06 Fakultät Luft- und Raumfahrttechnik und Geodäsie
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/7
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Item Open Access Development and application of PICLas for combined optic-/plume-simulation of ion-propulsion systems(2019) Binder, Tilman; Fasoulas, Stefanos (Prof. Dr.-Ing.)Electric propulsion systems are an efficient option for altitude/attitude control and orbit transfers of spacecraft. One example is the gridded ion thruster which ionizes the propellant and accelerates the ions of the generated plasma by a high-voltage grid system. This work deals with the numerical simulation of the plasma flow starting near the grid system in the ionization chamber and leaving the thruster with high velocity. These simulations give direct insight into the modeled, physical interrelationships and can be used to investigate questions arising in the industrial development process of ion propulsion systems. The required simulation method is challenging due to the high degree of flow rarefaction and the plasma state itself, including freely moving ions and electrons. Applicable simulation methods belong to a particle-based, gas-kinetic approach, such as Particle-In-Cell (PIC) for the simulation of electromagnetic interaction and the Direct Simulation Monte Carlo (DSMC) for inter-particle collisions. The effects resulting from the finite size of a real system can only be investigated by simulating the complete, three-dimensional thruster geometry which requires a large and complex simulation domain. Acceptable simulation times are realized by expanding and using the framework of the coupled PIC-DSMC code PICLas in combination with high performance computing systems.Item Open Access Active removal of space debris with space-based lasers : performance and requirements(2016) Schmitz, Manuel; Fasoulas, Stefanos (Prof. Dr.-Ing.)Space debris has recently become a topic of elevated interest. As the threat of an uncontrollable collision cascade among defunct space objects, known as the Kessler syndrome, is being discussed, the stakeholders and decision-makers have begun to consider the active removal of orbital debris. Thus motivated, the space community has begun conceiving and studying technical concepts for the realization. The bulk of them address the removal of larger bodies from orbit. These are catalogued and have the potential of fragmenting into a high number of new, dangerous objects. This thesis, however, treats a concept for the removal of the medium-sized (1 cm to 10 cm) debris objects. These are by far more numerous and are not catalogued. They have a comparable destructive potential but may be even harder to pick from their orbits. The remediation concept treated herein employs a space-based, high-power laser. By engaging objects in the size regime of 1 cm to 10 cm, and causing laser-induced surface ablation on a substantial subset of the debris population, the objects' perigees shall be reduced, so that they will re-enter the atmosphere quickly and eventually burn up. Although this mission concept has been studied in the past, essential key aspects have not yet been analysed in sufficient depth. In fact, important parts have only been covered by rough estimates and rule-of-thumb calculations. Among these topics are: The number of reachable debris objects, the necessity for orbital manoeuvres to be performed by the laser, the impact of the relative motion between laser and debris in the near field, and the connection between the laser optics and orbital mechanics. This thesis determines the boundaries in which a space-based laser debris removal can be performed. It identifies the necessary assumptions and the prerequisites, and derives technical system requirements for an implementation. For this purpose, a generic and comprehensive mission performance model is established. The model employs a discrete element approach, which is implemented as a numerical code. It allows performing case studies of individual missions as well as systematic parameter scans and optimizations. Additionally, it provides insight into the relevant mechanisms that are driving the performance: The user can tell why a particular