Chapter 66: Satellite in Orbit

66 Satellite in Orbit

Summary 1221

Introduction 1222

Modeling Details 1222

Solution Highlights 1225

Results 1231

Modeling Tips 1232

Input File(s) 1233

1221CHAPTER 66

Satellite in Orbit

SummaryTitle Chapter 66: Satellite in Orbit

Features: Enclosure Radiation, Orbital Heating and Radiation Exchange Factors, Multiple Orbits and Pointing, MLI and Coating, Satellite with moving parts (articulating solar panels)

Geometry & Boundary Conditions

Material propertiesALU606: K = 167 W/m/°C, Cp = 940 J/Kg/°C, ρ = 2700 Kg/m³Honeycomb: K = 11.5 W/m/°C, Cp = 945 J/Kg/°C, ρ = 50 Kg/m³, Several coatings

Analysis characteristics Solution 400 / RC Network solver. Steady and transient thermal analysis.

Applied Loads Enclosure Radiation Face, Radiation Enclosure

Element type CQUAD4, CTRIA3

FE results

Space ambient temperature = -273.15 °C (default value)

MD Demonstration Problems

CHAPTER 661222

IntroductionThis problem demonstrates the orbital space application of SOL 400 RC Network Solver and Thermica v3.

Modeling Details

Figure 66-1 Satellite Geometry and Materials

1 m

2 m1 m1 m

0.5 m

2.5 m2 m

Y

Systemreference frameorigin

1.25 m

2 m

1 m

gaps : 0.1 m

Parabola :diam=1.5 mheight = 0.25 m

1.75 m

Cylinders :diam = 0.02 m 1 m

Y

PANELSMaterial : HONEYCOMBSun face : SOLARCELLAnti -Sun face : BLACKPAINT

BODY FACESMaterial : ALU6061Inner coating : BLACKPAINTOuter coating : MLI

ANTENNAMaterial : HONEYCOMBEmitting face : WHITEPAINTRear side : MLI

YOKEMaterial : ALU6061Coating : MLI

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Satellite in Orbit

Case 1: Single Round Orbit, Single Pointing, and Solar Panels Articulation

Figure 66-2 Satellite Orbit and Pointing for Case1

Orbital Description: Reference line: Sun Altitude: 1000 km Inclination: 60° Solar time of ascending node: 16:00 Epoch: Spring 2000

Pointing Description: -Z toward Earth +X along velocity vector Moving Parts: Solar panels pointing to the Sun 1 axis of rotation

MD Demonstration Problems

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Case 2: Multiple Orbital Arcs with Multiple Pointing, Solar Panels Articulation

Figure 66-3 Satellite Orbit and Pointing for Case1

Orbital Arc #1: Sun Pointing Orbital Description: Reference line: Sun Altitude: 1000 km Inclination: 60 deg Solar time of ascending node: 16h Epoch: Spring 2000 Duration: 170 deg

Orbital Arc #2: Sun to Earth Orbital Description: Reference line: Sun Altitude: 1000 km Inclination: 60 deg Solar time of ascending node: 16h True anomaly: 170 deg True anomaly step: 1 deg Duration: 10 deg

Orbital Arc #3: Earth Pointing Orbital Description: Reference line: Sun Apogee: 3000 km Perigee: 1000 km Inclination: 60 deg Solar time of ascending node: 16h Argument of perigee: 180 deg True anomaly: 0 deg Duration: 180 deg

Pointing Description: -Z toward Sun +Y toward North Pole Moving Parts: Solar panels pointing to the Sun

Pointing Description: -Z toward Sun +Y toward North Pole dYaw/dt = 0.25 deg/s dPitch/dt = 0.30 deg/s dRoll/dt = 0.26 deg/s Moving Parts: Solar panels pointing to the Sun 1 axis of rotation

Pointing Description: -Z toward Earth +X along Velocity vector Moving Parts: Solar panels pointing to the Sun 1 axis of rotation

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Solution HighlightsRC Network Solver uses VIEWEX entry to simulate the enclosure radiation loads. RADC entry is used to represent the MLI or Coating materials.

