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					GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003

Mechanical Design Integration Peer Review, March 2003

4. Thermal Systems Analysis

Jeff Wang Martin Nordby

jeff.wang@lmco.com nordby@slac.stanford.edu
25 March 2003

LAT-PR-01278 Section 4

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GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003

4. LAT Thermal Systems Analysis
• Introduction – Thermal block diagram – LAT internal design changes since Delta PDR – Interface design changes since Delta PDR 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

• • •

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Mechanical Design Integration Peer Review, March 2003

LAT Thermal System Schematic Diagram
Thermal Accommodation
Direction of arrow signifies direction of heat flow

ACD

TKR

Grid Base Ass’y Rad Mnt Bkt
EMI Skirt

CAL
EMI Skirt

Rad Mnt Bkt Htr Sw Box
Radiator

Htr Sw Box
Radiator

Electronics X-LAT Plate

Solar Array

Spacecraft

Solar Array

LV Payload Attach Fitting

LAT Thermal Schematic Diagram
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GLAST LAT Project

Mechanical Design Integration Peer Review, March 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 612 W (was 602W) – Total is still within the 650 W allocation
• • • CAL and TKR power increased 26 W Electronics power dropped 18 W ACD power increased 3 W

•

•

•

•

– 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
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LAT-PR-01278 Section 4

GLAST LAT Project

Mechanical Design Integration Peer Review, March 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

•

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Mechanical Design Integration Peer Review, March 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 survivalcase 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

•

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Current State of Thermal Model
• Subsystem models have been refined – Updated TKR model to reflect CDR design – Incorporated ACD model from GSFC to reflect CDR design – Incorporated Reduced CAL model from NRL to reflect CDR design – Modified Radiator model to reflect design changes made since Delta PDR Solar Array interface has been updated – Hot-case array is still per LAT IRD – Cold-/survival-case array uses Spectrum PDR design Still uses Delta-PDR electronics and X-LAT model – CDR model is under development and will be incorporated into the LAT thermal model after this review SC Bus MLI closeout interface definition is unchanged since Delta-PDR Incorporated heat pipe logic to calculate gas front Added VCHP heater control logic – Logic will be part of SIU control of thermal system

•

•

• • •

Model status: the model is thermal mature, and interfaces understood. The electronics thermal model is the one deficiency, and is being worked now in preparation for CDR analysis

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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 Remove waste heat from electronics Connect radiators for load-sharing Transport waste heat from grid to Radiators
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 Down Spout Heat Pipes connect Grid to Radiators MLI thermal shielding surrounding ACD, Grid Box, Electronics

•

•

–
–

Top Flange Heat Pipes (not shown)
• • •

X-LAT Heat Pipes

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Downspout Heat Pipes
•
On-Orbit Thermal Environment and LAT Process Power Earth IR Earth Albedo Solar Flux LAT Process Power

LAT Thermal Overview
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GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003

Driving Thermal Design Requirements
Parameter Max Radiator area (#) Max process power indefinite dissipation Peak process power dissipated for 10 min (#) Min process power indefinite dissipation 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 Stability of LAT Control Temp point (3) VCHP heater power when LAT is on (at Vmin) VCHP heater power when LAT is off (at Vmin) When off, orbit-average survival heater power at 27 V min (not incl control auth margin) When off, peak survival heater power During Obs t-vac, TCS capable of full functionality "lying on its side"
(1): Total Power = Process Power + VCHP Reservoir Heater Power = 612 + 38 = 650W (2): Margin on heater power keeps minimum LAT temperature above AT limits (3): LCT defined as the Grid side of the Grid--DSHP interface point
LAT-PR-01278 Section 4 4-9

Requirement < 5.88 m2 612 W @ T(max) 720 W for 10 min @ T(max) 497 W @ T(min) 75 W/Rad 450 - 575 km

