Since the 1970s, helicopters have been vital in disaster response but face limitations in cost, infrastructure, and
maneuverability. This thesis presents the design and optimization of an emergency response flyer tailored for the
GoAERO competition. Multirotor configurations with hybrid-electric propulsion are investigated to overcome
the limitations of existing fully electric VTOL technologies.

A Multidisciplinary Design Optimization (MDO) framework is applied to hybrid-electric quadrotor, hexarotor,
and octorotor configurations, optimizing the balance between rotor count, mass, and performance. The objec-
tive is to minimize Maximum Takeoff Mass (MTOM) while enhancing dynamic performance and maximizing
the payload-to-system mass ratio. This study addresses a key research gap by integrating early-stage handling
qualities (HQ) evaluation and exploring trade-offs between optimized rotor count configurations. Aerodynamic
forces and energy consumption are estimated using momentum theory, while system dynamics are analyzed
through Newton-Euler equations and eigenvalue assessments.

Results show that the hexarotor configuration achieves the fastest convergence, balancing design complexity and
design space exploring. Configurations maintain a disk loading between 43–63[kg/m2] with hover efficiency
between 5 and 5.8. A higher rotor count improves hover efficiency and disk loading, making performance com-
parable to eHang and Vahana while achieving nearly twice the cruise speed, rivaling helicopters.

At a hybridization factor (HF) of 0.1, MTOM is reduced by 75%, with only a 3% mass variation between con-
figurations. However, at higher HF, mass increases by 20% due to relatively low energy density of batteries
further impacting structural support demands, underscoring the need for a more detailed support structure model.
Stability analysis confirms neutral hover stability, while a real, negative eigenvalue at cruise identifies the surge
subsidence mode, governed by system mass.

Rotor count significantly impacts design flexibility. Hexacopters and octocopters offer better disk loading homo-
geneity, whereas quadrotors face constrained rotor sizing and elevated blade and disk loading, limiting efficiency.
Quadrotors excel in payload-to-mass ratio and simplicity, making them ideal for productivity missions but less
suited for maneuvering-intensive tasks with lower disk loading and control authority, highlighting the importance
of early HQ considerations.

This thesis makes a valuable contribution to the advancement of eVTOL research by addressing early-stage HQ
assessments where on the basis of other literature and configuration optimization, the hexacopter emerges as the
most viable for the GoAERO competition, striking the best balance between mass, handling qualities, and mission
performance.

This work explores a paradigm in which isolated aircraft components are analyzed separately and combined together in a multi-body system representative of the whole geometry. The FLAPERON (FLight mechanics Analysis and PERformance OptimizatioN) toolbox is developed and employed to assess the impact of vortex-filament-based aerodynamic interactions on the simulated aircraft's response when considering aerodynamic data only at the component level. Physical networks created in Simscape are used to simulate symmetrical flight and assess key stability characteristics of a configuration including a main wing, a horizontal stabilizer, and a vertical stabilizer. Vortex filaments are modeled for the main wing and the horizontal stabilizer. The introduced aerodynamic interactions change the simulated response of the aircraft in accordance with predictions. This work suggests that multi-body analysis of flying qualities is possible based on the data prescribed at the component level.

Strategic airlift is an essential capability for the rapid global movement of cargo, particularly in crisis operations where timelines are short and cargo demands extreme. Despite the European Union's collective purchase of A400M aircraft, capability gaps remain due to the aircraft's limited ability to airlift heavy and outsized equipment. This study applies Knowledge-Based Engineering aircraft design tools in conjunction with Agent-Based Simulation techniques to evaluate a fleet's ability to move cargo rapidly across strategic distances in high-stakes operational scenarios. One focus of the study is on the often-overlooked constraint of cargo hold volume and its effects on a fleet's ability to transport cargo. The study found that this volume constraint can reduce airlift capacity by roughly 20% in scenarios with medium-density cargo. Further, through design space exploration, this study identifies key top-level aircraft requirements for a new airlifter to work effectively in the European fleet of airlifters. Analysis reveals that a next-generation aircraft requires a wide fuselage capable of double-file loading, an extended fuselage length of 39m, an increased payload capacity of 120 tons, and a cruise speed of Mach 0.8. Such a design could enhance the fleet performance and reduce fleet requirements by roughly 30%.

