1. IPPW 2007 Bordeaux 25-29 june 2007 Page 1 This document is property of CEA/CESTA and shall not be reproduced without its authorization OVERVIEW OF DUST EFFECTS DURING MARS ATMOSPHERIC ENTRIES MODELS, FACILITIES AND DESIGN TOOLS Montois I. (1), Pirotais D. (1), Conte D. (2), Sauvage N. (2), Chazot O. (3) (1) CEA - BP2 - 33114 Le Barp - France - dominique.pirotais@cea.fr - isabelle.montois@cea.frdominique.pirotais@cea.frisabelle.montois@cea.fr (2) EADS Astrium - France (3) Von Karman Institute -72 Chaussée de Waterloo, 1640 Rhode-St-Genese, Belgium – chazot@vki.ac.bechazot@vki.ac.be

2. IPPW 2007 Bordeaux 25-29 june 2007 Page 2 This document is property of CEA/CESTA and shall not be reproduced without its authorization CONTEXT Mars atmosphere periodically witnesses dust storm that may leave solid particles in suspension for a long time. According to their high velocities, when reentry vehicles encounter such dust clouds, even small particles can induce significant damage to the TPS

3. IPPW 2007 Bordeaux 25-29 june 2007 Page 3 This document is property of CEA/CESTA and shall not be reproduced without its authorization Charred layer erosion is the most evident effect of dust clouds encounter other less awaited effects are present that need modelling for a comprehensive assessment of dusty flows This paper proposes an overview of these effects within the frame of Mars entries

4. IPPW 2007 Bordeaux 25-29 june 2007 Page 4 This document is property of CEA/CESTA and shall not be reproduced without its authorization Dust laden flows : main issues II III IV VI I V I : particles specification II : shock/particles interactions III : shock layer crossing IV : impact @ wall V : ejecta VI : wake seeding

5. IPPW 2007 Bordeaux 25-29 june 2007 Page 5 This document is property of CEA/CESTA and shall not be reproduced without its authorization Step I : particles description Particles concentration and distribution versus altitude Particles velocity or vehicle velocity Nature and size Phenomenon and Methodology overview Since the first measures of Viking probes, knowledge of Mars atmosphere particles has continuously improved and is still improving. Provided via databases : our baseline description is EMCD Martian Climate global Modelling.

6. IPPW 2007 Bordeaux 25-29 june 2007 Page 6 This document is property of CEA/CESTA and shall not be reproduced without its authorization Maximum altitude of dust : ~75 km Particles size : eff r eff (μm) Case 10.51 Case 212 Case 30.21 Case 40.22 I) Dust description

7. IPPW 2007 Bordeaux 25-29 june 2007 Page 7 This document is property of CEA/CESTA and shall not be reproduced without its authorization Dust content and dust mixing level total amount of particles : M where  is the optical depth DR is a scaling parameter (m 2 /g) Dust particles loading –  = 5 Dust particles mixing ratio –  = 5

8. IPPW 2007 Bordeaux 25-29 june 2007 Page 8 This document is property of CEA/CESTA and shall not be reproduced without its authorization DUST MASS FLUX (  =1) Some orders of magnitudes

9. IPPW 2007 Bordeaux 25-29 june 2007 Page 9 This document is property of CEA/CESTA and shall not be reproduced without its authorization Step I : particles description Particles concentration and distribution versus altitude Particles velocity or vehicle velocity Nature and size Phenomenon and Methodology overview Step II : shock particles interaction Particles modification (break up) Depends on the shock characteristics And on the particles mechanical characteristics and nature shock oscillations & associated flow perturbation Essentially included in margins for engineering purposes

10. IPPW 2007 Bordeaux 25-29 june 2007 Page 10 This document is property of CEA/CESTA and shall not be reproduced without its authorization Step I : particles description Particles concentration and distribution versus altitude Particles velocity or vehicle velocity Nature and size Phenomenon and Methodology overview Step II : shock particles interaction Particles modification (break up) Depends on the shock characteirstics And on the particles mechanical characteristics and nature Particles slow down Flow perturbation Step III : shock layer crossing Particles deceleration and deviation Particles heating, melting, ablating… Energy dissipation/momentum transfer : flow modification Consequences on the gas mixture behaviour HEAT FLUXES MODIFICATIONS @ WALL

11. IPPW 2007 Bordeaux 25-29 june 2007 Page 11 This document is property of CEA/CESTA and shall not be reproduced without its authorization AUGMENTED HEATING EVIDENCE Fleener – Watson Convective heating in dust laden hypersonic flows AIAA Paper 76-319, 1973, Palm Springs, CA