Design 5.57 m2 612 W LAT + 38 W Rad @ 24 C 720 W for 20 min @ <T(max) 497 W @ -10 C 73.4 W 450 km hot-case 575 km cold-case OK OK

Margin 0.31 m2 5 C calc + 1 C Operating 10 min, 7 C 50% Rad control auth. 0 W/Rad OK

Comply Y Y Y Y Y Y Y Y

Ver. Method I T, A T, A T, A T, A A T, A A T, A T, A D D D D T, A

+30 C / -15 C +/- 3 C < 38 W < 50 W < 220 W < 560 W

+24 C / -3 C < +/- 3 C 13 W @ 27 V 42 W @ 27 V 152 W 387 W (incl 30% control auth) OK

+ 6 C / 12 C 25 W 8W 68 W 173 W (45%)

Y Y Y Y Y Y Y

GLAST LAT Project

Mechanical Design Integration Peer Review, March 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

Special Status Normal Operations Tran- Cold Hot 10 Min Surv. Alloc. Unit sition Case Case Peak Total 50.0 95.3 534.8 590.0 650.0 719.8 W Total on Grid 0.0 0.0 210.6 234.0 252.1 291.2 W TKR 139.5 155.0 162.8 192.9 W CAL 60.3 67.0 75.8 83.4 W ACD 10.8 12.0 13.6 14.9 W Total on X-LAT 0.0 45.3 286.2 318.0 359.9 390.5 W TEM 43.2 48.0 54.3 58.1 W TPS 148.5 165.0 186.7 203.2 W GASU 19.8 22.0 24.9 27.8 W SIU 27.2 21.6 24.0 27.2 29.7 W EPU 38.7 43.0 48.7 53.0 W PDU 18.1 14.4 16.0 18.1 18.6 W Radiators 50.0 50.0 38.0 38.0 38.0 38.0 W

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-00225-04 “A Summary of LAT Dissipated Power for Use in Thermal Design”, 13 Mar 2003

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Mechanical Design Integration Peer Review, March 2003

Thermal Model Details: Electronics Box Dissipated Power
Cold Case Power Dissipation
LAT +Y +Y Side LAT Radiator Bay 12 EPU-B 0 Bay 8 PDU-B 0 -X Side Bay 4 PDU-A 14.4 Bay 0 EPU-A 19.4 Boxes TEM/TPS: X-LAT Tot Legend: GASU SIU PDU EPU -A -B 94.5 191.7 286.2 Bay 1 Empty 0 Bay 5 GASU Bay 13 Empty 0 Bay 9 GASU Bay 14 Empty 0 Bay 10 GASU 9.9 Bay 6 GASU 9.9 Bay 2 Empty 0 Bay 15 Empty 0 Bay 11 SIU-B 0 Bay 7 SIU-A 21.6 Bay 3 EPU-A 19.4 Boxes TEM/TPS: X-LAT Tot LAT +X +X Side Sun Side -X Side Bay 12 EPU-B 0 Bay 8 PDU-B 0 Bay 4 PDU-A 18.11 Bay 0 EPU-A 24.3 118.8 241.0 359.9

Hot Case Power Dissipation
LAT +Y +Y Side LAT Radiator Bay 13 Empty 0 Bay 9 GASU 0 Bay 5 GASU 0 Bay 1 Empty 0 Bay 14 Empty 0 Bay 10 GASU 12.4 Bay 6 GASU 12.4 Bay 2 Empty 0 Bay 15 Empty 0 Bay 11 SIU-B 0 Bay 7 SIU-A 27.2 Bay 3 EPU-A 24.3 LAT +X +X Side Sun Side

-Y Side LAT Radiator LAT Top View

-Y Side LAT Radiator LAT Top View

Global trigger, ACD, and Switching Unit Spacecraft Interface Unit Power Distribution Box LAT Event Processor A-side, powered box B-side, unpowered cold spare

Notes: 1. All power is in watts

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

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Mechanical Design Integration Peer Review, March 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 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

