test case definitions -...

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SPACECRAFT DEMISE

TEST CASE DEFINITIONS

Version 1.9. Before continuing, check on scdw.rtech.fr whether a newer version of this document

is available.

NOM et SIGLE DATE et SIGNATURE

Rédigé par

Bastien PLAZOLLES

(R.TECH)

Vérifié par

Vincent Rivola

(R.TECH)

Approuvé par

Martin Spel (R.TECH)

http://scdw.rtech.fr/SCDW_WEB/UK/PAGE_Information.awp

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Table of Contents

Table of Contents ............................................................................................................................ 2

Documents ...................................................................................................................................... 4

Reference documents ...................................................................................................................... 4

Modifications .................................................................................................................................. 4

Glossary .......................................................................................................................................... 4

Introduction .................................................................................................................................... 5

1 Directory structure .................................................................................................................... 6

2 Overview of data format ........................................................................................................... 6

3 Aerodynamic models validation ................................................................................................ 7 3.1 Studied forms: ........................................................................................................................................................................... 7

3.1.1 Hollow Cylinder .......................................................................................................................................................................... 7 3.1.2 Box .................................................................................................................................................................................................... 8

3.2 Mesh............................................................................................................................................................................................... 9 3.3 Initial conditions.................................................................................................................................................................... 10

3.3.1 Mach 9 .......................................................................................................................................................................................... 10 3.3.2 Mach 15 ....................................................................................................................................................................................... 11 3.3.3 Mach 20 ....................................................................................................................................................................................... 11 3.3.4 Rarefied flow ............................................................................................................................................................................. 11

3.4 Test case description ........................................................................................................................................................... 12 3.4.1 Mandatory cases ..................................................................................................................................................................... 12 3.4.2 Extra cases ................................................................................................................................................................................. 13

3.5 Output data: ............................................................................................................................................................................. 13 3.5.1 Models description ................................................................................................................................................................. 13 3.5.2 Aero-coefficient data ............................................................................................................................................................. 14 3.5.3 Surface data .............................................................................................................................................................................. 14

3.5.3.1 CFD data ............................................................................................................................................................................................. 14 3.5.4 Symmetry data ......................................................................................................................................................................... 14 3.5.5 Volume data ............................................................................................................................................................................... 14

4 Thermodynamic models validation .......................................................................................... 16 4.1 1D test case .............................................................................................................................................................................. 16 4.2 2D test case .............................................................................................................................................................................. 16

5 Integration simulation ............................................................................................................. 18 5.1 Initial conditions.................................................................................................................................................................... 18 5.2 Geometries for test cases ................................................................................................................................................... 19

5.2.1 Case 1: .......................................................................................................................................................................................... 19 5.2.2 Case 2: .......................................................................................................................................................................................... 19 5.2.3 Case 3: .......................................................................................................................................................................................... 19 5.2.4 Case 4: .......................................................................................................................................................................................... 19

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5.2.5 Case 5: .......................................................................................................................................................................................... 20 5.2.6 Case 6 ............................................................................................................................................................................................ 20 5.2.7 Case 7: .......................................................................................................................................................................................... 20 5.2.8 Case 8: .......................................................................................................................................................................................... 20

5.3 Demised test cases ................................................................................................................................................................ 21 5.3.1 Initial condition ....................................................................................................................................................................... 21 5.3.2 Geometry ..................................................................................................................................................................................... 21

5.3.2.1 Case 9: .................................................................................................................................................................................................. 22

5.3.2.2 Case 10: ............................................................................................................................................................................................... 22

5.3.2.3 Case 11: ............................................................................................................................................................................................... 22

5.3.2.4 Case 12: ............................................................................................................................................................................................... 22 5.4 Output data .............................................................................................................................................................................. 23

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Documents

Reference documents

Reference Document Title

Modifications Version Date Topic

V1.0 10/04/2014 First version of the document

V.1.1 05/05/2014 References to website

V.1.2 19/05/2014 References to website

V.1.3 29/09/2014 Add Sref for Aerodynamic cases and initial Temperature for

Thermodynamic cases

V.1.4 06/10/2014 Extra precisions concerning definition of aero-coefficient data

(3.5.2)

