Speaker
Description
There is a substantial lack of knowledge about the environmental effects to the upper atmosphere by the continuously increasing number of satellites that are brought to re-entry after operation. The main constituent of satellite structures is aluminum. Aluminum is injected into the Earth’s atmosphere as a rather new element, as it is only a minor constituent in micrometeorites [1]. However, the impact of this new trace element remains scarcely investigated so far.
Current research assumes the immediate oxidation of molten or evaporated aluminum during re-entry to form aluminum monoxide (AlO). Then, upon cooling, the formation of alumina (Al2O3) particles [2,3], or aluminum hydroxides (Al(OH)x) is discussed in literature [4]. However only few experimental data are available of the processes, especially on the forming solid particles. In our group, we are trying to experimentally evaporate aluminum and collect the resulting solid particles after they eventually cooled down again.
These experimental simulations are performed in the plasma wind tunnels at the Institute of Space Systems (IRS) at the University of Stuttgart. In past experiments we observed the evaporation of aluminum and the formation of AlO. By adding aluminum powder in the plasma flow, we acquired spectral signatures of gaseous Al and AlO, similar to those measured during airborne observations of re-entries [5]. We suspect that the aerothermal environment plays a major role in the particle formation processes. For example, a simple steady evaporation of particles seems not to cover the aerodynamic effects of resident times of particles in the hot core flow. A very first analysis of presumably molten or evaporated particles impacting on copper plates in different locations is used to study the formation processes. The impacting aluminum formed a thin layer coating the copper. Preliminary Powder X-Ray Diffraction and Scanning Electron Microscope analyses by the Department of Chemistry of the University of British Columbia in Vancouver [6,7] show that the layers consist of Al2O3 particles and pure metallic aluminum with a thin top layer of Al2O3.
In the presentation we will explain the newly developed experimental setup to study the processes after the demise of re-entering satellites. We assume several factors influence the process from the spacecrafts’ demise towards the formation of solid particles. These experiments are of high interest to gain an understanding of the increasing number of satellites re-entering the earth’s atmosphere.
[1] Schulz and Glassmeier, Advances in Space Research, 2026.
[2] Park and Layland, Acta Astronautica, 2021.
[3] Maloney et al., JGR Atmospheres, 2025.
[4] Plane et al., JGR Space Physics, 2021.
[5] Loehle et al., Meteoritics and Planetary Science, 2021.
[6] https://www.chem.ubc.ca/x-ray-crystallography
[7] https://emlab.mtrl.ubc.ca/equipment/