Mesoscale processes (atmospheric phenomena with horizontal scales ranging from a few tens to several hundred kilometres and lasting from a few tens of minutes to a few days) have the potential to influence the chemical composition of the troposphere. Tropopause folds and mountain waves are two important types of mesoscale processes. Concentrations and gradients of trace gases like ozone (O3) can be influenced by these processes. Tropopause folds bring ozone-rich stratospheric air to lower altitudes. Mountain waves and turbulence associated with them influence O3 gradients in the troposphere. Tropospheric O3 is a toxic pollutant and a short-lived greenhouse gas with an influence on the lifetime of many other trace gases. Understanding of its long-term development and budgets are important. For this, better understanding, generalization and representation of mesoscale processes are necessary. Observations made by the 52MHz wind-profiler radar ESRAD (ESrange RADar) and the 54.5MHz wind-profiler radar MARA (Movable Atmospheric Radar for Antarctica) served as the basis for this study. ESRAD is located close to Kiruna in arctic Sweden and has been in operation since July 1996. This is a site with frequent mountain wave activity. By analysis of ESRAD and sonde data we have studied vertical mixing and turbulence associated with mountain waves. An attempt was made to show the influence of these processes on relaxation of the O3 gradient in the lower troposphere. Additional balloon-borne in situ measurements of vertical profiles of atmospheric characteristics (temperature, humidity, O3 mixing ratio) complement the radar measurements and aid in correct identification and improved understanding of the observed processes as well as of the radar backscatter signal itself. MARA was operated at the Swedish summer station Wasa (73°S, 13.5°W) during austral summer 2010/2011 and at the Norwegian year-round station Troll (72°S, 2.5°E) nonstop since December 2011. During its operation at the Wasa station, ozonesonde measurements were successfully undertaken during the passage of a tropopause fold. These provided validity to the radar measurements and proved them to be a useful tool for tropopause fold studies, for the first time at Antarctic latitudes. Data gathered at the Troll station exhibit signs of an annual cycle of tropopause folds with winter maximum and summer minimum in their occurrence rate which is similar to the observed behaviour in the northern hemisphere. Comparisons with ECMWF (European Centre for Medium-Range Weather Forecasts) model data and the WRF model (Advanced Research and Weather Forecasting) show that higher resolution models such as WRF are needed for more adequate representation of these processes. High resolution models can in return serve as a basis for studies of areas that are not at all or only partially covered by measurement networks, as well as for global studies. Thus they can provide useful information about atmospheric transport and the state of trace gases like O3. / <p>Godkänd; 2013; 20130101 (marmih); Disputation Ämne: Rymdteknik/Space Engineering Opponent: Senior lecturer Suzanne Gray, Dept of Meteorology, University of Reading, Reading, United Kingdom Ordförande: Professor Sheila Kirkwood, Institutionen för system- och rymdteknik, Luleå tekniska universitet, Luleå /Svenska institutet för rymdfysik, Kiruna Tid: Måndag den 11 februari 2013, kl 09.00 Plats: Aula, Institutet för rymdfysik, Kiruna</p>

