There are special effects in spectroscopy that must be considered in order to fullyexplain how molecular oxygen interacts with radiation in planetary atmospheres.One of these, the Zeeman effect, is described in this thesis. The Zeeman effect is the theory by which energy levels of atoms and molecules are altered by magnetism, and it causes both polarization and line shape to change. The first publication attached to this thesis, Paper I, details the technical and practical implementation of the Zeeman effect in a radiative transfer model. One potential use of magnetically altered spectroscopy is to remotely measure magnetism. Paper II discuss a method for such measurements on weakly magnetized planets by measuring the polarization caused by the Zeeman effect. The article brings up Mars as one potential candidate to utilize the method. To introduce the articles properly, the thesis starts with a shortdescription of the underlying basic theory for radiative transfer and spectroscopy.After the theory chapter, a short description of input necessary to utilize the theory on operational and experimental platforms is presented.

This thesis is composed of three articles, which have the common denominator that they are studies of heating of oxygen ions in the high altitude cusp and mantle in the terrestrial magnetosphere. All data analysis are based on observational data from the Cluster satellites. Oxygen ions originate in the ionosphere, from where they flow up along open cusp field lines. This upflowing ionospheric plasma is generally gravitationally bound and will return as ionospheric downflow. However, if the plasma is sufficiently energized it may overcome gravity and reach the magnetosphere. Further energization is able to put the plasma on trajectories leading downstream along the magnetotail, which may cause the plasma to escape into the magnetosheath. This thesis considers energization of oxygen ions through wave-particle interactions. We show that the average electric spectral densities in the altitude range of 8-15 Earth radii are able to explain the average perpendicular temperatures, using a simple gyroresonance model and 50% of the observed spectral density at the O+ gyrofrequency. We also show that the phase velocities derived from the observed low frequency electric and magnetic fields are consistent with Alfvén waves. Strong heating is sporadic and spatially limited. For three case studies of strong heating, we show that the regions of enhanced wave activity are at least one order of magnitude larger than the gyroradius of the ions, which is a 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. Three events of very high temperatures and simultaneously observed high spectral densities were studied, and we showed that the temperatures could be explained with the simple gyrofrequency model. We have also provided average diffusion coefficients at different altitudes, which can be used for ion heating and outflow modeling.

Mars is an unmagnetized planet. Mars has no intrinsic magnetic field but has local magnetic anomalies in the crust. The solar wind, which is the plasma flowing from the Sun at supersonic speed, interacts with the magnetic fields of the currents induced in the conductive Martian ionosphere, deviates and slows down to subsonic speeds. A void in the solar wind is formed around the planet as an induced magnetosphere.At the boundary of the induced magnetosphere, the plasma composition changes from being dominated by the major ion in the solar wind (protons) to being dominated by heavy ions of planetary origin. Also, the interplanetary magnetic field, being carried by the solar wind, starts to pile up against the planet to form a magnetic barrier on the dayside, drapes around the planet, stretches due to mass loading, and forms a magnetotail.The gyroradius of a heated proton in the magnetosheath is large in comparison with the size of the induced magnetosphere. Therefore, a fraction of the proton population penetrates the induced magnetosphere boundary, enters the upper layer of the atmosphere (the ionosphere) and subsequently neutralizes at low altitudes. We have conducted a detailed study of an event, in which the magnetosheath protons penetrate the Martian induced magnetosphere boundary (IMB). The spatial extent of the proton precipitation region reached several thousands of kilometers along the orbit of the Mars Express spacecraft.The interaction of the precipitating protons with the Martian atmosphere was modeled using a direct simulation Monte Carlo method. The inclusion of a horizontal magnetic field in the model significantly increased the backscattering of protons compared to the case without a magnetic field. More than 50% of the incoming energy is reflected backwards for a magnetic field of strength 30 nT, compared to 4% in the case of no magnetic field. We have also used hybrid modeling to study the spatial pattern of the precipitation onto the Martian atmosphere both for solar wind protons and protons originating from the planetary atmosphere. The solar wind protons and the exospheric (planetary) protons contribute 60% and 40%, respectively, of the deposition of mass at the exobase for the given input parameters. The precipitating flux decreases substantially at the subsolar point, due to the backscattering of the incoming protons by the more intense piled-up magnetic field.

The powered soft landing of a spacecraft represents a maneuver with high interest, withsome private launcher companies – SpaceX, Blue Origin, Rocket Factory Augsburg, etc. - showinginterest in implementing it as a solution for their launchers, and several national agenciesusing it for the exploration of celestial bodies where it may be the only option. This thesispresents the work done in the theoretical development of a possible control algorithm for thepower landing maneuver of a rocket on Earth’s surface. The first step is the definition of the landingmaneuver based on literature study. This includes the identification of the different phasesof the flight, the selection of control variables, and the establishment of the initial conditionsfor the simulation and the working assumptions. Following this work, the three-dimensionalequations of motion for a rocket-like body are determined and simulated in the absence of anycontrol signal. Two aspects need to be analyzed in the powered landing maneuver: attitudeand velocity control. The second step consists in the implementation of the two respectivealgorithms, which are then applied to the equations system. The newly controlled system isagain simulated, and the results are compared with the ones obtained in the absence of thecontrol. The simulations are expected to provide the position, attitude, and velocity profilesof the rocket both in free fall and with a controlled power-landing. Consequently, the controlsystem is expected to guarantee safe recovery of the spacecraft given different initial conditions.

