M.Ing. / This dissertation is intended to make a contribution to the engineering intellectual pool of knowledge by offering a perspective on the subject of software development that encompasses safety (i.e. quality, qualification and reliability). Software development will be examined in light of developments made in recent years in three engineering disciplines: quality, qualification and reliability. These developments will be infused into an established system engineering process currently in use in Denel Dynamics (referred to as ‘the organization’). This dissertation will probe how the concept of software quality is addressed and ensured in the organization. With the aid of current (best) practices and processes; techniques and systems, the author intends to present a different perspective on the development of quality software products from the current view of the organization, by addressing software safety, reliability and cost. The author believes that software quality, with particular emphasis on reliability, if systematically administered in a structured and controlled manner in an organization, will yield products for global markets that are both safe and cost-efficient. In the following chapters, software reliability will be discussed in detail in a quantitative and/or qualitative manner to explain the case presented. It is envisioned that the information collated in this dissertation will be used by all involved in the software product life cycle, such as first-time programme or project managers, programmers and decision makers, to help make informed decisions that will ensure the organization realizes the best return on its investment.

How an aircraft performs its approach and descent towards an airport today has got big potential for improvements. It's mainly the environmental impact and safety that can, and must, be improved for a sustainable future in aviation. "Green Approaches" is a small, yet relatively well-known, optimized approach system mainly used by Scandinavian Airlines on Arlanda airport. Unfortunately "Green Approaches" aren't used often enough, due to the simple reason that it doesn't work very well during heavy traffic. Luckily further research is being done in this field to further optimize an aircraft’s approach. As of today, the most forward going research is being done by the FAA and NASA, and their new system is called NextGen OPD. The system is not fully developed yet but their goals are, as previously mentioned, to optimize today's aircraft approach. In this report the focus will also be set on improving aircraft approaches, although not by optimizing today’s system like the FAA and NASA. Instead, a whole new concept of how aircraft approach airports will be developed. The reason that a brand new concept will be developed is simple, optimizing today's aging system will not be sustainable for the future. Also, optimizing an aging system has its limits. By designing a whole new concept, a steady ground will be laid and it shall be sustainable for the coming century's technology. The new concept will be called ”C.C.D.D.”, Computer Controlled Direct Descent, and will have a lot of goals and expectations to fulfill. As hinted in the name, the new concept is built on the idea that a computer will be controlling the whole approach, and therefore the "Human factor" will more or less be eliminated. Although the main purpose of a new approach system is to decrease the negative environmental impact, by decreasing the fuel consumption during the approach. The new concept will also decrease the noise an aircraft makes during the descent and increase the possibility for a greater traffic flow in the airport’s airspace. The end result will be a "win-win" for everyone involved. An environmentally friendly aircraft approach is necessary for a sustainable future in aviation. C.C.D.D. is a system that will pay for itself with time, because of the decreased fuel consumption for airliners. The system also has the ability to be expanded to computer control departing aircrafts, due to the systems highly computerized structure and integration with airplanes autopilot.

