During space missions, real time tele-operation of a rover is not practical because of significant signal latencies associated with inter planetary distances, making some degree of autonomy in rover control desirable. One of the challenges to achieving autonomy is the determination of terrain traversability. As part of this field, the determination of motion state of a rover on rough terrain via the estimation of wheel-terrain contact angles is proposed. This thesis investigates the feasibility of estimating the contact angles from the kinematics of the rover system and measurements from the onboard inertial measurement unit (IMU), joint angle sensors and wheel encoders. This approach does not rely on any knowledge of the terrain geometry or terrain mechanical properties. An existing framework of rover velocity and wheel slip estimation for flat terrain has been extended to additionally estimate the wheel-terrain contact angle along with a side slip angle for each individual wheel, for rough terrain drive. A random walk and a damped model are used to describe the evolution of the contact angle and side slip angle over an unknown terrain. A standard strapdown algorithm for the estimation of attitude and velocity from IMU measurements, is modified to incorporate the 3D kinematics of the rover in the implementation of a nonlinear Kalman filter to estimate the motion states. The estimation results from the filter are verified using tests performed on the ExoMars BB2. The obtained contact angle estimates are found to be consistent with the reference values.

Spacecraft simulator platforms can simulate the microgravity environment of space on Earth, for the purposes of testing the Attitude and Orbit Control Subsystem of satellites. In order to do this, the satellite is mounted on a bench and the combined center of mass of this assembly is controlled by a series of moving masses. The objective is to bring this center or mass as close as possible to the center of rotation, since solids in microgravity always rotate around their own center of mass. The air-bearing platform located, designed and built at the NanoSat Laboratory of the Kiruna Space Campus of the Luleå University of Technology makes use of four balancing masses, which are displaced by that number of linear actuators. This document explains the process followed to design an algorithm for the estimation of the center of mass and the subsequent calculation of the required positions of the balancing masses to bring this center of mass back to the center of rotation. First, the equations of rotational motion of the bench were found through two formulations: quaternions and Euler-Lagrange. Secondly, these equations were used to obtain an estimation of the center of mass via Batch Least-Squares. Thirdly, the equations of the center of mass of a system of point masses were used to find the proper positions of the balancing masses. Finally, the complete algorithm was tested with Hardware-in-the-Loop simulations before testing it in the real hardware of the platform. The developed algorithm was not capable of estimating the center of mass with sufficient accuracy, which invalidated the obtained actuator positions, and thus was not able to compensate the offset of the center of mass. Recommended lines of development are provided to assist on the continuation of this work.

In the scope of this thesis, a possible usage of embedded artificial neural networks for on-board image analysis is investigated. After an introduction which imparts basic knowledge about artificial neural network and autonomy in spaceflight, a possible system design is elaborated based on previously defined reference scenarios. The reference scenarios are based on two projects that are currently under development at the professorship of Space Technology at the University of Würzburg: ASMET and SONATE. As base for the neural network architecture, a convolutional neural network called SqueezeNet was chosen, since it was developed for similar input data and performs sufficiently well. In addition, the SqueezeNet architecture requires extremely little memory for the trained-in model compared to other architectures which makes in-orbit updates of the model feasible. The system concept in this thesis is designed for offline learning, i.e. the training phase will be done on an ordinary computer. The resulting, trained-in model is then transferred to the embedded system. On the embedded side, a FPGA-based approach was chosen since FPGAs allow to parallelize the neural network execution and therefore accelerate it significantly. Even though not all components of the designed concept could be implemented in the scope of this thesis, all key elements were implemented and tested, either on real hardware or by using testbenches. Especially the tests conducted with the convolution unit of the embedded system went well and allowed to make a quite promising assessment of the expected execution speed. In addition, a tool with graphical user interface was developed to guide a potential user of the system through the steps of training-in and setting up the system. For the training process, a neural network framework called Caffe was used within this tool. In summary, this thesis provides as intended a profound starting point for further research on artificial neural network for space applications at the professorship of Space Technology of the University of Würzburg.