RADSET 6RADCAV 6 448 YES 0 FD SPOINT 696TEMP 37 696 -273.15SPC 6 696 1 -273.15RADM 7 1.PHBDY 5 1.CHBDYP 448 5 POINT 696 7 1. 0.0 0.0VIEWEX 6 F AREA T T THERMIC 1380. 0.3 -19. F F 5000 5000 99. 3600. 1.E-8

A black, unit area point element CHBDYP is used to define the radiation ambient temperature for a radiation enclosure. This point element is referenced by RADCAV entry to link to the enclosure. The point is defined as a SPOINT and SPC is used to define its temperature value. VIEWEX entry links with a radiation enclosure by the ICAVITY ID, and define the external radiation solvers and some related control parameters. The orbital and pointing parameters are not defined inside the bdf file. They are defined in the GUI of the external radiation solvers (such as Thermica v3). The following shows the RADC cards which are used to define the coating and MLI materials for radiation loads.

RADC 6 0.82 0.74 + + COAT Solar_ceRADC 5 0.78 0.52 + + MLI 0.02

MD Demonstration Problems

CHAPTER 661226

Defines the radiation solver and correlating solver parameters for radiation calculations in RC heat transfer.

Format NEVADA

Format TSS

Format THERMICA

Format TRASYS

Format SRR

VIEWEX Advanced RC Radiation Solver Parameters

Note: You must have a copy of the external radiation code to use it.

1 2 3 4 5 6 7 8 9 10VIEWEX ICAVITY Run

InteractivelyRADK Disto Method

Orbital Re-use existing results

+

“NEVADA” RENO Reflection Restart RENO Ray count

VEGAS Ray count

Energy Cutoff

Confidence GRID closure

+

+ GRID iterations Time Scale RADK cutoff

1 2 3 4 5 6 7 8 9 10VIEWEX ICAVITY Run

InteractivelyRADK Disto Method

Orbital Re-use existing results

+

+ “TSS” +

1 2 3 4 5 6 7 8 9 10VIEWEX ICAVITY Run

InteractivelyRADK Disto

MethodOrbital Re-use

existing results

+

+ “THERMIC” Solar FLux Planet Albedo

Planet BlackBody

Restart Suppress VF Articulation

Radiation ray count

Orbital flux ray count

+

+ Confidence Time Scale RADK cutoff

1 2 3 4 5 6 7 8 9 10VIEWEX ICAVITY Run

InteractivelyRADK Disto

MethodOrbital Re-use

existing results

+

+ “TRASYS” Axi Radial mesh Axi Axial mesh

Axi Angular mesh

Time scale

RADK cutoff +

1 2 3 4 5 6 7 8 9 10VIEWEX ICAVITY Run

InteractivelyRADK Disto

MethodOrbital Re-use

existing results

+

+ “SRR” Gebhart Solver Convergence Tol

Max Iter Fij smoothing method

Fij Filter cutoff

Fij Smoothing

Tol

Fij Smooth Iter

+

+ Bij smoothing method Bij Filter cutoff Bij Smoothing Tol

Bij Max Iter

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Satellite in Orbit

Format SRQ

1 2 3 4 5 6 7 8 9 10VIEWEX ICAVITY Run

InteractivelyRADK Disto

MethodOrbital Re-use

existing results

+

+ “SRQ” Flux Solver Convergence Tol

Max Iter Fij smoothing method

Fij Filter cutoff

Fij Smoothing

Tol

Fij Smooth Iter

+

Field Contents Type Default

ICAVITY Cavity identification number. I 0 Required

Run Interactively Run the radiation code interactively. C, “FULL”, “T”, or “F”

FULL

Do not currently have batch mode for Thermica or TSS.

Do not have interactive mode for TRASYS.

RADK Distro Method How to redistribute RADK onto elements. C, “FULL”, “AREA”, or “DIRECT”

FULL

Orbital Use orbital analysis for radiation. Not supported in SindaRad.