<p> As aircraft are designed to a greater extent on computers, the need for accurate and fast CFD algorithms has never been greater. The development of CFD algorithms requires experimental data against which CFD output can be validated and from which insight about flow physics can be acquired. Skin friction, in particular, is an important quantity to predict with CFD, and experimental skin friction data sets aid not only with the validation of the CFD predictions, but also in tuning the CFD models to predict specific flow fields. However, a practical experimental technique for collecting spatially and temporally resolved skin friction data on complex models does not yet exist. This dissertation develops and demonstrates a new luminescent oil film skin friction meter which can produce spatially-resolved quantitative steady and unsteady skin friction data on models with complex curvature. </p><p> The skin friction acting on the surface of a thin film of oil can be approximated by the expression &tau;<i>_w</i> =&mu;<i>_o</i><i>u_h/h</i>, where &mu;<i>_o</i> is the dynamic viscosity of the oil, <i>u_h</i> is the velocity of the surface of the oil film, and <i>h</i> is the thickness of the oil film. The new skin friction meter determines skin friction by measuring <i>h</i> and <i>u_h</i>. The oil film thickness <i>h</i> is determined by ratioing the intensity of the fluorescent emissions from the oil film with the intensity of the incident light which is scattered from the surface of the model. When properly calibrated, that ratio provides an absolute oil film thickness value. This oil film thickness meter is therefore referred as the Ratioed-Image Film-Thickness (RIFT) Meter. The oil film velocity <i>u_h</i> is determined by monitoring the evolution of tagged molecules within the oil film: Photochromic molecules are dissolved into the fluorescent oil and a pattern is written into the oil film using an ultraviolet laser. The evolution of the pattern is recorded, and standard cross-correlation techniques are applied to the resulting sequence of images. This newly developed skin friction meter is therefore called the Luminescent Oil Film Flow-Tagging skin friction meter, or the LOFFT skin friction meter. The LOFFT skin friction meter is demonstrated by collecting time-averaged skin friction measurements on NASA's FAITH model and by collecting unsteady skin friction measurements with a frequency response of 600Hz. Higher frequency response is possible and is dependent on the experimental setup. </p><p> This dissertation also contributes to the work done on the Global Luminescent Oil Film Skin Friction Meter (GLOFSFM) by noting that the technique could be influenced by ripples at the oil-air interface. An experiment studying the evolution of ripples at the oil-air interface was conducted to determine under what oil film conditions the GLOFSFM can be appropriately applied. The RIFT meter was crucial for this experiment, as it facilitated quantitative distributed oil film thickness measurements during the wind-tunnel run. The resulting data set is rich in content, permitting the computation of mean wavelengths, peak-to-trough ripple heights, wave speeds, and mean thicknesses. In addition to determining under what oil film conditions the GLOFSFM may be applied, this experiment directly determined the oil film conditions under which the velocity of the ripples may be used to proxy the velocity of the oil film surface. The RIFT meter and the ability to determine oil film surface velocity by monitoring ripple velocities admit yet another time-averaged skin friction meter, the Fluorescent-Oil Ripple-Velocity (FORV) skin friction meter. The FORV skin friction meter recovers skin friction as &tau;<i>_w</i> = &mu;<i>_ov_rip/H</i>, where <i> v_rip</i> is the velocity of the ripples, and <i>H</i> is the oil film thickness averaged over the thickness fluctuations due to the ripples. The FORV skin friction meter is demonstrated on NASA's FAITH model.</p><p>

The main objective of this thesis was to improve the simulation model of a subscale fighter demonstratorthat had been developed previously. In order to give a reliable result, the simulation model should be modeled correctly and employ accurate input. To fulfill this objective two approaches was performed, the first was by providing the aerodynamic derivatives database in order to be implemented  in the simulation model, and the second process is to improve the propulsion module of the  simulation model. The aerodynamic database was generated by several VLM and panel  method software, namely Tornado, VSPAero and XFLR5, which uses subscale fighter  demonstrator called Generic Future Fighter  (GFF) as the aircraft model. The results from  different methods and software were then compared first before it was implemented to the  simulation model. The second process includesenhancing the propulsion model and implementation of the aerodynamic database.The propulsion model enhancement covers the improvement of thrust modeling and development of fuel consumption model. Additionally, the aerodynamic database implementation was executed by connecting the  external sets of the database into the simulation  model automatically. The verification process  was performed by comparing the result of the simulation model against recorded flight data, also by comparing the improved and the  previous simulation model result to see the effect of improvement that was carried out. Using the improved model of engine thrust and fuel consumption model, the propulsion module can produce a reliable outcome of forces and   moments computation. Moreover, theimplementation of the aerodynamic database  also gives a significant improvement in the simulation model result.

