Abstract: Drones have long been explored for supply. While several systems offering small pay-loads in drone delivery have seen operational use, large-scale supply drones have yet to be adopted. A range of setbacks cause this, including technological and operational challenges that hinder their adoption. Here, these challenges are evaluated from a conceptual modelling perspective to forecast their applicability once these barriers are overcome. The study uses technology trend modelling and bibliometric activity map-ping methodologies to predict the applicability of specific technologies that are cur-rently identified as operational challenges. Specifically for supply drones, trends in technological improvements of battery technology and aircraft control are modelled to project effects and focus on landing zone autonomy and powertrain. The prediction also focuses on the current state of hybrid power and higher levels of automation required for landing zone operations. These models are validated through several published case studies of small delivery drones and then applied to assess the feasibility and con-straints of larger supply drones. A case study, conceptual design of a supply drone large enough to move a shipping container, is presented to illustrate the critical technologies required to transition large supply drones from concept to operational reality. Key technologies required for large-scale supply drones have yet to build up a critical mass of research activity, particularly on landing zone autonomy and powertrain. Moreover, additional constraints beyond technological and operational challenges could include limitations in autonomy, certification hurdles, regulatory complexity, and the need for greater social trust and acceptance.

Abstract: The need for simpler, yet accurate and physically sound, methods to predict the lift and pressure distributions over asymmetric delta wings, particularly at high angles of attack with attached shock wave, motivates the development of an alternative approach presented in this paper. By employing a geometric transformation and postulating a functional similarity between linear and nonlinear solutions, a straightforward algebraic technique for pressure estimation is developed. This approach bridges the solution in the central nonuniform flow region to the exact solutions in the uniform flow regions with attached shock waves near the leading edges, in a manner analogous to methods used for supersonic starting flow at high incidence. The method is shown to reproduce established results for both symmetric and yawed delta wings within a limited error. It yields a compact, explicit expression for the normal force coefficient, formulated as a weighted average of the pressure coefficients from the two uniform flow regions. A pathway for extending the approach to the upper surface, where the uniform flow is governed by swept Prandtl-Meyer relations is also outlined. Although classical analytical approaches for delta wings were established decades ago, the proposed method provides a tractable alternative tool for modern fast engineering analysis.

Abstract: Very Low Earth Orbit (VLEO) satellites, operating at altitudes below 450km, provide tremendous potential in the domain of remote sensing. Their proximity to Earth of-fers high resolution, low latency, and rapid revisit rates, allowing continuous moni-toring of dynamic systems and real-time delivery of vertically integrated earth ob-servation products. Nonetheless, the application of VLEO is not yet fully realized due to numerous complexities associated with VLEO satellite development, considering atmospheric drag, short satellite lifetimes, and social, political and legal regulatory fragmentation. This paper reviews the recent technological developments supporting sustainable VLEO operations with regards to aerodynamic satellite design, atomic oxygen barriers, and atmospheric-breathing electric propulsion (ABEP). Furthermore, the paper pro-vides an overview of the identification of regulatory and economic barriers that extort additional costs for VLEO ranging from frequency band allocation and space traffic management to life-cycle cost and uncertain commercial demand opportunities. Nevertheless, the commercial potential of VLEO operations is widely acknowledged, and estimated to lead to an economic turnover in the order of 1.5 B$ by 2030. Learning from the literature and prominent past experiences such as the DISCOVERER and the CORONA program, the study identifies key gaps and proposes a roadmap to sustainable VLEO development. The proposed framework emphasizes modular and serviceable satellite platforms, hy-brid propulsion systems, and globally harmonized governance in space. Ultimately, public-private partnerships and synergies across sectors will determine whether VLEO systems become part of the broader space infrastructure unlocking new capabilities for near-Earth services, environmental monitoring, and commercial innovation at the edge of space.

Abstract: This study introduces an all-fiber optic sensing network based on fiber Bragg grating (FBG) technology for structural health monitoring (SHM) of launch vehicle payload fairings un-der extreme thermo-mechanical conditions. A wavelength–space dual-multiplexing ar-chitecture enables full-field strain and temperature monitoring with minimal sensor de-ployment. Structural deformations are reconstructed from local measurements using the inverse finite element method (iFEM), achieving sub-millimeter accuracy. High-temperature experiments verified that FBG sensors maintain a strain accuracy of 0.8 με at 500 °C, significantly outperforming conventional sensors. Under 15 MPa mechanical loading and 420 °C thermal shock, the fairing structure exhibited no damage propagation. The sensing system captured real-time strain distributions and deformation profiles, con-firming its suitability for aerospace SHM. The combined use of iFEM and FBG enables high-fidelity, large-scale deformation reconstruction, offering a reliable solution for reusa-ble aerospace structures operating in harsh environments.

