Experimental testing of attitude determination systems still plays an important role, despite increasing use of simulations. Testing provides a means to numerically quantify system performance, give confidence in the models and methods, and also discover and compensate for unexpected behaviours and interactions with the attitude determination system. The usefulness of the test results is dependent on an understanding of the uncertainties that contribute to the attitude error. With this understanding, the significance of the results can be assessed, and efforts to reduce attitude errors can be directed appropriately. The work of this thesis is to gain a quantitative understanding of the uncertainties that impact the attitude error of low cost spinning spacecraft using COTS camera (as Sun sensor) and MEMS magnetometer. The sensors were calibrated and the uncertainties in these calibrations were quantified, then propagated through the Triad method to uncertainties in the attitude. It was found that most systematic errors were reduced to negligible levels, except those due to timing latencies. Attitude errors achieved in the laboratory with the experimental setup were around 0.14 degrees (3σ) using either the Triad, q-method or Extended Kalman Filter with a gyro for dynamic model replacement. The errors in laboratory were dominated by magnetometer noise. Furthermore, correlated systematic errors had the effect of reducing the attitude error calculated in the laboratory. For an equivalent Sun-mag geometry in orbit, simulation showed that total attitude error would be of the order of 0.77 degrees (3σ). An uncertainty contribution analysis revealed this error was dominated by uncertainties in the inertial magnetic field model. Uncertainties in knowledge of the inertial Sun model, sensor calibration, sensor alignment and sensor noise were shown to be insignificant in comparison.

Polar Mesosphere Summer Echoes (PMSE) are strong radar echoes observed from altitudes of 80-90 km in polar regions, during summer time. PMSE are closely related to the fascinating atmospheric phenomenon known as noctilucent clouds (NLC). Since it has been suspected that NLC could respond to climate change in the mesosphere, they have attracted considerable interest in the scientific community during recent years. However, continuous visual or photographic NLC observations suffer from weather restrictions and the human factor. In contrast, PMSE radar measurements can easily be made over a long interval and are very attractive for long-term studies of the atmospheric parameters at the polar mesopause. This thesis uses the world’s longest data set of PMSE observations made by the same radar at the same place. Since 1997 these measurements have been carried out with the 52 MHz ESRAD MST radar located near Kiruna in Northern Sweden. The data set for 1997-2008 has been used for studies of diurnal, day-to-day and year-to-year variations of PMSE. We showed that PMSE occurrence rate and volume reflectivity on a daily scale show predominantly semidiurnal variations with the shape of the diurnal curves remaining consistent from year to year. We found that day-to-day and inter-annual variations of PMSE correlate with geomagnetic activity while they do not correlate with mesopause temperature or solar activity. We did not find any statistically significant trends in PMSE occurrence rate and length of PMSE season over 1997-2008. The thesis also presents also a new, independent calibration method, which can be used to estimate changes in transmitter output and antenna feed losses from year to year (for example due to changes of antenna configuration) and allows making accurate calculations of PMSE strength. This method is based on radar-radiosonde comparisons in the upper troposphere/lower stratosphere region simultaneously with PMSE observations. Using this calibration we calculated the distribution of PMSE strength over magnitudes; it varies from year to year with the peak of the distribution varying from 2×10−15 to 3×10−14 m−1. We found that inter-annual variations of PMSE volume reflectivity strongly correlate with the local geomagnetic k-index and anticorrelate with solar 10.7 cm flux. We did not identify any significant trend in PMSE volume reflectivity over 1997–2009. Finally, using 11 years of measurements, we calculated in-beam the PMSE aspect sensitivities using the FCA technique. We showed that half of PMSE detected each year cannot be explained by isotropic turbulence since they are highly aspect sensitive echoes. The distribution of these echoes remains consistent from year to year with median values of aspect sensitivity from 2.9 to 3.7°. The remaining half of the PMSE have aspect sensitivity parameters larger than 9-11°. We found that PMSE aspect sensitivity has altitude dependence: the scatter becomes more isotropic with increasing height. We did not identify any dependence of PMSE aspect sensitivity on backscattered power for any year. We analysed limitations of the in-beam and off-zenith beam methods and concluded that the former is suitable for highly aspect sensitive echoes while the latter is needed for more isotropic scatterers. / <p>Godkänd; 2011; 20110926 (marsmi); DISPUTATION Ämnesområde: Rymdteknik/Space Technology Opponent: Professor Patrick Joseph Espy, Dep of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway, Ordförande: Docent Evgenia Belova, Swedish Institute of Spaces Physics, Kiruna Tid: Måndag den 31 oktober 2011, kl 10.00 Plats: Aulan, Swedish Institute of Spaces Physics, Kiruna</p>

