EIS MTM/TTM THERMAL BALANCE TEST STEADY- STATE ...

SOLAR-B Instrument

EIS MTM/TTM THERMAL BALANCE TEST STEADYSTATE RESULTS AND CONCLUSIONS Document No. BU/SLB-EIS/TN/028.01 Compiled by H. Mapson-Menard The University of Birmingham Astrophysics and Space Research Group 01/05/02

EIS MTM/TTM THERMAL BALANCE TEST STEADY-STATE RESULTS AND CONCLUSIONS INTRODUCTION This document describes the results and conclusions of the thermal balance tests performed on the EUV Imaging Spectrometer Mechanical/Thermal Test Model. The tests were carried out in the Rutherford Appleton Laboratory Space Test Chamber on 27/02/02 - 03/03/02 inclusive. Hot operational steady-state, cold non-operational steady-state and hot to cold transient tests were performed and temperatures recorded with a frequency of once per minute. Thirteen heater mats and seven heater resistors were used to control the temperature of the structure and components (respectively), and to simulate the external power loads predicted in orbit. See documents BU/SLB-EIS/TN/020.03, EIS MTM/TTM Thermal Balance Test Specification, Procedures and Predictions, and BU/SLB-EIS/PS/004.01, EIS MTM/TTM Thermal Test Preparations and Procedures, for more information.

TEST OBJECTIVES •= To determine the effective conductivity of the MLI •= To verify the thermal mathematical model The objective was not to reproduce exact orbital temperature distributions, but to achieve equilibrium in two steady-state cases. Therefore, heaters were set at predetermined dissipation values and the structure was allowed to come to the resulting equilibrium temperatures. Any discrepancies between the actual and predicted temperatures resulted in adjustments to the thermal mathematical model.

TEST RESULTS The results are presented in a schematic format for clarity. Figure 1 explains the schematic, which shows the important optical bench and component nodes. Figures 2 and 3 show the hot and cold test equilibrium temperatures. Figures 4 and 5 show the thermal mathematical model predictions for the hot and cold tests. Table 1 describes the sensor positions. The test and thermal model results for all sensors are shown in Graphs 1 and 2 for the hot and cold test cases respectively.

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Figure 1: Explanation of the Thermal Results Schematic Date: Date and Time results were aquired

Time:

08 07

Details: back panel

Result details

31 16 mirror

Sensor Number Heater Number

07 06

base panel

Temperature Power Dissipation

34 19 CCD radiator

35 20 ROE radiator

ROE

MHC

29 14

06 05

base panel

05 04

base panel

04 03

13 12

32 17 CCD support structure

base panel

base panel

30 15

03 02

base panel

12

02 01 base panel

base panel 11 10 base panel

33 18 grating

base panel

01 0a 0b

10 09 clamshell

base panel 09 08 front panel

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Figure 2: Hot Test Equilibrium Temperatures Date: 09/04/02

