The active control of dynamic stall on helicopter blades, wind turbine blades, fixed-wing aircraft, and flapping-wing flyers is reviewed. Different dynamic stall problems are identified, stall types are defined, control metrics are established, and the parameter space is delineated. For helicopter and wind turbine blades, as well as small unmanned aerial vehicles, the primary objective is generally to eliminate or mitigate the effects of dynamic stall. However, in certain fixed-wing, flapping-wing, and energy-generation applications, the goal is to utilize or exploit dynamic stall effects.A major emphasis is placed on nominally incompressible flows, including dynamic stall management, passive control devices, steady and unsteady active control techniques, scheduled control, iterative learning control, closed-loop control, and the role of dynamic stall control in flapping-wing flight. Significant control authority can be achieved by either suppressing or inducing dynamic stall through low-frequency leading-edge slot blowing on thick airfoils, which is particularly suitable for wind turbine blade load control. High-frequency unsteady dynamic stall control—typically achieved using fluidic, combustion-based, or plasma-based devices—is effective because the resulting stall-controlling leading-edge vortices are generated more than an order of magnitude faster than dynamic stall vortices.Simple reactive control can be achieved through the adaptation of stall warning methods, and a feedforward/feedback control architecture is shown to be both practical and effective for gust alleviation in small vehicles. In flapping-wing flyers, the role of dynamic stall control differs between propulsive and hovering flight. In propulsive flight, active flow control may enhance propulsive efficiency. In hovering flight, a relationship exists between Strouhal numbers associated with insect flight, leading-edge forcing on flat-plate airfoils and low-aspect-ratio wings, and vortex shedding.Under subsonic compressible conditions, dynamic stall is driven by shock-induced separation. In such cases, leading-edge modifications—including vortex generators, discrete wall-normal jets or micro-jet blowing, and dielectric barrier discharge actuation—demonstrate significant control potential. Computational methods play a vital role in advancing the application and evaluation of active control strategies by enabling system-level studies that assess aerodynamic, aeromechanical, energetic, and structural benefits.
This review evaluates six oxygen (O2) sensor technologies for potential use in crewed spaceflight, with emphasis on rocket engine bay environments. Sensor types examined include electrochemical (zirconia and galvanic), optical (absorption and fluorescence), paramagnetic, semiconductor (titania), chemiluminescent, and ultrasonic. Existing oxygen sensor standards and performance claims rarely account for the coupled effects of vibration, low pressure, thermal transients, contamination, and ignition risk in propulsion-adjacent environments. To address this gap, each sensor is assessed based on operating principles, materials, and performance against mission-driven criteria such as accuracy, response time, vibration tolerance, temperature resilience, stability, and ease of integration. A comparative trade-off analysis evaluates the relative suitability of each sensor type. The analysis concludes that fluorescent, zirconia and galvanic sensors offer the best overall balance of environmental robustness and sensing performance with galvanic sensors being viable for short-duration use. Paramagnetic, semiconductor, and chemiluminescent sensors face limitations due to fragility, thermal constraints, or integration complexity. These findings support the identification of reliable oxygen sensing technologies for mission-critical environments where accurate oxygen monitoring is required under extreme thermal, pressure, vibration, and chemical conditions.
The use of advanced energy storage systems is seen as a major driver of improved operational performance and reduced environmental impact of vertical takeoff and landing aircraft. As a zero-emission alternative to traditional fossil-fueled internal combustion engines, high-density electrification is a viable step change, particularly for sustainable Urban Air Mobility. Current battery technologies achieve 250 Wh/kg at the cell level but incur weight increases from structural packaging and thermal management. Moreover, aviation-specific requirements varying across distinct flight phases make battery integration challenging. Consequently, new battery chemistries providing higher energy densities, hydrogen use, and innovative hybrid configurations are projected to be adopted in the upcoming years, which have been reviewed in depth to provide a system-level roadmap for the transition to sustainable urban air mobility.