Abstract: Unmanned Aerial Vehicles (UAVs) are increasingly deployed across diverse domains and many applications demand a high degree of automation, supported by reliable Conflict Detection and Resolution (CD&R) and Collision Avoidance (CA) systems. At the same time, public mistrust, safety and privacy concerns, the presence of uncooperative airspace users, and rising traffic density are driving a shift toward decentralized concepts such as free flight, in which each actor is responsible for its own safe trajectory. This survey reviews CD&R and CA methods with a particular focus on decentralized automation and encounters with noncooperative intruders. It analyzes classical rule-based approaches and their limitations, then examines Machine Learning (ML)–based techniques that aim to improve adaptability in complex environments. Building on recent regulatory discussions, it further considers how requirements for trust, transparency, explainability, and interpretability evolve with the degree of human oversight and autonomy, addressing gaps left by prior surveys.

Abstract:

Precise orbit determination for multi-spacecraft deep-space missions faces challenges including long communication delays, sparse tracking, dynamic model uncertainties, and inefficient data fusion. Presenting a hybrid estimation architecture, this study integrates onboard autonomous navigation with ground-based batch processing of delayed measurements. The framework makes three key contributions: (1) a delay-aware fusion paradigm that dynamically weights space- and ground-based observations according to real-time Earth–Mars latency (4–22 min); (2) a model-informed online calibration framework that jointly estimates and compensates dominant dynamic error sources, reducing model uncertainty by 60%; (3) a lightweight hierarchical architecture that balances accuracy and efficiency for resource-constrained “one-master-multiple-slave” formations. Validated through Tianwen-1 mission-data replay and simulated Mars sample-return scenarios, the method achieves absolute and relative orbit determination accuracies of 14.2 cm and 9.8 cm, respectively—an improvement of >50% over traditional centralized filters and a 30% enhancement over existing federated approaches. It maintains 20.3 cm accuracy during 10-minute ground-link outages and shows robustness to initial errors >1000 m and significant model uncertainties. This study presents a robust framework applicable to future multi-agent deep-space missions such as Mars sample return, asteroid reconnaissance, and cislunar navigation constellations.

Abstract: We study minimum-time heliocentric transfers for a spacecraft propelled by an electric thruster that draws constant electrical power P while continuously varying its exhaust speed (variable Isp). The vehicle is assumed to depart from and arrive on circular heliocentric orbits (i.e., initial and final velocities match the local circular velocity at the respective radii). First, we derive an analytic solution of the one-dimensional, gravity-free brachistochrone and discuss how a finite exhaust-speed ceiling modifies the solution, producing a boost–coast–brake structure. Next, we formulate the full planar Sun-field optimal-control problem, derive two closed-form first integrals, and show that the indirect formulation reduces to a seven-dimensional boundary-value problem. Finally, we present a practical numerical continuation strategy that obtains a coarse feasible endpoint via global optimization and then refines it by homotopy and Powell’s local solver. Numerical examples for a 1GW engine with an initial/dry mass of 3000 t→1000 t demonstrate Earth–Jupiter-class transfers in roughly 200–220 days that commonly exploit a solar Oberth pass. Reproducible code and data are available at the project repository.

Abstract: This paper presents a resilient, multi-layer architecture designed to ensure reliable autonomous operation of single and multiple quadcopters. The architecture leverages the resilient spacecraft executive to hierarchically organize trajectory-planning and flight-control functions, and integrates Simplex architectures at each level to provide safety assurance. A compound subsystem expands robustness by employing multiple candidate algorithms for planning and control, while a supervisory program adapts Simplex behavior based on system states and environmental conditions to enable high-level mission management. The architecture is evaluated in simulations involving environmental uncertainties, including varying wind and obstacles, within a bridge-inspection mission using both single- and multi-quadcopter configurations. Results show that the system maintains safe and effective operation across a wide range of conditions, demonstrating scalability for cooperative multi-agent tasks.

