Ground test facility for rarefied atomic oxygen flows

• Subject Area: Fluid Mechanics, Technical Thermodynamics and Thermal Energy Engineering ; Astrophysics and Astronomy
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563081791

This application relates to a ground test facility in which gas-surface interactions of space-relevant materials can be investigated under Very Low Earth Orbit (VLEO) conditions. In the facility, a plasma generator will generate an almost completely dissociated, fast, so-called hyperthermal flow of atomic oxygen. A portion is extracted at high speed via a skimmer with a small opening into a high-vacuum chamber with a large mean free path in order to investigate the interaction with material samples. A mass spectrometer determines the particle density of reflected oxygen as a function of the incident and reflected angle. In addition, material samples are exposed to high-energy atomic oxygen over a longer period of time in order to investigate mass loss and changes to the surface. A modular design of the system with exchangeable plasma generator and skimmer allows the experimental parameters to be adapted over a wide range. The application is closely linked to the CRC "Advancing Technologies of Very Low Altitude Satellites - ATLAS", which was established at the University of Stuttgart on April 1, 2024 to research the scientific basis for conquering the VLEO area. Essential for this is a better understanding of the gas-wall interactions that occur, which determine, for example, the aerodynamic drag and thus the lifetime of satellites as well as the efficiency of control surfaces or new types of air-breathing electric propulsion thrusters. The VLEO atmosphere consists mainly of atomic oxygen, whose chemical interaction with surfaces can also lead to significant material erosion. The advantages of the VLEO area with lower flight altitudes of less than 450 km are, for example, improved possibilities for Earth observation or telecommunications. The residual atmosphere also slows down passive satellites more than in traditional orbits, so that they quickly lose altitude at the end of operation, enter the denser atmosphere and burn up. This enables the rapid and purely passive disposal of satellites and avoids long-lived space debris. Beyond the CRC ATLAS, the facility is important for the further development and improved calibration of sensors for atomic oxygen. These sensors, known as FIPEX sensors, have been used successfully for several years with various international partners in atmospheric research on sounding rockets and satellites to measure the atomic oxygen distribution at high altitudes. Following the successful commissioning and extensive characterization of the VLEO system, it is also expected to play an important role in the investigation of relevant flight measurement technology and the development of subsystems for low-flying satellites in the long term.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Bodentestanlage für verdünnte atomare Sauerstoffströmungen
• Applicant Institution: Universität Stuttgart
• Leader: Professor Dr.-Ing. Stefanos Fasoulas