Swarm intelligence has emerged as a transformative paradigm for autonomous space robotics, enabling scalable, robust, and adaptive behaviors through decentralized coordination of multiple agents. Inspired by collective phenomena in nature, swarm intelligence provides solutions to the challenges of extreme space environments, where resilience, autonomy, and fault tolerance are crucial. This review explores recent advances in the modeling, control, and validation of swarm-based space robotic systems. Mathematical frameworks ranging from single- and double-integrator dynamics to orbital swarm dynamics are examined, alongside formation control strategies such as consensus-based, leader–follower, virtual structure, and behavior-based approaches. The review covers swarm controllability, scalability, and performance metrics, highlighting trade-offs between efficiency, robustness, and computational complexity. Emerging optimization paradigms, including bio-inspired algorithms, hybrid global-local strategies, and multi-objective optimization, are surveyed for their applicability to mission-critical tasks such as debris removal, and distributed satellite constellations. The review also investigates numerical simulation platforms and experimental testbeds associated with swarm intelligence, highlighting their role in bridging the gap between theory and deployment. Case studies of current and proposed space missions illustrate the transition of swarm intelligence from conceptual design to operational reality, while trends in reinforcement learning, blockchain integration, and large language model-guided swarms signal future research directions. By consolidating theoretical foundations, experimental progress, and mission applications, this paper outlines the opportunities and challenges of harnessing swarm intelligence for future space exploration and infrastructure.
Rocket-based combined cycle (RBCC) engines are considered one of the primary power solutions for future reusable vehicles, near-space high-speed flight vehicles and other novel types of aerospace vehicles. In recent years, RBCC power has made significant breakthroughs in key research areas, such as mode transition, wide-domain combustion organization and flow channel design. The ejector mode, the most distinctive among the RBCC engine's modes, serves as a bridge between the ground and the ramjet mode. The performance of the ejector mode plays a pivotal role in determining the vehicle's overall design. This paper first reviews publicly reported research progress on the ejector mode in typical RBCC vehicles and analyzes the thrust and specific impulse gain characteristics of the ejector mode in each scheme based on public data. Second, independent research progress on the gain characteristics of the ejector mode in public reports is reviewed, and the thrust and specific impulse gain characteristics achieved are analyzed. Finally, the key technical directions for the development of rocket gain technology are identified, highlighting directions for improving ejector mode performance and promoting the integrated design of ejector mode gain technology with other modes.
This review comprehensively synthesizes the progress concerning the aerodynamic and aeroelastic characteristics of morphing aircraft over the past years (circa 2010-2026). The morphing strategies are categorized into three primary dimensions based on established classifications: chordwise morphing (primarily camber morphing), spanwise morphing (primarily spanwise bending), and planform morphing (including sweep and span morphing). For each morphing strategy, the investigations are systematically reviewed, detailing advances in steady and unsteady aerodynamics, aeroelastic modeling and characteristics, and the application of active control strategies (aeroelastic and maneuver control). Distinct research priorities exist for different morphing strategies: chordwise camber morphing focuses primarily on aerodynamics, while spanwise bending centers on aeroelastic modeling and characteristics. Moreover, given the potential application in configuration adjustments across different flight phases, research on sweep and span morphing predominantly focuses on steady and quasi-steady states. The review also summarizes the current methodologies employed in aerodynamic and aeroelastic analysis and highlights the primary approaches for incorporating aerodynamic (primarily computational fluid dynamics) and structural nonlinearities, as well as their interaction frameworks, such as coupling with computational structural dynamics. The implementation of morphing in control systems is also reviewed, where a notable trend is the integration of control law modules (primarily feedforward and feedback control) into fluid–structure interaction frameworks. As a conclusion, the gap between model and practical application for morphing aircraft still exist. The challenges of detailed modelling for actuation system and time-varying aerodynamics should be paid more attention.
