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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)

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Preliminary Airworthiness

Design Review for FIFI LS

(Field-Imaging Far-Infrared Line Spectrometer)

MPE

15 December 1998


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Overview

Albrecht Poglitsch

MPE

15 December 1998


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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)


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The FIFI LS Team (cont.)

Univ. of Jena

  • CoI: Thomas Henning

  • Student: Randolf Klein (Software: user interface, data analysis)


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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






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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


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Schedule

Norbert Geis

MPE

15 December 1998



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Functional Hazard Analysis I

Alexander Urban

MPE

15 December 1998


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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


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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


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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


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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


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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


  • Vacuum vessel overpressure l.jpg
    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


    Cryogen vessel overpressure l.jpg
    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


    Double neck inserts l.jpg
    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



    Double neck insert l.jpg
    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


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    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


    Double neck insert25 l.jpg
    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


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    Functional Hazard Analysis II

    Walfried Raab

    MPE

    15 December 1998


    Mass budget l.jpg
    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


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    Center of Gravity

    • 550 mm from TA flange

      along beam

    • 400 mm above beam axis


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    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




    Flange failure at pin inserts l.jpg
    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


    Bearing failure l.jpg
    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


    Flange failure in tension l.jpg
    Flange Failure in Tension

    SI flange

    dowel pin


    Flange failure in tension35 l.jpg
    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


    Bolt hole shear tear out l.jpg
    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


    Bolt hole shear tear out37 l.jpg
    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


    Bolt hole shear tear out38 l.jpg
    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


    Bolt hole shear tear out39 l.jpg
    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


    Bolt failure l.jpg
    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


    Bolt hole shear tear out41 l.jpg
    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


    Bolt hole shear tear out42 l.jpg
    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


    Containment analysis l.jpg
    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


    Structural analysis l.jpg
    Structural Analysis

    8. Structural Analysis

    • Not completed as of 15 December 1998

    • Finite element analysis will be made for critical items


    Lasers and gases l.jpg
    Lasers and Gases

    9. Lasers and Gases

    • No noxious Gases used in FIFI LS

    • Possible use of class IIIb or less alignment laser


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    Electrical Hazard Analysis

    Leslie Looney

    MPE

    15 December 1998


    Electronic system overview l.jpg
    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


    Electronic system overview48 l.jpg
    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



    Warm read out electronics l.jpg
    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


    Grating encoder l.jpg
    Grating Encoder

    • Two aluminum enclosures mounted on instrument (one for each detector array)

      • Contains grating position electronics and medium voltage power to control PZTs

      • All custom electronics

    • Power supplied on Tefzel insulated cable


    Guiding camera and driver l.jpg
    Guiding Camera and Driver

    • COTS CCD camera (and COTS camera driver, TBD) in aluminum enclosure mounted on instrument

      • Fiber optic link to dedicated COTS PC computer at PI rack

      • BNC coax link to monitor in PI rack/video distribution system

    • PC computer will control guiding camera and receive data output

      • PC computer linked to VX real-time computer in PI rack


    Master clock l.jpg
    Master Clock

    • A programmable (£ 2 MHz) frequency standard that is used to derive other clock standards in instrument

      • Sends clock signals (£ 16 kHz) to the Controller, Grating Driver, Chopper Driver, and K Mirror Driver

