Vertical Take-off Research Articles

Influence of Airfoil Geometry on VTOL UAV Aerodynamics at Low Reynolds Numbers

This study examines the impact of airfoil geometry on the aerodynamic properties of a low Reynolds number flying wing unmanned aerial vehicle (UAV). The investigation was conducted at three Reynolds numbers (1×106, 2×106, and 5×106), all under a constant Mach number of 0.3 during subsonic flight. Four distinct airfoils from the NACA and Selig series were analyzed using XFLR5 v6.61, with the angle of attack varying from -5° to 15°. Among the airfoils, NACA 6409 consistently demonstrated superior aerodynamic performance across all Reynolds numbers. Notably, at a Reynolds number of 1×106, NACA 6409 achieved a peak lift coefficient (Cl) of 1.584 at an angle of attack of 11.1°, indicating high efficiency. Additionally, the study explored the angles of attack where the drag coefficient (Cd) increased sharply, as well as the lift-to-drag ratios (Cl/Cd), providing a comprehensive understanding of stalling behavior and the balance between lift and drag. These findings offer valuable insights into the aerodynamic efficiency of airfoils in the context of vertical takeoff and landing (VTOL) UAV design, underscoring the importance of further research to optimize airfoil designs for enhanced VTOL UAV performance.

The Diverse Applications of Aerospace Drones: From Defense to Humanitarian and Commercial Uses

This research investigates the extensive applications of aerospace drones across defense, humanitarian, and commercial sectors, showcasing their transformative impact on modern industry. Aerospace drones have become pivotal tools in diverse settings—from defense and tactical operations to humanitarian aid and infrastructure management—offering operational efficiencies, cost savings, enhanced safety, and innovative solutions to complex challenges. This study explores defense applications such as military reconnaissance, where Vertical Take-Off and Landing (VTOL) drones enable effective surveillance in challenging terrains. In humanitarian settings, drones are utilized for disaster response in earthquake and flood zones, providing critical functions like search-and-rescue, real-time damage assessment, and medical supply delivery. Commercially, drones support long-range infrastructure inspections, smart agriculture, and environmental monitoring, driven by advancements in imaging and remote sensing. The project emphasizes the technical challenges and ethical considerations associated with drone deployment, particularly the need for robust AI and autonomous navigation systems in dynamic and unpredictable environments. Collaborations with international aerospace firms and humanitarian organizations have further refined drone integration strategies in both civilian and military contexts. The research concludes with a discussion on regulatory frameworks and environmental impacts, aiming to provide a comprehensive view of thefuture of aerospace drones and their role in addressing global challenges.

Lightweight aircraft design: Integrating biomechanics and algorithm optimization for drone construction using paper materials

Lightweight aircraft design emphasizes materials like composites, alloys, and advanced polymers to reduce weight while ensuring structural integrity. Streamlined aerodynamics, efficient propulsion systems, and optimized component layout further enhance performance. The purpose of this research is to develop an innovative aircraft design model for drones, integrating algorithm optimization techniques and lightweight materials to enhance the performance and efficiency of drones with the utilization of open-source software. We apply this structure to the construction of drones with fixed-wing (FW) and vertical take-off and landing (VTOL) configurations. The aircraft’s body is constructed using lightweight materials such as glass fiber fabric (Gff) and extruded polystyrene foam (XPS), employing a vacuum-assisted wet layup technique for fabrication. Multi-objective Co-evolving Ant Colony Optimization (MC-ACO) was used to improve the construction of drones with VTOL and FW capabilities. This strategy enabled it to be easier to achieve the trade-offs required for a generalist drone design, such as range, payload capabilities, and swarm operations, which were then evaluated against commercially available software to evaluate the effectiveness. Incorporating biomechanics into the design method permits higher consideration of user interaction with drones. The findings indicate that low-fidelity architecture is a suitable starting point for prototyping under limited time frames. The paper concludes with a discussion of the technical constraints of employing free software, as well as some practical concerns for flight testing drones with hybrid configurations.