The lunar polar permanently shadowed regions (PSRs), abundant in volatile resources such as water ice, are pivotal for future lunar exploration and in-situ resource utilization. However, the persistent absence of sunlight within these regions renders conventional energy supply methods ineffective, presenting a major obstacle to sustained surface operations. In contrast to Radioisotope Thermoelectric Generators (RTGs), which are constrained by low specific power and high launch mass, or physical cables limited by rugged crater topography, Laser Wireless Power Transmission (LWPT) offers a flexible and lightweight alternative. This review specifically focuses on surface-to-surface LWPT architectures for lunar exploration, in which electrical power generated at illuminated lunar surface sites is transmitted by laser to receivers operating on the lunar surface within permanently shadowed or otherwise energy-deficient regions. Orbit-to-surface laser power transmission, although also relevant to future lunar energy systems, is beyond the scope of this review and is discussed only briefly to contextualize the broader development of space power beaming. With demonstrated energy densities exceeding 1 kW/m2 in ground tests, LWPT presents a compelling candidate for sustained power delivery to PSRs. Nevertheless, the extreme cold, intense radiation, and highly complex lunar dust plasma environment pose substantial challenges to the stability and reliability of LWPT systems. In response, advanced technical strategies—including thermal management, beam shaping, intelligent control, and material optimization—have been developed to improve system adaptability under these harsh conditions. Distinct from previous reviews that primarily focused on component-level metrics, this paper provides a systematic feasibility assessment of LWPT specifically tailored to surface deployment in lunar polar regions. We synthesize the multi-physics coupling impacts of these environmental factors on transmission performance and present quantitative link budgets for representative mission scenarios. The results indicate that LWPT will catalyze a paradigm shift in lunar polar energy supply, enabling efficient, flexible, and large-scale power delivery for future lunar surface operations. The insights presented herein provide a robust theoretical foundation and technical reference for the development of next-generation energy systems for sustainable lunar surface infrastructure.
In an effort towards sustainable aviation, the use of liquid hydrogen as an energy carrier has the potential to enable zero carbon emission flights. While the idea has been around for decades, challenges in storing and handling liquid hydrogen safely and reliably to meet aviation standards still remain. As liquid hydrogen needs to be stored at −253 °C, the tank architecture, interfaces and sensors differ greatly from those used for kerosene.Previous studies have investigated and rated certain LH2 fill level sensors for space applications but no comprehensive evaluation has been conducted regarding their suitability for future commercial aircraft. This paper aims to provide an extensive overview of LH2 fill level sensor technologies, significantly expanding upon previous research including novel measurement techniques and commenting on the technology readiness level. No fuel level sensor concept excels across all evaluation criteria. Therefore, the authors selected 6 out of the 22 measurement concepts presented in this study to be investigated further in order to advance their respective Technology Readiness Levels.
Quick Access Recorder (QAR) data is a critical source of high-fidelity information, enabling a deep characterization of aircraft, engines, and their subsystems within complex and dynamic operational environments. Even minor variations in manufacturing or operational wear can cause technically identical systems to develop distinct performance characteristics over their service life. QAR acts as a digital memory of this individuality, capturing a wide array of parameters that reflect a system’s physical reflexes and characteristic habits. Through this memory, normal or abnormal behaviors can be monitored during standard flight phases, under stressful conditions, and against the effects of aging. Thus, the performance evolution of the system over time can be examined by analyzing its alignment with expected behavior, as well as accuracy, lag, or deviation of its responses to control commands. Given its clear value, QAR data has been the subject of extensive research over the years. Therefore, the purpose of this review is to provide a thematic map of the applications of QAR data in aviation, documenting its evolution over the past 25 years. A total of 380 studies reveal that research concentrates around three primary focal points: (i) flight safety and risk management, (ii) operational efficiency based on fuel consumption, and (iii) system health management, with an emphasis on engines. Within these areas, several core topics have emerged. Building on these topics, this paper provides a holistic assessment of QAR analysis, from raw data preparation and feature engineering to the application of various statistical and data-driven approaches across diverse domains.