scenario is strong or weak, and iteratively tune the mission and system parameters of the orbital debris sweeper platform. Three performance-driving quantities have been identified: The laser range, the tracking agility and the laser's power. This computer-based model is used to identify the constraints and the boundary conditions of the mission concept in general, framing a "design space" of missions. Finally, three exemplary sweeper missions are presented as a demonstration of the model's capabilities. Requirements for their technical implementation are estimated, along with an analysis of their remediation performance. The balanced scenario is shown to be capable of reducing the debris density in the most polluted orbital regions by 23% in 10 years.Item Open Access Optimal heliocentric orbit raising of CubeSats with a monopropellant electrospray multimode propulsion system(2025) Quarta, Alessandro A.; Bassetto, Marco; Becatti, GiuliaA Multimode Propulsion System (MPS) is an innovative spacecraft thruster concept that integrates two or more propulsion modes sharing the same type of propellant. A spacecraft equipped with an MPS can potentially combine the advantages of continuous-thrust electric propulsion and medium-to-high-thrust chemical propulsion within a single vehicle, while reducing the overall mass compared to traditional configurations where each propulsion system uses a different propellant. This feature makes the MPS concept particularly attractive for small spacecraft, such as the well-known CubeSats, which have now reached a high level of technological maturity and are employed not only in geocentric environments but also in interplanetary missions as support elements for conventional deep-space vehicles. Within the MPS framework, a Monopropellant-Electrospray Multimode Propulsion System (MEMPS) represents a specific type of micropropulsion technology that enables a single miniaturized propulsion unit to operate in either catalytic-chemical or electrospray-electric mode. This paper investigates the flight performance of a MEMPS-equipped CubeSat in a classical circle-to-circle orbit-raising (or lowering) maneuver within a two-dimensional mission scenario. Specifically, the study derives the optimal guidance law that allows the CubeSat to follow a transfer trajectory optimized either for minimum flight time or minimum propellant consumption, starting from a parking orbit of assigned radius and targeting a final circular orbit. Numerical simulations indicate that a heliocentric orbit raising, increasing the initial solar distance by 20%, can be achieved with a flight time of approximately 11 months and a propellant consumption slightly below 6 kg. The proposed method is applied to a heliocentric case study, although the procedure can be readily extended to geocentric transfer missions, which represent a more common application scenario for current CubeSat-based scientific missions.Item Open Access Merging spacecraft software development and system tests : an agile verification approach(2021) Bucher, Nico; Eickhoff, Jens (Prof. Dr.-Ing.)In this dissertation, the author describes an agile verification approach for spacecraft onboard software that allows for software development guided by system tests performed with the actual spacecraft. The approach was applied for the Flying Laptop small satellite, built and operated by the Institute of Space System (IRS) at the University of Stuttgart, Germany. This work contains examples of practical experience gathered during the system testing campaign of Flying Laptop.Item Open Access Simulating asteroid impacts and meteor events by high-power lasers : from the laboratory to spaceborne missions(2023) Ferus, Martin; Knížek, Antonín; Cassone, Giuseppe; Rimmer, Paul B.; Changela, Hitesh; Chatzitheodoridis, Elias; Uwarova, Inna; Žabka, Ján; Kabáth, Petr; Saija, Franz; Saeidfirozeh, Homa; Lenža, Libor; Krůs, Miroslav; Petera, Lukáš; Nejdl, Lukáš; Kubelík, Petr; Křivková, Anna; Černý, David; Divoký, Martin; Pisařík, Michael; Kohout, Tomáš; Palamakumbure, Lakshika; Drtinová, Barbora; Hlouchová, Klára; Schmidt, Nikola; Martins, Zita; Yáñez, Jorge; Civiš, Svatopoluk; Pořízka, Pavel; Mocek, Tomáš; Petri, Jona; Klinkner, SabineMeteor