1 / 124

Preliminary Airworthiness Design Review for FIFI LS (Field-Imaging Far-Infrared Line Spectrometer) MPE 15 December 1998

Preliminary Airworthiness Design Review for FIFI LS (Field-Imaging Far-Infrared Line Spectrometer) MPE 15 December 1998. Overview Albrecht Poglitsch MPE 15 December 1998. The FIFI LS Team. MPE Garching PI: Albrecht Poglitsch CoIs: Norbert Geis (Instrument Scientist)

cricket
Download Presentation

Preliminary Airworthiness Design Review for FIFI LS (Field-Imaging Far-Infrared Line Spectrometer) MPE 15 December 1998

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Preliminary Airworthiness Design Review for FIFI LS (Field-Imaging Far-Infrared Line Spectrometer) MPE 15 December 1998

  2. Overview Albrecht Poglitsch MPE 15 December 1998

  3. The FIFI LS Team MPE Garching • PI: Albrecht Poglitsch • CoIs: Norbert Geis (Instrument Scientist) Reinhard Genzel (MPE director) Leslie Looney (Project Scientist) Dieter Lutz Linda Tacconi • Engineers: H. Dohnalek (Design engineer, cryo/mechanics) G. Kettenring (Support engineer, FE modeling) J. Niekerke (Electrical Engineer, control electronics) G. Pfaller (Head of MPE machine shop) M. Rumitz (Electrical engineer, readout electronics) H. Wang (Electrical engineer, control SW/HW) • Students: Dirk Rosenthal (Detector development) Walfried Raab (Cryostat definition, grating, optics) Alexander Urban (Detector & readout testing)

  4. The FIFI LS Team (cont.) Univ. of Jena • CoI: Thomas Henning • Student: Randolf Klein (Software: user interface, data analysis)

  5. FIFI LS Overview • PI Instrument for SOFIA • Wavelength ranges 42-110 mm & 110-210 mm • Resolution 0.03-0.1 mm (~ 175 km/s) • Instantaneous spectral coverage 1300 - 3000 km/s • Two 25´16 Ge:Ga photoconductor arrays • 5´5 (spatial pixels) ´ 16 (spectral channels) • Built by MPE Garching / Univ. Jena, Germany

  6. System Overview

  7. FIFI LS Instrument

  8. FIFI LS Instrument

  9. Instrument

  10. Instrument • Cryostats and vacuum vessel built from Aluminum 5083 (AlMg4.5Mn) (TBD for vacuum vessel) • Indium sealed stainless steel necks • Work surfaces attached to bottom of cryostats • Work surfaces are not part of cryostats • Work surfaces connected via fiberglass tabs • Optic components mounted on work surface and surrounded by sheet aluminum cryogenic shields

  11. Schedule Norbert Geis MPE 15 December 1998

  12. FIFI LS Schedule

  13. Functional Hazard Analysis I Alexander Urban MPE 15 December 1998

  14. Analysis Overview I.Cryogenic Issues 1.Quiescent cryogen boil-off • Cabin oxygen goes from 21% to 20.7% 2.Rapid cryogen boil-off, worst case • Cabin oxygen goes from 21% to 19.5% 3.Vacuum vessel overpressure • Use room temperature pressure relief devices 4.Cryogen can overpressure • Use double neck design with warm pressure relief devices

  15. Analysis Overview II.Structural Issues 5.Estimated Masses • Total weight including cart: 595 kg • Total weight w/o cart: 490 kg 6.g-loading 7.Containment analysis 8.Structural analysis • Finite Element analysis will be performed 9. Lasersand Gases • Possible use of class IIIb or less alignment laser • No noxious gases used in FIFI LS

