atmospheric entry plasmas - ulisboa · (photodissociation, photoionization, photodetachment) and...

IntroductionCorrelations & High-Fidelity Sims.

Case Studies

Atmospheric Entry PlasmasFısica dos Plasmas

Mario Lino da Silva, Bruno Lopez, Vasco Guerra and JorgeLoureiro

Instituto de Plasmas e Fusao NuclearInstituto Superior Tecnico, Lisboa, Portugal

March 10, 2014

M. Lino da Silva, B. Lopez, V. Guerra and J. Loureiro, IPFN Reentry Plasmas


Case Studies

What are Atmospheric (Re)-Entry Plasmas

Typical Earth reentry profile Spacecraft entry in Mars Atmosphere (Artist Illustration)

Formation of a strong shockwave upstream of a spacecraft crossingthe upper atmospheric layers at hypersonic speeds.



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Shockwaves as Plasma Precursors



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Comparison Between Entry and Laboratory DischargePlasmas

Reentry Plasma

1/2mv2 ' 7/2kBTtr

v = [7− 10km/s]⇒Ttr = [25, 000K− 60, 000K]

Ttr � Tvib

Gas Discharge Plasma

Tel = 1− 3eV

V–e processes dominant

Ttr � Tvib



Case Studies

Plasma Radiation as a Spacecraft Design Driver

Radiative heating can be a major design driver forlarge or high-speed (≥ 10km/s) entry vehicles

For lower entry speeds, radiative heating maymandate additional thermal protections (e.g. baseheating for Martian entries)

Convective heating mostly depends on groundspecies, radiative heating depends on excited species.Larger uncertainties

Accounting for an additional spectral dimension withgrids with over 106 points. Very computationallyintensive CFRD simulations.



Case Studies

Main Drivers

Do we need to take radiation into account?

Optically thin or thick?

Coupling between flow and radiation?

Equilibrium or non-equilibrium radiation?

Selection of an appropriate radiative database

Other issues (precursor, photo-chemistry, photo-ionisationprocesses)



Case Studies

Aerothermodynamics of Entry Vehicles



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Engineering CorrelationsLarge-Scale CFRD Simulations

Engineering Correlations for Radiation

Engineering Correlations useful when exploring different EDLscenarios

Exploratory parameters: Spacecraft sizing, atmosphericprofiles and composition, entry path and angle, aerodymamiccoefficients, etc...

Correlations then complemented with detailed CFRDcalculations for pre-selected Flight paths, at specificrepresentative entry points (∼5)



Case Studies


Blackbody radiation limit

spectral emissivity of a gas has atheoretical limit given by Planck’slaw

Bν(T ) =2hν3

c2

[exp

(hν

kBT

)− 1

]−1

The spectral integration yields theStefan–Boltzmann Law:∫

ν

Bν(T ) = σT 4The Sun’s emissivity is close to a blackbody

Engineering correlations are based on this upper theoretical limit for theemitted radiation



Case Studies


Stagnation Streamline flux dependence on cone radius

Convective fluxesSutton and Graves, Fay and Riddel correlations:

qwconv = f[√(

dudx

)s

]from Newtonian theory:

[(dudx

)s

]= 1

R

√2p−p∞ρ

qwconv ∝ 1√R

Radiative FluxesOptically Thin shock layer: qwrad =

(Eδ2

)a with δ w R

ρs/ρ∞

qwrad ∝ R

Requirements for minimizing convective and radiativeheat fluxes are mutually exclusive

aE: radiated power, half goes upstream, half to the wall. δ is the shock standoff. s: shock



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Stagnation Streamline flux dependence on entry speed

Convective fluxes

qwconv ≈ 1/2ρ∞u3∞Sta

qwconv ∝ u3∞

Radiative Fluxes

Ts =u2∞

2Cps;

qwrad = σT 4s =

u8∞

(2Cps )4

qwrad ∝ u8∞

Radiation dominates above10km/s

aSt: Stanton number



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Boltzmann and Goulard Numbers

Boltzmann number B−1o , Radiation/Convection ratio:

B−1o =

qradqconv

=σT 4

ρuCpT

Infinite slab approximationa. We also have CpT w u∞/2.

