Transcript Preliminary Airworthiness Design Review for FIFI LS MPE 15 December 1998

Preliminary Airworthiness
Design Review for FIFI LS
(Field-Imaging Far-Infrared Line Spectrometer)
MPE
15 December 1998
1
Overview
Albrecht Poglitsch
MPE
15 December 1998
2
The FIFI LS Team
MPE Garching
– PI:
– CoIs:
Albrecht Poglitsch
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)
3
The FIFI LS Team (cont.)
Univ. of Jena
– CoI:
Thomas Henning
– Student: Randolf Klein (Software: user interface, data analysis)
4
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
5
System Overview
6
FIFI LS Instrument
7
FIFI LS Instrument
8
Instrument
9
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
10
Schedule
Norbert Geis
MPE
15 December 1998
11
FIFI LS Schedule
1998
Calendar Year Quarter -
1
2
1999
3
4
1
2
2000
3
4
1
2
2001
3
4
1
2
2002
3
4
1
2
3
Core Technologies
Detector
-- Prototype Design/Construction
-- Prototype Testing
-- Flight Arrays
Diffraction Grating & Drive
-- Prototype Design/Construction
-- Prototype Testing
Linear Module
Cryo Tests
Procurement & Mfg.
Tests (Stressed) Tests (Unstressed)
R.T.Tests
Cryo Tests 2nd grating
Baseline Design
Mechanical, Cryostat
Optical, Overall Layout
Electrical, Main Units Definition
Data R/O, Computer H/W, S/W
Safety, Airworthiness
Dimensional, Safety
PDR
Detail Design
Mechanical, Cryostat
Optical, Components, Mounts
Electrical, Design custom
Data R/O, Software
Safety, Airworthiness
Safety + All subcomponents
Tolerancing Mirrors Mounts Cryomechanisms
Controllers Interfaces R/O
Hardware
Safety critical design CDR CDR
Software
Manufacture, Acquisition
Mechanical, Cryostat, Mfg.
Optical Units, Mounts, Acq. & Mfg
Electrical, Custom Electronics Mfg.
Control, Data R/O, Computers
Safety, Airworthiness
critical subsystems
1st spectrometer components
2nd spectrometer
Controllers
R/O electronics
COTS computer eqpmt Control Software
FAA • Conformance • Testing
System Tests
Function, Cryostat, Mechanical
Function, Electronics
Function, Control & Software
Function, Scientific Performance
Safety, Airworthiness
Vacuum Cryo- Total
Mech Syst.
Operations
Syst.
Perf.
NEP
F
i
r
s
t
F
l
i
g
h
t
S
e
r
i
e
s
Tuning of
System
Performance
-Data
Reduction
-Science
Output of
First Flights
S
e
c
o
n
d
F
l
i
g
h
t
Operating
Tuning
Modes Calibration
flight
tests?
FAA
Appr
12
Functional Hazard Analysis I
Alexander Urban
MPE
15 December 1998
13
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
14
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
15
Cryogen Boil-off
1.Quiescent Cryogenic Boil-Off
Assumptions
– Cabin volume ~866 m3 (30000 ft3)
– Must have O2  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 => 0.48 l/h
– 2.8l LHeII (HeII cryostat) pumping time 18 h
– 30l LN2 estimated hold time 29 h
1.03 l/h
=> 0.15 l/h
=>
16
Cryogen Boil-off
• For 8 hour flight, total boil-off is:
– (0.48 l/h)(8h) = 3.8l LHe
– (0.15 l/h)(8h) = 1.2l LHeII
– (1.03 l/h)(8h) = 8.2l LN2
=> 2.7 m3 gaseous He
=> 0.8 m3 gaseous He
=> 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
17
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
18
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
19
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
20
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
21
Double Neck Inserts
22
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/s of 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
23
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
24
Double Neck Insert
Pressure Rise
• Pressure in LHe 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 in LHe 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
25
Functional Hazard Analysis II
Walfried Raab
MPE
15 December 1998
26
Mass Budget
5. Estimated Masses
•
•
•
•
•
•
Vacuum vessel
Cryostat mount
Electronic boxes
Cart
Optics
Cryogen vessels
(including Cryogens)
• Total weight
• Total weight w/o cart
N2:
LHe (4K):
LHe (2K):
259 kg
50 kg
30 kg
105 kg
20 kg
84 kg
45 kg
1.4 kg
595 kg
490 kg
27
Center of Gravity
• 550 mm from TA flange
along beam
• 400 mm above beam axis
28
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
29
Nasmyth Flange
30
Nasmyth Flange
31
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
32
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
33
Flange Failure in Tension
SI flange
dowel pin
34
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
35
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
36
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
37
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
38
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
39
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
40
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
41
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
42
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
43
Structural Analysis
8. Structural Analysis
• Not completed as of 15 December 1998
• Finite element analysis will be made for critical items
44
Lasers and Gases
9. Lasers and Gases
• No noxious Gases used in FIFI LS
• Possible use of class IIIb or less alignment laser
45
Electrical Hazard Analysis
Leslie Looney