Time: NA Details: Hot Test Equilibrium Temperatures

32.3

08 07 1.17

Sensor Number

07 06

31 33.1 16

Heater Number

1.06

30.7

Temperature 1.28

Power Dissipation 31.1

06 05 1.18

33.1

05 04 2.33

-26.6

37

-54.5

36

34 -69.1 19

32.1

15.11

35 -46.2 20 3.25

23.1

2.23 13 12

32 17 0.28

04 03

03 02

28.1 34.5

45.5

29 14 4.31

58.4

30 15 2.36

4.15

2.77

12 35.3

02 01 39.9 2.69

11 10

38.6

2.75

43.1

01 0a 0b 5.79

10 09

33 18 1.03

39.4

41.1 2.16

40.0

09 08 4.46

4

Figure 3: Cold Test Equilibrium Temperatures Date: 22/04/02

Time: NA Details: Cold Test Equilibrium Temperatures

22.7

08 07 3.05

Sensor Number

07 06

31 20.5 16

Heater Number

1.09

11.6

Temperature 1.51


06 05 1.03

-4.9

05 04 1.00

-53.8

37

-72.0

36

34 -81.4 19

-11.0

12.91

35 -65.5 20 2.96

0.99 13 12

32 -21.8 17 0.28

04 03

03 02

-20.5 -11.2

29 -18.6 14 0.45

-9.5

30 15 0.28

0.16

2.01

12 -12.1

02 01 -10.7 0.15

11 10

-3.3

0.14

15.6

10 09

33 18 1.02

2.6

01 0a 0b 5.93

13.1 3.02

10.6

09 08 4.02

5

Figure 4: Hot Test Thermal Model Predicted Temperatures Date: 29/04/02

Time: 21:34 Details: Cold Test Model Temperatures

33.3

08 07 1.17

Sensor Number

07 06

31 34.9 16

Heater Number

1.06

31.7

Temperature 1.15


06 05 1.06

33.7

05 04 2.10

-26.2

37

-53.8

36

34 -66.8 19

33.3

13.75

35 -46.5 20 3.25

24.0

2.01 13 12

32 17 0.28

04 03

03 02

31.1 32.2

36.0

29 14 4.31

49.7

30 15 2.36

0.50

2.49

12 32.8

02 01 34.2 2.69

11 10

37.8

2.48

45.2

01 0a 0b 5.79

10 09

33 18 1.03

36.9

42.6 1.94

41.6

09 08 4.46

6

Figure 5: Cold Test Thermal Model Predicted Temperatures Date: 30/04/02

Time: 08:34 Details: Cold Test Model Temperatures

21.1

08 07 3.05

Sensor Number

07 06

31 20.1 16

Heater Number

1.09

12.8

Temperature 1.36


06 05 0.93

-0.3

05 04 0.9

-58.7

37

-74.3

36

34 -80.7 19

-4.1

11.70

35 -66.1 20 2.96

0.89 13 12

32 -18.9 17 0.28

04 03

03 02

-18.5 -8.7

29 -19.0 14 0.45

30 15

-7.8

0.28

0.14

1.81

12 -10.8

02 01 -10.1 0.15

11 10

-1.7

0.13

18.3

01 0a 0b 5.93

10 09

33 18 1.02

3.0

15.7 2.72

14.1

09 08 4.02

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Table 1: Thermal Sensor Descriptions Sensor Name EIS-TTS-01 EIS-TTS-02 EIS-TTS-03 EIS-TTS-04 EIS-TTS-05 EIS-TTS-06 EIS-TTS-07 EIS-TTS-08 EIS-TTS-09 EIS-TTS-10 EIS-TTS-11 EIS-TTS-12 EIS-TTS-13 EIS-TTS-14 EIS-TTS-15 EIS-TTS-16 EIS-TTS-17 EIS-TTS-18 EIS-TTS-19 EIS-TTS-20 EIS-TTS-21 EIS-TTS-22 EIS-TTS-23 EIS-TTS-24 EIS-TTS-25 EIS-TTS-26 EIS-TTS-27 EIS-TTS-28 EIS-TTS-29 EIS-TTS-30 EIS-TTS-31 EIS-TTS-32 EIS-TTS-33 EIS-TTS-34 EIS-TTS-35 EIS-TTS-36 EIS-TTS-37

Thermal Node 6032 6011 6009 6050 6049 6048 6047 6059 6028 6025 6024 6012 6010 6044 6014 6034 6027 6144 6114 6134 6127 6159 6128 6152 6106 6130 6121 6112 6079 6065 6063 6070 6064 6065 6076 6073 6080

Description of Position Inside, P1 +Y face bt P2, P12A0, P13, P9 Inside, P1 +Y face bt P2, P13, P14, P10 Inside, P1 +Y face bt P2, P14, P15, P11 Inside, P1 +Y face bt P2, P15, P16, P3 Inside, P1 +Y face bt P2, P15, P16, P3 Inside, P1 +Y face bt P2, P16, P7, P3 Inside, P1 +Y face bt P2, P16, P7, P3 Inside, P7 +Z face centre Inside, P8 -Z face centre Inside, P1 +Y face bt P9, P8, P12C0, P4 Inside, P1 +Y face bt P9, P12CO, P13, P4 Inside, P1 +Y face bt P10, P13, P14, P4 Inside, P1 +Y face bt P11, P14, P15, P4 Outside, P5 +Y face bt P2, P16, P7, P3 Outside, P6 +Y face bt P2, P13, P14, P10 Outside, P6 +Y face bt P2, P12A0, P13, P9 Outside, P6 +Y face bt P9, P8, P12CO, P4 On P5 MLI, bt P2, P16, P7, P3 On P6 MLI, bt P2, P13, P14, P10 On P6 MLI, bt P2, P12A0, P13, P9 On P6 MLI, bt P9, P8, P12C0, P4 On P7 MLI, centre On P8 MLI, centre On P2 MLI, bt PP16, P7, P1, P5 On P2 MLI, bt P13, P14, P1, P6 On P2 MLI, bt P12A0, P13, P1, P6 On P4 MLI, bt P8, P12CO, P1, P6 On P1 MLI, bt P10, P13, P14, P4 ROE structure MHC structure Mirror centre CCD Grating centre CCD radiator ROE radiator Particle shield top Particle shield bottom