For each generation of electronic equipment there is a trend towards higher power den-sities. Increased heat generation is an undesired consequence that the thermal design unit in a company must handle. The goal of thermal design engineer/unit is to utilizethe same volume to more efficiently transfer more heat from the equipment. This can bedone by exploring more complex and advanced heat sink geometries, optimizing the finshapes and so on. The new prototypes developed will be tested for their reliability and endurance in special chambers called climate chambers, that simulate desired environ-ments. The measurements by thermal design teams in these kind of climate chambers are mainly of outdoor products, whose cooling is based on natural convection. Forcedcooling using fans is optional for these outdoor products. The climate chambers in general provides temperature measurement as the outputto the analysis, though there are other important parameters that define the operationalfunctionality of an equipment. The ability to visualize the flow characteristics duringthe process of testing is a valuable aid in the design process. A virtual/CFD form of thephysical climate chamber (CC) would empower the design process, while alleviating theusage of the climate chambers for such analyses. CFD offers a wide range of capabilitiesthat lets the user change the boundary conditions with great ease compared to that ofthe experimental setup. The numerical model developed in this thesis project provides results, that help inunderstanding the physics involved in fluid flow inside the physical climate chamber.Turbulence quantification of the flow is the main aim of this thesis project, which wouldbe resourceful in future works. Experiments are conducted inside the climate chamber, in order to aid the construction of numerical model as well as serve as source of vali-dation for the numerical results. Laminar transient case simulations are preferred over use of any turbulence models, to limit any kind of predictions made by these turbulencemodels. Integral length scales and turbulence intensities are compared and reason fordiscrepancies are addressed. The results from the comparisons show that, the numerical model emulates physicsof actual flow inside the climate chamber. However, there are many factors that directlyaffect the results, making it difficult to precisely quantify the error, within the time periodof this thesis project.

In this project, an algorithm has been proposed to detect a satellite’s maneuver by comparingthe orbital elements observed from the two line element data and the orbital elements propagatedwith the help of Simplified perturbations models. A set of TLE data for an object orbiting Earthcontains a specific set of orbital elements. Simplified perturbation are utilized to propagate theorbital velocity and position vector of the same object. By comparing the results obtained fromboth the methods, the maneuvers of a satellite are detected. This project outlines the workingmethodology and the implementation of the algorithm developed to detect the maneuvers. Thefunctioning of the technique is assessed with reference to two case studies for which the maneuverhistory is available by following the approach employed by Kelecy et al. (2007). The same methodis implemented to detect the orbit controlling maneuvers as well as the fine control maneuvers. Theresults derived from the analysis indicate that the maneuvers which has the magnitude of even aslow as cm/s has been detected when the detection parameters are calibrated properly.

One of the challenges that satellites face is the interaction between control movement and vibration of flexible appendages such as solar arrays and antennas that can negatively affect the performance of the spacecraft. The aim of this thesis is to develop a numerical model of a solar panel structure for KNATTE, a frictionless platform developed by the Onboard Space Systems group at Luleå University of Technology, and develop a control law that reduces the flexible vibration of the solar arrays when attitude control manoeuvres are performed. A set of solar panel structures have been designed and tested, the mathematical model of the multibody system, which consists of KNATTE and two flexible solar panels, has been developed in MATLAB by applying the finite element method. A finite element analysis has been performed in MATLAB to extract the natural frequencies of the system. The model has been numerically verified using a commercial software, and experimentally verified by performing testing on the frictionless vehicle, KNATTE, equipped with the solar panel structures and a number of piezoelectric sensors. Once the model has been verified, a Linear Quadratic Gaussian (LQG) controller has been developed using the results from the finite element model in order to reduce the amplitude of the vibrations of the flexible solar panel structure. The behaviour of the system has been simulated when the spacecraft performs an attitude manoeuvre. The finite element model provides the modal behaviour of the multibody system, obtaining its natural frequencies with low relative error. The LQG controller reduces the amplitude of the vibrations of the flexible solar panel structure.