Abstract: Ti-6Al-4V(Ti64), widely used in aerospace structures for its high specific strength and corrosion resistance, is increasingly produced by additive manufacturing (AM) to enhance material efficiency and design flexibility. However, its fatigue performance remains highly variable due to process-induced microstructural heterogeneities and inherent defects. Since aerospace components are designed under damage-tolerant principles, understanding fatigue crack growth (FCG) behavior in AM Ti64 is essential for reliable life prediction. This short review critically examines FCG in Ti64, focusing on the influence of build orientation, processing routes, heat treatment, mean stress, defects, and environmental conditions. These factors, through their effect on the microstructure, govern crack propagation. Achieving consistent and predictable FCG behavior requires standardized test reporting, high-resolution microstructural and defect characterization, and data-driven approaches, that link processing, microstructure, and mechanical response. To complement this mechanistic perspective, a meta-analysis of 67 studies was conducted to assess how FCG research in AM Ti64 is reported. The results showed that only 66 percent of studies included details on manufacturing processes and specimen preparation, and just 68 percent documented feedstock characteristics and material properties, whereas 99 percent reported testing conditions. These gaps highlight the need for more consistent and harmonized reporting. To address this, a reporting benchmark grounded in established testing standards and domain expertise is proposed. Such standardization will enhance reproducibility, enable meaningful data comparisons, and advance data-driven FCG research in AM.

Abstract: The Wind Wall is an innovative mechanical system system comprising multiple Vertical Axis Wind Turbines (VAWTs) designed to efficiently harness wind energy and convert it into electrical power. This study investigates two critical aspects of optimizing the Wind Wall’s performance which uses symmetrical blade profiles: the ideal spacing between the turbines and the optimal helix angle of the turbine blades. The VAWTs in this design utilize the Savonius-type drag-based mechanism, with symmetrical Ugrinsky-profile blades that incorporate a helical twist. The helical twist improves torque uniformity and reduces pulsation in torque, enhancing overall efficiency, but excessive angles can lead to turbulence and reduce the performance. Using CFD simulations, this paper explores the relationship between helix angles, torque generation, and the Coefficient of Moment (Cm) at a constant wind speed. Additionally, the effect of spacing between turbines on effective velocity (Ve) and torque is analyzed. A simplified correlation between Ve, turbine diameter, and spacing is proposed, providing a practical method for designing a Wind Wall with ease. This research identifies the optimal helix angle (20–30°) and spacing parameters, balancing performance, ease of manufacturing for a sustainable energy solution.

Abstract: Due to emerging strategic demands, this article presents a comprehensive conceptual design investigation into enhancing the MQ-9A Reaper Uncrewed Aerial Vehicle (UAV). Motivated by the need for persistent long-range strike and surveillance capabilities, the research study proposes three primary modifications to create an aircraft titled the MQ-9X Raven. First, we replace the existing turboprop engine with the widely used Williams FJ44-4A turbofan for fuel consumption and excess power at 50,000 feet, with a range of approximately 8000 nm. Second, we update the wing design with a 79 ft wing for a greater aspect ratio and a new LRN1015 airfoil to enable high-altitude, long-endurance standoff of around 24 hours. Third and finally, we integrate Joint Strike Missiles (JSM) for enhanced lethality. The project follows a rigorous methodology beginning with a redefinition of mission requirements, aerodynamic, thrust, and stability analysis, and then verification with flight simulation, computational fluid dynamics, and wind tunnel experiments. Our analysis shows the MQ-9X Raven is highly suitable for the task of pervasive high-altitude standoff maritime strike.

Abstract: Unmanned airships are highly sensitive to parametric uncertainty, persistent wind disturbances, and sensor noise, all of which compromise reliable path following. Classical control schemes often suffer from chattering and fail to handle index discontinuities on closed-loop paths due to the lack of mechanisms, and cannot simultaneously provide formal guarantees on state constraint satisfaction. We address these challenges by developing a unified, constraint-aware guidance and control framework for path following in uncertain environments. The architecture integrates an extended state observer (ESO) to estimate and compensate lumped disturbances, a barrier Lyapunov function (BLF) to enforce state constraints on tracking errors, and a Super-Twisting Terminal Sliding Mode (ST-TSMC) control law to achieve finite-time convergence with continuous, low-chatter control inputs. A constructive Lyapunov-based synthesis is presented to derive the control law and to prove that all tracking errors remain within prescribed error bounds. At the guidance level, a nonlinear curvature-aware line-of-sight (CALOS) strategy with an index-increment mechanism mitigates jump phenomena at loop-closure and segment-transition points on closed yet discontinuous paths. The overall framework is evaluated against representative baseline methods under combined wind and parametric perturbations. Numerical results indicate improved path-following accuracy, smoother control signals, and strict enforcement of state constraints, yielding a disturbance-resilient path-following solution for the cruise of an unmanned airship.