In order to decarbonize the industry, green hydrogen production will need to be increased. An option for green hydrogen production is to use electrolysers and wind energy in an offshore location. This thesis aims to improve the design of offshore wind based hydrogen production by optimizing the design with the use of Multidisciplinary Design Optimization. The question is answered with the use of a modular design including desalination, hydrogen production, hydrogen compression and transportation with a hydrogen pipeline. The main conclusion from this thesis is that the design problem included non-linearities. The complex optimization problem could be solved by using a sequential differential evolution algorithm. The resulting optimized design showed that optimizing the pressure of the electrolyser could result in lower work requirements for the compressor and desalination and increasing hydrogen production.

The field of floating offshore wind energy is rapidly advancing, offering a promising solution to
harness stronger and more consistent wind resources in deep-water regions, where conventional bottom-fixed turbines are not viable. Floating Offshore Wind Turbines (FOWTs), mounted on floating substructures, enable the deployment of wind turbines in deep offshore locations without the need for extensive foundations. This approach can significantly lower project costs, primarily by reducing substructure procurement expenses for comparable water depths. As a result, the installed capacity of FOWTs is projected to reach approximately 18.9 GW by 2030.

However, the design of cost-efficient FOWTs presents significant challenges due to the complex interactions between aerodynamic and hydrodynamic loads, as well as the coupling of various subsystems. One of the key hurdles is reducing the Levelized Cost of Energy (LCoE) to ensure the economic viability of Floating Offshore Wind Farms (FOWFs). Additionally, the flexibility of the floating substructure, which moves in six degrees of freedom (DOF), introduces complexities in the wake profile, such as enhanced wake meandering, which may affect the wake losses and the overall farm energy production.

Despite the potential impact of floater movements on energy yield, the specific effects on optimal wind farm layout design remain under-explored. Furthermore, the impact of these displacements on the LCoE needs to be examined to determine whether incorporating floater displacements into optimization frameworks leads to more accurate results or merely adds unnecessary complexity and computational cost.

This thesis evaluates the role of static floater displacements, specifically tilt and surge, in the optimization of FOWFs. Two distinct scenarios have been compared to assess how these displacements affect energy yield, the LCoE, and the optimal wind farm layout. The first scenario (Case A) disregards the static equilibrium displacements of the floating turbines, while the second scenario (Case B) incorporates these displacements into the analysis. To conduct the analysis, this thesis develops a wake modeling strategy focusing on wind-induced floater displacements, wherein the tilt and surge displacements of the floater are computed for each turbine using the PyWake framework, based on the effective wind speed experienced by its rotor. This wake modeling approach is then integrated into an OpenMDAO-based optimization framework to minimize the LCoE of the wind farm, which is used for the comparison between the two cases, to achieve the objectives of this study.

A case study of a 42-turbine sample wind farm in the North Sea, arranged in a rectangular gridded layout, was analyzed using the optimization framework. The results showed minimal differences in AEP, LCoE, and layout design between the scenarios that account for floater displacements (Case B) and those that neglect them (Case A). However, the computational time required for the optimization process increased by approximately fourfold for Case B. Case B resulted in a 0.25% reduction in AEP and a 0.162 €/MWh increase in LCoE, primarily due to changes in wake behavior caused by tilt and surge displacements. The optimal layout also shifted in orientation and spacing, with Case B yielding slightly lower power in the final configuration. Despite these effects, the overall impact on the LCoE was modest, suggesting that while incorporating floater displacements could potentially improve the accuracy of results for FOWFs, it might not justify the added computational costs for larger wind farms.

