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Large Monolithic Mirror LMM

Gary Matthews Manager, Image Collection Systems Eastman Kodak Company April 11, 2003

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Program Goals
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Determine the feasibility of building and processing a 4-meter by 10-meter mirror Determine if a mirror this large can be built to chronographic requirements

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Requirements
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Mirror Requirement
Aperture Shape Length Area Areal Density (Mirror Only) Optical Surface Form Parent diameter Offset distance Radius of curvature Total surface error - 0-3 cycles/aperture - 3-10,000 cycles/aperture - >10,000 cycles/aperture Environment Launch loads Thermal - Operating temperature - Isothermal DT - Axial gradient Dynamic Disturbance
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Description
Approximately elliptical 10m along major axis 2 30m 2 < 25 kg/m (mirror only) Off-axis parabola (k = -1) 11m Diameter Parent 2.11m (center of parent to center of aperture) 29.8m < 10nm rms (after actuator correction) < 8nm rms (after actuator correction) < 5nm rms (after actuator correction) < 1.5nm rms (after actuator correction) 10-g quasi-static axial & lateral combined 20 +/- 0.5 deg C 1.0 deg C 0.5 deg C TBD
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Mirror System Configuration
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Mirror uses kinematic mounting scheme System design minimizes actuators Semi-rigid approach minimizes mid-spatial frequency errors
Passive Mounts (3) Force Actuators (74) Displacement Actuators (9)

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Mirror Design Concept
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Mirror concept builds on successful AMSD segmented core design Mirror constructed of smaller segmented blanks joined before processing

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Faceplates will be pocket milled to reduce mass while maintaining optical performance
Front Plate: 6 Internal Ribs per Cell Back Plate: 3 Internal Ribs per Cell

· Example of pocket milled plate to reduce core areal density · Allows larger core size

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Mirror Performance Correction Analysis
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Input Surfaces, No Correction

Power

Force/Displ Acts % Correction 18/9 97.4 56/9 99.5 74/9 99.6

Astigmatism

Force/Displ Acts % Correction 18/9 98.8 56/9 99.5 74/9 99.6

Coma

Force/Displ Acts % Correction 18/9 94.0 56/9 98.1 74/9 98.5

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Mirror Performance Due to Manufacturing Errors
Input Surfaces, No Correction

Random Unit Moments at Each Mount/ Displ Actuator

Force/Displ Acts % Correction 18/9 73.2 56/9 85.0 74/9 85.5

Random CTE Variations Seg-to-Seg & Front-to-Back

Force/Displ Acts % Correction 18/9 77.7 56/9 82.4 74/9 92.2

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Mirror Error Budget
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Fusion Welding Seams
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Corning has a long history of fusion welding ULETM seams Concept being considered in joining mirror segments prior to slumping

Fusion Welded ULETM Mirror Core
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Large Fusion Welded ULETM Mirror Edge Ring
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Mirror Handling and Shipping Processes
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10m LMM Vaculift

10m LMM Turnover Device & Shipping Container
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Gantry Based Processing Concept
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Risk Assessment
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Mirror Blank Technology Abrasive W ater Jet Cutting of Lightweight Core Segments Abrasive W ater Jet Pocket Milling of Faceplates Low Temperature Fusion Bonding of Blank Segments Edge W elding of Blank Segments Into Monolith Handling of Monolith Diamond Grinding of Monolithic Blank Surfaces Low Temperature Slump Furnace Low Temperature Slump of Mirror Blank

Risk Level 1.0 2.0 1.0 2.5 2.5 2.5 2.7 2.7 0 1 2 3 4 No Risk

Risk Level Definitions Routine or sufficient factory capacity exists. Adaptation of existing processes or improvements to existing facilities. Small scale engineering models or process development needed. Large scale prototype or large scale process demonstration needed. No precedent available, feasibility in peril but big payoff if successful.

Minimal Risk Modest Risk High Risk Grave Risk

Mirror Finishing Technology Fixed Abrasive Diamond Grinding Polishing Support Loose Abrasive Grind and Smooth Loose Abrasive Figure CO2 W avelength Optical Test Large Tool Polishing Small Tool Polishing HeNe W avelength Optical Test Optical Test Support Ion Figure

Risk Level 2.0 2.7 2.0 2.5 1.5 2.0 1.0 2.0 2.5 1.0 0 1 2 3 4 No Risk

Risk Level Definitions Routine or sufficient factory capacity exists. Adaptation of existing processes or improvements to existing facilities. Small scale engineering models or process development needed. Large scale prototype or large scale process demonstration needed. No precedent available, feasibility in peril but big payoff if successful.

Minimal Risk Modest Risk High Risk Grave Risk

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Mirror Design Experience
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Large mirror core Pocket milled demonstration mirror

AMSD highly segmented core
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Subscale Demonstration Mirror Design
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Subscale demonstrator suggested to show proof-of-concept Shares all critical features with full scale 4X10 mirror
Blank Segments, 3x

2x, Edge Weld

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Summary
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A large 4X10 meter appears to be feasible at acceptable risk Mirror smoothness parameters will be difficult but achievable Facilitization will be required for slumping and processing Subscale proof-of-concept mirror can be fabricated and processed using existing facilities

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