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 Fargo : validation of space-relevant ferrofluid applications on the ISS(2024) Sütterlin, Saskia; Bölke, Daniel; Ehresmann, Manfred; Heinz, Nicolas; Dietrich, Janoah; Karahan, Bahar; Kob, Maximilian; O’Donohue, Michael; Korn, Christian; Grossmann, Steffen; Philipp, Daniel; Steinert, Michael; Acker, Denis; Remane, Yolantha; Kreul, Phil; Schneider, Maximilian; Zajonz, Sebastian; Wank, Bianca; Turco, Fabrizio; Buchfink, Manuel; Gutierrez, Elizabeth; Hofmann, Sonja; Ruffner, Silas; Wagner, Alexander; Breitenbücher, Laura; Schäfer, Felix; Herdrich, Georg; Fasoulas, StefanosThe Ferrofluid Application Research Goes Orbital (FARGO) project desires to harness the potential of ferrofluids for advanced space system applications. Thereby, the student-led research project aims to develop, evaluate and subsequently validate three different ferrofluid-based applications on board the International Space Station (ISS): a novel attitude control system called Ferrowheel as well as a Thermal and an Electrical Switch. The project is part of the Überflieger2 competition of the German Aerospace Center (DLR) in cooperation with the Luxembourg Space Agency (LSA). Central to this study is the role of ferrofluids in ensuring the functional principles to minimize the number of moving components ultimately. Therefore, the proposed systems have the potential to mitigate wear, reduce friction, and consequently improve the longevity and reliability of space systems. In the Ferrowheel, a disc is supported on ferrofluid cushions instead of conventional ball-bearing-mounted rotors. This innovative approach, facilitated by the magnetic pressure positioning of the ferrofluid, eliminates the need for solid-to-solid contact. Circularly arranged coils function as the stator, propelling the disc with a 3-phase control, resulting in a spinning magnetic field. In addition to determining the generated torque, the objective is to validate experiments on system operations in which various acceleration and deceleration manoeuvres, as well as the stored angular momentum, are evaluated. The Electrical Switch leverages a self-manufactured magnetorheological fluid (MRF) developed by augmenting a liquid-metal base with iron powder. As a result, the fluid, akin to ferrofluid, has a magnetic field-responsive movement. Since a liquid metal is used as the base, the ferrofluid-like fluid acts as both the magnetically actuatable and the current conducting fluid. To enable a current flow, the fluid is brought between the two electrical contacts utilizing electropermanent magnets (EPMs). These magnets combine the high magnetic field strengths of permanent magnets with the adaptive switching capability of electromagnets. Compared to all other demand-controlled magnetic field sources, this results in the great advantage that no energy is consumed as long as they are in one state. Only the switching process of the EPMs itself requires a high amount of energy, but only for a relatively short period. The switching behaviour under different loads will be investigated, evaluated, and compared to reference data recorded on Earth. The design of the Thermal Switch is characterized by the fact that it can be actively switched. Active thermal switching is still a relatively new field, so there is little comparative data from industrial solutions. Particularly for spacecraft, thermal design is crucial because the harsh environment of space must be taken into account. In addition to the challenge that heat can only be transferred to the environment via thermal radiation, severe conditions in space are characterized by extreme temperature differences. While extreme heat develops on the satellite surface on the side facing the sun, the opposite is valid on the shaded side. The resulting heat flow, which is irregular in time, location, and direction, leads to temperature peaks and gradients that can affect the system’s performance, functionality, and reliability. Active switching provides selective control over heat transfer, allowing more flexible temperature regulation in critical areas and implementing a dynamic system response. Different design ideas are tested and evaluated for the applications in various experiments. The most suitable design is finally selected, further modified, and tailored for experimentation on the ISS and presented in this study. The most significant challenge is the time-critical factor of only a 1-year development phase. A total of 21 students from six different courses of study and two supervising PhD students from the Institute of Space Systems are involved in the FARGO project, all members of the small satellite student society at the University of Stuttgart, KSat e.V.Item Open Access Satellite design optimization for differential lift and drag applications(2024) Marianowski, Claudia; Traub, Constantin; Pfeiffer, Marcel; Beyer, Julian; Fasoulas, StefanosUtilizing differential atmospheric forces in the very low earth orbits (VLEO) regime for the control of the relative motion within a satellite formation is a promising option as any thrusting device has significant impact on system design due to the limited weight and size restrictions of small satellites. One possible approach to increase the available accelerations caused by the atmosphere is to reduce the mass of the respective satellites as well as to increase the available surface area. However, satellites of these characteristics suffer from rapid orbital decay and consequently have a reduced service lifetime. Therefore, achieving higher control forces is in contradiction to achieving a minimum orbital decay of the satellites, which currently represents one of the biggest challenges in the VLEO regime. In this article, the geometry of a