mirror box presentation final draft
TRANSCRIPT
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Mirror Box
Albert Yang, Tatiana RoyMentor: Lee Wilson
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Ae105 Final Presentation 2
Mirror Boxes
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Two Types of Mirror Boxes
• Mirror box contains all required infrastructure for telescope mirrors– Two reference (rigid)
mirrors and two deformable mirrors in total
– Will focus primarily on the deformable mirrors
Reference Mirrors
Deformable Mirrors
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Box Subsystems• Mirrors
– Mirrors subsystemholds the mirror in place
• Picomotors– Piston/tip/tilt the mirror
• Electronics – House electronics
• Frame – Hold all mirror box
elements and interface with CoreSat 105.6mm
106mm
90mm
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CoreSat Interface
• Must match with pre-established Surrey mechanical and electrical interfaces
CableInterface
MechanicalInterfaces
MechanicalInterfaces
Interface with Surrey
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Functional Requirements
• Survive launch loads• Provide mechanical support for a set of
deformable mirrors, rigid mirrors, and mirror electronics
• Allow mirror to operate within the required range of tip, tilt, and piston positions)
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Performance Requirements
• Provide tip/tilt of up to 6.85°
Picomotors Tilting the Mirror Plate
Mirror Sub-assembly
ReferencePlate
θ
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Mass Budget
• Mass Requirement: <680g per box Current Best Estimate:
Subsystem Current Mass (g) % total Contingency (g) (30%) Total (g)Mirror* 28 5.5 9 37
Picomotors 263 51.7 79 342
Electronics 38 7.5 12 50
Frame 180 35.4 54 234
Total Mass 509 154 663
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Addressing Requirements
• Mirror Mounts– Updated mount design to solve pinching issue– Tested new mount design
• Damping Columns– Designed damping columns to interface with
mirror box and mitigate launch loads– Chose damping material
• Updated mirror box design
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Mirror Mount: Old Design• Curved mirror is extremely thin. Mirror is
prone to deformation near mounting sites– Old mounts designed
for flat mirrors– Curved mirrors need
different mounts– Changes in shape
will lead to reducedoverall performance Old Design Relied on
Cylindrical Magnets
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Mirror Mount: New Design
• Designed new mount– Single point of contact on
each side of the mirror– Top cage required to retain
magnetFixed with epoxy
Magnet/Cage minimum clearance
Tangent Line
Sphere Center Line
Old Mounts New Mounts
Tangent Line
Sphere Center Line
MagnetBall Bearing
Ball Bearing
MagnetBall Bearing
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Testing Mirror Deformations• Zernike coefficients were calculated using
SHWS to measure deformations– Need 2.4m (radius of curvature) path to SHWS– Independent test also conducted– Looking for trefoil shape deformation in mirror
Flat Mirror
SHWS Beam Splitter
Mirror Fixture
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Mirror Deformation Testing Setup
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LaserBeam Splitter
Mask Mirror 1Laser
Laser
Laser
Mirror 2
Laser
Curved Mirror Fixture
Laser
SHWSOne-Way Travel Distance: 2.4mRadius of curvature of mirror
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Mirror Mount Deformation Results• Mirror had high Z4 and Z5 values• Z9 and Z10 are not present in our test
Consequently, mirror mounts do not deform mirrorZ1
Z2 Z3
Z4Z5 Z6
Z8Z9 Z10Z7
Zernike Tested Name
4 .7 Defocus
5 2.5 Oblique Astigmatism
9 <.1 Vertical Trefoil
10 <.1 Oblique Trefoil
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Mirror Mount Characterization• A test was also performed on a Haso SHWS
by Caltech Post-Doc Steve Bongiorno– Performed on different mirror, manufactured to
have less errors– Concluded mirror aberration
was dominated by astigmatism, and not by any trefoil shape
Low Relative Values
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Launch Survival• Large vibration loads during launch: Mirror
will vibrate and possibly shatter1.5g lateral6g vertical
Verti
cal
Lateral
1.5g lateral3g vertical
2.5g lateral3g vertical
From Delta IV Handbook
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Damping Columns
• Damping columns attenuate vibrational energy by physical contact during launch– Damping columns are separated
from the mirror after launch
Extruded Tip for Damping Material
Set screw in a tapped hole
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Damping Material• Chose Red Silicone foam as damping
material– Reported CVCM (collected volatile
condensable materials) of <0.005 (lowest possible)
– Rated for -100F to 400F (required -50F to 50F)
Threads Into Reference Plate
Damping Material at Top
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Updated CAD: Spring Tubes
• Keep mirror plate connected to reference plate while still allowing for normal picomotor operation
• Springs housed by tubes connect reference plate and mirror plate
One end attaches at bottom of tube
One end attaches at mirror plate
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Summary of Mirror Box Progress• Designed new mirror mounts to solve
mirror pinching issue– Prototyped new mounts and characterized
with SHWS test– Showed no appreciable deformation
• Designed damping columns and chose damping material– Fabricated sample damping column
• Updated CAD to reflect design changes
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Ae105 Final Presentation 21
Further Work Required
• Finish launch vibration survivability test– Finish profiling vibration table to make sure it
can reach the frequencies required• More SHWS tests with different
configurations for the mirror– Test mirror with current mount vs. no mount
• Design and assemble reference mirror box
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Backup Slides
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Picomotors Objectives
• Purpose is to tip and tilt mirror
• Must achieve angles of at least 6.84°from normal
• Must unlatch mirror and mirror plate from launch configuration to normal operation
Picomotor actuates up and down
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Picomotors Challenges
• Normal operation must be possible while also securing the mirror plate
• Movements of individual picomotors cannot interfere with each other Picomotors Tilting the Mirror Plate
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Picomotors final design
• Spring system keeps mirror plate attached to reference plate without affecting picomotor performance
• Picomotor heads interface with mirror plate through a kinematic mount to avoid interference between picomotors (cone, flat, vee)
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Picomotors Concern: Interference with Frame
• Ensured in CAD that mirror plate + PCB + mirror + mirror mounts could tilt without intersecting frame
• Using a 20% margin on the maximum tilt, found that mirror assembly has ~0.2mm clearance at closest approach
Clearance on both sides
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Frame Objectives
• The frame must house the device and provide attachment points for the various components
• Must provide mechanical and electrical interfaces with Surrey components
• Allow for easy assembly
Interfaces with Surrey
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Frame Challenges
• Should keep mirror from dropping during assembly (assembled upside down)
• Picomotors must be able to fully extend without causing any interference
Previously problematic area
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Frame Design
• Threaded holes for all sides and reference plate
• Lip on sides keeps mirror from dropping during assembly
• Original height was increased (without affecting optics distances) to accommodate for picomotors max extension
Lips for safe assembly
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Electronics
• 3 PCBs between bottom and reference plate, plus one behind mirror
• 3 PCBs stack has some cropped edges to accommodate for picomotors and spring tubes (does not affect electronics
Ribbon Cable
Electronics Boards
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Mirror Box Overview
• Mirror box is the system that contains all required infrastructure for the telescope mirrors
Box Assembly Inside the Box