Abstract:

Flow quality at the engine face, especially total pressure recovery and swirl, is central to the performance and stability of external compression supersonic inlets. The steady-state RANS based numerical computations are performed to quantify bleed/swirl trade-offs in a single-ramp intake. The CFD simulations are done first without a bleed system over M_∞ = 1.4-1.9 to locate the practical onset of a bleed requirement. The deterioration in pressure recovery and swirl beyond M_∞ ≈ 1.6, consistent with a pre-shock strength near the turbulent separation threshold, motivates the use of a bleed system. The comparisons with and without the bleed system are done next at M_∞ = 1.6, 1.8, and 1.9 across the operation map parameterized by the flow ratio. The CFD simulations are performed by using ANSYS Fluent, with pressure-based coupled solver with realizable k-ε turbulence model and enhanced wall treatment. The results provide engine-face distortion metrics using standardized ring to sector swirl ratio alongside pressure recovery. The results show that bleed removes low-momentum near-wall fluid and stabilizes the terminal-shock interaction, raising pressure recovery and lowering peak swirl and swirl intensity across the map, while extending the stable operating range to lower flow ratio at fixed M_∞. The analysis delivers a design-oriented linkage between shock/boundary-layer interaction control and swirl: when bleed is applied at and above M_∞ = 1.6, the separation footprints shrink and the organized swirl sectors weaken, yielding improved operability with modest bleed fractions.

Abstract: Urban Air Mobility (UAM) promises to reduce ground-traffic and journey times by using electric vertical take-off and landing (eVTOL) aircraft for short, low-altitude flights, especially in urban environments. However, low-flying aircraft are at particularly high risk of collisions with wildlife, such as bird strikes. This study builds on previous research into UAM collision avoidance systems (UAM-CAS) by implementing one such system into the BlueSky open-source air traffic simulator and evaluating its efficacy in reducing bird strikes. Several modifications were made to the original UAM-CAS framework to improve performance. Realistic UAM flight plans were developed and combined with real-world bird movement datasets from all seasons, recorded by an avian radar at Leeuwarden Air Base. Fast-time simulations were conducted in the BlueSky Open Air Traffic Simulator using the UAM flight plan, the bird datasets, and the UAM-CAS algorithm. Results demonstrated that the UAM-CAS reduced bird strikes by 62%, with an average delay per flight of 15s. However, a small number of flights faced substantially longer delays, indicating some operational impacts. Based on the findings, specific avenues for future research to improve UAM-CAS performance are suggested.

Abstract: High-speed low-pressure turbines in geared turbofans operate at transonic exit Mach numbers and low Reynolds numbers. Engine-relevant data remain scarce. The SPLEEN C1 linear cascade is investigated at Mout=0.70--0.95 and Reout=65,000--120,000 under steady inlet flow. Experiments are combined with 2D RANS and MISES, including transition modelling and inlet-turbulence decay calibrated to measurements. Results are consistent with conventional LPT behaviour: losses decrease with increasing Mach and Reynolds numbers, except when shocks interact with the blade boundary layer (M≈0.95). Profile loss drops by 23% from M=0.70 to 0.95 at Re=70,000, and by 19% at M=0.80 when open separation is suppressed. Secondary loss decreases by up to 25% at Re=70,000 and shows weak sensitivity to Reynolds number. A coupled loss model predicts profile loss with RMSE=4.7%. Secondary-loss modelling reproduces global trends: separating endwall dissipation from mixing keeps errors within ±10% for most cases, but accuracy degrades near the shock–boundary layer interaction case and at the highest Reynolds number. Mixing dominates endwall loss (∼75%), with the passage vortex contributing ∼50% (±10%) of the mixing component. This article is a revised and expanded version of “An Experimental Test Case for Transonic Low-Pressure Turbines—Part 2: Cascade Aerodynamics at On- and Off-Design Reynolds and Mach Numbers” presented at ASME Turbo Expo 2022, Rotterdam, June 13–17, 2022. All data and documentation are openly available at https://doi.org/10.5281/zenodo.7264761.

Abstract: This theoretical research paper explores a hypothetical advanced drone swarm system comprising 50 AI-automated, self-driven drones, each equipped with face detection, self-target locking, and a destructive payload designed to release energy comparable to a high energy weapon, deployed from a larger aerial platform. Framed strictly for academic inquiry to avoid any harm, the study delves into the scientific and engineering feasibility of such a system. It examines the intricate mechanisms of swarm intelligence and collective autonomy, including advanced coordination algorithms and resilient communication protocols. The report further investigates AI-driven autonomous navigation, focusing on multi-sensor fusion, real-time obstacle avoidance, and precision targeting with integrated face detection. A significant portion addresses the theoretical basis and immense challenges of a high energy payload, contrasting it with more feasible directed energy weapon concepts and their power and thermal management requirements. The logistical aspects of mothership deployment and aerial integration are also explored. Finally, the paper critically analyzes the profound ethical, legal, and societal implications of such Lethal Autonomous Weapon Systems (LAWS), particularly concerning international humanitarian law, the accountability gap, the AI arms race, and the imperative of meaningful human control, highlighting that while many components are subjects of active research, the high-energy payload remains largely speculative and faces fundamental barriers.

