The increasing reliance on space infrastructure and its rapid expansion necessitate the development and enhancement of tools for space debris and fragmentation research. Accurate prediction of the risks associated with satellite fragmentation requires comprehensive understanding of the dynamics involved. To address this need, the widely used NASA Standard Breakup Model (SBM) is employed in this thesis to predict fragment characteristics resulting from breakup events. Additionally, a novel method is introduced to determine the direction of these fragments, something not directly covered by the SBM. Furthermore, the principle of kinetic gas theory is applied to calculate the overall, long-term collision risk between debris and a predetermined satellite population. The results from this reveal the limitations of the SBM in accurately simulating fragmentations for certain satellite types. However, the newly implemented fragment directionality method aligns well with observed data, suggesting its potential for further research. Similarly, the risk model exhibits strong correspondence with ESA's MASTER, a model used for assessing collision risks with debris, with the deviations likely due to different impact velocity models used. Finally, the validated fragmentation and risk models are combined, and the combined model is used to analyse a real-world fragmentation event.

Noise generation from underwater activities propagates into the marine environment.For marine vessels the propulsion system generates the most noise during itsoperations. Naval vessels that want to operate without being detected want to controlthe sound generating properties of the vessel. To control the sound generatingproperties this project has been looking into the existing propeller of the submergedcraft Carrier Seal that is produced by James Fisher Defense. Then a new and bespokenpropeller has been developed with theories applied to minimize its noise generatingproperties. The properties of the propeller that have been altered is the number ofblades, blade area ratio, pitch and skew angle. These properties have been alteredwith aid of the open-source software for Matlab named Openprop. From the finalpropeller design a prototype was later produced, tested and compared to the existingpropeller of the Seal Carrier. To test and compare these two propellers a test procedurewith inspiration from NATO and the Swedish Defense and Research Agency (FOI) wasdeveloped. The results from the comparison show that the sound pressure level fromthe propeller spectrum could be lowered with 3 dB re 1 μP a for the vessels design speedand several blade tones could be eliminated entirely. Simultaneously the efficiency ofthe vessel is increased throughout its speed range.In conclusions the recommendation to JFD is to change their existing propeller tothis bespoken propeller as it has proven itself to better in every way during thesetrials.

Space surveillance and tracking is paramount to enable collision avoidance alert systems and avoid fragmentation events and the consequent generation of debris. This thesis work was performed within the framework of the EU SST, a network of sensors and processing capabilities of the European Union dedicated to space tracking. Using tools developed at CNES, a performance analysis of a correlation assessment algorithm based on the Lambert’s problem was carried out. The algorithm was tested on a simulated population orbiting the GEO region using different dynamical models. The performance of the algorithm was also tested for varying values of the sensor noise. A modification to the algorithm accounting for orbit perturbations was proposed and tested, showing improved results under certain conditions. Finally, the catalogue initialization capabilities of the algorithm were assessed in terms of correlation assessment and orbit determination accuracy by testing it on real data collected by the TAROT network of telescopes.

Satellite constellations intended for communications services are becoming increasingly relevant with multiple companies such as Starlink and OneWeb launching constellations consisting of hundreds or thousands of satellites. This thesis investigated how such a constellation can be designed for a small user terminal with a diameter of approximately 15 cm. Four constellations, two at 8 500 km altitude and two at 1 200 km altitude, were proposed. Methods for systematic placement of satellites in orbital planes, aspects going into the link budget, and relevant regulations on the international level were investigated. It was found that the most favourable constellation was a medium Earth orbit constellation with a minimum elevation of 30°. The primary reason for this choice was the limited budget which did not allow for a large number of satellites being launched. Finally, the concept of a hybrid constellation with both geostationary satellites and non-geostationary satellites was considered.

In today's procedures of bus development in Scania CV, physical tests are the most common and reliable source of confirmation for new concepts. As of now, the majority of the physical tests are conducted in various places around the globe such as Spain, Brazil, and Sweden in order to subject the buses to various climates and environments. Naturally, these tests around the globe demand a lot of resources and are very time-consuming leading the bus development department to look for alternative ways of confirmation for these tests. An alternative to testing is in the eld of Computational Fluid Dynamics (CFD), by using 3D models to simulate in order to save resources and time. Today, the method of simulating using CFD is becoming more frequent in the development phase. However, it needs improvements. The purpose of this master's thesis is to develop a method in which the application of CFD can be successfully relied upon, by identifying a set of boundary conditions used as initial data for the CFD simulation. The boundary conditions in this project are the driving conditions and the surface temperatures of the heat sources inside the engine compartment. Initially, a physical test is conducted, in which the surface and surrounding temperatures are measured. Surrounding temperatures will act as a comparison between the physical tests and the simulations. Once the boundary conditions have been measured through physical tests, the data acquired is then used for the simulation as initial values. The goal is to achieve a maximum of10% difference between the results of the physical test and those of the simulations. From the final results, the difference between the physical tests and the simulations is 24% for one of the driving conditions which is considered the best case. However, the results are an improvement compared to the old method used currently by Scania. The method developed in this masters thesis shows an improvement of 21% compared to the old method for the same driving condition which implies a step in the right direction for reliable simulations.

As emissions of polluting substances due to shipping are growing, newsolutions for ship propulsion are emerging. One of them is the suctionwing, a vertical wing designed to generate lift forward, and made even moreefficient than classical wings by the suction of its boundary layer. Thisproject allowed for the participation, within a team of mechanical engineers,in the early design of a pilot model of such a system, ultimately intendedto be industrialised. The design process was followed in order to define thesolutions to match the performances of each function of the wing, basedon a set of specifications, and to verify the sustainability of those solutions.Also, a particular interest in the furniture and/or manufacturing of thosesolutions was given. For those instances, the suction system was defined withthe collaboration of manufacturers. Also, the wing orientation system wasdefined and its integration was verified with respect to the deformation ofthe components at its interfaces. Then, The flap was designed in order todefine solutions to allow mobility transmission, taking into account its stressconditions. The solution for the sealing of the system was also worked upon.Finally, the main mast of the wing was designed so to maintain its integrity,with respect to its stress charges and its strong stress concentrations.

The drone industry is growing and the need for increased autonomy will be required if large fleetof drones will be able to fly without a single pilot per drone. A useful part of automating the flighten-route can be achieved with the upcoming standard of Direct Remote Id (DRI), which signalspositional data for drones and can be used as the perceptive part in a collision avoidance systembetween drones with the advantage of limited weight penalties and minimal financial cost.Simulations were carried out to understand different kinds of evasive maneuvers and develop asimple yet effective algorithm for avoiding obstacles and continue towards the next waypoint ona mission. Positional data can be retrieved with an ESP-32 board from a flight computer withMavlink protocol, which can then be broadcasted and received to an ESP-32 board using DirectRemote Id. The distances between the nearest drones can be computed, along with the shortest al-lowable distance and closest positions of the drones, if they were to continue on a straight course. Ifthe closest passing distance turned out closer than a set safety distance, an evasive maneuver is cal-culated and executed, with preliminary work focusing on evasion maneuvers on an horizontal plane.Flight tests showed that an evasive position could be calculated, and the drone successfully di-verted to it, while continuing with the mission after the evasion was completed. These resultsshowed the potential of using Direct Remote Id as a simple close proximity detection for use withcollision avoidance

This thesis presented an overview of the development of a geolocating algorithm as part of a geoprocessor for raw satellite imagery. This algorithm was devised for and limited by the specifications of a state-of-the-art multispectral telescope designed by Aistech Space, hosted onboard the Guardian spacecraft, which will observe Earth through the visible, near infrared, and thermal infrared bands of the electromagnetic spectrum. The geolocation algorithm presented here is composed of the combination of two models. The first is a physical model, which makes use of spacecraft telemetry and external satellite-tracking data to approximate the geographical center of a sensed scene. Secondly, an optical model obtains a reference Landsat image based on the timestamp and approximated location of the sensed scene and utilizes image processing techniques to pinpoint a more precise geographical location of the sensed scene within acceptable limits. This performance was achieved in 77% of the cases considered. To conclude, a roadmap of the subsequent development topics and their relevance was laid out.

