A rotary-wing aircraft, or helicopter, is crucial for maritime operations due to its Vertical Take-Off and Landing (VTOL) capabilities, making it essential for small-deck Naval ships. Helicopters serve multiple roles, enhancing the Royal Netherlands Navy’s (RNLN) missions. However, the rise of Unmanned Aerial Vehicles (UAVs) in the past decade has introduced a cheaper, expendable, and more efficient alternative for certain operations, as UAVs require no pilot and can operate continuously. UAVs are ideal for tasks related to improving situational awareness, thereby increasing mission effectiveness, reducing pilot risk, and lowering fuel consumption. The RNLN aims to utilize UAVs alongside crewed helicopters on new ships to maximize operational efficiency. Both helicopters and UAVs follow three mission phases: launch, mission, and recovery, with the recovery phase being the most challenging. During the recovery phase, a crewed helicopter approaches the sailing vessel in a standardized way for which operational limits are established. These limits are essential for rough weather situations and are determined through many flight tests, which is a time-consuming, expensive and hazardous task. In addition, these operational limits only apply to a standardized approach manoeuvre. No approaches for UAVs are prescribed yet, making it difficult to determine such limits, but opens the possibility to standardize newly optimal UAV-ship approaches for which operational limits can be established. Moreover, the ship needs to manoeuvre to obtain optimal wind conditions for an approaching helicopter, which is not desired for UAVs. This means that UAVs should be able to approach and land on the ship in any wind condition. This study investigated the effect of wind on optimized UAV-ship approaches, which can be used to aid and standardize maritime UAV-ship approaches. For this objective, a trajectory optimization framework was created that combined helicopter dynamics and performance, a ship, three wind models of increasing levels of accuracy and a solver to find optimal wind-affected approaches. Trajectories were optimized to be smooth and fast because this is most important for operational purposes. Experiments involved several wind directions, wind speeds and helicopter starting positions, affected by three wind models. This work shows that the created framework functions properly and can be used in a variety of situations. The optimized trajectories were evaluated by the Longest Common SubSequence (LCSS) similarity measure to investigate the effect of both wind direction, speed and model fidelity. With an output between 0 and 1, the LCSS algorithm provided intuitive results and clear trends. A conclusion is that the helicopter wants to exploit the wind as much as possible. It diverts its path to acquire a higher ground speed at the start and a stronger headwind to decelerate at the end of the approach. When introducing a wind gradient, it was observed that the helicopter adjusted its vertical manoeuvre with the same objective. In some wind cases, constraint limits were reached or violated, marking preliminary operational limits. Results were also interpreted with a different perspective to find the best starting positions for the helicopter to approach the vessel in a certain wind condition. These results showed a variety of optimal starting locations, based on the total objective function value, total energy consumption and by distance normalized quantities. Wind model fidelity did not influence this outcome significantly, but it showed that it is important to estimate performance parameters with higher-fidelity models for increased wind speeds. This could also be seen from the downdraft behind the hangar; while the optimized approaches did not deviate geometrically, performance indicators such as the power required were affected significantly.

Due to an exponential growth in the number of shipments of Unmanned Aerial Systems (UAS), the amount of these devices operating in the sky has increased remarkably over the last few years. This led to an increasing number of proximity incidents with manned aircraft. Since these devices share certain airspace with rotorcraft, the question arises how much damage a helicopter could sustain after an impact with a UAS. Within this thesis, a risk assessment was completed initially to determine which collision in terms of type of UAS and helicopter impact location poses the highest risk to the operator of the helicopter. Subsequently a validated model of a DJI Phantom III was developed and impacted onto a rotorcraft windshield in explicit Finite Element software. The sustained damage was compared with a simulated bird strike event to determine whether the prevailing certification requirements would suffice to guarantee safety of the crew.

