SKA TDP & CART 15m (DVA-1) ANTENNA DESIGN 11 US SKA Consortium Meeting at Arlington VA June 3-4, 2010 Matt Fleming Contributions from Jack Welch Roger Schultz Gordon Lacy Lynn Baker German

Antenna Design Drivers 1Must achieve survival. ( 100 mph wind ) 2 Low cost per unit area of aperture. ( good sky coverage ) ( installed ) ( low cost materials, low mass design, low fabrication labor ) ( favors symmetric ) 3Very low operational cost for a 30 year life ( very few maintenance visits required ) 4Frequency range of 0.3 to 10 GHz with WBSPF ( 4.0m Gregorian secondary ) ( favors offset ) 5Excellent A e / T sys. ( accurate surfaces, controlled spillover, low diffraction ) ( favors offset ) 6Exceptional dynamic range. ( very rigid surfaces, very good pointing, ) pt source sensitivity survey survey speed Performance vs Cost Tradeoffs These will shape specifications. US SKA Consortium, Arlington, Matt Fleming slide 2 of 28

Design Driver 2, Cost Raw material costs. ( fairly constant world wide )( a good design is light weight ) Labor cost. ( varies by type and location based on economic and social conditions ) For some designs material is often traded for labor Technology. ( application of intellect to use of material, labor & energy ) Number of units needed. ( investment in tooling ) Transportation. ( where made, where assembled, where installed ) Basic fabrication cost drivers Remote fabrication of smaller elements allows use of global labor competition. Understanding these items for every design allows engineering shortcuts We cannot do detailed design on every possible design approach US SKA Consortium, Arlington, Matt Fleming slide 3 of 28

What is New We have an aperture diameter specified at 15m. We will maintain the offset high configuration for now. We have a new approach for the primary reflector. (CART) We have better relative cost info from 12m for tradeoff decisions. We have a better understanding system operations cost. (SPDO) We have a well defined shaped optics design. We have new specifications. US SKA Consortium, Arlington, Matt Fleming slide 4 of 28

Specifications 1 of 2 US SKA Consortium, Arlington, Matt Fleming slide 5 of 28

Specifications 2 of 2 US SKA Consortium, Arlington, Matt Fleming slide 6 of 28

Single piece reflectors often have low labor cost relative to alternate designs. 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. The concept can work for symmetric or offset designs. Primary as a monocoque element Single shell or stressed skin Jump to single shell On Az-El mount US SKA Consortium, Arlington, Matt Fleming slide 7 of 28

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. 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 ) ATA 6.1m Implementation US SKA Consortium, Arlington, Matt Fleming slide 8 of 28

The TDP 15m Implementation Spars 13 members Center frame 16 members Secondary & feed support 22 members 2,400 4,950 7,350 10,050 10,250 14,450 Total Secondary Assy Total Primary Assy Total on El Bearing Total on Az bearing Total Turret Flange Total Antenna Preliminary Weight Est ( Kg ) Materials & sections can be adjusted US SKA Consortium, Arlington, Matt Fleming slide 9 of 28

Hydroforming has low production cost and is a fast process. Hydroforming a 12m symmetric is considered quite possible at 3mm thickness. Hydorforming a 15m x 18m offset is definitely more difficult to predict. Manufacturing repeatability is better with thickness, worse with flatness. Plastic deformation FEA is needed to predict 15m repeatiblility. ( Ohio State ) Tooling will be very expensive. ( 12m was considered to be 2M$ ) (DVA-1) Hydroforming Big Reflectors US SKA Consortium, Arlington, Matt Fleming slide 10 of 28

Information from Composite Investigations DRAO = Dominion Radio Observatory CART = Composite Application Radio Telescope Prototype 10m complete. Symmetric with Core, Beams & Hub. SKA Memo 116 costing information Starting to investigate Offset monocoque V3 Canada DRAO CART Project and South Africa MeerKAT Project have generated cost and performance information for composite on site reflector fabrication. US SKA Consortium, Arlington, Matt Fleming slide 11 of 28