 This thesis proposes a time-effective procedure for numerical prediction of the hydrodynamic performance of a small high-speed craft (HSC) for Search and Rescue (SAR) operations. Following a naval architecture review of available SAR designs, engineering physics and numerical methods for the evaluation of resistance and seakeeping are explained. A method that utilises Reynolds-Averaged Navier Stokes equations-based Computational Fluid Dynamics theory is utilised to predict calm-water resistance and wave-induced motions of a sample SAR vessel operating in regular waves. Simulations are performed using the Orca3D Marine CFD environment, utilising the Simerics CFD package. The method is validated against experimental results found in literature. The comparative study of calm-water resistance allows for analysing the influence of the hull shape on the performance of the craft. Seakeeping analysis is performed in one wave length. Head, oblique and following seas conditions are simulated. In head and oblique seas, obtained results in the time domain present periodic motions. Non-linear pitch motions are displayed, followed by amplitudes of motions calculations. High non-linearity of roll motions in oblique seas is observed. The thesis concludes that for less demanding cases, the proposed procedure offers a time-efficient method to estimate the hydrodynamic performance of the vessel with satisfying accuracy. Further research is required to optimise the method for obtaining results in following seas in an acceptable time frame.

The impact of air travel on the climate, along with its increasing share in CO2 emissions have raised the demand for sustainable air travel solutions. The current aircraft technologies have seen significant improvement throughout the years. Although, the rate at which new aircraft technologies are developed can not keep up with the increased demand for air travel. Hence, a different approach to reduce the aviation’s impact on climate can be achieved by optimizing the vertical flight path in order to reduce the fuel consumption, i.e. using dynamic programming.

Upon departure, an optimization of the vertical flight path is initiated and an optimal flight plan is suggested to the flight crew.

 The fuel saving produced by the optimal flight plan is a potential saving that can only be fully achieved if the flight crew chose to fly according to the optimized flight path. However, restrictions from the Air Traffic Control, as well as the flight crew’s willingness to follow the optimized flight path can affect the achieved saving. Hence, a tool is developed in order to compute trip fuel consumption from post-flight data obtained from the Automatic Dependent Surveillance-Broadcast (ADS-B) surveillance technology. A method to identify the start and end positions of cruise segments is successfully implemented. Two methods of calculating the fuel are implemented and compared. The first method is based on simulating the actual flight, which uses the same performance model as for the simulation of the operational flight plan trip and optimized trip. The second method is based on utilizing the ADS-B data to obtain the aircraft speed which in return can be used as a parameter to obtain the fuel flow of the aircraft, hence the trip is not simulated. The results reveals that the simulation method produces flight trajectories that are comparable to the operational and optimized flight plans since they use the same model structure. However, using ADS-B data to obtain fuel consumption represents the actual flight trajectory more accurately.

 Furthermore, an optimization algorithm based on the onboard Flight Management Computer is implemented. According to the results, the FMC optimization offers a sufficient optimization of the cruise phase, when compared to the OFP trip, however performs worse than the dynamic programming, which provides a global optimal solution.

The impact of air travel on the climate, along with its increasing share in CO2 emissions haveraised the demand for sustainable air travel solutions. The current aircraft technologies haveseen significant improvement throughout the years. Although, the rate at which new aircrafttechnologies are developed can not keep up with the increased demand for air travel. Hence, adifferent approach to reduce the aviation’s impact on climate can be achieved by optimizing thevertical flight path in order to reduce the fuel consumption, i.e. using dynamic programming.Upon departure, an optimization of the vertical flight path is initiated and an optimal flight planis suggested to the flight crew.

The fuel saving produced by the optimal flight plan is a potential saving that can only be fullyachieved if the flight crew chose to fly according to the optimized flight path. However, restrictionsfrom the Air Traffic Control, as well as the flight crew’s willingness to follow theoptimized flight path can affect the achieved saving. Hence, a tool is developed in order tocompute trip fuel consumption from post-flight data obtained from the Automatic DependentSurveillance-Broadcast (ADS-B) surveillance technology. A method to identify the start andend positions of cruise segments is successfully implemented. Two methods of calculating thefuel are implemented and compared. The first method is based on simulating the actual flight,which uses the same performance model as for the simulation of the operational flight plantrip and optimized trip. The second method is based on utilizing the ADS-B data to obtain theaircraft speed which in return can be used as a parameter to obtain the fuel flow of the aircraft,hence the trip is not simulated. The results reveals that the simulation method produces flighttrajectories that are comparable to the operational and optimized flight plans since they use thesame model structure. However, using ADS-B data to obtain fuel consumption represents theactual flight trajectory more accurately.

Furthermore, an optimization algorithm based on the on-board Flight Management Computeris implemented. According to the results, the FMC optimization offers a sufficient optimizationof the cruise phase, when compared to the OFP trip, however performs worse than the dynamicprogramming, which provides a global optimal solution

By working as an intern with the Quotation Officer of Sabena Technics Nîmes facility,an aircraft maintenance company, this degree project highlights the different factors totake into account in a quotation of civil planes (B737/B767/A320/A330) by analysingwork packages from airline company, applying a process to estimate the importantdata as the man hours or tools, and using my technical knowledge to understandmaintenance tasks. Management knowledge for commercial sale reviews was usefulas well, this job is in the middle of the commercial team and and the technicalteam. Finally, a critical opinion of the process has been made in order to propose animprovement of the next quotations.

A reduction in the global use of fossil fuels is necessary when striving for a more sustainable future. One key strategy in the transition from fossil fuels is electrification. This strategy is particularly prominent within the transport sector, where more efficient ways to store electric energy are being pursued. Structural battery composites represent a promising technology. Being based on multifunctional composite materials that can carry mechanical loads and store electrical energy at the same time, they provide a ‘mass-less’ energy storage.

This work aims to develop a shape morphing structural battery capable of bending upwards and downwards in a cantilever setup. The structural battery is made from several constituents. Two outer layers of carbon fibers act as negative electrodes and a middle layer of aluminium foil coated with NMC622 on both sides acts as the positive electrodes. Additionally, a glass veil layer and a ceramic separator separate the positive and negative electrodes. A structural battery electrolyte is used to embed the laminate in order to provide load transfer and ion transfer. From this setup, it is possible to control the lithiation/delithiation of each carbon fiber layer independently and thereby bend the laminate in the desired direction. Subsequently, the system is modeled both analytically using Matlab and numerically using Comsol Multiphysics 6.1. 

From the models it is found that the system is in theory capable of large deformations, showing promising results. However, the experimental laminates show low capacity upon cycling which would cause near to zero deformations. The poor performance of the system could be linked to incompatibility between the structural battery electrolyte and the NMC622.

The use of continuously reinforced thermoplastics have increased in recent years andoffer some significant advantages over their thermoset counterparts. The utilizationof these materials is however still limited due to the labour intensive processingand manufacturing. In the first part of this thesis, the aim is to investigate howcontinuously reinforced thermoplastics can be used in high volume manufacturingof complex components, specifically when combined with injection moulding. Thesecond part will attempt to develop a conceptual manufacturing process and designof a demonstrator part and perform a structural analysis of the component.To answer the first question, an extensive literature study on continuous fibre materialsand thermoplastics was conducted along with research on established and newlydeveloped manufacturing methods such as automated tape laying and fibre placement,tailored fibre placement and 3D printing combined with injection overmoulding. Theconceptual manufacturing process of the demonstrator part was then based on thisresearch and the design was modeled in using finite element analysis.The results shows that continuously reinforced thermoplastics can be used forhigh volume manufacturing of complex components when combined with injectionmoulding. While some of the processing methods are still in an early developmentstage, the techniques have been tested and implemented. The structural analysis of thedemonstrator part shows that the design can withstand the maximum external loadsthus and provide proof of concept.

