HOPI FAA Safety PDR
6 November, 1998
Lowell Observatory
6 November, 1998
HOPI FAA Safety PDR
1
Overview
• Staff Introductions
–
–
–
–
–
–
Ted Dunham - PI, Overall responsibility
Jim Elliot - Co-I
Brian Taylor - Software
Ralph Nye - Mechanical Design
Jim Darwin - Machinist
Rich Oliver - Electronics Technician
6 November, 1998
HOPI FAA Safety PDR
2
Overview
• Character of the Instrument
– Special Purpose Science Instrument for SOFIA
– Occultation Observing
• What are occultations?
• Deployment operation will be common
– Guest Investigator use
– SOFIA Testing - most stringent requirements
– OPERATIONAL FLEXIBILITY IS CRITICAL
6 November, 1998
HOPI FAA Safety PDR
3
Overview
– HOPI is a high-speed imaging system
– Two CCD detectors capable of fast readout
– Reimaging optics, one set optimized for 0.3-0.6
microns, the other for 0.4-1.0 microns
– Unbinned image scale 0.33 arcsec/pixel
– Selectable filters, Hartmann and Focault tests.
– Goal - Allow simultaneous mount on SOFIA
with FLITECAM to extend coverage to 5 mm.
6 November, 1998
HOPI FAA Safety PDR
4
Overview
Stellar Occultation
Geometry
Toward
Occulted Star
Motion of Occulting object
Occulting
object
Shadow of
Occulting object
Earth
6 November, 1998
HOPI FAA Safety PDR
5
Overview
An occultation occurs when an object in the solar
system passes between an observer and a star.
The figure above shows how the object's
shadow is cast on the Earth by the starlight. The
object's motion causes the shadow to move
across the Earth. The path of the shadow across
the Earth's surface is called the occultation track.
The cartoon on the left shows how the
occultation appears as seen by an observer.
The occulting object moves across the sky,
approaching a star. If the observer is in the
correct position on the Earth, the star disappears
behind the object.
6 November, 1998
HOPI FAA Safety PDR
6
Overview
• Operation with FLITECAM is important
– Simultaneous IR imaging capability needed for:
• Certain occultation opportunities
• SOFIA testing
• FLITECAM is just beginning to be defined
– This is the biggest certification issue we face
– We are trying to allow for FLITECAM mount
6 November, 1998
HOPI FAA Safety PDR
7
Overview
View of HOPI with
red and blue
channels in place.
Electronics are
located under the
instrument. The
figures on the next
sheet show views
from the left and
top. Note the small
dewar sizes.
6 November, 1998
HOPI FAA Safety PDR
8
Overview
6 November, 1998
HOPI FAA Safety PDR
9
Overview
• This view shows
HOPI as seen looking
toward the telescope.
The large circular
plate is the 41”
mounting flange. The
red optics are on the
left, the blue on the
right. The mounting
location for the bare
CCD or FLITECAM
is at top center.
6 November, 1998
HOPI FAA Safety PDR
10
Overview
The Hartmann test
mode requires a
modification to the
red side of HOPI.
Some additional
optics are installed
and the camera lens
is removed. These
are small and fully
contained inside the
instrument case.
6 November, 1998
HOPI FAA Safety PDR
11
Overview
A high-throughput
mode is possible by
moving either dewar
(the red one is shown
here) to the top center
location. No
reimaging optics are
in the path. The
other CCD can image
the outer part of the
field for what it’s
worth.
6 November, 1998
HOPI FAA Safety PDR
12
Overview
The preferred
location for
FLITECAM
is at top
center. Here
its dewar is
assumed to be
12 inches in
diameter and
24 inches
long.
6 November, 1998
HOPI FAA Safety PDR
13
Overview
• Instrument Envelope
– A cone with 41” base at
the flange and 12 3/8”
radius 2 meters from
the flange represents
the instrument envelope.
Two electronics boxes
protrude.