Hydrogen is seen as a potential energy carrier for the next generation of aircraft that will be more climate-friendly than the previous generation of kerosene-powered aircraft. Two types of hydrogen-based propulsion systems are currently foreseen for such aircraft: hydrogen combustion and hydrogen fuel cell. In addition to producing useful electrical power, fuel cell systems produce a considerable amount of heat which must be removed to ensure the continued and efficient operation of the fuel cell stack. This thesis presents a thermal management system sizing methodology for propulsive fuel cell systems onboard CS-23 commuter aircraft. The developed methodology is implemented into an aircraft sizing environment to study the characteristics of air-based thermal management systems and their effects on aircraft design and aircraft performance. The results show that the thermal management system, through its additional mass, parasitic drag and parasitic power, has both a direct and indirect effect on aircraft performance. In addition to the conventional thermal management system, an unconventional system using nanofluids is studied. The use of nanofluids showed no considerable improvement in both system and aircraft level performance when compared to the base fluid. This thesis shows the importance of considering the design of thermal management systems during the conceptual design of fuel cell aircraft.

Floating offshore wind turbines (FOWTs) unlock the potential to harness energy from wind in deeper waters. Despite their potential, the major obstacle to large-scale commercial deployment remains the floating substructure's high cost. Multidisciplinary design, analysis and optimisation techniques are commonly employed to improve their cost-competitiveness, but existing models often use simplified engineering models. This approach risks neglecting design considerations typical of structures subjected to complex aero-hydro-servo-elastic loads.

To address the need for incorporating higher-fidelity analysis methods, an optimisation framework is developed, integrating OpenFAST to simulate the response of the FOWT system under various environmental and operational conditions. Leveraging the flexibility of the Python framework and the wealth of output data contained within the OpenFAST simulation results, this holistic approach offers opportunities to explore novel and cost-effective platform designs with high reliability.

To demonstrate its effectiveness, the optimisation framework is utilised to achieve a significant reduction of the DeepCWind platform's structural mass. Among the considered constraints, the platform pitch motion was critical, reaching maxima for design load cases characterised by the most extreme wind and waves. Although the inclusion of a structural model for the platform comes at considerable computational expense, it enhances the framework's value, as structural integrity can be verified.

The recommended use of the optimisation framework is for in-depth studies, following preliminary design explorations conducted with cheaper models. Future efforts should focus on extending the structural and hydrodynamic model to improve the framework's versatility, and make it applicable to a wider range of platform concepts and turbine sizes.

Boundary Layer Ingestion (BLI) is a promising propulsion concept for aviation, aiming to reduce fuel burn. This configuration involves using the propulsor to ingest the boundary layer from the fuselage or wing. Typically, aircraft with BLI propulsors also integrate a hybrid-electric powertrain. This integrated setup has shown potential in fuel burn reduction. This thesis investigates the interactive effects of BLI-induced power-saving benefits and aircraft design parameters on overall performance, focusing on a fuselage tail-mounted BLI propeller.

The thesis has three primary objectives. First, it seeks to enhance the fidelity of the existing BLI model within a conceptual aircraft design tool. The improvement involves transitioning from the actuator disk theory to the blade element theory (BET) with gradient-based optimization. Additionally, a surrogate model is established with this improvement through multidisciplinary design optimization (MDO), design of experiment (DoE), and response surface methodology (RSM) to predict power-saving benefits based on fuselage geometric and operational parameters. Comparison reveals discrepancies between the existing BLI model and the surrogate model, emphasizing the influence of blade aerodynamics.

The second and third objectives delve into the sensitivity of aircraft-level performance and powertrain settings. The conceptual aircraft design tool, Aircraft Design Initiator (Initiator), is used for sizing, with the surrogate model integrated. The study uses a regional turboprop ATR-72 as a reference conventional aircraft design and employs a partial-turboelectric (PTE) architecture for the hybrid-electric powertrain in the radical aircraft design. A sensitivity analysis varying design parameters by 20%, including fuselage slenderness ratio, propeller size ratio, and shaft-power ratio, reveals their impact on BLI effects and aircraft-level performance.