The large carbon footprint of industries is one of the main issues raised when talking about climate change. Active carbon monitoring methods need to be implemented to give transparency to the industry market and to spread awareness and information. This thesis investigates multiple CO2 emissions monitoring via satellite monitoring for four different industries in the EU. The pulp and paper industry was monitored in Sweden through smoke detection coming from the chimneys of factories. The CO2 aggregated emissions of 14 Swedish factories were calculated with a mean error of 12%. The metal ore roasting, and sintering industry were successfully monitored as well through smoke detection. In Sweden with an error 4.6%, and in the EU with an error 9.5 %. The production of lime and the calcination of dolomite were unsuccessfully monitored due to no suitable method found. Finally, coke industry emissions were monitored through burned gas monitoring. The CO2 emissions were correlated to the real emissions with a mean correlation coefficient of 0.64. This study took part in a public information campaign lead by a Swedish start-up, and some results were displayed in Stockholm, Sweden.

Waterborne public transportation (WPT) is slowly increasing in importance as an active component of public transportation networks in cities. City planners are looking at WPT to overcome urban congestion and pollution. However, prevalent challenges like ferry procurement, poor state of existing ferry fleets and technical challenges like the presence of ice, have created reluctance in the minds of public transport providers (PTPs).  While contemporary research shows ferries can be economical and environmentally friendly, there are some fundamental challenges that need to be addressed before PTPs can feel confident.

In this regard, deterrents from PTP’s perspective are identified and solutions are investigated, starting with a systematic characterization of WPT. A definite structure for operational requirements is proposed in an objective manner. Using these as basis, two standard ferry sizes that could fulfil multiple WPT roles in majority of cities are introduced. For establishing city-wise tailoring, platform-architecture based modularization of ferries is proposed. The ferry modules are tailored with respect to operational requirements in a clear and objective manner through the introduction of an evaluation methodology. The method incorporates economic, social, environmental, and regulatory stakeholders. These proposed solutions are aimed at improving PTP’s confidence in WPT and provides solutions for the marine industry to produce quick, cost efficient and tailored ferries. 

Next, the scope is focused towards investigating sustainable operations in freshwater ice conditions, typically found in the Stockholm region in Sweden. The ice going ferries today operate with ice strengthened heavy hulls. While they work well in ice, they perform poorly in comparison with non-ice going ferries during ice free months. Correspondingly, solutions towards lightweight ice going hulls are investigated. 

This investigation starts with understanding ice-hull interaction mechanisms. Then, techniques to estimate the ice loads are investigated. We adopt a probabilistic approach to tackle the limitations due to the stochastic nature of ice and a lack of experimental data. The resulting load cases are used for evaluating lightweight structural concepts. 

The investigation is approached by dividing ice-hull interaction into quasi-static, dynamic and abrasive loading phases. Several candidates corresponding to the first two loading phases are investigated parametrically. The range of structural concepts include metal grillages, bio-inspired composites, and sandwich structures. Realistic loading models for quasi-static and impact mechanisms are developed and validated with experiments. The winning candidates for each loading phase are combined to propose a tri-layer lightweight structural concept. Three candidates for the concept are evaluated and compared.

The thesis answers several questions that riddle WPT today. But at the same time, it raises new questions. Several directions for future work are identified. With continued development, it would be possible to see modularly tailored ferries operating with lightweight hulls in WPT systems around the world.

A fundamental challenge in ice-prone waterborne public transportation systems is the need for ice-strengthening while being fuel efficient during ice-free periods. To achieve this, the use of lightweight hull structures is explored in the current study by starting with introducing a tri-layer structural concept for an ice going hull. The three layers correspond to abrasion loads, impact loads and pressure loads experienced during a typical ice-hull interaction. Several structural concepts suited towards these respective loading mechanisms are considered. Most favorable parametric variants are identified and assembled as contenders in the tri-layer concept. The assembly is tested against experimentally validated ice impact models in FEA as well as a realistic quasi-static pressure representation. Three different lightweight structural concepts including aluminum grillage, stiffened sandwich structure and metal-FRP stiffened sandwich structure are compared and discussed. It is found that the latter of the three concepts is suited best towards both quasi-static and impact loading. Ice going ferries built with ice strengthened lightweight hulls can reduce emissions, fuel consumption as well as increase the payload capacity. Such a ferry would be competitive with non-ice going ferries during ice free periods.

The current study focuses on the impact loading phase characteristic of thin first year ice in inland waterways. We investigate metal grillages, fibre reinforced plastic (FRP) composites and nature-inspired composites using LS Dyna. The impact mode is modelled as (a) simplified impact model with a rigid-body impactor and (b) an experimentally validated ice model represented by cohesive zone elements. The structural concepts are investigated parametrically for strength and stiffness using the simplified model, and an aluminium alloy grillage is analysed with the ice model. The metal–FRP composite was found to be the most favourable concept that offered impact protection as well as being light weight. By weight, FRP composites with a Bouligand ply arrangement were the most favourable but prone to impact damage. Further, aluminium grillage was found to be a significant contender for a range of ice impact velocities. While the ice model is experimentally validated, a drawback of the simplified model is the lack of experimental data. We overcame this by limiting the scope to low velocity impact and investigating only relative structural performance. By doing so, the study identifies significant parameters and parametric trends along with material differences for all structural concepts. The outcomes result in the creation of a viable pool of lightweight variants that fulfil the impact loading phase. Together with outcomes from quasi-static loading phase, it is possible to develop a lightweight ice-going hull concept.

Lightweight ice-class vessels offer the possibility of increasing the payload capacity while making them comparable in energy consumption with non-ice-class vessels during ice-free periods. We approach the development of a lightweight hull by dividing ice–hull interactions into quasi-static loading and impact loading phases. Then, investigative outcomes of lightweight concepts for each loading phase may be combined to develop a lightweight ice-going hull. In this study, we focus on the quasi-static loading phase characteristic of thin first-year ice in inland waterways. We investigate metal grillages, sandwich structures and stiffened sandwich structures parametrically using the finite element method. The model is validated using previous experimental studies. In total over 2000 cases are investigated for strength and stiffness with respect to mass. The stiffened sandwich was found to be the most favorable concept that offered both a light weight as well as high gross tonnage. Further, significant parameters and their interactions and material differences for the three structural concepts were investigated and their trends discussed. The outcomes result in the creation of a viable pool of lightweight variants that fulfill the quasi-static loading phase. Together with outcomes from the impact loading phase, a lightweight ice-going hull may be developed.

Within waterborne public transportation (WPT), one often observes a mismatch between the operational requirements and ferry characteristics. A method to holistically evaluate ferries with respect to local requirements could lead to tailored procurement and targeted refurbishment of existing fleet. In this study, we develop a structure for operational requirements and use it as a basis for a ferry evaluation methodology. The requirements’ structure follows a three-level hierarchy starting from broad vessel design to mandatory requirements to performance requirements. The performance requirements are based on the three pillars of sustainability, aided by commuter surveys carried out in Stockholm ferries, interviews with public transport providers (PTP) and previous literature. The evaluation of the ferry is performed using analytic hierarchic process (AHP) to convert the PTP’s subjective preferences and ferry performance into a single dimensionless index. Rules for quantification of performance metrics including social performance are proposed. The uncertainties associated with AHP are addressed by employing fuzzy AHP based on extent analysis and fuzzy AHP in combination with particle swarm optimization. Two applications including performance assessment of existing ferries and assembly of a modular ferry are discussed. The method can lead to objective decision making in ferry evaluation, potentially leading to a more efficient WPT.