A propeller has a high propulsive efficiency, yet inherently leaves the air it propels swirling. The efficiency of a propeller can be enhanced by placing it in the tip vortex of a wing. Such a tip-mounted propeller configuration lets the vortex created by the wing and the vortex created by the propeller counteract each other, enhancing the propulsive efficiency of the system. Even though the benefits of such a configuration are clear, the concept is not commercially viable. Among other benefits, electric engines are scalable, light and can be placed in advantageous positions. This allows the engine to be placed at the tip of a wing. The batteries for electric propulsion are heavy, so synergistic effects are needed to improve the efficiency to such an extent that electric propulsion will be commercially viable. Another benefit can be defined by tip-mounted propulsion. As the propeller is mounted at the tip of the wing, the moment arm is large. This could result in a large directional control moment. On the other hand, if one engine is inoperative, the resulting moment is so large that it cannot be compensated by a rudder deflection. Therefore, if a one-engine inoperative situation arises, to still produce thrust both propellers have to be interlinked resulting in a heavy system, or both engines should be switched off. If tip-mounted propellers are used to enhance directional stability and control, the vertical tailplane size can be reduced, resulting in a reduction of mass, drag and hence overall power consumption. In this thesis the contribution of tip-mounted propellers to static stability, dynamic stability, and control is researched, for both positive and negative input power. Negative input power denotes that the propellers are recuperating energy fromthe airflow, and is a state that is applicable when one engine is inoperable. The forces on a tip-mounted pusher propeller are obtained by linking a lifting line wing model and a combined blade-element momentum vortex propeller model. The lifting line model is used to calculate wing-induced velocities on the pusher propeller disk. These induced velocities are used as input for the propeller model, and a resulting thrust and power is obtained. These are corrected for an angle of attack on the propeller disk by empirical relations. The thrust, normal force and power are saved to a 7D dataset. A non-linear flight mechanics model of the Piper Seneca III uses the dataset as lookup table and implements the tip-mounted propeller as forces at the tip locations. Thrust variations in the 7D dataset are parametrically visualised, showing the expected trends. Resulting forces are compared with a rudder deflection, to estimate a potential rudder size reduction. When the aircraft is flying slow, tip-mounted propellers can match the maximum moment produced by the conventional rudder. When flying fast, around half the reference yawing moment can be produced by tip-mounted propellers. The static stability contribution of tip-mounted propellers is visualised parametrically for propeller diameter, advance ratio, blade pitch and a toe-in angle. Negative toe-in angles, hence toe-out angles, prove to greatly enhance the directional static stability. High thrust values greatly enhance longitudinal static stability as the reference aircraft’s wing tips are positioned above the centre of gravity. In the same parametric fashion as the static stability evaluation, the contribution of tip-mounted propellers to dynamic stability is evaluated. The damping factor and natural frequency are obtained for first order motions Dutch roll and the Phugoid by fitting an exponential curve to the time-response of the flight mechanicsmodel. This method succeeds in capturing the motion characteristics, and indicates clear trends: the frequency of the Dutch roll increases with toe-out angles and thrust, and the frequency increases with thrust. The Phugoid’s natural frequency increases with thrust, and damping factor decreases with thrust. An attempt is done to use the curve-fitting method for the second order motion Short period as well, yet proves too inaccurate. A typical tip-mounted propeller design is evaluated to summarise the effects of using tip-mounted propellers for directional stability and control. For this non-optimised design, the static stability is enhanced by 37%. The dynamic stability has increased significantly as well. Maximum blade pitch deflection and maximum rudder deflection result in similar time-history sideslip responses when the aircraft is flying slow, when flying fast the tip-mounted propeller design’s sideslip response is around half the reference rudder deflection response. This conclusion also applies to a one engine inoperative simulation. In this thesis, a significant first step is made toward enhancing directional stability and control with tip-mounted propellers by defining the contribution of tip-mounted propellers in a parametric fashion. The results are directly applicable to an aircraft that has been designed with tip-mounted propellers, yet does not rely on tip-mounted propellers for directional stability and control. A typical design is evaluated in cruise, recuperative and one-engine inoperative cases, proving that from a stability and control point of view the vertical tailplane can be reduced in size. Before tip-mounted propellers can be used for directional stability and control behaviour analysis in the stalled regime, more research has to be conducted. This is left as recommendation.

The Hyperloop is a newly proposed transportation method which caters to the rising demand of high-speed transportation, while adhering to stringent emission requirements. This system comprises pods that are propelled through a partially evacuated tube at velocities of 300 m/s. The low-pressure environment paired with high-subsonic Mach numbers create an unconventional flow regime. This thesis project is an investigation on the aerodynamic characteristics of a Hyperloop pod, whereby an optimization is performed in order to find a pod shape that yields minimum drag. A low-fidelity solver is developed to perform the analysis and optimization. Investigations show a large pressure peak at the nose due to violation of the Kantrowitz limit. Furthermore, a blunt nose paired with a concavity in the tail section yield minimum drag due to the alleviation of the choked flow effect. The solver can readily be embodied into a larger, multi-disciplinary optimization framework.