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Graph 1: Complete Hot Test Temperature Results and Predictions Hot Test and Model Results for all Sensor Locations T(test)

T(model)

100

50

Temperature (degC)

0

-50

-100

-150

-200 1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 Sensor Number

Graph 2: Complete Cold Test Temperature Results and Predictions Cold Test and Model Results for all Sensor Locations T(test)

T(model)

50

Temperature (degC)

0

-50

-100

-150

-200 1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 Sensor Number

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DISCREPANCIES BETWEEN TEST AND MODEL RESULTS INTRODUCTION The thermal model was adjusted so it predicted similar temperatures and trends as the thermal test results showed. However, some temperatures could not be made to correlate effectively. This section discusses the reasons behind significant discrepancies of more than 5°C. FRONT MLI TEMPERATURE The thermal model predicts a temperature ~50°C warmer than the results from sensor 23, the front MLI section, in both the hot and cold tests. The efficiency of this MLI section has been greatly reduced to 0.29 Wm-2K-1, to allow the corresponding structural areas to reach realistic temperatures. This means that a larger amount of power is being radiated from this area than is indicated by the MLI temperature. Figure 6 shows the front of EIS during pre-test preparations. The position of the sensor in question can be seen (under the small section of black kapton tape). Also shown are gaps in the MLI where flaps have been created to allow the protrusion of the lifting eyebolt interface. It is believed that power is being dissipated from the structure through these gap areas and not via the MLI. The thermal model geometry includes this whole front section as one node (not including the aperture half), so any power being radiated from the area will be seen to travel via the MLI as the gaps are not featured in the geometry. The more power the MLI radiates, the warmer it will be, so the higher model temperature represent the power being radiated through the gaps. Figure 6: The Front MLI Section of EIS

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BACK MLI TEMPERATURE The thermal model predicts a temperature ~10°C warmer than the results from sensor 22, the back MLI section, in both the hot and cold tests. Figure 7 shows gaping regions of the MLI where overlaps are made in this section. It is believed that the sensor shows the MLI itself is working efficiently, but that power is being radiated from the gaping areas. Figure 7: The Back MLI Section of EIS

TOP CENTRAL MIRROR TUBE MLI TEMPERATURE The thermal model predicts a lower temperature for the top central mirror tube MLI section, for the hot and cold tests (sensor 18). It is believed that this is due to sensor 18 being placed close to the MLI hole for the purge vent. The purge vent is an aluminium component placed in the top panel. The proximity of the MLI temperature sensor to the MLI hole means that it is less effective in this localised region, and hence radiating more power than normal. The corresponding structure results (sensor 14) show that the overall performance of the MLI is still good.

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MODIFICATIONS MADE TO THE MATHEMATICAL MODEL SO THE THERMAL TEST RESULTS ARE REPRESENTED Document BU/SLB-EIS/TN/020.03, EIS MTM/TTM Thermal Balance Test Specification (Appendix 1), lists the changes that were initially made to convert the model from FM to MTM/TTM. Below, Table 2 lists the conductive links that were individually modified. •= Structure emissivity reduced from 0.9 to 0.75. Allowed the front optical bench area (sensor 01) to reach the required temperatures.

•= General MLI effective conductivity reduced by a factor of 0.6. Increased the overall temperature. Represents excellent MLI performance. •=

Front section MLI effective conductivity increased by a factor of 7.5. Represents MLI degradation due to overlaps and eyebolt interface flaps.

•= Back section of MLI effective conductivity increased by a factor of 2.0. Represents MLI degradation due to overlaps.

•= Central MLI section effective conductivity reduced by a factor of 0.55. Represents even better MLI performance in areas without holes or folds. Structure conductivity reduced by a factor of 2.5. Increased temperature gradients.