Goulard Number Γ, Radiative cooling parameter

Γ =2qwradqwconv

=2qwrad

1/2ρ∞u3∞

σ: Stefan-Boltzmann constanta

half the radiated power goes upstream, half to the wall



Case Studies


Optically Thin and Optically Thick Limiting Cases

Optically Thin: Γn =4σT 4

s αδρ∞u∞hs

Optically Thicka: Γk =16σT 4

s α3ρ∞u∞hs

Γ < 10−3: radiation is not important

10−3 < Γ < 10−2: radiation is important but coupling isnot necessary

Γ > 10−2: coupling of the radiation to the flowfield isnecessary

The absorption coefficient is related to the opticaltransmissivity such that T = exp(−αδ). Transmissivitygoes from 100% (optically thin) to 0% (optically thick).

aknown as the Rosseland limit



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Radiative Transfer Regimes



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Computational Fluid Radiative Dynamics Simulations

Development of radiative databasesproviding the spectral-dependent emissionεν and absorption α(ν) coefficients forany arbitrary state of the plasma

Accounting for bound, bound–free(photodissociation, photoionization,photodetachment) and free-free(Bremstrahlung) transitions

bound-bound transitions include atomic,diatomic and polyatomic transitions

Radiative transfer equation is then solvedover the computational domain



Case Studies


Development of Spectral Databases

atomic and polyatomic transitionstypically simulated from externalradiative databases (NIST, TopBase,HITRAN)

diatomic transitions databases areexplicitely obtained using appropriatequantum-mechanics models

continuum radiation calculated frompublished absorption cross-sections(e.g. TopBase for atomicphotoionization), or fromsemi-empirical to exact cross-sectionsfor molecular continuum cross-sections

Absorption Coefficient for a 97%CO2–3%N2 Plasma inThermochemical Equilibrium at 5000K and 1bar



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Line-by-Line Models

“Collection” of lines which correspond to the overall quantum-allowedradiative transitions between the internal levels of an atom/molecule.

Selection rules define the quantum-allowed transitions, which must respectangular and spin momentum conservation for atoms and molecules.

Three key parameters:1) Line position considering Planck’s Law: ν = Eu − El/hc ;2) Line intensity: Iν = NuAul∆Eul ;3) Line profile: F (ν − nu0), Voigt (sum of a Lorentz & Gaussian profile).

Radiative spectra obtained through the superposition of these overall lines.



Case Studies


Key Parameters

The fundamental equation for intensity

Iν = NuAul∆EulF (ν − ν0)

can be decoupled in the following variables :

Nu : Level populations :Either a Boltzmann equilibrium distribution, either through Collisional-Radiativenonequilibrium models

Aul : Transition probabilities (Einstein Coefficients):From ”ab-initio” or measured transition moments

∆Eul : Level energies:Fitting and extrapolation of experimentally determined data

F (ν − ν0) : Line profile:Voigt profiles accounting for Doppler and Collisional broadening (depends on the localconditions of the plasma)



Case Studies


The SPARTAN Code

SPARTAN: Simulation of PlasmA Radiation inThermodynAmic Nonequilibrium

Simulation of Earth, Mars and Titan plasma radiation

63 atomic and molecular bound-bond, bound-free(Photodissociation, Photoionization, Photodetachment),and free-free transitions

Simulated species: C, C+, C−, N, N+, N−, O, O+, O−,Ar, Ar+, C2, H2, N2, N+

2 , O2, CN, CH, CO, CO+, NH,NO, OH, CO2

Code freely distributed under a Gnu Public License, seehttp://esther.ist.utl.pt/

SPARTAN Code Logo



Case Studies


Elementary Radiative Processes

El

Eu

? ?

