The expansion and increased complexity of technology is undoubtedly consistent and one can intuitively suppose that this trajectory will not deviate from this course in the years to come. On a continuous basis, concepts that started of as some hypothetical or abstract notions without practical relevance gets transferred to the modern state of our current technology. During these times, where a subset of our technology has the responsibility of handling the safety of our being, research within dependability theory must keep up the pace with technology. One cannot emphasize enough the importance of ensuring the validity of system dependability attributes prior and posterior to development. With the objective of aggregating findings to the research field and potentially derive new propositions this paper assesses the stochastic modeling concepts used within dependability theory. In particular, discrete-time-and continuous-time-Markov chains are outlined in detail, searching for possibilities to extend these processes in the context of real-time system monitoring. As an outcome, numerical 'repair rate optimization' (RRO) through CTMC uniformization is introduced. A technique which deduces a proposed allocation of repair rate adjustment based on the models parametric sensitivities (gradient ascent). The theoretical aspects are verified by development of an algorithm in Matlab that utilizes the above. Additionally, an approach of combining dependability attributes into a unified measure is proposed. Where the (bounded) transient probabilities are regarded as vectors in the L2(R, B(R), λ) Hilbert Space. For which a normalized dependability norm can be obtained by using the induced norm and triangle inequality. This serves as a metric to compare distinct architectures in terms of several, quantitative attributes. The results imply that under the hypothesis that the system/company can adapt to an increased demand on maintenance periodicity, reliability/availability can be significantly improved. Mitigating risk of failure while optimally preserving resources in terms of e.g. core capacity, maintenance personnel, budget and/or required redundancy while conditioning on the actual system behaviour.

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The entropy noise in modern engines is mainly originating from two types of mechanisms.First, chemical reactions in the combustion chamber lead to unsteady heat releasewhich is responsible of the direct combustion noise. Second, hot and cold blobsof air coming from the combustion chamber are advected and accelerated throughturbine stages, giving rise to the so-called entropy noise (or indirect combustionnoise). In the present work, numerical characterization of indirect combustion noiseof a Nozzle Guide Vane passage was assessed using three-dimensional Large EddySimulations. The study was conducted on a simplified topology of a real turbinestator passage, for which experimental data were available in transonic operatingconditions. First, a baseline case was reproduced to validate a numerical finite volumesolver against the experimental measurements. Then, the same solver is used toreproduce the effects of incoming entropy waves from the combustion chamber andto characterize the additional generated acoustic power. Periodic temperature fluctuationsare imposed at the inlet, permitting to simulate hot and cold packets of aircoming from the unsteady combustion. The incoming waves are characterized bytheir characteristic wavelength; therefore, a parametric study has been conductedvarying the inlet temperature of the passage, generating entropy waves of greaterwavelengths. The study proves that the generated indirect combustion noise canbe significant. Moreover, the generated indirect combustion noise increases as thewavelength of the incoming disturbances increases. Finally, the present work suggeststhat, in transonic conditions, there might be flow features which enhance theindirect combustion noise generation mechanism.

The performance of the auroral large imagining system (ALIS_4D) and an automatic track detection algorithm was evaluated for space debris surveillance and tracking. The evaluation of the ALIS_4D was done through a numerical simulation and data annotations, while the track detection results were manually evaluated. The effect of auroral conditions, filters, and the detection mode were evaluated for the performance of both.  It was found that  ALIS_4D can detect resident space objects. The peak detection rate per hour was dependent on the time of the year, day, and the limiting magnitude set by the filters and the sensor among others. The peak was simulated to be approximately 120 in January and 70 in April and September. A space object observation campaign was performed in April 2020 for 90 minutes. During that period across the used four stations 61 unique objects were detected and 37 unique objects were detected at the Abisko station, that was used for the simulation. During the observation time there was auroral activity which can block the line-of-sight to resident space objects.  The track detection algorithm was evaluated for data gathered in a dedicated space situational awareness (SSA) mode and other modes. In SSA mode, the algorithm found 60% of the subsections of the image with visible traces. The false detection rate was 17% when no auroras were present and 56% when there were. In other modes the evaluation was simplified due to large number of false positives. When assumed best case scenario 99.2% of the detections were false. The auroral activity and the used mode had the most significant effect on the track detection algorithm performance. It was found that in SSA mode the used filter did not effect on the track detection performance.