Satellite constellation design has been a well-studied problem since the beginning of the space age. In recent years new concepts and approaches tried to solve it with fewer satellites whilst guaranteeing coverage to the areas of interest, whether globally or regionally. This thesis introduces a novel approach based on the repeating ground track concept. It then links and converts the constellation design problem to a Set Cover problem. Although it is NP-hard, the Greedy Algorithm is capable to approximate the solution in a polynomial time with a logarithm ratio. An application of the non-symmetric strategy is illustrated with in 36 different scenarios, where altitude, sensor swath and time requirement are varied. In addition to that, a comparison with the Walker constellation on 6 scenarios is analyzed and discussed. In most cases the non-symmetric strategy produces constellations with significantly less satellites required.

This study investigates methods for assessing threats in space. Space services are crucial to both civilian and military capabilities, and a loss of such systems could have severe consequences. Space systems are exposed to various types of threats. To ensure the benefits of space-based applications, protect space assets, improve security, and maintain the space environment, it is crucial to assess threats in space. This thesis focuses on co-orbital antagonistic threats arising from satellites that are capable of performing precision manoeuvres. These satellites could either perform physical attacks or perform operations such as inspection, eavesdropping, or disruption on other satellites. Lambert's problem can be utilised for calculating orbital transfers. By solving the problem iteratively over a range of values of when the transfer is executed and the transfer time, it is possible to detect when a transfer is feasible. This can be used to assess when a satellite can pose a threat to a target. The calculations of orbital transfers are improved by the implementation of a genetic algorithm. The algorithm can solve for both direct transfers to the target and transfers using multiple impulses. Furthermore, a genetic algorithm, called NSGA-II, which can handle multiple objective functions is also analysed. The implemented methods show the potential of being employed to assess threats, especially for direct transfers where a single impulse is executed to transfer to a target. In this case, it is possible to identify threats based on the satellite's $\Delta v$ budget. However, when additional impulses are introduced it becomes more complicated. It is more difficult to estimate when an attack is more likely to commence. The implemented methods show potential, but further research is required in order to develop a robust method to assess co-orbital threats. 

The conducted analysis has highlighted a few aspects that are crucial for assessing co-orbital threats. Information about the $\Delta v$ budget of the satellite that potentially could pose a threat must be available. Furthermore, space surveillance and tracking capabilities are essential to detect orbital changes, which can be vital to perform counter-operations in the event of an attack

The Generic Planning Tool (GPT) is a new software package being developed by the Flight Dynamics team at DLR. In an era where laser communications are becoming more and more relevant to data transmission for space missions, the GPT’s purpose is to compute highly accurate visibility windows and provide a wide variety of support information for both satellite-to-ground and inter-satellite links. What sets the GPT apart from previous products, is its shift from mission-specific to multi-mission and being able to accept various orbit and attitude data formats, thus enabling the support of multiple missions from DLR and external clients with flight dynamics information for mission planning applications. Its two main components are the core libraries written in Fortran, which serve as the powerhouse for the orbital mechanic’s computations, and the microservice architecture, enabled by JSON input/output files and Python scripts, which implement an automatic request-response service accessible over the network. This thesis will present why, how, and which GPT software functionalities were developed and tested during the internship at the German Space Operation Center.

Nowadays, the forestry industry still uses heavy machinery damaging both the forest and the soil. The start-up AirForestry is currently developing a sustainable way to thin and harvest trees. With their 6.2m wide electric drone carrying a harvesting tool, they can reach, thin, cut and carry trees without the need for access roads. Naturally, the drone needs to be as lightweight as possible to increase its endurance and operation range. Therefore, the first version of the drone was manufactured before the thesis with a carbon fibre laminate. 

The purpose of this thesis is to study and optimize the composite structure of the drone. The first step is to characterize the existing design through experiments and simulations using the software ANSYS. Static bending loads, free vibrations, and forced vibrations are investigated against a set of predefined design requirements. This study shows that the contact surfaces between each arm and with the motor holders have high-stress concentrations compared to the rest of the arm. This means that most of the arm can be made thinner to lessen the weight with some extra reinforcement on those problematic areas. 

The second step is to optimize the laminate to decrease the weight of the structure. A preliminary optimization was made and manufactured at the beginning of the thesis with strict limitations on the choice of the lamina or available thicknesses. Similar bending and vibration experiments and simulations are conducted on the new design to compare it with the older model. While the mass was expected to decrease by about 30 $\%$, the final measured weight of the arms indicates a drop of only 15 $\%$ of the mass. The model is then optimized further with more freedom in the design variables. Several variables are successively optimized: the material choice for the laminae, the thickness then of the laminae, and the angles of the plies. The mass of the structure with the final laminate has an expected decrease in mass of 45$\%$, saving more than 12kg in total

Autonomous underwater vehicles (AUVs) are robotic platforms that are commonly used to gather environmental data, provide bathymetric images, and perform manipulation tasks. These robots are used not only for scientific, but also for industrial and military purposes. Climate change, political instabilities, and the increasing demand for both renewable and fossil energy sources have created a need for high-performance AUVs and particularly long-range AUVs.

The performance of long-range AUVs is characterised by several parameters, such as autonomous decision making, accurate navigation, system reliability, and vehicle endurance. The vehicle’s endurance is the key capability enabling long-range missions and is determined by the energy capacity and power consumption. By cruising at optimum speed, the vehicle endurance can be utilised most efficiently, resulting in the longest achievable vehicle range. The range of AUVs can be extended by maximising the available energy capacity and by minimising the overall power consumption. This thesis shows how the choices of propulsion system and power source can help improving the range of AUVs.

The power consumption comprises the hotel load and propulsive power. While the hotel load is largely depending on the payload sensors, the propulsive power can be minimised by choosing the right propulsion system. As a part of this thesis, the transit performance of underwater gliders is analysed using an analytical approach. The analysis yields a glide metric for the assessment of the energy efficiency of underwater gliding and allows for comparison to other conventional propulsion systems.

The most common energy systems for AUVs are primary and secondary electrochemical cells, in particular lithium-ion batteries. Alternative energy systems such as fuel cell (FC) systems can potentially improve the range of AUVs. Through a conceptual design study using off-the-shelf components, it is shown how FC systems can increase the energy capacity of AUVs. FC systems are typically implemented as hybrid systems paired with a small capacity battery system. Energy management strategies (EMS) are required to coordinate these two power sources. In this thesis, deterministic and optimisation-based strategies have been tested in simulations and evaluated against realistic AUV power consumption data from field trials. The results suggest that the complexity of the EMS needs to grow with mission complexity. While deterministic methods can yield the lowest energy consumption for standard missions (e.g. bathymetric imaging), optimisation-based methods provide best load-following behavior, making these methods better suited for retaining power reliability through maintaining battery state of charge.

Our society depends on functional road communication, and Heavy Duty Vehicles (HDVs) offer convenient and limitless possibilities of transport and services. However, HDVs account for a quarter of the European Union's CO2 road emissions. There is a substantial need to reduce the CO2 emissions of HDVs to ensure a low negative environmental impact. To reduce the CO2 emissions of HDVs, their energy usage must be reduced. One way to reduce energy usage is to improve the structural efficiency of the vehicle and use high-performance composite materials such as Carbon Fiber Reinforced Polymers (CFRP). 

HDVs are continuously exposed to road-induced vibrations, and the fatigue loading often sets the design criteria for HDV components. Therefore, flexible simulation frameworks are needed to encourage and simplify the implementation of composite materials in engineering structural designs dimensioned for fatigue. This doctoral thesis proposes a probabilistic modeling framework for fatigue assessment of CFRP. The thesis aims to provide knowledge and insights into the fatigue modeling of composite materials and a better understanding of the proposed modeling framework.