6

hν- hν-

hν-

hν-

hν-

spontaneous emission induced emission absorption

∂Nu

∂t= −NuAul

∂Nu

∂t= −NuBuluν

∂Nl

∂t= −NuBuluν



Case Studies


Derivation of the Radiative Transfer Equation (RTE) (1/2)

Summing the three processes we have

∂Nu

∂t= −NuAul + [NuBul − NuBul ]uν

In Radiative equilibrium the net variation is 0, and radiation is given bythe Planck Blackbody Law

uoν(T ) =8πhν3

c3

[exp

(− hν

kBT

)− 1

]−1

we have

glBlu = guBul

Aul

Bul=

8πhν3

c3



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Derivation of the Radiative Transfer Equation (RTE) (2/2)

Integrating the expressions of the previous slide in volume from we obtainthe classical RTE equation:

cos θdLνdz

= εν − ανLν

with

εν =nuAulhν

4π

α(ν) =

(nu −

guglnl

)Bul

hν

c

which becomes the Beer-Lambert Law in 1D coordinates:

dIνdl

= ε− α(ν)Iν

and after integration:

Iν =ε

α(ν)[1− exp(−α(ν)l)]



Case Studies


Ray-Tracing Methods for Space-Related Heat TransferAnalysis

Ray-Tracing: An exactmethod for determining thequantities of photons whichirradiate a surface.

qν =

∫ π/2

−π/2

∫ π

0Iν(θ, φ)cosθ sin θdθdφ

Iν =ε

α′[1 − exp(−αl(θ))]

Ray-tracing considers full 3D geometries, with the possibility of simpler2D/1D slab geometries.



Case Studies


Ray-Tracing Methods for Space-Related Heat TransferAnalysis

0 5 10 150

1

2

3

4

5

6

7

8

X(m)

Y(m

)

T (K)

500

1000

1500

2000

2500

3000

3500

4000

4500

Complex flow geometries with millions of molecular spectral lines



Case Studies

Titan Entry: HuygensMars Entry: PHOENIX and EXOMARSThe ESTHER Shock Tube

Case Studies



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IST-IPFN Participation is Space Exploration Programmes

Since 2004, IPFN has supported all the major Europeanplanetary exploration Missions

Support to the Huygens Titan entry mission in 2004

Support to the Mars EXPRESS Observation of the PHOENIXentry in 2008

Support to the upcoming Mars robotic exploration MissionEXOMARS in 2016 and 2018

IPFN is developing a new generation European shock-tube(ESTHER) for the support of planetary exploration missionson a total funding of 2M Euros



Case Studies


Huygens Titan Entry (2005)

60 half angle blunted cone

Base diameter: 2.7 m

Nose radius: 1.25 m

Entry module mass: 318.62 kg

Aerodynamic databasesdeveloped by EADS between1991 and 1995.



Case Studies


Huygens Heat Fluxes: Nominal Yelle Atmospheric Profile

Titan Composition: 95% N2–5% CH4

Important Radiator species CN produced in the shock layer.correlations do not work anymore.



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Validation of Aerothermodynamic Databases: Shock-TubesExperiments

TCM2 Shock-Tube at Marseilles, France, was utilized for validatingthe CFRD models used for Huygen’s Entry



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Acquisition Results: CN spectral time-resolved picture

Shot conditions :

Shock TubeClassical mixturepshock=200 Pa

Shock velocityvshock=5680 m/s



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40 Pa test rebuilding, Boltzmann

Non-equilibrium zone, 1s integration Temporal evolution

Validation of Aerothermal databases against simpler (1D,

time-dependent) representative flow conditions



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Coupled CFD-Radiative Simulations of Huygens Entry



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Influence of Radiation and Radiation Coupling



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Mars EXPRESS Observation of the PHOENIX Entry

ESA Mars EXPRESS Orbiterprovided support for PHOENIX2008 Mars Entry

Mars EXPRESS TrackedPHOENIX Entry with his onboardinstrumentation (First Attempt attracking an Entry from anOnboard Satellite).

CFRD simulations prior to entry predicted the IR trail to be the mostemissive.

SPICAM VUV Camera and HRSC Visible Camera tracked the Entry.IR Fourier Spectrometer could not be turned on due to power budgetconstraints.



