Earth’s biosphere is sustained by its biological diversity, which forms an intricate network of biological, physical and chemical pathways. This network has many fail-safe redundant func-tions including buffer stocks of inert biomass, huge amounts of water and the large volume of gases in the atmosphere. By contrast, manmade habitats for human space exploration are closed ecosystems that represent only a trivial fraction of Earth’s biosphere. The employment of bio-regenerative processes complemented with physical-chemical tech-nologies is thought to have numerous advantages from the perspective of redundancy and reducing resupply mass for the sustained human presence in space or on other planetary surfaces. However, the combination of bio-regenerative processes, such as plant cultivation, with physical-chemical processes to form hybrid life support systems is challenging. Such systems are a concert of many interdependencies and interacting feedback loops, which are difficult to operate in a desired range of set points. Furthermore, the complexity of such sys-tems makes them vulnerable to perturbations. Applying system dynamics modelling to study hybrid life support systems is a promising ap-proach. System dynamics is a methodology used to study the dynamic behavior of complex systems and how such systems can be defended against, or made to benefit from, the per-turbations that fall upon them. This thesis describes the development of a system dynamics model to run exploratory simulations, which can lead to new insights into the complex behav-ior of hybrid life support systems. An improved understanding of the overall system behavior also helps to develop sustainable, reliable and resilient life support architectures for future human space exploration. A set of simulations with a hybrid life support system integrated into a Mars habitat has been executed and the results show a strong impact of space greenhouses on the life support sys-tem behavior and the different matter flows. It is also evident from the simulation results that a hybrid life support system can recover from a perturbation event in most cases without a fatal mission end. Recycling urine to produce a plant nutrient solution is a novel approach in further closing loops in space life support systems. Within this thesis, a number of experiments have been executed in order to determine the effectiveness of a urine-derived nutrient solution com-pared to a standard reference solution. The results show that in principle plants can be grown with a nutrient solution made of human urine, but that the yield is lower compared to the reference solution. However, the urine-derived solution might be tuned by adding small amounts of additional nutrients to remove the imbalance of certain elements. This way the nutrient salts supplied from Earth could be reduced.

Les questions de mobilité et de logement sont aujourd’hui au centre des enjeux du développement urbain. La hausse du taux de motorisation, de la pression sur le marché du logement, poussent à une déstructuration des liens de proximité et génèrent aujourd’hui une saturation du système de transport. De cette difficulté à se déplacer naissent des tensions (augmentation du temps de trajet, risque de retard, etc.). L’objectif de cette thèse est alors d’étudier le poids de ces tensions dans la décision de déménager. Une enquête a été réalisée auprès de 500 résidants actifs luxembourgeois ayant déménagé sans changer de lieu de travail. Les résultats montrent que certains individus se sont bien rapprochés de leur lieu de travail dans le but de réduire ces tensions. Cette recherche a donc permis de mettre en évidence des liens de conjonction entre la mobilité quotidienne et résidentielle et d’aboutir à une meilleure compréhension du système de la mobilité spatiale locale des individus. / Mobility and housing are today at the centre of the urban development issues. Indeed, the raise of the motorization rate, combined with the increasing property market pressure, are leading to a disruption of proximity links and tend to generate transportation system saturation. Those difficulties affecting mobility gives tensions (increased travel time, risk of delay, etc.). The objective of this thesis was to study the weight of those tensions in the residential mobility process. A survey was conducted among 500 active’s Luxemburg residents. Those people have recently changed housing without having changed their workplace. Results show that some people get now closer to their workplace in order to reduce their daily mobility tensions. This research helped highlighting links between daily mobility and residential mobility conjunction and lead to a better understanding of the local spatial mobility system of individuals.

Most of the work on photography is about image and trying to understand photography as an image. Contrary to this approach, this paper deals with the experience of the photographer at the time of taking the picture, and also the influence of photography, understood as a medium, on our perception. The main topic is the photography of movement, where we can best demonstrate how photography changes both our perception and our understanding of (objective) reality. The beginning of the work is devoted to one of the greatest Czech photographers, Josef Sudek, who describes the method of his work. Sudek's definition of the moment involved in taking the picture is "when everything fits together"; the impossibility of returning to the same moment is a central feature of photography as presented in this work. Consequently, the basis for the thesis is that (1) photography and camera change the way we perceive, and that (2) photography is an actualization of the possibility of how we see what we see. The actualization of the possibility is discussed mainly in the context of Barbara Probst, whose work "Exposures" fundamentally enters the history of photography, and who - once again - does not put emphasis on the image but rather on the photographer as the creator of the image.