Abstract: The European Union Aviation Safety Agency (EASA) is developing guidelines to certify AI-based systems in aviation with learning assurance as a key framework. Central to the learning assurance are the definitions of a Concept of Operations, an Operational Domain, and an AI/ML constituent Operational Design Domain (ODD). However, since no further guidance for these concepts is provided to developers, this work introduces a methodology for their definition. Concerning the concepts of the Operational Domain of the overall system and the AI/ML constituent ODD, a tabular definition language for both is introduced. Furthermore, processes are introduced to define the different necessary artifacts. For the specification process of the AI/ML constituent ODD, different preexisting steps were identified and combined, such as the identification of domain-specific concepts for the AI/ML constituent. To validate the methodology, it was applied to the pyCASX system that utilizes neural network-based compression. For the use case, the methodology proved it was able to produce an AI/ML constituent ODD of finer detail compared to other ODDs defined for the same airborne collision avoidance use case. Thus, the proposed novel framework is an important step toward a holistic framework following EASA’s guidelines.

Abstract: Unmanned aerial vehicles have been around for decades in the aerospace community, looking into the numerous technological and sophisticated solutions for transport alternatives, opening up new frontiers for aerial supremacy, accounting for the exponentially increasing population density. Now, UAVs accountable for their broad variation in their sizes from being minuscule up to a humungous weaponized system, primarily operate on electric systems to achieve better performance and effective payload allowances. With electricity dominating the technological race, improvising the same for sustainability requirements is also a budding area of scrutiny and research. That being well noted, solar power is another dimension of exploiting the concept of renewability and sustainability, owing to its adaptability. Hence, this work is a comprehensive, detailed review of the research that had been undertaken so far, in integrating solar power sources to unmanned aerial vehicles.

Abstract: This study presents numerical simulations of turbulent flow over a thick airfoil, modeled here as a semicircular cylinder, incorporating aerodynamic flow control (AFC) based on trapped vortex cells. Building upon previous work that focused on viscous effects, we now examine the influence of compressibility at various Mach numbers (M = 0.1, 0.2, and 0.3), corresponding to a diameterbased Reynolds number of 130, 000. The simulations employ a conventional RANS methodology, coupled with the Spalart-Allmaras and realizable k-ϵ turbulence models. To reinforce the validity of the results, cross-platform validation is performed using multiple numerical solvers, including pressure-based, density-based, and hybrid approaches (combining PISO/SIMPLE algorithms with the Kurganov-Noelle-Petrova scheme). Under the investigated conditions, the flow over the AFCintegrated configuration remains fully unseparated and exhibits outstanding lift performance. At Mach 0.2 (cruise conditions), the concept achieves a lift coefficient of approximately 6, about 95% of the theoretical maximum for a half-circular airfoil (2π), with a corresponding lift-to-drag ratio of around 24. As the Mach number increases to 0.3, the accelerated flow over the upper surface of the airfoil becomes locally transonic. Further analysis across a range of angles of attack (±150) at Mach 0.2 confirms the concept’s ability to maintain high lift and unseparated flow behavior, underscoring the effectiveness of the AFC system in enhancing aerodynamic performance.

Abstract: In the continuous quest to enhance the efficiency and sustainability of flight, the natural world offers a plethora of strategies and adaptations that can be harnessed in aviation technology. This review paper explores the multifaceted approaches of energy harvesting and drag reduction observed in nature, emphasizing their potential applications in modern aircraft and drone design. It delves into the study of micro and macro structures in various species, such as the drag-reducing micro-structures of riblets on bird feathers. The paper further investigates the broader morphological adaptations in birds and insects, including topics such as beak shape, coloration, flight configurations, materials, molting, and airfoil design for their contributions to aerodynamic proficiency. In addition, this review highlights various energy harvesting techniques observed in nature, such as soaring and ground effect exploitation, and their potential integration into aircraft design for improved endurance. Through a comprehensive review of these natural phenomena, this work aims to provide valuable insights for the development of innovative, eco-friendly aviation technologies, contributing to the global effort to reduce the environmental impact of air travel while improving the viability of drones in the nano to micro range.