Thermal Design

Matthieu GASQUET

Cranfield University / Rutherford Appleton Laboratory

Coseners HouseJuly 9th 2002EUS consortium meeting

TopicsEUS Thermal environment & requirements

Steady State thermal analysis

Transient thermal analysisParameters Results

Conclusion

Thermal Environment(1/2)During the nominal phase (0.2 to 0.8 A.U.), heat load varies from 2200W/m2 to 34000W/m2

Graph1

33569.59094

32291.94278

30392.45598

28124.9802

25722.45326

23358.16422

21139.52701

19120.16377

17316.95835

15724.94619

14327.92072

13105.1012

12034.9331

11097.04225

10273.09432

9547.04797

8905.097225

8335.471605

7828.186102

7374.788154

6968.123634

6602.130458

6271.661639

5972.335766

5700.412054

5452.686389

5226.405191

5019.194028

4828.998405

4654.034693

4492.749255

4343.784423

4205.950065

4078.199695

3959.610471

3849.366265

3746.743359

3651.098334

3561.857713

3478.509154

3400.59391

3327.700325

3259.458259

3195.534259

3135.627406

3079.465632

3026.802635

2977.41509

2931.100228

2887.673749

2846.967979

2808.830212

2773.121282

2739.714314

2708.493582

2679.353522

2652.197863

2626.938817

2603.49642

2581.797904

2561.777137

2543.374149

2526.534712

2511.20993

2497.355922

2484.933532

2473.908033

2464.248944

2455.929788

2448.927957

2443.22455

2438.804266

2435.65529

2433.769243

2433.141116

2433.769243

2435.65529

2438.804266

2443.22455

2448.927957

2455.929788

2464.248944

2473.908033

2484.933532

2497.355922

2511.20993

2526.534712

2543.374149

2561.777137

2581.797904

2603.49642

2626.938817

2652.197863

2679.353527

2708.493582

2739.714314

2773.121282

2808.830212

2846.967979

2887.673749

2931.100222

2977.41509

3026.802635

3079.465634

3135.627404

3195.534265

3259.458259

3327.700328

3400.59391

3478.509158

3561.857713

3651.09833

3746.743359

3849.366261

3959.610465

4078.199689

4205.950065

4343.784429

4492.74925

4654.034693

4828.998405

5019.194028

5226.405191

5452.686389

5700.412054

5972.335777

6271.661646

6602.130458

6968.123634

7374.788165

7828.186113

8335.471605

8905.097238

9547.04797

10273.09431

11097.04225

12034.9331

13105.10121

14327.92075

15724.94619

17316.9583

19120.16377

21139.52701

23358.16422

25722.45326

28124.98023

30392.45598

32291.94272

33569.59094

34021.72998

Heat Load Vs Days

Days from Perihelion

Heat load (W/m2)

heat_load_time_function

DAY 133569.59094

32291.94278

30392.45598

28124.9802

DAY 525722.45326

23358.16422

21139.52701

19120.16377

17316.95835

DAY 1015724.94619

14327.92072

13105.1012

12034.9331

11097.04225

DAY 1510273.09432

9547.04797

8905.097225

8335.471605

7828.186102

DAY 207374.788154

6968.123634

6602.130458

6271.661639

5972.335766

DAY 255700.412054

5452.686389

5226.405191

5019.194028

4828.998405

DAY 304654.034693

4492.749255

4343.784423

4205.950065

4078.199695

DAY 353959.610471

3849.366265

3746.743359

3651.098334

3561.857713

DAY 403478.509154

3400.59391

3327.700325

3259.458259

3195.534259

DAY 453135.627406

3079.465632

3026.802635

2977.41509

2931.100228

DAY 502887.673749

2846.967979

2808.830212

2773.121282

2739.714314

DAY 552708.493582

2679.353522

2652.197863

2626.938817

2603.49642

DAY 602581.797904

2561.777137

2543.374149

2526.534712

2511.20993

DAY 652497.355922

2484.933532

2473.908033

2464.248944

2455.929788

DAY 702448.927957

2443.22455

2438.804266

2435.65529

2433.769243

DAY 752433.141116

2433.769243

2435.65529

2438.804266

2443.22455

DAY 802448.927957

2455.929788

2464.248944

2473.908033

2484.933532

DAY 852497.355922

2511.20993

2526.534712

2543.374149

2561.777137

DAY 902581.797904

2603.49642

2626.938817

2652.197863

2679.353527

DAY 952708.493582

2739.714314

2773.121282

2808.830212

2846.967979

DAY 1002887.673749

2931.100222

2977.41509

3026.802635

3079.465634

DAY 1053135.627404

3195.534265

3259.458259

3327.700328

3400.59391

DAY 1103478.509158

3561.857713

3651.09833

3746.743359

3849.366261

DAY 1153959.610465

4078.199689

4205.950065

4343.784429

4492.74925

DAY 1204654.034693

4828.998405

5019.194028

5226.405191

5452.686389

DAY 1255700.412054

5972.335777

6271.661646

6602.130458

6968.123634

DAY 1307374.788165

7828.186113

8335.471605

8905.097238

9547.04797

DAY 13510273.09431

11097.04225

12034.9331

13105.10121

14327.92075

DAY 14015724.94619

17316.9583

19120.16377

21139.52701

23358.16422

DAY 14525722.45326

28124.98023

30392.45598

32291.94272

33569.59094

DAY 15034021.72998

heat_load_time_function

Heat Load Vs Days

Days from Perihelion

Heat load (W/m2)

