# Presentation: 480104

## Ablative thermal protection systems for entry in Mars atmosphere.A presentation of materials solutions and testing capabilities

- _Jean-Marc BOUILLY_, Francine BONNEFOND,Ludovic DARIOL, Pierre JULLIEN, Frédéric LELEU
- Prepared for
**4th International Planetary Probe Workshop****Pasadena, CA, USA June 27-30, 2006**

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## Presentation Outline

- ExoMars mission overview
- ExoMars Descent Module
- Norcoat-Liege
- Composition and manufacturing
- Heritage
- Qualification for Mars Missions
- Test facilities
- Modeling
- Norcoat Liege preferred to Alternative Solutions
- Growth potential
- Conclusion

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## ExoMars Mission Overview

- Launch in 2011 (backup 2013)
- Carrier Module will release Descent Module
- Payloads to land on the surface
- Rover + Pasteur Payload for exobiology and geological research
- Geophysics/Environment Package (GEP) for Martian geophysics and ambient conditions

***from ASTRIUM / EADS-ST phase A study***

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## ExoMars Descent Module : Main features(from ASTRIUM / EADS-ST phase A study)

- ~ 3.80 m diameter
- ~ 1200 kg
- TPS = Norcoat-Liege on Frontshield & Back-Cover
- Frontshield 180 kg(TP ~50%)60 large panels 10 mm+ 50 small panels 6 mm
- Back-Cover 180 kg(TP ~25%)80 panels 6 mm

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## TPS trade-offNorcoat Liege preferred to Alternative Solutions

- AQ60
- low density silica / phenolic material used for Huygens heatshield
- Norcoat-Liege allows a simpler design, an easier implementation and a slightly lower mass budget
- PICSIL
- low density silicone-based ablator baseline for European CTV studies. (1995-96)
- less optimized than Norcoat-Liege for a mission to Mars, due to the lower thermal solicitations
- higher maturity of Norcoat-Liege

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## NORCOAT® LIEGEComposition and manufacturing

- _PROCESS SUMMARY_
- Realization of panels in an heated press by cork powder agglomeration
- Cutting, machining and forming
- Bonding under pressure on the equipment
- Possibility of outgassing treatment for space applications
- Applicable on developable or not very complex surfaces
- _CHARACTERISTICS_
- Density: 0.47
- Thickness: from 1.5 to 150 mm

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## Norcoat-Liege heritageARD cone & back-cover

- Panels 19 mm thick
- Implementation of many singularities
- thrusters, TPS experiments, measurement devices,antennas, access doors, etc...
- Successful flight on October 21st 1998
- Very nice aspect after recovery

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## Norcoat-Liege heritageBEAGLE 2 Frontshield & back-cover

- 31 tiles on Frontshield
- 9 mm, 3.9 kg total mass (< 4.5 kg/m2)
- tiles + several singularities on Back-Cover
- 3 to 6 mm, 2.0 kg total mass (< 2.5 kg/m2)
- Very late design modifications implemented

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## Norcoat-Liegeadaptation to Mars missions

- Outgassing : elaboration of appropriate thermal treatment
- Selection of optimal : Temperature, Vacuum level, Duration
- Stringent cleanliness conditions to meet decontamination / sterilisation requirements (planetary protection regulations)
- Screening and selection of appropriate method based on medical experience
- Two different processes established for FS & BC
- Dust erosion (joined CEA-CESTA / EADS-ST approach)
- Modelling
- Test facilities

**Bonding in class 100 room of sterilised tiles for Beagle2 back-cover**

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## Norcoat-Liege Qualification for Mars Missions (1) Stagnation point tests

- IPM Russia
- Air and CO2
- Up to ~1100 kW/m2
- COMETE
- Air ; up to ~2000 kW/m2
- VKI Belgium
- Comparison Air / CO2
- Up to ~2000 kW/m2
- 	Very good behaviour
- 	No noticeable difference under air or CO2

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## Norcoat-Liege Qualification for Mars Missions (2) Tangential flow tests - EADS-ST SIMOUN facility

- BEAGLE 2
- CO2
- Up to ~800 kW/m2
- NETLANDER
- Air
- up to ~1800 kW/m2
- 	Very good behaviour of the whole arrangement (including joints, steps & gaps)
- 	Capability of the material certainly significantly higher than the experienced test results (limited to required values)