The study reveals that fuselage length significantly impacts fuel weight and, consequently, aircraft performance. Surprisingly, aero-propulsive benefits from BLI do not directly enhance overall aircraft performance, attributed to an associated weight penalty. Instead, the shaft-power ratio and propeller size ratio prove significant at the system level. Further investigation into powertrain settings suggests that radical BLI-equipped aircraft designs are not able to surpass the energy efficiency of conventional counterparts. Additionally, the proposed surrogate model exhibits a limited applicable range, especially under high BLI propeller disk loading, rooted in underlying physical constraints in propeller design. These findings prompt a critical examination of the feasibility of hybrid-electric powertrains with BLI for regional turboprop aircraft, with a note of caution regarding potential variations in modeling methods and assumptions.

Interest grows rapidly in electric and hybrid electric aircraft. To determine the optimal performance and energy management required with such novel powertrain configurations, a knowledge-based aircraft and powertrain performance model is developed. The model is then used to set up an optimal control problem, which is transcribed to a non-linear programming problem using global orthogonal Legendre-Gauss-Radau collocation for single phase problems, and Hermite-Simpson local collocation for multiphase problems. The solution to the control problem allows identification of the best control strategies and energy management strategies. A case study is performed on the HY4 hybrid fuel cell aircraft and the hybrid electric Pipistrel Panthera. Solutions show that for best fuel economy, flying at a minimum drag airspeed, and keeping a constant power setting, proved more important than the choice of altitude. This was more noticeable for the HY4, with its relatively low power available and good aerodynamic properties following from its glider-based airframe.
The Fuel-optimal energy management strategies proved identical for both aircraft investigated. Batteries are used to provide a power boost during takeoff, after which batteries are discharged gradually throughout the remainder of the flight to maximize discharge efficiency. The engine or fuel cell are kept at approximately constant cruise power settings throughout the flight. The Panthera showed
consistent flight profiles with increasing range. For the HY4, however, achieved airspeeds reduced with increasing range, and additional measures were required to force a climb to non-zero altitudes due to its under-powered nature. The fuel-optimal trajectories offered an average of 10-15% of possible fuel
savings, depending mostly on the size of the onboard batteries. Fuel savings increased significantly at low ranges300km, where the contributions of the batteries have more impact.
Comparing different transcription methods and problem setups, it was concluded that global orthogonal, or pseudo-spectral, methods like Legendre-gauss-Radau collocation are not only faster, but also more consistent compared to simpler direct collocation methods. However, if the problem complexity increases and the performance limits of the aircraft are pushed, switching to a simpler method like Hermite-Simpson collocation reduced the time required to find a solution, with negligible differences in the resulting trajectories. Opting for a multiphase problem set-up, essentially splitting the problem in a series of individual subproblems, appeared less advantageous. While offering more control over the trajectories, time required to find solutions increased drastically, and offered no additional insight into the best energy management strategies.