EUS thermal requirements (1/2)The Radiator Area is limited by the footprint of the EUS casing (1.4m x 0.4m = 0.56m2)

Coatings, and in particular multilayer coatings applied on mirrors have to be maintained in a reasonable range of temperature ( below 100C )

The EUS should be cooled as much as possible with a passive control system because of the limited mass and power budget ( also more reliable):Radiators, Multi Layer Insulation, Thermal control coatings,

EUS thermal requirements (2/2)A small part of energy has to reach the detector ( few Watts)Materials used for mirror and structure have to be thermally stable:

Steady State analysis (1/3)Assumptions:

Based on the worst hot case: 34000 W/m2Radiator temperature fixed to 50 CMirrors and Heat Stop temperature fixed to 61 CNo view factors between the heat shield and the radiators

Steady State analysisGrazing incidence telescope

M1 absorptivity0,10M2 absorptivity0,70rastering mirror absorptivity0,25total heat absorption on M1 (W)10,23total heat absorption on M2 (W)61,24total heat absorption on rastering mirror (W)0,66heat load coming from the rastering mirror to the slit 1,97Minimum Total radiator area (m2)0,125

Telescope design(2/2)Off-axis design

The off-axis design is the most challenging one from a thermal point of view

M1 absorptivity0,10heat stop absorptivity0,70heat stop transmissivity0,05M2 absorptivity0,83total heat absorption on M1 (W)26,30total heat absorption on heat stop (W)165,69total heat absorption on M2 (W)9,82heat load coming from M2 to the slit 2,01Minimum Total radiator area (m2)0,349

Transient simulationBased on the Off-axis telescope designMade with ESARAD/ESATAN and I-DEASThe simulation is based on the nominal phase orbit ( 0.2 to 0.8 A.U)The heat load is applied to the heat shield and the primary mirrorThere is no physical contact between the heat shield and the rest of the spacecraft

The geometric model (1/2)Different parts have been modeled:The heat shield The telescope casingThe mirrors and the heat stopThe radiators for the primary mirror and the heat stop

The geometric model (2/2)The area of the radiator has been fixed to the results given by the worst hot case steady state calculation:0.39 m2 for the M1 radiator area0.01 m2 for the heat stop radiator area

Model descriptionDifferent coatings are applied on each face of the parts to control the temperature

Thermal strategies

Three parameters have been studied in this simulation:

the emissivity of the telescope casing and heat shield

The absolute conductance between M1 and its radiator

The absorptivity of M1

Results (1/4)M1 temperature without radiator:

Results (2/4)M1 temperature with a conductance of 0.5 W/C between the radiator and M1, a high emissive coating and M1 either lowly or highly absorptive:

Results (3/4)M1 temperature with a low emissive coating on the heat shield, M1 lowly absorptive, and a conductance of 50 W/C.

Results (4/4)M1 temperature with a high emissive coating (MLI) on the telescope, M1 either lowly or highly absorptive, and a conductance of 50 W/C

Comments With a good absolute conductance and a large radiator, it seems that the thermo-optical properties of M1 dont have a big impact on its temperature.With a high emissive coating on the telescope casing and heat shield, the maximum temperature limit is in the requirements, but it is oscillating a lot.

Comments necessary to put heat switches or Variable conductance heat pipe to control the temperature with a better accuracy

Temperature (C)Absolute Conductance (W/K)-2000.01-200.0100.5101.0150100

Graph2

0.01

0.01

0.5

1

100

Conductance VS Temperature

Conductance VS Temperature

Feuil1

-2000.01

-200.01

00.5

101

150100

Feuil1

Conductance VS Temperature

Feuil2

Feuil3

Future workHeat shield thermal analysis and designDetailed analysis of the temperature mapping on M1Variable conductance heat pipe implementationParametric study of the model with Radiator area

conclusionImportance of heat shield thermal properties and mechanical mounting.The off-axis design seems feasible from a thermal point of view provided that:the heat shieldis conductively isolatedthe required thermo-optical properties (alpha and epsilon) are achieved on the heat shield at the elevated temperaturesthe required radiator area is accommodated the necessary thermal links are provided between the M1 mirror and its radiator