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## Test exploitation & determination of material thermal characteristics (Beagle2)

- AMARYLLIS 2D model, with pyrolysis and surface recession
- iterative process to optimise the restitution of measured temperatures, compared to computed ones.
- Elaboration of material thermal model, including ablation and pyrolysis phenomena

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## SIMOUN facility overview

**SIMOUN facility overview**

- SIMOUN SET UP :
- - Generator
- - Test chamber
- - Vacuum system
- - Sample in flow

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## SIMOUNMain Characteristics

**STAGNATION PRESSURE****	****   ****	****    ****	****                   1 TO 18 BAR**
**STAGNATION ENTHALPY****	****	****                         4 TO 14 MJ/Kg(air)**
**FLOW****	****	****	****	****	****	****     air, N2, CO2**
**RUN TIME****	****	****	****                      a few sec. to 30 min.**

**STAGNATION POINT**
**NOZZLE** :  Contoured, Mach number 4.5
**SAMPLE** : Diameter 50 mm
- 	   Pressure : 50 to 200 mbar
- 	   Heat flux : 700 to 2500 kW/m2  *
**Extended field** :
- 	   Pressure : 200 to 500 mbar
- 	   Heat flux : 2500 to 4000kW/m2
- For tests duration <1mn : up to 6000kW/m2 expected (still to validate)
-  * : cold wall conditions

**FLAT PLATE &  WEDGE**
**NOZZLE** :  Superelliptic, Mach number 5
**SAMPLE** : 300 x 300 mm2 , 150 mm thick
- 	   Angle of attack : 0 to 16°
- 	   Pressure : 3 to 180 mbar
- 	   Heat flux : 20 to 1600 kW/m2  *
- For tests duration <1mn : up to 2000kW/m2
- expected (still to validate)
- * : cold wall conditions

**SIMOUN****Main Characteristics**

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**Notes:**
Continuous effort to upgrade the facility and extend its capabilities and domain of use.

## Dust erosion

**STEP I**

**STEP II**

**STEP III**

**STEP IV**

**STEP V**

- Step I : particles description
-  Nature and size
-  Distribution versus altitude
-  Particles velocity
- Step II : shock particles interaction
-  Particles modification (break up)
-  Flow perturbation
- Step III : shock layer crossing
-  Particles deceleration, deviation and heating
- Step IV : particles TPS interaction
-  TPS erosion
-  Heat fluxes increase on TPS : due to wallroughening and earlier transition to turbulence
- Step V : debris
-  Effects on the boundary layer
-  « Debris shielding »

**Dust erosion**
**Phenomenon and Methodology Overview**

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## Test facilitiesAQTIL

- Study of alumina particles impact on Ariane 5 (due to boosters separation rockets)
- Adaptation of existing plasma torch
- Development of specific injection device
- Implementation of several diagnostic techniques for control of particles seeding
- Velocity
- Homogeneity
- State (solid or melt)
-  facility is now available and fully qualified for TPS characterisation under particles impingement

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## SIMOUNAdaptation for particle injection

- Application on SIMOUN of the same methodology as  on AQTIL :
- Nozzle exit particle injection
- Specific diagnostics
- To be validated in  :
- Low ambient pressure
- Supersonic flow
- First step : Stagnation point (in 3rd quarter 2006)
- Then, implementation completed for plane board tests

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## R & D approach

- Detailed characterisation work performed during the past years
- In association with local Research Centers (CNRS, CRPP)
- Influence of main molecules constituting the material
- Analysis of degradation process
- Very interesting results, especially wrt stability at high temperature
- Basis for thorough understanding and future improvements

- Norcoat-Liege aftercarbonization @ 2000°C

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## Growth potential

- Better comprehension of the role of each constitutive molecule  basis for a more detailed theoretical modelingenables future tailored improvements of the material.
- Two attractive perspectives to enlarge the use of this type of material to a wider domain.
- Inclusion of a mechanical reinforcement in the material, in order to strengthen the char layer.
- Search for a lightened material, in view of application on aft body of entry probes

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## Conclusion

- EADS-ST ready to bring a significant contribution to ExoMars development and future success
- Thermal protection
- Qualification facilities
- More generally, all the disciplines required for atmospheric entry (AED, ATD,...)
- These technologies and techniques can obviously also serve any future scientific mission with atmospheric entry probe

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## 
Thank you for attention

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