LAT-PR Section 44-1 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Mechanical Design Integration Peer Review, March Thermal Systems Analysis Mechanical Design Integration Peer Review, March Thermal Systems Analysis 25 March 2003 Jeff Martin Jeff Martin

LAT-PR Section 44-2 GLAST LAT ProjectMechanical Design Integration Peer Review, March 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

LAT-PR Section 44-3 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 LAT Thermal System Schematic Diagram LAT Thermal Schematic Diagram

LAT-PR Section 44-4 GLAST LAT ProjectMechanical 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

LAT-PR Section 44-5 GLAST LAT ProjectMechanical 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 m 2 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

LAT-PR Section 44-6 GLAST LAT ProjectMechanical 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 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

LAT-PR Section 44-7 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 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

LAT-PR Section 44-8 GLAST LAT ProjectMechanical Design Integration Peer Review, March 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 m 2 –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 –Top Flange Heat Pipes (not shown) Isothermalize grid structure –X-LAT Heat Pipes 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 SurvivalColdHotUnits Earth IR W/m 2 Earth Albedo Solar Flux W/m 2 LAT Process Power W MLI thermal shielding surrounding ACD, Grid Box, Electronics X-LAT Heat Pipes shunt electronics power to Radiators LAT Thermal Overview Active VCHP control allows for variable Radiator area to maintain constant interface temp to LAT Down Spout Heat Pipes connect Grid to Radiators

LAT-PR Section 44-9 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Driving Thermal Design Requirements

LAT-PR Section GLAST LAT ProjectMechanical 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 LAT Dissipated Power Values Source: LAT-TD “A Summary of LAT Dissipated Power for Use in Thermal Design”, 13 Mar 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Thermal Model Details: Electronics Box Dissipated Power Source: LAT-TD “A Summary of LAT Dissipated Power for Use in Thermal Design”, 13 Mar 2003 LAT Dissipated Power Distribution in Special Electronics Boxes

LAT-PR Section GLAST LAT ProjectMechanical 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 SC-LAT Thermal Interface Parameters

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Thermal Model Details: Design Case Details Source: LAT-TD “LAT Thermal Design Parameters Summary”, 19 Mar 2003 LAT Thermal Case Description To Be Reviewed

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Results Summary Temperature Predicts for LAT Subsystems Hot-Case peak temperatures predicts –Tracker Predict: 24 o C max Operating Limit: 30 o C –Calorimeter: Predict: 16 o C max Operating Limit: 25 o C –Electronics Predict: 28 o C max Operating Limit: 45 o C These are “raw predicts” and do not include 5 o C uncertainty

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Temperature Predicts and Margins to Operating Limit Temperature Predicts for LAT Subsystems Temperature predicts show that all subsystem components carry greater than 5 o C margin to their operating limit Minimum margin of 6 o C is for the center TKR module

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 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: 4.0 deg C –Top of Grid—DSHP at VCHP: ~7.6 deg C TKR Maximum Temperature Gradient in the LAT

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Hot Case Environmental Orbit Loads Hot Case Orbit: Beta 0, +Z Zenith, +X Sun Pointing sun Environmental Load on Radiators for Hot-Case Orbit

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March W orbital heating 252 W orbital heating 235 W orbital heating 83.5 W solar array heating 84 W solar array heating 652 W to space 648 W to space 2072 W to space Instrument Power 612 W 24 W from bus 46 W solar array heating Y Z 30 W from bus 3.9 W to space Hot Case QMAP Orbital heating Radiated to space Bus heating VCHP reservoir 64 W orbital heating 91 W to space Hot Case QMAP Hot Operational Orbit Average Qmap 30 W from bus

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Hot Case Temperatures Predicted LAT Temperatures for Hot-Case Orbit

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Hot Case Tracker Temperature Predicted TKR Temperature Showing Analysis Predict is Stabilizing Toward an Aymptote

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Hot Case Radiator Temperatures

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Hot Case with “Real” PDR Solar Arrays

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Survival Case Orbit sun Survival Orientation: +X Sun Pointing Environmental Load on Radiators for Survival-Case Orbit

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Survival Case QMAP 1529 W orbital heating 130 W orbital heating 39 W solar array heating 258 W to space 1569 W to space Make-up Heaters 61W W solar array heating W to space W to space 44 W orbital heating 22 W heater power Survival Case QMAP Y Z Survival Orbit Average Qmap Orbital heating Radiated to space Bus heating VCHP reservoir Anti-freeze heaters VCHP reservoir heaters 131 W orbital heating 38 W solar array heating 259 W to space 10.0 W to space 23 W heater power

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Survival Temperatures

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Survival Case Temperatures Predicted LAT Temperatures for Survival-Case Orbit

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Survival Case Radiator Temperatures Predicted Radiator Temperatures for Survival-Case Orbit

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Survival Heater Power Survival heater power (orbit average) Grid make-up heaters61 W VCHP anti-freeze heaters91 W X-LAT Plate heaters0 W Total heater power152 W Allocation:220 Watts Heater power margin:+68 W (45% margin)

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 VCHP Reservoir Heater Power Reservoir Heater Size –3.5 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)

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Cold Case Temperatures Predicted Temperatures for Cold-Case Orbit

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Cold Case Radiator Temperatures Predicted Radiator Temperatures for Cold-Case Orbit

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 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 –In-chamber cool-down transient analysis

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 LAT Thermal Hot Case Analyses Summary of Hot-Case Failure Analyses

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 LAT Thermal Cold/Survival Case Analyses Summary of Cold-/Survival-Case Failure Analyses

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 LAT Thermal Systems Components Passive thermal hardware –Radiators and X-LAT Plates Provided by: Mechanical Systems, LM Transport and reject heat from LAT –Grid Base Assembly Provided by: Mechanical Systems, SLAC Heat pipes from LM Transport heat from LAT interior to Radiators Actively-controlled hardware –Radiator VCHP’s Provided by: Mechanical Systems, LM Heaters on reservoirs are the active feedback mechanism –Radiator anti-freeze heaters Provided by: Mechanical Systems, LM Thermostatically-controlled to assure that VCHP’s do not freeze when LAT is in survival mode –Grid Make-up heaters Provided by: Mechanical Systems, SLAC Thermostatically-controlled to make-up heat leak during survival LAT Thermal System Components Radiators Grid Base Assembly X-LAT Plates

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 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 look- up table Logic and constants can be modified by IOC upload –Power Distribution Unit (PDU) Provided by: Electronics/DAQ, SLAC Handles conversion of all thermistor, current, and voltage signals –Heater Switch Box Provided by: Electronics/DAQ, SLAC Contains FET switches for individual control of VCHP heaters Receive switching control signals from SIU TCS Architecture Source: LAT-SS , “LAT Thermal Control System Performance Specification,” 23 March 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 TCS Operating Modes TCS Operating Modes and Transitions 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 Source: LAT-SS , “LAT Thermal Control System Performance Specification,” 23 March 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 LAT Power Up LAT and TCS Early Orbit Power-Up Source: LAT-SS , “LAT Thermal Control System Performance Specification,” 23 March 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Thermal Control System N 2 Chart TCS Mode Transition Logic Chart Source: LAT-SS , “LAT Thermal Control System Performance Specification,” 23 March 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 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 –Develop thermal vacuum test model Chamber and STE configuration is defined in concept (LAT is using NRL T-Vac chamber) –Finalize control logic algorithms –Finalize TCS functionality requirements that flow to FSW