Vrije Universiteit Brussel

Comprehensive characterization of the aerothermomechanical response of space debris toatmospheric entry plasmasFagnani, Andrea; Chazot, Olivier; Hubin, Annick; Helber, Bernd

Publication date:2019

Document Version:Final published version

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Citation for published version (APA):Fagnani, A., Chazot, O., Hubin, A., & Helber, B. (2019). Comprehensive characterization of theaerothermomechanical response of space debris to atmospheric entry plasmas. Poster session presented at10th VKI PhD Symposium, Rhode-Saint-Genese, Belgium.

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Download date: 18. Dec. 2020

Comprehensive characterization of the aerothermomechanical response of space debris to atmospheric entry plasmas

Andrea Fagnani1,2, Olivier Chazot1, Annick Hubin2, Bernd Helber1

1Aeronautics and Aerospace Department, von Karman Institute for Fluid Dynamics2Materials and Chemistry Department, Vrije Universiteit Brussel

Overview of the research projectSatellites orbiting Earth offer unrivalled possibilities for research and commercial applications; however, space activities have left thousands of objects inorbit which are no longer functional, namely, space debris. Their number is predicted to increase exponentially in the future and, due to their hypervelocitymotion, collision of fragments with existing and new missions can lead to a catastrophic break up, generating even more debris in a cascade effect [1].

To achieve a sustainable space environment, the Design for Demise (D4D) strategy proposes to conceive any space object for the end-of-life disposalthough a destructive atmospheric entry. Yet, experience has demonstrated that several parts can survive almost intact, thus representing risk on ground[2]. The overarching objective of this research is to contribute with multi-scale experiments and modelling to advance the predictive capabilities of theaerothermal demise of metallic and silicate components.

A multi-physics melting-ablation problem

Plasma wind tunnel experiments Modelling the experimental environment

References

Microscale surface analysis

Figure 2: Main physical phenomena involved in the multiphase melting-ablation problem, eventually leading to the material demise

Atmospheric entry brings about extreme gas-surface interactionphenomena (Fig. 2), causing the material degradation and eventuallyleading to demise if all the mass is consumed:

• aerothermal heating induces melting and formation of gas-liquid andliquid-solid interfaces;

• the liquid layer is removed by flow shear forces or by thermo-chemicalphenomena such as evaporation;

• molecular species dissociate due to the extreme gas temperatures,recombine in the boundary layer and diffuse towards the surface;

• at the wall, heterogeneous chemistry occurs, including catalysis,nitridation and oxidation reactions.

At the Electrochemical and Surface Engineering group (SURF) laboratoriesat VUB we will apply advanced analysis techniques to understand criticalsurface processes occurring upon exposure of metals and silicates to high-enthalpy reactive flows:

• Scanning Electron Microscopy (SEM) will be used to image changesin surface morphology;

• Energy Dispersive X-Ray Spectroscopy (EDX) will characterizealterations of surface chemical composition under ablation;

• X-Ray Photoelectron Spectroscopy (XPS) will provide quantitativeelemental analysis of the surface and information on the oxide scales.

Data will serve to refine finite-rate surface oxidation models and validate numerical simulations.

A withstanding challenge in high-enthalpy facilities is the scaling of thedriving physical phenomena, as well as the correct modelling of theexperimental environment.

We propose to perform a dedicated experiment design starting with the1D coupled flow-material solver developed by Dias et al. [3].Successively, a melting-ablation model will be implemented in PATO [4] toperform 2D material response simulations.

This procedure will guide the design of the test sample geometries, alsoaddressing the correct flow conditions.

The VKI Plasmatron is the world’s largest Inductively Coupled Plasma (ICP)facility. It allows to reproduce the chemically reacting boundary layer on are-entry body thanks to a high-purity plasma flow.

This work aims at developing a robust test methodology to provide highquality data for comparison with simulation codes. Supersonic test will beperformed for the first time in an ICP facility on these material classes.

The experimental set-up (Fig. 4) will include:

• Non intrusive temperature measurementswith pyrometry (1), radiometry (2) andinfrared thermography (3);

• Time resolved recession measurements withhigh-speed camera imaging (4);

• Plasma flow investigation with opticalemission spectroscopy (5);

• In-depth temperature measurement in thematerial sample with thermocouples (6).

Figure 4: Sketch of the experimental set-up.

Figure 5: Steel type 316L sample before and after plasma exposure (left) and SEM image of oxidised surface from [5] (right).

Figure 6: Sketch of the quasi-1D coupled flow-material solver from Dias et al. [3] (left) and representative 2D material ablation in PATO performed with input transfer coefficients (right) .

This research is funded by the Research Foundation – Flanders (FWO) fellowship n°1SB3219N.

1. H. Klinkrad, Space Debris – Models and Risk Analysis, Springer-Verlag Berlin Heidelberg, 2006;2. Y. Prevereaud et al., Acta Astronautica, vol. 122, pp. 258-286, 2016;3. B. Dias et al., AIP Conference Proceedings 1786, 160004, 2016;4. J. Lachaud et al., Journal of Thermophysics and Heat Transfer, vol. 28, no. 2, pp. 191-202, 2014;5. Vesel et al., Applied Surface Science, vol. 255, pp. 1759-1765, 2008.

Figure 3: Picture of the 160 mm diameter plasma jet and test probe in the VKI Plasmatron facility.

Figure 1: Snapshot of the aerothermal demise of theATV-4 space cargo ship, as observed from theInternational Space Station in October 2013 (ESA).

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