Fast-Time Simulations to Study the Capacity of a Traffic Network Aimed at Urban Air Mobility

This article investigates viable solutions to implement an Urban Air Mobility network in Milan, Italy, and analyzes its influence on the airspace capacity. The network comprises eight vertiports for passenger transport among two main airports in the area and the city using electric vertical take-off and landing aircraft (eVTOLs). A Fast-Time Simulation (FTS) model with the software AirTOp (Air Traffic Optimization) allowed the evaluation of the ideal capacity of the network by varying two configurations, which differ from each other in terms of the number of Final Approach and Takeoff areas (FATOs). The results show how it is possible to reach high hourly capacities (in the order of one hundred), thus allowing the use of the service for about 4% of the total passengers passing through the two airports during the reference day chosen for this study. However, the results are ideal due to the strong idealism of the system, which overlooks several factors, and they should be considered as the maximum limit that can be obtained. Despite this, the method presented in this article can also be adapted for other urban areas with high population densities. In addition, the use of a simulation tool of this type allows, in addition to a numerical analysis, a qualitative analysis of the network behavior in terms of traffic, thus highlighting the criticalities of the proposed systems.

Options for future European reusable booster stages: evaluation and comparison of VTHL and VTVL return methods

AbstractIn the past, the majority of system studies on reusable space transportation performed within Europe focused on concepts relying on lift-generating wings for recovery. Recently, vertically landing concepts similar to those deployed successfully by SpaceX have moved to the center of technical attention. Both recovery and landing strategies have their pros and cons and it is not obvious what would be a sound choice for Europe. Therefore, the German Aerospace Center DLR initiated a parametric system study, named ENTRAIN, that evaluates the impact of different return options on the launcher design on a technical level: the vertical take-off, vertical landing method (VTVL) as used by SpaceX compared to the vertical take-off, horizontal landing (VTHL) method as used for the Space Shuttle. Within this study, launchers were designed using different propellant combinations, staging velocities and engine cycles. The designed launchers are evaluated in this paper regarding performance, technical difficulties, operational aspects, size, mass and complexity.

Design and implementation of a nonlinear observer for a novel Quadrotor UAV: the HELIPLANE

This study presents the design and dynamic modeling of a new type of quadrotor UAV, referred to as the Heliplane, which integrates the vertical take-off and landing (VTOL) capabilities of a multirotor with the horizontal flight efficiency of a fixed-wing aircraft. The modeling process involved creating a dynamic representation of the Heliplane, with special attention to the determination of its aerodynamic coefficients, which were calculated using SolidWorks Flow Simulation. The aerodynamic forces, including lift and drag, were analyzed based on the flow characteristics around the Heliplane's structure. To further enhance the system's performance, a nonlinear observer based on a sliding mode approach was synthesized. This observer was designed in a triangular form to ensure accurate state estimation and robust control, even in the presence of model uncertainties. The observer's key advantage lies in its finite-time convergence, which guarantees quick and precise tracking of the Heliplane's state variables. Simulation results demonstrated the effectiveness of the proposed observer in estimating the rotational and translational velocities with minimal deviation. The sliding mode observer's performance suggests its suitability for control and fault detection tasks in UAV applications, particularly in challenging operational environments.

The Design of Improved Series Hybrid Power System Based on Compound-Wing VTOL

Hybrid power systems are now widely utilized in a variety of vehicle platforms due to their efficacy in reducing pollution and enhancing energy utilization efficiency. Nevertheless, the existing vehicle hybrid systems are of a considerable size and weight, rendering them unsuitable for integration into 25 kg compound-wing UAVs. This study presents a design solution for a compound-wing vertical takeoff and landing unmanned aerial vehicle (VTOL) equipped with an improved series hybrid power system. The system comprises a 48 V lithium polymer battery(Li-Po battery), a 60cc internal combustion engine (ICE), a converter, and a dedicated permanent magnet synchronous machine (PMSM) with four motors, which collectively facilitate dual-directional energy flow. The four motors serve as a load and lift assembly, providing the requisite lift during the take-off, landing, and hovering phases, and in the event of the ICE thrust insufficiency, as well as forward thrust during the level cruise phase by mounting the variable pitch propeller directly on the ICE. The entire hybrid power system of the UAV undergoes numerical modeling and experimental simulation to validate the feasibility of the complete hybrid power configuration. The validation is achieved by comparing and analyzing the results of the numerical simulations with ground tests. Moreover, the effectiveness of this hybrid power system is validated through the successful completion of flight test experiments. The hybrid power system has been demonstrated to significantly enhance the endurance of vertical flight for a compound-wing VTOL by more than 25 min, thereby establishing a solid foundation for future compound-wing VTOLs to enable multi-destination flights and multiple takeoffs and landings.