Hot 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

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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) Nominal 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 Hot 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 Rocking 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 Maximum Fully open/0 hot-case Hot Real SA Transition Re-Point [6] Change from Pointed[2] to Pointed[4] 450 0 28.5 0.01 265 0.4 1419 27 6 Unit

km deg deg --W/m2 W/m2 W W/m2

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)

Survival Minimum Maximum Maximum 100% closed/100% TBD% closed/<60% Fully open/0 Fully open/0 cold-case cold-case hot-case hot-case Survival SA Cold SA Hot Real SA Design Hot 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, panels with 1" gaps panels with 1" gaps 3 panels with 1" 3 panels with 1" gaps gaps 1.3 1.3 1.3 0.52 0.127 0.127 0.127 0.0254 0.92 0.92 0.92 0.9 26% 26% 17% NA 0.68 0.68 0.75 0.9 0.86 0.86 0.84 0.85 0.18 0.18 0.4 0.5 0.91 0.91 0.87 0.88 0.39 0.39 0.45 0.8 0.75 0.75 0.72 0.9 56.2 56.2 56.2 74.3 6135 6135 6135 4665

Maximum Fully open/0 hot-case Hot Real SA

m m^2 %

W/K J/K

LAT Thermal Case Description
Source: LAT-TD-00224-04 “LAT Thermal Design Parameters Summary”, 19 Mar 2003

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Results Summary
• Hot-Case peak temperatures predicts – Tracker
• • Predict: 24 oC max Operating Limit: 30 oC Predict: 16 oC max Operating Limit: 25 oC Predict: 28 oC max Operating Limit: 45 oC

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Calorimeter:
• •

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Electronics
• •

•

These are “raw predicts” and do not include 5 oC uncertainty
Component TKR CAL TEM TPS EPU SIU PDU GASU ACD, BEA TSA
Notes:

Survival Min Max -23.8 -17.1 -18.9 -17.8 -19.7 -19.1 -19.7 -19.1 -19.7 -19.1 -19.2 -19.1 -19.2 -19.1 -19.7 -19.5 -19.1 -16.2 -25.6 -13.3

Cold Ops Min Max -2.8 9.2 0.8 3.1 4.9 12.4 4.7 12.4 0.0 4.9 2.4 10.2 2.3 7.6 8.8 9.0 3.0 3.8 -5.5 -1.9

Hot Design Min Max 13.3 24.0 12.4 15.8 17.6 27.8 17.2 27.7 0.0 17.5 12.9 24.1 12.6 20.8 21.2 22.0 14.8 18.0 15.1 20.2

All temperatures are in degrees C Temperatures are raw predicts

Temperature Predicts for LAT Subsystems
LAT-PR-01278 Section 4 4-14

GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003

Temperature Predicts and Margins to Operating Limit
• • Temperature predicts show that all subsystem components carry greater than 5 oC margin to their operating limit Minimum margin of 6 oC is for the center TKR module

Survival Cold Ops Hot Design Component Predict Limit Margin Predict Limit Margin Predict Limit Margin Tracker -23.8 -30.0 6.2 -2.8 -15.0 12.2 24.0 30.0 6.0 Calorimeter -18.9 -30.0 11.1 0.8 -15.0 15.8 15.8 25.0 9.2 TEM* -19.7 -40.0 20.3 4.9 -30.0 34.9 27.8 45.0 17.2 TPS* -19.7 -40.0 20.3 4.7 -30.0 34.7 27.7 45.0 17.3 EPU* -19.7 -40.0 20.3 0.0 -30.0 30.0 17.5 45.0 27.5 SIU* -19.2 -40.0 20.9 2.4 -30.0 32.4 24.1 45.0 20.9 PDU* -19.2 -40.0 20.8 2.3 -30.0 32.3 20.8 45.0 24.2 GASU* -19.7 -40.0 20.3 8.8 -15.0 23.8 22.0 45.0 23.0 ACD, BEA -19.1 -40.0 20.9 3.0 -15.0 18.0 18.0 30.0 12.0 TSA -25.6 -50.0 24.4 -5.5 -30.0 24.5 25.0 35.0 10.0
All temperatures are in degrees C Temperatures shown are for the hottest/coldest extremity of the subsytem, except as indicated Temperature predicts do not include 5 C analysis uncertainty margin (*) Temperatures shown are for the box interface to its heat sink