The design and development of new aircraft are becoming increasingly expensive and timeconsuming. To assist the design process in reducing the development cost, time, and late design changes, the conceptual design needs enhancement using new tools and methods. Integration of several disciplines in the conceptual design as one entity enables to keep the design process intact at every step and obtain a high understanding of the aircraft concepts at early stages. This thesis presents a Knowledge-Based Engineering (KBE) approach and integration of several disciplines in a holistic approach for use in aircraft conceptual design. KBE allows the reuse of obtained aircrafts’ data, information, and knowledge to gain more awareness and a better understanding of the concept under consideration at early stages of design. For this purpose, Knowledge-Based (KB) methodologies are investigated for enhanced geometrical representation and enable variable fidelity tools and Multidisciplinary Design Optimization (MDO). The geometry parameterization techniques are qualitative approaches that produce quantitative results in terms of both robustness and flexibility of the design parameterization. The information/parameters from all tools/disciplines and the design intent of the generated concepts are saved and shared via a central database. The integrated framework facilitates multi-fidelity analysis, combining low-fidelity models with high-fidelity models for a quick estimation, enabling a rapid analysis and enhancing the time for a MDO process. The geometry is further propagated to other disciplines [Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA)] for analysis. This is possible with an automated streamlined process (for CFD, FEM, system simulation) to analyze and increase knowledge early in the design process. Several processes were studied to streamline the geometry for CFD. Two working practices, one for parametric geometry and another for KB geometry are presented for automatic mesh generation. It is observed that analytical methods provide quicker weight estimation of the design and when coupled with KBE provide a better understanding. Integration of 1-D and 3-D models offers the best of both models: faster simulation, and superior geometrical representation. To validate both the framework and concepts generated from the tools, they are implemented in academia in several courses at Linköping University and in industry

This thesis studies algorithms to estimate an aircraft’s position with different information from various radio stations. Because aircrafts both civilian and military are heavily dependant on GNSS signals, it can be interfered from hostile sources. The aircraft shall then be able to navigate without the GNSS signals. This thesis focuses on three radio navigation systems, DME,VOR and TACAN. With the measurements from these three radio stations and measurements from the inertial navigation system one can estimate a position with an estimation filter. In this thesis two types of filters will be used, the linear Kalman filter and the Extended Kalman filter. The linear Kalman filter will be used when converting the TACAN measurements to a pseudo position and the Extended Kalman filter will be used for the DME,VOR and TACAN measurements. The results shows that the converted TACAN measurements and TACAN measurements estimates very well in both north and east direction. When using only DME measurements the filter estimates the position fairly well in the direction towards the station and poorly in the orthogonal direction. For the VOR measurements the filter estimates the position quite poorly in the direction of the radio station and well in the orthogonal direction. In conclusion the converted TACAN measurement and TACAN measurement algorithm can be used for navigation purposes by its own measurements. However, the DME and VOR measurement algorithms need to be combined or using multiple stations at different locations to get better estimates in both directions. All of the filter could use some better tuning to get the optimal filter, but it is not necessary.

The I2T5, an iodine-propelled, cold gas thruster, developed by ThrustMe, France, is the first of its kind to make it successfully to space. Due to its simple, reliable and cost-effective design, it is a suitable propulsion system for CubeSat missions with low delta-V (ΔV) requirements. To ensure that the I2T5 performs at its peak, it is crucial to maintain good thermal control of the thruster, to keep it within the operational temperature range. The first flight measurements of the I2T5 provided insight into its thermal performance. It was observed that the required temperature to sublimate the iodine propellant was not reached within the expected time frame, which led to a longer warm-up period, and a reduction in thrust. The problem arose due to an unforeseen conductive thermal contact between the tank and the thruster walls. This thesis delves deeper into this issue, and focuses on alleviating the total conductive heat loss from the tank to the satellite frame, where the I2T5 is integrated. The insulating washer-bolt configuration of the I2T5 side panels is observed to be responsible for the conductive heat transfer. A preliminary analysis is performed to obtain an initial maximum for the conductive heat flux lost to the satellite frame. A plan of action is then determined to optimise the geometry, material or configuration of the insulating washers to lower the maximum heat flux value. Following this, an experiment was conducted with a new washer-bolt configuration to determine the heat flux values. A case study is performed for the orbital environment heat fluxes that the I2T5 would receive if it were integrated to a CubeSat in sun-synchronous orbit. An overview of results shows that, for the thermal simulations, all the methods employed to reduce the conductive heat loss at the frame were effective. The experiment provided neutral results, and would need to be repeated with different experimental parameters to have a clear perspective of the heat losses. In reality, the satellite frame receives radiative fluxes in addition to conductive heat fluxes, but radiation is not considered for this thesis, and is suggested as a prospective study.

