Speaker
Description
As the number of small satellites in Low Earth Orbit grows, understanding their re-entry demise becomes increasingly crucial for ensuring the sustainability of space utilization. This includes risks associated with ground impacts from incompletely demised components and the release of aerosols and gases into the upper atmosphere. The SOURCE PWK project, funded by the German Aerospace Center (DLR) and carried out by the University of Stuttgart’s Institute of Space Systems (IRS), aims to investigate the demise behaviour of CubeSats. The investigation employs both numerical demise simulations of the CubeSat mission SOURCE (Stuttgart Operated University Research CubeSat for Evaluation and Education) and plasma wind tunnel (PWT) experiments on its critical components.
The project employs a two-pronged approach, combining numerical simulations of CubeSat missions like SOURCE (Stuttgart Operated University Research CubeSat for Evaluation and Education) with plasma wind tunnel (PWT) experiments on critical components. SOURCE, a 3U+ CubeSat developed by IRS in collaboration with the University of Stuttgart's small satellite student society (KSat e.V.), is expected for launch not earlier than 2025. Beyond educational and technological demonstration objectives, its mission includes gathering in-situ measurements during early re-entry phases above approximately 130 km altitude. These data can be used to refine existing numerical models and demisability analysis tools for spacecraft.
Numerical simulations using the ESA-code SCARAB, developed by HTG GmbH, preceded the PWT experiments, aiding in identifying critical components such as titanium threaded rods, antennas, printed circuit boards (PCBs), carbon fiber reinforced plastic (CFRP) elements, cameras, magnetorquers, and batteries. PWT experiments expose these components to high enthalpy air plasma flows simulating conditions at the stagnation point during re-entry. Trajectory points relevant for the demise process were selected from simulations, ranging from the early re-entry phase at approximately 93 km altitude to the peak heating phase around 80 km altitude.
The process of component demise in the PWT is monitored using a video camera (Sony Alpha 6400), an infrared thermal camera (FLIR A6751 SLS), a linear pyrometer (KE Technologie GmbH LP3), and thermocouples at specific points of interest. Optical emission spectroscopy (OES) is also performed in the stagnation point region using the visual and near-infrared range (OceanOptics HR4 VIS-NIR). The named instruments and measurement techniques can be combined to document the demise processes in a time-resolved manner. This allows for the correlation of the emissions of gaseous particles and droplets to the heating process of exposed components and materials.
This work presents the visual observation of the demise process, along with spatially and time-resolved temperature measurements and OES data for the tested components. The results are compared to the SCARAB re-entry simulations to identify significant deviations where demise models can potentially be improved. Finally, conclusions are drawn regarding the expected demise during SOURCE’s actual re-entry, specifically, and CubeSats in general.