      • Sends clock (£ 10 kHz) and sync signals (£ 0.6 kHz) to both detectors

    • Mounted in SI rack

    • All connections are Teflon insulated shielded copper cables


    Mechanism drivers l.jpg
    Mechanism Drivers

    • Custom electronic drivers for Chopper, K Mirror, and two Gratings

      • Commanded by the controller

    • Aluminum enclosures in the SI rack

    • Teflon insulated, shielded cable used for signal


    Hardware controller l.jpg
    Hardware Controller

    • Hardware controller in an aluminum enclosure in SI rack

      • Commanded by the VX real-time computer

      • Controls the Master Clock frequency and sync signals

      • Controls the Grating, Chopper, and K Mirror Drivers


    Computers l.jpg
    Computers

    • COTS VX Real Time computer in VME crate at PI rack

      • Primary control computer

      • Data from both detectors received via fiber cable

      • Performs some data processing

      • Commands Controller via shielded copper cables

      • Communicates to Windows NT workstation via Ethernet bus

    • COTS Windows NT computer in VME crate at PI rack

      • Used at SI rack by personnel to monitor SI

      • Update of instrument status

      • Detector data inquires

      • Data from camera guider through the PC

      • Sends request to the TA control through the MCCS


    Batteries l.jpg
    Batteries

    • Batteries used to ensure proper shutdown of sensitive read-out electronics.

    • Battery size and type TBD

    • Batteries will be mounted in SI rack in containment enclosure


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    Stress Analysis

    Norbert Geis

    MPE

    15 December 1998


    Stress analysis cryostat l.jpg
    Stress Analysis Cryostat

    • Four components need to be analyzed

      • Vacuum container

      • Nitrogen vessel

      • Main Helium vessel

      • Auxiliary Helium vessel

    • Preliminary Analysis with Structural formula

    • “First article testing” on above components is planned

      • No certification of welding

      • Witnessed burst-pressure test

    • Finite Element Analysis using Pro/Mechanica will be performed on components which are impractical to test


    Vessel design analysis l.jpg
    Vessel Design/Analysis

    • Avoid sophisticated analysis and certification of electron beam welding shop by witnessed “burst test” of all vessels to 3 times the maximum operating (differential) pressure

    • Maximum operating pressure defined by relief valves, including margin for tolerance in relief pressure

    • Verify design with analytical calculation / FEM analysis to withstand burst test without permanent deformation

    • Operating differential pressure (+ margin) for

      • vacuum vessel: 0.1 (+0.05) bar

      • nitrogen vessel: 1.1 (+0.05) bar

      • main helium vessel: 1.1 (+0.05) bar

      • auxiliary helium vessel: 1.1 (+0.05) bar


    Vacuum container l.jpg
    Vacuum Container

    • Material (TBD): certified 5083 Aluminum (Al Mg 4.5 Mn)

    • Light weight construction

    • Consists of 3 main parts

      • Top shell

      • Middle part

      • Base shell

    • Each main part milled

    • O-ring seals between main parts


    Vacuum container62 l.jpg
    Vacuum Container

    top shell

    middle part

    base shell


    Vacuum container analysis l.jpg
    Vacuum Container Analysis

    1bar

    • Top shell Dimensions:

      • length: l = 860 mm

      • loaded area:

        A = 1376 cm2

      • pressure: 1 bar


    Vacuum container analysis64 l.jpg
    Vacuum Container Analysis

    • Highest stress occurs at top shell

    • Stress analysis on cross bar

      • f = tensile stress = M/W

        • M = bending moment = ql2/8

          • q = Ap/l = 16 kp/cm

        • M = (16)(86)2/8 kpcm = 147920 Ncm

        • W = moment of resistivity = I/c = 26 cm3

          • I = Moment of inertia; c = distance from neutral axis

      • f = 147920/26 = 5690 N/cm2

      • M.S. = (17430/5690) - 1 = 2

        All formulas from: Formeln der Technik, Heinrich Netz, G. Westermann, 1960


    Nitrogen vessel l.jpg
    Nitrogen Vessel

    • Material: 5083 Aluminum (AlMg4.5Mn)

    • Eccentric cylindrical shape

    • Main body milled

    • Top plates electron beam welded to main body

    • Dimensions:

      • Outer diameter: 830 mm

      • Inner diameter: 348 mm

      • Height: 109 mm

      • Volume: 30 l



    Nitrogen vessel67 l.jpg
    Nitrogen Vessel

    • Structural analysis is applied to weakest cross bar

    • Dimensions:

      • length: l = 210 mm

      • width: b = 140 mm

      • assumed pressure: p = 3.5 bar


    Nitrogen vessel68 l.jpg
    Nitrogen Vessel

    • f = tensile stress = M/W

      • M = bending moment = ql2/8

        • q = Ap/l = 49 kp/cm

      • M = (49)(21)2/8 kpcm = 27000 Ncm

      • W = moment of resistivity = 3.6 cm3

    • f = 27000/3.6 = 7500 N/cm2

    • M.S. = (18390/7500) - 1 = 1.5


    Main helium vessel l.jpg
    Main Helium Vessel

    • Material: 5083 Aluminum (AlMg4.5Mn)

    • Dome shaped to enhance pressure stability

      • made on lathe from single block

    • Base plate electron beam welded to dome

    • Dimensions:

      • Diameter: 560 mm

      • Max. Height: 227 mm

      • Volume: 36 l



    Main helium vessel71 l.jpg
    Main Helium Vessel

    Dome Shape

    • Wall thickness t = 0.5 mm

    • Constructed with two overlapping radii

      • Structural Analysis applied to three critical Points

        • A: Point at base plate

        • B: Intersection of the

          radii R1 and R2

        • C: Point on radius R1

    p = 3.5 bar


    Main helium vessel72 l.jpg
    Main Helium Vessel

    • Two independent directions of stress on surface

      • meridian stress

      • horizontal stress

    • For each of the points A,B,C the higher stress is considered

      • Point A: fm > fh

      • Point B: fm < fh

      • Point C: fm = fh


    Main helium vessel73 l.jpg
    Main Helium Vessel

    Stress at point A:

    • fA = meridian tensile stress = pR0/2t

    • fA = (3.5)(28)/2(0.5) kp/cm2 = 980 N/cm2

    • M.S. = ( Ftu/fA) - 1 = (18390/980) - 1 = 17.8

      Stress at point B:

    • fB = horizontal tensile stress = pR1(2-R1/R2)/2t

    • |fB| = |(3.5)(86)(2-86/16) /2(0.5)| kp/cm2 = 10150 N/cm2

    • M.S. = ( Ftu/|fB|) - 1 = (18390/ 10150) - 1 = 0.8

      Stress at point C:

    • fC = meridian tensile stress = pR1/2t

    • fC = (3.5)(86)/2(0.5) kp/cm2 = 3010 N/cm2

    • M.S. = ( Ftu/fC) - 1 = (18390 /3010) - 1 = 5.1


    Main helium vessel74 l.jpg
    Main Helium Vessel

    Circular Base Plate

    • Dimensions:

      • Radius R0: 280 mm

      • Height h: 30 mm

      • fbp = tensile stress = 1.24 pR02/h2

      • fbp = 1.24(3.5)(28)2/(3)2 kp/cm2 = 3780 N/cm2

      • M.S. = (Ftu/ftp) - 1 = (18390/3780) - 1 = 3.9


    Auxiliary helium vessel l.jpg
    Auxiliary Helium Vessel

    • Material: 5083 Aluminum (AlMg4.5Mn)