Dynamics and control of a high-altitude balloon with slung load

Abstract The high-altitude balloon proposed in this paper is a long-life balloon carrying a payload through a cable that flies at 20km altitude in near space. A dynamic model of the system, including the thermodynamics of the buoyancy body coupled with a hanging model of the pod, is developed using the Newton–Euler method. The buoyancy body consists of a helium balloon and a ballonet. A differential pressure difference-based altitude adjustment is achieved by tracking the pressure difference at the target altitude. A dynamic simulation of the buoyancy body with a slung pod in autonomous vertical takeoff and altitude regulation processes is presented. The internal thermodynamic variations and pressure differential of the buoyancy body are given. The air mass exchange and blower flow control of the ballonet are validated. The altitude holding error is analysed. The maximum pull force that the cable can withstand is calculated, and the maximum attitude angles of the pod during the ascending and descending processes are depicted. Simulation results provide basic knowledge for the structural design and payload installation of pods.

Transition flight of a concept of lifting-wing quadcopter

Abstract This paper presents the concept of a lifting-wing quadcopter unmanned aerial vehicle (UAV), a vertical take-off and landing vehicle (VTOL) with a rear wing, a canard at its front and four propellers. The aerodynamic surfaces are designed so that their mounting angle can be adjusted and fixed before flight, so its performance in transition flight can be studied for a combination of wing and canard mounting angles. A dynamic model using rigid-body equations of motion is presented, which is used to compute the transition flight trajectory from hover to cruise in horizontal flight. The trim conditions were computed for a range of fixed wing and canard mounting angles to study the effects of these variables on transition trajectory parameters such as required power, body pitch angle and propeller rotation speeds as a function of flight speed. Furthermore, a transition flight control algorithm is presented, which has a cascaded PID controller and a reference scheduler to switch between the proper reference states, controls and control allocation matrix. Finally, the transition control algorithm of the conceptual UAV is numerically simulated. Results show that this configuration can perform a fast and smooth transition from hover to cruise flight using the proposed flight control algorithm, substantially reducing required propulsive power in cruise of up to 64%. The application of the control algorithm made notable a transition manoeuver that consists of negatively inclining the aircraft at a negative pitch angle, initially at high intensity, and as the final cruising speed approaches, the inclination is attenuated until the equilibrium pitch angle is reached. Simultaneously with the negative inclination of the pitch angle, there is a slight drop in altitude, which is quickly resumed as the trajectory develops until the final cruising speed. Lastly, this aircraft configuration can be widely used in applications where performance gains in operations currently carried out by multicopters, which cover large distances and need long flight time, would bring great operational advantages.

The Overview of Vertical Take-Off and Landing Technology

Vertical takeoff and landing (VTOL) technology is garnering significant attention in the aviation industry due to its distinct benefits and wide range of potential applications. A long runway is not necessary when using VTOL technology, which allows aircraft to take off and land vertically straight from the ground. Air mobility in cities, military activities, and emergency response are just a few of the areas where this technology is beneficial. This essay will provide an overview of the development, application, and future of vertical takeoff and landing technology. The technologys operating principles, advantages and limitations will also be explored. Overall, VTOL technology offers a tremendous leap in aircraft technology, with numerous possible uses. Even though there are still difficulties, more research and development will probably result in improvements and broader use.

Position and reduced attitude trajectory tracking control of quadrotors: Theory and experiments

Multirotor aerial vehicles are versatile flying robots that perform hovering, vertical take-off and landing, and aggressive maneuvers in a 3D environment. Due to their underactuated nature, the aerial vehicles' position and orientation cannot be controlled independently. For this reason, most of the quadrotors' tasks involved position tracking or regulation tasks. This paper focuses on the position-tracking problem of quadrotors using the reduced orientation of the vehicle, meaning that only two degrees of freedom of the robot's orientation are controlled. We propose an almost global exponential reduced attitude control law that aligns the aerial robot's thrust direction with the desired force that drives the robot along the desired position trajectory. For the translational subsystem, we propose a dynamic control law that drives the position and velocity of the quadrotors asymptotically to the desired trajectories. The proposed attitude control law is computationally simple, and thus, it is suitable to run on board. Finally, we provide experimental results performed on a low-cost quadrotor and a comparison study with a full-attitude controller to illustrate the performance and advantages of the proposed control laws.

