CURRENT SKA TDP ANTENNA DESIGNANTENNA … · Jack Welch RShltRoger Schultz ... US SKA Consortium,...

CURRENT SKA TDP ANTENNA DESIGNANTENNA DESIGNSKA 2010 Meeting, Manchester, UK

March 22, 2010Matt Fleming

Contributions from

Jack WelchR S h ltRoger SchultzGordon Lacy

Antenna Design Drivers

These will lead to specifications: ???

1 Mush achieve survival.( 100 mph wind )

2 Low cost per unit area of aperture2 Low cost per unit area of aperture. ( good sky coverage ) ( installed )

( low cost materials, low mass design, low fabrication labor ) ( favors symmetric )

3 Very low operational cost for a 30 year life( f i t i it i d )( very few maintenance visits required )

4 Frequency range of 0.3 to 10 GHz with WBSPF( 3.5m Gregorian secondary ) ( favors offset )

5 E ll t A / T5 Excellent Ae / Tsys.( accurate surfaces, controlled spillover, low diffraction ) ( favors offset )

6 Exceptional dynamic range.( very rigid surfaces, very good pointing, )( very rigid surfaces, very good pointing, )

US SKA Consortium, Madison, 2008-11-17 Matt Fleming slide 2 of 35

What Antenna Design to Choose


Basic fabrication cost driversTo achieve specific device function

Raw material costs. ( what the planet provides & our ability recover it )

Labor cost ( our physical size & strength, social & economic environment )

Technology. ( application of intellect to use of materials labor & energy )

Number of units needed. ( investment in tooling )

Transportation. ( where is it made & where is it used ) Patriot dishmaterial is sometimes

traded for labor

Understanding these items for every design allows engineering shortcutsWe cannot do detailed design on every possible design approach


Types of Reflectors & Support

This is an arbitraryidentification systemj t f di ijust for discussion


Primary as a monocoque elementSingle shell or stressed skin

•Reflector edge support by itself preserves accuracy extremely well.•The reflector surface can act as the structural front side of a deeper system.•Rim edge and center support works better if the center has axial flexibility

Single shell or stressed skin

•Rim edge and center support works better if the center has axial flexibility.•The concept can work for symmetric or offset designs.

J t i l h llJump to single shellOn Az-El mount


ATA Implementation

•A frame & spar system gives good edge & center support with an open center.•Wind & gravity moment loads are reduce with Az & El near the shell center.Th t t ll t t t h d t b t d l t h ll•The support system allows a compact turret head to be nested close to shell.

•A compact turret head can contain almost all the precision machining needs.•A relatively simple pipe pedestal can support the turret head. ( wind & thermal )


JPL, DSN, Prototype

•A 6.1m diameter symmetric shell can be made with only a 3mm thickness.•The surface accuracy can be quite high.•A study showed 3mm alum 3003 will have good repeatability in production•A study showed 3mm alum 3003 will have good repeatability in production .•Another study showed 3mm alum 3003 can be extended to a 12m symmetric.


Identify 3 Optical Designs of Interest

Data points for SKA cost modelInform Tradeoff symmetric vs offset

B1D1

E1

E2


Select 3 Designs for CostingFEA Design & Costing for HMR to meet survival requirements

HMR = Hydroformed Metal Reflectory


Canada NRC DRAO CART Project

NRC = National Research CouncilDRAO = Dominion Radio ObservatoryCART = Composite Application Radio Telescope

Prototype 10m complete.Symmetric with Core, Beams & Hub.SKA Memo 116 costing information Starting to investigate

Off t V3g

Offset monocoque V3


TDP Antenna Cost ( summary estimates )

( survival design shown )( add 15% for performance design )( survival design shown )( add 15% for performance design )

8% 15%0% 0% 11%

Adding 15% 113,000 122,000 130,000 137,000 152,00025%

Adding 15% 113,000 122,000 130,000 137,000 152,000


TDP Antenna Cost (summary estimate )

a little more detaila little more detail


Costing Allows Selection

Optics 42 used for costing PAF = Phased Array Feed

Preffered mechanical configuration Acceptable optical configuration

2 Gregorian feeds with rotary indexer & possibly a PAF

Shown with Feed Up but optics can be the same with Feed Down

Note feed support locations


Computed RMS0.008 inches

0.20 mm



0.33 mm



0.03 mm


Some FRP Deflection ResultsVery preliminary 15m thin shell surface & support

Consult Gordon Lacy DRAO for additional interpretationOrientations are arbitraryOrientations are arbitrary

Dish 2.0 mm ppEl 15

Dish 4.0 mm ppEl 90


Specifications 1 of 2


Specifications 2 of 2


Beginning to work on details


Opportunity to Collaborate


Pedestal Mount & Frame


Alt


More

Machined Flange

Consider use of ring forgings

Alternate foundationAlternate foundation concepts are still under consideration


Turret Head & Az drives

Deliverable AssyDeliverable Assy

Machinedfabrication

Double row ang contactOr crossed rollerWith oil bath

Lubrication 60 months

Az drivemodules

Lubrication 60 months


El Bearings & El drive

Bearing choices


Encoders & Pointing


Cable Wraps & Enclosures

Current Az wrap envisioned to have only 5 elements at +/- 270°Power 1, Power 2, Ground, Control fibers, Signal fibers

Cooling is important to consider early in the design


Feed Indexer

No concepts worth showing yet

Some comments:

It will be expensiveIt will introduce additional deflectionIt will introduce additional pointing considerationsIt will require more cables and cable wrap loading

I look at the ATA WBSPF with 1.0 to 10.0 GHz, weighing 40 Kg and wonder If we gave 0 3 to 1 0 GHzweighing 40 Kg and wonder If we gave 0.3 to 1.0 GHz to another solution then the dish is much simpler.


Issues to rememberwhile Considering Cost Resultswhile Considering Cost Results

These cost numbers are critical for SKA decision making.

Antenna based on design to achieve survival with a 3mm shell.

As a consequence holds decent surface RMS for, no sun, no wind.

Current itemized estimate believed to be quite good.

C t ill i d i i i d t hi fCosts will rise as design is improved to achieve performance.

Larger radius of curvature on primary is higher risk for hydroforming.


Questions


CURRENT SKA TDP ANTENNA DESIGNANTENNA … · Jack Welch RShltRoger Schultz ... US SKA Consortium,...

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