  16. Cryogen Boil-off 1.Quiescent Cryogenic Boil-Off Assumptions • Cabin volume ~866 m3 (30000 ft3) • Must have O2³ 19.5% of cabin air • 8 hours flight Gas generation rate • 1l LHe produces 0.7 m3 gaseous He at room T, P • 1l LN2 produces 0.65 m3 gaseous N2 at room T, P • 36l LHe (main LHe cryostat) estimated hold time 75 h => 0.48l/h • 2.8l LHeII (HeII cryostat) pumping time 18 h => 0.15 l/h • 30l LN2 estimated hold time 29 h => 1.03 l/h

  17. Cryogen Boil-off • For 8 hour flight, total boil-off is: • (0.48 l/h)(8h) = 3.8l LHe => 2.7 m3 gaseous He • (0.15 l/h)(8h) = 1.2l LHeII => 0.8 m3 gaseous He • (1.03 l/h)(8h) = 8.2l LN2 => 5.3 m3 gaseous N2 • Corrected for reduced pressure in cabin (~4/3 V0) • 4.7 m3 He and 7.0 m3 N2 • Impact on cabin oxygen is: • 21% (1 - 11.7/866) = 20.7% • This is above the minimum of 19.5% and assumes no ongoing recirculation

  18. Cryogen Boil-off 2.Rapid Cryogen Boil-Off After Loss of Vacuum Assumption • 39l LHe and 30l LN2 boil-off instantly Gas generation rate • 39l LHe produces 27.3 m3 gaseous He at room T, P • 30l LN2 produces 19.5 m3 gaseous N2 at room T, P • Corrected for reduced pressure in cabin (~4/3 V0) • 36.4 m3 He and 26 m3 N2 Effect on cabin O2: • 21% (1 - 62.4/866) = 19.5% • This fulfills the requirement of 19.5% and assumes no ongoing recirculation

  19. Vacuum Vessel Overpressure 3.Vacuum Vessel Overpressure • Vacuum vessel is not strong enough to contain all cryogen at room temperature • Warm pressure relief devices on vacuum vessel • Commercial spring-loaded relief device • Opens at 0.1 bar (TBD) differential pressure

  20. Cryogen Vessel Overpressure 4.Cryogen Vessel Overpressure • None of the cryogen vessels are strong enough to contain all cryogen at room temperature LN2 Vessel • Two independent necks • Bleed valve at one neck • Two warm pressure relief devices at other neck opens at 0.1 bar (TBD) and 0.5 (TBD) differential pressure • No need for cold pressure relief device or double neck insert Main LHe Vessel and Auxiliary LHe Vessel • Use of double neck inserts

  21. Double Neck Inserts • Two independent tubes to LHe cryostats • Total diameter of tubes: • Main LHe Cryostat: 2.6 cm • Auxiliary LHe Cryostat: 1.6 cm • One way valves are at room temperature • Insert removed during LHe transfer (on ground) • Red tag procedure guarantees installation of double neck inserts before flight • During pumping on LHe: • Additional warm pressure relief device in pump line if necessary

  22. Double Neck Inserts

  23. Double Neck Insert He Boil-Off • Maximum boil-off in case of vacuum failure • Assume: • Heat input of 1W per cm2 of cryostat wetted by LHe (*) • Total surface of LHe (LHeII) cryostat is 7500 cm2(1300 cm2) => total heat input is 7500W (1300 W) • Temperature of outflowing gas: 6 K • Density of He gas at 6 K is 8 kg/m3 • 1W heat input generates 6.2·10-3 l/sof He gas => total generated volume of He gas is 47 l/s (8 l/s) (*) W. Lehmann, G.Zahn, “Safety Aspects for LHe Cryostats and LHeTransport containers”, ICEC 7 Procs., 1978,569-579

  24. Double Neck Insert Characterization of Flow • Assumption: Neck is dominant impediment to flow • Maximum velocity of flow is speed of sound • Sound speed in He gas at 6 K is 145 m/s • Assume: • Cross section of neck is 5.3 cm2 (2 cm2) • Mean velocity of flow is (generated gas)/(cross section of neck) = (0.047 m3/s)/(5.3·10-4 m2) = 89 m/s (40 m/s) => velocity of flow is 60% (28%) of sound speed • Viscosity of He gas at 6 K is 2·10-6 Pa·s • Reynolds number in tube is 9·106 (2.6·106) => Flow in neck is turbulent