– Could rotate about the
optical axis to fix this.
6 November, 1998
HOPI FAA Safety PDR
14
Overview
• The HOPI dewars will
be made by Precision
Cryogenics Inc. (PCI)
like the EXES and
FORCAST dewars.
• This drawing is for a
similar PCI dewar for
another Lowell project.
• The fused silica
windows will have a
safety factor > 10.
Dewar for Lowell
Observatory
Teflon washer
Half Scale Sketch
Ted Dunham
520-774-3358
1.50 OD
1/2-20 thread
for inverted operation
Slot in top of fitting for
insertion & extraction
3.00
.71 ID
Same as other
end of dewar
6061-T6
extruded pipe
0.125 wall,
6.25" OD
Need about an inch of
clear space here for a
mounting bracket
0.065
wall
G10 Supports
evenly spaced,
4 places. 1" wide
x 1/16 thick
x 8" long
ND-16 vacuum
fitting
.25 ID min
stainless
thinwall
tube
2.0 liters LN
Knob pointing
away from fill
tube
~ 7" deep
13.63
6.00
Evacuation valve is rotated
90° into view.
5.00
4 holes for 4-40
evenly spaced on
1.813 BC.
.38
.25
.87
5.33
1.25
Ring welded
inside tube
4.87
6 holes tapped
for 6-32, evenly
spaced on 5.69 BC
2-260 O-ring
2.13
1.81
2-029 O-ring
.38
5.31
.50
1.88
.38
7.06
.38
7.37
8.00
8 equally spaced
8-32 screws on
7.06 BC
8 equally spaced
3/8 ID holes on
8.00 BC
Rotated 22.5°
into view
9.00
6 November, 1998
HOPI FAA Safety PDR
15
Overview
• The HOPI dewars will be made from 6061-T6
aluminum tubing and pipe to reduce welding.
• Outside dimensions will be approximately 8.5”
diameter by 9” long with a 2” long fill stem. The
vacuum vessel walls will be 0.148” thick.
• The nitrogen can will be 7” ID by 5” long. Its
walls will be 0.125” thick.
• The end plates on both the dewar and the nitrogen
can will be 0.5” thick.
6 November, 1998
HOPI FAA Safety PDR
16
Overview
HOPI High-Level System Design - Electronics & Data System
GP S
An te nn a
Stepping
Motors
Fi l ter # 1
Al l 8 PC-48 ch ann el s
i nclu de l i mi ts & ho me
Fo cu s # 1
Pu pi l 1 X
Chopper
to MCCS
VG A Di sp la y & kbd
for deb ug o nl y
Mo to r
dri ve r
bri ck
Hair Box
Linux PC
Industrial
Chassis
1 fi ber
1Hz, 1MHz
2 fi bers
Le ach #1
OMS P C4 8
NI P C-TIO
Ho meb re w
Processor card
Fl a sh d isk
Fl o ppy
Sh utter # 2
Ro om for IMC PID
& am pl ifi ers & 2 nd
OMS b oa rd fo r IR.
Tri gg ers
Sh utter # 1
Pu pi l 1 Y
Fi l ter # 2
10/100 BT
Network
TT L/Fi be r
&
Fi b er/T TL
Trak GPS
Se ri a l
Fi b er p ai r
Ne twork Con ne cti on
To Move PC
Sun Sparc
Ultra 30
Se ri a l
21 " d ispl a y,
keyboa rd
an d mo use
PCI Bus
Disk &
CD-ROM
Se ri a l PCI card
23 Gb Di sk
Ch an nel 1
2 fi bers
Le ach #2
2 fi bers
Le ach ca rd #2
Stub - 2 fi bers
Pu pi l 2 X
Stub IMC Fo cu s
DL T 70 00
Stub fo r IR
23 Gb Di sk
Le ach IR Stub
Le ach IMC
Stub
Sun Sparc
Ultra 5
IMC Stub
Stub - 2 fi bers
TELESCOPE SIDE
6 November, 1998
23 Gb Di sk
Ch an nel 2
Stub Lea ch IR
Pu pi l 2 Y
Stub - IR
fil ter &
pu pi l X Y
SCSI
Le ach ca rd #1
Fo cu s # 2
RACK SIDE
HOPI FAA Safety PDR
Stub Lea ch IMC
10/100 BT
Network
Sma l l di sp
kbd & mo use
17
Overview
• Certification Philosophy
– Goal - Preserve as much optical flexibility as
possible within the original certification.