This thesis aim to provide SSC, Swedish Space Corporation, with a foundation for understanding the key ideas behind water injection during rocket lift-off, including problems to be avoided when simulating the phenomena. This investigation focus on finding approaches suitable for obtaining a rough estimate of the reduction in noise generation, when too expensive equipment required is absent. The main idea was to compare different methods at the end as an alternative suitable way of verifying, since validation data was not available. The setup of the simulations consisted of two cases, one with water injection and the second case was without, and they were simulated the OpenFOAM software while the mesh was constructed using the GMSH software. A 1D analytical prediction model was computed using Matlab to estimate the noise generated. The result of the simulation showed an error of approximately 300-400 m/s within the rocket engine when compared to the Rocket Propulsion Analysis (RPA) software result. The maximum sound pressure level without water injection (SPL) from the analytical prediction model, ended up at approximately 172dB as well as 164dB depending on where it was "recorded". The maximum SPL with water injection was approximately 7dB lower in both recorded locations which was achieved by using optimal initial values. The biggest error observed by researches using this prediction model is approximately +2 dB above the real value. However, the error from this specific setup could not be estimated. The challenges and approximations encountered throughout this investigation is thoroughly discussed within the thesis and despite the absence of accurate results this investigation provides a thorough insight into water injection during rocket lift-off, with the potential of achieving better results using a more advanced solver in OpenFOAM.

Computational Fluid Dynamics has become a versatile product development tool, bringing many advantages to the conceptual design phase of products, and is being used for a wide variety of applications. In this thesis, the aerodynamics of a UAV with internal radar has been investigated. UAV is an acronym for Unmanned Aerial Vehicle, that is an aircraft which is flown with no human pilot onboard the aircraft, maneuvering the flight controls. The studies conducted throughout this thesis aimed at conducting numerical simulations of two UAV wing designs, through the utilization of the Vortex Lattice Method and Computational Fluid Dynamics. A number of different flight cases were investigated for comparing the two wing designs with respect to their aerodynamic characteristics, as well as a sustained turn analysis for the second UAV wing design. The analyses were conducted by importing provided UAV CAD-models into the numerical software, setting up appropriate grids, and running the simulations at the flight cases of interest. The results gathered from the simulations concerning the first wing design demonstrated favorable flight characteristics at lower angles of attack, although at angles of attack greater than 5°, flow separation was apparent. Regarding the results concerning the second wing design, it could be flown at greater angles of attack without experiencing flow separation, while decreasing the total drag of the UAV. For the sustained turn analysis concerning the second wing design, the aircraft generated sufficient lift at desired load factors, for maintaining its altitude however, it could not reach a trimmed state despite larger deflection angles of the ruddervators. Therefore the center of gravity position of the UAV was manipulated for sustaining the turns at desired load factors. Pressure contour plots were generated from the CFD simulations from which it could be determined that the front and nose of the aircraft could be further redesigned for decreasing aerodynamic drag.

