solar orbiter euv spectrometer
DESCRIPTION
Solar Orbiter EUV Spectrometer. Thermal Design Considerations Bryan Shaughnessy. Spacecraft Sunshield. Aperture (100mm*100mm). Primary Mirror (100mm*100mm). Baffles. Optical path. Width = 0.3m. Length 1.4 m. Slit Assembly. Grating. Heat Stop. Basic Configuration. - PowerPoint PPT PresentationTRANSCRIPT
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Solar Orbiter EUV Spectrometer
Thermal Design Considerations
Bryan Shaughnessy
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Basic Configuration
Detector Assembly
Aperture
(100mm*100mm)
Grating
Length 1.4 m
Width =
0.3m
Slit Assembly
Optical path
Primary Mirror
(100mm*100mm)
Heat Stop
Baffles
Spacecraft
Sunshield
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Basic Thermal Requirements
• Detector temperature < -60 deg C (target -80 deg C)• Structure and optics:
– Multilayer coatings (if used) are assumed to be a limiting factor. < 100 deg C assumed at present.
• Thermal Control System Mass TBD• Thermal Control System Power TBD (minimise)
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Thermal Environment
Distance From Sun AU
Heat Flux
W/m2
Through
Aperture, W
1.2
1.0
0.9
0.8
0.6
0.4
0.2
951
1370
1691
2140
3805
8562
34250
9.51
13.7
16.9
21.4
38.0
85.6
342.5
Cold case non operational
Hot case non operational
Start Up
Hot Case operational
Cold Case Operational
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Solar Thermal Loads at 0.2 AU
350 WThrough Aperture 250 W
200 WAbsorbed at primary
100 W
50 W3 W
103 WAbsorbed at baffles
47 WAbsorbed atheat stop(‘focussed’)
(Absorbing Optics/No Aperture Filter)
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Irradiance Profile at Primary Mirror(No Aperture Filter)
35 KW/m2
30 KW/m2
25 KW/m2
20 KW/m2
15 KW/m2
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
The Thermal Challenges
• Reject heat input to system of ~350W at 0.2AU– Filter at aperture?– Maintaining sensible temperatures/gradients within instrument– Getting heat to radiators (or to spacecraft cooling system)– Spreading the heat across the radiators
• Prevent heat loss when instrument is further from the Sun– Maintaining sensible temperatures within instrument– Minimising heat transfer to radiators (or to spacecraft cooling
system)– Minimising power required for survival heaters
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Heat Rejection by Radiators
• Radiator heat rejection capability a function of:
– Emissivity ~ 0.95 for black paint– Efficiency ~ 0.96– View-factor to space ~ 0.95
• How to transfer heat to radiator?
Radiator (1.4 m x 0.3 m)
Temperature Heat Rejection
K °C W/m2 Watts
233
253
273
293
313
333
343
353
373
-40
-20
0.0
20
40
60
70
80
100
144
200
270
357
461
587
654
734
907
62
87
117
154
200
254
284
318
393
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Thermal Design Options
• Solar absorptivity of the optics:– High (i.e., SiC) – remove more heat from primary mirror– Low (e.g., gold coated) – remove more heat from heatstop – but likely restriction
on coating temperature• Coupling to radiators:
– Fitted with heat pipes or loop heat pipes to distribute heat– Primary mirror connected to radiator via thermal straps and/or heat pipe
evaporator.• How to get high thermal conductance coupling?
– Heat loss minimised during cold phases by:• Louvers• Temperature dependent coatings (major development programme required)• Use of loop heat pipes• Use of variable conductance heat pipes
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Loop Heat Pipe Concept
Solar load
LHP Evaporator
Radiator (condenser)
Flexible lines
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Loop Heat Pipe Concept
•Advantages:•Control over amount of heat removal (reduce when further from Sun)•Flexible couplings allow for pointing of primary mirror
•Technical Challenges: •Selection of working fluid compatible with hot and cold environments
• ammonia: -40 °C →+80 °C• methanol: +55 °C → +140 °C
• Freezing of working fluid in radiator during cold cases?• Thermally coupling the primary mirror to the evaporator • Redundancy?
• multiple lines to same evaporator, multiple evaporators?
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Thermal Model Predictions
Radiator Area, m2 T, deg C Radiator Area, m2 T, deg C Baffle 0.2 105 0.4 48 Primary 0.1 105 0.2 46 Heat stop 0.02 33 0.02 15 Detector 0.1 -80 0.1 -80 TOTAL 0.22 - 0.72 - Width* 0.16m - 0.51m - * assuming 1.4 m instrument length
(Absorbing Optics/No Aperture Filter/Heat pipes or loop heat pipes to radiators)
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
Detector Cooling
• Aluminium filtering blocks any remaining solar thermal loads
• Detector fitted in a thermally isolated enclosure:– Low emissivity shielding– Low conductivity mounts
• Dedicated radiator attached to detectors via a cold finger– Multistage to shield thermal loads from spacecraft sunshield?
• Electric heaters fitted for temperature control and outgassing operations
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Solar Orbiter EUS: Thermal Design ConsiderationsBryan Shaughnessy, Rutherford Appleton Laboratory
THE END