C, “T”, or “F”

“F”

Re-use existing results

Re-use previous radiation results. C, “T”, or “F”

“F”

“NEVADA” Identification that NEVADA will be used. C

RENO Reflection Use reflection method of ray tracing for RADK. C, “T”, or “F”

“F”

Restart Use Restart option. C, “T”, or “F”

“F”

Reno Ray count Number of rays cast for Reno module I > 0 5000

Vegas Ray count Number of rays cast for Vegas module I > 0 5000

Energy Cutoff Energy cutoff level. I -3

Confidence Confidence Level percentage R > 0.0 99.0

GRID closure GRID closure tolerance. R > 0.0 0.001

GRID iterations Maximum GRID iterations I > 0 300

Time Scale Orbital time scale factor, number of time units in an hour (e.g., If using seconds, value would be 3600.0.).

R > 0.0 1.0

RADK cutoff RADK filter smallest element. R > 0.0 1.0e-8

MD Demonstration Problems

CHAPTER 661228

“TSS” Identification that TSS will be used. C

“THERMICA” Identification that THERMICA will be used. C

Solar Flux Quantity of solar flux. R > 0.0 1380.0

W/m2

Planet Albedo Planetary Albedo. R -19, assumes Earth orbit

Planet BlackBody Planet Blackbody. R -10.0, assumes Earth orbit

Suppress VF Articulation

Suppress view factor articulation. C, “T”, or “F”

“F”

Radiation ray count Number of rays cast for radiation calculation. I > 0 5000

Orbital flux ray count Number or rays cast for radiation calculation. I > 0 5000

“TRASYS” Identification that TRASYS will be used. C

Axi Radial mesh Axisymmetric element mesh in radial direction. I > 0 1

Axi Axial mesh Axisymmetric element mesh in axial direction. I > 0 1

AXI Angular mesh Axisymmetric element mesh in angular direction. I > 0 5

“SRR” Identification that the SindaRad. RADK method will be used

C

Gebhart Solver Which RADK solver to use. “GS” or “FGS”

“FGS”

Convergence Tol Tolerance for convergence of RADK calculation. R > 0.0 1.0e-5

Max Iter Maximum allowable iterations to converge. I > 0 50

Fij smoothing method How to filter view factors. C, “CROP” or “HIGH”

“CROP”

Fij Filter cutoff Parameter for filter. R > 0.0 1.0e-8

Fij Smoothing Tol Tolerance for smoothing. R 1.0e-4

Fij Smoothing Iter Maximum allowable iterations to smoothing. I > 0 50

Bij smoothing method How to filter conductors C, “CROP” or “HIGH”

“CROP”

Bij Filter cutoff Parameter for filter. R > 0.0 1.0e-8

Bij Smoothing Tol Tolerance for smoothing. R 1.0e-4

Field Contents Type Default

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Satellite in Orbit

Remarks

1. This entry is for RC Network solver only. EX means external radiation solvers.

2. Each entry type is designed for one specific radiation solver, except the very last two types, which are for SINDARad’s two options:

NEVADA

TSS

THERMICA

TRASYS

SINDARad RADK method

SINDARad Q method

3. About more details about the parameters in the entry, please reference SINDA for Patran User’s Guide and SINDARad User’s Guide.

Bij Max Iter Maximum allowable iterations to smoothing. I > 0 50

“SRQ” Identification that the SindaRad QRad method will be used.

C

Flux Solver Which QRad solver to use. C, “GS” or “CG”

“GS”

Convergence Tol Tolerance for convergence of QRad calculation. R > 0.0 1.0e-5

Field Contents Type Default

MD Demonstration Problems

CHAPTER 661230

Defines the radiative properties of advanced materials such as coatings and multilayer insulation, commonly used in the aerospace market.

Format COAT

Format MLI

Remarks

1. This entry is for RC Network solver only.

2. Estar is defined as the effective emissivity from the wall to MLI outer surface. The general value is around 0.01 to 0.03, the typical value is 0.02.