    • Closed cylinder

    • Top and base plate electron beam welded to cylindrical walls

    • Dimensions

      • Vessel radius R: 146 mm

      • Vessel height H: 213 mm

      • Volume 1.8 l



    Auxiliary helium vessel77 l.jpg
    Auxiliary Helium Vessel

    Circular Top Plate

    • Top plate thickness ttp = 12 mm

      • ftp = tensile stress of top plate = 1.24 pR2/ttp2

      • ftp = 1.24(3.5)(7.3)2/(1.2)2 kp/cm2 = 1606 N/cm2

      • M.S. = (Ftu/ftp)-1 = (18390/1606) - 1 = 10.5

        Circular Base Plate

    • Base plate thickness tbp = 20 mm

      • fbp = tensile stress of base plate = 1.24 pR2/tbp2

      • fbp = 1.24(3.5)(7.3)2/(2)2 kp/cm2 = 578 N/cm2

      • M.S. = (Ftu/ftp) - 1 = (18390 /578) - 1 = 30.8


    Auxiliary helium vessel78 l.jpg
    Auxiliary Helium Vessel

    Cylindrical Walls

    • Cylinder wall thickness tcyl = 2 mm

      • fcyl = tensile stress in vessel wall = pR/tcyl

      • fcyl = (3.5)(7.3)/0.2 = 1278 N/cm2

      • M.S. = (Ftu/fcyl) - 1 = (18390 /1278) - 1 = 13.4


    Composite material tabs l.jpg
    Composite Material Tabs

    • Made from GFRP/CFRP (TBD)

    • Provide thermal isolation and precise positioning for cryogen vessels

    • Three types of tabs:

      • LN2-tabs : between Vacuum Vessel and LN2 plate

      • LHe-tabs: between LN2 plate and LHe plate

      • LHeII- tabs: between LHe plate and LHeII plate

    • Number of tabs: 4 of each type

    • Failure of tabs would impair instrument performance and lead to increased cryogen boil-off

    • Load is highest on LN2-tabs

      • Structural Formula Analysis shown here as an example


    Example ln 2 tabs l.jpg
    Example: LN2-Tabs

    LN2-Tab Dimensions:

    LN2 tab

    LHe tab

    LHe II tab


    Example ln 2 tabs81 l.jpg
    Example: LN2-Tabs

    Tab shear failure

    • Failure mode is shear of the tab along width

      • 9g forward load is applied on two tabs

    • Dimensions:

      • Width w = 9.5 cm

      • Effective height or distance between bolt holes h = 4.2 cm

      • Thickness t = 0.2 cm

    • fs = shear stress per tab = ½·(M/W)

      • M = bending moment = 150 kg (9g)·4.2 cm = 56700 Ncm

      • W = moment of resistivity = t·w2/6 = (0.2)·(9.5)2/6 = 3 cm3

    • fs = (1/2)·(56700/3) = 9450 N/cm2

    • M.S. = (Fsu/fs) -1 = (27560/9450) - 1 = 1.9


    Example ln 2 tabs82 l.jpg
    Example: LN2-Tabs

    Tab buckling

    • Failure mode is buckling of the tab

      • 6g downward load is applied on four tabs

        Ultimate buckling stress allowable

    • Fbu = ultimate buckling stress = k·E·(t/l)2

      • k = buckling factor = 8.9 (According to DIN 4114)

      • E = elastic modulus of fiberglass at 4 K = 7.5·105 N/cm2

    • Fbu = (8.9)(7.5·105)(0.2/9.5)2 = 2950 N/cm2


    Example ln 2 tabs83 l.jpg
    Example: LN2-Tabs

    Buckling stress

    • Tab cross section A: 1.9 cm2

    • F = force per tab = 150 kg (6g)/4 = 2250 N

    • f = buckling stress = F/A = 1180 N/cm2

    • M.S. = (Fbu/fb) - 1 = (2950/1180) -1 = 1.5


    Hard stops l.jpg
    Hard Stops

    • Fiber tabs from non-certified material

    • Hard stops at each fiber tab

      • Made from 5083 Aluminum (AlMg4.5Mn)

      • Hard stops treated as nominal support system

      • Failure of tabs under limit loads considered non-critical

    • Stops are recessed into work surfaces to take up shear forces

    • Finite Element Analysis of hard stops will be performed

    • Analysis with structural formulas shown here

      • Failure modes considered:

        • Shear tear under 9g forward load

        • Failure in tension under 9g forward load

        • Shear tear under 6g downward load

        • Failure in tension under 6g downward load


    Hard stops85 l.jpg
    Hard Stops

    hardstop

    LN2 plate

    tab

    LHe plate


    Hard stops analysis l.jpg
    Hard Stops Analysis

    Analysis for 9g forward load

    • Assume:

      • Main LHe container and auxiliary LHe container accelerating at 9g for a distance of Lr = 0.5 mm

      • Mass of object mobj = 56 kg

    • v = speed at hard stop = (2·9g·Lr)1/2 = 0.3 m/s

    • T = kinetic energy = ½·mobj·v2 = 260 Ncm


    Hard stops analysis87 l.jpg
    Hard Stops Analysis

    Shear Analysis (9g forward)

    • Dimensions of hard stop:

      • bstop = width = 2.4 cm

      • wstop = thickness = 3.5 cm => Shear area Astop: 8.4 cm2

      • hstop = height = 1 cm

    • Assume:

      • Shear load is equally divided on two hard stops

      • GAl = Shear modulus of Aluminum = 0.385·E = 2,772,000 N/cm2

    • Fstop = force on stops = (1/nstop)(2·Tobj·Astop·GAl/hstop)1/2 = 55000 N

    • fshear = shear stress = Fstop/Astop = 6550 N/cm2

    • M.S. = (Fsu/fshear) - 1 = (11500/6550) - 1 = 0.7


    Hard stops analysis88 l.jpg
    Hard Stops Analysis

    Failure in Tension (9g forward)

    • fbend = bending stress = Mstop/Wstop

      • Mstop = bending moment = Fstop·hstop = 55000 Ncm

      • Wstop = moment of resistivity = b·w2/6

      • Wstop = (2.4)·(3.5)2/6 = 4.9 cm3

    • fbend = 55000/4.9 = 11220 N/cm2

    • M.S. = (Ftu/fbending) - 1 = (18390/11220) - 1 = 0.5


    Hard stops analysis89 l.jpg
    Hard Stops Analysis

    Analysis for 6g downward load

    • Assume:

      • Main LHe container and auxiliary LHe container accelerating at 6g for a distance of Lr = 1 mm

      • Mass of object mobj = 56 kg

    • v = speed at hard stop = (2·6g·Lr)1/2 = 0.35 m/s

    • T = kinetic energy = ½·mobj·v2 = 343 Ncm


    Hard stops analysis90 l.jpg
    Hard Stops Analysis

    Shear Analysis (6g downward)

    • Dimensions of hard stop:

      • bstop = width = 2 cm

      • wstop = thickness = 1.5 cm => Shear area Astop: 3 cm2

      • hstop = height = 0.4 cm

    • Assume:

      • Shear load is equally divided on eight hard stops

      • GAl = Shear modulus of Aluminum = 0.385·E = 2,772,000 N/cm2

    • Fstop = force on Stops = (1/nstop)(2·Tobj·Astop·GAl/hstop)1/2 = 15000 N

    • fshear = shear stress = Fstop/Astop = 4975 N/cm2

    • M.S. = (Fsu/fshear) - 1 = (11500/4975) - 1 = 1.3


    Hard stops analysis91 l.jpg
    Hard Stops Analysis

    Failure in Tension (6g downward)

    • fbend = bending stress = Mstop/Wstop

      • Mstop = bending moment = Fstop·hstop = 6000 Ncm

      • Wstop = moment of resistivity = b·w2/6

      • Wstop = (2)·(1.5)2/6 = 0.75 cm3

    • fbend = 6000/0.75 = 8000 N/cm2

    • M.S. = (Ftu/fbending) - 1 = (18390/8000) - 1 = 1.3


    Slide92 l.jpg

    Miscellaneous Items

    Dirk Rosenthal

    MPE

    15 December 1998


    Cryostat mount l.jpg
    Cryostat mount

    • Light weight construction made of 5083 Aluminum (AlMg4.5Mn)