CubeSats are becoming a game changer in the space industry. Appearing first for univer-sity mission, its popularity is increasing for commercial use and for deep space missionssuch as the on HERA mission that will orbit in 2026 around an asteroid as part of aplanetary defence mission. Standardisation and industrial collaboration is key to a fastdevelopment, assuring the product quality and lower development expenditures.In this study the focus is set elaborating a low cost demonstrator platform to be usedfor developing and testing onboard software on physical hardware: a Hardware-Softwaretesting facility. The purpose of such a platform is to create an interactive and accessibleenvironment for developing on board software. The application chosen to be elaboratedon this platform is a module the subsystem of attitude and orbit control of the satelliteorbiting around asteroid.In order to create this platform the simulation of the asteroid environment of theCubeSat has been made using open source software libraries. During this task the per-formance of open source libraries has been compared to commercial alternatives. In thedevelopment of simulation different orbit perturbations have been studied by modellingthe asteroid as a cube or spheroid and additionally the effect of a third perturbing bodyand radiation pressure.As part of this project two microcontroller have been set up communicating using acommunication bus and communication protocols used for space applications to simulatehow the attitude and orbit control is commanded inside the CubeSat.

There is a large number of design options to consider when designing aircraft vehicle systems for fighter aircraft, and there is a lack of tool support that provides an overview of these available design options. Various design options will bring consequences in terms of weight, performance, cost, etc. which is desired to be known in an early conceptual phase. Conventional methods, such as morphological matrix and design structure matrix, lack the ability to generate an overview and map complex systems. By studying model-based tools in form of ontologies and feature models in Protégé and FeatureIDE respectively, these tools are considered to provide a higher level of detail regarding the available design options compared to the conventional methods, such as the morphological matrix and the design structure matrix. Ontologies and feature-models are therefore considered to increase the effectiveness in the conceptual design phase of aircraft vehicle systems. By combining ontologies and feature models, more thoughtful design decisions can be performed. An increased knowledge of the available design options can lead to an improved development of aircraft vehicle systems, and new solutions can be evaluated. By performing more detailed trade studies for an unmanned aerial vehicle, for different system solutions, various parameters such as engine power outtake, system weight, etc. can be analysed and provide an indication whether a concept should be evaluated further. It is however necessary to consider how different parameters affect the overall system, and fuel penalty may be implemented as an equivalent parameter. Performing power flow calculations do however not consider solution-specific limitations, which have to be implemented to be able to determine if an aircraft vehicle system concept should be considered advantageous or not.

This thesis aims to develop a methodology to translate an ontology to a matrixbased methods that is case independent. In the larger picture this is one of manycomplexities in systems engineering approach. The focus in this work is in the domainof conceptual design, hence, matrix based methods that are most suitable for it areinvestigated. The flexible nature of the ontology always allows for expansion withnew information about the concepts, and from that perspective a parsing scriptwas developed to extract information from the ontology, it was also designed to beflexible. The script can be used to extract any desired type of information by alteringa few keywords as inputs. The advantage is that the same structure of the script canbe used to extract information from many different ontologies.Using this method the matrices relevant for conceptual design were formulated.These matrices were further compared to each other. Also, a few recommendationswere given for the improvement of the method to adapt towards high fidelity. Thecurrent method is capable of solving problems with low fidelity, however this formsa basis to expand the method to high fidelity problems.

This thesis proposes a distributed robust control approach for low-thrust nanosatellite formation flying. The presented control approach is the further development of an already existing approach which combines robust control and distributed control using the consensus approach. The adjustments presented in this thesis are intended to enable the usage of the control approach in nanosatellite missions such as the upcoming NetSat mission. Stability criteria, optimization goals and constraints such as the limited maximum thrust are formulated with the help of Linear Matrix Inequalities (LMIs). In addition, the presented control approach includes methods for exploiting the maximum thrust and for collision avoidance. Due to the design as a distributed controller based on the consensus approach, a satellite formation can be maintained even in the case of the failure of the propulsion system and/or Attitude Determination and Control System (ADCS) of a single satellite. To verify the design of the control approach, simulations of the formation scenarios planned for the NetSat mission are performed with a satellite formation simulation framework based on Orekit and MATLAB®.