GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
CDR/CD-3 Review, May 12-16 2003
LAT Thermal Systems
Analysis
Jeff Wang
LMCO
LAT Thermal Engineer
jeff.wang@lmco.com
Document: LAT-PR-01967
Section 8.C Thermal Design
1
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Agenda
•
•
•
•
Introduction
Design trade analyses performed and results
Thermal systems overview
Thermal parameters
– Requirements and interfaces
– Analysis parameters, environments, and case definitions
• Analysis update
–
–
–
–
Hot- and cold-cases analyses
Survival-case analysis
Other non-design case analyses
Failure-case analyses
• Thermal Control System Design
• Summary and Further Work
Document: LAT-PR-01967
Section 8.C Thermal Design
2
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Thermal Systems Overview
•
•
•
Radiators
– Two panels, parallel to the LAT XZ-plane
– Size per panel: 1.82 m x 1.56 m = 2.84 m2
– Aluminum honeycomb structure
Heat Pipe design
– Constant-conductance heat pipes on Grid Box
– Ammonia working fluid
– Extruded aluminum, with axial groove casings
Heat pipes
– Variable-conductance Heat Pipes
•
•
–
6 VCHP’s per Radiator panel
Provides feedback control of grid temperature
Isothermalize grid structure
X-LAT Heat Pipes
•
•
–
MLI thermal shielding surrounding
ACD, Grid Box, Electronics
Top Flange Heat Pipes (not shown)
•
–
Down Spout Heat Pipes
connect Grid to Radiators
Remove waste heat from electronics
Connect radiators for load-sharing
Downspout Heat Pipes
•
Transport waste heat from grid to Radiators
On-Orbit Thermal Environment and LAT Process Power
Earth IR
Earth Albedo
Solar Flux
LAT Process Power
Document: LAT-PR-01967
Survival
208
0.25
1286
0
Cold
208
0.25
1286
535
Hot
265
0.40
1419
612
Units
W/m2
W/m2
W
X-LAT Heat Pipes shunt
electronics power to Radiators
Active VCHP control allows for variable Radiator
area to maintain constant interface temp to LAT
LAT Thermal Overview
Section 8.C Thermal Design
3
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Downspout and X-LAT Heat Pipes
Document: LAT-PR-01967
Section 8.C Thermal Design
4
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Thermal System Schematic Diagram
ACD
Thermal
Accommodation
Direction of arrow signifies
direction of heat flow
TKR
Grid Base Ass’y
Rad
Mnt
Bkt
Radiator
EMI Skirt
Electronics
Htr Sw
Box
Radiator
Solar
Array
CAL
EMI Skirt
Htr Sw
Box
Rad
Mnt
Bkt
X-LAT Plate
Spacecraft
Solar
Array
LV Payload Attach Fitting
LAT Thermal Schematic Diagram
Document: LAT-PR-01967
Section 8.C Thermal Design
5
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Internal Thermal Design Changes Since Delta-PDR
The following design changes have been incorporated in the CDR thermal model
•
•
•
•
Added high emissivity black paint to TKR sidewalls
– Lowers peak TKR temperature by radiatively coupling modules together
– Raises ACD survival temperature and lowers TKR hot-case peak temperature by
improving radiative coupling between the two
Connected TKR to Grid with 4 heat straps/module
– Increases temperature gradient across the thermal joint
– Improves thermal joint reliability compared to Delta-PDR thermal gasket design
Replaced outer ACD MLI blanket layer with germanium black kapton (FOSR before)
– Preferred by subsystem, since MLI is unsupported
– Marginally raises survival case temperatures
Increased total LAT power (w/o reservoirs) to 615 W (was 602W)
– Total is still within the 650 W allocation
•
•
•
•
CAL and TKR power increased 21.6 W
Electronics power dropped 8.3 W
ACD power remained about the same
– Net effect is to raise hot-case peak temperatures for the TKR and CAL
Added S-bend to VCHP transport section
– Results in net drop in survival heater power needs
•
•
–
–
Reduces survival-case heat leak out of Grid
Increases anti-freeze radiator heater power
Improves flexibility for better compliance at integration
Increases transport capacity requirement on VCHP’s
Document: LAT-PR-01967
Section 8.C Thermal Design
6
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Thermal Interface Design Changes Since Delta-PDR
The following interface changes have been incorporated in the CDR
thermal model
• Increased Radiator area to 2.78 m2 but decreased
efficiency by shortening it
– Modified Radiator aspect ratio at request of Spectrum to
accommodate solar arrays
– This change results in slightly higher LAT hot-case temperatures
• Finalized Radiator cut-outs
– Added cut-outs for solar array launch locks
– Increased size of cut-out for solar array mast
– This change results in slightly higher LAT hot-case temperatures
Document: LAT-PR-01967
Section 8.C Thermal Design
7
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Trade Studies Since Delta-PDR
• Solar Array interface for survival/cold cases
– Delta-PDR total survival grid + anti freeze heater power calculated to
be 171 watts (28.0 watts reservoirs)  191 W Total
– Using the Spectrum PDR Solar Array, survival heater power
increased to 244 W (28 W for reservoirs)
– With no solar array, total survival heater power increased to 330
watts
– Conclusion: using the Spectrum Astro PDR solar array in the LAT
cold- and survival-case models was agreed as reasonable
• Reservoir size reduction
– Desire to maximize radiator area and temperature margins
– Used Delta-PDR model to assure that smaller reservoir could totally
close heat pipes for survival and provide adequate cold case control
– Reduced size provides more condenser length
– Conclusion: reduce reservoir size from Delta PDR volume of 288 cc
to 75 cc. This produces a net gain of 100 mm in condenser length
Document: LAT-PR-01967
Section 8.C Thermal Design
8
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Thermal Systems Peer Review RFA Status
RFA 13-Stowed Case
Limiting LAT component –VCHP Reservoirs if heaters not activated
Document: LAT-PR-01967
Section 8.C Thermal Design
9
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Thermal Systems Peer Review RFA Status
•
•
•
•
•
•
•
RFA-14 Heater Flight sizing-at least 30% margin at minimum voltage
RFA-15 With all YS-90 Tracker sidewalls, peak tracker temperature at CDR
RFA-16 ACD limits –The ACD has already agreed to the lower(-40 C) limits of the
Environmental specification
RFA-21 Backup test heater for flight anti-freeze heaters: not necessary due to control of
environment in test
RFA-22 Maximum Tracker temperature with .03 MLI e* - Temperature rises to 24.75 C
RFA-25 Correlation of flight thermistors at unit level - will be done both for the Tracker and
Calorimeter to establish proper limits at LAT level TVAC test
RFA-30 AO Effects on Germanium Black Kapton-See paper on AO from International SAMPE
Technical conference, November 1996. Note that pristine Germanium Black kapton showed
no effects from the AO. The ACD will have a scrim outer layer for the thermal blanket; it is
recommended that the 2nd layer of the blanket also be germanium black kapton.