Temperature Predicts for LAT Subsystems

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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: 4.0 deg C – Top of Grid—DSHP at VCHP: ~7.6 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) 17.60 23.00 24.00 18.80 18.30 14.30 -Y Rad +Y Rad 6.80 6.50 5.10 4.80 -3.30 -4.10 27.30 28.10

DSHP-4 top row, Rad DSHP-4, at VCHP Top of Radiator by VCHP4 Maximum temp gradient

TKR Maximum Temperature Gradient in the LAT

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Mechanical Design Integration Peer Review, March 2003

Hot Case Environmental Orbit Loads
Hot Case Orbit: Beta 0, +Z Zenith, +X Sun Pointing

sun

600
Solar Constant =1419 W/m 2

500

Planet Power=265W/m 2 Albedo=0.4

Absorbed Flux (W)

400 300 200 100 0
Total-Rad1 Total-Rad2

LAT-PR-01278 Section 4

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
Time(seconds)

Environmental Load on Radiators for Hot-Case Orbit
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Hot Case QMAP

2072 W to space

Instrument Power 612 W

2008 W orbital heating

46 W solar array heating 91 W to space 252 W orbital heating 83.5 W solar array heating 30 W from bus 652 W to space 3.9 W to space Z 30 W from bus 24 W from bus

64 W orbital heating 235 W orbital heating

84 W solar array heating

648 W to space 3.9 W to space Orbital heating Radiated to space Bus heating Bus heating VCHP reservoir

Y

Hot Operational Orbit Average Qmap

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Hot Case Temperatures

Predicted LAT Temperatures for Hot-Case Orbit
LAT-PR-01278 Section 4 4-19

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Hot Case Tracker Temperature

Predicted TKR Temperature Showing Analysis Predict is Stabilizing Toward an Aymptote
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Hot Case Radiator Temperatures

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Hot Case with “Real” PDR Solar Arrays

LAT-PR-01278 Section 4

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Survival Case Orbit
Survival Orientation: +X Sun Pointing

sun
160 140 120
Absorbed Flux(W)

100 80 60 40 20 0 0 960 1816 1920 2880 3841 Time(seconds) 3945 4801 5761
Solar Constant =1286 W/m 2 Planet Power = 208 W/m 2 Albedo = 0.25

Total-Rad1 Total-Rad2

Environmental Load on Radiators for Survival-Case Orbit
LAT-PR-01278 Section 4 4-23

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Mechanical Design Integration Peer Review, March 2003

Survival Case QMAP

1569 W to space

Make-up Heaters 61W

1529 W orbital heating

22 W solar array heating 44 W orbital heating 63 W to space 13 12 39 W solar array heating 45.5 258 W to space Z 9.9 W to space 22 W heater power Y Survival Orbit Average Qmap 45.5 12 38 W solar array heating 131 W orbital heating

130 W orbital heating

259 W to space 10.0 W to space Orbital heating Radiated to space Bus heating Bus heating VCHP reservoir Anti-freeze heaters VCHP reservoir heaters
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23 W heater power

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Survival Temperatures

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Survival Case Temperatures

Predicted LAT Temperatures for Survival-Case Orbit
LAT-PR-01278 Section 4 4-26

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Survival Case Radiator Temperatures

Predicted Radiator Temperatures for Survival-Case Orbit
LAT-PR-01278 Section 4 4-27

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Mechanical Design Integration Peer Review, March 2003