This thesis looks at the SherpaTT planetary rover. The rover is a hybrid walking and driving rover that has been developed and built by DFKI and has already been deployed on several Mars analogue field studies. The SherpaTT rover wheels were found to become entangled in rocks during the last field deployment in Morocco. As human intervention would be impossible on Mars the aim is to reduce the possibility of rock entanglements by performing a mechanical redesign of the wheels. During this redesign care is taken to ensure the current traction, slip-resistance, weight and strength are not adversely affected. In addition, the durability of the wheels is investigated in terms of materials to review whether the current wheels are suitable for a mars deployment. An investigation into the grousers design results in a changed design that aims to both reduce rock entanglements and increase wheel performance by optimising the grouser height and number over several different wheel and terrain cases. Wheels are produced for four scenarios, a rigid wheel on hard ground, a rigid wheel on soft ground, a flexible wheel on hard ground and a flexible wheel on soft ground. A conceptual investigation into the wheel fork design is carried out to examine the effects of changing three properties of the wheel fork. The magnitude and location of the stress is compared for each. Materials are investigated resulting in the recommendation of several potential material choices which provide an increase in the overall strength and hardness. While SherpaTT is still in development the 6000 class of aluminium is recommended due to the relative ease with which it can be worked with. Once SherpaTT moves onto the final stages it is recommended that at least the grousers are made from the 7000 class of aluminium, which have higher levels of strength and hardness.

A modern ghter aircraft has an advanced ight control system which highly augmentsthe control inputs from the pilot. To verify a new iteration of the control system is a timeconsuming and expensive task. It is desired to nd qualities that is not satisfactory to thepilot as early as possible in the verication process to reduce the cost for design changes.The primary objective of this thesis is to develop methods that can be used for automaticalevaluation of aircraft ying qualities from the data provided by a desktop simulator. A desktopsimulator is cheap to use compared to ight tests and tests with a pilot in a simulator.Only ghter aircraft in the precision ight phase are studied however the methods developedcould easily be extended to include other types of aircraft and other phases of ight.To evaluate the ying qualities two sets of criteria are used the MIL-F-8785C standardand the Gibson criteria. The MIL-F-8785C standard uses a second order linear system toevaluate the aircraft's ying qualities. The linear system is estimated from the nonlineardata and evaluated against the MIL-F-8785C standard. The Gibson criteria studies the timeand frequency domain directly and are designed to work with highly augmented aircraft.The set of Gibson criteria used in this thesis primary evaluates data from the time domainhowever one criterion from the frequency domain is studied.The methods developed to evaluate the ying qualities from the MIL-F-8785C standardonly works for a small part of the ight envelope furthermore they show a large dierencefor what is considered acceptable ying qualities. Because of this the methods developed forthe MIL-F-8785C standard are considered not to be suited for evaluating ying qualities forhighly augmented aircraft. The methods developed to evaluate the ying qualities againstthe Gibson criteria works for a large part of the ight and also show a high accuracy. Thismakes the methods suited for evaluation of the ying qualities.

Cryocooling is a continuously developing field of engineering, applied in the fieldsof aerospace, military, and medical sciences among others. There is a demand forsmaller and more efficient cryocoolers for spaceborne low-light observation missions,with many custom cooling systems having completed successful missions. The Stir-ling cycle is the most prevalent refrigeration technique used for space applications,with the pulse-tube, Joule-Thomson or reverse Brayton cycles being used in somespecial cases.A matrix heat exchanger is designed with 3D-printed 17-4 PH stainless steel end capsstreamlined for computer numerical control (CNC) production. The heat exchanger (HX) core consists of 1mm thick stainless steel spacers and 250μm thick copperchips that are tolerance-matched for photo etching, as well as pyrolytic graphitesheets (PGS) of 25μm, the thickest commercially available PGS without addedadhesive film material.The experiments of joining PGS and copper chips with Epo-Tek 301-2 epoxy tocreate a solid core structure for the heat exchanger did not result in a pressure-resistant laminate material. The graphite surface proved difficult to adhere to usingthis epoxy, creating voids, and easily delaminated into separate layers of PGS. Bond-ing the stack together using indium, testing epoxy with a higher ability to permeatethe PGS or diffusion-bonding through other means are presented as options forfurthering the HX development.Pressure testing of a copper-only laminated heat exchanger core showed that theend cap recess adhesion capability is a potential point of failure, as the designedstructure makes it impossible to inspect the results of the bond without curingthe epoxy and pressurising the system. The difficulty in establishing a tight seambetween the main counter-flow channels of the HX is also demonstrated here, asleakage between the channels occurred at pressures in the vicinity of 2