Transcript Section 4.3 - Radiator Thermal Design

GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
DOE/NASA Mechanical Systems Radiator Assy, March 27, 2003
GLAST Large Area Telescope:
Mechanical Systems Peer Review
March 27, 2003
Section 4.3 - Radiator Thermal Design
Liz Osborne
Lockheed Martin
Thermal Engineer
[email protected]
Section 4.3 - Mechanical Systems Radiator Assy
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DOE/NASA Mechanical Systems Radiator Assy, March 27, 2003
Topics
• Requirements
• Thermal Design Overview
• Thermal Design Environments
– Orbital Environment
– Spacecraft Interface
• Thermal Control
– Variable Conductance Heatpipes
– Thermal Surfaces
– Heaters
• Thermal Model
• Results
– Hot Operation, Cold Operation, Survival
• Summary & Future Work
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Driving Thermal Requirements
Parameter
Requirement
Design
Margin
Comply
Ver.
Method
Operational Temperature Limits (RIT)
Temperature Stability (RIT)
Survival Temperature Limits
Reservoir Average Power, Normal Mode
Reservoir Peak Power, Normal Mode
Anti-Freeze Average Power, Normal Mode
Anti-Freeze Peak Power, Normal Mode
Reservoir Average Power, Survival Mode
Reservoir Peak Power, Survival Mode
Anti-Freeze Average Power, Survival Mode
Anti-Freeze Peak Power, Survival Mode
Survival Power draw from LAT
Margin, Heater Sizing, Normal Mode
Margin, Heater Sizing, Survival Mode, Cold
VCHP Failure, Hot Operation
Based on:
-10 C to +15 C
+/- 7C
-20 C to +30 C
48 W
TBD
0W
0W
TBD
TBD
TBD
TBD
155 W
Duty Cycle <70%
>30% margin on
power to fully close
VCHP's
+15°C
-5°C to +10°C
+/- 4°C
-20 °C to TBD
13 W
48 W
0W
0W
42 W (27V)
48 W (29V)
91 W
232 W (35V)
61 W
31 %
+5/+5°C
+/- 3°C
0°C/TBD
35 W
TBD
0W
0W
TBD
TBD
TBD
TBD
94 W
39 %
Y
Y
Y
Y
TBD
Y
Y
TBD
TBD
TBD
TBD
Y
Y
TBD, no
power
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
57%
+14°C
27%
+1 °C
allocation
A, T
A, T
Y
Radiator Level IV Design Specification, LAT-SS-00394-1-D6, Draft, Dated 5 Mar 2003
LAT Mechanical Systems Interface Definition Dwg, Radiator-LAT Interface, LAT-DS-01221, Draft,
Dated 25 Feb 2003
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Thermal Design Overview
•
•
Radiators
– Two panels, parallel to the
LAT XZ-plane
– Size per panel: 1.82 m x
1.56 m = 2.8 m2
– Construction
• Aluminum honeycomb
structure
6 Variable-Conductance Heat
pipes (VCHP’s) on each
Radiator panel
– Interface to XLAT CCHP’s
and LAT DSHP’s at each
Radiator Interface
Temperature (RIT)
– Provide active feedback
control of grid temperature
through VCHP’s
RIT (6 places)
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Thermal Design Environments
Thermal Case:
LAT Orientation
Altitude, km
Beta Angle
Earth IR, W/m2
Earth Albedo
Solar Flux, W/m2
Solar flux from Radiators
mis-alignment, W/m 2
Survival
Cold
+X on sun line, +Y 90
deg out of orbital plane
575
0
208
0.25
1286
0
Hot
-Z on sun line, +Y 90 +Z 90 deg out of orbital
deg out of orbital plane plane, +X on sun line
575
450
0
0
208
265
0.25
0.4
1286
1419
0
6
Cold Orientation
Survival Orientation
Hot Orientation
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Orbital Heatloads
Radiator Orbital Heatrates for Cold, Hot & Survival
-Y Hot
-Y Hot+16.9W misalignment
+Y Hot
-Y Cold
+Y Cold
-Y Survival
+Y Survival
600
Watts on Radiator
500
400
300
200
100
0
0
10
20
30
40
50
60
70
80
90
100
Time in orbit, minutes
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Interface to Spacecraft & LAT
•
Solar Arrays strong influence on Radiators
– Hot design: Arrays begin 0.52m from radiator
• Orbit-average heatload on 1 radiator (to IRD spec) is 73W
• Conservative design approach
– Actual Spectrum Astro solar array design is 1.32m from radiator
– Cold & Survival design: Arrays begin 1.32m from radiator
• Corresponds with actual Spectrum Astro Design
•
Spacecraft mount points (2/radiator)
–
•
5W max total heat leak to Radiators
LAT mount points (2/radiator)
–
5W max total heat leak to Radiators
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Thermal Control (1 of 3)
•
VCHP’s
– Interface to XLAT CCHP’s and LAT DSHP’s at each RIT
• Removes 612W (hot) and 497W (cold) from instrument
– Non-condensable gas mass, 0.42g (conservative)
– Cold operation: Provides active feedback control of grid temperature
through VCHP logic & heaters
• Maintains RIT above –5 C
– Hot operation: VCHP full open
• RIT temperature not controlled
– Survival: VCHP closed
• Reservoir heaters on full to drive up gas front and close off pipe
•
Thermal Surfaces (5 yr EOL)
– Radiator & Reservoirs: 10mil FOSR – Second Surface Aluminized Teflon
• a/e: .08/.85 (BOL), .24/.85 (EOL)
• Approved to withstand AO degradation
– Radiator backside: MLI Blanket
• e* range .01 to .03
• Aluminized kapton, outer layer facing S/C