The use of advanced small-satellite platforms has become increasingly more popular in the recent years. Several private companies are investing enormous capital into constellations of small satellites that are designed to provide highly data-intensive global services, such as rapid Earth imaging or fast worldwide Internet access. The scientific community is also interested in the development of miniature and high throughput platforms, for instance in the area of microwave radiometry or hyperspectral imaging. The current state of the art nanosatellite radio frequency (RF) communications systems struggle to keep up with the increasing downlink demand and satellite data processing capabilities. Laser communications (lasercom) offers various advantages: increased bandwidth, smaller size, weight, power consumption, and a license-free spectrum. While the narrow beamwidths allow lasercom to achieve higher data rates than RF, they, however, also result in higher pointing requirements for the spacecraft. Precision laser pointing systems have been successfully demonstrated on bigger satellites, but not on a nanosatellite scale, where the size and weight constraints are so severe. The Nanosatellite Optical Downlink Experiment (NODE) developed at MIT is a lasercom terminal designed to demonstrate the technologies required for a high-speed optical downlink using commercial off-the-shelf components within the constraints of a typical 3U CubeSat. NODE augments the bus attitude control system with a compact fine laser pointing stage to compensate for the spacecraft body pointing error. This thesis focuses on the development and laboratory verification of the laser pointing system for NODE. A control scheme utilizing a miniature fast steering mirror (FSM) used to track a beacon uplink signal from the ground station is presented. An on-orbit FSM calibration algorithm is developed to improve the control robustness and precision. A novel sampling approach that enables closed-loop FSM control is proposed and implemented. The method focuses on simultaneous sampling of the beacon and an internal feedback signal on a single detector. Finally, a hardware-in-the-loop testbed is built in the laboratory with components that were selected for NODE, and the system is functionally verified and analyzed with regards to pointing accuracy. Experimental results show that the pointing requirements given by the mission link budget are met, and that the system performs reliably under various laboratory-simulated conditions.

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>

<p> With the growing threat of orbital debris impacts to space structures, the development of space shielding concepts has been a critical research topic. In this study, numerical simulations of the hypervelocity impact response of stacked aluminum 6061-T6 sheets were performed to assess the effects of layering on penetration resistance. This work was initially motivated by set of experimental tests where a stack of four aluminum sheets of equal thickness was observed to have a higher hypervelocity ballistic resistance than a monolithic aluminum sheet with the same total thickness. A set of smoothed particle hydrodynamic simulations predicted a 40% increase in the ballistic limit for a 6-layer target compared to a monolithic sheet. In addition, the effect of variable sheet thickness and sheet ordering on the impact resistance was investigated, while still maintaining a constant overall thickness. A set of thin layers in front of a thick layer generally lead to a higher predicted ballistic limit than the inverse configuration. This work demonstrates an increase in the performance of advanced space shielding structures associated with multi-layering. This suggests that it may be possible to dramatically improve the performance of such structures by tailoring the material properties, interfaces, and layering concepts.</p><p>

The thermal protection system (TPS) represents the greatest risk factor after propulsion for any transatmospheric mission (Dr. Charles Smith, NASA ARC). Any damage to the TPS leaves the space vehicle vulnerable and could result in the loss of human life as happened in the Columbia accident. Aboard the current Space Shuttle Orbiters no system exists to notify the astronauts or ground control if the thermal protection system has been damaged. Through this research, a proof-of-concept monitoring system was developed. The system has two specific applications for thermal protection systems: (1) Improving models used to predict thermal and mechanical response of TPS materials, and (2) Self-diagnosing damage within regions of the TPS and communicating the damage to the appropriate personnel over a potentially unstable network. Mechanical damage is among the most important things to protect the TPS against. Methods to detect the primary types of mechanical damage suffered by thermal protection systems have been developed. Lightweight, low-power sensors were developed to detect any cracks in small regions of a TPS. Implementation of a network of these sensors within 10's to 1000's of regions will eventually provide high spatial resolution of damage detection; allowing for detection of holes in the TPS. Also important in thermal protection material development is to know the ablation rates and time/temperature response of the materials. A new type of sensor has been developed to monitor temperature at different depths within thermal protection materials. The signals being transmitted through the sensors can be multiplexed to allow for mechanical damage and temperature to be monitored using the same sensor.

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.