Survival Heater Power
• Survival heater power (orbit average) • Grid make-up heaters 61 W • VCHP anti-freeze heaters 91 W • X-LAT Plate heaters 0W • Total heater power 152 W Allocation: Heater power margin: 220 Watts +68 W (45% margin)

• •

Parameter When off, orbit-average survival heater power at 27 V min (not incl control auth margin) When off, peak survival heater power Control margin on heater power

Requirement < 220 W < 560 W > 30%

Design 152 W 387 W @ 35 V (incl 30% control auth) 88%

Margin 68 W (45%) 173 W (45%) 55%

Comply Y Y Y

Ver. Method D D D

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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 on (at Vmin) VCHP heater power when off (at Vmin) Control margin on heater power

Requirement < 38 W < 50 W > 30%

Design 13 W @ 27 V

Margin Comply 25 W Y Y Y

42 W @ 27 V 8 W 200% 170%

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Cold Case Temperatures

Predicted Temperatures for Cold-Case Orbit
LAT-PR-01278 Section 4 4-30

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Cold Case Radiator Temperatures

Predicted Radiator Temperatures for Cold-Case Orbit
LAT-PR-01278 Section 4 4-31

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Summary of LAT Thermal Analysis Cases
• Design cases – High Power, EOL Case(Hot) – No Power, BOL Survival(Cold) Other on-orbit cases of significance – Cold-Case – Sky-survey – Alternate Beta-angles – Extra Solar – Re-pointing transient analysis – Survival cool-down transient analysis – Early-orbit turn-on survival analysis – Failure Analyses Ground cases – In-chamber hot-/cold-cases
• • TCS Protoflight test LAT thermal-vacuum/thermal-balance test

•

•

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In-chamber cool-down transient analysis

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LAT Thermal Hot Case Analyses
Case Orbit Solar Array # Parameters 1 Hot Case Design Hot 2 Hot Case Real Hot 3 Hot Case Design Hot 4 Hot Case Design Hot 5 Hot Case Design Hot 6 Nominal Design Hot 7 Rocking Design Hot 8 Transition Design Hot 9 Hot Case Design Hot 10 Hot Case Design Hot 11 Hot Case Design Hot 12 Hot Case Design Hot 13 Hot Case Design Hot 14 Hot Case Design Hot 15 Hot Case Design Hot 16 Hot Case Design Hot 17 Hot Case Design Hot 18 19 20 Hot Case Hot Case Hot Case Design Hot Design Hot Design Hot Radiator Temp 0 o C Set 0 o C Set Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated NCG 5 yr 5 yr 5 yr 5 yr 10 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr 5 yr Heat Pipe Failure None None None None None None None None VCHP # 2 VCHP # 0 XLAT # 2 XLAT # 0 DSHP #2 DSHP #0 Grid HP # 2 Grid HP # 3 Grid HP # 0 None None None Heater Failure None None None None None None None None 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 None None None None None None None None TKR-grid conduction lost (1 Bay)

Summary of Hot-Case Failure Analyses
LAT-PR-01278 Section 4 4-33

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LAT Thermal Cold/Survival Case Analyses

Case # 1 2 3 4 5 6

Orbit Parameters Cold Case Cold Case Survival Case Survival Case Survival Case Survival Case

Solar Array Real Cold Real Cold Real Cold Real Cold Real Cold Real Cold

Radiator Temp Calculated Calculated Calculated Calculated Calculated Calculated

NCG None None None None None None

Heat Pipe Failure None None None None None None

Heater Failure None 1 VCHP Reservoir None 1 VCHP Reservoir Heater Open 1Grid Heater Open Pri & BU VCHP Reservoir Heaters on

Summary of Cold-/Survival-Case Failure Analyses

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LAT Thermal Systems Components
• Passive thermal hardware – Radiators and X-LAT Plates
• • Provided by: Mechanical Systems, LM Transport and reject heat from LAT Provided by: Mechanical Systems, SLAC Heat pipes from LM Transport heat from LAT interior to Radiators