Document: LAT-PR-01967
Section 8.C Thermal Design
10
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Driving Thermal Design Requirements
Parameter
Ver.
Driving
Comply Meth
Req
od
Requirement
Design
Margin
> 5.4 m2
5.57 m2
0.17 m2
Y
I
433-IRD0001
3.2.3.4.1
Max process power indefinite dissipation
615 W @ T(max)
615 W LAT + 35 W
Rad @ 29.4 C
5 C uncertainty
+ 0.6 C
Operating
Y
T, A
LAT-TD00225-5
Peak process power dissipated for 10 min (#)
720 W for 10 min
@ T(max)
720 W for 10 min @
<T(max)
Y
T, A
LAT-TD00225-5
Min process power indefinite dissipation
495 W @ T(min)
495 W @ -10 C
50% Rad
control auth.
Y
T, A
75 W/Rad
73.4 W
0 W/Rad
Y
T, A
450 - 575 km
450 km hot-case
575 km cold-case
OK
Y
A
OK
Y
T, A
OK
Y
A
Y
T, A
Y
T, A
Minimum Radiator area (#)
Capable of normal operation when loaded by 75 W/Rad of heat
from SC solar arrays
Orbit range of 450 km min to 575 km max
Capable of maintaining thermal control during exposure to IR,
Albedo, Solar fluxes
Provide thermal control with LAT pointed 2pi/24/7/365 during
any normal LAT mode
LAT max.min operating temp
+30 C / -15 C
+29.4 C / -3 C
Stability of LAT Control Temp point (3)
+/- 3 C
< +/- 3 C
VCHP heater power when LAT is on (at Vmin)
< 35 W
13 W @ 27 V
22 W
Y
D
VCHP heater power when LAT is off (at Vmin)
+0. 6 C / 12 C
LAT-TD00225-5
433-IRD0001
3.2.3.4.5
LAT-TD00224-5
LAT-SS00778
LAT-TD00225-5
< 50 W
42 W @ 27 V
8W
Y
D
When off, orbit-average survival heater power at 27 V min (not
incl control auth margin)
< 220 W
158 W
62W
Y
D
*Pending
When off, peak survival heater power
< 560 W
533 W (incl > 30%
control auth)
27 W (5%)
Y
D
*Pending
Y
T, A
433-MAR0001
During Obs t-vac, TCS capable of full functionality "lying on its
side"
(1): Total Power = Process Power + VCHP Reservoir Heater Power = 615 + 35 = 650W
(2): Margin on heater power keeps minimum LAT temperature above AT limits
Document: LAT-PR-01967
OK
(3): LCT defined as the Grid side
of the Grid--DSHP interface point
Section 8.C Thermal Design
11
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Thermal Model Details: LAT Dissipated Power
• Dissipated power values are pulled directly from the LAT power
budget held by the LAT System Engineer
• All power allocations and geographical distribution is under
CCB control
A Sum m ary of LAT Dissipated Pow er for Use in Therm al Design
2. LAT Dissipated Power
Martin Nordby, Dick Horn, Jeff Wang
LAT-TD-00225-05
Print Date: 18-Apr-03
Eff. Date: 16-Apr-03
Special Status
Normal Operations
Quantity
TranCold
Hot
10 Min
Surv.
Alloc.