For transport aeroplanes the Blended-Wing-Body (BWB) configuration shows promise in improving aerodynamic efficiency. The Green Raven project strives to demonstrate hydrogen fuel-cell-electric propulsion on a 4 m wingspan BWB. Due to the lack of a traditional horizontal tailplane, BWBs commonly have multifunctional control surfaces that void assumptions needed for traditional sizing methods. This work endeavoured to produce a control surface configuration that would permit adequate flying qualities of the Green Raven according to the MIL-F-8785C specification, preferably while minimising cruise power draw. The open-source aerospace modelling and optimisation environment SUAVE was chosen for the task, with the intention of adding any needed functionality.SUAVE was modified to permit the definition of general-purpose control surfaces and stability derivatives to be obtained for the additional degrees of freedom they bring which was demonstrated using a SUAVE representation of the Green Raven. The precise procedure for airworthiness-constrained control surface optimisation could not be determined before cessation of work but an outline of a simplified procedure was proposed. / Flygplan med sammansmält vinge och flygkropp (Blended-Wing-Body, BWB) har potential att nå lägre energiförbrukning. På KTH har projektet Green Raven som mål att demonstrera framdrivning med vätgasdrivna bränsleceller på ett obemannat flygplan med denna konfiguration och en spännvidd på 4 m. Då flygplanskonfigurationen BWB saknar konventionell stabilisator är rodren längs vingens bakkant i regel multifunktionella vilket invaliderar beprövade metoder för dimensionering. Detta arbete hade som mål att ta fram en roderkonfiguration till Green Raven-projektet som medger tillfredställande flygegenskaper i enighet med MIL-F-8785C, helst samtidigt som effektbehovet i planflykt minimeras. SUAVE, ett open-source-verktyg för modellering och optimering av flygfarkoster, valdes för uppgiften i vetskap om att vissa kodändringar skulle krävas.SUAVE modifierades för att medge modellering av multifunktionella roder och de extra frihetsgrader de medför vilket demonstrerades genom att ta fram stabilitets- och roderderivator för en modell av Green Raven. En procedur för optimering med krav på flygegenskaper som bivillkor kunde inte färdigställas i tid men en förenklad procedur föreslås.

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. / En minskning av den globala användningen av fossila bränslen är nödvändig i strävan efter en mer hållbar framtid. En nyckelstrategi i övergången från fossila bränslen är elektrifiering. Denna strategi är särskilt framträdande inom transportsektorn, där effektivare sätt att lagra elektrisk energi eftersträvas. Strukturella batterikompositer representerar en lovande teknik. Genom att vara baserade på multifunktionella kompositmaterial som har förmåga att bära mekaniska belastningar och lagra elektrisk energi samtidigt, ger de en "masslös" energilagring. Detta arbete syftar till att utveckla ett formförändrande strukturellt batteri som kan böjas uppåt och nedåt i en fribärande uppsättning. Det strukturella batteriet är tillverkat av flera beståndsdelar. Två yttre lager av kolfibrer fungerar som negativa elektroder och ett mellanlager av aluminiumfolie belagd med NMC622 på båda sidor fungerar som positiva elektroder. Dessutom separerar ett glasfiberlager och en keramisk separator de positiva och negativa elektroderna. En strukturell batterielektrolyt används för att bädda in laminatet för att ge lastöverföring och jonöverföring. Från denna uppsättning är det möjligt att kontrollera lithieringen/delithieringen av varje kolfiberlager oberoende och därigenom böja laminatet i önskad riktning. Därefter modelleras systemet både analytiskt med Matlab och numeriskt med Comsol Multiphysics 6.1. Från modellerna visar det sig att systemet i teorin är kapabelt till stora deformationer, vilket visar lovande resultat. De experimentella laminaten visar emellertid låg kapacitet vid cykling, vilket skulle orsaka nästan inga deformationer. Systemets dåliga prestanda kan vara kopplat till inkompatibilitet mellan den strukturella batterielektrolyten och NMC622.