A vertical take-off and landing (VTOL) unmanned aircraft vehicle trajectory control model with air-launched missiles

Purpose In today’s technology, the significance of unmanned aerial vehicles is steadily increasing. Many unmanned aerial vehicles design, especially those used for military purposes, have achieved autonomy from human operators. Undoubtedly, one of the most crucial features of these aircraft is their vertical take-off and landing (VTOL) capability. Inspired by quadrotor methodology, this paper aims to conduct, a modeling of an aircraft with VTOL capabilities. Design/methodology/approach The impact of releasing air-launched missiles, considered as the useful payload carried during the flight of the aircraft, has been taken into account in this modeling. The release of air-launched missiles disrupts both the symmetric structure of the system and alters the mass and inertia parameters. Simulations were conducted to investigate scenarios involving the simultaneous release of all air-launched missiles and their release at different times. Findings The investigation focused on determining how quickly an aircraft, aiming to consecutively hit targets, can return to its desired trajectory. The time interval between the consecutive releases of two air-launched missiles has been identified. Originality/value It is crucial for a VTOL-capable aircraft to possess a unique modeling structure to examine its capability of releasing air-launched missiles in various scenarios. This entails understanding not only the aircraft’s VTOL functionality but also its ability to effectively release missiles in different operational conditions.

Design and Simulation of eVTOL Aircraft Thermal Management System

Abstract Vertical Take-off and Landing (VTOL) aircraft with hybrid or fully-electric propulsion systems are becoming popular for Urban Air Mobility (UAM) applications. However, they face challenges such as limited power and energy density, stringent operating temperature constraints, and the generation of low-grade waste heat. These issues emphasize the need for effective Thermal Management Systems (TMS) design. In light of the above, this paper aims to design the TMS for a parallel hybrid electric XV-15 aircraft, a widely known civil tiltrotor concept. The TMS is integrated into the aircraft system to assess its impact on energy efficiency and emissions at both aircraft and mission levels. This study considers current state of the art technology and expected advancements over the next two decades to identify the benefits of electrification. In the designed TMS, liquid cooling cold plates serve as the main heat acquisition and cooling system for each electric component. An air-coolant heat exchanger is also incorporated to dissipate the accumulated heat load. The study conducts a comparative analysis to determine the optimal TMS design point. It involves a comparison between two design scenarios: one focused on the cruise condition, which constitutes a significant portion of the flight mission, and another designed specifically for peak heat load conditions. This ensures a holistic evaluation of the TMS's performance across various flight phases, balancing efficiency and resilience to peak demands. Finally, the energy efficiency and emission penalty associated with the TMS integration are quantified and discussed in the study.

Active Disturbance Rejection Flight Control and Simulation of Unmanned Quad Tilt Rotor eVTOL Based on Adaptive Neural Network

The unmanned quad tilt-rotor eVTOL (QTRV) is a variable-configuration aircraft that combines the features of vertical takeoff and landing (VTOL), hovering, and high-speed cruising, making its control system design particularly challenging. The flight dynamics of the QTRV differ significantly between the VTOL and cruise modes, and are further influenced by rotor tilt and external wind disturbances. Developing a unified, highly coupled nonlinear full-flight dynamics model facilitates flight control system design and simulation verification. To ensure stable tilt of the QTRV, a tilt corridor was established, along with the design of its tilt route and manipulation strategy. An adaptive neural network active disturbance rejection controller (ANN-ADRC) is proposed to ensure stable flight across all modes, reducing the control parameters and simplifying tuning while effectively estimating and compensating for unknown disturbances in real time. A hardware-in-the-loop (HIL) simulation system was designed for full-mode flight control simulation, and the results demonstrated the effectiveness of the proposed control method.

Noise and inflow velocity measurements of fixed pitch rotors in edgewise flight

A common design of many of the proposed generation of electric Vertical Takeoff and Landing (eVTOL) vehicles involves fixed pitch rotors in edgewise flight. These applications typically have significantly lower tip Mach numbers than conventional rotor-craft and involve distributed smaller rotors making them operate at lower Reynolds numbers and hence likely having a greater sensitivity to gusts and environmental turbulence. This work will present results of studies with fixed pitch rotors conducted in the UF Anechoic Wind Tunnel Facility. The studies involve radiated noise, thrust and stereoscopic Particle Image Velocimetry to measure the inflow velocity to the rotor plane. The measurements were taken for un-altered free stream conditions as well as ones subjected to three different turbulence generation grids. The results provided show that there can be effects at moderate levels of free stream to turbulence to the rotor efficiency and radiated noise.

Inclined Installation Effect on the Offset Strip Finned Heat Exchanger Designed for a Hybrid Electric Propulsion System in Electric Vertical Take-Off and Landing

The plate-fin heat exchanger was designed for the liquid cooling thermal management system of the hybrid electric propulsion system for an electric vertical take-off and landing (eVTOL) vehicle. The offset-strip fin design was applied, and the performance of the heat exchanger was evaluated, particularly with respect to the inclination of the airflow entering the heat exchanger. The estimated performance during the design phase matched well with the experimental results. The inclination of the heat exchanger had a minimal effect on thermal performance, with a slight increase in performance as the inclination increased. However, the pressure difference along the airflow was affected, likely increasing as the inclination increased. The sensitivity of various parameters on coolant temperature was also investigated. The air inlet temperature had a significant effect on coolant temperature, followed by the coolant flow rate. Therefore, when designing the thermal management system, careful consideration should be given to the ambient air temperature and coolant flow rate.