A combination of experimental investigations and numerical modeling is conducted. To carry out fatigue testing, a fatigue testing procedure was established. Fatigue testing of anisotropic material involves accurately selecting process parameters to obtain specimens that fail in the gauge length. The fatigue damage progression of CFRP laminates was monitored throughout the fatigue tests by analyzing the stiffness change, finding that the initial stiffness loss can be related to the damage development of the specimens. 

Composite materials are multi-scale, where constituents and damage are of a much lower order length scale than the laminate and structure. Therefore, the numerical modeling uses a two-scale modeling approach to capture the variability of a composite laminate. First, the micro-scale modeling uses Representative Volume Elements (RVE) to determine the effective macro-mechanical properties of a composite lamina. The RVE models are generated based on experimental data capturing micro-geometrical variations that could affect the composite laminate behavior. Second, macro-scale models, capturing the complexity and variability of composite materials, are used in a probabilistic modeling approach for fatigue assessment. A Weibull distribution in a weakest link formulation is used to consider the combined effect of material variability of a CFRP laminate. 

The work proposes a probabilistic fatigue modeling framework for implementation in an industrial design process. The methodology is highly valuable in the progress of fatigue modeling of composites. It aims to encourage and simplify the implementation of composites in engineering structural designs and components dimensioned for fatigue. The insights and outcomes of this doctoral thesis play a crucial role in the advancement of future resource-efficient vehicles and an optimal selection of materials to design for the right material in the right place.

Systems for space are a challenge to construct. By creating the right requirements, the probability of creating the desired systems is increased. This thesis investigates the information flow between the NewSpace company Unibap, and their customers, concerning environment requirements, operational scenarios, and mission objectives. The investigation was conducted through a case study involving interviews, surveys, observation, and documents. The surveys were answered by personnel at the NewSpace company, and were followed by an interview. These tools were used to identify the important factors to understand while developing Unibaps products for space. The purpose of this thesis was to determine what information should be asked of the customers in the project. It was found that the environment, operational scenarios, and interfaces were the most important to understand at the beginning of the project. A document with questions to ask the customers at the beginning of the project was produced, as well as a process to improve the information flow.

This paper investigates using satellite data to improve adaptive sampling missions, particularly for front tracking scenarios such as with algal blooms. Our proposed solution to find and track algal bloom fronts uses an Autonomous Underwater Vehicle (AUV) equipped with a sensor that measures the concentration of chlorophyll a and satellite data. The proposed method learns the kernel parameters for a Gaussian process (GP) model using satellite images of chlorophyll a from the previous days. Then, using the data collected by the AUV, it models chlorophyll a concentration online. We take the gradient of this model to obtain the direction of the algal bloom front and feed it to our control algorithm. The performance of this method is evaluated through realistic simulations for an algal bloom front in the Baltic sea, using the models of the AUV and the chlorophyll a sensor. We compare the performance of different estimation methods, from GP to curve interpolation using least squares. Sensitivity analysis is performed to evaluate the impact of sensor noise on the methods’ performance. We implement our method on an AUV and run experiments in the Stockholm archipelago in the summer of 2022. 

This thesis deals with the scheduling problem for a constellation of Earth observation satellites, focusing on modelling the attitude dynamics to assess the tasking capabilities. A target selection algorithm is developed considering the time dependent manoeuvres between targets and the time-dependent value of the observed targets. Further, a closed-loop dynamics simulation is carried out to assess the agility of the 6U platform and verify the results of the algorithm. The work does not intend to present definitive numerical results, rather the goal is to develop a holistic framework that allows appraising the performance of a platform and the fulfilment of the mission objectives, aiming to maximise the collective value of the observed targets. Given the inputs in terms of platform, sensor, orbit and list of targets, this work serves to simulate the target selection and imaging at an arbitrary day and time for a chosen observation window.

A comparison between several numerical finite element methods to model progressive failurein composite materials is performed. The focus of the study is on the development of an efficientmethod to model crack growth phenomena in large-scale thermoplastic composite laminates.The analyses are performed in the commercial software Abaqus and include three discrete crackmethods and one smeared crack method, which are applied to model coupon tensile tests. Thethree discrete crack methods involve cohesive elements, cohesive contact properties, and theextended finite element method. The smeared crack method uses the Hashin damage initiationcriterion as already implemented in the software. The numerical results were compared bothto numerical and experimental references. A method to represent multiple failure modesin a single fracture surface is used both with cohesive elements and with a cohesive contactproperty. The cohesive contact method results in being the most efficient. To achieve a moreaccurate prediction of the damage evolution and of the final failure, a method using multiplesurfaces of cohesive elements is tested. A technique to scale the mesh by reducing the initiationstrength is evaluated. Both these last two studies show that more in-depth work is required tosuccessfully apply these methods.

The purpose of Model Seakeeping Experiments Presented in the Time-Domain to Facilitate Validation of Computational Tools has been to put together a well-arranged bank of model measurements, useful as a reference material in the validation procedure of real-time simulation models.

The work reports on seakeeping experiments on a model of an 11300 tonne ro-ro vessel. All information is at hand: hull geometry, model condition, test set-up, procedures and time series of the measured quantities.

The time series, together with the hull geometry, is stored on CD-ROM. The printed part of the work reports on the test set-up, procedures and post-processing, and gives a catalogue with overall data on each test. Experiments were performed in regular, irregular and short-crested waves at two speeds, corresponding to five and 15 knots, with relative heading varied around the clock. The wave systems were modelled by regular waves with amplitude corresponding to one-three metre and of irregular waves with significant wave height of five metre. For each test, the waves are described by an analytical expression. Those wave equations describing the wave elevation in time and space, can be used as sea environment when comparing the measurements with time-domain simulations.

The recorded data are from measurements of wave elevation, global and local motion, velocity and acceleration. Each of the 110 tests are described by time series recorded from 18 measurement channels.

Thanks to the generality of the tests and the accessibility of hull geometry and time series, the work should be useful not only as reference in cases of validation, but also to illustrate the dynamic behaviour of ships in the education of naval architects.

To further reduce weight remains a constant goal within aviation. In this project an aircraftconsole is redesigned from aluminium to carbon fibre composite and analysed to see ifit is possible to reduce weight while maintaining the ability to withstand the emergencylanding loads. There are in total 9 different load cases, but the focus is on 9 and 18g forward.The design of the composite console is an iterative process, and the outcome is a sandwichsolution with a basic layup of 3 carbon fibre composite layers, PVC core and another 3carbon composite layers. Each iteration is followed by analysis in Ansys workbench usingFEA, finite element analysis, and if stresses or strains are too high reinforcement layers areadded to areas of concern and a new iteration of layup and analysis is performed.The aluminium console weighs 17 kg and after iterating the sandwich console fivetimes the end result is a console weighing 12.2 kg. Which means a weight reduction ofapproximately 30%.Overall, the new composite sandwich console can withstand higher loads than the oldaluminium one but the fastening to the floor requires further analysis.