plasmas and impact events are complex, dynamic natural phenomena. Simulating these processes in the laboratory is, however, a challenge. The technique of laser induced dielectric breakdown was first used for this purpose almost 50 years ago. Since then, laser-based experiments have helped to simulate high energy processes in the Tunguska and Chicxulub impact events, heavy bombardment on the early Earth, prebiotic chemical evolution, space weathering of celestial bodies and meteor plasma. This review summarizes the current level of knowledge and outlines possible paths of future development.Item Open Access Machine learning and Monte Carlo based data analysis methods in cosmic dust research(2019) Albin, Thomas; Srama, Ralf (Priv.-Doz. Dr.-Ing.)This work applies miscellaneous algorithms from the fields Machine Learning and Computational Numerics on the research field Cosmic Dust. The task is to determine the scientific and technical potential of using different methods. Here, the methods are applied on two different projects: the meteor camera system Canary Island Long-Baseline Observatory (CILBO) and the Cassini in-situ dust telescope Cosmic-Dust-Analyzer (CDA).Item Open Access Untersuchungen zum Einsatzpotential und zur Inkjet-Fertigung von Mischpotential-Elektrolytsystemen(2022) Scherer, Philip; Fasoulas, Stefanos (Prof. Dr.-Ing.)Item Open Access Electrical conductivity of the thermal dusty plasma under the conditions of a hybrid plasma environment simulation facility(2015) Zhukhovitskii, Dmitry I.; Petrov, Oleg F.; Hyde, Truell W.; Herdrich, Georg; Laufer, Rene; Dropmann, Michael; Matthews, Lorin S.We discuss the inductively heated plasma generator (IPG) facility in application to the generation of the thermal dusty plasma formed by the positively charged dust particles and the electrons emitted by them. We develop a theoretical model for the calculation of plasma electrical conductivity under typical conditions of the IPG. We show that the electrical conductivity of dusty plasma is defined by collisions with the neutral gas molecules and by the electron number density. The latter is calculated in the approximations of an ideal and strongly coupled particle system and in the regime of weak and strong screening of the particle charge. The maximum attainable electron number density and corresponding maximum plasma electrical conductivity prove to be independent of the particle emissivity. Analysis of available experiments is performed, in particular, of our recent experiment with plasma formed by the combustion products of a propane-air mixture and the CeO2 particles injected into it. A good correlation between the theory and experimental data points to the adequacy of our approach. Our main conclusion is that a level of the electrical conductivity due to the thermal ionization of the dust particles is sufficiently high to compete with that of the potassium-doped plasmas.Item Open Access A small linear accelerator for charged microparticles(2025) Bauer, Marcel; Li, Yanwei; Srama, Ralf; Behrens, Florian; Mocker, Anna; Schäfer, Felix; Simolka, Jonas; Strack, HeikoResearching cosmic dust requires terrestrial facilities for accelerating analogues of different sizes and masses. To address the area of very lightweight particles, electrostatic accelerators like Van de Graaf accelerators or Linear Accelerators (LINACs) have proven adequate. This article describes the components, dimensions, working principle and attributes of a variable frequency switched 6-stage LINAC of 120 kilovolts (kV) potential based at the Institute of Space Systems, University of Stuttgart. It utilizes negative voltages, no storage capacitors, isometric drift tubes, one semiconductor-based high-voltage switch per stage and there is no voltage drop during acceleration. The particle rate can reach up to 33 particles per second. By setting a target speed window, it autonomously chooses the right number of acceleration stages to meet that requirement, if possible. Micron-sized iron particles were accelerated successfully, achieving speed increase rates of up to three times the pre-LINAC speed and a total speed of up to 1300 m/s. This platform provides a new tool for dust sensor calibration, impact physics and material surface processing due to its ability to bring particles of different charge-to-mass ratios to a defined target speed.Item Open Access Experimentelle Untersuchungen zum Versagen von Raumfahrtstrukturen beim atmosphärischen Wiedereintritt(2024) Leiser, David; Fasoulas, Stefanos (Prof. Dr.