given reference satellite, a 3UCubeSat, is optimized under the consideration of different surface material properties for differential lift and drag control applications while simultaneously ensuring a sustained VLEO operation. It is worth noting that both the consideration of sustainability as well as the optimization with regard to differential lift are new in literature. It was shown that the advantageous geometries strongly depend on the type of gas-surface interaction and thus, two different final designs, one for each extreme type, are presented. In both cases, improvements in all relevant parameters could be achieved solely via geometry adaptions.Item Open Access Mars and Venus entry simulation capabilities of IRS plasma wind tunnel PWK3(2012) Herdrich, Georg; Marynowski, Thomas; Dropmann, Michael; Fasoulas, StefanosAn assessment is made for the inductively driven plasma wind tunnel PWK3 with the goal to derive relevant mass specific enthalpies for typical Mars and Venus atmospheric entry missions. For this purpose an integral method has been used which links the plasma power to the radial distribution of total pressure and fully catalytic heat flux in the plasma jet on basis of a relation from Marvin and Pope. Rebuilding the enthalpies with this relation allows for the derivation of a gas specific proportionality factor. This factor enables the derivation of the mass specific enthalpies at the centre line and the radial profiles for the respective condition are not necessarily required any more. Correspondingly a review of reference CO2 plasma conditions obtained in past investigations at IRS leads to the identification of an operational envelope in terms of the mass specific enthalpies which are from an energy consideration the prerequisite for the creation of similarities with respect to the real atmospheric entry maneuvers. The analysis shows that PWK3 is capable to cover the full range of mass specific enthalpies that are required for typical Mars and Venus atmospheric entry scenarios.Item Open Access Chemical heat derived from rocket-borne WADIS-2 experiment(2024) Grygalashvyly, Mykhaylo; Strelnikov, Boris; Strelnikova, Irina; Rapp, Markus; Lübken, Franz-Josef; Schütt, Corinna; Stephan, Claudia; Eberhart, Martin; Löhle, Stefan; Fasoulas, StefanosChemical heating rates were derived from three of the most significant reactions based on the analysis of common volume rocket-borne measurements of temperature, atomic oxygen densities, and neutral air densities. This is one of the first instances of the retrieval of nighttime chemical heat through the utilization of non-emissive observations of atomic oxygen concentrations, obtained through in situ measurements, performed at the Andøya Space Center (69°N, 16°E) at 01:44:00 UTC on 5 March 2015. Furthermore, we determine the heating efficiency for one of the most significant reactions of atomic hydrogen with ozone and illustrate the methodology for such calculations based on known atomic oxygen and temperature. Subsequently, using ozone values obtained from satellite observations, we retrieved odd-hydrogens and total chemical heat. Finally, we compared the retrieved chemical heat with the heat from turbulent energy dissipation. Our findings reveal that the vertically averaged chemical heat is greater than the heat from turbulent energy dissipation throughout the entire mesopause region during nocturnal conditions. The heating rates of turbulent energy dissipation may exceed the chemical heating rates only in narrow peaks, several hundred meters wide.Item Open Access Relation between crystal structure and transition temperature of superconducting metals and alloys(2020) Koblischka, Michael Rudolf; Roth, Susanne; Koblischka-Veneva, Anjela; Karwoth, Thomas; Wiederhold, Alex; Zeng, Xian Lin; Fasoulas, Stefanos; Murakami, MasatoUsing the Roeser-Huber equation, which was originally developed for high temperature superconductors (HTSc) (H. Roeser et al., Acta Astronautica 62 (2008) 733), we present a calculation of the superconducting transition temperatures, 𝑇𝑐, of some elements with fcc unit cells (Pb, Al), some elements with bcc unit cells (Nb, V), Sn with a tetragonal unit cell and several simple metallic alloys (NbN, NbTi, the A15 compounds and MgB2). All calculations used only the crystallographic information and available data of the electronic configuration of the constituents. The model itself is based on viewing superconductivity as a resonance effect, and the superconducting charge carriers moving through the crystal interact with a typical crystal distance, x. It is found that all calculated 𝑇𝑐-data fall within a narrow error margin on a straight line when plotting (2𝑥)2 vs. 1/𝑇𝑐 like in the case for HTSc. Furthermore, we discuss the problems when obtaining data for 𝑇𝑐 from the literature or from experiments, which are needed for comparison with the calculated data. The 𝑇𝑐-data presented here agree reasonably well with the literature data.Item Open Access Enhanced gas-surface scattering modeling for VLEO satellites in DSMC simulations(2025) Schütte, Miklas; Fasoulas, Stefanos; Pfeiffer, MarcelIn VLEO, the continuum assumption breaks down requiring the use of the DSMC method to simulate the gas flow around satellites. However, DSMC simulations relies on simplified GSI models, such as the Maxwell model or the Cercignani-Lampis model, which are based on constant accommodation coefficients. Instead, these coefficients are variable, influenced by multiple factors, which makes their accurate determination challenging. Furthermore, these models are using simplifying assumptions, such as superposition of specular and diffuse reflections, or independent scattering of the normal and tangential components of the velocity. Implementing a high precision GSI