Preliminary Airworthiness

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 2516 GeGa photoconductor arrays
• 55 (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. Lasers and 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 O2 ³ 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 gt 0.48 l/h
• 2.8l LHeII (HeII cryostat) pumping time 18 h gt
  0.15 l/h
• 30l LN2 estimated hold time 29 h gt
  1.03 l/h

17
Cryogen Boil-off

• For 8 hour flight, total boil-off is
• (0.48 l/h)(8h) 3.8l LHe gt 2.7 m3 gaseous He
• (0.15 l/h)(8h) 1.2l LHeII gt 0.8 m3 gaseous He
• (1.03 l/h)(8h) 8.2l LN2 gt 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)
• gt 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 6.210-3 l/s of He gas
• gt 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)/(5.310-4 m2) 89 m/s (40
  m/s)
• gt velocity of flow is 60 (28) of sound speed
• Viscosity of He gas at 6 K is 210-6 Pas
• Reynolds number in tube is 9106 (2.6106)
• gt Flow in neck is turbulent

25
Double Neck Insert

• Pressure Rise
• Pressure in LHe cryostat is p1 a (a2
  p22)1/2 ()
• p2 ambient pressure 105 Pa
• a (llrv)/(2d)
• Tube drag number l 7.2310-3 (8.610-3)
• 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 in LHe cryostat is 1.017105 Pa
  (1.007105 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 oclock
  pins
• Relevant emergency loads are 5g upward and 6g
  downward
• Maximum load is 490 kg (6g) gt 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
• gt 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 Dpinl 3cm5cm 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
• gt 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 Dboltpt 1.2 cmp2 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 _at_ 3A 12 V _at_ 3A)
  with a battery backup to insure proper shutdown

51
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

52
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

53
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

54
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

55
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

56
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

57
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

58

• Stress Analysis
• Norbert Geis
• MPE
• 15 December 1998

59
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

60
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

61
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

62
Vacuum Container
top shell
middle part
base shell
63
Vacuum Container Analysis
1bar

• Top shell Dimensions
• length l 860 mm
• loaded area
• A 1376 cm2
• pressure 1 bar

64
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

65
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

66
Nitrogen Cryostat
67
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

68
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

69
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

70
Main Helium Vessel
71
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
72
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 gt fh
• Point B fm lt fh
• Point C fm fh

73
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

74
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

75
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

76
Auxiliary Helium Vessel
p 3.5 bar
77
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

78
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

79
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

80
Example LN2-Tabs

• LN2-Tab Dimensions

LN2 tab
LHe tab
LHe II tab
81
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 tw2/6
  (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

82
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 kE(t/l)2
• k buckling factor 8.9 (According to DIN
  4114)
• E elastic modulus of fiberglass at 4 K
  7.5105 N/cm2
• Fbu (8.9)(7.5105)(0.2/9.5)2 2950 N/cm2

83
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

84
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

85
Hard Stops
LN2 plate

• hardstop

tab
LHe plate
86
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 (29gLr)1/2 0.3 m/s
• T kinetic energy ½mobjv2 260 Ncm

87
Hard Stops Analysis

• Shear Analysis (9g forward)
• Dimensions of hard stop
• bstop width 2.4 cm
• wstop thickness 3.5 cm gt 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 0.385E
  2,772,000 N/cm2
• Fstop force on stops (1/nstop)(2TobjAstopGA
  l/hstop)1/2 55000 N
• fshear shear stress Fstop/Astop 6550 N/cm2
• M.S. (Fsu/fshear) - 1 (11500/6550) - 1 0.7

88
Hard Stops Analysis

• Failure in Tension (9g forward)
• fbend bending stress Mstop/Wstop
• Mstop bending moment Fstophstop 55000 Ncm
• Wstop moment of resistivity bw2/6
• 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

89
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 (26gLr)1/2 0.35 m/s
• T kinetic energy ½mobjv2 343 Ncm

90
Hard Stops Analysis

• Shear Analysis (6g downward)
• Dimensions of hard stop
• bstop width 2 cm
• wstop thickness 1.5 cm gt 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 0.385E
  2,772,000 N/cm2
• Fstop force on Stops (1/nstop)(2TobjAstopGA
  l/hstop)1/2 15000 N
• fshear shear stress Fstop/Astop 4975 N/cm2
• M.S. (Fsu/fshear) - 1 (11500/4975) - 1 1.3

91
Hard Stops Analysis

• Failure in Tension (6g downward)
• fbend bending stress Mstop/Wstop
• Mstop bending moment Fstophstop 6000 Ncm
• Wstop moment of resistivity bw2/6
• 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

92

• Miscellaneous Items
• Dirk Rosenthal
• MPE
• 15 December 1998

93
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

94
Cryostat mount
95
Cryostat mount
96
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

97
Pressure Coupling Device
98
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

99
Boresight box
polyethylene window
pressure coupling device
mirror
dichroic filter
lens
O-rings
O-rings
100
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

101
Electronic Enclosures
102
Electronic Enclosures (cont.)
103
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 gt stable configuration
• Technical data
• Mass 105 kg
• Wheel track 750 mm
• Overall center of gravity above ground 970 mm

104
SI Cart
105
SI Cart
106

• FIFI LS Operations
• Dirk Rosenthal
• MPE
• 15 December 1998

107
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

108
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

109
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

110
Operations System checks

• Check out electronics
• Verify detector health
• Verify functionality of mechanisms
• Perform laboratory calibration measurements

111
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

112
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

113
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 whats allowed

114
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

115

• Documentation
• Albrecht Poglitsch
• MPE
• 15 December 1998

116
Documentation

• List of required documents
• Drawing list
• Material Certification Records
• Control Documents

117
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

118
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

119
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)

120
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

121
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

122
Certification

• Design documentation in certification logbooks
• Certification papers on file (material and
  hardware)
• Correspondence on file (project, DERs, DARs)

123
Control Documents

• Operations control documents
• Regular operation
• Failure handling
• Continued airworthiness documents

124

• FIFI LS PADR
• THE END