# Presentation: 191812

## Mechanical Overview

Rodger Farley
Mick Correia
Judy Brannen
16 November 2001 

- Rodger Farley
- Mick Correia
- Judy Brannen
- 16 November 2001

## Mirrors:ULE
Primary:90% light weighted 
Secondary,Tertiary and Fold: 50% light weighted
Structure: M55J composite
Total Instrument Mass: 1011kg
(includes spacecraft interface structure 50kg)

- Primary:90% light weighted
- Secondary,Tertiary and Fold: 50% light weighted
- Structure: M55J composite
- Total Instrument Mass: 1011kg
- (includes spacecraft interface structure 50kg)

## Metering Structure similar to HST design
Spider 3 point tangent design to give torsional stiffness
Mirrors and Aft optics are kinematically mounted using both bi-pods or flexures 

- Spider 3 point tangent design to give torsional stiffness
- Mirrors and Aft optics are kinematically mounted using both bi-pods or flexures

## Secondary Mirror Focus Mechanisms 
   Requirements:
Tip:  1 arc sec
Tilt:  1 arc sec
Focus: + / - 0.5 mm total travel, 1 micron incremental motion
Transverse X: + / - 0.5 mm total travel, 10 micron incremental motion
Transverse Y: + / - 0.5 mm total travel, 10 micron incremental motion

*   **Requirements:*
- Tip:  1 arc sec
- Tilt:  1 arc sec
- Focus: + / - 0.5 mm total travel, 1 micron incremental motion
- Transverse X: + / - 0.5 mm total travel, 10 micron incremental motion
- Transverse Y: + / - 0.5 mm total travel, 10 micron incremental motion

## Design suggestion:
Three point ball-screw mechanism developed by Swales Aerospace.  
Heritage: FUSE spacecraft, tip-tilt-focus for 15 kg UV mirror.  Used once per orbit approximately.  It has exceeded the design life by many factors.
Demonstrated Performance: 0.35 micron resolution, +/- 1 mm total travel
Mass Estimate: approx 18 kg

- Three point ball-screw mechanism developed by Swales Aerospace.
- Heritage: FUSE spacecraft, tip-tilt-focus for 15 kg UV mirror.  Used once per orbit approximately.  It has exceeded the design life by many factors.
- Demonstrated Performance: 0.35 micron resolution, +/- 1 mm total travel
- Mass Estimate: approx 18 kg

## Aperture Door Requirements:
Non air-tight, nor particularly light-tight
Re-closable, designed for 100 actuations guaranteed
Re-close in 100 seconds
Deploy to out of the FOV
Deployed frequency above 10 Hz
Unpowered holding torque: ???

- Non air-tight, nor particularly light-tight
- Re-closable, designed for 100 actuations guaranteed
- Re-close in 100 seconds
- Deploy to out of the FOV
- Deployed frequency above 10 Hz
- Unpowered holding torque: ???

## Design suggestion:
HST-like, with Moog Schaeffer type 5 actuator.  
Heritage: HST-ish
Demonstrated Performance: 2.25 deg/s fast, 0.23 deg/s slow for first and last 5 degrees of rotary motion
Mass Estimate: 61 kg door and associated mechanisms, 6.5 kg electronics
Note: the mass can be reduced by using composite materials
Mass moment of inertia about the hinge line: 63.7 kg-m^2 (HST)
Power Estimate: 14 watts at fast speed plus 12 watts peak for drive electronics

- HST-like, with Moog Schaeffer type 5 actuator.
- Heritage: HST-ish
- Demonstrated Performance: 2.25 deg/s fast, 0.23 deg/s slow for first and last 5 degrees of rotary motion
- Mass Estimate: 61 kg door and associated mechanisms, 6.5 kg electronics
*Note*: the mass can be reduced by using composite materials
- Mass moment of inertia about the hinge line: 63.7 kg-m^2 (HST)
- Power Estimate: 14 watts at fast speed plus 12 watts peak for drive electronics

## Type 5 rotary actuator 

- Type 5 rotary actuator
- One time launch latch
- Folding hinge line at mid door position
- if required
- Concerns regarding rotary actuator:
-    Torsional Stiffness for frequency
-    Detent holding torque for maneuvers

## Shutter Mechanism Requirements:
Light-tight to:? 
Shutter speed: If a fast shutter is possible, then operate in 1/40 of a second.  If a slow shutter is reasonable, then operate in 1 second to open or close, with a position vs. time curve having 1/40 second accuracy.  It is desirable but not necessary that the shutter should operate such that the exposure times for all detector CCDs are the same to within 1/20 of a second. 
Fail-safe requirements? (fail open, fail close, don’t bother?)
Frequency of operation:  800 actuations (open or close) per day for 3 years  (2 per 220 seconds).  This works out to about 1x106 actuations for the mission.

- Light-tight to:?
- Shutter speed: If a fast shutter is possible, then operate in 1/40 of a second.  If a slow shutter is reasonable, then operate in 1 second to open or close, with a position vs. time curve having 1/40 second accuracy.  It is desirable but not necessary that the shutter should operate such that the exposure times for all detector CCDs are the same to within 1/20 of a second.
- Fail-safe requirements? (fail open, fail close, don’t bother?)
- Frequency of operation:  800 actuations (open or close) per day for 3 years  (2 per 220 seconds).  This works out to about 1x106 actuations for the mission.

## Shutter Mechanism Design:
Considerations are the location relative to a pupil or a focus  
Fast shutters have problem of impact transient vibrations and require large forces. Fast shutters would require snap-action mechanism 
Slow shutters require a PID controller with sensors
Locations considered 
Behind the primary
Behind the folding flat
Inside the folding flat
Just in front of the folding flat

- Considerations are the location relative to a pupil or a focus
- Fast shutters have problem of impact transient vibrations and require large forces. Fast shutters would require snap-action mechanism
- Slow shutters require a PID controller with sensors
- Locations considered
- Behind the primary
- Behind the folding flat
- Inside the folding flat
- Just in front of the folding flat

## Lampton Scissors Shutter with snap action

## Clam shell four-bar linkage shutter

## Bow tie and half bow tie shutters 

- Bow tie and half bow tie shutters

## Boomerang Shutter

## Cross section of folding mirror

- Port lid type shutter

## Suggested Qualification Program:

Build brass-boards, as many as needed. Determine how much of the design is sensitive to workmanship
Build engineering test unit that will go thru the qualification program of vibration and thermal cycling 
Build a life test unit and test in thermal vacuum chamber
Cycle 1 million times, then inspect for wear
Continue life test till 10 times required life

- Build brass-boards, as many as needed. Determine how much of the design is sensitive to workmanship
- Build engineering test unit that will go thru the qualification program of vibration and thermal cycling
- Build a life test unit and test in thermal vacuum chamber
- Cycle 1 million times, then inspect for wear
- Continue life test till 10 times required life