– Large margins to allow for FLITECAM mount
– Certify main structure, electronics mounts, and
optical mounting method, but not exact
locations of optical elements. Include sufficient
margin to allow for different configurations.
– New elements would need new certification.
6 November, 1998
HOPI FAA Safety PDR
18
Schedule
• Schedule Chart Placeholder
6 November, 1998
HOPI FAA Safety PDR
19
FHA
• Overview
–
–
–
–
–
–
–
Cryogen Boiloff
Pressure Vessel issues
Aircraft Pressure Boundary
Mass Budget
G Loading
Lasers & Gases
Electrical Hazards
6 November, 1998
HOPI FAA Safety PDR
20
FHA
• Cryogen Boiloff
– Liquid nitrogen only, no helium
– Normal boiloff rate is 1.5 cu ft/hour per dewar
– Maximum boiloff rate for a dewar at ambient
internal pressure is ~2 cu ft/min at STP.
– Total liquid capacity is 3 liters per dewar,
corresponding to 70 cu ft of gas at STP.
– Worst case - both dewars boil dry in ~35
minutes and displace 0.2% of the cabin volume.
6 November, 1998
HOPI FAA Safety PDR
21
FHA
• Pressure Vessel Issues
– Dewars will be made by Precision Cryogenics,
like FORCAST and EXES.
– If the dewar neck tube is blocked, rising
pressure could rupture the dewar
– Burst disks with an operating pressure of 30 psi
will be used, a cryogenic one on the nitrogen
can, a room temperaure one on the dewar case.
– There is no oxygen displacement hazard.
6 November, 1998
HOPI FAA Safety PDR
22
FHA
• Aircraft Pressure Boundary
– Formed by windows in the vacuum pipe.
The instrument case is not a pressure vessel.
– 6.5” diameter windows will be either CaF2 (20 mm
thick) or sapphire (6 mm thick) depending on cost.
– Window thicknesses are appropriate for a 1 atmosphere
pressure differential with a safety factor of at least 20.
– DC-8 windows have safety factors ranging from 7-14.
6 November, 1998
HOPI FAA Safety PDR
23
FHA
• Mass Budget
–
–
–
–
–
–
–
–
–
–
CCD Electronics
20 lb x 2
CCD Pwr. Supply
15 lb x 2
“Hair” box
25 lb
Dewars
25 lb x 2
Vacuum pipe
20 lb
Blue dichroic/field lens 6 lb
Blue collimator assy 15 lb
Blue fold mirror
6 lb
Blue camera lens
4 lb
Blue filter/focus assy 15 lb
–
–
–
–
–
–
–
–
–
–
–
Red collimator assy
Red fold mirror
Red camera lens
Red filter/focus assy
Hartmann optics
Mounting plate
Base plate
Side walls
Top and back plates
Additional bracing
Add’l contingency
– TOTAL
6 November, 1998
HOPI FAA Safety PDR
40 lbs
6 lb
4 lb
15 lb
10 lb
100 lb
150 lb
66 lb
20 lb
33 lb
45 lb
700 lb
24
FHA
• G Loading
– Failure of 3/4” thick flange in:
•
•
•
•
•
•
Tension failure, one pin location only
Shear tear-out, one pin location only
bearing failure, one pin location only
pin shear, one pin only
bolt hole shear tear-out
Estimated CG is on-axis (side-side), 4” below the
optical axis (top-bottom), and 10” forward of the
mounting flange (fore-aft).