V.1.5 12/10/2014 Minor corrections

V.1.6 20/10/2014

Add properties for reference materials

Change ouput list for Integration test cases

V.1.7 06/02/2015

New Integration test cases

Add output for finalstate.txt, of Integration test cases + description

V.1.8 18/02/2015 Correction initial Flight Path Angle Integration cases and

thickness case 12

V.1.9 23/02/2015 Correction of Perigee Argument for Integration cases 9 to 12

Glossary Acronym Meaning

LLAVIF Longitude Latitude Altitude Velocity Inclination Flight path angle

CoG Center of Gravity

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Introduction

During the last decade, several tools have been developed in order to study the demise of spacecraft and satellite debris during atmospheric reentry, with the final goal to assess the ground risk. Decisions on whether to allow launching a spacecraft are taken based on the results of these tools. It is therefore of extreme importance to be able to assess the quality and uncertainties of such tools. Being too conservative in the risk assessment puts an economic burden on the aerospace industry. Predicting a too low risk will increase the real risk to the population.

Each tool includes different models (atmospheric, thermodynamic, aero-thermodynamic…) of which the uncertainties are of unknown. Until now there is no workshop that allows evaluating the precision and validity of results of these tools, unlike what is done for CFD simulations for example (Drag Prediction Workshop, High Lift Prediction Workshop, SPICES...).

The objective of the workshop is twofold. The first objective is to improve the overall quality of the tools by inter-comparison of the various data sources (numerical, analytic, experimental).

The second goal is to assess the uncertainties in the modeling of the various disciplines, so that they can be taken into account in a statistical analysis. In the existing methodologies the predictions are purely deterministic, which, taken into the account the uncertainties in all disciplines, is questionable. This workshop initiative is part

of the thesis work ‘Parallel Computing Platform Design for Demise’ in which a statistical approach is

proposed (using state of the art processors such as GPU and Xeon Phi), for which the uncertainties of the various models and input data are needed as input parameters.

Although not excluded, no typical workshop meeting is foreseen. Initially the workshop will be purely a web-based activity. The web site that will be put in place will allow registered users to access the test case data and share other information such as publications, description of the various codes, share spacecraft material properties etc.

The objective of this document is to describe a list of test cases that could be used to compare these different tools between them, and eventually with CFD tools.

Indeed, it is very important to notice that there are a lot of different disciplines included in the simulation of a debris reentry. For each of them, models are used to simplify simulations and reduce computation times. Thus the first goal should be to try to validate each discipline independently. This is the reason why these test cases are divided in three categories:

- Models validation cases: this part is directed towards the validation of the models themselves. This includes for example the validation of aerodynamic formulae used in rarefied and continuum regimes by comparing them to CFD simulations for example or Wind Tunnel tests when available.

- Thermal cases: this will be the same objective as for aerodynamic models, i.e comparing thermal formula used in debris simulation tools and more advanced numerical simulations or eventually wind tunnel tests if available.

- Integration simulation cases: this part will focus on complete trajectory comparisons between the different codes and eventually with some reconstructed data from past debris reentries. The main objective of this part is to show how the differences pointed in the two previous parts, impact the simulation of a debris re-entry.

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1 Directory structure

All the results will be stored on a web site provided by R.Tech at the following address: http://scdw.rtech.fr

The sub-directory structure will be as follow:

<Category>/Contributions/<Case n°>/<Contribution_number>/<Input_data>

/<Ouput_data>

/Grids

/Grids/<Case n°>/CGNS

/GridPro

Each participant has the possibility to use more than one simulation tool.

2 Overview of data format In order to facilitate data comparison, the data format must comply with the following requirements:

- All files must be ASCII

- All units must be SI units

- Floating point data must contain the dot (“.”) for the decimal delimiter

- <Input_data> must contain at least:

o One file description.txt containing the different input parameters used for the simulation

and thermal mode used (template in Annex 1).

- <Ouput_data> must contain at least:

o Please refer to each categories to have a description of the minimal requirements for output data

o If for any reason one of the output asked for is not available in a tool, provider is asked to fulfill the column corresponding to the parameter with -9999

http://scdw.rtech.fr/

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3 Aerodynamic models validation

3.1 Studied forms: In order to cover simple and more complex aerodynamic effects such as shock-shock interaction for example, it has been decided to use two shapes for the comparisons.

