copyright 2007 northrop grumman corporation 1 large deployed and assembled space telescopes november...
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Copyright 2007 Northrop Grumman Corporation 1
Large Deployed and Assembled
Space Telescopes November 14, 2007
Ronald S PolidanChief Architect, Civil Systems Division
Charles F Lillie, Gary Segal, Dean DaileyNorthrop Grumman Space Technology
Copyright 2007 Northrop Grumman Corporation 2
Agenda
Expectations
Deployable Observatories
Very Large Observatories
Technology Needs
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Astrophysics Beyond 2020 – Expectations
JWST will have launched in 2013, fulfilled its 5 year prime mission and be on its way to its 10-year lifetime goal
New “infrastructure” elements and technologies are changing the architectural approaches to big space telescopes
Bigger launch vehicles: EELV Heavy and Ares V Advanced optics technology (ultra-light weight mirrors, replication, improved
wavefront sensing and control technologies, …) Advanced deployment and assembly (robotic or crewed) technologies
Linearly extrapolating from the past: Hubble (1990): 2.4 m aperture, 11,110 kg total mass, $4.1 B (FY06, A-D) JWST (2013): 6.5 m aperture, 6,200 kg total mass, $3.5 B (FY06, A-D)
For a similar cost we should expect to produce a ~20 m telescope, launching in the mid-2020s
Assuming anything faster than linear technology development produces 25 meter or larger filled aperture telescopes
20-m or Larger Filled Aperture Telescopes Should be Expected in the 2020’s
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Current State of the Art: JWST
MomentumTrim Flap
Fixed Fwd and Aft Spreader Bars
Aft UPS Bipod Launch Lock Attachment
Points
Unitized Pallet Structures (UPS)
TelescopicSide
Booms
Fixed Side Spreader Bars
Note: S/C Solar Array and Radiator Shades
Shown in Stowed Positions for Clarity
Momentum Trim Flap
Fixed Width Aft Membrane
Core Area
Tower Ext. SMSS Deployment PM DeploymentSecondary DeploymentSunshieldSolar Arrays HGA Cool Down
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Simplest Approach: Scaling Up JWST
Scaling up JWST to large EELV and Ares V launch vehicles
Lowest cost option: a JWST “rebuild” with no new technology development
Use identical cord fold deployment & sunshield architecture and technology
The bottom line for several reasons but mostly having to do with vertical height in the faring (a high center of gravity, load paths and acoustic loads are additional complications) limits you to
~ 8 meter aperture for the largest EELV ~ 12 meter aperture for an Ares V
For truly large telescopes, we need something more advanced than a cord fold approach
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Shift to a Family of Deployment OptionsRecent analysis driven by the proliferation of diverse missions requiring both large and smaller telescopes have shown that the choice of deployment approach will depend on:
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Primary Mirror Diameter (m)1 2 3 4 5 6 7 8 9 10 11 12
Relative Risk & Cost vs Primary Diameter
Hubble
Spitzer
Stacked HexFan-FoldChord-Fold
JWST
• Size of the primary mirror required for the mission
• Launch constraints
– Total mass
– Launch environment
• Required telescope agility
– Fixed targets or
– Imaging while tracking
• Applicable and available mirror technology
– Need smaller, stiffer segments
– Availability of larger, ultra-light segments
• Acceptable cost and risk
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Telescope Deployment Architecture Approach Should be Optimized for Cost and Mission Needs
2m - 18 Segment PM, 2m Fairing 2m - 7 Segment PM, 2m Fairing 3m - 7 Segment PM, 3m Fairing
3m - 10 Segment PM, 2m Fairing 4m - 10 Segment PM, 2m Fairing 3m - 7 Segment PM, 2m fairing
Depending on manufacturability
of segments
Depending on segment size & Mission Rqmts
Scalable to Very Large
Diameters
Chord-Fold Deployment
Fan-Fold Deployment Robotic Deployment
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Scaling to Very Large AperturesOne of our long term goals has been the development of an efficient deployment approach that would scale to very large telescopes
SAFIR (10m)
2m Segments6m Primary
3m Segments8.5m Primary
3.5m Segments10.5m Primary
1m Segments3m SMD Primary
Scaling in Segment Size
2m Segments10m Primary
3.5m Segments24.5m Primary
Scaling in Number of RingsHybrid Mirror
6m UV/Vis/IRSMD (3m)
● ● ●
Minimal additional structure required for launch Tripod secondary support contributes to PM
stiffness Heritage concept with hardware implementation
experience
Scalability to very larger telescopes Most efficient packaging No outboard mechanisms allowing
minimal shroud diameter
Advantages of Stacked Hex Deployment
28m UV/Vis/IR
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Stowed in EELV 5 m heavy
(Restraint shell removed for clarity)
10 meter, 7 hex segment deployment
scheme
JWST bus subsystem re-use
New telescope payload
Far infrared wavelength detection requires ~ 4 deg K cooling
• Positioning boom• Deploys and positions scope• Thermally decouples scope
from sunshield• Very low frequency, highly
damped jitter isolation• Maintains balance between
mass and pressure centers over large F.O.R.