6 November, 1998
HOPI FAA Safety PDR
25
FHA
• Flange failure in tension
– Here the “cap” on the flange above the center
of the top pin tears off.
Flange diameter = 41”
D = 6.361”
Bolt/pin circle diameter = 990 mm = 38.976”
6 November, 1998
HOPI FAA Safety PDR
26
FHA
• Flange failure in tension, continued
– The distance along the bottom of the “cap”
from the pin to the edge of the plate is
D = sqrt(20.52 - 19.4882) = 6.361 inches
– The area under tension is
A = (2D - dpin) * tp = 8.79 sq. in.
– Here dpin is the pin diameter (1”) and tp is the
plate thickness (3/4”).
6 November, 1998
HOPI FAA Safety PDR
27
FHA
• Flange failure in tension, continued
– The ultimate tensile strength of 6061-T6
aluminum (Ftu), from the FAA SI handbook,
accounting for a safety factor of 1.5, is 25.3 ksi.
– The margin of safety, MS, is
MS = AFtu/Mg - 1 = 8.79*25300/1320*6-1= 27
– Here M is the instrument mass, taken to be the
maximum SOFIA SI weight to allow for
FLITECAM, and g is the 6g downward load.
6 November, 1998
HOPI FAA Safety PDR
28
FHA
• Flange shear tear-out
– Here a triangular piece of the flange tears out.
– The two lengths that fail are
D = d/cos(40) - rpin
= 0.82”
– The shear area is
A = 2D tp = 1.23 sq in.
6 November, 1998
HOPI FAA Safety PDR
29
FHA
• Flange shear tear-out, continued
– The ultimate shear strength of 6061-T6 aluminum
(Fsu), from the FAA SI handbook, accounting for a
safety factor of 1.5, is 16.7 ksi.
– The margin of safety, MS, is
MS = AFsu/Mg-1 = 1.23*16700/1320*6 -1= 1.6
– Here M is the instrument mass, taken to be the
maximum SOFIA SI weight to allow for
FLITECAM, and g is the 6g downward load.
6 November, 1998
HOPI FAA Safety PDR
30
FHA
• Flange bearing failure
– Here the pin causes an inelastic deformation of
the mounting plate and the hole deforms.
– The bearing area A = p rpin tp
= 1.18 sq in
– The allowable yield stress from
the FAA SI Handbook, Fbru,
accounting for the safety factor
of 1.5, is 40.7 ksi.
6 November, 1998
HOPI FAA Safety PDR
31
FHA
• Flange bearing failure, continued
– The margin of safety, MS, is
MS = AFbru/Mg-1 = 1.18*40700/1320*6-1 = 5
– Here M is the instrument mass, taken to be the
maximum SOFIA SI weight to allow for
FLITECAM, and g is the 6g downward load.
6 November, 1998
HOPI FAA Safety PDR
32
FHA
• Flange pin shear
– Here the pin shears off.
– Shear area is the cross-sectional area of the 1”
diameter pin, A = prpin2 = 0.79 sq in.
– The pin material is stainless steel with a shear
strength exceeding that of 6061-T6 aluminum.
The ultimate shear strength for the aluminum
material, (Fsu), from the FAA SI handbook,
accounting for a safety factor of 1.5, is 16.7 ksi.
6 November, 1998
HOPI FAA Safety PDR
33
FHA
• Flange pin shear, continued
– The margin of safety is
MS = AFsu/Mg-1 = 0.79*16700/1320*6-1 = 0.7
– Here M is the instrument mass, taken to be the
maximum SOFIA SI weight to allow for
FLITECAM, and g is the 6g downward load.
– The actual margin of safety will be larger by the
ratio of the shear strength of the pin material to
that of 6061-T6 aluminum.
