06 Fakultät Luft- und Raumfahrttechnik und Geodäsie

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/7

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Publication Type: search.filters.UBSTyp.ZeitschriftenartikelAuthor: search.filters.author.Fasoulas, StefanosInstitute: search.filters.UBSInstitut.Institut für RaumfahrtsystemeSubject: search.filters.subject.624

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    Satellite design optimization for differential lift and drag applications
    (2024) Marianowski, Claudia; Traub, Constantin; Pfeiffer, Marcel; Beyer, Julian; Fasoulas, Stefanos
    Utilizing 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.
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    Solar activity dependency of a specular intake for an ABEP system
    (2025) Barth, Nadine; Skalden, Jonathan; Papavramidis, Konstantinos; Tuttas, Franziska; Pfeiffer, Marcel; Beyer, Julian; Tietz, Raphael; Fasoulas, Stefanos; Herdrich, Georg
    Challenging space missions at very low altitudes face significant atmospheric drag, requiring efficient propulsion methods such as Atmosphere-Breathing Electric Propulsion (ABEP) to extend mission lifetimes. ABEP captures atmospheric particles and uses them as propellant for an electric thruster, reducing dependence on limited on-board propellant. This could extend missions in Very Low Earth Orbit (VLEO) and on celestial bodies with an atmosphere, such as Mars. The Institute of Space Systems (IRS), under the EU H2020 DISCOVERER, ESA Ram-CLEP, and CRC ATLAS projects, is developing a high-efficiency specular intake and a RF Helicon-based plasma thruster (IPT) for ABEP. This study uses the numerical tool PICLas and it’s Direct Simulation Monte Carlo Method’s (DSMC) to analyse the effect of solar activity and evaluate the validity of the hyperthermal assumption in VLEO for ABEP intake designs. Additionally, the effect of changing intake lengths on important key parameters, such as intake efficiency, mass flow rate, and pressure, is examined. The results show that efficiency decreases with higher solar activity, longer intakes and higher altitudes, with particle temperature having the greatest effect on efficiency, due to its influence on thermal velocity and the molecular speed ratio. An almost linear relationship between efficiency and molecular speed ratio is shown, revealing that the hyperthermal assumption may not be valid for VLEO applications. To achieve the required pressure level for ignition, flexible ABEP operation is recommended to accommodate for varying solar activity, suggesting lower altitude operation during low solar activity and higher altitude operation during high solar activity.