Unit Hot Cold
sition Case
Case
Peak
Total
58.0 105.0
530.0
591.0
650.0
750.0 W
Total on Grid
0.0
0.0
208.8
228.5
244.9
283.7 W
TKR
139.5
153.0
160.7
190.8 W
16
CAL
60.3
65.0
73.5
81.0 W
16
ACD
9.0
10.5
10.7
11.8 W
1
Total on X-LAT
0.0
47.0
286.2
327.5
370.1
408.3 W
TEM
43.2
47.0
53.1
58.6 W
16
TPS
148.5
164.0
185.4
204.5 W
16
GASU
19.8
22.0
24.9
27.4 W
1
1
SIU
30.0
21.6
26.5
30.0
33.0 W
1
1
EPU
38.7
53.0
59.9
66.1 W
2
1
PDU
17.0
14.4
15.0
17.0
18.7 W
1
1
Radiators
58.0
58.0
35.0
35.0
35.0
58.0 W
16
16
Comments
Evenly distributed up 4 sides of TKR module
Evenly distributed up 4 sides of CAL
Evenly distributed around 4 sides of BEA
1 board/bay
1 P.S. board/bay for TEM
1 lg board spanning 4 center bays
2 bds in 2 bays (1 hot, 1 cold)
2 bds in 2 bays, both hot (+ 1 cold spare)
2 bds in 2 bays (1 hot, 1 cold)
Bottom of Radiator panels at VCHP's
LAT Dissipated Power Values
Source: LAT-TD-00225-05 “A Summary of LAT Dissipated Power for Use in Thermal Design”, 16 Apr 2003
Document: LAT-PR-01967
Section 8.C Thermal Design
12
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Thermal Model Details: Electronics Box Dissipated Power
Cold Case Power Dissipation
Hot Case Power Dissipation
LAT +Y
LAT +Y
+Y Side
LAT Radiator
-X Side
3rd Layer
TEM/TPS
X-LAT Tot
+Y Side
LAT Radiator
Bay 12
EPU-B
Bay 13
Empty
Bay 14
Empty
Bay 15
Empty
Bay 12
EPU-B
Bay 13
Empty
Bay 14
Empty
Bay 15
Empty
12.0
12.0
12.0
12.0
14.9
14.9
14.9
14.9
Bay 8
PDU-B
Bay 9
GASU
Bay 10
GASU
Bay 11
SIU-B
Bay 8
PDU-B
Bay 9
GASU
Bay 10
GASU
Bay 11
SIU-B
12.0
12.0
21.9
12.0
14.9
14.9
27.3
14.9
Bay 4
PDU-A
Bay 5
GASU
Bay 6
GASU
Bay 7
SIU-A
Bay 4
PDU-A
Bay 5
GASU
Bay 6
GASU
Bay 7
SIU-A
26.4
12.0
21.9
33.6
31.9
14.9
27.3
44.9
Bay 0
EPU-A
Bay 1
Empty
Bay 2
Empty
Bay 3
EPU-A
Bay 0
EPU-A
Bay 1
Empty
Bay 2
Empty
Bay 3
EPU-A
31.3
12.0
31.3
44.9
14.9
94.5
191.7
286.2
12.0
-Y Side
LAT Radiator
LAT Top View
LAT +X
+X Side
Sun Side
-X Side
3rd Layer
TEM/TPS
X-LAT Tot
131.7
238.5
370.1
14.9
-Y Side
LAT Radiator
LAT +X
+X Side
Sun Side
44.9
LAT Top View
LAT Dissipated Power Distribution in Special Electronics Boxes
Source: LAT-TD-00225-04 “A Summary of LAT Dissipated Power for Use in Thermal Design”, 13 Mar 2003
Document: LAT-PR-01967
Section 8.C Thermal Design
13
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Environmental Temperature Limits
Component
Tracker Module @ SSD
Calorimeter Module
TEM Box (1)
EPU Box (1)
SIU Box (1, +)
PDU Box (1, +)
GASU Box (1, +)
ACD, BEA Sub-Ass'y (2, +)
TSA Sub-Ass'y (+)
Grid Box Sub-Ass'y (+)
CCHP Components
VCHP Components
Radiator Sub-Ass'y (+)
Low Temp Limits
High Temp Limits
Qual
AT Oper. Oper. AT
Qual
-30
-20
-15
30
35
50
-30
-20
-15
25
40
50
-40
-35
-30
45
50
55
-40
-35
-30
45
50
55
-40
-35
-30
45
50
55
-40
-35
-30
45
50
55
-40
-35
-30
45
50
55
-25
-20
-15
30
35
40
-40*
-35
-30
35
40
45
-40*
-15
-10
30
35
40
-40*
-15
-10
30
35
40
-40*
-15
-10
30
35
40
-40
-35
-30
20
25
30
Survival
Low
High
-30
50
-30
50
-40
60
-40
60
-40
60
-40
60
-40
60
-40
45
-50
45
-40
40
-67
60
-67
60
-67
60
Notes:
All temperatures are in degrees C; see acronym list for an explanation of acronyms used
Temperatures shown are for the hottest/coldest extremity of the subsytem, except as indicated
(+) Protoflight units only. Qual temps shown are for proto-flight qual testing
(*) Not all performance requirements will be met at EOL for this test. See Appendix A for a full explanation
(1) Temperatures shown are for the box interface to its heat sink
(2) BEA temperature limits apply to the full ACD assembly as well
Document: LAT-PR-01967
Section 8.C Thermal Design
14
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Verification Test Temperatures
•
Component Level Testing Minimum test margins
– 5 C margin from Operating to AT level
– 5 C margin from AT to LAT PFQ level
•
LAT level Thermal Vacuum Test strategy
– Drive all components to their ATP/PFQ level
• Virtually impossible to achieve
• Will most likely be limited by one or two components
Document: LAT-PR-01967
Section 8.C Thermal Design
15
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Thermal Math Model and Status
•
TSS Model-Calculates radks and heat rates.
–
–
•
252 Surfaces External, 454 Internal
2787 Active Nodes External, 1436 Internal
Sinda Model.
– Submodels.
•
•
•
•
•
•
•
•
ACD CDR model
Detailed TKR model
Reduced Cal model
Detailed Grid model
Updated X-LAT and Electronics model
Bus model includes solar arrays and SV
– IRD array for hot case.
– Cold case/survival uses Spectrum Astro PDR
solar array.