6 November, 1998
HOPI FAA Safety PDR
34
FHA
• Flange bolt hole shear tear-out
– Here the bolt heads tear through the flange either
because of the 9g forward load or the moment
applied to the top of the flange by the 6g downward
load acting on the instrument’s moment.
– 9g forward load:
• The total shear area is given by
A = p dbh tp nbolts = p * 0.74” * 0.75” * 20 = 34.9 sq in.
Here dbh is the bolt head diameter (washers would help),
tp is the plate thickness, and nbolts is the number of bolts.
6 November, 1998
HOPI FAA Safety PDR
35
FHA
• Flange bolt hole shear tear-out, continued
– 9g forward load, continued
• The margin of safety is given by
MS = AFsu/Mg-1 = 34.9*16700/1320*9-1 = 48
– 6g downward load coupled through instrument CG
• Assume the full load is taken on the two top bolts so the
shear area is given by
A = p dbh tp nbolts = p * 0.74” * 0.75” * 2 = 3.49 sq in.
Here dbh is the bolt head diameter (washers would help),
tp is the plate thickness, and nbolts is the number of bolts.
6 November, 1998
HOPI FAA Safety PDR
36
FHA
• Flange bolt hole shear tear-out, continued
• The tear-out load is smaller
than the downward load
by the ratio dcg/dbc.
• The tear-out load is then
Lt = dcg/dbc M g
= 10/39 * 1320 * 6
= 2030 lbs
• The margin of safety is given
by MS = A Fsu / Lt - 1
= 3.49*16700/2030-1
= 28
6 November, 1998
HOPI FAA Safety PDR
dcg
CG, 10”
from flange
Downward
6g load
dbc
Bolt circle,
39” in
diameter
Tear-out
component
of load
37
FHA
• G Loading Summary
–
–
–
–
–
Tension failure MS = 27. Unrealistic failure mode
Shear tear-out MS = 1.6
Bearing failure MS = 5
Pin shear failure MS = 0.7 (for aluminum pin)
Bolt hole shear tear-out
• 9g forward load case MS = 48
• 6g down coupled load case MS = 28
6 November, 1998
HOPI FAA Safety PDR
38
FHA
• Containment and Penetration Analysis
– Not done in the FAA SI handbook, so not done
here either.
6 November, 1998
HOPI FAA Safety PDR
39
FHA
• Lasers and Gases
– NONE
6 November, 1998
HOPI FAA Safety PDR
40
FHA
• Electrical Hazards
– No high voltages (AC power is the highest)
– No high currents
– Most electronics is COTS
• Sun, SDSU, industrial PC chassis & boards, Trak
GPS, motor driver “bricks”, fiber modems
– Some homemade electronics
• Small timing circuit, fiber interfaces, and cables
with Teflon or Tefzel insulation.
6 November, 1998
HOPI FAA Safety PDR
41
FHA
HOPI High-Level System Design - Electronics & Data System
GP S
An te nn a
Stepping
Motors
Fi l ter # 1
Al l 8 PC-48 ch ann el s
i nclu de l i mi ts & ho me
Fo cu s # 1
Pu pi l 1 X
Chopper
to MCCS
VG A Di sp la y & kbd
for deb ug o nl y
Mo to r
dri ve r
bri ck
Hair Box
Linux PC
Industrial
Chassis
1 fi ber
1Hz, 1MHz
2 fi bers
Le ach #1
OMS P C4 8
NI P C-TIO
Ho meb re w
Processor card
Fl a sh d isk
Fl o ppy
Sh utter # 2
Ro om for IMC PID
& am pl ifi ers & 2 nd
OMS b oa rd fo r IR.