3.1.1 Hollow Cylinder The first shape is a hollow cylinder. It is defined by three dimensions:

- L1: Length of the cylinder - L2: External diameter of the cylinder - L3: Thickness of the cylinder

These elements are presented on the schema bellow:

Figure 1: Definition of the studied cylinder

X-axis is aligned with the axis of revolution of the cylinder. Z-axis is directed upward. Y-axis completes the direct referential. These three parameters will take the values as follow:

- L1: 0.1, 0.5 or 1.0m - L2: 1.0m - L3: 0.1,0.25 or 0.5m

X Y

Z

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For the computation of aerodynamic coefficients, Lref shall be chosen equal to √𝐿1 ∗ 𝐿2, Sref shall be equal to 1, and CoG shall be equal to (0,0,0) which is the center of the cylinder. The reference frame will be as presented on Figure 1, with the x axis along L1.

Figure 2:Inclination angles and momentum around axis Thus we can define the effective alpha (𝛼′) for the side slip cylinder as:

cos(𝛼′) = 𝑉𝑥𝑧 ∗cos(𝛼)

|𝑈|

And the different components of the speed as: 𝑣 = 𝑈 ∗ sin(𝛽)

𝑉𝑥𝑧 = √𝑈² − 𝑣² 𝑈𝑥 = 𝑉𝑥𝑧 ∗ cos(𝛼) 𝑈𝑦 = 𝑣

𝑈𝑧 = 𝑉𝑥𝑧 ∗ sin(𝛼)

3.1.2 Box The second shape is a cube and so it is defined by only one dimension L as can be seen on the figure bellow. For the computation of aerodynamic coefficients, Lref shall be chosen equal to L, Sref shall be equal to 1, and CoG shall be equal to (0,0,0) which is the center of the box. The reference frame will be as presented on Figure

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3. X-axis is aligned with the axis of revolution of the cylinder. Z-axis is directed upward. Y-axis completes the direct referential. The L parameter will be equal to 1.0m.

Figure 3: Definition of the studied cube.

3.2 Mesh

R.Tech will provide three different kinds of meshes to participants:

- Surface meshes in STL and IGES format: this can be used directly as input for some debris simulation tools or eventually be used as an input to create volume meshes.

- External 3D meshes for CFD simulations, in CGNS format

- Internal 3D meshes for thermal analysis in CGNS format

These meshes will only represent half of the object along the symmetry plane Oxz.

These meshes will be available on the workshop website in the following directory:

Aerodynamic/Meshes/R.Tech/

Each contributor is free to use its own meshes, but it will be asked to him to provide his meshes to the other contributors. Meshes names will have the following structure: Contributor_name_Shape_XXX.format, with XXX a single incremental number

X

Y

Z

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These meshes will be available on the workshop website in the following directory:

Aerodynamic/Meshes/Contributors/

3.3 Initial conditions

Simulations will be realized assuming perfect gas hypothesis for computations at Mach9, and assuming chemical non-equilibrium (thermal equilibrium) for computations at Mach 15 and 20.

These computations have to be performed in a laminar regime.

Chemical kinetic coefficients are those tabulated by Dunn-Kang, and listed below:

cf nf Θf N2+N2 = N+N+N2 4.70E+011 -0.5 113000

N2+O2 = N+N+NO 1.90E+011 -0.5 113000

N2+NO = N+N+NO 1.90E+011 -0.5 113000

N2+N = N+N+N 4.09E+016 -1.5 113000

N2+O = N+N+O 1.90E+011 -0.5 113000

O2+N2 = O+O+N2 7.20E+012 -1 59500

O2+O2 = O+O+O2 3.24E+013 -1 59500

O2+NO = O+O+NO 3.60E+012 -1 59500

O2+N = O+O+N 3.60E+012 -1 59500

O2+O = O+O+O 9.00E+013 -1 59500

NO+N2 = N+O+N2 3.90E+014 -1.5 75500

NO+O2 = N+O+O2 3.90E+014 -1.5 75500

NO+NO = N+O+NO 7.80E+015 -1.5 75500

NO+N = N+N+O 7.80E+015 -1.5 75500

NO+O = N+O+O 7.80E+015 -1.5 75500

N2+O = NO+N 7.00E+007 0 38000

NO+O = O2+N 3.20E+003 1 19700

Figure 4: Reaction’s constants, Dunn-Kang [m

3.mol

-1.s

-1]

3.3.1 Mach 9 Here are listed the initial conditions that shall be used for simulations at Mach 9

Mach 9 [-]

Speed 2.89E+003 [m/s]

Temperature 256.26 [K]

Pressure 272.72 [Pa]

Density 3.71E-003 [kg/m3]

Re/m 6.56E+005 [m-1

]

Wall Temperature 700 [K]

Chemistry Perfect gas N.A.

