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
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
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Types of Reflectors & Support
This is an arbitraryidentification systemj t f di ijust for discussion
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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
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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 )
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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.
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Identify 3 Optical Designs of Interest
Data points for SKA cost modelInform Tradeoff symmetric vs offset
B1D1
E1
E2
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Select 3 Designs for CostingFEA Design & Costing for HMR to meet survival requirements
HMR = Hydroformed Metal Reflectory
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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
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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
US SKA Consortium, Madison, 2008-11-17 Matt Fleming slide 12 of 35
TDP Antenna Cost (summary estimate )
a little more detaila little more detail
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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
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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
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More
Machined Flange
Consider use of ring forgings
Alternate foundationAlternate foundation concepts are still under consideration
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Turret Head & Az drives
Deliverable AssyDeliverable Assy
Machinedfabrication
Double row ang contactOr crossed rollerWith oil bath
Lubrication 60 months
Az drivemodules
Lubrication 60 months
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El Bearings & El drive
Bearing choices
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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
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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.
US SKA Consortium, Madison, 2008-11-17 Matt Fleming slide 30 of 35
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.
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