Zero-carbon-dioxide-emitting hydrogen-powered aircraft have, in recent decades, come back on the stage as promising protagonists in the fight against global warming. Nevertheless, most recent studies agree that hydrogen aircraft would underperform their kerosene counterparts in terms of operative empty mass and specific energy consumption. The main cause for the drop in performance lays in the fuel storage, as not only the liquid hydrogen has to be kept in cryogenic conditions and pressurised, but for the same energy content, it has four times the volume of kerosene. The inevitable consequences are an increase in fuselage size, which adds mass and drag to the aircraft, and the addition of an heavy fuel storage and distribution system. On the other side, hydrogen has 2.8 times higher specific energy, and the consequent reduction in fuel mass could balance the previously mentioned drawbacks. Literature on the topic shows that the optimal fuel storage solution depends on the aircraft mission, but most studies disagree on what solutions are optimal for each aircraft range category.The objective of this research was to identify and compare possible solutions to the integration of the hydrogen fuel containment system on short, medium and long-range airliners. The capabilities of an automated synthesis program for CS-25 aircraft have been expanded with validated structural and thermodynamic physics-based tank design models, to allow for the design and analysis of liquid hydrogen aircraft. Studies were performed on several design options. The effect of using an integral tank structure was found to be negligible for short-range aircraft, but increasingly more beneficial for medium and long-range aircraft. The effect of increasing the fuselage diameter was found to be favourable, especially when seats abreast could be added without the addition of one aisle. The effect of using a combination of an aft and a forward tank was found to be detrimental in terms of operational empty mass, beneficial in terms of specific energy consumption and negligible in terms of maximum take-off mass. The use of spherical tanks was found to be slightly beneficial, but only when compared to a non-spherical tank version using the same tank layout, non-integral tank structure, and same cabin layout. The study on the venting pressure revealed that with increasing aircraft size the optimal venting pressure in terms of main aircraft performance decreases whereas the sensitivity to those same parameters to the choice of venting pressure increases. The use of direct gas venting as a means to contain the pressure rise did not appear to provide significant performance improvements. The optimal designs, in terms of operational empty mass, maximum take-off mass and specific energy consumption, feature increased fuselage diameters, the use of the aft & forward tank layout, non-spherical tanks and no direct venting. The short-range aircraft uses non-integral tanks and high venting pressure, while the medium and the long-range aircraft benefit from an integral tank structure and a lower venting pressure. Nevertheless, the sensitivity to these design choices is not significant, meaning that with a different set of assumptions and/or requirements different design choices may become optimal. The overall best performing LH2 aircraft for the short, medium and long-range categories were found to have respectively 8%, 24% and 22% higher operative empty mass, -2%, 1% and -5% higher maximum take-off mass and 5%, 13% and 5% higher specific energy consumption than their kerosene versions.

The potential gain in energy production and profit by improving the placements of turbines within a wind farm is driving interest. However, finding the optimal placements provides a complex problem. A large number of inter-dependent design variables create a design space that is difficult to solve. Therefore there is much attention for offshore wind farm layout optimisation (OWFLO) in practice and literature. Most of the research is done in selecting and creating the best optimisation algorithms, wake models and cost models.

This is not yet another study into better modelling or optimiser selection for OWFLO. Instead, this study aims to provide insight into what performance can be expected from OWFLO and to know when further optimising is not justifiable anymore. The study consists of three parts. All three parts make use of a referent. A referent can be considered a close representation of reality, obtained by a best-practice implementation of the optimisation problem and its associated models. It is assumed that the referent has the same characteristics as reality and that deviations of other implementations of OWFLO from the referent are representative of their deviations from the true optimisation problem.\\

In this study, the referent is defined by, amongst others, the use of the Bastankhah and Porté-Agel Gaussian wake model, a 12 sector wind rose with a Weibull distribution per sector and the gradient-free covariance matrix adaptation evolution strategy. The referent is used to maximise annual energy production (AEP).

The first part uses the referent to find and understand the characteristics of the OWFLO problem. Wind farms with 9, 25 and 64 turbines have been optimised 100 times with the referent. The results show a small spread in the performance of the found optimised layouts, indicating that many local optima exist with similar performances in an OWFLO problem. The spread between the highest and lowest found performance decreases with increasing numbers of turbines. A special form of the response surface is used to visualise the response surface. The visualised response surfaces, with only two design variables, showed that the wakes of the turbines created multiple local optima.

The second part compares performances from optimised layouts with 25 turbines resulting from optimisations with alternative implementation choices, evaluated by the referent model. The performances are represented in boxplots for 100 optima each. The boxplots show that the influence of alternative implementation choices depends on the slightly different locations of the local optima in the design space and the roughness of the response surface they create. The influence of the shifts in locations of the local optima on the performance turned out to be minimal. An increase in the roughness of the response surface meant an increase in the spread of the performances. The difference in performance resulting from the alternative optimisers indicates that improvement of a state-of-the-art optimiser is not expected to lead to much better results.

