Speaker
Description
With increasing presence of small satellites in Low Earth Orbit, investigating their re-entry demise is crucial for the future sustainability of space utilization. This relates not only to the risk of ground impacts of residual components but also to the emission of aerosols and gases in the upper layers of the 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.
SOURCE is a 3U+ CubeSat developed by the IRS together with the small satellite student society of the University of Stuttgart (KSat e.V.). Its mission goal, besides education and technology demonstration, is to gather in-situ measurements during the very early phase of re-entry in altitudes above approximately 130 km. This data should verify and improve existing numerical models and tools for demisability analysis of spacecraft.
In preparation of the PWT experiments, numerical simulations of the demise were performed with the ESA-code SCARAB developed by the HTG GmbH. With the simulation results, critical components were identified and selected for plasma wind tunnel experiments. These include titanium threaded rods, antennas, printed circuit boards (PCBs), carbon fibre reinforced plastic (CFRP) components, cameras, magnetorquers and batteries. During the plasma wind tunnel experiments, the components are exposed to high enthalpy air plasma flows emulating the stagnation point conditions during re-entry. Three different trajectory points relevant for the demise process are selected from the numerical simulations and reconstructed in the PWT by matching enthalpy and total pressure. These trajectory points are ranging from the early re-entry phase in approximately 93 km altitude to the peak heating phase, determined with SCARAB, in approximately 80 km altitude.
The demise process of the selected components in the PWT is monitored with a video camera (Sony Alpha 6400), an infrared thermal camera (FLIR A6751 SLS), a linear pyrometer (KE Technologie GmbH LP3) and thermocouples at selected points of interest. Additionally, optical emission spectroscopy (OES) in the visual and near-infrared range is performed in the stagnation point region (OceanOptics HR4 VIS-NIR). The combination of the named instruments and measurement techniques allows for a time-resolved documentation of quasi individual demise processes in which the emissions of gaseous particles and droplets can be correlated to the heating process of exposed components and materials.
This work presents preliminary results of the visual observation of the demise process combined with temperature measurements and OES data for selected components.