    • No welding

      • All components joined by rivets, bolts and pins

    • Just mechanical support

      • Pressure seal provided by stainless steel bellows

    • Finite Element Analysis will be performed




    Pressure coupling device l.jpg
    Pressure Coupling Device

    • Provides pressure seal between FIFI LS and gate valve

    • Double O-ring sealed snout

    • Stainless steel bellows

    • Aluminum tube to protect bellows from mechanical damage



    Boresight box l.jpg
    Boresight box

    • Splits off visible from IR light

    • Optically aligns FIFI LS to Telescope axis

    • Contains:

      • Dichroic filter

      • Optical mirror

      • Adjustment mechanisms

      • Optical lens ( = pressure window)

    • Pressure inside is stratospheric pressure

    • Pump port required

      • Sealed off before take-off


    Boresight box99 l.jpg
    Boresight box

    polyethylene window

    pressure coupling device

    mirror

    dichroic filter

    lens

    O-rings

    O-rings


    Electronic enclosures l.jpg
    Electronic Enclosures

    • Six electronic enclosures mounted to instrument

    • Working on appropriate mounting techniques

    • Will use certified materials

    • Finite element analysis of stresses at critical areas for g-loading will be performed




    Si cart l.jpg
    SI Cart

    • Used to transport FIFI LS into airplane and to lift onto (already installed) cryostat mount (cradle)

    • Four rotatable and securable wheels with brakes

    • Hand-operated lifting mechanism

      • Four lever arms

      • Threaded control rods

    • In transport configuration FIFI LS bolted to cart

    • Low center of gravity => stable configuration

    • Technical data:

      • Mass: 105 kg

      • Wheel track: 750 mm

      • Overall center of gravity above ground: 970 mm




    Slide106 l.jpg

    FIFI LS Operations

    Dirk Rosenthal

    MPE

    15 December 1998


    Fifi ls operations l.jpg
    FIFI LS Operations

    • Document will be produced to govern instrument set-up and maintenance

      • Steps for routine, ongoing inspections

      • Precool safety check-list

      • Installation and removal procedures

      • On-board cryogen refill procedures

      • In-flight operations

        • Procedure for access to SI/SI-Rack during flight

      • Warm-up process


    Operations preparation l.jpg
    Operations: Preparation

    • Arrival at destination

    • Check shipping crates for coarse damage

    • Open-up cryostat

    • Visual inspection of entire system

      • Inspect cryostat window

      • Check for frayed cables, loose hardware, etc.

      • Check for missing system components

      • Check GFRP/CFRP supports

      • Inspect batteries

    • Re-assemble cryostat


    Operations cool down l.jpg
    Operations: Cool down

    • Check for water in cryogen cans

      • Remove if necessary

    • Pump out vacuum space

      • Use roughing pump to reach coarse vacuum

      • Use turbo pumps to reach end vacuum

    • Leak check vacuum vessel and cryogen cans on 1st cool-down of each flight series

    • Transfer LN2 into LN2 cryostat

    • Transfer LN2 into LHe cryostat

    • Refill both cans when empty

    • Remove N2 from LHe cryostat

    • Transfer LHe in LHe cryostat

    • Refill LHe and LN2 cans as needed


    Operations system checks l.jpg
    Operations: System checks

    • Check out electronics

    • Verify detector health

    • Verify functionality of mechanisms

    • Perform laboratory calibration measurements


    Operations sil l.jpg
    Operations: SIL

    • Attach system to simulator

      • Use SI cart to bring cryostat to mounting plate

      • Installation procedure as on airplane

      • PI rack and SI rack needed (SI rack close to flange)

    • Perform alignment and functionality tests on simulator

    • Remove system from simulator

      • Disconnect cables, fiber links, pump lines

      • Transfer cryostat to SI cart


    Operations ta l.jpg
    Operations: TA

    • Install cradle to Nasmyth flange

      • Cradle can be lifted/positioned manually

      • Fasten nuts & bolts

    • Install FIFI LS on cradle and flange

      • Use installation SI cart to lift and position instrument on cradle

      • Push into docking position and insert & tighten screws

    • Connect all cables and fiber optics links

    • Perform verification tests with MCCS

    • Transfer LN2 and LHe as necessary

      • Bring LN2 and LHe storage dewars on plane

      • Fill cans to capacity

    • Perform daily inspection of system for anything unusual or noteworthy


    Operations in flight l.jpg
    Operations: In-flight

    • Access to instrument during routine operations

      • Turn filter wheel

        • Done by turning knobs

        • Reaching over safety rail probably OK

        • Caged telescope probably OK, but not desired

    • Troubleshooting (diagnostics)