The Earth and its atmosphere are embedded in the magnetosphere, a region in space dominated by the geomagnetic field, shielding our planet as it acts to deflect the energetic solar wind. Even though the atmosphere is protected from direct interaction with the solar wind it is indirectly affected by significant magnetosphere-solar wind interaction processes, causing constituents of the upper atmosphere to flow up into the magnetosphere. The fate of the atmospheric originating ions is interesting from a planetary evolution point of view. If the upflowing ions in the magnetosphere are to escape into the solar wind they need to not only overcome gravity, but also the magnetic forces, and therefore need to be energized and accelerated significantly. The subject of this thesis is analysis of oxygen ions (O+) and wave field observations in the high altitude cusp/mantle and in the high latitude dayside magnetosheath of Earth, investigating magnetospheric processes behind ion heating, outflow and escape. Most data analysis is based on observational data from the Cluster satellites, orbiting the Earth and altitudes corresponding to different key regions of the magnetosphere and the immediate solar wind environment. The mechanism behind O+ heating mainly discussed in this thesis is energization through interactions between the ions and low-frequency waves. The average electric spectral densities in the altitude range of 8-15 Earth radii are able to explain the average perpendicular temperatures, using a gyroresonance model and 50% of the observed spectral density at the O+ gyrofrequency. Strong heating is sporadic and spatially limited. The regions of enhanced wave activity are at least one order of magnitude larger than the local gyroradius of the ions, which is a necessary condition for the gyroresonance model to be valid. An analysis indicates that enhanced perpendicular temperatures can be observed over several Earth radii after heating has ceased, suggesting that high perpendicular-to-parallel temperature ratio is not necessarily a sign of local heating. This also explains why we sometimes observe enhanced temperatures and low spectral densities. We also show that the phase velocities derived from the observed low frequency electric and magnetic fields are consistent with Alfvén waves. Outflowing ions flow along magnetic field lines leading downstream in the magnetotail, where the ions may convect into the plasma sheet and be brought back toward Earth. However, the effective heating in the cusp and mantle provides a majority of the O+ enough acceleration to escape into the solar wind and be lost, rather than entering the plasma sheet. The heating can actually be effective enough to allow outflowing cusp O+ to escape immediately from the high altitude cusp and mantle along recently opened magnetic field lines, facilitating a direct coupling between the magnetospheric plasma and interplanetary space. Observations in the shocked and turbulent solar wind (the magnetosheath) reveals hot O+ flowing downstream and approximately tangentially to the magnetopause and often close to it. An estimated total flux of O+ in the high-latitude magnetosheath of 0.7 ·1025 s-1 is significant in relation to the observed cusp outflows at lower altitudes, pointing to that escape of hot O+ from the cusp and mantle into the dayside magnetosheath being an important loss route. / <p>Godkänd; 2013; 20130227 (ysko); Tillkännagivande disputation 2013-04-04 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Rikard Slapak Ämne: Rymdteknik/Space Technology Avhandling: O+ Heating, Outflow and Escape in the High Altitude Cusp and Mantle Opponent: Professor Andrew Yau, Department of Physics and Astronomy, University of Calgary, Canada Ordförande: Docent Hans Nilsson, Institutionen för system- och rymdteknik, Luleå tekniska universitet Tid: Fredag den 26 april 2013, kl 10.00 Plats: Aula, Institutet för rymdfysik, Kiruna</p>

Spacecraft project management calls for division of project lifetime into phases, with specific goals to be fulfilled at the end of each phase. During first few phases a Preliminary Design Review (PDR) has to be conducted, after which top-level hardware design is not to be changed. This thesis describes a process of creating and demonstrates a software framework supporting teams building small satellites - typically CubeSat student projects - during initial phases of conceptual design, mission planning, and selection and sizing of hardware components. The scope of the thesis covers review of available tools for satellite mission and control system design, then it proposes a self-made MATLAB/Simulink toolbox - Spacecraft Control Architecture Rapid Simulator (SCARS) Toolbox, as a open source tool with gentle learning curve and ease of reverse engineering approach. In further parts of the thesis examples of usage are provided, and conclusions and descriptions of problems are presented. In the end, this thesis should not only serve as a description of SCARS toolbox, but also as an insight into the task of building a small satellite simulation.