MPE
15 December 1998
46
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
47
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
48
Electronics Overview
49
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
50
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
51
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
52
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
53
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
54
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
55
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
56
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
57
Stress Analysis
Norbert Geis
MPE
15 December 1998
58
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
59
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
60
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
61
Vacuum Container
top shell
middle part
base shell
62
Vacuum Container Analysis
• Top shell Dimensions:
1bar
– length: l = 860 mm
– loaded area:
A = 1376 cm2
– pressure: 1 bar
63
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
64
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
65
Nitrogen Cryostat
66
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
67
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
68
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
69
Main Helium Vessel
70
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
71
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
72
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
73
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
74
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
75
Auxiliary Helium Vessel
p = 3.5 bar
76
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
77
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
78
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
79
Example: LN2-Tabs
LN2-Tab Dimensions:
LN2 tab
LHe tab
LHe II tab
80
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
81
Example: LN2-Tabs
Tab buckling
• Failure mode is buckling of the tab
– 6g downward load is applied on four tabs
• Fbu
Ultimate buckling stress allowable
= 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
82
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
83
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
84
Hard Stops
LN2 plate
hardstop
tab
LHe plate
85
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
86
Hard Stops Analysis
Shear Analysis (9g forward)
• Dimensions of hard stop:
– bstop = width = 2.4 cm
– wstop = thickness = 3.5 cm
– hstop = height = 1 cm
=> Shear area Astop: 8.4 cm2
• 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
87
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
88
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
89
Hard Stops Analysis
Shear Analysis (6g downward)
• Dimensions of hard stop:
– bstop = width = 2 cm
– wstop = thickness = 1.5 cm
– hstop = height = 0.4 cm
=> Shear area Astop: 3 cm2
• 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
90
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
91
Miscellaneous Items
Dirk Rosenthal
MPE
15 December 1998
92
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
93
Cryostat mount
94
Cryostat mount
95
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
96
Pressure Coupling Device
97
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
98
Boresight box
polyethylene window
mirror
pressure coupling device
dichroic filter
lens
O-rings
O-rings
99
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
100
Electronic Enclosures
101
Electronic Enclosures (cont.)
102
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
103
SI Cart
104
SI Cart
105
FIFI LS Operations
Dirk Rosenthal
MPE
15 December 1998
106
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
107
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
108
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 cooldown 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
109
Operations: System checks
•
•
•
•
Check out electronics
Verify detector health
Verify functionality of mechanisms
Perform laboratory calibration measurements
110
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
111
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
112
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
113
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
114
Documentation
Albrecht Poglitsch
MPE
15 December 1998
115
Documentation
•
•
•
•
List of required documents
Drawing list
Material Certification Records
Control Documents
116
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
117
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
118
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)
119
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
120
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
121
Certification
• Design documentation in certification logbooks:
– Certification papers on file (material and hardware)
– Correspondence on file (project, DERs, DARs)
122
Control Documents
• Operations control documents
– Regular operation
– Failure handling
• Continued airworthiness documents
123
FIFI LS PADR
THE END
124