Tri gg ers
Sh utter # 1
Pu pi l 1 Y
Fi l ter # 2
10/100 BT
Network
TT L/Fi be r
&
Fi b er/T TL
Trak GPS
Se ri a l
Fi b er p ai r
Ne twork Con ne cti on
To Move PC
Sun Sparc
Ultra 30
Se ri a l
21 " d ispl a y,
keyboa rd
an d mo use
PCI Bus
Disk &
CD-ROM
Se ri a l PCI card
23 Gb Di sk
Ch an nel 1
2 fi bers
Le ach #2
2 fi bers
Le ach ca rd #2
Stub - 2 fi bers
Pu pi l 2 X
Stub IMC Fo cu s
DL T 70 00
Stub fo r IR
23 Gb Di sk
Le ach IR Stub
Le ach IMC
Stub
Sun Sparc
Ultra 5
IMC Stub
Stub - 2 fi bers
TELESCOPE SIDE
6 November, 1998
23 Gb Di sk
Ch an nel 2
Stub Lea ch IR
Pu pi l 2 Y
Stub - IR
fil ter &
pu pi l X Y
SCSI
Le ach ca rd #1
Fo cu s # 2
RACK SIDE
HOPI FAA Safety PDR
Stub Lea ch IMC
10/100 BT
Network
Sma l l di sp
kbd & mo use
42
Stress
Analysis
• Main Work Surface
– Top and bottom plates are 5mm 304 stainless.
– Both plates will be attached to the mounting
flange and side plates with angle and screws.
– Additional braces will be attached to both
plates with angle and screws also.
– Optical components will be mounted to the top
plate, electronics to the bottom.
6 November, 1998
HOPI FAA Safety PDR
43
Stress
Analysis
• Main Work Surface, continued
– What kind of stress calculations are needed for
the envisioned angle bracket mounting method?
– Will we need to fasten the top and bottom
plates together by means other than the
attachments to the main structure?
– The optical breadboard normally comes with
1/4-20 tapped holes. 1/4-28 is possible to get if
necessary. Should we do this?
6 November, 1998
HOPI FAA Safety PDR
44
Stress
Analysis
• Major Optical Components
– The optics will be mounted as clusters of
connected lenses in modules.
– The modules will be fastened to the work
surface by either 1/4-20 or 1/4-28 screws.
– The worst case component is the 40 lb red
collimator lenses and fold mirror assembly.
– Analyses will be done assuming a 9g load for
simplicity although this load is often too high.
6 November, 1998
HOPI FAA Safety PDR
45
Stress
Analysis
• Major Optical Components, continued
– Ignore the failure in tension case since shear
tear-out is always more of a problem.
– All analyses done for only one bolt.
– The safety margins are as in the FHA section:
•
•
•
•
Shear tear-out:
MS = Fsu 2(d/cos40-rb)t /Mg - 1
Pin (screw) shear: MS = Lmax / M g - 1
Bolt head tear-out: MS = Fsu pdbht / M g - 1
Bearing failure:
MS = Fbru prbt / M g - 1
6 November, 1998
HOPI FAA Safety PDR
46
Stress
Analysis
• Major Optical Components, continued
– The variable definitions are:
• Fsu = ultimate shear strength, 16.7 ksi for 6061-T6
• Fbru = max. bearing strength, 40.7 ksi for 6061-T6
• Lmax = max. screw shear load from MIL-HDBK-5G,
992 lbs for #10, 1718 lbs for 1/4”, assuming 35ksi material
• d = distance of bolt hole center to edge of plate, 1/2”
• t = thickness of plate, 1/8”
• rb = radius of bolt hole, 0.095” for #10, 0.125” for 1/4
• dbh = diameter of bolt head, 0.30” for #10, 0.37” for 1/4
• Mg = mass of unit times g load.
6 November, 1998
HOPI FAA Safety PDR
47
Stress
Analysis
• Major Optical Components, continued
– The results are summarized in the table below:
Load Case
Shear Tear-out
Pin (screw) shear
Bolt head tear-out
Bearing Failure
6 November, 1998
Margin of Safety
5.2
3.8
5.7
4.5
HOPI FAA Safety PDR
48
Stress
Analysis
• Electronics Enclosures
– The worst case enclosure is the industrial PC
chassis for the “hair” box at 25 lbs.