  25. Double Neck Insert Pressure Rise • Pressure inLHe cryostat is p1 = a + (a2 + p22)1/2(*) • p2 = ambient pressure = 105 Pa • a = (l·l·r·v)/(2·d) • Tube drag number l = 7.23·10-3(8.6·10-3) • Length of neck l = 0.23 m • Mean velocity of flow v = 89 m/s (40 m/s) • Diameter of neck d = 2.6 cm (1.6 cm) • Pressure inLHe cryostat is 1.017·105 Pa (1.007·105 Pa) giving a differential pressure of 0.017 bar (0.007 bar) (*) According to: Willi Bohl,Technische Strömungslehre, Vogel-Verlag, 1978

  26. Functional Hazard Analysis II Walfried Raab MPE 15 December 1998

  27. Mass Budget 5. Estimated Masses • Vacuum vessel 259 kg • Cryostat mount 50 kg • Electronic boxes 30 kg • Cart 105 kg • Optics 20 kg • Cryogen vessels N2: 84 kg (including Cryogens) LHe (4K): 45 kg LHe (2K): 1.4 kg • Total weight 595 kg • Total weight w/o cart 490 kg

  28. Center of Gravity • 550 mm from TA flange along beam • 400 mm above beam axis

  29. g-Loading 6. g-Loading • Mass of mounted Instrument (m) = 490 kg • Thickness of FIFI LS-flange (t) = 20 mm • Number of bolts (n) = 13 • Bolt circle diameter (Bc) = 990 mm • Bolt diameter (Dbolt) = 12 mm • Number of shear pins = 2(4) • Shear pin diameter (Dpin) = 25.4 mm • Shear pin circle diameter (Dpi) = 990 mm According to MIL-HDBK5G using the A-Basis for Aluminum 5083: • Ultimate shear strength (FSu) = 11500 N/cm2 • Ultimate tensile strength (Ftu) = 18390 N/cm2 • Bearing yield stress allowable (Fbru) = 27560 N/cm2

  30. Nasmyth Flange

  31. Nasmyth Flange

  32. Flange Failure at Pin Inserts • Flange failure modes at pin inserts are a) bearing failure and b) flange failure in tension Assumptions for both scenarios • Entire shear load is reacted on two pins • Highest tension is reacted on 3 and 9 o’clock pins • Relevant emergency loads are 5g upward and 6g downward • Maximum load is 490 kg (6g) => 29400 N • Tension load per pin is 14700 N

  33. Bearing Failure a) Bearing Failure • Failure mode is yielding of the contact area between the pin and the flange with deformation of the flange material Calculation of bearing failure • Abr = bearing area = 2.2 cm x 1.7 cm = 3.74 cm2 • fbr = tensile stress = 14700 N/3.74 cm2 = 3930 N/cm2 • M.S. = (Fbru/fbr) - 1 = (27560/3930) - 1 = 6

  34. Flange Failure in Tension SI flange dowel pin

  35. Flange Failure in Tension b) Flange Failure in Tension • Failure mode is rending of the flange material at the smallest cross section Calculation of Flange Failure • ft= tensile stress = P/A • P = tension load = 14700 N • A = area in tension = (13.5)(2) cm2 = 27 cm2 • ft = 14700/27 = 544 N/cm2 • M.S. = (Ftu/ft) - 1 = (18390/544) - 1 = 33

  36. Bolt Hole Shear Tear-Out Two basic types of bolts Instrument bolts (2) barrel nuts in instrument ribs Cradle bolts (11) use of caged nuts provided by observatory

  37. Bolt Hole Shear Tear-Out • Flange material needs to react to the forward loading and the moments created by vertical and lateral loads • Forward load • Equally divided over all 13 bolts assuming 9 g-loading • Pf = forward shear load per bolt = 490 kg (9g)/13 = 3390 N • Moments created by vertical load • Highest at topmost bolts • Reacted equally on 2 instrument bolts • Pv = moment due to vertical load per bolt • Pv = 490 kg (6g)(55/40)/2 = 20200 N => Vertical loading yields much higher bolt load