Recently, novel experimental evidence of continuous rotating detonations for gaseous H2/O2 propellants with a rotating detonation rocket engine (RDRE) was attained on the 3-inch Air Force Research Laboratory (AFRL) Distribution A RDRE, with the fuel and oxidizer injectors modified for H2/O2 gas propellants. Evident in previous experiments, detonation instabilities arising from upstream deflagration, from recirculation zones, and from insufficient gas mixing challenged resolution of detonation wave behavior from back-end imaging with the available optical equipment. Images were often over-illuminated from both the high amount of deflagration in the plume and the higher density of detonation waves in the annulus coupled with the small detonation cell size for H2/O2 gas propellants. Additionally, conventional optical systems attenuate the ultraviolet (UV) emission range (~308-320 nm wavelength) from the primary combustion species. To overcome these challenges are two methodologies that still utilize optical back-end imaging: (1) CH* chemiluminescence with fuel doping, and (2) OH* chemiluminescence. The first methodology utilizes doping CH4 into the H2/O2 gas mixture at a relatively small concentration of up to 5% by total mass flow rate to leverage CH* chemiluminescence at 409 ± 32 nm wavelength. The second methodology utilizes the combination of an OH* bypass filter for 308–320 nm wavelength to filter other emissions and an intensifier to amplify the detonation wave OH* emission. As of the present research, the first methodology was investigated across a regime of operating conditions, with planned future testing outlined to facilitate comparable data acquisition utilizing the second methodology.

Thermal management is a crucial part in the aviation industry. It is also essential that the components involved in aviation be light weight. One of the vital components of thermal management is heat exchangers. It has been observed that the optimization of the heat exchanger is approaching its saturation with traditional manufacturing. To overcome this challenge engineers are exploring the new revolutionary technology of additive manufacturing. Additive manufacturing has created the opportunity of design freedom for the optimization of heat exchangers with complex heat exchanger microchannels and optimized fin designs.This project essentially focuses on generating complex heat exchanger cores with organic lattice structures such as Triply periodic minimal surface (TPMS) geometry. Evaluation of the heat exchanger core has been done using computational fluid dynamic analysis and a comparative study is done to choose the most suitable geometry for the fluid-fluid heat exchangers. A static thermal evaluation of the strut-based lattice structure has been conducted for fin designs and support structure to be used in laser powder bed fusion technology. Additionally, the selected geometry from the analysis has been incorporated into a demonstrator product. The key limitation of this process has been addressed in this project.

The goal of this dissertation is to introduce a method of fault diagnosis that is designed to cope with fault signature variability, the main source of difficulty for the existing diagnostic systems. This method is a non-parametric pattern classifier that uses a multi-valued influence matrix (MVIM) as its diagnostic model. In this method, process abnormalities are detected through processing the sensory data and flagging, and diagnostic reasoning is performed by matching the flagged measurements against the columns of the influence matrix. Fault signature improvement is achieved by a Flagging Unit, which is tuned based on a training set. This unit is shown to have the ability to improve detection, reduce false alarms, and enhance diagnostics. The improved fault signatures by the Flagging Unit are also shown to be beneficial to other classifiers such as the Bayes classifier and artificial neural nets. The applicability of the MVIM method is investigated in fault diagnosis of a helicopter gearbox. A total of five tests were performed, during which eight failures occurred. In order to enhance the effect of the failures on the vibration data, the vibration signals obtained from the gearbox were digitized and processed by a vibration signal analyzer. The parameters obtained from this signal analyzer were then utilized to train the MVIM method and test its performance for both detection and diagnosis. The averaged values of the parameters obtained from individual accelerometers were used to reduce the processing time. Training sets were formed based on parameters from various combinations of the five tests, and the MVIM method was tested based on the parameters from all of the five tests. Detection results indicate that the MVIM method provided excellent results when the full range of faults' effects on the vibration measurements were included in the training set. The MVIM method was also utilized to rank the parameters for their significance in detection. It is shown that through this ranking the optimal subset of parameters for detection can be selected, which is particularly important in reducing processing time for on-line detection. For diagnosis, the MVIM method was used in a hierarchical manner. The parameters from individual accelerometers were first processed through detection MVIMs, to trigger the presence of a fault, and then examined by diagnostic MVIMs to identify the fault. Diagnostic results show that the MVIM method had a correct diagnostic rate of 95% for the faults included in training. (Abstract shortened by UMI.)

Optimal trajectory design has been extensively studied across multiple disciplines adopting different techniques for implementation and execution. It has been utilized in past space trajectory missions to either optimize the amount of fuel spent or minimize the time of flight to meet mission requirements. Coupled Radial Basis Functions (CRBFs) are a new way to solve these optimal control problems, and this thesis applies CRBFs to spacecraft trajectory optimization design problems. CRBFs are real-valued radial basis functions (RBFs) that utilize a conical spline while also not being affected by the value of the shape parameter. The CRBF approach is applied to nonlinear optimal control problems. We adopt the indirect formulation so that the necessary and boundary conditions are derived from the system dynamical equations. As a result, a set of nonlinear algebraic equations (NAEs) is generated. The NAEs are then solved using a standard solver in MATLAB and the results are produced. CRBFs do not rely heavily on initial extensive analysis of the problem, which makes it very intuitive to use. The states, control, and co-states are defined as the equations to be solved and approximated using CRBFs. The results show that CRBFs can be applied to space trajectory optimization problems to produce accurate results across state and costate variables on uniform user defined nodes across the simulation time.