Flight testing is an activity that exists since the beginning of flight, and is still seen as an essential part of the aircraft development process. While numerical simulation has been improved significantly over the last decade, flight testing remains attractive in the exploration and evaluation of the flight envelope, especially in the region where numerical simulation lacks prediction accuracy. Free-flying model testing is a potential technique, which is recognized by some of the largest research institutes. Using such relatively cheap scale models aids in the determination of the flight behavior of full-scale aircraft in an early stage in the design process. Furthermore it takes less time to develop a scalemodel and is also safer to fly. A 5.5% scale model of the Boeing 737-700 is created by the TU Delft as a first step towards investigating the potential of dynamically scaled flight testing. This Delft University Unconventional Concept (DUUC) has a conventional tube-wing configuration and features ducted fan engines mounted aft on the fuselage, which replace the conventional empennage. A horizontal and vertical jet vane is placed in the duct, which guide the propeller slipstream and thereby control the attitude of the aircraft. Successful flights have already been performed with this model, which proves the propulsive empennage concept. However, the stability and control behavior has only been assessed at a low level. Flow characteristics entailed by the ducted fan are accounted for by means of approximate functions and empirical relations instead of looking at the physical interaction between the components within the duct. This study focusses on the processing of said interaction by performing a CFD study of which the results are used in the longitudinal equations of motion of the DUUC. This way, certain motion can be simulated from which the effect of the unconventional empennage on the stability and control can be assessed. In order to study the aerodynamics of the propulsive empennage and subsequently its stability, a CADmodel is developed using PARAPY. This is a knowledge based engineering platform written in the Python language and allows for parametrization of the model such that geometric alterations can easily be implemented. Previous studies within the TU Delft have lead to a multi-model generator written in PARAPY. The fuselage and wing generation modules that were developed can readily be applied in the generation of the DUUC model. The propulsive empennage module is created by the author of this thesis, consisting of several sub-parts: (1) outer duct that forms a shielding around the propeller, (2) the pylon that connects the duct to the fuselage, (3) a center body to which the (4) propeller and (5) control vanes are attached. The full aircraft model has been used in a series of CFD simulations with ANSYS FLUENT. Inviscid steady calculations are performed using a pressure-based solver with a SIMPLE pressure-velocity coupling scheme. The propeller is modeled as an actuator disk whereby the thrust is defined by specifying a pressure jump across the thin surface. The thrust produced by the ducted fan is based on the turboprop installed on the ATR72-600 aircraft, which has similar dimensions compared to the Boeing 737-700. Both the full-scaleDUUC as well as the 5.5% scale model are subjected to this aerodynamic analysis. Minor discrepancies were found between the two models, which is a result of the artificial viscosity that is implemented in the Euler scheme to smoothen strong gradients in the solution (numerical dissipation). Due to the location of the engine, the thrust line is located above the center of gravity which contributes to a stabilizing effect. The effect of several parameters on the stability and control has been analysed, such as the center of gravity location, mass and inertia, and geometric scaling factor. The slight difference in aerodynamic performance between the full-scale and subscalemodels, means that the trimmed solution for steady horizontal flight is also slightly different with a maximum error of 2.5 degrees in elevator deflection. More drag is obtained as the aircraft scale goes down, resulting in a higher required thrust to achieve force balance in a trimmed flight condition. Furthermore it is found that by scaling the aircraft down according to Froude scaling theory, the response becomes much faster. This response can in turn be scaled back, which proved to be a very useful estimate of the full-scale simulation.

The objective of this research is to determine the impact of design variables on power output of the Makani Power Wing7 airborne wind turbine. This system consists of a rigid wing connected to the ground using a using a number of bridles and a tether. The tethered wing flies crosswind trajectories and generates power using on-board turbines. Sensitivities of power output to design variables are required for various design trade-offs. A simulation and optimization approach is presented which allows analysis of a fairly complex model with realistic controls and constraints. Using trajectory optimization removes the assumption of a predefined trajectory and allows analysis of the impact of the flightpath itself. The wing is modeled as a rigid body with six degrees of freedom. Aerodynamic forces are determined using a response surface on results of a vortex lattice code. A time-varying position of the bridle attachment point couples the wing to the tether. This tether is implemented as a straight elastic element with analytic approximations for the effects of mass and aerodynamic drag. The power system model consists of a turbine response surface and DC-equivalent generator model. Optimal trajectories are determined using the direct collocation method resulting in a capacity factor of 48.1% for a site with uniform wind field and annual mean wind speed of 7.5 m/s. The relative impact of aerodynamic lift and drag on long term averaged power output are found to be an order magnitude more important than wing mass. Topology and circularity of the flight path are found to have a low impact on power.