•= •= Front bulkhead split into two nodes representing a gradient between the front and rear panel skins. •= Baffle split into 9 additional nodes so that gradients in the X-axis, as well as the Z-axis, could be represented. •= Most heater mat power dissipations were reduced by 10%. The exceptions were heaters 0a, 0b, 1, 7 and 8 as these were integrated with a more successful method that will be used for flight heaters. •= Heater 12 power dissipation reduced by 3W in the hot test. Power loss could be due to summation of numerous effects, such as: power drawn to CCD cold cone, as the protective foils are not present power drawn to ROE cooling system, as the system does not feature the preferred surface finishes or protective foils •= ineffective power transmission to the structure itself, due to “bumpy”, resin-rich local thickening reducing surface contact with the heater •= power loss to harness CCD radiator heater resistor dissipation reduced by 9%. Represented power dissipated to STC (and not conducted to radiator). •= •=

•=

Table 2: Modified Conductive Links Node I

Node J

6036 6059 6028 6028 6028 6063 6064 6065

6019 6047 6025 6023 6021 6059 6025 6012

New Value Original Description (W/K) Value (W/K) 0.4 N/A Linking front (clamshell) bulkhead front and rear skins 0.05 N/A Linking rear panel to rear mirror tube base 0.3 N/A Linking front panel to base panel 0.3 N/A Linking front panel to side panel 0.3 N/A Linking front panel to side panel 0.15 0.1 Mirror to structure link 0.25 0.1 Grating to structure link 0.01 1 MHC to structure link

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THERMAL SENSITIVITIES AND IMPLICATIONS MHC LINK TO STRUCTURE 10% link reduction

=> ~6°C MHC temperature increase => ~1°C mounting structure temperature decrease

The MTM/TTM conductive link was significantly reduced, creating a large gradient between the MHC and its mounting structure. This interface should be better coupled. MHC OUTER SURFACE FINISH The sensitivity of the MHC temperature to its outer box optical properties varies with temperature. The MHC box should therefore have a black finish so the maximum power coupling with the structure is achieved. ROE LINK TO STRUCTURE 0.01W/K link decrease

=> 1°C ROE box temperature increase

Due to dominant radiative control within the EIS structural enclosure, the optical properties of the ROE box have little affect on the ROE temperature when T(ROE) ~ T(structure). However, as the above figures show, when the ROE is 10°C warmer than the structure, the link plays a significant role in determining the ROE operating temperature. ROE OUTER SURFACE FINISH Correct surface finishes Plain aluminium finish

=> T(ROE) = 29°C => T(ROE) = 45°C

To minimise the power load on the ROE cooling system, the correct surface finishes should be produced. The optical properties assumed in the thermal model (to produce the 29°C hot case operating temperature) are: α = 0.1 ε = 0.05 for general surfaces, and α = 0.9 ε = 0.9 for the top surface that views the base of the thermal shield The thermal shield connected to the ROE radiator should have similar optical properties. INTERNAL HEATER POWER (TEST CONFIGURATION) 1W power increase

=> 2°C general temperature increase => 4°C temperature increase in area of power increase

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OPTICAL PROPERTIES OF THE STRUCTURE Graph 3 shows the normalised variation of two node temperatures with structure emissivity. The nodes featured correspond to the base plate area immediately behind the clamshell (6032) and the front panel in front of the grating (6028). Reducing the emissivity also had the affect of increasing the gradients across the structure. It is unlikely that the structure has ε < 0.75. Higher values of ε did not produce the high temperatures witnessed behind the clamshell during the tests. Graph 3: Node Temperature Variation with Structure Emissivity

Normalized Temperature Variation

Node Temperature Variation with Structure Emissivity 12 10

N(6032)

N(6028)

8 6 4 2 0 0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Structure Emissivity

MLI PERFORMANCE The MLI performance was better than predicted. ESA MLI efficiency tables predicted ~0.039 Wm-2K-1 for good quality, large blankets with an average structure and MLI temperature of ~210K. The MLI conductivity predicted by the thermal model, to generate the correct test temperature results, was ≤ 0.02 Wm-2K-1, except areas with overlaps and holes. This value was verified by calculating the power radiated from sections of the MLI using the MLI temperatures recorded during the hot and cold tests. This was then used to calculate the link required for the power to be conducted through the specified area of MLI. The conductive link required was also found to be ≤ 0.02 Wm-2K-1.