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Mach 15 [-] Speed 4769.7300 [m/s] Temperature 250.61 [K] Pressure 26.3 [Pa] Density 3.64E-4 [kg/m

3]

Re/m 98573.316 [m-1

] Mass fraction N2 0.767 [-] Mass fraction O2 0.233 [-] Wall Temperature 700 [K] Turbulence model None (laminar) [-] Parietal model catalycity Pseudo catalytic [-]

Chemistry Non Équilibrium N.A.


Mach 20 [-] Speed 5959.41091933 [m/s] Temperature 220.10227234 [K] Pressure 6.01998111 [Pa] Density 9.49055199e-05 [kg/m

3]

Re/m 34557.813 [m-1

]

Mass fraction N2 0.767 [-] Mass fraction O2 0.233 [-] Wall Temperature 700 [K] Turbulence model None (laminar) [-] Parietal model catalycity Pseudo catalytic [-] Chemistry Non Équilibrium N.A.

3.3.4 Rarefied flow Here are listed the initial conditions that shall be used for simulations in rarefied regime.

Mach 24.64 [-] Speed 7364 [m/s] Temperature 222 [K] Pressure 0.00749787 [Pa]

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Density 1.18e-07 [kg/m

3]

Mass fraction N2 1 [-] Mass fraction O2 0.0 [-] Wall Temperature 200 [K]

3.4 Test case description

The tables below summarize the different test case configurations, including the shape, the dimensions of the shape, the Mach number and the free stream angle of attack.

As explained at the beginning of the document, these test cases can be run either using a CFD software or a simplified tool or formula that is also used in a debris simulation software from which one would like to evaluate the precision.

Axisymmetric computation is allowed for the case of the cylinder with an angle of attack of 0°.

For the other cases, symmetric computations are allowed (Oxz being the plane of symmetry).

There are 6 mandatory cases and 15 optional cases.

3.4.1 Mandatory cases

The objective of the mandatory cases is to study the aerodynamic of an hollow cylinder and a box. The hollow cylinder is an interesting case with respect to the shock-shock interactions appearing between the bottom part and the top part of the cylinder at 45°. The box case is more classical but small shock distance at 45° makes it an interesting case as well.

In the previous studies, the influence of Mach number was discovered to be less important than other parameters and thus it has been decided to study only Mach 9 for compulsory cases.

Case N° Shape L1 (m) L2 (m) L3 (m) Mach Angle of Attack (°)

Sideslip (°)

M001 Cylinder 1.0 1.0 0.25 9 0 0

M002 Cylinder 1.0 1.0 0.25 9 45 0

M003 Cylinder 1.0 1.0 0.25 9 90 0

M004 Box 1.0 1.0 1.0 9 0 0

M005 Box 1.0 1.0 1.0 9 45 0

M006 Box 1.0 1.0 1.0 9 45 45

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3.4.2 Extra cases In these extra cases (not mandatory), the different objectives are:

- (1) study various thickness for the cylinder at 45° (extend case M002)

- (2) study the influence of Mach number for the cylinder of thickness 0.25m (extend cases M001, M002 and M003)

- (3) study the influence of Mach number for the box (extend case M005)

Case N° Objective Shape L1 (m) L2 (m) L3 (m) Mach Angle of Attack (°)

Sideslip (°)

X001 (1) Cylinder 1.0 1.0 0.1 9 45 0

X002 (1) Cylinder 1.0 1.0 0.5 9 45 0

X003 (2) Cylinder 1.0 1.0 0.25 20 0 0

X004 (2) Cylinder 1.0 1.0 0.25 20 45 0

X005 (2) Cylinder 1.0 1.0 0.25 20 90 0

X006 (3) Box 1.0 1.0 1.0 20 45 0

Extra cases may be run with DSMC code for the rarefied flow condition described previously.