Detailed radiator and heat pipes
9812 nodes total
– Heat pipe logic in VCHPs to predict gas
front
– Added VCHP heater control logic
•
Logic will be part of SIU control of thermal system
Model status: the model is mature and includes all
subsystem updates for CDR
Document: LAT-PR-01967
Section 8.C Thermal Design
16
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Thermal Model Details: Thermal Interfaces
• Thermal interfaces to the Spacecraft
– All specified in LAT IRD (433-IRD-0001) except cold-/survival-case
solar array definition, which has been arrived at by mutual agreement
between Spectrum, LAT, and the GLAST PO
• Environmental parameters
– PDR and Delta-PDR analysis shows that Beta = 0, pointed-mode is
the LAT hot-case
– Solar loading is per the LAT IRD
– Sky-survey attitude and “noon roll” is based on an assumed slew
rate of 9 degrees/min, max
• Thermal design case parameters are tabulated on the following
chart
Parameter
Hot
SC interface temperature
LAT MLI effective emittance
SC MLI surface emissivity
Conductive leak: SC bus to Grid
Conductive leak: SC to each Rad
Optical Properties
Material/Interface Properties
50
0.01
0.05
5
5
EOL
Hot
Surv/
Unit
Cold
-10
C
0.03
0.05
0
W
0
W
BOL
Cold
SC-LAT Thermal Interface Parameters
Document: LAT-PR-01967
Section 8.C Thermal Design
17
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Thermal Model Details: Design Case Details
Thermal Case:
Survival
Cold
Orbit Definition and Environment
LAT Operational Mode
Safe-Hold [1]
Pointed [2]
LAT Orientation
+X on sun line, +Y
-Z on sun line, +Y
90 deg out of orbital 90 deg out of orbital
plane
plane
Altitude
575
575
Beta Angle
0
0
Orbit inclination
28.5
28.5
Orbit eccentricity
0
0
Earth IR
208
208
Earth Albedo
0.25
0.25
Solar Flux
1286
1286
Orbit-averaged solar flux due to re-pointing
0
0
Solar flux from Radiators mis-alignment
Tolerances (not included in thermal model) +X-axis on sun line
Sun line in +XZto < +/-15 deg
plane to < +/- 1 deg
Instrument Status and Control
LAT process power mode
VCHP status/reservoir heater power
Material/Interface Properties
Solar Array
Total Array Size (2 wings-3 panels/Wing)
Distance from radiator
Boom size cross-sectional area
Panel Front alpha
Solar cell Efficiency
Effective Front Panel Alpha
Panel front emissivity
Panel back alpha
Panel back emissivity
Boom alpha
Boom emissivity
Thru conductance (front-back, per panel)
Total Thermal Capacitance (per panel)
Nominal
Hot
Rocking
Transition
Unit
Sky-Survey [3]
-Z on nadir line,
sun line in +XZ
plane
450
0
28.5
< 0.01
265
0.4
1419
noon flip*
6
Sun line in +XZplane to < +/- 1
deg
Pointed [4]
+Z 90 deg out of
orbital plane, +X
on sun line
450
0
28.5
0.01
265
0.4
1419
0
6
Sun line in +XZplane to < +/- 1
deg
Sky-Survey [3]
-Z on nadir line,
sun line in +XZ
plane
450
0
28.5
< 0.01
265
0.4
1419
noon flip*+27
6
Sun line in +XZplane to < +/- 1
deg
Re-Point [6]
Change from
Pointed[2] to
Pointed[4]
450
0
28.5
0.01
265
0.4
1419
27
6
km
deg
deg
--W/m2
Survival
Minimum
Maximum
Maximum
Maximum
Maximum
100% closed/100% TBD% closed/<60%
Fully open/0
Fully open/0
Fully open/0
Fully open/0
cold-case
cold-case
hot-case
hot-case
hot-case
hot-case
Survival SA
Cold SA
Hot Real SA Design Hot SA Hot Real SA
Hot Real SA
4.7m X 1.54 m, 3
4.7m X 1.54 m, 3 4.7m X 1.54 m, 4.7m X 1.54 m, 4.7m X 1.54 m, 4.7m X 1.54 m,
panels with 1" gaps panels with 1" gaps 3 panels with 1" 3 panels with 1" 3 panels with 1" 3 panels with 1"
gaps
gaps
gaps
gaps
1.3
1.3
1.3
0.52
1.3
1.3
0.127
0.127
0.127
0.0254
0.127
0.127
0.92
0.92
0.92
0.9
0.92
0.92
26%
26%
17%
NA
17%
17%
0.68
0.68
0.75
0.9
0.75
0.75
0.86
0.86
0.84
0.85
0.84
0.84
0.18
0.18
0.4
0.5
0.4
0.4
0.91
0.91
0.87
0.88
0.87
0.87
0.39
0.39
0.45
0.8
0.45
0.45
0.75
0.75
0.72
0.9
0.72
0.72
56.2
56.2
56.2
74.3
56.2
56.2
6135
6135
6135
4665
6135
6135
W/m2
W
W/m2
m
m^2
%
W/K
J/K
LAT Thermal Case Description
Source: LAT-TD-00224-04 “LAT Thermal Design Parameters Summary”, 19 Mar 2003
Document: LAT-PR-01967
Section 8.C Thermal Design
18
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Temperature Predicts and Margins to Operating Limit
•IRD Hot-Case peak temperatures predicts vs. “Real” Case Solar Array
–Tracker: 29.4 C vs. 24.3 C
–Calorimeter: 22.0 C vs. 16.8 C
–Electronics: 36.0 C vs. 30.3 C
Component
Cold
Survival
Limits
Cold
Hot
Operating Operating
Limits
Limits
MarginsMarginsIRD Hot IRD Hot Real Hot Real Hot
TKR(SSD) -30.0
-15.0
30.0
29.4
0.6
24.3
5.7
CAL BP
-30.0
-15.0
25.0
22.0
3.0
16.8
8.2
EPU*
-40.0
-30.0
45.0
18.2
26.8
12.2
32.8
GASU*
-40.0
-30.0
45.0
22.1
22.9
17.2
27.8
PDU*
-40.0
-30.0
45.0
16.5
28.5
10.4