Aircraft Cabin Ventilation systems are crucial for not only maintaining a fresh supply of air but also help in proper air distribution control and reducing airborne pathogen contamination. Passenger thermal comfort is of vital importance for a comfortable cabin environment and thus the need to measure environmental parameters such as velocity and temperature stratification for different ventilation systems is paramount.  Experimental setups often lead to investigation uncertainties and limitations of measured data in a mock-up model when compared to a real cabin. This is due to simplifications either made in the geometry or air supply systems and thus a careful comparison of airflow differences due to the simplifications should be considered. Computational Fluid Dynamic (CFD) models of aircraft cabins can provide a virtual solution for a physical phenomenon (in this case, airflow distribution of an aircraft ventilation system) and thus, such simplifications can be studied and comprehended while reducing the cost and time associated with experimental setups. CFD studies, however, do require thorough verification and validation to avoid compromise on accuracy. This study investigates different aircraft cabin ventilation systems using CFD to analyze airflow distribution and its implications on the thermal comfort and contaminant transport in the cabin. The CFD study results are verified by conducting a mesh sensitivity study since there is no experimental investigation to validate against. This master thesis project was performed at Linköping University in the Applied Thermodynamics and Fluid Mechanics division at the Department of Management and Engineering. A generic single-aisle cabin of a regional jet aircraft is modelled and further implemented in a CFD solver to simulate different Aircraft ventilation systems. The aircraft cabin is modelled using the Autodesk Fusion 360 CAD tool and a CFD model is set up in ANSYS FLUENT using a RANS RNG K-epsilon turbulence model with Enhanced wall treatment. Human Manikins are also designed to represent passengers and are included as heat sources to study thermal distribution. The mouth is used to release CO2 to stimulate breathing through respiration. A tracer gas (CO2) used to represent a pathogen which is discharged from an occupant as a cough or sneeze to study its diffusion path and infection risk. The aircraft cabin is reduced to a cross-section of one row of four seats abreast with a periodic boundary condition which is used to imitate the entire length of the cabin to help reduce meshing as well as computational cost.

Mars : The red planet has been on top in the priority list of interplanetary exploration of the solar system. The Mars exploration landers and rovers have laid the foundation of our understanding of the planet atmosphere and terrain. Although the rovers have been a great help, they also have limitations in terms of their speed and exploration capabilities from the ground. Throughout the whole mission period the rover is limited to travel for couple of Kilometers, and the lack of terrain data in real time also limits the path planning of the exploration rovers. It would be beneficial in terms of extended range of operation to have a secondary system that can fly ahead of the rover and provide it with pre-mapped terrain so that the rover can select the optimal site to perform scientific experiments. The INGENUITY Mars helicopter is designed to test the technical demonstration of aerial flight in the thin atmosphere of Mars. This project will use some of the research and developments done for the ingenuity helicopter and aims to simplify the rotor craft's design by adding more rotors and getting rid of the variable pitch control used in ingenuity helicopter. In this thesis we have proposed a multi rotor UAV that is developed for powered flight in the Mars atmosphere. This thesis will give insights about the constraints and solutions to allow an autonomous UAV to fly in the thin atmosphere of Mars. The thesis will focus on the selection of the optimal airfoil for low Reynolds number flow on Mars, its aerodynamics which will be followed by flow simulations in CFD software to extract thrust parameters for the UAV. The later half of the thesis project will be primarily focused on designing a low level controller for the UAV to execute some basic commands like hold position, do roll,pitch and yaw movements and following a specific path. From the control prospective the scope of this master thesis is to make a mathematical model of the Mars UAV and design a PID controller for the vehicle. The project will conclude the simulations and control response from the PID controller and as a future work an LQR and MPC can be developed for the Mars UAV.