Case N° Shape L1 (m) L2 (m) L3 (m) Flow Angle of Attack (°)

Sideslip (°)

X007 Cylinder 1.0 1.0 0.1 DSMC 0 0

X008 Cylinder 1.0 1.0 0.5 DSMC 0 0

X009 Cylinder 1.0 1.0 0.25 DSMC 0 0

X010 Cylinder 1.0 1.0 0.1 DSMC 45 0

X011 Cylinder 1.0 1.0 0.5 DSMC 45 0

X012 Cylinder 1.0 1.0 0.25 DSMC 45 0

X013 Cylinder 1.0 1.0 0.1 DSMC 90 0

X014 Cylinder 1.0 1.0 0.5 DSMC 90 0

X015 Cylinder 1.0 1.0 0.25 DSMC 90 0

3.5 Output data:

3.5.1 Models description In order to improve the understanding of results, participants are invited to provide at least a brief description of

the models they used for their computations in the file modeldescription.txt.

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3.5.2 Aero-coefficient data

The aerodynamic coefficients will be stored in the file aerocoeff.txt.

Aerodynamic coefficients have to be computed in the reference frame specified paragraph 3.1.

The first line of the TECPLOT version 8, compatible file aerocoeff.txt is:

Variables = x Cx Cy Cz Cn Cl Cm CD CL “L/D” In which Cx, Cy and Cz are the axial forces, Cn, Cl and Cm are the moments around x,y and z axis, CD and CL the drag and lift forces, and L/D is the ratio of the lift over the drag, x will not be used in this section.

3.5.3 Surface data

3.5.3.1 CFD data

The CFD data at the surface will be stored in the file CfdData.txt

The following surface quantities ('variables') at the mesh nodes listed. The first line of the TECPLOT version 8 compatible file is: Variables = x y z T Cp Cf' Cfx Cfy Cfz Q Q_t_r Q_v Q_d “y+” “è” cN2 cO2 cNO cN cO In which cN2 etc denote the mass-fractions and è the emissivity. Make sure that the exact naming of the variables (upper/lower case) is respected. Values that are not applicable can be removed. Other values can be added if needed. The order of the variables is encouraged to be followed but not strictly necessary. The coordinates x,y,z are given in the reference frame specified paragraph 3.1.

3.5.4 Symmetry data

The following surface quantities ('variables') at the mesh nodes will be listed in the files: symmetry_y.plt

and symmetry_z.plt.

The first line of the TECPLOT version 8 compatible file is: Variables = x y z cN2 cO2 cNO cN cO u v w Tv_N_2 Tv_O_2 Tv_N_O T rho p M H In which cN2 etc denote the mass fractions, ‘H’ the enthalpy and “è” the emissivity. Make sure that the exact naming of the variables (upper/lower case) is respected. Values that are not applicable can be removed. Other values can be added if needed. The order of the variables is encouraged to be followed but not strictly necessary. The coordinates x,y,z are given in the reference frame specified paragraph 3.1

3.5.5 Volume data

The following surface quantities ('variables') at the mesh nodes will be listed in the file volume.plt.

The first line of the TECPLOT version 8 compatible file is: Variables = x y z cN2 cO2 cNO cN cO u v w Tv_N_2 Tv_O_2 Tv_N_O T rho p M H

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In which cN2, …, cO denote the mass-fractions, ‘H’ the enthalpy and “`e” the emissivity. Make sure that the exact naming of the variables (upper/lower case) is respected. . Values that are not applicable can be removed. Other values can be added if needed .The order of the variables is encouraged to be followed but not strictly necessary. The coordinates x,y,z are given in the reference frame specified paragraph 3.1.

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4 Thermodynamic models validation

The objective of this part is to validate thermodynamic and ablation models used in the different debris simulation tools. Two test cases have been identified:

- a solid sphere with 1D or 3D ablation - a solid sphere with 2D ablation -

4.1 1D test case

The sphere will have the following dimensions:

- Radius: 0.5m

The sphere is composed of AA7075 with the following properties:

- Thermal conductivity: 130 W/m-K

- Specific heat capacity: 1012.35 J/kg/K

- Density: 2 787 kg/m3

- Emissivity: 0.1

Extra properties are provided in Annex 2.

The initial temperature is imposed to 200 K.

A fixed integrated heat flux of 400kW will be imposed on the sphere.

Thus the net entering flux is equal to 400𝑘𝑊

4∗𝜋∗0.5²~127.324kW/m².

Contributors are free to treat the case as 1D or 3D, they will just have to indicate it in the description.txt

file.

Output data must contain at least the wall temperature, the temperature (or temperatures) inside the sphere as well as the thickness of the sphere through the simulation.

4.2 2D test case

The sphere will have the following dimensions:

- Radius: 0.5m

The sphere is composed of aluminum with the following properties:

- Thermal conductivity : 130 W/m-K

- Specific heat capacity: 1012.35 J/kg/K

- Density: 2 787 kg/m3

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- Emissivity: 0.1

Extra properties are provided in Annex 2.