3. Emis is usually for the IR waveband, and Absorptivity is for the UV waveband.

RADC Thermal Radiative Coating Properties

1 2 3 4 5 6 7 8 9 10RADC RADMID Emis Absorptivity IR Spec UV Spec +

+ “COAT” IR Transpa

IR Transluc UV Transpa UV Transluc

IR Refrac Ind

UV Refrac Ind

1 2 3 4 5 6 7 8 9 10RADC RADMID Emis Absorptivity IR Spec UV Spec +

+ “MLI” Estar

Field Contents Type Default

RADMID Radiation material identification number. I 0 Required

“COAT” Identification that a coating type material has been started. C 0

Emis Emissivity. R 0.0 1.0

Absorptivity Absorptivity. R 0.0 1.0

IR Spec IR Specularity. 0.0 < R 1.0 0.0

UV Spec UV Specularity. 0.0 < R 1.0 0.0

IR Transpa IR Transparency. 0.0 < R 1.0 0.0

IR Transluc IR Translucency. 0.0 < R 1.0 0.0

UV Transpa UV Transparency. 0.0 < R 1.0 0.0

UV Transluc UV Translucency 0.0 < R 1.0 0.0

IR Refrac Ind IR Refraction Index. R 1.0 1.0

UV Refrac Ind UV Refraction Index. R 1.0 1.0

MLI Identification that an MLI type material has been started. C

Estar MLI E-star parameter. R 0.0

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Satellite in Orbit

Results

Figure 66-4 Temperature Contour of Satellite for Case 1 (Steady State)

Figure 66-5 Temperature Contour of Satellite for Case 2 (Steady State)

MD Demonstration Problems

CHAPTER 661232

Figure 66-6 Temperature vs. Time on Solar Panels (Transient)

The steady state results are used as the initial conditions. They are actually the average temperatures over the whole orbital period. The orbits in both cases have eclipses with the Earth shadow; therefore the steady state temperatures are lower than the temperatures in the Sun shine period. That is why the curves have a sudden jump up at the beginning. The lower temperature at the middle curves shows the eclipse effects on the solar panels. The green curves show the shading effect caused by the satellite body and antenna. In case 2, during the first orbital arc period, the satellite body and antenna point vertically to the Sun, along with the solar panels, so no shading effect at all, and the temperatures are certainly much higher. During the third orbital arc period, the satellite body and antenna point to the Earth, while the solar panels point to the Sun, the shading effect occurs at certain orbital locations. The temperatures are relatively lower because the satellite orbit is much higher. The top points (inflexion) of the curves shows the locations where the solar panels point to the Sun best, while the satellite body and antenna point to the Earth.

Modeling TipsThe parabolic primitive surface is not available in SimXpert V2010 for now, so we use a sphere surface instead. MD Nastran can support the parabolic surface. If you want to use the parabolic surface, you will need to do some extra work to manually modify the BDF file. The yokes which support the solar panels are deliberately ignored to simplify the thermal models.

For transient analysis cases, the time scale factor in the radiation enclosure form is very important. If you use second as the time unit for orbital period in Thermica, the time scale factor should be 3600.0.

Case1 (orbital period = 6307.1 sec.) Case2 (orbital period = 6595.5 sec.)

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Satellite in Orbit

Input File(s)

Files Description

QT13_satellite.dat MD Nastran SOL400/RC Network Solver thermal input file

QT14_sat_tran.dat MD Nastran SOL400/RC Network Solver thermal input file

QT39_sat_3arcs.dat MD Nastran SOL400/RC Network Solver thermal input file

QT40_sat_tran_3arcs.dat MD Nastran SOL400/RC Network Solver thermal input file

QT13_14_satellite.TRJINP Thermica v3 orbit input file for case 1

QT13_14_satellite.PNTINP Thermica v3 pointing input file for case 1

QT39_40_sat_3arcs.TRJINP Thermica v3 orbit input file for case 2

QT39_40_sat_3arcs.PNTINP Thermica v3 pointing input file for case 2