This volume covers the phases from design to manufacturing of a wind tunnel testsupport structure for a conceptual blended wingbodyUAV designed by KTH GreenRaven Project students. The innovative aircraft design demonstrates sustainabilitywithin aviation by utilizing a hybrid electricfuelcell propulsion system. The windtunnel test to be conducted at Bristol University will produce data to evaluate theaerodynamic properties of the model for design verification. The wind tunnel modelis a smallscaled1.5mspanmodel supported by struts that change the pitch andyaw angles during testing. An external force balance provided by Bristol Universitymeasures the loads and moments experienced by the model. The main requirementsfor the structure are to withstand the aerodynamic loads imposed by the model andto change the model’s orientation while maintaining wind speed during the test. Themaximum aerodynamic loads were provided in a matrix, the largest of which was usedas the load condition for the support equating to a 512N lift at 14◦ AOA. Trade studieswere conducted to determine the mechanisms to satisfy the requirements while stayingwithin budget. The chosen design for the support structure includes a circular baseplate constrained by a locking ring with positioning pins to change the yaw angle. Themain strut is mounted at the the center of the circular base plate. A hinge bracketat the top of the strut interfaces with another hinge bracket within the model viaa clevis pin. An electric linear actuator mounted downstream of the main strut isused to vary the pitch angle, with the center of rotation at the clevis pin. Once thedesign was finalized, finite element analysis was done to verify the structural stabilityof the design. The FEA results were compared to EulerBernoulliapproximations fordeflection. Manufacturing of the components was outsourcedwhile assembly andprogramming of the actuator was done inhouse.

The oceans are a key element in our society, economy and environmental system.They cover over 70% of the worlds surface and contribute substantially to ecosystemservices such as climate management as well as to economic sectors such as foodproduction and tourism. While the importance of the oceans for climate changeand the society is generally acknowledged in science and literature, it is often notreflected in policy. Integrated Assessment Models (IAMs) which are used to advicepolicy on carbon prices often systematically omit process and damages related tothe ocean such as ocean acidification, loss of biodiversity and changes in oceancurrents.The aim of this study is to give a more detailed perspective on ocean related processesand their role and importance for the economy under climate change and to testassumptions made in the development of IAMs - and more precisely the DynamicIntegrated Climate-Economy model also referred to as the DICE model. The initialresults of the DICE model resulted in a optimal temperature trajectory with amaximum of 4 ◦C contradicting the goals set with the Paris Agreement.This thesis is the first of its kind attempt in reviewing the most recentbiophysical evidence on climate change impacts with a focus on marine systemsand incorporating these damages to market and non-market sectors into the DICEmodel. The impacts from climate change are implemented into the DICE modelthrough economic valuation of the damages and an update of the damage function.The analysis is based on the damage function used in the original DICE2016R2model as well as the suggested update presented by Hänsel et al. (2020)The results show, that incorporating marine damages into the model yields in amajor increase in economic damages particularly in the temperature range up to 2◦C.These increased damages influence the results of the optimal temperature trajectoryand give a clear indication for a more stringent climate policy, drastically limitingthe maximum temperature increase compared to the original DICE model.

Performance models provided by aircraft manufacturers are used by aircraft operators to perform flight path simulations aiming to reduce aircraft fuel consumption. However, performance models are generic and does not account for the performance deviations of each aircraft individual. The performance deviations, particularly in terms of fuel consumption, will affect the dynamic programming of flight path simulations. This may result in a less optimal flight path and ultimately lead to higher fuel consumption than expected. In hope of reducing this risk, a collection of local performance factors were derived. These factors describe the percentual deviation between the real fuel flow and the levels predicted by the performance model, and are allocated with respect to a range of flight parameters in a data library known as the performance library. A test environment is then constructed to simulate a continuous flow of flight data, where a new performance library is derived from the flight data of every month. The local performance factors of the previous month are then updated with the current; a learning process based on the weighted average ensemble approach. Further, the local performance factors are used in conjunction with the performance model to estimate the aircraft fuel consumption during cruise. The observed average prediction error is noticeably smaller than that of an equivalent global, scalar performance factor used by airlines today. The result also reveals that the prediction accuracy and versatility of the performance library is mainly determined by its resolution - higher resolution generally offers better accuracy at a cost of requiring more flight data, whereas lower resolutions are more versatile but of lower accuracy. Finally, the performance libraries of two identical aircraft are used to trace the performance deviation between them. The weighted average of all local performance factors in the performance library of respective aircraft reveal that the average fuel consumption is roughly -1.9 % and -2.5 % lower than the estimates by the performance model, ultimately proving that it is feasible to detect overall fuel efficiency deviation between two identical aircraft.

To leave Earth’s gravity well and ascend into Cislunar space takes ingenuity, and the engineering feats of many. Now to propel humanity further into space, rockets will need assistance to provide the large requirements of mass to be used for space structures. Tsiolkovsky’s Rocket Equation greatly limits the advantages of rockets and leaves an opening for Space Elevators to assist in a dual space access approach. By moving a large amount of mass routinely, efficiently, environmentally friendly and with daily launches towards space. Along with the apex anchor situated at 100,000 km for emergency assistance across all Cislunar space, and to act as both storage facilities and a construction zone. Space Elevators are the railway to space and can supplement rockets by transforming how mass is transported to Cislunar space and beyond.

Planing hull is a common hull design concept which decreases the resistance while speed is increasing for a specific speed range. It is also suitable for hull modifications to achieve higher efficiency. Spray deflector is a promising hull modification which offers extra resistance decreasing and less vertical acceleration for planing hulls. Spray deflector technology can decrease the resistance up to 28% compared to the bare hull. However, the information on spray deflector design is strongly limited. In this study, there are two different types of spray deflector designs compared via CFD to achieve better design. Star CCM+ software was used to create CFD models with given numerical settings: 3-Dimensional, implicit unsteady, multiphase VOF, RANS based SST K-Omega turbulences model, all y+ Hybrid Wall Treatment while only considering heave and trim. Froude Number of the simulations ranges from 2 to 2.6. To improve the value of CFD models, mesh sensitivity study, time step study, y+ study, and alteration of prism layer number were conducted. The experimental base of this thesis is Molchanov’s “Experimental validation of spray deflectors' impact on the performance of high-speed planing” study from 2018. All CFD outcomes were evaluated according to these experiments. 

There is a problem named numerical ventilation which downgrades the value of outcomes. Thus, three different methods were evaluated against numerical ventilation additionally to the spray deflector comparison. These methods are “Phase Replacement”, “Modified High-Resolution Interface Capturing Scheme”, and “Volume Fraction Source Term”. Application of Volume Fraction Source Term method gave the best achievements for the calculation of resistance with 0.35% error ratio, and trim angle 17% error ratio while causing 16% error ratio for heave. The modified HRIC scheme achieved a 1.4% error ratio for heave, 12.5% error ratio for resistance, and 20.4% error ratio for trim angle. The restrictions of these methods and their application ways are specified in this thesis.

In order to satisfy the mechanical requirements for space structures, achieving lightweight designs is of the greatest significance. The primary focus of this study is the utilization of Kelvin cell core in the design of sandwich structures for space applications. The research encompasses a variety of production techniques, analyzes, and tests related to the design of sandwich structures with Kelvin cells as the core material. While a variety of configurations are evaluated in a general sense, particular configurations are examined in greater extensive detail. In this context, the structure's bending stiffness, compression stiffness, and vibration characteristics are analyzed. The analytical procedure begins with a simplified structure analysis, followed by the modeling of the actual geometry. According to applicable standards, stiffness values are calculated based on the deflection results of the analyzes. However, it is important to note that the tests performed on the modeled structures are conducted in a laboratory environment using additively manufactured samples. This permits a comparison between the obtained test results and the findings of the analyzes, shedding light on the effect of the manufacturing method. This study demonstrates that the honeycomb sandwich structure is superior in terms of overall stiffness. In addition, a specially designed reinforced Kelvin Cell structure possesses exceptional bending rigidity properties. In light of these findings, it is clear that the combination of Kelvin Cell core and specific reinforcement strategies has the potential to improve the mechanical performance of sandwich structures. In addition, the deformation results revealed by the analyzes showed that the structure can be deformed in large amounts in directions other than the direction of the force it is exposed to. This situation is of great importance for damping in space applications. As a result of vibration analyzes and tests, the effect of stiffness and mass increase in a certain direction on natural frequencies has been revealed, and with 3-point bending tests, the facing elastic modulus and core shear modulus values of the structure have been determined separately and its effect on the sandwich structure has been shown. Accordingly, this study examined and evaluated many aspects of the possible role of the Kelvin Cell in space applications.

