Overview and Mechanical/Thermal IFs to FPU

1. Overview and Mechanical/Thermal IFs to FPU PACS IHDR MPE J. Schubert Overview and Mechanical/Thermal IFs to FPU

2. Content • Overview QM FPU, Status and Problem Areas • Status PACS Mechanical I/F to S/C • Status PACS Thermal I/F to S/C • Allowed Mechanical Loads to Ge:Ga Detector I/Fs • Design and Changes on Cooler L0 I/Fs • Allowed Mechanical Loads to Level 0 Cooler I/Fs • Temperatures of LO I/F to HERSCHEL S/C • In Orbit • On Ground (IMT, and EQM) Overview and Mechanical/Thermal IFs to FPU

3. Overview PACS FPU • FPU QM structural parts manufacturing and assembly completed • Housing compartments blackened with KT 70 • Top Optic mirrors integration and alignment started • Thermal and Load/Structural Analysis finalized • Mechanical, Thermal and Electrical I/Fs to the S/C and to Subunits frozen • Warm and Cryo Vibration performed on STM structure with success • Subunits delivered (Chopper) or within the end of the AIV phase • Extremely tight schedule increases risk for all parties and possibly shifts problem to the FM Overview and Mechanical/Thermal IFs to FPU

4. Overview (cont.) • Open issues to be worked on • Distribution board  qualification/testing of PCB board not finalised, delaminating problem observed, investigation ongoing • Mirrors Gold layer on 3 of 13 mirror batches did not pass the tape test, investigation ongoing • Detector Array Delta cold vibration tests to be performed on Detector Array Components • PhFPU Bolometer Kevlar suspension failed during cold vibration in STM FPU, cold delta vibration test in preparation • PhFPU I/F to S/C  a) mechanical load from S/C cooling is critical, b) not enough clearance between back shells of S/C harness and PhFPU connector panel (TBC) Overview and Mechanical/Thermal IFs to FPU

5. PACS Mechanical I/F to S/C • PACS FPU ICD Drawing Issue 27 DRAFT distributed to ESA & Industry for comment, 04-July-03 • Major design changes compared to issue 25 reworked+implemented • Level 0 S/C IF to Ge:Ga detectors, pin to flat I/F (compliant to IID-A) • Mechanical I/F to OB, pin diameter & position (compliant to IID-A) • Further detailed information added • Cold/Warm configuration, Mounting & Handling Equipment and Non Flight Items etc., drawing split into ten separate drawings • Final release after working in ASTRIUM comments (received 9-Oct-03) • PACS QM manufacturing finished, no further updates beyond Issue 27 foreseen • Further requests/changes beyond Issue 27 are only possible via formal CR to PACS • Level 0 Sorption Cooler I/F not reflected in Issue 27 anymore (separate drawing needed by CEA) • Removing I/F-adapter (ECP#6) accepted by ESA and Industry Overview and Mechanical/Thermal IFs to FPU

6. PACS Thermal I/Fs to SC Ge:Ga Level 0 Level 1 PhFPU Level 0 GeGa Level 0 I/F (2x) Pin I/F changed to rectangular I/F soldered to pin; Conduct resistance at I/F can be tuned to minimize heating of blue detector PhFPU/Cooler Level 0 I/F (2x) Level 1 Level 1 GeGa Level 0 Level 1 I/F (3x) Thread distance changed from 33 mm to 37 mm Overview and Mechanical/Thermal IFs to FPU

7. Mechanical Loads to Level 0 Ge:Ga Detectors I/F • Amendment to CR, H-P-PACS-ME- 008 issued 29.Oct03, includes also updated mechanical load values for the Ge:Ga Detectors L0 I/F to be in line with the changed mechanical I/F (pin to flat mounting I/F): • Torque, longitudinal bending moment to central copper cold pin. < 1.8 Nm • Torque, rotation moment to the central copper cold pin < 0.2 Nm • Axial force to the central copper cold pin < 500 N • Lateral force to the central copper cold pin < 100 N • This IF loads regarded as uncritical • For the fixation of the straps a mounting tool is foreseen Overview and Mechanical/Thermal IFs to FPU

8. Engineering Change at PACS Thermal Cooler L0 I/F • ECP PACS-ME-ECP 06, issued 27-July-03 agreed 16-Oct-03 • Reason for ECP: I/F temperature requirements of 1.85K at the end of the cooler recycling phase, acc. H-P-PACS-CR-0009, cannot be met -> 46h cooler hold time in question • Proposal (agreed): Remove I/F adapter; remaining contribution from PACS side to the overall thermal conductance (He-tank to Evaporator I/F) is now the contact resistance at the I/F to the cooler -> ~ 30% gained in thermal conductivity to the cooler I/F New Design Old Design Overview and Mechanical/Thermal IFs to FPU

9. Mechanical Design at L0 Cooler I/F after ECP • Changed Mechanical I/F Design at PACS Cooler • S/C strap routing/ integration  • location of S/C temperature sensors  • Necessary design change on PhFPU side • rerouting PhFPU 2K strap  • shifting 2K feed through  • I/F baffle to reduce radiation environment  • performed already • CQM Parts manufactured !  • BUT: Mechanical loads from S/C ? PhFPU Feed Through PhFPU Baffles PhFPU Cooling Strap to Bolometer S/C Cooling Strap Evaporator S/C Temp. Sensors S/C Cooling Strap to Pump (cut in drawing, shown partly only) Overview and Mechanical/Thermal IFs to FPU