-Ing.)In der vorliegenden Dissertation wird der Einfluss mechanischer Lasten auf den destruktiven Wiedereintritt großer Raumfahrtstrukturen experimentell analysiert. Dabei wird der Einfluss mechanischer Lasten insbesondere auf die Break-Up Höhe untersucht, da diese für weitere Fragmentierungsprozesse und Verglühen von entscheidender Bedeutung ist. Dazu wird ein neuer mechanischer Aufbau beschrieben, der mechanische Lasten in Bodentests aufbringen kann. Der Aufbau basiert auf einem elektromechanischen Lastzylinder, der in den Plasmawindkanal PWK4 integriert wurde. Dieses neuartige Konzept weist eine Probenform auf, für die eine erweiterte Umrechnungsmöglichkeit von Flugsituationen in Bodensimulationen erforderlich ist. Dazu wird die bekannte LHTS Ähnlichkeit um eine axialsymmetrisch planare Transformation erweitert. Diese Methode wird durch Wärmestromdichtemessungen im Plasmawindkanal validiert. Die mechanischen Lasten auf die Modulverbindungselemente der Internationalen Raumstation werden durch Freiflugexperimente im Stoßwindkanal TUSQ der University of Southern Queensland untersucht. Die ermittelten Lasten werden zum Flugfall skaliert und entlang einer typischen Wiedereintrittstrajektorie extrapoliert. Als Versuchsbedingung werden drei Trajektorienpunkte in 90 km, 75 km und 65 km Höhe entlang einer typischen Wiedereintrittstrajektorie aus dem niedrigen Erdorbit untersucht. Diese entsprechen der frühen Eintrittsphase, der Höhe des typischen Break-Up und der Höhe der maximalen Wärmelast. Dabei werden sowohl die Plasmabedingung als auch die mechanische Last auf diese Trajektorienpunkte angepasst. Vier typische, metallische Strukturmaterialien werden untersucht; zwei verschiedene Aluminiumlegierungen, eine Edelstahllegierung sowie eine Titanlegierung. Um das Materialverhalten vergleichen zu können, werden die Proben sowohl unbelastet als auch belastet getestet. Die Materialversuche weisen deutliche Unterschiede sowohl zwischen den unterschiedlichen Materialien als auch zwischen den Versuchsbedingungen auf. Die Hochtemperaturmaterialien Edelstahl und Titan versagen nie unter den nominellen Bedingungen; eine Lasterhöhung führt zur Einschnürung und schlussendlich zum Versagen der Materialien. Bei den Aluminiumlegierungen können je nach Bedingung und Last drei unterschiedliche Versagensarten beobachtet werden, Einschnüren mit Bruch, Sprödbruch, und Schmelzen. Die mechanischen, thermischen und spektroskopischen Analysen der Proben zeigen Eigenschaften wie Deformation, Oxidation und spektrale Emission. Eine Analyse des Oxidationsverhaltens, gekoppelt mit der spektralen und visuellen Analyse zeigt, dass das atypische Verhalten der gemessenen Oberflächentemperatur, einer Veränderung des Emissionsgrads infolge von chemischen Reaktionen zugeordnet werden kann. Spektrale Merkmale werden mit den Daten aus Beobachtungsmissionen verglichen. Dabei zeigt sich, dass bisherige Korrelationen zu spektralen Ereignissen und dem Zerfall einzelner Komponenten nicht gültig sind. Der Nachweis von Alkalimetallen ist dabei, nicht auf Komponenten zurückzuführen, sondern als Spurenelement in allen Strukturelementen vorhanden. Vor allem in Edelstahl und Titan sind die spektralen Signaturen eher durch Änderungen des Oxidationsverhaltens erklärbar als durch strukturelles Versagen. Ein Modell auf Basis der Meteorforschung wird genutzt, um den Massenverlust eines beobachteten Wiedereintritts abzuschätzen. Die Materialparameter werden dafür experimentell ermittelt. Die daraus errechnete Gesamtmasse weicht dabei maximal 20 % von der Gesamtmasse des Raumtransporters Cygnus beim Wiedereintritt ab. Diese Arbeit zeigt, dass mechanische Lasten beim destruktiven Wiedereintritt eine signifikante Rolle spielen. Versuche in Bodentestanlagen unter kombinierten Lasten stellen für eine experimentelle Untersuchung eine geeignete Methode zur Evaluation des Materialverhaltens dar.