Case Studies


CFRD Simulations of PHOENIX Entry

PHOENIX Temperature Profiles, t=203s Sample spectrum of the PHOENIX Plume


HRSC Observation in # 5647 during Phoenix EDL : Nadir Context of Limb

° ° SC /

SOWG 38, ESAC, Villafranca: HRSC Future Planning Hoffmann and Hauber 04 June 2008

195° E, 81.5° N: HRSC ND, spatial resolution 12.5 m/pixel, image width 18 km

HRSC Observation in # 5647 during Phoenix EDL : Pointing during 144 SRC Frames

f f f


Phoenix always in center of frame based on latest available Kernel from 25 May

HRSC in # 5647 during Phoenix EDL : SRC 076

Uppermost limb haze layers (detached haze y (layer) enter FOV



Upper limb within FOV



Optically thick limb at edge of FOVg

•No hints for flash or brightening

•Pointing and timing seem to be correct

Phoenix not detected:•Upper limit for energy releaserelease

•Consistent with continuous telemetry link


ESA UNCLASSIFIED – For Official Use

ExoMars Programme: two missions launched in 2016 and 2018.• The 2016 mission consists of the Trace Gas Orbiter (TGO) and the EDL Demonstrator Module (EDM)• The 2018 mission consists of the Rover, accommodated inside a Descent Module (DM) and carried

to Mars by a Carrier Module (CM)• Large international cooperation with Roscosmos and some contributions from NASA

Proton

Trace Gas Orbiter (TGO)

ExoMars Programme Mission Architecture

2016 Mission 2018 Mission

Carrier Module & Descent Module

Rover + Landed PlatformEDL Demonstrator Module (EDM)

+

Proton


Case Studies


Radiative Transfer Towards Mars EXPRESS

Optical path Transmissivity Raddiation collected by one pixel of the Mars EXPRESSinstrumentation

Radiation in the VUV-Visible region was not detected, IR radiation was

predicted to be detected if the instrument had been switched on



Case Studies


Spectral Database for CO2–N2 Mixtures

CO2 Infrared

CO Infrared

CO 4+

CO 3+

CO Angstrom

CO Triplet

CN Violet

CN Red

C2 Swan

C2 Phillips

C2 Mulliken

C2 Deslandres–D’Azambuja

C2 Ballik–Ramsay

O2 Sch.–Runge

O2 Sch.–Runge Cont.

N2 1+

N2 2+

NO Gamma

NO Beta

NO Delta

NO Epsilon

NO Beta

C Atomic

C Photoionization

N Atomic

N Photoionization

O Atomic

O Photoionization

C− Photodetachment

N− Photodetachment

O− Photodetachment

CO2 Photoionization

N2 Photoionization

O2 Photoionization

CN Photoionization

CO Photoionization

NO Photoionization



Case Studies


Radiative Power for CO2–N2 Mixtures: Comparison WithOther Spectral Databases

1000 2000 3000 4000 5000 6000 7000 8000 9000 1000010

0

102

104

106

108

1010

1012

Temperature (K)

Rad

iativ

e P

ower

(W

/m3 ) CO

2 IR Other Systems

Comparison of the overall temperature dependent radiative power of CO2 IR radiation (red) and for the other

radiative systems (black) for an atmospheric pressure, Martian-type CO2–N2 plasma. Comparison is carried for the

SPARTAN code database (full lines) and the EM2C database (dotted lines).



Case Studies


Example of a Ray Departing from the Afterbody Plume;PH (1/2)

103

104

105

10−15

10−10

10−5

100

Wavelength (A)

Inte

nsity

(W

/m2 /c

m−

1 )

Intensity at ray departureIntensity at ray arrival



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Example of a Ray Departing from the Afterbody Plume;PH (2/2)

4.17 4.1705 4.171 4.1715 4.172 4.1725

x 104

10−1

100

101

Wavelength (A)

Inte

nsity

(W

/m2 /c

m−

1 )

Intensity at ray departureIntensity at ray arrival



Case Studies


Comparison of Stagnation Streamline and BackcoverShoulder Spectra; PH

VUV-Visible radiation higher for the stagnation streamlinepoints

For both points, CO2 radiation spectral intensity is severalorders of magnitude above Visible-VUV radiation



Case Studies


Contribution of Radiative Fluxes above 1µm to the OverallRadiative Power; Large Spacecraft Configuration

0 5 10 15 20 25 30 35 40 45 5099.8

99.82

99.84

99.86

99.88

99.9

99.92

99.94

99.96

99.98

100

Wall Point

IR R

adia

tion

Con

trib

utio

n (%

)

PHPPP28P23SHA

Values for the smaller spacecraft configuration are similar. Other studies in the scope

of the ESA TC3 testcase confirm such findings for CO2–N2 mixtures (CN and C2

radiation less than 3% overall in the stagnation streamline point.