The initial temperature is imposed to 200 K.

A fixed integrated heat flux of 400kW will be imposed on the sphere.

The net flux is expressed as, 𝐹 = 𝐹𝑆𝑡𝑎𝑔 ∗ 𝑐𝑜𝑠𝜃 ∗ 𝑐𝑜𝑠𝜑

Fstag being the flux at the stagnation point in the direction of the x axis, θ the angle in the xOz plane and φ the angle in the xOy plane as defined on the Figure 5. The angles are defined positive in the forward direction.

Thus the flux at the stagnation point is equal to: 𝐹𝑠𝑡𝑎𝑔 =400𝑘𝑊

𝜋∗0.52~509.296𝑘𝑊/𝑚²

Output data must contain at least the wall temperature of the side facing free stream, the temperature (or temperatures) of the interior nodes of the sphere as well as the sphere thickness throughout the simulation.

In order to improve the understanding of results, participants are invited to provide at least a brief description of

the models they used for their computations in the modeldescription.txt output file.

Figure 5: 2D distribution of the flux

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5 Integration simulation Contrary to the previous test cases, this chapter describes the comparison tests that shall be run on a complete debris reentry.

The goal is to globally compare the different simulation tools by using macroscopic parameter such as the impact energy, the impact location, etc...

5.1 Initial conditions

Every test case will start with the same initial condition. The initial entry point in two different coordinate systems is:

- LLAVIF system :

Initial Altitude : 120.0 km

Initial Speed in the inertial frame : 7.6 km/s

Flight path angle: -2.612°

Initial Temperature : 300 K

Initial Latitude : 0°

Initial Longitude : 0°

Inclination angle: 45°

- Keplerian coordinate system:

Semi major axis : 6139.7329559249 km

Eccentricity : 0.0728268039

Apogee altitude : 208.7336239044 km

Perigee altitude : -685.5406320546 km

Perigee argument : 145.7054889438°


Azimuth angle: 45°

Right ascension of ascending node: 99.9064731143°

True anomaly: -145.7054889438°

The date is: 2012-01-01, 00h00 UTC.

The atmospheric model used for the simulation will be the US Standard Atmosphere 1976. If the US Standard Atmosphere 1976 model is not available, please use the MSIS86 model. The atmospheric model used should be

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indicated in the input data to make it clear for comparisons.

5.2 Geometries for test cases

Materials properties used for the simulations are those defined in the table Annex 2. If these properties can’t be

defined in the software, participant will have to indicate in the file description.txt the materials properties

used and their properties.

Objects are those define in the Annex 3. All the objects considered here are randomly tumbling.

5.2.1 Case 1: Object: Sphere

Outer radius: 0.5 m

Inner radius: 0.47 m

Material: AA7075

Mass: 247.224 kg

5.2.2 Case 2: Object: Sphere

Outer radius: 0.5 m


Material: Ti-6AL-4V

Mass: 393.589 kg

5.2.3 Case 3: Object: Cylinder

Outer radius: 0.5 m


Length: 1.0 m

Material: AA7075

Mass: 370.835 kg

5.2.4 Case 4: Object: Cylinder

Outer radius: 0.5 m


Length: 1.0 m

Material: Ti-6Al-4V

Mass: 590.383 kg

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5.2.5 Case 5: Object: Box

Length: 1.0 m

Width: 1.0 m

Height: 1.0 m

Thickness: 0.03 m

Material: AA7075

Mass: 472.162 kg

5.2.6 Case 6 Object: Box

Length: 1.0 m

Width: 1.0 m

Height: 1.0 m

Thickness: 0.03 m

Material: Ti-6Al-4V

Mass: 751.699 kg

5.2.7 Case 7: Object: Plate

Length: 1.0 m

Width: 1.0 m

Thickness: 0.03 m

Material: AA7075

Mass: 83.61 kg

5.2.8 Case 8: Object: Plate

Length: 1.0 m

Width: 1.0 m

Thickness: 0.03 m

Material: Ti-6Al-4V

Mass: 133.11 kg

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5.3 Demised test cases

We define four new test cases that are supposed to fully demise during the atmospheric reentry.

