Copyright 2007 Northrop Grumman Corporation 1 Large Deployed and Assembled Space Telescopes November...

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


Agenda

Expectations

Deployable Observatories

Very Large Observatories

Technology Needs


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


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


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


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:

Man

ufac

turin

g, L

aunc

h &

Dep

loym

ent R

isk

and

Cos

t

Monolith

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


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


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


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


• Application of NGST High Accuracy Reflector Deployment System (1990)

Stack Deployment Animation


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


“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


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


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


30-m spherical primary mirror telescope

30 meter spherical primary mirror

Secondary (f/d = 1.79)

Spherical corrector assemblySpherical corrector assembly


30 m Assembled Spherical Telescope concept

Bus and telescope

rendezvous and dock here


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%


Courtesy of Jack Frassanito & Associates and Dr. Harley Thronson

On-orbit Servicing


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


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

Copyright 2007 Northrop Grumman Corporation 1 Large Deployed and Assembled Space Telescopes November...

Documents

Transcript of Copyright 2007 Northrop Grumman Corporation 1 Large Deployed and Assembled Space Telescopes November...