Case Studies


The ESTHER Shock-Tube Project

European Shock Tube for High Enthalpy Research

European Space Agency project

International consortium, led by Instituto Superior Tecnico, for thedevelopment and comissioning of a shock-tube facility for planetaryexploration research in the high speed regime

Consortium partners include:

Fluid Gravity Eng. (Ermsworth, UK),Universite de Provence (Marseille, France),Ingenieurie Systemes Avances (Bordeaux, France),Moscow Institute for Physics and Technology (Moscow, Russia),Instituto de Soldadura e Qualidade (Lisboa, Portugal),Shock-Waves Laboratory (Aachen, Germany),University of Manchester (Manchester, UK),Universite Blaise Pascal (Clermont–Ferrand, France),Universite Paris VI (Paris, France)



Case Studies


Shock-Tube Characteristics

Facility capable of reproducing shock waves for gas mixtures simulatingthe atmosphere of Earth, Mars and Venus (CO2–N2), Titan (N2–CH4).

High pressure reached in the driver section through the deflagration of ahigh-pressure H2–O2 mixture. This allows a quick-rise in pressure,enabling 3–4 shots per day, but needs special precautions related to thepresence of explosive gases.

Shock velocities of v '4–12km/s, allowing the simulation of orbital (slowspeed) and interplanetary superorbital entry plasma flows.

High-speed automated diagnostics (MHz) for control, acquisition, andcollecting light emitted by the plasma.



Case Studies


Shock-Tube Design (1/4)

High Pressure Driver Section

600 bar maxium working pressure

900 bar design limit

Internal diameter 200mm

Outer diameter 360mm

Internal length 1.5m

Nominal mixture70%He,20%H2,10%O2

Initial pressure 10 to 50 bar

High pressure ignition and safetysystem

Combustion gas preparation systemand induction system includingmixing, storage, valves, probes andgauges

Gasket system with rupture pressures60 to 600 bar



Case Studies



Compression Tube (or second stage)

Internal diameter 130mm

Outer diameter 150mm, length 6.5m

Initial pressure 0.1-0.5 bar (optimized for each run)

Gasket system with rupture pressures 5 to 25 bar



Case Studies



Working Section

Internal diameter: 80mm

outer diameter: 150mm

length from diaphragm to window:4m

total internal length to the dumptank: 5.4m

Initial pressure 10 to 1000Pa

Pumping system: minimum pressureof 10-8 mbar during cleaningprocedures, ensure known initial testgas composition.

Working gas preparation andinduction system including probesand gauges.

Windows (UV/VUV transparent)and window mounting system.

Shock speed / pressure measurementsystem.

Diaphragm to dump tankM. Lino da Silva, B. Lopez, V. Guerra and J. Loureiro, IPFN Reentry Plasmas


Case Studies



Dump Tank

Post window section lead in tube to dump tank

Pressure range, vacuum to 2bar pressure post shot.

Diameter: 1 m

Length: 3 m


Outside view of the laboratory and view of the experimental hall

ESTHER shock-tube

Hypersonic Plasmas LaboratoryEuropean Shock-Tube for High Enthalphy Research

Facility Specifications

Length: 16m Test-section diameter: 80mm Shock Velocities: 4-12+ km/s Pre-shock pressures: 0.1-100+ mbar Planetary compositions: Air (Earth), CO2-N2 (Venus, Mars), N2-CH4 (Titan)

Shock-Tube: A facility for reproducing the conditions of an atmospheric entry Support to planetary exploration missions and meteoroids planetary protection research 2M€ total funding, 1,75M€ funding from the European Space Agency First facility of its class to be built in the last 30 years in Europe, located at IST-IPFN World class facility capable of reaching superorbital shock-speeds in excess of 10km/s

Example of a shock-induced plasma

atmospheric entry plasmas - ulisboa · (photodissociation, photoionization, photodetachment) and...

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