Urban Air Mobility (UAM) is emerging as a transformative mode of transportation, operating in densely populated, acoustically complex urban environments where public tolerance to noise is substantially lower than in conventional helicopter operations. In this context, even moderate noise can critically affect community acceptance, regulatory approval, and operational deployment, making it a central challenge for urban integration of electric vertical take-off and landing (eVTOL) aircraft. This review synthesizes recent advancements in understanding eVTOL vehicle aerodynamic noise and explores emerging noise control strategies. The primary noise sources are rotor self-noise and interaction noise arising from rotor–rotor, rotor–airframe, and rotor–duct interferences. Distinct configurations—such as multirotor, tiltrotor, lift+cruise, and ducted-fan designs—exhibit notable differences in noise characteristics and source mechanisms, leading to shifts in dominant noise types across different flight conditions. Passive noise mitigation approaches, such as blade geometry optimization, blade serrations, surface treatment, and porous materials, are critically reviewed alongside blade- and flow-based active techniques as well as rotor synchrophasing. Research methodologies span theoretical modeling, numerical simulations, and experimental measurements. Current limitations, such as gaps in accurately simulating complex interaction noise and validating control strategies under real-world conditions, are fairly addressed. The review concludes by advocating for integrated design frameworks that harmonize noise reduction with safety, efficiency, and regulatory compliance, stressing the need for interdisciplinary collaboration to advance scalable UAM noise solutions. By integrating current knowledge on eVTOL noise mechanisms and control strategies, this review aims to inform research priorities and guide industry efforts toward meeting acoustic certification standards for sustainable urban air mobility.
The integration of game theory and multi-agent systems (MASs) has been systematically examined as a transformative paradigm for modeling strategic interactions among autonomous entities in advanced technological systems. This paper focuses on the synergy between game-theoretic principles and MASs, with emphasis on their applications to complex operational domains such as autonomous system coordination, distributed system control, and intelligent network management. Firstly, foundational concepts, historical developments, and classifications of both fields have been analyzed. The analysis highlights how game theory provides robust frameworks for addressing challenges in cooperative control, resource allocation, and swarm dynamics within advanced operational contexts. For instance, game-theoretic approaches to swarm-vs.-swarm engagement in contested environments and distributed guidance for interception systems have been investigated. Subsequently, key application scenarios have been explored, including robust path optimization for autonomous agents operating under uncertain conditions, such as GPS-denied or similar challenging environments. Challenges unique to complex applications, such as high-dimensional state spaces, real-time computational demands, and communication constraints in dynamic environments, have also been identified. Finally, future research directions emphasize the development of scalable distributed algorithms, enhancement of resilience against adversarial disruptions, and optimization of decision-making under incomplete information—critical for advancing autonomous systems in diverse technological fields. Overall, this paper offers a comprehensive analysis of the application of game theory in MASs and anticipates future advancements in the field.
The paper focuses on the exploration and comparison of zero-emission technology strategies for regional aircraft. While significant progress is made on the development of technologies, systems and aircraft configurations, major challenges and uncertainties mean that various strategies are considered but are difficult to compare as they rely on different technologies, metrics, requirements, maturity levels and sustainability targets. A novel, holistic approach that captures inter-dependencies, synergies and combined impact of technologies is developed to evaluate the feasibility of such aircraft over 2 horizons, quantify performance and emissions through various phases of the life cycle, establish technology bottlenecks and required step changes and classify developments in terms of impact and risk. For at least 30 passengers at 300 nmi, significant advances are required for fuel cells (2 kW/kg), electric machines (13 kW/kg), power distribution (>1.5 kVolts), and thermal management systems (3.5 kW/kg and 3.5 kW/kW). These will lead to major mission level (+90%) and lifecycle energy penalties (up to +177%) with a carbon intensity level of 6.5 kgCO2/kgH2 (ex. blue, turquoise, green hydrogen) required to breakeven current CO2 levels. Step changes including superconductivity and high temperature fuel cells, along with aircraft mass and drag reductions are required to increase capacity to pax>40 and 800 nmi, and achieve energy reductions against existing designs. The energy density of batteries and the need of gas turbines to meet diversion and hold requirements limit full electric variants to 30 passengers at 200 nmi with 480 Wh/kg battery energy density but they can offer an exceptional energy per passenger benefit (∼40% reduction) against current aircraft.