5.3.1 Initial condition These test cases have new initial conditions. The initial entry point in two different coordinate systems is:

- LLAVIF system :

Initial Altitude : 100.0 km

Initial Speed in the inertial frame : 7.6 km/s

Flight path angle: -0.5°

Initial Temperature : 300 K

Initial Latitude : 0°

Initial Longitude : 0°


- Keplerian coordinate system:

Semi major axis : 6104.1211743857 km

Eccentricity : 0.0618885792

Apogee altitude : 103.7601011331 km

Perigee altitude : -651.7906723617 km

Perigee argument : 172.3940541048°


Azimuth angle: 45°

Right ascension of ascending node: 99.9064709751°

True anomaly: -172.3940540568°

The date is: 2012-01-01, 00h00 UTC.

As for the other test cases the atmospheric model used for the simulation will be the US Standard Atmosphere 1976. If the US Standard Atmosphere 1976 model is not available, please use the MSIS86 model. The atmospheric model used should be indicated in the input data to make it clear for comparisons.

5.3.2 Geometry Materials properties used for the simulations are those defined in the table Annex 2. If these properties can’t be

defined in the software, participant will have to indicate in the file description.txt the materials properties

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used and their properties.

Objects are those define in the Annex 3. All the objects considered here are randomly tumbling.

5.3.2.1 Case 9:

Object: Sphere

Outer radius: 0.5 m


Material: AA7075

Mass: 34.743 kg

5.3.2.2 Case 10:

Object: Cylinder

Outer radius: 0.5 m


Length: 1.0 m

Material: AA7075

Mass: 52.115 kg

5.3.2.3 Case 11:

Object: Box

Length: 0.3 m

Width: 0.3 m

Height: 0.3 m

Thickness: 0.013 m

Material: AA7075

Mass: 17.918 kg

5.3.2.4 Case 12:

Object: Plate

Length: 0.5 m

Width: 0.5 m

Thickness: 0.015 m

Material: AA7075

Mass: 10.451 kg

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5.4 Output data

The output data must contain at least:

One file, finalstate.txt, containing the final state of the object, and respecting the following

format:

Duration=” “ #Duration of the fall of the object (or the duration to

demise the last debris)

Debris_amount=” “ #Amount of debris for software including fragmentation

(equal to 1 for the others)

Remaining_Mass=” “ #Total remaining mass

Remaining_Mass_Debris_X=” “ #For software including fragmentation,

remaining mass of the debris n°X

Altitude_X=” “ #Landing/demise altitude of debris n°X. If no fragmentation

X=0

Longitude_X=” “ #Landing/demise longitude of debris n°X. If no

fragmentation X=0

Latitude_X=” “ #Landing/demise latitude of debris n°X. If no

fragmentation X=0

Casualty_Area=” “ # as describe in Annex 3 (if participant uses another

method to compute the casualty area, he will have to provide description of

the method he used in the modeldescription.txt file)

One file, TECPLOT format, timeevolution.dat containing at least time evolution of :

Time [s], Altitude [m], Longitude [°], Latitude [°], Velocity (in Earth rotating reference frame) [m/s], Velocity (in inertial frame) [m/s], Acceleration (in inertial frame) [m/s²], Mach, Knudsen, Thermal mass [kg], Aerodynamic mass [kg], Wall temperature [K], Cd, Drag force [N], Reference area of the object [m²], Atmospheric temperature [K], Atmospheric density [kg/m

3], Atmospheric pressure [Pa], Down range [m],

Down range shortest path [m], Flight path angle [°], Net heat flux (integral over the surface) [W], Convective heat flux [W], Radiation gain heat flux [W], Radiation loss heat flux [W], Oxidation heat flux [W], Wall thickness [mm], Outer Area of the object [m²], Kinetic energy [J], Mass of the object [kg], Ballistic coefficient [m²/kg], Thermal area [m²]

The first line of the TECPLOT version 8 compatible file is: Variables = Time Altitude Longitude Latitude Velocity VelocityInertial Acceleration Mach Knudsen ThermalMass AerodynamicMass WallTemperature Cd DragForce ReferenceArea ExtTemperature ExtDensity ExtPressure DownRange DownRangeShortestPath FPA Qnet Qconv QradGain QradLoss Qoxidation Thickness OuterArea KineticEnergy TotalMass BallisticCoefficient ThermalSurface

A detailed description of these parameters is provident in Annex 4.

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For Spacecraft oriented code: One file, TECPLOT format, sco_timeevolution.dat containing

temperature [K], heat flux density [W/m2] and pressure [Pa] distribution over the surface as function of time.