34.6
SIU*
-40.0
-30.0
45.0
18.2
26.8
12.2
32.8
TPS*
-40.0
-30.0
45.0
34.9
10.1
29.2
15.8
TEM*
-40.0
-30.0
45.0
36.0
9.0
30.3
14.7
ACD BEA
-40.0
-15.0
30.0
22.5
7.5
17.5
12.5
ACD TDA
-50.0
-30.0
35.0
26.3
8.7
21.6
13.4
All temperatures are in degrees C
Temperatures shown are for the hottest/coldest extremity of the subsytem, except as indicated
Hot case temperature predicts include 5 C analysis uncertainty margin
For cold and survival cases, 5 C uncertainty not used because of heater control
(*) Temperatures shown are for the box interface to its heat sink
Cold
MarginsMarginsCold
Survival Survival
-3.3
-0.2
-2.8
3.3
-2.6
-2.6
3.6
3.8
0.4
-5.9
11.7
14.8
27.2
33.3
27.4
27.4
33.6
33.8
15.4
24.1
-23.7
-18.5
-19.0
-19.5
-18.8
-19.0
-19.5
-19.5
-19.1
-25.6
6.3
11.5
21.0
20.5
21.2
21.0
20.5
20.5
20.9
24.4
Temperature Predicts for LAT Subsystems
Document: LAT-PR-01967
Section 8.C Thermal Design
19
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Sensitivity of Temperature Predictions
Base
Case Real
-10%
Hot
Conductors
TKR
24.3
2.3
CAL
16.8
1.4
EPU
12.2
0.8
GASU
17.2
1.4
PDU
10.4
0.6
SIU
12.2
0.8
TPS
29.2
2.7
TEM
30.3
2.8
ACD BEA
17.5
1.1
ACD TDA
21.6
1.7
Document: LAT-PR-01967
-10%
Radks
5.1
5.1
5.3
5.2
5.2
5.3
5.2
5.2
5.2
5.3
+10%
Power
4.3
3.6
3.0
3.6
2.8
3.0
4.7
4.8
4.0
3.7
+10%
Conductors
-1.8
-1.1
-0.6
-1.1
-0.5
-0.6
-2.2
-2.3
-0.9
-1.4
Section 8.C Thermal Design
+10%
Radks
-2.6
-2.7
-3.0
-2.3
-2.6
-3.0
-2.9
-2.9
-2.9
-3.1
-10%
Power
-3.6
-2.9
-2.5
-3.0
-2.1
-2.5
-4.2
-4.3
-1.9
-3.1
20
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Hot Case TKR Peak Temperature Gradient
•
•
Peak temperature gradient is along the heat transfer path to the top of a center TKR module
Key temperature gradients
–
–
–
Up TKR wall: 5.7 deg C
TKR—Grid thermal joint: 3.8 deg C
Top of Grid—DSHP at VCHP: ~7.7 deg C
Location
Top tray
Wall at top tray
Closeout at top of st'd tray
Bottom of regular tray wall
Top of Cu strap interface
Top of grid
Temp (degC)
17.80
23.20
24.20
19.10
18.50
14.70
DSHP-4 top row, Rad
DSHP-4, at VCHP
Top of Radiator by VCHP4
Maximum temp gradient
-Y Rad +Y Rad
7.00
6.70
5.60
5.30
-3.00
-3.80
27.20 28.00
TKR Maximum Temperature Gradient in the LAT
Document: LAT-PR-01967
Section 8.C Thermal Design
21
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Hot Case Environmental Orbit Loads
Hot Case Orbit: Beta 0, +Z Zenith, +X Sun Pointing
sun
600
Solar Constant =1419 W/m 2
Planet Power=265W/m 2
Albedo=0.4
400
300
200
Total-Rad1
100
Total-Rad2
0
46 0
7.
1
93 7
4.
3
14 4
01
.5
17
27
17
2
18 8
68
23 .7
35
.8
28
0
32 3
70
37 .2
37
.3
38
78
38
7
42 9
04
46 .5
71
51 .7
38
.9
56
06
Absorbed Flux (W)
500
Time(seconds)
Environmental Load on Radiators for Hot-Case Orbit
Document: LAT-PR-01967
Section 8.C Thermal Design
22
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Hot Case QMAP
Instrument Power
2068 W to space
2009 W orbital heating
615 W
42 W solar array heating
62 W orbital heating
83 W to space
235 W orbital heating
17 W
from
bus
252 W orbital heating
83.6 W solar array heating
83.5 W solar array heating
27 W
from
bus
28 W
from
bus
653 W to space
650 W to space
4.0 W to space
3.9 W to space
Z
2.1 W solar
Y
Document: LAT-PR-01967
2.1 W solar
Hot Operational Orbit Average Qmap
Section 8.C Thermal Design
Orbital heating
Radiated to space
Bus heating
Bus heating
VCHP reservoir-space
VCHP reservoir
23
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Hot Case IRD Temperatures
Predicted LAT Temperatures for Hot-Case Orbit
Document: LAT-PR-01967
Section 8.C Thermal Design
24
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Hot Case IRD Tracker Temperature
Predicted TKR Temperature Showing Analysis
Predict is Stabilizing Toward an Asymptote
Document: LAT-PR-01967
Section 8.C Thermal Design
25
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Hot Case IRD Radiator Temperatures
Document: LAT-PR-01967
Section 8.C Thermal Design
26
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Hot Case with “Real” PDR Solar Arrays
Document: LAT-PR-01967
Section 8.C Thermal Design
27
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Survival Case Orbit
Survival Orientation: +X Sun Pointing
sun
160
140
Absorbed Flux(W)
120
100
80
60
40
Solar Constant =1286 W/m2
Planet Power = 208 W/m2
Albedo = 0.25
20
Total-Rad1
Total-Rad2
0
0
960
1816
1920
2880
3841
Time(seconds)
3945
4801
5761
Environmental Load on Radiators for Survival-Case Orbit
Document: LAT-PR-01967
Section 8.C Thermal Design
28
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Survival Case QMAP
1568 W to space
Make-up Heaters
1529 W orbital heating