Airborne Wind Energy (AWE) systems are tethered aircraft for wind energy harvesting that, since not constrained by a tower like conventional wind turbines, can operate at high altitudes with access to a better wind resource. This work presents a comprehensive review of the current knowledge and state of the art of the aerodynamics of AWE systems. Aerodynamics, which affects power generation, flight physics, control, structure, and safety, among others, is the most transversal area for AWE technology. It is a rich field of experimental and theoretical research due to its significant impact on performance. The review starts organizing actual AWE prototypes, some of them reaching the 100 kW range, according to some selected dimensionless parameters strongly related with their aerodynamics including the Reynolds and Mach numbers, the aspect ratio, the maximum lift-to-weight ratio and aerodynamic efficiency, the reduced frequency, and the sweep and dihedral angles of the wing. AWE machines with different electrical generation solutions (on the ground and onboard), links to the ground (tethered and rotary machines), aircraft (non-rigid or soft, hybrid and fixed wing), and control (aerodynamic surfaces, hanging control pod, ground-based, etc.) are considered and the implication of each architecture on the aerodynamics is discussed. After such a fundamental introduction, the work reviews the current state of AWE numerical and experimental aerodynamics, detailing the modeling methods and key findings. The numerical models are categorized into fast, low- to mid-fidelity methods based on potential flow, and high-fidelity computational fluid dynamics methods like Reynolds-averaged Navier–Stokes and Large-Eddy Simulations. Most numerical studies aim to understand local phenomena by examining the flow and pressure fields over wings, and/or to calculate the aerodynamic force and moment coefficients of 2D airfoils or entire wings. On the experimental side, the significant progress characterizing different types of aircraft in wind tunnels, water channels and in-flight during typical AWE trajectories is summarized. Special attention is paid to the experimental setups and on-board instruments that have been used for the in-situ measurements of aerodynamic variables, as well as the estimation theory and applications of the experimental data to construct aerodynamic models. Furthermore, this paper analyzes the effective application of current numerical and experimental aerodynamic knowledge and models in related areas such as dynamics and control, and fluid–structure interaction. The paper concludes with a critical assessment of the current state of knowledge, highlighting the main open questions, challenges, and opportunities in the field of AWE aerodynamics.
Since the dawn of aviation, aircraft icing has been a problem for air vehicles. Ice buildup on aircraft is a potentially serious safety issue as it can interfere with the aerodynamic characteristics. Icing alters performance and controllability of the vehicle, and hence it has been identified as one of the main causes for catastrophic accidents. Consequently, for safety reasons, the installation of devices to detect its presence has become necessary. However, ice formations can represent a threat also for other types of structures, such as high-power lines, bridge stay cables, antennas, or wind turbines, placed in environments that contribute to the ice formation. The purpose of this paper is to provide a review on the different ice detection technologies, focusing principally on aircraft icing, and classifying them according to the possible applications and their operating principle.