In an existing mechanical industrial system, a hose passes through a chamber as the hose unrolls from the reel it is stored on. As the hose unrolls, the radius of the reel decreases and the position from where the hose leaves the reel varies from side to side on the reel. Thereby, the hose has a varying incoming direction to the chamber. The chamber, which is suspended and jointed in a pulley that the hose also passes through, is steered by the hose as it changes direction. For the function of the chamber, it is important that the chamber stays centered around the hose throughout the unrolling process. However, because of how the chamber currently is suspended in the pulley, the centering of the chamber is not satisfactory. The aim of the work presented in this report was to solve the centering problem. 

In order to solve this matter, a new design for the chamber's suspension was presented. This includes a new hinging point of the chamber to add another degree of freedom to the movement of the chamber, so that the direction of the chamber can match the direction of the hose. Moreover, a new mounting system for the sealing membranes at the chamber's inlet has been proposed to cope with anomalies in the expected direction of the hose. 

Prototypes of the suggested design changes were made. Tests with these indicate that the proposed design has the intended function and thereby has the potential to improve the centering. However, there was no opportunity to test and evaluate the prototype in industrial operation but only in a workshop environment. Therefore, further tests have to be conducted before the proposed design changes can be commercialized.

Wind propulsion is a traditional way to propel ships over the oceans. In the recent development towards more sustainable shipping, sailing is considered in the industry again with high momentum. For a modern merchant ship, the aerodynamic forces generated on the particular rigging are unusual. Tailored research and experiments are required to understand their influence on the ship’s sailing behaviour. This work concerns the aerodynamic interactions on a model-sized car carrier with four 360° rotatable, symmetric, rigid wings aligned along the centreline on deck. Differential pressures on the wings are measured to capture the generated normal forces. In a comprehensive post-processing, data recorded in systematic experiments at two apparent wind angles were evaluated. A comparison for the different wing positions on board the model shows stronger interactions in upwind sailing conditions than when reaching. The two-dimensional data prove a significant influence of the hull in the normal force profiles over the wing span. The results of this work indicate that the aerodynamic conditions while sailing have to be attentively considered for efficient wing trimming.

The geostationary orbit has many applications for Earth observation and telecommunications. Like all satellites, spacecraft in this type of orbit are affected by perturbations. These perturbations can modify the satellites trajectories and, without control, deviate them from their target position. In order for these spacecraft to keep their target orbit, station keeping manoeuvres are required. These orbital manoeuvres are performed by thrusters − electrical or chemical − and are thus platform dependent. As part of the ground segments, Flight Dynamics Software programs are used to plan these manoeuvres, taking into account perturbations and orbital propagation – which is the prediction of the orbital evolution of the satellites – as well as the specific spacecraft configuration. Telecommands are then sent periodically to the spacecraft through the ground stations to execute the manoeuvres. Part of the manoeuvres goal is to control the inclination drift, but during the end-of-life of the spacecraft it is also possible to save some fuel − and thus increase the mission lifetime − by not controlling the inclination anymore. In this paper, inclined orbit station keeping strategy and algorithms are developed to an industrial level for a specific spacecraft platform: the SpaceBus Neo, a geostationary platform developed by Thales Alenia Space within ESA’s Neosat program. Additionally, some inclined orbits produced by the developed software are presented and analysed.

Structural steel plays a fundamental role in the heavy industry, serving as a key material for numerous load-bearing products and equipment. Its widespread use is attributed to its robustness, resistance to wear, ease of use in construction, and cost-effectiveness. As industries increasingly focus on sustainable development, there is a growing emphasis on efficient material use and the enhancement of component performance. The optimisation of structures, achieved through integrating high-performance materials and appropriate design methodologies, is crucial in advancing product development. Such design strategies should focus on maximising structural capacity while maintaining economic viability. Although the production costs for these optimised structures may be higher, this is often compensated by their reduced operational costs and lower environmental impact. 

The implementation of high-strength structural steels for lightweight and high-performance structures necessitates a design that can withstand high stress. These materials offer increased static strength and exhibit enhanced fatigue resistance thanks to their advantageous microstructure. However, the full potential of these materials in structural applications is significantly influenced by design decisions and manufacturing techniques. Common production methods, such as welding and cutting, often impede the improvement of fatigue strength in high-performance materials, as numerous standards and guidelines indicate. Therefore, to fully leverage the benefits of high-strength materials, it is crucial to enhance and comprehend the effects of weld quality, cut edge quality, defect tolerance and potential post-weld treatments, ensuring these factors align with the materials' enhanced strength characteristics.

The present work investigates aspects that could enhance the reliability of load-bearing structures, thereby facilitating the use of high-stress designs and the integration of high-strength steels. It identifies the quality of welds and cut edges as a key limiting factor. The research thoroughly examines its impact and proposes new recommendations. The defect tolerances are also further studied to understand how defects impact these high-strength materials. The findings offer vital insights for developing improved quality recommendations for welds and cut edges, which are fundamental in effectively utilising high-strength steel.

Wing-in-Ground (WIG) effect aircraft are gaining attention for their potential in reducing environmental impact. However, optimising wing planforms based solely on aerodynamics might improve performance while compromising static height stability of WIG aircraft. This study investigates the effects of planar and nonplanar wing planform optimisation for regional transport ground effect aircraft. Three distinct multiobjective wing planform optimisations are explored: planar wing optimisation, nonplanar wing optimisation, and nonplanar wingtip optimisation. These optimisations assess the impact on both aerodynamic efficiency and static height stability characteristics of a wing planform in ground effect, at three different flying altitudes. In extreme ground effect, the Pareto set includes wings with negative spanwise camber, enhancing both cushion sensation and aerodynamic efficiency by effectively utilizing ground effect, thus proving advantageous over planar wing configurations.

High-Frequency Mechanical Impacts (HFMI) is a surface treatment technique utilized to introduce residual stresses and extend the service life of structures. This project primarily focuses on studying the life extension effects of HFMI on welded structures that have undergone fatigue and have existing cracks. This is of significant importance for the maintenance of structures jointed with welds, such as bridge structures. Therefore, this project selected welded components with lower fatigue strength in bridge structures as research specimens for analysis and testing.To simulate the conditions that bridges experienced over many years of usage, initial notches were prepared near the weld toes. A data acquisition and control system was developed to analyze crack propagation behavior, using NI devices to assess the pre-fatigue condition and control the fatigue testing machine. To understand the test results, fracture mechanics calculations and finite element simulations were applied for comparison.In conclusion, based on the experimental results, HFMI improves the life of welded structures with cracks. This demonstrates the feasibility of using HFMI for the maintenance of bridge welding structures and extending their service life.

An aircraft is exposed for a certain risk during warhead deployment. If the distance is too short between the aircraftand warhead during burst, fragments may hit the aircraft with fatal consequences. The warhead consists not onlyof fragments created during burst but also parts to attach it to the aircraft such as mounting plates and fasteningloops. These parts have a significantly larger mass than natural fragments and may travel far during trajectory.The problem for a potential hit of fragment on a fighter jet after its warhead has detonated has been presentsince several decades. It is of interest to analyse the problem to effectively reduce the warheads arming time andthe aircraft’s altitude during warhead deployment. The complexity consists of how the mounting plates and fas-tening loops behave during trajectory, which may affect the travelled distance if they rotate or tumble. Attemptsto solve this problem for the Gripen fighter jet has been made by Staffan Harling at FOI which this thesis is asubsequent work.