10. Mechanical Loads to Level 0 Cooler I/F • Change Request to PACS IID-B: H-P-PACS-ME- 008, Issued 26-Nov-2001, I/F Loads identified as Single point failure • The mechanical loads arising from the level 0 cooling straps to the fixation points of the cooling straps at the PACS FPU must be limited. Impact of no-change: Damage of the mechanically sensitive thermal I/Fs during mounting and/or during launch can happen. • Static load: 50 N • Dynamic load: 50 grams (20.8G rms assumed) • CR was not processed further. Reason: missing final design of S/C level 0 cooling strap (under Industry responsibility) • Current Design for the S/C cooling strap: • ½ mass of cooling strap, pulling at the Level 0 I/F was 312 grams • New ½ mass acc. AIR LIQUIDE study could be 100-125 grams Overview and Mechanical/Thermal IFs to FPU

11. Mechanical Loads to Level 0 Cooler I/F (cont.) • First results from FEE on cooler switch I/F done by CEA-SBT (01-Oct-03): • dynamical response of the switch,  (e.g. first eigenfrequency) depends on the additional mass fixed at the interface level: -50 grams, the first eigenfrequency is 194 Hz -100grams ........................................ 180 Hz -300 grams......................................... 140 Hz • maximum admissible mass at I/F could be potentially increased to 100 grams. TN on FEE calculation in preparation. • S/C cooling strap design needs to be balanced between conductance requirements (reduce cross section, change material TBC) and mechanical load requirements • MPE proposes to perform a coupled FEE analysis, to take into account the dynamic behaviour of the S/C cooling strap and to perform a cold vibration test in "full" configuration (PhFPU/cooler/cooler switch + strap) representative to the flight configuration • Amendment to CR, H-P-PACS-ME- 008 issued 29.Oct03, but 100 grams can not be guaranteed as long as no detailed FEE analysis is performed. Overview and Mechanical/Thermal IFs to FPU

12. HERSCHEL L0 I/F Temperature to the Cooler Evaporator • Agreement reached on HERSCHEL Open Tank Solution, HERSCHEL L0 I/F meeting 30-Oct-03 @ESTEC Overview and Mechanical/Thermal IFs to FPU

13. Estimation of PACS Level 0 I/F Temperatures in Orbit HERSCHEL Tank Temperature: 1.7K Material Pods: Al 1050 Open Pods: Open Tank Solution for the Evaporator I/F Conductance data taken from AIR LIQUIDE analysis HP-2-AIRL-AN-0004 *) Can be tuned at the I/F Overview and Mechanical/Thermal IFs to FPU

14. Difference between Ground and Orbit • Tilt of Cryostat • The temperature of the cooler evaporator I/F at the end of the recycling phase defines the condensation efficiency of the 3He (hold time of the cooler) • The difference between on ground and in orbit is the convective effect. This only affects the recycling phase. Once the cooler is cold, orientation does not matter. • In orbit: We can assume the in-orbit case corresponds to a 60-90° tilting for the cryostat on ground. At the end of the recycling phase, the power flowing through the evaporator strap is 18 mW (measured 14 mW in the latest test). • On ground: If the cryostat can only be tilted 20°, the power flowing through the evaporator strap at the end of the recycling phase can extrapolate to be about 30-35 mW !!! Overview and Mechanical/Thermal IFs to FPU

15. Difference between Ground and Orbit (cont.) • Herschel Tank Temperature Orbit: 1.7K Ground (IMT): 1.7K to 1.8K • Temperature shift at cooler I/F up to 100mK due to warm up after days • L1 Temperature (~PACS FPU temperature) Orbit: 3K to 3.5K Ground(IMT): 6.3K to 7.3K • Thermal load from L1 to L0 through switch base increased (0.45mW -> ~2mW) • Impact to hold time (needs further assessment using measured values) • Impact on the Net heat lift at 300mK (needs further assessment using measured values) • Thermal Radiation Environment Orbit: 9K –10K Ground (IMT): 8K – 10K • 5- 6 K, no impact expected, for 10 K we don't know (hard to calculate) • cooler is pretty much covered by protective baffles and caps (best we could do) It is assumed the heat sink to the cryostat drops back down to 1.8 K once the condensation phase is completed Overview and Mechanical/Thermal IFs to FPU

16. Estimation of PACS Level 0 I/F Temperatures IMT Tank Temperature: 1.75K Thermal radiation environment: 8K-10K, not taken into account Level 1 temperature unknown: 6.3K to 7.3K, not taken into account Conductance data taken from AIR LIQUITE analysis HP-2-AIRL-AN-0004, Al 1050 *) Can be tuned at the I/F Overview and Mechanical/Thermal IFs to FPU

17. Estimation of PACS Level 0 I/F Temperatures EQM Tank Temperature: unknown, used also 1.65K Thermal radiation environment: unknown, should be 5K Level 1 temperature unknown: unknown, should be around 4K to 5K Conductance data taken from AIR LIQUITE analysis HP-2-AIRL-AN-0004 *) Can be tuned at the I/F Overview and Mechanical/Thermal IFs to FPU

18. Summery on PACS Level 0 I/F Temperatures • In Orbit • With the “Open Tank Solution” and with Al 1050 for the HERSCHEL tank pods, PACS Temperature requirements on the L0 I/Fs can by fulfilled. • On Ground • It is not clear whether the PACS cooler can be recycled and/or run at 0.3mK with sufficient cooling power during IMT test. • With a cryostat tilt of more than 20 degree, the situation can be improved by a factor 2.3 (for recycling only) • IMT/EQM testing and testing conditions needs further assessments to be performed by all parties. • Lionel Duband (CEA) needs to perform further calculations (tests?) using new validated boundary temperatures for the Ground test. Overview and Mechanical/Thermal IFs to FPU