The third part explores the need for improvement of the analysis by adding a phenomena currently not considered in OWFLO. The influence of neighbouring wind farms on layout optimisation without including atmospheric stability is explored. Three cases have been defined to show the influence of neighbouring wind farms on layout optimisation. It is concluded that adding neighbouring wind farms for accurate energy yield assessments is necessary. However, for layout optimisation, the benefit of including neighbouring wind farms is not evident.

The commercialization of the space industry has led to a reduction in size and weight of satellites and launching vehicles, which have effectively reduced the cost of space services. The costs of launching payloads to space can be significantly reduced when the launching vehicles are reusable. The two-stage-to-orbit system with a winged, reusable first stage vehicle, is deemed to offer benefits in terms of operations, as it can take-off and land from a runway.
Dawn Aerospace is pursuing development of the winged semi-Reusable Launching Vehicle with horizontal take-off and landing capabilities in the Mk-III concept. In the previous work on this concept, the aerodynamic design has not been addressed. It is important that the aerodynamic design is already considered in the conceptual design, as the large variations in flight conditions during the mission pose conflicting requirements on the aerodynamic design.
A performance analysis model of the launching vehicle was developed, in which the aerodynamic discipline is integrated. Using the developed model, sensitivity analyses and case studies were performed to investigate the impact of design changes on the mission performance. These results indicate that the limited gliding range of the first stage vehicle influences the propellant mass fraction of the upper stage.
The performed case studies indicate how the propellant mass fraction of the upper stage can be influenced, by changes to the vehicle design. Analysis of an alternative wing concept that improves the gliding performance of the first stage vehicle shows that the propellant mass fraction of the upper stage vehicle can be reduced from 91.5% to 90.3%. This can be achieved as the improved gliding range allows to reduce the delta-V delivered by the upper stage, and a less steep ascent trajectory that results in 8.9% less gravity losses. Analysis of a changed fuselage configuration indicates a reduction of propellant mass fraction from 91.5% to 90.4%.
Also changes to the trajectory design were analyzed, and by either reversing the direction of the take-off maneuver or by reserving propellant for the return trajectory, the propellant mass fraction can be reduced. The reductions achieved in the case studies were 0.5% for the reversed take-off direction, and 1.2% for the propelled return trajectory.

Knowledge Based Engineering (KBE) applications mainly reduce the lead-time in engineering design projects by translating product and process knowledge into application code. The problem with KBE applications is that they produce an output from some input, but it is unclear how it came to its conclusions. There are existing KBE methodologies such as MOKA that proposes a few models to help understand what the KBE application is doing, but these models are disconnected from the application code: there is no traceability of knowledge onto application code. Moreover, MOKA requires specialists which are often not available; this hinder adoption of the methodology. Therefore , this thesis proposes a new ontology that explains how to structure knowledge without specialists, and defines how that knowledge is connected to application code. Moreover, a platform has been developed which incorporates the new ontology, and enables users to structure knowledge and connect it to code.

This thesis work proposes an approach to integrate design and reliability assessment, based on a single modeling environment by deployment of Systems Modeling Language (SysML). The main purpose of the developed approach is to help enhance reliability assessment in student-based CubeSat projects. Considering the limited project resources, that CubeSat university design teams typically have to cope with, an attempt is made to create a methodology, that allows adoption of single modeling environment for both system design and reliability analysis, thereby focusing on the main principles and advantages offered by the Model-Based Systems Engineering (MBSE) practice. To develop the considered methodology and to demonstrate its practical application the following steps were taken: A SysML design model is built, consisting of both functional and physical architectures, based on a hypothetical simplified spacecraft subsystem. Thereby an assessment is made to what detail a system needs to be modeled and which characteristics it should at least comprise to provide a sufficient basis for a risk model, as a choice of a certain risk assessment methodology may influence the extent to which a system must be modeled, while certain system design model characteristics influence the selection of the appropriate risk assessment methods to be implemented. To determine how risk analysis can be performed in SysML for a given hypothetical design problem, various risk assessment methods were considered for the sake of risk assessment methodology development, based on specific criteria. After it became clear how the implementation of both qualitative and quantitative parts of risk assessment had to be realized in SysML, the actual risk analysis was initiated; the design model was extended by a reliability model. The evaluation on the obtained results was finally performed, and general observations from integrating risk analysis in MBSE were presented, based on the comparison with traditional methods, considering the major risk assessment aspects.