Lower frequency telescope attachments provide greater observatory flexibility and performance!
SAFIR Observatory Concept
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• Application of NGST High Accuracy Reflector Deployment System (1990)
Stack Deployment Animation
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Thermal And Dynamic Isolation Boom
• Thermal and dynamic isolation boom concept with fine pointing
• Produces ~3 Pi steradian instantaneous field of regard
• Allows for improved momentum management by control of CP/CG
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“Sugar Scoop”
Conical
Advanced Sunshield Approaches
Flat
• The level of thermal stability being demanded by future big telescope missions preclude the use of simple sunshields
• Need to look toward multi-layer or possibly active sunshields
• These too will need to be deployed
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Scaling to Very Large Apertures Long standing analysis and design
confirms that deployment of stacked, Hex segments provides the most efficient approach to scaling to large telescope apertures
Scale the number of deployed rings
Scale the size of the segments
Two basic approaches to scaling segmented telescopes:
Issues
• Deployment of large number of segments
• Largest number of rigid body actuators
• Highest weight ratio• Highest number of
segment prescriptions
Issues
• Highest risk of manufacturability of very large segments
• Requires largest faring diameter
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Stowed Deployed
Lightweight honeycomb sunshield containment shell structure (outer shell and
inner shell)
Stowed four segment deployable truss structure
Spacecraft bus
40 M
17 M
Deployed optical bench truss with aux spar support (low frequency isolation from
bus)
Sunshield provides 60 deg operating cone
3.5 M monolithic primary reflectors with deployable
secondary reflectors
Structurally Connected Interferometer – 40 m
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30-m spherical primary mirror telescope
30 meter spherical primary mirror
Secondary (f/d = 1.79)
Spherical corrector assemblySpherical corrector assembly
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30 m Assembled Spherical Telescope concept
Bus and telescope
rendezvous and dock here
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30 M Spherical Telescope Observatory Concept
Five EELV heavy launches Total lift capability ~ 40,000 Kg’s Observatory SWAG ~ 27,000 Kg’s Weight margin ~ 48%
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Courtesy of Jack Frassanito & Associates and Dr. Harley Thronson
On-orbit Servicing
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Key Technologies Enabling Next Generation Space Telescopes Rapid, low cost fabrication of ultra-light
weight primary mirror segments Eliminates time consuming grinding and polishing
Several approaches including vapor deposition of nanolaminates bonded to actuated substrates
Active figure control of primary mirror segments High precision actuators
Surface parallel actuation eliminates need for stiff reaction structure (SMD)
High speed wavefront sensing and control High density figure control enables very light weight
mirror segments
High speed, active while imaging WFS&C allows for rapid slew and settle and earth imaging
Highly-packageable & scalable deployment techniques Deployment architecture should take advantage of light
weight mirrors
Active control for light weight structural elements to supply good stability Reduces weight required for vibration and thermal control
Image Plane & WFS&C Sensor
Imaging FPA(4096 X 40968m pixels)
Model SensorScene Tracker Focal PlaneFine Figure & Phase Sensor
Beam Footprint at FPA Plane
Nonolaminate on Mandrel
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Conclusions
Space telescopes with 20-meter and larger apertures are within affordable reach by the mid-2020’s
To achieve this we need to initiate a technology development plan that thoroughly explores the trade options and identifies and matures the enabling technology
We need the sustained technology development funding to mature the technology
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