The continuous demand to improve turbine performance has led manufactures to focus on aspects that have been previously considered of secondary importance such as the secondary air system. The purpose of this system is to cool the components and prevent ingestion of hot gas into the stator-rotor cavity that could lead to low frequency pressure fluctuations called Cavity Flow Instabilities. These instabilities could cause unpredictable rotor vibrations and damage several components. A CFD method capable of detecting cavity flow instabilities in a rotor-stator disk cavity system is investigated, based on the 360◦model of the cavity without anystator vanes and rotor blades. Boundary conditions are simplified by considering steady and uniform flow in the main gas path. Different turbulence models are tested such as Realizable k−ε,k−ω SST, DDES, and SAS. In order to test the performance of the method, different purge flow levels are simulated. The most successful results, are predicted by the Realizable k−ε turbulence model. This model predicts two rotating low pressure structures in the cavity, for low purge flow levels. These pressure structures rotate at approximately 80% of the rotor speed. Furthermore, the spectra analysis of the pressure shows a reasonable agreement with the experimental results in terms of the frequency, showing a distinct region of low frequencies pressure instabilities. Nonetheless, this method overpredicts the amplitudes by a factor of 3-7 depending on the frequency. In addition, regions of one order of magnitude higher in frequency is also predicted. The DDES model shows similar findings but the amplitudes in the pressure spectra associated to the low frequencies are lower. Additionally, SAS also predicts the pressure in-stabilities but, in this case, the amplitudes are closer to RANS simulations, yet the high frequencies disappear. Unfortunately, k−ω SST, did not predict these pressure instabilities. Further research is still needed in many of the aspects of this work, from the simplifications up to the turbulence models. However, it is concluded from this work that this method could be a useful tool for turbine design as it decreases the need for testing and prototype manufacturing.

Current state-of-the-art of propulsion system for space vehicles does not allow to deliver therequired payload for the mission to all bodies in the Solar System. Therefore, alternatives havebeen developed to reach those bodies without having the necessary technology. Gravity AssistManoeuvres take advantage of the encounter of the spacecraft with one or more celestial bodies tomodify the velocity vector of the spacecraft. These manoeuvres have already been used previouslyto reach high v targets with a very low propellant consumption.This thesis models a Gravity Assist Manoeuvre to later apply the model to a space mission to reacha target with multiple gravity assist manoeuvres around the Moon to reduce the fuel consumption.In the first part, the gravity assist manoeuvre is designed based on the angle that the normal vectorof the plane of the fly-by forms with the perpendicular vector to the velocity of the spacecraft onthe Moon reference frame and the velocity of the Moon. The second designed parameter for thefly-by is the angle that the velocity of the spacecraft relative to the Moon rotates about the planeof the fly-by modifying the direction of the spacecraft’s velocity.The second part of the project applies the previous concept of gravity assist manoeuvres to aspace mission. A spacecraft orbiting on a Geostationary Transfer Orbit is injected into an orbitto the Moon. Once the spacecraft reaches the Moon, it flies by the Moon modifying the directionand magnitude of the velocity of the spacecraft in the Earth reference frame. The orbit obtainedafter the fly-by is then propagated for a given period of time before injecting the spacecraft againinto an orbit to the Moon. After arrival to the Moon, the direction and magnitude of the velocityof the spacecraft in the Earth reference frame is modified through a second fly-by. Afterwards,the previous process is repeated again for a third fly-by before transforming the velocity of thespacecraft into the Heliocentric reference frame. The orbit is propagated for a period of timebefore getting injected into an orbit to the target of the mission.The third part of the project aims to optimise the mission developed in the second part, thoughonly two fly-bys will be considered in this part to simplify the optimisation process. The previousmission has been developed in several sections and the minimum fuel consumption has beendetermined individually for each section, obtaining a local minimum. Unfortunately, the globalminimum fuel consumption determined as the addition of those local minimum fuel consumptionmight be different, i.e. different sections might influence other sections leading to a lower globalminimum fuel consumption that has not been considered before.The fourth and last part shows future work that might be done to the project. It includes themodification and application of the code for the optimisation, the study of powered fly-bys tomodify the previous parts, and the addition of perturbations and space interactions to develop amore realistic mission.