The first line of the TECPLOT version 8 compatible file is: Variables = HeatFluxDensity Temperature Pressure Then for each time step contributor is asked to define a new zone as advised in the Tecplot data format guide: Tecplot Data Format Guide

ftp://[email protected]/tp_data_format_guide.pdf

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Annex 1: description.txt template

The description.txt file is structured as describe bellow. Obviously contributors are free to add extras information, but at least these are mandatory:

Category=” “ #Aerodynamic, Thermal or Integration

Code=” “ #Name of the code/software, version

Contributor=” “

Meshes=” “ #If none required indicate NA

Dimension=” “ #1D or 3D, only for thermodynamic 1D case, the other indicate NA

Materials_properties=” “ #<density (kg/m3)>, <heat of fusion (J/kg)>, <melting T

(K)>, <oxidation heat (J/kg(02))>, only if used values are different from booklet

Atmospheric_model=” “ #US76 or MSIS86, only for integration cases, the other

indicate NA

Fragmentation=” “ #TRUE or FALSE, only for integration cases, the other indicate

NA

Annex 2: Materials properties

Name Density [kg/m

3]

Heat of fusion [J/kg]

Melting T [K] Oxidation heat

[J/kg (02)] Emissivity

Heat Capacity [J/kg/K]

AA7075 2 787.0 376 788.0 830.0 0.0 0.141 1012.35

TI-6Al-4V 4 437.0 393 559.0 1 943.0 3.248125e7

0.302 807.5

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Annex 3: Objects and casualty area definition

1) The Randomly tumbling sphere:

Casualty area AC:

𝐴𝐶 = 𝜋 ∗ (𝑅𝑜𝑢𝑡 +𝐷ℎ2)2

With Rout the outer radius of the sphere and Dh the mean human diameter.

2) The randomly tumbling cylinder

Note that the thickness is the same along the cylinder as for the faces.

Casualty area AC:

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𝐴𝐶 = 𝜋 ∗ (𝑅𝑒𝑞 +𝐷ℎ2)2

With:

𝑅𝑒𝑞 = √𝑆𝑚𝑎𝑥

𝜋 and 𝑆𝑚𝑎𝑥 = max(𝜋 ∗ 𝑅𝑜𝑢𝑡

2 , 𝐿𝑜𝑢𝑡 ∗ 2 ∗ 𝑅𝑜𝑢𝑡); Lout being the Length of the cylinder and Rout

the Outer radius

3) The randomly tumbling box:

Casualty area AC:

𝐴𝐶 = 𝜋 ∗ (√𝐿 ∗𝑊

𝜋 +

𝐷ℎ2)2

With L the Length of the box and W the Width.

4) The randomly tumbling plate:

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Casualty area AC:

𝐴𝐶 = 𝜋 ∗ (√𝐿 ∗𝑊

𝜋 +

𝐷ℎ2)2

With L the Length of the plate and W the Width.

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Annex 4: Detailed description of output parameters of integration simulation

Time: elapsed time since the beginning of the reentry

Altitude: Distance between the object and the ground

Longitude: The Longitude

Latitude: The Latitude

Velocity: Velocity of the object in the rotating frame

VelocityInertia : Velocity in the inertial frame

Acceleration: Acceleration of the object in the inertial frame

Mach: The Mach number

Knudsen: The Knudsen number

ThermalMass: Mass used for the thermic computations

AerodynamicMass: Mass used for aerodynamic computations

WallTemperature: Temperature of the wall of the object

Cd: Drag Coefficient

Drag Force: The current Drag Force

ReferenceArea: Aerodynamic Reference Surface

ExtTemperature: Atmospheric Temperature

ExtDensity: Atmospheric Density

ExtPressure: Atmospheric Pressure

DownRange: The down range

DownRangeShortestPath: The down range shortest path

FPA: Flight Path Angle

Qnet: Net flux integrated over the surface

Qconv: Convective Flux to the Wall (>0 if the flux heats the wall)

QradLoss: Radiative Flux emitted by the wall

Qoxidation: Oxydation Flux integrated over the surface

Thickness: Thickness of the wall

OuterArea: The true surface of the object

KineticEnergy: Kinetic Energy of the object

TotalMass: Total Mass of the object

BallisticCoefficient: Ballistic Coefficient of the object

ThermalSurface: Surface used for thermic computations