NSFCAM2 Mechanical Issues

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NSFCAM2 Mechanical IssuesInitial Design
Concept

• Date first created 04/19/02
• Date last modified 07/01/02

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Issues Design Tasks

• Nsfcam2 WeightSurface Areas
• Nsfcam2 Optical Configuration
• 2048x2048 Hawaii RG Array (new)
• Dichroic Turret and Mount (new)
• Focal Plane Wheel Mechanism (new)
• Lens assembly (new)
• Interface Mount (new)
• Design for use with IRTF AO (Copy? WFS)

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Issues DesignTasks contd

• Vacuum Jacket (new)
• V-Truss (new)
• Thermal Design( old and new)
• Radiation Shield (new)
• Detent Mechanism ( new or redesign)
• Hall Sensors (replace limit switches)
• Compliant Worm Design, adopt
• Phases of Upgrade
• Wave Plate (external to VJ)?

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Nsfcam2 WeightSurface Areas
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Nsfcam2 Optical Configuration

• Note Distance MIM Truck Bottom-to-TFP same for
  Spex and Nsfcam2 (28.655 inch)
• To accommodate new lenses, will extend VJ,
  Rad.Shield and Cold Structure by about 12 inches
• IRTF AO WFS shown
• Need to decide whether to build a duplicate WFS
  or one with a larger FOV
• Interface Mount omitted

MIM Truck
Dichroic
TFP
VJ Extension
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2048x2048 Hawaii 2RG Array

• Design Tasks
• New optics increases Overall Length approx 12
  inch
• Add Extension to existing Cold Structure
• Design new Radiation Shield and Vacuum Jacket to
  suit new Overall Length
• Redesign cold strap 2nd stage
• Adapt 2K Rockwell Array Mount to design
• Design-in Access to Detector
• Design for new wiring of 2K Array

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Dichroic Turret Mount (new design)

• Design Tasks
• Adopt Spex Dichroic Mount Design for Nsfcam2
• Use Spex Generic Motor Mount (Animatics Motor)
• Design new Dichroic Turret and Bearing Assembly
• Design new Dichroic Drive, Train and Detent
  (compliant worm)
• Omit Limit switches, use Hall Sensors instead
• Add 3 outriggers to Dichroic Turret for Stability
• Extend Cold Structure to enclose new Dichroic
  Turret
• Redesign/stiffen up Turret Support Plate
  (backbone)
• Increase Worm Ratio

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Focal Plane Wheel Mechanism (new)

• Design Tasks
• FPW Design new mechanism for Nsfcam2
• Design to fit into space of Thermal Clamp (to be
  removed)
• Lens-Turret capability not needed if FPW is used
• Use Lens-Turret drive for FPW, Redesign
• Detented mechanism, with 4 positions (use
  compliant worm)
• Continuous mechanism may have advantages?
• Use Spex Generic Motor Mount (Animatics Motors)
• Modify Cold Structure for new drive location
  (enlarge port,plug)

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Lens Assembly (new)

• Design Tasks
• Optics-Lens-design requires new Lens-cell
  assembly(ies)
• 2 Lens-cell assemblies required without Focal
  Plane Wheel, Lens-turret must remain operational
• 1 Lens-cell assembly (fixed) required with Focal
  Plane Wheel, Lens-Turret will be modified (fixed
  Lens-cell) or Lens-Turret will be removed and a
  new lens-mount will be built

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Interface Mount (new)

• Design Tasks
• Similar to Mount for Nsfcam, longer by 5 inch
• Use THK mechanism for ease of installation (same
  as for Nsfcam)
• Fabrication cost Approx 8K (from previous one
  built)
• Instrument Mount will be bolted to Top Surface of
  VJ.rather than on the sides, as in Nsfcam. This
  will improve the Stiffness of the Design

Nsfcam Interface (built)
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Design for use with IRTF AO

• Design Tasks
• If we use same WFS and APD Rack Mountthen
• Mounting WFS and APD Rack will be identical as in
  Nsfcam
• Installation procedure same
• Electronics Box may change due to new Array
• CCC might change,depending on cooling capacity
  needed.