Helicopters have been valuable vehicles ever since their invention. Their capabilities for axial flight and hovering make them an outstanding resource. However, their complexity, directly related to their aerodynamics, makes them extremely hard to design. In today’s market competitivity resources must be optimized and accurate models are needed to obtain realizable designs. The well known Blade Element Theory was used to model helicopter rotors using the Modelica based software SystemModeler. However, it remained unverified due to the lack of experimental data available. The access to experimental data published by NASA motivated the comparison from the model to the measurements obtained during real testing to a scaled rotor. Some improvements were performed to the model obtaining unexpectedly accurate results for hover and axial flight. Two approaches based on the Blade Element Theory and related to Vortex Theory were followed: an infinite number of blades and a finite number of blades. Moreover, the model simulation speed was notice ably increased and prepared for the forward flight model development. Nonetheless, even though the model was ready for forward flight simulations, further research is needed due to, again, the lack of experimental data available. It is concluded from the present work that Wolfram’s SystemModeler can be used as a tool in early design phases of helicopters, even before CAD modeling and CFD due to its simplicity, speed, accuracy, and especially its capability for being used on simple desktop computers.

Propulsion system testing before mission operation is a fundamental requirement in any project. For both industrial and commercial entities within the space industry, complete system integration into a static test platform for functional and performance testing is an integral step in the system development process. Such a platform - if designed to be relatively safe, uncomplicated and reliable - can be an important tool within academia as well, giving researchers and students a possibility for practical learning and propulsion technology research. In this thesis, a preliminary design for a liquid-propellant rocket engine testing platform to be used primarily for academical purposes is developed. Included in the presented design is a bi-propellant Chemical Propulsion system, gas pressure fed with Gaseous Nitrogen and using Gaseous Oxygen as oxidiser and a 70 % concentrated ethanol-water mixture as fuel. The propellant assembly contains all necessary components for operating the system and performing combustion tests with it, including various types of valves, tanks and sensors. An estimation of the total preliminary cost of selected components is presented as well. Also part of the developed platform design is a small thrust chamber made of copper, water-cooled and theoretically capable of delivering 1000 N of thrust using the selected propellants. A list of operations to be performed before, during and after a complete combustion test is presented at the end of the document, together with a preliminary design of a Digital Control and Instrumentation System software. Due to time limitations, the software could not be implemented in a development program nor tested with simulated parameters as part of this thesis project.

The current trend in aircraft design is to increase the proportion of fiber composites in the structures. Since many primary parts also are constructed using metals, the number of hybrid metal-composite structures is increasing. Such structures have traditionally often been avoided as an option because of the lack of methodology to handle the mismatch between the material properties. Composite and metal properties differ with respect to: thermal expansion, failure mechanisms, plasticity, sensitivity to load type, fatigue accumulation and scatter, impact resistance and residual strength, anisotropy, environmental sensitivity, density etc. Based on these differences, the materials are subject to different design and certification requirements. The issues that arise in certification of hybrid structures are: thermally induced loads, multiplicity of failure modes, damage tolerance, buckling and permanent deformations, material property scatter, significant load states etc. From the design point of view, it is a challenge to construct a weight optimal hybrid structure with the right material in the right place. With a growing number of hybrid structures, these problems need to be addressed. The purpose of the current research is to assess the strength, durability and thermo-mechanical behavior of a hybrid composite-aluminum wing structure by testing and analysis. The work performed in this thesis focuses on the analysis part of the research and is divided into two parts. In the first part, the theoretical framework and the background are outlined.Significant material properties, aircraft certification aspects and the modeling framework are discussed.In the second part, two papers are appended. In the first paper, the interaction of composite and aluminum, and their requirements profiles,is examined in conceptual studies of the wing structure. The influence of the hybrid structure constitution and requirement profiles on the mass, strength, fatigue durability, stability and thermo-mechanical behavior is considered. Based on the conceptual studies, a hybrid concept to be used in the subsequent structural testing is chosen. The second paper focuses on the virtual testing of the wing structure. In particular, the local behavior of hybrid fastener joints is modeled in detail usingthe finite element method, and the result is then incorporated into a global model using line elements. Damage accumulation and failure behavior of the composite material are given special attention. Computations of progressive fastener failure in the experimental setup are performed. The analysis results indicate the critical features of the hybrid wing structure from static, fatigue, damage tolerance and thermo-mechanical points of view.