Triple Jump Performance Parameters and Inter-Limb Asymmetry in the Kinematic Parameters of the Approach Run in International and Paralympic-Level Class T46/T47 Male Athletes

Background/Objectives: The triple jump is included in the Paralympic Athletics competition. The aim of the research was to examine the relationship of the phase ratios and the inter-limb asymmetry in the spatiotemporal parameters of the approach run in Paralympic and international-level Class T46/T47 triple jumpers. Methods: Eleven Class T46/T47 male athletes were recorded during the examined competitions. Step length (SL), frequency (SF), and average velocity (ASV) for the late approach run as well as the length and the percentage distribution of each jumping phase (hop, step, jump) were measured using a panning video analysis method. The inter-limb asymmetry was estimated using the symmetry angle. Results: No significant inter-limb asymmetry was found (p > 0.05). In addition, SL, SF, and ASV were not different (p > 0.05) between the steps initiated from the ipsilateral and the contralateral leg regarding the impaired arm. However, the direction of asymmetry for SF was towards the ipsilateral leg to the impaired arm in the majority of the examined athletes. The maximum speed of the approach was correlated with the triple jump distance and the magnitude of asymmetry for AVS was correlated with the vertical take-off velocity and angle for the step. Conclusions: Since the distance of the triple jump related with the peak approach speed added the negative correlation of peak approach speed with the magnitude of the symmetry angle for SL, it is suggested to minimize the asymmetries in the step characteristics during the approach run to improve triple jump performance in Class T46/T47 jumpers.

Regulatory and spectrum policy challenges for combined airspace and non-terrestrial networks

The recent advancements in the aviation and space industries facilitate new types of users in the sky, e.g., electrical vertical take-off and landing (eVTOL) aircraft. To unlock the full potential of these innovations, it is crucial to create interconnected three-dimensional networks that integrate airspace and non-terrestrial networks (NTNs) with their terrestrial counterparts, also known as Combined Airspace and Non-Terrestrial Networks (ASN). Combined ASN needs a flexible and adaptive network architecture with multiple, and partly converging technologies, such as air-to-ground, satellite, and high-altitude platforms, with a focus to cover both ground and aerial users. In addition to technical challenges, spectrum policy and regulatory aspects will affect the wireless network design and management schemes in three-dimensional space. Hence, this paper introduces regulatory and spectrum policy challenges posed by the development of combined ASN. This paper investigates a hypothetical urban air mobility use case with an eVTOL aircraft that operates as a flying taxi.

Refined air-cooled battery sizing process for conceptual design of eVTOL aircraft

Recently, electric vertical takeoff and landing (eVTOL) aircraft have garnered significant interest as a primary mode of transportation in advanced air mobility (AAM). For the conceptual design of eVTOL aircraft, where a broad design space must be explored rapidly, a practical and reliable battery sizing process is essential. This process needs to employ models with low computational cost while comprehensively considering two key factors: voltage drop characteristics and thermal effects. However, existing research on battery sizing mainly relies on constant specific energy or power, neglecting these factors. This oversight can lead to significant discrepancies in battery sizing between the conceptual and detailed design phases. To address these limitations, this paper introduces a refined battery sizing process. Our approach incorporates models for battery voltage drop, heat generation, and a cooling system. A Thevenin equivalent circuit is used to model voltage drop and heat generation, with a novel calibration method developed for accurate predictions of voltage and temperature profiles. An air cooling system is adopted for its simplicity and lightweight design, and a corresponding model is constructed. Applying our process to eVTOL aircraft sizing revealed that incorporating temperature, along with the depth of discharge (DoD) and C-rate, as constraints in battery sizing led to a 4.6 % decrease in specific energy and a 4.2 % decrease in specific power. These findings underscore the importance of considering temperature in battery sizing. Additionally, sensitivity analyses provided insights into which thermal management system, air-cooled or liquid-cooled, is more appropriate for the battery under various operating conditions.

Incremental Sliding Mode Control for Predefined-Time Stability of a Fixed-Wing Electric Vertical Takeoff and Landing Vehicle Attitude Control System

Incremental Sliding Mode Control for Predefined-Time Stability of a Fixed-Wing Electric Vertical Takeoff and Landing Vehicle Attitude Control System