– Analyses will be done assuming a 9g load for
simplicity although this load is often too high.
– The enclosures will be held in place with
1”x1/8” angle brackets made of 6061-T6
aluminum and fastened to the main work
surface and braces with 10-32 screws.
6 November, 1998
HOPI FAA Safety PDR
49
Stress
Analysis
• Electronics Enclosures, continued
– Ignore the failure in tension case since shear
tear-out is always more of a problem.
– All analyses done for only one bolt.
– Use the equations for margin of safety and the
values for screw dimensions etc. from the
Major Optical Components section.
6 November, 1998
HOPI FAA Safety PDR
50
Stress
Analysis
• Electronics Enclosures, continued
– The results are summarized in the table below:
Load Case
Shear Tear-out
Pin (screw) shear
Bolt head tear-out
Bearing Failure
6 November, 1998
Margin of Safety
9
3.4
8
5.7
HOPI FAA Safety PDR
51
Stress
Analysis
• Dewar Overpressure
• For a cylinder, tensile stress due to pressure is
Fs = P * r / t
where P is the pressure difference, r is the cylinder
radius and t is the cylinder’s wall thickness.
• The margin of safety is
MS = Ftu/Fs - 1
where Ftu is the ultimate tensile strength of the
material, 25.3 ksi for 6061-T6 aluminum.
6 November, 1998
HOPI FAA Safety PDR
52
Stress
Analysis
• Dewar Overpressure, continued
• For the dewar, r=4.16”, t=0.148”, and P = 90 psi
(a factor of three more than the burst disk pressure).
The tensile stress is 90*4.16/0.148 = 2500 psi.
• For the nitrogen can, r=3.5”, t=0.125”, and P = 90
psi. The tensile stress is 90*3.5/0.125 = 2500 psi.
• The margin of safety is
25300/2500 - 1 = 9.1
6 November, 1998
HOPI FAA Safety PDR
53
Stress
Analysis
• Dewar Overpressure, continued
• The safety factor for a flat circular plate (I think of it
as a dewar window) is
MS = (4*Ftu/kP) * (t/D)2 - 1
• Ftu is the ultimate tensile strength of the material
k is 1.125 for a simply supported circular plate
P is the pressure differential
t is the plate thickness
D is the plate diameter
6 November, 1998
HOPI FAA Safety PDR
54
Stress
Analysis
• Dewar Overpressure, continued
• For the nitrogen can ends, t=0.5”, D=7.25”
MS = (4*25,300/1.125*90) * (0.5/7.25)2 - 1 = 3.8
• For the dewar ends, t=0.5”, D=8.625”
MS = (4*25,300/1.125*90) * (0.5/8.625)2 - 1 = 2.4
• For the dewar window, t = 3mm, D = 38mm, and the
tensile strength for fused silica is 7100 psi. (4700
psi with a safety factor of 1.5). Then
MS = (4*4700/1.125*90) * (3/38)2 - 1 = 0.16
• If the dewar’s burst disk fails to rupture, the dewar
window will fail before the dewar end plates fail.
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Stress
Analysis
• Instrument Cart
– Floor loading is the issue here
– The cart has not been designed, but we assume it
weighs less than 300 lbs, for a total weight of cart +
instrument, including FLITECAM, of 1600 lbs, the
maximum SI weight.
– The wheel contact area must be adequate to avoid floor
damage when the weight is held by three wheels, at 530
lbs per wheel.
– The floor load limit in ICD SIC-TA-01 is TBD.
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Operations
• Installation Timeline
–
–
–
–
–
Arrive with equipment a week before installation
Integrate instrument in the lab on its cart
Transport to and mount on TAAS for checkout
Transport to aircraft and install on the telescope
Store cart in the lab
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Operations
• Ground Operations
–
–
–
–
Dewar fills will occur nominally twice a day.