The renewed global interest in furthering human’s presence on the Moon has catalyzed efforts to establish a sustainable lunar base. The incentive is not only for scientific opportunities and prospects of deep-space exploration, but also for demonstrating technologies that will extend our reach throughout the Solar System. Central to such efforts is the development of robust and scalable lunar construction technologies. This survey presents a comprehensive review of the state-of-the-art in lunar construction, including environmental characterization, infrastructure development, construction methods and materials, and robotic systems. The unique challenges posed by the lunar environment are highlighted, such as extreme temperature variations, high radiation exposure, and micrometeorite impacts, with a particular emphasis on the abrasive, adhesive, and electrostatically charged lunar regolith, thus including strategies developed for lunar dust mitigation. The survey investigates the critical infrastructure that will need to be established, including habitats, power stations, communication stations, landing pads, blast berms, and more. A detailed analysis of the methods and materials that are being developed to create such infrastructure is presented, identifying which methods have demonstrated promise and garnered the most attention. A diversity of robotic technologies are required to enable the construction of the necessary infrastructure using these methods and systems, which are broken down into lunar cranes, mobile manipulators, 3D printers, and robot teams, with a particular focus on work being done to develop flight systems. The paper concludes by identifying critical research and technological gaps that must be addressed to support the next generation of lunar missions and long-term extraterrestrial habitation.
In pursuit of developing a sustainable aviation future, the application of liquid hydrogen as an energy carrier for aircraft has emerged as an appealing strategy to achieve future zero-emission goals. Liquid hydrogen is uniquely capable of meeting the aggressive power and energy requirements of aircraft systems, though utilizing it requires a substantial and extensive transition process throughout the entire industry and energy supply infrastructure. This work is intended to demonstrate the feasibility of developing a hydrogen aviation ecosystem by the year 2050, in the form of a visionary blueprint that includes forecasts in energy, operations, aircraft systems, and infrastructure. The projected 2050 scenario is informed by a meta-analysis of roadmaps and forecasts across a broad range of technical areas, where hydrogen is demonstrated to achieve technical feasibility, scalability, economic competitiveness, and deep environmental benefits for use in aviation. It is demonstrated that liquid hydrogen applications can meet the stringent safety requirements of aviation with abatement of currently recognized hazards. The increase in global hydrogen production across the coming decades is projected to reduce the life cycle emission impacts of aviation operations by over 80% by 2050, which is enabled by decarbonization of hydrogen production pathways and electrical grids anticipated across all global regions. The cost of liquid hydrogen for aircraft, including gaseous hydrogen production, liquefaction, transportation, and distribution, is projected to decrease to $3.37/kg by 2050 to become commensurate or lower cost than that projected for kerosene fuels on a per unit energy basis. With the continued increase in air traffic and global aircraft fleets, a sufficient volume of hydrogen produced and accessible by aviation is anticipated to meet the energy demands of hydrogen aircraft of 2050. Concept aircraft for future generations of regional jet, narrowbody, and widebody hydrogen aircraft are also provided, which are capable of providing extreme improvements in energy efficiency when compared to the incumbent fleet at the corresponding entry into service timeframe. A significant investment in capital is identified to establish the necessary infrastructure for liquid hydrogen use in aviation, though the vast majority of these costs are associated with off-site energy/fuel production and processing capabilities, which can be strategically co-developed with other transportation and energy industries. Based on all of these conclusions, developing a burgeoning liquid hydrogen aviation ecosystem by 2050 is entirely feasible, but it requires purposeful investment, pursuit, and alignment both within and outside of the aviation community. As such, when determining a pathway for a sustainable aviation future, the question is not whether it is possible. Rather, the question is whether we, as an aviation community, will decide to bring this future into being.
The international review journal “Progress in Aerospace Sciences” was founded in 1961 at the beginning of the Space Age. The author uses the occasion of the journal's 65th anniversary to present his personal retrospective on the circumstances that enabled the amazingly rapid aerospace systems developments during this time period amounting to a “conquest of space and time”. He follows this up with the prediction that a continued development of the global air transportation and of the space exploration systems will critically depend on the “conquest of the energy barrier”. He argues that there is an urgent need for a global Apollo Energy Project.