73.8 W
21 W solar array heating
53 W orbital heating
69 W to space
15 W
from
bus
130 W orbital heating
40 W solar array heating
259 W to space
11 W
from
bus
43.5 W
heater
power
131 W orbital heating
11 W
from
bus
39 W solar array heating
44.5 W
heater
power
260 W to space
9.9 W to space
Z
10.0 W to space
22 W heater power+solar
23 W heater power+solar
Y
Survival Orbit Average Qmap
Document: LAT-PR-01967
Section 8.C Thermal Design
Orbital heating
Radiated to space
Bus heating
Bus heating
VCHP reservoir
Anti-freeze heaters
VCHP reservoir
29
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Survival Temperatures
Document: LAT-PR-01967
Section 8.C Thermal Design
30
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Survival Case Temperatures
Predicted LAT Temperatures for Survival-Case Orbit
Document: LAT-PR-01967
Section 8.C Thermal Design
31
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Survival Case Radiator Temperatures
Predicted Radiator Temperatures for Survival-Case Orbit
Document: LAT-PR-01967
Section 8.C Thermal Design
32
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Survival Heater Power
• Survival heater power (orbit average)
•
•
•
•
Grid make-up heaters
VCHP anti-freeze heaters
X-LAT Plate heaters
Total heater power
• Allocation:
• Heater power margin:
69 W
89 W
0W
158 W
220 Watts
+62 W (43% margin)
Requirement
Design
Margin
Comply
Ver.
Method
When off, orbit-average survival heater power
at 27 V min (not incl control auth margin)
< 220 W
158 W
62 W (39%)
Y
D
When off, peak survival heater power
< 560 W
533 W @ 35 V (incl
>38% control auth)
27 W (5%)
Y
D
Control margin on heater power, Grid
> 30%
62%
25%
Y
D
Control margin on heater power, Anti-Freeze
> 30%
80%
38%
Y
D
Parameter
Document: LAT-PR-01967
Section 8.C Thermal Design
33
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
VCHP Reservoir Heater Power
• Reservoir Heater Size
– 3.5 W/Reservoir @ 27V = 42 W for 12 (100% duty cycle)
– Survival minimum required power = 1.5 W/reservoir
– Heaters sized at > 200% of required minimum
• Reservoir Duty Cycles
– Hot Case: 0% and 0 W
– Cold Case: ~ 30%  13 W orbit-averaged power
– Survival: 100%  42 W orbit-averaged power (heaters locked on
while LAT is off)
Parameter
VCHP heater power when LAT on (at
Vmin)
VCHP heater power when LAT off (at
Vmin)
Control margin on heater power
Document: LAT-PR-01967
Requirement
Design
Margin Comply
< 35 W
13 W @ 27 V
25 W
Y
< 50 W
42 W @ 27 V
8W
Y
> 30%
200%
170%
Y
Section 8.C Thermal Design
34
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Cold Case Temperatures
Predicted Temperatures for Cold-Case Orbit
Document: LAT-PR-01967
Section 8.C Thermal Design
35
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Cold Case Radiator Temperatures
Predicted Radiator Temperatures for Cold-Case Orbit
Document: LAT-PR-01967
Section 8.C Thermal Design
36
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Failure Analyses—Hot-Case
Case
Orbit
Solar Array
#
Parameters
9
Hot Case Spectrum SA
10
Hot Case Spectrum SA
11
Hot Case Spectrum SA
12
Hot Case Spectrum SA
13
Hot Case Spectrum SA
14
Hot Case Spectrum SA
15
Hot Case Spectrum SA
16
Hot Case Spectrum SA
17
Hot Case Spectrum SA
Radiator
Temp
Calculated
Calculated
Calculated
Calculated
Calculated
Calculated
Calculated
Calculated
Calculated
5 yr
5 yr
5 yr
5 yr
5 yr
5 yr
5 yr
5 yr
5 yr
Heat Pipe
Failure
VCHP # 2
VCHP # 0
XLAT # 2
XLAT # 0
DSHP #0
DSHP #2
Grid HP # 2
Grid HP # 3
Grid HP # 0
NCG
18
Hot Case
Spectrum SA
Calculated
5 yr
None
19
Hot Case
Spectrum SA
Calculated
5 yr
None
20
Hot Case
Spectrum SA
Calculated
5 yr
None
Heater
Failure
None
None
None
None
None
None
None
None
None
1 Grid Htr
Closed
1 Rsvr Htr
Closed
None
0ther
None
None
None
None
None
None
None
None
None
None
None
TKR-grid
conduction
lost (1 Bay)
Summary of Hot-Case Failure Analyses
Document: LAT-PR-01967
Section 8.C Thermal Design
37
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Hot Thermal Failure Analysis Results Summary
•
Change in peak temperatures
Real Hot
TKR
24.3
CAL
16.8
EPU
12.2
GASU
17.2
PDU
10.4
SIU
12.2
TPS
29.2
TEM
30.3
ACD BEA
17.5
ACD TDA
21.6
•
XLAT
Pipe 0
Failed
2.1
2.0
0.9
3.7
0.4
0.9
0.9
0.9
1.4
1.7
XLAT
Pipe 2
Failed
1.1
1.7
1.5
19.2
-0.8
1.5
18.1
16.9
1.3
1.0
VCHP
Pipe 0
Failed
1.0
0.9
1.0
0.5
2.0
0.3
1.0
1.0
0.6
0.9
VCHP
Pipe 2
Failed
2.1
2.0
0.9
3.7
0.3
0.9
0.9
0.9
1.4
1.7
Fail
DSHP #2 DSHP #0 Grid HP # Grid HP # Grid HP # 1 Grid Htr Reservoir
Failed
Failed 3 Failed 2 Failed 0 Failed Closed Htr #2 on
2.9
1.2
1.6
1.2
0.6
1.8
2.1
2.6
1.1
1.3
0.9
0.4
2.2
2.0
0.7
0.3
-0.1
0.0
0.1
1.6
0.9
-0.8
0.4