Over weekends, dewars can warm up.
Cooldown should take < 8 hours (TBD).
Instrument tests and data transfer operations
will occur during the days.
– Power will be required with the aircraft out of
the hangar for two hours prior to takeoff.
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Operations
• Instrument Interfaces
–
–
–
–
Mechanical interface to telescope and rack
Cart carrying instrument to the telescope
GPS antenna required on the aircraft
120V/60Hz power required at rack and on
telescope
– Vacuum line for the evacuated gate valve pipe
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Operations
• Power Budget
• Power Budget
– Telescope-mounted parts
•
•
•
•
– Rack-mounted parts
Blue electronics 120 W
Red electronics 120 W
“Hair” box
150 W
Contingency
100 W
• TOTAL
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•
•
•
•
•
•
Computer
Monitor
Tape drive
2 disk drives
GPS receiver
Contingency
• TOTAL
140 W
180 W
90 W
150 W
40 W
100 W
700 W
60
Operations
• Motorized reconfiguration during flight
–
–
–
–
–
Done during normal telescope operation
Focus of red and blue channels
Pupil stop positioning
Filter wheel rotation
During Hartmann operation, MLM and setup
lens are in the filter wheel and can be changed.
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Operations
• Manual reconfiguration during flight
– Cage the telescope before reconfiguration
– Insert/remove Hartmann collimator, folding
mirrors, and beamsplitter/LED source
– Insert/remove pupil imaging optics and knife
edge for Focault test
– Dummy weights provided to maintain balance
– Swap dewars or electronics in case of failure
– Simple repairs in case of in-flight failure
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Operations
• Reconfiguration between flights
–
–
–
–
Add or delete FLITECAM
Bare CCD mode - one CCD dewar in upper posn.
Change filter wheel contents, pupil stop size
Change pressure seal. There are 4 configurations:
•
•
•
•
2 windows, vacuum pipe evacuated
1 window in gate valve assy, no pipe at all
1 window at gate valve end of pipe, no vacuum in pipe
1 window at instrument, no pipe.
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Operations
• Modifications and Upgrades
– Possibilities still under consideration:
• Image motion compensation camera system
• Infrared system to take the place of FLITECAM?
– Unknown modifications for future observations
– These modifications would follow their own
certification timeline.
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Documentation
• Safety and Airworthiness Documents
– FAA Certification Notebook
• This will be kept “live” by recording major
maintenance and instrument upgrades as they occur.
It will include procedures and certification docs.
– Drawing Set.
• The numbering system will be based on the HAWC
system in the FAA book, but simplified for our
instrument and modified to fit the existing Lowell
drawing system as follows.
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Documentation
• Drawing numbers will be of the form:
EXP083-XNNnnS
EXP083 is HOPI’s Lowell project number.
• Here X is a letter designation:
– M for mechanical (including cryo and vacuum) systems
– E is for electrical systems
– O is for optical systems
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Documentation
• NN is a subsystem number. 00 is a table defining all
the subsystems. The drawings under subsystem 01
are assembly drawings of the full system.
• nn is a drawing number. 00 is a table of contents for
all the drawings in this subsystem. Drawings may
have more than one sheet.
• S is a drawing size, ranging from A to E.
• All drawings will have a title block similar to the
one shown in the FAA certification manual.
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Continued
Airworthiness
• Little expected airworthiness-related maintenance
– Inspect pressure seal windows prior to each flight
series.
– Inspect cabling insulation prior to each flight series.
– Check for loose fasteners prior to each flight series.
– Test burst disks at intervals TBD?
– Insure fasteners in good condition when changed.
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Outstanding
Issues
•
•
•
•
FLITECAM development
Burst disks
Mounting large computer monitor on rack
What modifications of COTS equipment will be
required?
• Need strength information on NAS hardware
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