– a/e: .12/.04 (BOL), .16/.04 (EOL)
– RIT and transport of VCHP: MLI Blanket
• No radiation included in thermal model
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Thermal Control (2 of 3)
• Heaters
– Operational
• VCHP reservoirs
– 3.5W each (27V), Total 42W (48W @ 29V)
– Feedback control from RIT
– Survival
• VCHP reservoirs
– Operational heaters are switched on full
• Anti-freeze heaters (condenser length)
– 4 total zones, 1 zone per 3 heatpipes
– Controlled by thermostats and RTD’s
» Enabled lower setpoints
– Primary control set ON/OFF -62°C/-58°C
» Redundant set ~4C lower with offset RTD’s
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Thermal Control (3 of 3)
VCHP Thermal Control Heaters and Sensors
+Y Radiator Shown Only
Zone 1
Heaters
Thermostat Controllers
T T
T T
Zone 2
+Z
+X
+Y
RTD’s
Heaters
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Thermal Model
•
•
TSS Model
– Surface model to calculate view factors
and orbital fluxes
– Thermal Synthesizer System, v.11C
– Input: geometry, material properties,
optical properties, environmental
parameters, orbit definition
– Output: RADKS (eAF), Heatrates (W),
Conductances and Capacitances for input
into SINDA Thermal Model
SINDA Model
– Numerical network of capacitances &
conductances
– Cullimore & Ring SINDA/FLUINT 4.5
– 4710 Total Nodes (Radiators & VCHP’s)
Imbedded VCHP’s
– Input: conductances, capacitances, interfaces, sources, heaters,
TSS outputs, VCHP logic
– Output: temperatures, temperature stability, VCHP gas front,
Heatpipe loads, average heater power
Reservoirs
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Thermal Results – Hot (1 of 3)
Steady State Orbit Average Heatmap for –Y Radiator
W
290.2
16.9
260.9
83.5
3.1
-651.8
-2.8
0.0
Energy Balance
from LAT
from Solar (misalignment)
from Earthshine & Albedo
from Solar Arrays
from Bus
to SPACE
to LAT MLI
SUM
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Thermal Results – Hot (2 of 3)
Hot RIT Temperatures
Reservoir Average Heater Power = 0 W
12
+Y Radiator
-Y Radiator
Temperature, °C
10
8
6
4
2
0
0
50
100
150
200
250
300
350
400
450
500
Time over 5 orbits, minutes
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Thermal Results – Hot (3 of 3)
VCHP #2 Failure (worst case) increases max RIT temperature to +14°C
RIT Hot Temperature with +Y VC#2 Failure
16
14
12
Temperature, °C
•
RIT VC2
10
8
6
4
2
0
0
50
100
150
200
Section
4.3 - Mechanical
Systems Radiator Assy
Time over
2 orbits,
min
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Thermal Results – Cold (1 of 3)
RIT Cold Temperatures over 5 Orbits
Reservoir Average Heater Power = 13 W
0
0
50
100
150
200
250
300
350
400
450
500
-0.5
Temperature, C
-1
-1.5
-2
-2.5
-3
-3.5
-4
-4.5
Time over 5 orbits, min
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Thermal Results – Cold (2 of 3)
Snapshot Temperatures at time=410min
Reservoir Average Heater Power = 13 W
Radiator –Y VCHP’s
Radiator +Y VCHP’s
°C
0 1
2
RIT
Transport
3
4 5
0 1
2
RIT
3
4 5
Transport
Condenser
Condenser
Reservoir
Reservoir
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Thermal Results – Cold (3 of 3)
Temperature Profile of +Y radiator VCHP#0 over 5 Orbits
10
Reservoir Heater
RIT
Temprature, C
0
-10
80% up condenser
-20
Reservoir
-30
-40
60% up condenser
-50
40% up condenser
20% up condenser
Condenser
Bottom
-60
-70
0
100
200
300
400
500
Time over 5 orbits, min
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Thermal Results - Survival
Minimum VCHP temperature = -65 C
Reservoir heaters on full = 42W/27V (Max Temperature = 42 C)
Antifreeze heaters average power = 91W: with 30% margin =118 W
RIT Survival Temperatures over 5 Orbits
-18.8
0
50
100
150
200
250
300
350
400
450
500
-19
-19.2
Temperature, C
•
•
•
-Y Radiator
+Y Radiator
-19.4
-19.6
-19.8
center pipes
-20
-20.2
Time over 5 orbits, min
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Summary & Future Work
•
Summary
– Thermal design of Radiators presented
• VCHP’s used to control the interface to the LAT
• Thermal control surfaces optimize radiator and protect from environment &
spacecraft
• Operational Heaters have been sized for VCHP control
• Survival Heaters maintain the VCHP’s above limits
– Thermal analysis results presented
•
•
•
•
Hot: Max RIT temperature is +10 °C
HP Failure increases max RIT to +14°C
Cold: Min RIT temperature is –5 °C
Survival: Min RIT temperature is –20°C
– Heaters maintain VCHP’s above –65°C
– In compliance with the thermal requirements
• Open TBD’s need resolution
•
Future Work
– Update model as necessary
– Run system engineering trade analyses
• Nominal hot case, Rocking mode, Transition mode, NCG mass optimization, 10yr mission
– Finalize location and mount design of SS thermostats
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