model enables to optimize the aerodynamics of VLEO satellites and to design efficient intakes for atmospheric breathing propulsion systems vastly enhance mission planning and fuel requirement calculations, ultimately extending operational lifetimes and reducing costs. We present an approach that integrates MD simulation data into DSMC through a scattering kernel modeled as a Gaussian mixture conditional probability density function. Preliminary tests on synthetic data derived from the Cercignani-Lampis model demonstrate the model’s capability to accurately predict reflected velocities. Additional improvements are needed to enhance the model’s performance in interpolation and extrapolation of unknown incoming velocities in the future.Item Open Access Analysis of collision avoidance manoeuvres using aerodynamic drag for the Flying Laptop satellite(2023) Turco, Fabrizio; Traub, Constantin; Gaißer, Steffen; Burgdorf, Jonas; Klinkner, Sabine; Fasoulas, StefanosCollision avoidance is a topic of growing importance for any satellite orbiting Earth. Especially those satellites without thrusting capabilities face the problem of not being able to perform impulsive collision avoidance manoeuvres. For satellites in low Earth orbits, though, perturbing accelerations due to aerodynamic drag may be used to influence their trajectories, thus offering a possibility to avoid collisions without consuming propellant. Here, this manoeuvring option is investigated for the satellite Flying Laptop of the University of Stuttgart, which orbits the Earth at approximately 600km. In a first step, the satellite is aerodynamically analysed making use of the tool ADBSat. By employing an analytic equation from the literature, in-track separation distances can then be derived following a variation of the ballistic coefficient through a change in attitude. A further examination of the achievable separation distances proves the feasibility of aerodynamic collision avoidance manoeuvres for the Flying Laptop for moderate and high solar and geomagnetic activity. The predicted separation distances are further compared to flight data, where the principle effect of the manoeuvre on the satellite trajectory becomes visible. The results suggest an applicability of collision avoidance manoeuvres for all satellites in comparable and especially in lower orbits than the Flying Laptop , which are able to vary their ballistic coefficient.Item Open Access Motivation, structure and goals of the collaborative research centre 1667 : advancing technologies of very low-altitude satellites - ATLAS(2025) Fasoulas, Stefanos; Pagan, Adam S.; Traub, Constantin; Annighöfer, Björn; Barz, Stefanie; Beck, Andrea; Cunis, Torbjørn; Dekorsy, Thomas; Essig, Stephanie; Fichter, Walter; Flemisch, Bernd; Herdrich, Georg; Hobiger, Thomas; Kallfass, Ingmar; Kästner, Johannes; Klinkner, Sabine; Lamanna, Grazia; Loehle, Stefan; Pfeiffer, Marcel; Poser, Rico; Roth, Johannes; Saliba, Michael; Schneider, Martin; Sneeuw, Nico; Wagner, GerdThe Collaborative Research Centre (CRC) 1667 “Advancing Technologies of Very Low Altitude Satellites-ATLAS” was established in April 2024 with the scientific goal of addressing the fundamental challenges of making satellite operations in Very Low Earth Orbits (VLEO) sustainable. These orbits are beneficial for satellite services that have become indispensable to our modern society. Moreover, access to VLEO offers the opportunity to operate satellites without exposure or contribution to the increasing contamination of traditional orbits with space debris. Seventeen highly interlinked research projects have been selected to investigate and advance accurate numerical and experimental methods for gas-surface interactions, novel concepts utilising the residual atmosphere and minimising the satellite sizes, and mission-related challenges of a selected scenario. In addition, support projects cover topics related to public outreach and academic exchange and assist in achieving the strategic goal of positioning the University of Stuttgart as a key contributor to this internationally very important research area. In summary, the CRC ATLAS aims to constitute a research-oriented profile-building measure at the University of Stuttgart with a strong international reputation.Item Open Access Very low earth orbit missions and technologies(2026) Fasoulas, Stefanos; Herdrich, Georg; Traub, Constantin; Crisp, Nicholas H.; Roberts, Peter C. E.Item Open Access Enhanced algorithms to ensure the success of rendezvous maneuvers using aerodynamic forces(2021) Bühler, Simon; Traub, Constantin; Fasoulas, Stefanos; Herdrich, Georg H.A common practice in the field of differential lift and drag controlled satellite formation flight is to analytically design maneuver trajectories using linearized relative motion models and the constant density assumption. However, the state-of-the-art algorithms inevitably fail if the initial condition of the final control phase exceeds an orbit and spacecraft-dependent range, the so-called feasibility range. This article presents enhanced maneuver algorithms for the third (and final) control phase which ensure the overall maneuver success independent of the initial conditions. Thereby, all maneuvers which have previously been categorized as infeasible due to algorithm limitations are rendered feasible. An individual algorithm is presented for both possible control options of the final phase, namely differential lift or drag. In addition, a methodology to precisely determine the feasibility range without the need of computational expensive Monte Carlo simulations is presented. This allows fast and precise assessments of possible influences of boundary conditions, such as the orbital inclination or the maneuver altitude, on the feasibility range.