This thesis treats a risk perspective analyse of the distance between the aircraft and warhead named range safetydistance. Travelled distances for fragments are calculated with variation in velocity, drag coefficient and ejectionangle to analyse the problem to a wider extent.

The conclusion states that the time from warhead deployed until it burst should be at least seven seconds. Genericdata has been used in this master thesis due to classified information concerning real cases. Focus has been onthe method and to develop a Matlab code that hopefully can be used to estimate range safety distances from aappropriate risk perspective.

Following the liberalization of the aviation market in the mid-1990s, there has been a significant increase in aviation activities worldwide. This has inevitably resulted in the expansion of airports, which in numerous regions has led to concern and conflicts over increased noise levels. For people residing near airports, the constant noise can be distressing, interrupting sleep and leading to general noise annoyance. Indeed, noise pollution is serious and ranks second as the most significant environmental health hazard after air pollution. The World Health Organization's 2018 guidelines on environmental noise affirm this, highlighting the harmful effects and setting stricter aircraft noise thresholds than previous standards.This poses challenges, as the current technological landscape finds it difficult to achieve the necessary noise reduction. Plus, given the long life expectancy of the existing aircraft fleets, modern technological advancements pushing noise reduction will not be realized within the next decade. Noise mitigation strategies should, therefore, not only focus on technological advancements but also consider other paths forward, such as noise abatement landing procedures. 

During the flight cycle, it is the landing phase that contributes most significantly to the noise impact. This is well-known, and through the years, methods have been designed that effectively mitigate noise during the middle stages of the approach, principally by maintaining aircraft at elevated altitudes for extended periods and bypassing noise-sensitive areas. However, the dynamic noise characteristics of the aircraft itself are often overlooked, missing opportunities for noise reduction in closer proximity to the airport. Adopting an experimental approach, the work presented in this thesis investigates the possibilities of quieter landing procedures, focusing on the final phase of the approach and the aircraft as a variable noise source. Findings suggest that quieter approach procedures are feasible without interfering with established safety standards, emphasizing delayed landing gear deployment as a key strategy. However, reconciling the goals of sustainable aviation with the demands of present-day air traffic remains a formidable challenge. In other words, fly less.

This Master thesis report contains a complete attitude and orbit control analysis for solar sail spacecraft in the Circular-Restricted-3-Body-Reference frame. The overall goal of the project is to drive one solar sail from the edge of the Earth Sphere of Influence to a vicinity of the sub-Lagrange1 point. First, a trajectory control optimization has been performed using a direct transcription method to find an optimal control to guide the solar sail to a neighborhood of the sub-Lagrange 1 point. Then, the stability of the artificial equilibrium points in the Sun-Earth system has beeninvestigated. Two options are detailed in the following study: Halo orbits which correspond to periodic motion, and the implementation of a PD-controller on the solar sail normal vector to make any artificial equilibrium point asymptotically stable. An attitude control analysis study has been performed to estimate the needed torques for all the mission phases. This report is one of the first step for Space sunshade missions in the vicinity of the sub-Lagrange 1 point.

This paper presents the study of energy analysis methods enabling the understanding and the classification of flutter mechanisms. The cases of application of the internship are generic business jets. The report is divided into two parts: the improvement of the energy analysis already in place in the internal aeroelasticity software; and the development of prospective methods of energy analysis to identify the influence of each zone in the flutter mechanism directly on the mesh. After having identified the pros and cons of the initial energy analysis method, various proposals for improvements were made and a MATLAB tool was produced to enable users to compare them with the method already in place. The results show equivalent performances to identify the important modes in a flutter mechanism and a better understanding of the flutter mechanisms thanks to the new analysis. The second axis investigated during this internship has for final objective the identification of flutter mechanism thanks to computations of the contribution of each zone in the evolution of the work of the flutter mechanism. The work done during the internship has shown how to use the current tools to track the role of each zone in the work as a function of speed for each flutter mechanism but also the current limits to perform these analysis effectively. The results show the usefulness of such an approach to improve the analysis of flutter mechanism and could be an important complement to the study of deformation of the flutter mode for the comprehension of the flutter mechanism. It also highlights that observing the work of aerodynamic forces or deformations of the flutter mode at the flutter point is often insufficient for identifying a mechanism.

Carbon fibers submitted to high temperatures (>2000 °C) experience a permanent increasein their thermal conductivity. This change has been attributed to a change in the molecularstructure due to graphitisation. Graphitisation occurs when amorphous carbons are exposed tohigh temperatures (> 1000°C) for a prolonged period of time and describes the process in whichcarbon atoms are rearranged from their amorphous form into structured hexagonal ringed latticesheets. To characterise the extent of this process, one needs to determine certain ring statisticswhich provide information on the bonding structure. In this work, we develop and verify a ringstatistics tool that can be used to analyze the resulting structure of atomistic simulations, and useit in a novel approach to characterise the extent of graphitisation in Molecular Dynamics (MD)simulations of carbon. Different ring definitions, such as Franzblau, Leroux, Hybrid and King arecompared to determine the most appropriate definition for the investigation of carbon structures.A new ring definition, Hybrid, is introduced as an extension of Leroux’s definition, exploiting theefficiency of Leroux’s definition while making the definition more appropriate for carbon systemsby removing shortcuts of length 1. It was found that Franzblau rings most accurately capturecarbon structures, and are most optimal for the investigation of amorphous and graphitisedcarbons. We then apply this tool to two MD simulations of amorphous carbons undergoing anannealing process at 4000K for 300 ps to characterise the extent of graphitisation. We found aprevalence of ∼0.1 hexagonal rings per atom in amorphous carbons prior to annealing, comparedto ∼0.33 hexagonal rings per atom in graphitised carbon after annealing. The likelihood of a ringbeing hexagonal in amorphous carbon was ∼30%, as opposed to ∼75% in graphitised samples.Calculating the ratio in the number of hexagonal rings per atom to the number of hexagonalrings per atom in a fully graphitised system, the extent of graphitisation can be quantified. Sincethis value is normalized by the number of atoms in the simulation this method can be appliedto any domain size. This successful application of the ring statistics tool opens the door toapply it to more realistic and complex systems. The tool has already been expanded to considermulti-component systems and molecule identification. Hence, the tool could already be appliedto more complex cases, such as doped or contaminated systems, investigating the effects on bondstructure. In its current state, the tool could also be used to investigate how the extent andrate of graphitisation changes at different depths in a system. Potentially characterising therate at which graphitisation penetrates a system under various conditions. The tool also hasthe potential to be expanded to consider localisation and identification of defects, bond angles,bond creation and destruction and the structural classification and identification of systems.Combining this tool with MDSuite, a software in development by the Institute for ComputationalPhysics (ICP) at the University of Stuttgart with the collaboration of the von Karman Institutefor Fluid Dynamics (VKI) to analyse MD trajectories, could offer a package that can providedeep system information for minimal cost.

Measuring the thrust of cold gas micro-thrusters, due to the small magnitude of the generated force, is a challenging task, and to obtain satisfying quality of results usually careful adjustments of the setup has to be performed. The work presented in this paper aims at improving the quality of such measurements at the GomSpace Sweden company. The work consists of two parts: In the first part the author focuses on improving current thrust measurements setup implemented in the company, which consists of a vacuum compatible laboratory scale. It was observed that the results obtained from this setup were approximately 25‒35% lower than expected. A test campaign performed within the work found that this was associated mainly with backflow of plume expansion gases. Covering the scale and the tested propulsion unit with a box having openings only for thrusters was proved to be sufficient setup upgrade to mitigate the issue. In the second part of the project an alternative setup utilising a hanging pendulum-based solution with strain measurement-based force sensor is proposed and its design is thoroughly described. Results of initial tests of a 3D printed prototype of this setup are presented, proving its potential to produce results with better quality of output than the laboratory scale.