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THERMAL MATHEMATICAL MODEL TEMPERATURE PREDICTIONS FOR THE EIS FLIGHT MODEL The adjusted EIS thermal model was modelled in orbit for the hot operating, cold operating and 25° hot survival environment cases. This highlighted any problems caused by the adjustments made to the model. Figures 8, 9 and 10 show the predicted in flight temperatures for the cases listed above. The models were modified so that the expected surface finishes were on all components. Also, the effective conductivity of the front MLI node was reduced to 0.078 Wm-2K-1 (from 0.29 Wm-2K-1). No other conductive links were adjusted from the MTM results model.

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Figure 8: Hot Operational Case Thermal Model Predicted Temperatures Date: 30/04/02

Time: 16:36 Details: Hot Flight Model Temperatures

27.1

08 07 1.0

Sensor Number

07 06

31 26.6 16

Heater Number

26.8

Temperature 1.0


06 05 0.5

34 -64.2 19

-9.3

35 20

05 04

23.4

04 03

13 12

32 -50.6 17 3.0

23.3

03 02

27.3 25.4

29.2

29 14 6.6

35.0

30 15 4.5

27.6

27.4

12 30.7

28.4

11 10

27.7

01 0a 0b

10 09

33 18

27.8

02 01

27.4

09 08

16

Figure 9: Cold Operational Case Thermal Model Predicted Temperatures Date: 30/04/02

Time: 17:00 Details: Cold Flight Model Temperatures

28.2

08 07 0.5

Sensor Number

07 06

31 28.1 16

Heater Number

29.1

Temperature 1.0


06 05 1.0

30.7

05 04 1.0

34 -73.1 19

31.0

04 03 1.0

35 -14.3 20

13 12

32 -59.1 17 3.0

03 02

30.5 31.8

30.5

29 14 6.6

37.1

30 15 4.5

30.5

1.0 12 32.8

30.5

11 10 1.0

31.3

02 01

28.9

01 0a 0b 1.0

10 09

33 18 31.5

1.5

30.7

09 08

17

Figure 10: Hot 25°° Survival Case Thermal Model Predicted Temperatures Date: 30/04/02

Time: 16:34 Details: Hot 25deg Survival Flight Model Temperatures

26.9

Sensor Number

08 07

07 06

31 27.4 16

Heater Number

28.5

Temperature Power Dissipation

34 -22.1 19

35 -18.4 20

29.8

06 05

31.4

05 04

32.3

04 03

13 12

32 -19.9 17

03 02

20.0 33.5 11.7

29 14

41.4

30 15

49.8

50.2

12 41.7

43.0

11 10

54.5

01 0a 0b

10 09

33 18

50.4

02 01

50.2

09 08

18

CONCLUSIONS The EIS MTM/TTM thermal balance tests were successful. The effective conductivity of the MLI was found to be ≤ 0.02 Wm-2K-1. The thermal model was adjusted so it predicted the equilibrium temperatures, in both the hot and cold test cases, within ± 5°C. The main differences between the original and adjusted thermal models were the improved MLI performance, the structure optical properties, the conductivity of the panels, and the conductive links between components. Discrepancies, larger than 5°C, between the test results and thermal model predictions were found to be caused by temperature sensor placements and model resolution - not the assumptions used within the model. It was therefore found that the thermal mathematical model was verified. The CCD temperature sensor had not been placed on/near a CCD, but on the CCD support structure, so the CCD cooling path was not verified past the CCD radiator and particle shield. A sensor has now been placed on a CCD, so the conductivity of the braid connecting the upper particle shield and CCD can be verified during system thermal tests. It was concluded that some modifications should be made to the EIS Flight Model to optimise performance. These are listed below. MODIFICATIONS REQUIRED FOR THE FLIGHT MODEL •= Larger MLI overlaps, to ensure consistent MLI performance in joint regions. •= An extra section of MLI to cover the eyebolt interface, to improve the front section MLI performance. •= Possible MLI layer reduction, to reduce the hot case operational temperatures. •= Better contact (larger thermal link) between the MHC and the structure, to keep the MHC operating temperature to a minimum. •= Dark MHC surface finish, to keep the MHC operating temperature to a minimum. •= Correct ROE box and cooling system optical finishes, to insure minimal heat loads on the ROE cooling system from the structure.

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