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Grid Base Assembly
• • •

•

Actively-controlled hardware – Radiator VCHP’s
• • Provided by: Mechanical Systems, LM Heaters on reservoirs are the active feedback mechanism Provided by: Mechanical Systems, LM Thermostatically-controlled to assure that VCHP’s do not freeze when LAT is in survival mode Provided by: Mechanical Systems, SLAC Thermostatically-controlled to make-up heat leak during survival
Radiators

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Radiator anti-freeze heaters
• •

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Grid Make-up heaters
• •
X-LAT Plates Grid Base Assembly

LAT Thermal System Components
LAT-PR-01278 Section 4 4-35

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Thermal Control System Design
• TCS control hardware – LAT Spacecraft Interface Unit (SIU)
• • • • • • Provided by: Electronics/DAQ, SLAC Provides control function for TCS Control logic part of flight software Alarms and management of LAT and TCS state changes communicated to SC Thermal constants managed in a lookup table Logic and constants can be modified by IOC upload Provided by: Electronics/DAQ, SLAC Handles conversion of all thermistor, current, and voltage signals Provided by: Electronics/DAQ, SLAC Contains FET switches for individual control of VCHP heaters Receive switching control signals from SIU
+Y Radiator
VCHP htr's (6 zones) T Anti-freeze htr’s (2 zones) T

HSB

T

T

Grid

SC PRU VCHP Feed Surv Feed

PDU Thermistors

SIU Watch-dog VCHP control

SC C&DH Thermal sensors

–

Power Distribution Unit (PDU)
• •
T

Temp monitors Heaters Thermal switch

HSB
T T

HSB: Heater Switch Box
+Y

–

Heater Switch Box
• • •

Anti-freeze htr’s (2 zones) T

-Y Radiator

+X

T VCHP htr's (6 zones)

TCS Architecture

Source: LAT-SS-00715-01, “LAT Thermal Control System Performance Specification ,” 23 March 2003

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TCS Operating Modes
• Off – LAT is off and all feeds are un-powered (during launch and transportation) Pre-Deploy – Immediately after fairing separation, the VCHP feed is powered to activate the VCHP heaters – This is TBD until early-orbit timeline is finalized with Spectrum Survival – After solar array deployment, the survival feed is powered and Grid make-up Radiator anti-freeze heaters are energized – TCS is in “Survival” whenever LAT enters “survival” mode TCS Safe – SIU/PDU are thermally in control of the LAT Transition – TCS is functioning fully, except that LAT temperatures may be out of operating range – LAT is powering up or warming up Nominal – All temperatures and rates of change are within nominal operating range
LAT-PR-01278 Section 4

•

Nominal
SIU watch-dog time-out (A) SC power bus low voltage (A)

Temp warning (A) Temp alarm (A)

TCS survival alarm (A,C) SC emergency (A,C)

LAT temp's in range (C)

Transition

•

TCS in control (C) SIU turned on (C)

TCS Safe

Survival
Surv bus power on (C) (A) = Autonomous function/transition (C) = Commanded function/transition

Pre-Deploy
Launch (C) Fairing separation (C)

• •

Off

TCS Operating Modes and Transitions

•

Source: LAT-SS-00715-01, “LAT Thermal Control System Performance Specification ,” 23 March 2003

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LAT Power Up
Obs.
Launch and Ascent Early Orbit Standby/Engineering Engineering Sky Survey

Operating Modes

LAT

Off

Pre-deploy

LAT Survival

LAT Hardware Safe

T&DF On

Detectors On

Standby

Observing

Thermal

Off

Pre-deploy

Survival

TCS Safe

Transition

Nominal

<TBD min
Temperature (oC)
40 30 Launch Fairing Separation 20 10 0 Fairing Sep + TBD min -10 -20 Solar Array -30 Deploy