HM & FRP shells are similar Both hydroformed metal and fiber reinforced plastic create good monocoque structures FRP can replace HM reflectors and can provide edge support Rim beam & spars favored over shell support US SKA Consortium, Arlington, Matt Fleming slide 12 of 28

Additional Views US SKA Consortium, Arlington, Matt Fleming slide 13 of 28

Beam Path Close approximation of TDP shaped optics design Feeds US SKA Consortium, Arlington, Matt Fleming slide 14 of 28

Structural Simplicity Triangular deep trusses good Cured beams and curved shells bad Tubular structures are very efficient at handling bending and torsion More about PAF position later US SKA Consortium, Arlington, Matt Fleming slide 15 of 28

Secondary & Feed Support Light weight structure 180 Kg Heavier structure US SKA Consortium, Arlington, Matt Fleming slide 16 of 28

TDP & CART Team Collaboration Gordon Lacy is beginning to run FEA optimizations on reflectors & supports Matt Fleming beginning to analyze and detail 15m mount and drive systems US SKA Consortium, Arlington, Matt Fleming slide 17 of 28

Deliverable Antenna Elements Primary not shown It is an on site fabrication Pedestal Turret head Secondary Primary center frame Electronics enclosures Secondary and feed support Feed and indexer US SKA Consortium, Arlington, Matt Fleming slide 18 of 28

Pedestal Fabrication Consider use of ring forgings Machined Flange Alternate foundation concepts are still under consideration US SKA Consortium, Arlington, Matt Fleming slide 19 of 28

Turret Head Assembly Deliverable Assembly Includes az drives, bearings, encoders, electronics US SKA Consortium, Arlington, Matt Fleming slide 20 of 28

Primary Center Frame Pentagonal frame shown Machining of this portion may be necessary and a little expensive Tubes all have parallel end cuts US SKA Consortium, Arlington, Matt Fleming slide 21 of 28

Turret Head & Az drives Deliverable Assy Double row ang contact, Or crossed roller, or 4 pt, With oil bath Lubrication 60 months Machined fabrication Az drive modules US SKA Consortium, Arlington, Matt Fleming slide 22 of 28

Azimuth Drives Dual idler supported pinion Multiple modular drives Access to drives Full oil bath lubrication for 60 month period RFI control US SKA Consortium, Arlington, Matt Fleming slide 23 of 28

El Bearings & El drive Gravity loading helpful. Low clearance important Bearing choices tuff. Currently envision a custom actuator US SKA Consortium, Arlington, Matt Fleming slide 24 of 28

Encoders & Pointing Attachment to reflector surface away from loaded areas Long light weight tube might be problematic Both encoders can be interior to the turret head allowing environmental protection and easy cabling. Limit switch gearing Az tube could extend to ground for higher accuracy, but ……. Addition of tilt meter and accelerometer devices will enhance performance Unatainium box on back of dish is the best option US SKA Consortium, Arlington, Matt Fleming slide 25 of 28

Feeds & Indexer & PAF Space for PAF implies two leg support frame Pivot & structural support ATA in glass PAF shown 1m x 1m x 1m PAF at secondary focus still under consideration Lindgren in can US SKA Consortium, Arlington, Matt Fleming slide 26 of 28

Feed Indexer Concepts Consider cable wraps, precision, access, dirt. sector type.turret type. linear slide. Quick release fast exchange for feeds. Position repeat to 1.0mm. US SKA Consortium, Arlington, Matt Fleming slide 27 of 28

Questions US SKA Consortium, Arlington, Matt Fleming slide 28 of 28

12m Computed RMS inches 0.20 mm US SKA Consortium, Arlington, Matt Fleming slide 29 of 28

12m Computed RMS inches 0.33 mm US SKA Consortium, Arlington, Matt Fleming slide 30 of 28

12m Computed RMS inches 0.03 mm US SKA Consortium, Arlington, Matt Fleming slide 31 of 28