0.0
0.0
0.1
0.9
3.7
0.7
-0.6
0.2
0.1
-0.1
0.6
0.4
0.7
0.3
-0.1
0.0
0.1
1.6
0.9
0.8
0.3
0.0
0.1
0.1
1.6
0.9
0.8
0.3
0.0
0.1
0.1
1.6
0.9
1.6
0.6
0.7
0.3
0.3
3.2
1.4
2.3
0.9
0.5
0.3
0.4
1.9
1.7
Failure of heat straps for center Bay increases peak Tracker
temperature 4.3 o C
Document: LAT-PR-01967
Section 8.C Thermal Design
38
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Failure Analyses—Cold/Survival Cases
Case
#
Orbit
Parameters
Solar Array
Radiator
Temp
NCG
Heat Pipe
Failure
1
Cold Case
Real Cold
Calculated
None
None
2
Survival Case
Real Cold
Calculated
None
None
3
Survival Case
Real Cold
Calculated
None
None
4
Survival Case
Real Cold
Calculated
None
None
5
Survival Case
Real Cold
Calculated
None
None
Heater Failure
1 VCHP
Reservoir
1 VCHP
Reservoir
Heater Open
1Grid Heater
Open
Pri & BU VCHP
Reservoir
Heaters on
1 Anti-freeze
Heater Circuit
on
•Change in peak temperatures and average power below
Surv Anti
Both
Cold
Surv
Surv
Freeze Reservoir
Reserv
Reserv Grid Htr Htr Fails circuits
Cold
Htr Fails Survival Htr Fails
Fails
On
On
TKR
-3.3
-6.5
-23.7
-0.5
-0.5
0.0
-0.1
CAL
-0.2
-0.9
-18.5
-0.5
-0.5
0.3
0.0
EPU
-2.8
-8.0
-19.0
-0.2
-1.0
0.0
0.0
GASU
3.3
-7.4
-19.5
-0.3
-0.6
0.0
-0.1
PDU
-2.6
-8.0
-18.8
-0.4
-1.2
0.1
0.0
SIU
-2.6
-7.9
-19.0
-0.1
-0.1
0.0
-0.1
TPS
3.6
-8.3
-19.5
-0.3
-0.6
0.0
-0.1
TEM
3.8
-8.3
-19.5
-0.3
-0.6
0.0
-0.1
ACD BEA
0.4
-7.7
-19.1
-0.3
-0.9
0.0
-0.1
ACD TDA
-5.9
-6.4
-25.6
-0.5
-0.3
0.1
0.0
Grid+Anti-fr Htrs(W)
0
0
158
162.1
150.2
216.8
158
Heaters-Resv(W)
13
13.9
42
38.5
42
42
84
* For cold and survival cases, 5 C uncertainty not used because of heater control
•Case 4-Reservoir temperatures rise to 1050 C with both sets of heaters
On
Summary of Cold-/Survival-Case Failure Analyses
Document: LAT-PR-01967
Section 8.C Thermal Design
39
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Thermal Failure Analysis Results Summary
•
•
•
•
With one exception, all hot case failure scenarios led to a maximum
temperature rise of less than 50 C
Failure of the XLAT #2 Heat Pipe Below the GASU causes large
temperature rises in the GASU and TEM and TPS
– GASU remains within operating limits
– TEM and TPS rise above operating limit for “real” solar array
– TEM and TPS would rise above ATP for IRD hot Case
– These temperatures only seen when pipe under operating GASU
section fails-can switch to B side of GASU to eliminate large rise
Heater failure cases do not require intervention, I.e. switch to backups
– Heater power within limits
– Temperatures within limits
Primary and secondary reservoir heaters cannot simultaneously be on in
survival( 1050 C max)
Document: LAT-PR-01967
Section 8.C Thermal Design
40
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Integration and Test Flow
Tower
Integration
TKR
CAL
Grid
LAT
Integration
Integrate
TKR/CAL &
TEM's with
Grid
E
A
TEM/TPS
O
Environmental Tests
F
L
L
C
Survey
E
EPU
Observatory
Integration
LAT Test
A
F
Integrate
E-Boxes
w/ Grid
M
Thermal
Balance
EMI/EMC
Survey
Thermal Vac
C
M L
SIU
Delivery
L Sine Vibe
PDU
Mass
Properties
O Survey
GASU
Htr Box
Survey
C
Integrate EMI
Skirt, Htr Switch
Boxes
EMI SHIELD
M
L
Modal
survey
Install
Radiators
Observatory
Integration
Final Mass
Properties
M
L
Acoustic
ACD
Integrate ACD
L
X-LAT Plate
C
Integrate X-LAT
C
O Survey
Pre-Ship
Survey
M
Mech Fit-Check
Ship to
SA
Radiators
E
Electrical
InterfaceTests
A
Aliveness
Tests
F
Functional
Tests
Survey:
O
Limited
Performance
L
Optical
M
C
Comprehensive
Performance
Muon
v CDR 3/14/03
LAT Integration and Test Flow
Document: LAT-PR-01967
Section 8.C Thermal Design
41
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Thermal Balance/Thermal-Vacuum Tests
•
Test goals
–
Thermal-Balance
•
•
•
•
–
Thermal-Vacuum
•
•
•
•
•
Verify that the LAT thermal control system is properly sized to keep maximum temperatures within
mission limits, while demonstrating at least 30% control margin
Validate the LAT thermal control system control algorithms
Verify that the VCHP control effectively closes the radiator to when the LAT is off
Validate the LAT thermal model by correlating predicted and measured temperatures
Verify the LAT’s ability to survive proto-qualification temperature levels at both the high and low
end
Test for workmanship on hardware such as wiring harnesses, MLI, and cable support and strainreliefs which will not have been fully verified at the subsystem level
Demonstrate that the LAT meets performance goals at temperature
Provide stable test environment to complete LAT surveys, as detailed in LAT-MD-00895, “LAT
Instrument Survey Plan”
Configuration
–
–
–
–
–