Airborne wind energy (AWE) is a new technology aiming at converting wind energy by flying crosswind patterns with a tethered aircraft. One of the main challenges of this technology is the launching and retrieving of the aircraft. A promising solution is the use of a vertical take-off and landing (VTOL) system in the form of multiple electrically driven rotors. Contrary to other approaches, such as a rotational and catapult assisted take-off, no detailed studies on a VTOL system for AWE have been conducted so far. The goal of this research is to investigate the opportunities and limitations of a VTOL system as a take-off system for a rigid-wing AWE system (AWES), by designing and simulating a VTOL system for the AP2, an AWES prototype of Ampyx Power B.V.

The main research question to be answered by this research is how such a VTOL system can be designed. After having conducted a thorough state-of-the-art analysis (aka. literature study) the main research questions remain and are refined as: 1. What VTOL concept is most suitable for AWE applications? and 2. How do the aerodynamic forces of the AWES effect the VTOL system design? These are addressed and thoroughly analyzed in this report.

The proposed and applied design methodology is based on the mass estimation of the VTOL system and its components: motors, battery and rotors. The sizing of the motors and battery is done by calculating the power and energy demand during take-off. Rotor mass is estimated using a statistical model. To calculate the required power, a blade element momentum model (BEM) combined with generalized momentum theory (MT) is used considering both inflow velocity and angle. A flight mechanics model is derived to calculate the required thrust and aircraft attitude. This model considers propulsion, gravity, and aerodynamic forces.

A multi-disciplinary optimization (MDO) framework is developed to ensure consistency between the above-mentioned models and to calculate the minimum VTOL system mass for certain wind and operating conditions. A Simulink model of the VTOL system is developed using a multicopter flight path controller and a 2D dynamic model. This simulation model serves as a dynamic feasibility check on the VTOL system design and is used to iterate on assumptions taken in the design model.
One of the main findings of this research is that by tilting the rotor depending on wind and flight conditions the minimum VTOL system mass is obtained. The VTOL system mass is estimated at 4.3 kg at wind speeds below 4 m/s and decreases to a mass of 2.1 kg at 10 m/s wind speed. However, for a fixed rotor tilt of -30 degrees (knee-sitter concept, newly introduced in this report), the VTOL system mass is only 100 grams higher for speeds between 5 and 10 m/s. Because a fixed rotor does not require any tilting mechanism, it can be concluded that this concept is most optimal in terms of mass for a direct take-off approach. For the tail-sitter and quad-plane concepts, the VTOL system mass increases with wind speed.

A dynamic simulation has proved the feasibility of the sizing results for the tail-sitter, quad-plane and the new knee-sitter concept for a wind speed of 5 m/s and 10 m/s and a target elevation angle of 41.8 degrees. These simulations have shown that, under the assumptions of the simulation, the maximum motor power (from sizing model) is sufficient to successfully fulfill the take-off phase. It is found that the maximum motor power is only used to accelerate the rotor initially. It is not required in the transient flight phases. Furthermore, it is found that the additional power and energy, required for acceleration and transient phases is sufficiently low compared to the safety factor of 1.5 which has been taken into account in the preliminary sizing model.

