us ska tdp antenna design progress us ska awg meeting may 6, 2009, los angeles. california matt...

US SKA TDP Antenna Design Progress

US SKA AWG MeetingMay 6, 2009, Los Angeles. California

Matt Fleming

Contributions from

Jack WelchRoger Schultz

Sandy WeinrebGerry Harp

US SKA Consortium, Madison, 2008-11-17 Matt Fleming slide 2 of 27

Summary Reflector Types


Type G ( integral surface, composite, CART, MeerKAT )

This configuration may be worth pursuing because it allows nesting the turning head close to the vertex


Type F ( integral surface metal, Patriot, Vertex, Etc )


Type D & E ( ATA, JPL, Andersen, Others )

This is the area of most interest for large hydroformed shells. We have investigated Lots of backstructures that allow the turning head in close.


Rigid Circular Support Beam Study

In this study the dish is equipped with a minimal rim beam and supported by a rigid circular beam of various diameters. Stresses are generated by 100 mph side wind from the left.

Really type B support


Rigid Circular Support Beam Study

It seems reasonable to conclude that support at a diameter of less than 65 % will result in over stressed material. Also, it is likely that secondary reflector or feed support legs will need support from near the rim.


Rim Beam & Spars Study

In this study the dimensions of a rectangular rim beam are varied to maintain acceptable stress while the number of spars is changed. The spars converge at a point 5.0 meters behind the vertex of the dish. The rim beam depth is 2 X it’s width. Stresses are generated by 100 mph side wind from the left while pointed at zenith.


Rim Beam & Spars Study

It seams reasonable to conclude that only 5 or 6 spars are needed for survival at zenith stow. Also the use of a tripod or quadripod may be a factor in the number of spars chosen.


12m dia, 4.5mm thick, bare Al, full sun, no wind.Temperature shown, 70 to 124F, but deflection matches. ( very preliminary )


Various backstructures examined.Various important issues discovered.Surface buckling revealed is some cases.


Backstructure Spreadsheet

Contains the following sort of comparisonfor all the various designs

Reflector weightBackstructure weightNumber of members & jointsSlenderness ratiosPeak stress levels for various loads


So, this is our current favoriteD1-40810

It is important to realize this concept will work forsymmetric or offset with minimal axis offsets


FEA on our current favorite design looks good for survival

Developing Load & ReactionPrograms for El bearings & Jack



Antenna Optics and Mount Configurations

All other designswill be comparedto this design.


Cost Increase

Reflector 0 %

Pedestal 0 %

A-E Offset 0 %

Total 0 %

Performance Loss

Blockage 3.1 %

Sky 10 %

Spillover

Spacing (min) 0 %

Symmetric, Cassegrain, Az-El% of ATATotal cost

32 %

7 %

20 %


Symmetric, Gregorian, Az-El

Cost Increase

Reflector 0 %

Pedestal 0 %

A-E Offset 0 %

Total 0 %

Performance Loss

Blockage 3.1 %

Sky 10 %

Spillover

Spacing (min) 11 %

% of ATATotal cost

32 %

7 %

20 %


Symmetric, Prime, Az-El

Cost Increase

Reflector 0 %

Pedestal 0 %

A-E Offset 0 %

Total 0 %

Performance Loss

Blockage 2.3 %

Sky 10 %

Spillover

Spacing (min) 69 %

% of ATATotal cost

32 %

7 %

20 %


Offset, Gregorian, low, Az-El, 22

22

Cost Increase

Reflector 20 %

Pedestal 26 %

A-E Offset 20 %

Total 12.2 %

Performance Loss

Blockage 0 %

Sky 38 %

Spillover

Spacing (min) 42 %

% of ATATotal cost

32 %

7 %

20 %


Offset, Gregorian, low, Az-El, extended

Cost Increase

Reflector 20 %

Pedestal 28 %

A-E Offset 32 %

Total 14.8 %

Performance Loss

Blockage 0 %

Sky 10 %

Spillover

Spacing (min) 63 %

% of ATATotal cost

32 %

7 %

20 %


Offset, gregorian, low, Az-El, tilted ped

Cost Increase

Reflector 20 %

Pedestal 28 %

A-E Offset 20 %

Total 12.4 %

Performance Loss

Blockage 0 %

Sky 33 %

Spillover

Spacing (min) 42 %

% of ATATotal cost

32 %

7 %

20 %


Offset, Gregorian, high, Az-El

Cost Increase

Reflector 20 %

Pedestal -6 %

A-E Offset -4 %

Total 5.2 %

Performance Loss

Blockage 0 %

Sky 10 %

Spillover

Spacing (min) 11 %

% of ATATotal cost

32 %

7 %

20 %


SKA Memo 63 Proposed by Sandy & Roger


Extra slide, just for discussion

Clear Aperture


Support SystemsOffset with 0.5m Clearance


Support SystemsIndexer position


Offset Low


Stow issues

12° Elevation


30° Elevation


45° Elevation


60° Elevation


75° Elevation


90° Elevation


45° Elevation


ATA Pedestal, Shields


ATA Pedestal, Unshielded, Temps



ATA Pedestal, Shielded, Temps


ATA Pedestal, Shielded, Tilt


ATA Temps, various surfaces

us ska tdp antenna design progress us ska awg meeting may 6, 2009, los angeles. california matt...

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