      • Sometimes requires access inside safety rail

      • Examples

        • Swapping electronic boards (inside)

        • Reseating components (inside)

        • Cycling power (outside)

        • Probing voltages (some of both)

    • Need to establish guidelines for what’s allowed


    Operations end of flight series l.jpg
    Operations: End of flight series

    • Disconnect all cables and fiber optic links at end of observing run

    • Remove system from telescope

      • Remove FIFI LS from cradle and flange with cart

      • Remove cradle from Nasmyth flange

    • Return system back to lab

    • Perform any post run checks if necessary

    • Allow system to warm up

      • Place one way valves on both fill ports to prevent water condensation into cryogen cans

    • Place into shipment crates


    Slide115 l.jpg

    Documentation

    Albrecht Poglitsch

    MPE

    15 December 1998


    Documentation l.jpg
    Documentation

    • List of required documents

    • Drawing list

    • Material Certification Records

    • Control Documents


    Documentation list l.jpg
    Documentation List

    • List of documents to produce

      • Operations Control Documents

      • Continued Airworthiness Document

      • Electronics Documentation

      • Hydrostatic Test Plan

      • EMC/EMI Test Plan

      • Final Conformity Test Plan

      • Drawings Package

      • Stress Analysis Report

      • Functional Hazard Analysis

      • Instrument Maintenance Manual


    Documentation drawings l.jpg
    Documentation, Drawings

    • Certification Logbooks

      • Layout

        • 100 Introduction and General Instrument Specifications

        • 200 Documentation, master index

        • 300 Mechanical Specifications

        • 400 Electrical Specifications

        • 500 Functional Hazard Analysis

        • 600 Instrument Installations and Operations

        • 700 Continued Airworthiness and Maintenance Plan

        • 800 Stress Analysis

        • 900 Correspondence with the FAA IPT


    Drawing docs continued l.jpg
    Drawing Docs Continued

    • 1000 Correspondence with FAA DERs

    • 1100 Correspondence with FAA DARs

    • 1200 Drawing log and actual drawings

    • 1400 Conformity paperwork

    • 1500 Test plans

  • Drawing numbering guidelines

    • F-(OP)-(zzz)-S

    • F implies FIFI LS

    • O implies major category

    • P and Q are sub categories

    • zzz is the drawing number

    • S implies the drawing size (numeral)


  • Drawing docs continued120 l.jpg
    Drawing Docs Continued

    • Subcategories of A

      • 1 Assemblies, block diagrams

      • 2 Cryostat

      • 3 Mount

      • 4 Electronic Boxes

      • 5 Calibration Box

      • 6 Cart

      • 7 Electronic Drawings

      • 8 Control documents


    Drawing docs continued121 l.jpg
    Drawing Docs Continued

    • Example: F-235-003-3 could translate as:

      • F = FIFI LS

      • 2 = Cryostat

      • 3 = Helium Temperature Component

      • 5 = Grating Drive

      • 003 = Drawing #003

      • 3 = Drawing size DIN A3

    • Duplicate set of drawings kept at MPE at all times


    Certification l.jpg
    Certification

    • Design documentation in certification logbooks:

      • Certification papers on file (material and hardware)

      • Correspondence on file (project, DERs, DARs)


    Control documents l.jpg
    Control Documents

    • Operations control documents

      • Regular operation

      • Failure handling

    • Continued airworthiness documents


    Slide124 l.jpg

    FIFI LS PADR

    THE END