In this paper an adaptive version of the incremental nonlinear control allocation (INCA), which is able to account for sudden changes in the aerodynamic configuration of an aircraft, is investigated. The controller is designed for the highly maneuverable and tailless innovative control effectors (ICE) aircraft, which has a control suite of 13 nonlinear, interacting and axis-coupled effectors. The least mean squares (LMS) method is used to estimate a delta control effectiveness Jacobian (CEJ) based on the difference between the expected and measured accelerations of the aircraft. This delta CEJ model is then added to the onboard spline CEJ model to achieve fault tolerance. By keeping the nominal spline model intact the nonlinearities and interactions of the effectors remain modeled, while the LMS estimator allows for fast adaptation. Simulations for four different maneuvers and failure cases showed that the estimator is able to stabilize the aircraft for the most demanding maneuver. For two less demanding maneuvers the adaptive controller greatly reduced the control effort while keeping the tracking error similar to the non-adaptive controller. For the remaining fourth maneuver, which operates in a flight region with the most significant interactions and nonlinearities, the adaptive controller had a reduced performance compared to the nonadaptive controller. A sensitivity analysis showed that the choice of design parameters greatly influences the results, and no general set of best performing parameters was found.

With Multidisciplinary Design Analysis and Optimization (MDAO) a fully automated aircraft design analysis is set up and optimization algorithms are used to obtain better designs by balancing the synergy between components. In the EU project AGILE, a new methodology and framework were developed to make the MDAO approach more accessible to industry. A key component of this framework is the KADMOS package. KADMOS is used to formulate large, heterogeneous MDAO problems and their execution process before they are implemented as executable workflows. This thesis focuses on the automation of a key step in the problem formulation for MDAO systems: the execution process definition, i.e. the order and grouping of the disciplines. Several sequencing and decomposition algorithms are developed to optimize the execution order of the disciplines and their division over multiple processors for parallel execution. The algorithms are verified and validated on thousands of MDAO systems using a scalable mathematical test case. Furthermore, the conceptual design of a conventional aircraft is performed using a novel implementation of the Initiator toolbox in KADMOS to test the algorithms in a realistic aircraft design problem. This showed that the algorithms resulted in a setup time reduction due to the automation of the execution process formulation and a reduced convergence time thanks to the improved usage of computational resources.

The application of stability checks in simulated offshore wind structures is performed through tools that are established in the offshore wind industry. In particular, the structure should fulfill certain strength and fatigue criteria among which Fatigue Limit States (FLSs) checks are critical. In terms of the process, fatigue assessment can be carried out in both time (TD) and frequency domain (FD), with the former being more popular in the offshore wind energy sector. Nevertheless, simplified tools in the FD have been suggested, since they yield results similar to those of the TD analysis. In order to decide upon the choice of tool in performing the FLS estimations, a relative comparison should be implemented. Particularly, fatigue assessment in the TD, fatigue assessment in the FD and a simplified type of fatigue assessment in the FD are examined. These types of fatigue assessment are conducted in three respective tools, with the TD type conducted in NREL’s FAST v8 and both the FD types simulated within MATLAB tools. The tools are judged upon the desirable levels of Modelling & Simulation (M&S) fidelity. A set of criteria are defined for the particular use case, in an attempt to express that fidelity. The criteria’s metrics are additionally provided in the proposed methodology and associated measurements are taken during simulations. Only after conducting further multi-criteria decision analyses (MCDA), the eventual levels of fidelity for the three types of fatigue assessment result to a consequent ranking among the tools. Therefore, the measured criteria lead to the quantification of these levels of fidelity for all three tools and the application of MCDA results to their ranking. The proposed fidelity framework is applied in a case study in order to evaluate the proposed methodology, as well as to select the type of fatigue assessment and consequent tool that should be used within an early design stage. The results indicate that the simplified fatigue assessment in the FD should be preferred over conventional fatigue assessment in both TD & FD. In addition, the criteria included in the fidelity framework seem to provide a multifaceted approach, since none of the tools is favored in all categories. Finally, similarities in results between relevant types of conducted comparisons as well as between different types of MCDA, enhance the consistency of the proposed fidelity methodology and increase its credibility.