector mode of a RBCC engine using two-dimensional numerical simulations—a simplification that facilitates efficient parametric analysis while inherently omitting three-dimensional effects. The transition between stable and wavy flow patterns under the Diffusion and Afterburning (DAB) combustion mode is analyzed. Higher total temperatures enhance mixing efficiency but can induce wavy flow patterns, leading to potential instability. Conversely, increased total pressures promote stability through Fabri-choking mechanisms while reducing mixing efficiency by limiting entrainment capacity. A significant hysteresis effect is observed, where transition thresholds for stable and wavy states vary based on operational history. Key mechanisms contributing to this effect are discussed in depth, including momentum flux dynamics, Fabri-choking behavior, shock wave reformation, and mass and heat exchange processes. These findings provide critical insights for optimizing RBCC engine performance by balancing flow stability and mixing efficiency under varying conditions. This study’s insights into flow pattern dynamics, particularly the hysteresis effect, are crucial for developing robust control strategies and optimizing RBCC engine designs for hypersonic and space launch applications. Full article

We proposed a bilateral parallel offset jet model that enables jet vectoring control without the need for an active high-pressure secondary flow. Flow characteristics, including deflection force, wall pressure distribution, and flow structures, were investigated. The evolutions of key flow structures during jet deflection were investigated, including the passive secondary flow, the shear layer, the boundary layer, and the separation bubble. By analyzing the formation, dissipation, and interactions of the key flow structures, as well as their relationship with pressure characteristics, the mechanism of the jet deflection control was further deduced. The fundamental driving force of the jet deflection stems from the unbalanced pressure difference on either side of the jet, and the valve can control the flow rate of passive secondary flow, thereby altering the near-wall pressure on its side and further generating a pressure that propels the jet to deflect. For walls of different lengths, at a moderate wall length, where L* = 1.5, with the valve controlling the passive secondary flow, a maximum jet vectoring angle of 6.4° can be continuously achieved at a low Reynolds number. Within the range where 20% < δ_v < 100%, the nonlinear error of jet vectoring control is 5.7%. At a short wall length, where L* = 0.5, the driving force generated by the valve to deflect the jet is insufficient, and the maximum vector angle is 0.3°. For longer walls, the impact of the jet against the trailing edge of the wall obstructs jet deflection; therefore, extending the wall is not conducive to jet vectoring control. Featuring a non-expanding wall structure, the bilateral parallel offset jet model provides a new thrust vectoring control scheme characterized by a compact afterbody, no need for a high-pressure secondary air source, and a simple structure. Full article

This paper introduces an adaptive prescribed performance control (PPC) methodology designed to achieve appointed-time stabilization for morphing aircraft. The proposed approach ensures accurate attitude tracking despite challenges posed by time-varying dynamic constraints, structural deformation perturbations, abrupt aerodynamic disturbances, and rapid variations in attitude commands. Specifically, a novel appointed-time control law is developed using the back-stepping framework to enable precise adjustment of the stabilization time. Then, an adaptive performance boundary adjustment function is introduced. This function not only constrains the system state error but also adapts based on the distance between the state error and the real-time boundary, as well as command variations. This mitigates the fragility issues associated with traditional PPC methods. To further address the ‘differential explosion’ problem, an adaptive appointed-time filter is constructed in which the filter error can be stabilized for an appointed time. The unknown and total perturbations are estimated via adaptive neural networks. The designed controller is shown to guarantee the appointed time stability for all closed-loop signals and ensure that the system state error stays inside the prescribed bounds based on the stability analysis. Lastly, numerical simulations are performed to verify the advantages and effectiveness of the proposed method. Full article

This paper proposes a computationally efficient algorithm for nonlinear optimal guidance with a predefined final flight path angle. Although numerous impact angle guidance methods based on optimal control theory exist, a lack of efficient calculation procedures remains for the exact nonlinear engagement model, leaving practical hardware implementation challenges for the end-user. A fixed-structure algorithm with deterministic computational burden is developed for real-time onboard integration. The performance and optimality of the algorithm are verified through a comparative study with established guidance laws. Unlike methods relying on line-of-sight rate or time-to-go estimations, the proposed approach uses a closed-feedback form based on standard navigation data. A closed-form solution is derived for the climb phase to the cruise altitude. Practical feasibility is demonstrated on a microcontroller-based onboard computer, with execution times analyzed for flight software compatibility. The robustness of the proposed framework is validated via high-fidelity hardware-in-the-loop tests for two distinct scenarios: a multi-phase cruise mission and a short-range ballistic trajectory subject to propulsion uncertainties. Results confirm high precision and accurate impact angles across vastly different flight regimes, ranging from low-altitude cruise to high-dynamic reentry. Full article

This paper deals with the investigation of the best topology of a five-phase fault-tolerant spoke-type permanent magnet (PM) motor for the propulsion of a multirotor aerial vehicle. This study is carried out through four stages. First, an assessment of the PM configuration effect on motor performance, considering three positions, namely surface PM, spoke-type PM, and V-shape PM. Second, an evaluation of the optimisation formulation problem on motor performance, where three formulations, respectively, involving either electric motor (EM) efficiency, EM efficiency and torque, or EM efficiency and active weight are considered for this purpose. Third, the stator winding configuration effect on performance in healthy and faulty operation mode (OM), e.g., open-circuit fault (OC) and inter-turn short-circuit (ITSC) fault, is also assessed. This evaluation is performed considering two winding configurations, namely fractional slot concentrated winding (FSCW) with single-layer (SL) or dual-layer (DL) winding. Fourth, a modified rotor geometry is proposed, based on the airgap length variation, in order to increase the airgap flux density amplitude and thus improve the motor torque and power densities. A comparative study, in this case, is performed with a classical rotor geometry in order to assess their influence on motor performance in healthy and faulty operation mode (OM). In addition, this paper presents a quantitative comparison of the proposed five-phase motor and a three-phase spoke-type PM motor, where the results, in healthy and faulty OM, show the interest of the proposed multiphase motor. Full article

Forced resonance induced by rotor–stator interaction (RSI) is a primary driver of high-cycle fatigue (HCF) failure in aero-engine blisks. To overcome the inability of traditional non-contact excitation methods to replicate authentic three-dimensional aerodynamic forces and the predictive biases of pure numerical approaches regarding complex flow excitation energy, this study investigates the forced resonance characteristics of a rotating blisk using a novel aerodynamic excitation system through integrated numerical and experimental approaches. First, a one-way fluid–structure interaction (FSI) framework, coupling the Nonlinear Harmonic (NLH) method with Finite Element Analysis (FEA), was established to efficiently reconstruct the unsteady aerodynamic loads on blade surfaces. The analysis reveals an excitation mechanism dominated by the upstream propagation of the downstream potential field, based on which the numerical resonance response was predicted. In addition, investigating rotor–stator axial clearance as a key variable indicates that there is a strictly monotonically decreasing dependence of the aerodynamic excitation magnitude on the rotor–stator axial clearance. However, the spatial patterns of the primary first-order harmonic excitation remain relatively insensitive to changes in the rotor–stator axial clearance. Finally, by leveraging these excitation characteristics, broadband aero-resonance of the first three modes was successfully induced within the 2600 Hz frequency range under experimental conditions. This validates both the effectiveness of the experimental apparatus and the fidelity of the numerical model. This research not only clarifies the excitation mechanism under vortex generator-induced RSI but also provides a novel testing platform and theoretical framework for rotating modal analysis in advanced propulsion systems. Full article