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Vacuum Jacket (new)

• Design Features
• 4 Sections ,Alu 6061-T6
• Deep Sections 10, open-ended
• Bolted Assembly
• Custom O-Rings Qty4
• O-Ring placement designed to facilitate assembly
• Inside Dimensions identical to Nsfcam
• Weight as shown 166 lbs
• Weight Relief Estimate 20
• Interface Mount bolts to top section, increases
  stiffness
• Top cover provides access to Dichroic mechanism,
  detents.
• Bottom cover provides access to Detector and
  wiring

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V-Truss-1 (new)

• Design Features
• Center of Mass of Cold Structure located in
  middle of apex plane gravitational forces
  produce no moment and body does not tilt as it
  deflects.
• Easy Installation Assembly because of sectional
  approach to Vacuum Jacket
• Use G-10 Fiberglass for V-Truss Material
• Calculate required stiffness of V-Trusses

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V-Truss-2 (new)

• Design Features
• V-Truss Bases are attached to blue section of VJ
  first.V-Trusses are in place when adding Cold
  Structure
• Apexes are attached to Cold Structure full
  access
• Upper part of Radiation Shield will also be in
  place when inserting the Cold Structure (not
  shown)
• Yellow top sits on horizontal table for assembly

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V-Truss Calculation(Stiffness, Heat Conduction)
S (rad) nAEsin2phi/L Stiffness of system
acting in plane of apexes) n4 (number of
V-Trusses) E4.06exp6 lbs/in2 (Elastic Modulus
for G-10) A1/4 inch x 2 inch.5 in2
(x-section/leg) Phi(ang)30 deg (semi-angle at
apex) L4 inch/cos(phi) (length of
leg) S4.39exp5 lbs/in FS(rad)x x80lbs/4.39exp
5 4.6 micron (deflection) for 80 lbs
Cold-Structure No tilt involved Cold Structure
supported at C-of-G
Ref R.P.Hastings
C-of-G
S(rad)
Cold Structure
Heat Conduction thru V-Trusses Calculated by
comparing to (NICI) 2 Watt A/L NICI
9.84exp-2 A/L Nsfcam2 1.08exp-1 Ratio is approx
1 2 Watts Ratio Nsfcam2/Nsfcam 1.7x more
conductive
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Thermal Design-1

• Notes/Design Changes
• Increased Heat Load due to increased size of Cold
  Structure and Radiation Shield
• Preliminary Estimates(Areas) Cold Structure up
  16 , Radiation Shield up 36 (Spreadsheet)
• Preliminary Estimates (Mass) Cold Structure up
  20, Radiation Shield up 36
• Original Radiation Shield in Nsfcam was NOT
  polished
• Recalculate the needed cooling capacity based on
  new Cold Structure Mass and Surface Areas
• May have to go with 1050 cti Cryocooler
• Recalculate the thermal Strap
• E-Box redesign possible due to new 2K Array

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Thermal Design-2
Existing Thermal Design
Vacuum Jacket
Cold- Structure
350 CTI Cooler
Pre-charge Can (2.5L)
Rad-Shield Passive Non-Polished
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Thermal Design-3
New Thermal Design
Vacuum Jacket

• Notes on New Thermal Design
• Same as for Spex
• Need to calculate Precharge Capacity required
• Need to calculate Cooler Capacity

Cold- Structure
350 CTI Cooler
Pre-charge Can (2.5L)
Rad-Shield Active-Cooled Polished
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Radiation Shield (new)

• Design Features
• 3/32 Shield Thickness Total Weight 20 lbs
  Total Surface Area 4118 in2, in and out (2.65
  m2)
• 4 Shear- webs for thermal isolation and support
• Polish all in-and-out side surfaces to 10 micron
  finish (not done in Nsfcam)
• Follows design approach used for Vacuum Jacket
• Geometry of shear-web 1 inch free L 1/32 thick
  Qty 4
• Conductive Heat Load due to shear-webs will be
  approximately 160 mW

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X-Section (updated 06/06/02)redo
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Upgrade Schedule-1 Build Phase

• Plan (Given we use FPW)
• Tasks prior to opening up Nsfcam
• Build a new Dichroic Turret, complete with drive
  train and detent
• Build one Lens-cell assembly for new optics
  lenses
• Build one Lens-cell Mount
• Build the FPW complete with drive train and
  detent
• Build the plate which holds the Dichroic Turret,
  Lens-cell Mount and FPW. This plate is a a
  modified version of the existing one. This is the
  backbone for the new parts/assemblies inside
  Nsfcam2
• Build new Motor Mounts (Animatics) for all the
  mechanisms in Nsfcam2
• Build new Vacuum Jacket
• Build new Radiation Shield
• Build Cold Structure Extensions (Dichroic Turret
  and 2K Extension)

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Upgrade Schedule-2 Modify Fit Phase

• Tasks after opening Nsfcam
• Remove Dichroic Turret,Lensturret, drive trains
• Remove Thermal Clamp
• Modify Existing Cold Structure (Add tapped holes
  etc)
• Fit new internal Nsfcam2 to modified Cold
  Structure
• Fit Bottom Extension to Cold Structure
• Fit new V-Trusses
• Add Top Extension to fit the new Design for
  Dichroic Turret and Drive
• Fit new Radiation Shield using shear webs
• Fit new Vacuum Jacket
• Fit new drive trains
• Fit Generic Motors (from Spex)

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Time Estimate Spreadsheet