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Thermal Design. Christopher Smith RBSP Thermal Engineer Space Sciences Lab University of California, Berkeley. Outline. Requirements APL – UCB Interface Thermal Model Description IDPU Board Level Thermal Analysis Thermal Model Case Set Inputs Current Predicts Current Testing Overview.
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Thermal Design Christopher Smith RBSP Thermal Engineer Space Sciences Lab University of California, Berkeley
Outline • Requirements • APL – UCB Interface • Thermal Model Description • IDPU Board Level Thermal Analysis • Thermal Model Case Set Inputs • Current Predicts • Current Testing Overview
Spacecraft Level Thermal Requirements • Orbit: 500-675 km x 30,050 - 31,250 km (EFW-7, EFW-8) • Inclination: 10 degrees +/- 0.25 (EFW-6) • 2 year design life, plus 60 days (EFW-1) • Spacecraft top deck pointed to sun within: 25 degrees N/S and E/W, normal operation (EFW-201) 27 degrees composite, normal operation (EFW-202) 33 degrees, Safe mode (SCRD 3.10.4.4) (Was 47) • S/C spin rate (about top deck): 4 to 6 RPM, normal and safe modes (EFW-9) 3 to 15 RPM, instrument commissioning (EFW-203) • S/C shall survive 112 minute eclipse (Derived EFW-6, EFW-7, EFW-8)
EFW Thermal Requirements • Conductive external surfaces with 105 Ohms/Sq. (EFW-133) • Contamination: 100,000 class (EFW-132) • Instruments to operate within specification with -25 to +55 spacecraft boundary conditions. (EFW-76, EFW-77) • -25 to +70 for top deck interface, new since PDR • Instruments to survive without damage with -30 to +60 spacecraft boundary conditions. (EFW-79, EFW-80) • -30 to +75 for top deck interface, new since PDR • Comply with contamination control plan. APL document 7417-9007. (EFW-132) • Comply with Environmental Design and Test Requirements Document. APL document 7417-9019. (EFW-136) • Comply with RBSP_EFW_SYS_301_ETM, RBSP engineering test matrix
Engineering Test Matrix • 7 total cycles per instrument, 5 at component level, 2 at suite level. • Pre-Amps cycled separately due to larger temperature swing. • No need for thermal balance as all instruments are conductively coupled to the spacecraft.
APL Thermal Modeling Interface • Berkeley maintains a Thermal Desktop model of the EFW instrument and a boundary node definition of the spacecraft. • APL Maintains a TSS geometry and SINDA network model of the spacecraft. • APL integrates Berkeley geometry via Thermal Desktop TSS export. • Provides environmental heat flux data to instruments. • APL integrates Berkeley SINDA network model into the SINDA spacecraft network model. • APL specifies spacecraft connection nodes. • APL runs integrated model and provides temperature predicts back to Berkeley. • Design cycles as necessary. • APL is responsible for producing high fidelity temperature predicts.
Thermal Model OverviewInstruments and Boundary Spacecraft IDPU AXBs SPBs
Thermal Model OverviewAXB -Stowed Sphere / Preamp in Caging Mechanism (Clear Alodine, GeBK Blanket) Sphere / Preamp (DAG 213) Rod to Stacer Hinge (DAG 213) Mounting Tube (M55J) Stacer (Elgiloy)
Thermal Model OverviewAXB -Deployed Stacer (Elgiloy) Sphere (DAG 213) DAD (AntiSun: Clear Alodine) (Sun: Clear Alodine / GeBk Tape mix) Sphere Caging Mechanism (AntiSun: Clear Alodine) (Sun: GeBk Blanket / Clear Alodine mix)
Thermal Model OverviewSPB Deployed Elements SPB Sphere SPB Preamp Thick Wire Thin Wire
Thermal Model OverviewSPB & IDPU SPB - Deployed IDPU (Mostly Black Kapton XC Tape, Some Gold Alodine) (Black Kapton XC Tape) (Clear Alodine) SPB - Stowed (Black Kapton Blanket, Shown in Green)
Optical Materials • Most properties tested, used, and correlated for the THEMIS mission • Properties approved by the GSFC coatings committee July 07, 2008.
Thermophysical Properties • Hot Cases Use Low e* Anti-Sunward and High e* Sunward • Cold Cases Use High e* Anti-Sunward and Low e* Sunward
Interfaces IDPU • Conductively mounted to spacecraft side panel. • 9 #10 Bolts = 0.75 W/C each. • Radiative coupling to spacecraft interior, Black Kapton XCTape SPB • Conductively mounted to spacecraft side panel. • 4 #10 Bolts = 0.75 W/C each. • Deployed elements are completely isolated from the spacecraft by wire. • Low radiative coupling to spacecraft interior, Clear Alodined Aluminum AXB • Conductively mounted to the top and bottom spacecraft deck. • 6 #8 Bolts at each end = 0.75 W/C each. • Radiative coupling somewhat isolated from major portions of the spacecraft since the mechanical units are stowed inside a carbon fiber tube which is also stored inside a spacecraft carbon fiber tube. • Deployed elements are isolated from spacecraft influence by stacer. • Caging mechanisms conductively mounted to top deck, 4 #8 Bolts = 0.75 W/C each.
Power, Heaters • Current power used in model • IDPU, SPB and AXB do not have any survival heaters
General Case Sets APL Case Set Parameters UCB Case Set Parameters
Limit Categories • Science Operation Limit • Limits placed on an operating instrument • Specifies the range of temperatures the instrument will provide calibrated / useful science data • Operation – Out of Spec • Limits placed on an operating instrument • May represent a wider range that is survivable but may be out of spec • Temperatures beyond Science Op Limit need not be calibrated to • Non-Operation • Limits placed on a non operating instrument • Pre-Deployment Limit • Limits placed on a mechanical system before it is actuated • Deployment Limit • Limits placed on a mechanical system at the time of actuation • Post-Deployment Limit • Limits placed on a mechanical system after it has executed its one-time deployment
APL and UCB Predict Comparison, Table • Each case set compared at a specific time and a representative node • All case sets agree to within 1.5 degrees
Environmental Testing • AXB Cage – Whip: • ETU qualified to values above (from Environmental Design & Test Requirements Document, dated 07/05/09). • Project Thermal has requested an increase in the Survival (Non-Op) and Op High temperatures to 75 C and 70 C, respectively (5-deg increase). • Current AXB Cage-Whip interface temp predict: 53 C.