  38. Bolt Hole Shear Tear-Out Instrument Bolts Barrel nut shear tear-out • Pv = shear load = 490 kg (6g)(55/40)/2 = 20200 N • Abr = shear area = Dpin·l = 3cm·5cm = 15 cm2 • fbr = tensile stress = Pv/Abr = 20200 N/15 cm2 = 1350 N/cm2 • M.S. = (Fbru/fbr) - 1 = (27560/1350) - 1 = 19.5

  39. Bolt Hole Shear Tear-Out Instrument Bolts Rib failure in tension: • Pv = tension load = 20200 N • As = tension area = (5cm - 3cm) ·5cm = 10 cm2 • fs = tensile stress = Pv/As = 20200N/10cm2 = 2020 N/cm2 • M.S. = (Fsu/fs) - 1 = (11500/2020) - 1 = 4.7

  40. Bolt Failure • Cradle bolts 1/2”, provided by observatory • Instrument bolts M12, provided by team • steel alloy 10.9 : 57400 N ultimate strength • Highest load on single instrument bolt is 20200 N • M.S. = (57400/20200) - 1 = 1.8

  41. Bolt Hole Shear Tear-Out Cradle bolts • Forward load • Equally divided over all 11 bolts assuming 9 g-loading • Pf = forward shear load per bolt = 490 kg (9g)/11 = 4000 N • Moments created by vertical load • Highest at topmost bolts • Reacted equally on 2 bolts • Pv = moment due to vertical load per bolt • Pv = 490 kg (6g)(55/60)/2 = 13500 N => Vertical loading yields much higher bolt load

  42. Bolt Hole Shear Tear-Out Cradle bolts • fs = tensile stress = Pv/As • Pv = shear load = 13500 N • As = shear area = Dbolt·p·t = 1.2 cm·p·2 cm = 7.54 cm2 • Dbolt = bolt diameter, t = flange thickness • fs = 13500/7.54 = 1790 N/cm2 • M.S. = (Fsu/fs) - 1 = (11500/1790) - 1 = 5.4

  43. Containment Analysis 7. Containment Analysis • Loose Objects inside the vacuum vessel cannot attain the gate valve • Most parts are too big to fit through cryostat window • Vacuum tight polyethylene window • All screws inside boresight box secured by wires or equivalent

  44. Structural Analysis 8. Structural Analysis • Not completed as of 15 December 1998 • Finite element analysis will be made for critical items

  45. Lasers and Gases 9. Lasers and Gases • No noxious Gases used in FIFI LS • Possible use of class IIIb or less alignment laser

  46. Electrical Hazard Analysis Leslie Looney MPE 15 December 1998

  47. Electronic System Overview • Instrument mounted electronics will be packaged within aluminum enclosures • Cables to/from cryostat will be internal to enclosure • All high speed signals will be on fiber • All copper cables will be shielded with overall braid • All external connectors will be military style when appropriate • All systems will be properly shielded, fused, and grounded

  48. Electronic System Overview • Teflon or Tefzel insulated wire will be used in custom electronics and interconnects • Battery system will be used to insure proper shutdown of read-out electronics

  49. Electronics Overview

  50. Warm Read-Out Electronics • Two aluminum enclosures mounted on instrument (one for each detector array) • Contains amplifiers, multiplexers, and A/Ds • All electronics are custom • No high speed signals on copper cables between SI rack and PI rack; 4 MHz output signal on fiber • Clock (£2 MHz on coax from SI rack to SI; 10 kHz) and Sync (£ 0.6 kHz) signals from SI rack • End of scan (EOS) signal (£ 0.6 kHz) to SI rack • DC power on Tefzel cable (±24 V @ 3A; 12 V @ 3A) with a battery backup to insure proper shutdown

More Related