12. IPPW 2007 Bordeaux 25-29 june 2007 Page 12 This document is property of CEA/CESTA and shall not be reproduced without its authorization Step I : particles description Particles concentration and distribution versus altitude Particles velocity or vehicle velocity Nature and size Phenomenon and Methodology overview Step II : shock particles interaction Particles modification (break up) Depends on the shock characteirstics And on the particles mechanical characteristics and nature Particles slow down Flow perturbation Step III : shock layer crossing Particles decceleration and deviation Particles heating Energy dissipation :modification of flow Consequences on the gas mixture behaviour Step IV : particles TPS interaction wall roughening Early transition Increased heat fluxes TPS erosion « Clear atmosphere like » phenomena Quantitative data ? Characterization issues

13. IPPW 2007 Bordeaux 25-29 june 2007 Page 13 This document is property of CEA/CESTA and shall not be reproduced without its authorization Erosion characterization issues Multiple vs single impact Hot vs cold material Charred vs virgin Fluid flow coupling vs uncoupled Low vs high velocities

14. IPPW 2007 Bordeaux 25-29 june 2007 Page 14 This document is property of CEA/CESTA and shall not be reproduced without its authorization Erosion characterization issues All at a time : –Hard to perform –Difficult to interpret Split variables + physical modeling

15. IPPW 2007 Bordeaux 25-29 june 2007 Page 15 This document is property of CEA/CESTA and shall not be reproduced without its authorization Single impact (hot/cold) Objectives : tests of material under a single particle impact at very high velocity –Velocities up to 5000 m/s –Cold material –Particle : diameter 200 microns Extension to heated material (up to 3000 K) Expansion zone (10 mbar, AR) Diaphragm Sample Hydrogen (10b) CEA MICA Light gas gun facility Velocity Heat Char Debris Single Coupling Material Part. size

16. IPPW 2007 Bordeaux 25-29 june 2007 Page 16 This document is property of CEA/CESTA and shall not be reproduced without its authorization Multiple impacts (hot/cold) EADS AQTIL & SIMOUN Velocity Multiple Coupling Heat Char Part. size + uncoupled flow analysis ONERA R2CH VKI Minitorch

17. IPPW 2007 Bordeaux 25-29 june 2007 Page 17 This document is property of CEA/CESTA and shall not be reproduced without its authorization Step I : particles description Particles concentration and distribution versus altitude Particles velocity or vehicle velocity Nature and size Phenomenon and Methodology overview Step II : shock particles interaction Particles modification (break up) Depends on the shock characteirstics And on the particles mechanical characteristics and nature Particles slow down Flow perturbation Step III : shock layer crossing Particles decceleration and deviation Particles heating Energy dissipation :modification of flow Consequences on the gas mixture behaviour Step IV : particles TPS interaction TPS erosion Heat fluxes augmentation on TPS : due to wall roughening and earlier transition to turbulence Step V : debris Effects on the boundary layer « Debris shielding »

18. IPPW 2007 Bordeaux 25-29 june 2007 Page 18 This document is property of CEA/CESTA and shall not be reproduced without its authorization Debris shielding Simple approaches indicate low probability of occurrence Hypothesis 1 : ejecta swept off before following impact Hypothesis 2 : ejecta accumulate in BL (1 ms)

19. IPPW 2007 Bordeaux 25-29 june 2007 Page 19 This document is property of CEA/CESTA and shall not be reproduced without its authorization MODELING ISSUES How to simulate and assess erosion with validated models and tools An exemple : recession code

20. IPPW 2007 Bordeaux 25-29 june 2007 Page 20 This document is property of CEA/CESTA and shall not be reproduced without its authorization Ablation code simplified chart

21. IPPW 2007 Bordeaux 25-29 june 2007 Page 21 This document is property of CEA/CESTA and shall not be reproduced without its authorization Erosion + ablation code “simplified” chart

22. IPPW 2007 Bordeaux 25-29 june 2007 Page 22 This document is property of CEA/CESTA and shall not be reproduced without its authorization Discussion assumed first priority for a probe TPS assessment vs dust : –dust scenario –Material impact response assumed 2nd priority : heat fluxes modifications : –Transition onset –Rough wall effects –Flow perturbations

23. IPPW 2007 Bordeaux 25-29 june 2007 Page 23 This document is property of CEA/CESTA and shall not be reproduced without its authorization DISCUSSION : EXAMPLE MATERIAL EROSION RESPONSE Area of interest

24. IPPW 2007 Bordeaux 25-29 june 2007 Page 24 This document is property of CEA/CESTA and shall not be reproduced without its authorization CONCLUSION We favor splitting variables to analyze the various physical phenomena Then get as many as possible relevant data (erosion characteristics, flux enhancement …) for each single phenomena to model Build simulation tool in order to couple separately derived models Weigh modeling effort wrt anticipated benefits (take justified margins otherwise e.g. transition onset)

25. IPPW 2007 Bordeaux 25-29 june 2007 Page 25 This document is property of CEA/CESTA and shall not be reproduced without its authorization THANK YOU FOR YOUR ATTENTION COMMENTS WELCOME

26. IPPW 2007 Bordeaux 25-29 june 2007 Page 26 This document is property of CEA/CESTA and shall not be reproduced without its authorization MARS DUST STORMS