”The Eagle has landed”. With this words, astronaut Neil Armstrong, together with astronaut Edwin ”Buzz” Aldrin, confirmed the safe landing on the Moon of the Apollo11 on July 20th, 1969. This achievement would have never been possible without the engineering behind the construction of the Moon lander. One of the most innovative features installed aboard was the pintle injector, a specific type of injector capable of precise metering of the propellants into the combustion chamber, and capable of throttling. Furthermore, the pintle injector has demonstrated its inherent combustion stability andgood mixing properties over time. The current work serves as a feasibility study for the use of an electric motor as the actuator for the pintle. This paper is the result of a 9-month internship at ArianeGroup GmbH, which is investigating the use of a pintle injector as a back-up option for a future ESA lunar lander mission. A preliminary design of the pintle was already produced, and the scope of this work is the design of the mechanical linkages and the actuation of the injector, with the choice of the method of actuation, the electric motor and the necessary components.

The increasing number of space-related applications and the development of miniaturized satellites (sometimes called CubeSats) recently became an exciting area in modern space science. Due to their diverse applications, smaller size, and low development cost. More sophisticated CubeSat missions have been recently introduced, signaling that CubeSats have started to progress from solely technical demonstration platforms to providing opportunities for low-cost actual research missions with a highly promising benefit in terms of commercial revenue. Despite major advancements in CubeSat technology, there is still a range of fundamental concerns regarding CubeSat barriers, pitfalls, and commercial effects. From both an academic and an industrial perspective, this report offers a thorough overview of various facets of CubeSat manufacturing and launch costs. The latest trends in CubeSat were discussed as well as an analysis of the launch cost and other variables that could influence the mission. An information-gathering approach was used from various proposed and launched missions, including journal articles, the official space mission webpages, and other publicly accessible satellite databases. Using data collected from various sources, we found that the latest launching price for future missions is influenced and modeled by various reasons. The Liquid propellant, miniaturized thrusters for small satellites, and modernized payload carriers could play a part in lowering the cost of potential launches. For instance, the RP-1 fuel used in Falcon 9 is expandable and reusable, increasing launch opportunities and low per-unit launch costs. Likewise, tiny satellites with miniaturized thrusters will significantly help change aerodynamics and launch processes. Whereas systemic payload structures can bear maximum weight, theoretically expanding the number of Nanosatellites deployed per launch. This paper attempts to facilitate various elements that make it practical in enabling a decision-making process related to technical aspects of the launch cost and future utilization of CubeSat technology.

The understanding of developing boundary layers over wings is an important topic from the perspective of industrial applications. An increased understanding would be consequential not only for achieving higher fuel efficiency but also in the design of aircraft control strategies. With these aims in mind, the current work aims to further the understanding of developing boundary layer over wingsections. The study is performed with two particular perspectives in mind -unsteady aerodynamic effects in a pitching airfoil and turbulent boundary layerstructure in non-equilibrium boundary layers over a stationary airfoil.The boundary layer evolution in unsteady natural laminar flow airfoils undergoing small-amplitude pitch-oscillations is investigated. For high Reynolds numbers the origins of the non-linear unsteady aerodynamic response of laminar airfoils is explained on the basis of quasi-steady assumptions. Temporal nonlinearitiesin aerodynamic forces are shown to be inherently linked to thenon-linearities of static aerodynamic force coefficients and that a simple phaselagconcept can model the observed non-linear unsteady response. On the other hand at lower Reynolds numbers, when there exists an unstable leading edgelaminar separation bubble, the unsteady response is dynamically rich and changes in boundary layer characteristics can be abrupt. Such quasi-steadyphase-lag concepts are no longer appropriate to explain the unsteady flow physics in such a case. For the case of stationary airfoils, flow statistics for flow around an airfoil at two different Reynolds numbers are compared to assess Reynolds number effects in non-equilibrium flows. Pressure gradient effects found to be stronger at low Reynolds numbers, leading to higher energy in the larger structures present  in the outer part of the turbulent boundary layer. / <p>QC 20171121</p>

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The primary objective of this master's thesis is to examine a new version of a power unit currently utilized in an unmanned aerial vehicle and develop a simulation model of the power unit. The theoretical groundwork needed for developing a model has been presented, describing components used and the function of the different subsystems. The development of a model is done in the simulation environment of Simscape. Measurements were preformed on the physical prototype of the power unit. These measurements were used to verify the simulation. The results of the simulations and the measurements are presented at the end of the thesis, confirming the simulation model's validity.

In this thesis a Large Eddy Simulation (LES) of a hybrid rocket engine burning ethylene (C2H4) in nitrous oxide (N2O) is explored. This is done primarily using a solver and solution scheme provided by the Swedish Defence Research Agency (FOI) and an (at this date) unpublished chemistry model. This sheds light on some transiet behaviour of a prior experiment conducted with a model engine that the simulation was based on. Due to time constraints the simulation did not cover the full test of the engine. The results confirm predictions from the experiment that the propellant was fuel rich. Some insight on how oxidizer swirl propagates throughout the engine was discovered as well.