Indefinite
LAT Boot Up
40 30 20 10 0 -10 -20 -30 40 30 20 10 0 -10 -20 -30

Initiate LAT Turn-on

Detectors on

Orbit-Average Power Draw (W)

700 600 500 400 300 200 100 0

0W

50W

270W

320W

560W

650W

650W
700 600 500 400 300 200 100 0

Pwr Bus

VCHP Surv LAT Tot

VCHP Surv LAT Tot

VCHP Surv LAT Tot

VCHP Surv LAT Tot

VCHP Surv LAT Tot

VCHP Surv LAT Tot

VCHP Surv LAT Tot

Status

VCHP Surv SIU PDU GASU

TEM CAL TKR ACD EPU

VCHP Surv SIU PDU GASU

TEM CAL TKR ACD EPU

VCHP Surv SIU PDU GASU

TEM CAL TKR ACD EPU

VCHP Surv SIU PDU GASU

TEM CAL TKR ACD EPU

VCHP Surv SIU PDU GASU

TEM CAL TKR ACD EPU

VCHP Surv SIU PDU GASU

TEM CAL TKR ACD EPU

VCHP Surv SIU PDU GASU

TEM CAL TKR ACD EPU

VCHP = VCHP Htr. Bus Surv = Survival Htr. Bus

LAT= LAT Main Power Bus Tot = LAT Total Power

Off On

Transition

Source: LAT-SS-00715-01, “LAT Thermal Control System Performance Specification ,” 23 March 2003

LAT and TCS Early Orbit Power-Up
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Thermal Control System N2 Chart
Cause: SC powers VCHP bus at Launch + TBD Action: Turn on VCHP surv htrs Pre-Deploy Cause: SC S.A.'s deploy, powers Surv bus Action: Thermostats activate LAT make-up htrs Cause: SC out of safe mode, powers LAT main bus. MOC commands LAT to turn on. Action: SIU/PDU turn on, get temps; SIU opens watch-dog switch, takes control of VCHP's TCS Safe Cause: temp’s reach surv limit Action: TCS closes Radiators 100%, turns off DAQ, FEE, drops to TCS Safe, sends signal to SC Cause: MOC OK's LAT for turn-on Action: TCS OK's turn on of EPU’s, TEM’s, TPS’ to SIU Transition Cause: temps/rates out of nominal range; TCS receives alert from SIU due to out-ofrange HSK temp or SC alert Action: TCS drops to Transition, sends signal to SC Cause: make-up htr's off; temps/rates nominal Action: TCS sends OK to IOC for Observing Mode

Off

Cause: SC powers down VCHP bus Action: none

Cause: SC lowvoltage, powers down survival feeds Action: No LAT action

Survival

Cause: temp’s exceed surv limit Action: TCS sends alarm to SC, puts LAT in safe mode.

Same as below

Cause: SIU, PDU hang. SC pulls Cause: SC bus voltage low or LAT plug. Loss of signal. TCS htrs out-of- receives load-shed notice from SC range Action: TCS closes Radiators 100%, Action: Watch-dog switch closes drops to TCS Safe, sends signal to VCHP htrs SC

Nominal

TCS Mode Transition Logic Chart

Source: LAT-SS-00715-01, “LAT Thermal Control System Performance Specification ,” 23 March 2003

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Summary and Further Work
• Summary – We are working towards completing and using a fully integrated thermal model of the CDR design 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 Further Work – Complete incorporation of updated electronics thermal model into – Complete all failure cases for CDR – Complete sensitivity analyses for CDR – Complete launch and deployment scenarios
• Currently working with Spectrum to define deployed solar array configuration and launch and early orbit timeline Chamber and STE configuration is defined in concept (LAT is using NRL T-Vac chamber)

•

– – –

Develop thermal vacuum test model
•

Finalize control logic algorithms Finalize TCS functionality requirements that flow to FSW

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