The LAT instrument will be fully integrated but the SC solar arrays will not be installed
The LAT will be powered on and off during testing per the test procedure
The LAT will be oriented with the Z-axis parallel to the ground to allow all heat pipes to
operate and the +X axis facing up
All MLI blanketing will be in its flight configuration for the duration of the 2 tests
The LAT will NOT be reconfigured after the thermal-balance test
Document: LAT-PR-01967
Section 8.C Thermal Design
42
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Thermal Balance/Thermal-Vacuum Tests (cont)
•
•
Instrumentation
– Thermocouples and RTD’s will be used to instrument the LAT and test chamber
– LAT flight housekeeping instrumentation includes many thermistors and RTD’s. These
will also be used for monitoring temperatures within the LAT
Specialized test equipment requirements
– Chamber pressure of < 1 x 10-5 Torr
– Chamber cold wall temperature of –180 oC to provide a cold sink for accumulation of
contaminants
– Thermally controlled surfaces in the chamber
•
•
•
5 plates for ACD surfaces, each individually controlled
2 plates for the radiators(one for each side), each individually controlled
1 plate to simulate the bus, controlling the environment to the X-LAT Plate and the back of each
radiator
–
•
Heat exchangers mounted on the +/– X sides of the LAT Grid, to increase ramp rate
during transitions
– LAT heat pipes will be leveled to within 0.2 degrees
– 20 oC/hr max ramp rate
– Facility capable of holding LAT stable to < 2 oC/hr rate of change (TBR)
Test profile
– Dwell at high and low temps for 12 hours, min
– Comprehensive Performance Tests conducted at select plateaus
•
–
Perform at ambient, during cold and hot soaks, and at return to ambient
Limited Performance Tests during transitions and plateaus
•
Check operating modes and monitor units for problems or intermittent operation
Document: LAT-PR-01967
Section 8.C Thermal Design
43
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Thermal Balance/Thermal-Vacuum Test Profile
Hot QT
Bake Out
CPT
CPT
LPT
LPT
CPT
Hot QT
LAT Off
Hot T- Bal
LAT Off
LAT On
Muon Survey
Warm-up
Repress
Pump-Down
Muon Survey
CPT
CPT
Cold Surv
T-Bal
Cold
QT
Cold T-Bal
1
2
3
4
Muon Survey
LAT On
LPT
LPT
CPT
Cold Start
T-Bal
Ambient Pressure, Temp
T-Vac Cycles
Pressure < 1x 10-5 Torr
LAT Thermal-Vacuum Test Profile
Source: LAT-MD-01600-01, “LAT Thermal-Vacuum Test Plan,” March 2003
Document: LAT-PR-01967
Section 8.C Thermal Design
44
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
LAT Cool Down During TVAC
Document: LAT-PR-01967
Section 8.C Thermal Design
45
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Issues
–The X-LAT Plate to Electronics Box Interface needs better
definition to properly evaluate the conductance across the
interface
•Current conductance assumption is 150 W/m2-deg C or
0.1 W/in2-deg C(poor dry joint)
•High variability of tolerances between X-LAT plate and
electronics boxes could lead to very poor overall joint thermal
performance
Space Grade Gelvet Conductance, Gold Plated Aluminum and BeO
Interfaces
6.0
5.5
Conductance (W/C-in^2)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
0.020" Gelvet Conductance 0 C
Exponential best fit to 0C data
Extrapolation of exponential fit
1.5
1.0
0.5
0.0
0
200
400
600
800
1000
1200
1400
1600
1800
Pressure (psi)
Document: LAT-PR-01967
Section 8.C Thermal Design
46
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Summary
– We are using a fully integrated thermal model for generating
temperature predicts for CDR
– The Radiator thermal design has been changed to incorporate
modifications to the spacecraft interface
– Predicts show that we meet all operating limits, with adequate
margin, when using the IRD solar arrays
• When using the expected “real” Spectrum Astro solar array, net flux to
each radiator drops about 60 watts
• With a “real” solar array, maximum temperatures drop about 5 C
– Predicts show that we meet all operating limits, with adequate
heater margin, when using the Spectrum solar arrays in the cold
and survival cases
Document: LAT-PR-01967
Section 8.C Thermal Design
47
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review, May 12-16 2003
Appendix
Thermal Analysis RFAs
Section 8.C Thermal Design
48
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Peer Review RFAs
Document: LAT-PR-01967
Section 8.C Thermal Design
49
GLAST LAT Project
CDR/CD-3 Review, May 12-16 2003
Peer Review RFAs (Continued)
Document: LAT-PR-01967
Section 8.C Thermal Design
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