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CURRENT SKA TDP
ANTENNA DESIGN 10
DVA1 Meeting at NSF Arlington VA
April 15-16, 2010
Matt Fleming
Contributions from
Jack Welch
Roger Schultz
Gordon Lacy
Antenna Design Drivers
1 Must 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 )
3 Very low operational cost for a 30 year life( very few maintenance visits required )
4 Frequency range of 0.3 to 10 GHz with WBSPF( 3.5m Gregorian secondary ) ( favors offset )
5 Excellent Ae / Tsys.( accurate surfaces, controlled spillover, low diffraction ) ( favors offset )
6 Exceptional dynamic range.( very rigid surfaces, very good pointing, )
These will lead to specifications: ???
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 2 of 43
Basic fabrication cost drivers
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 )
Understanding these items for every design allows engineering shortcuts
We cannot do detailed design on every possible design approach
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 )
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 3 of 43
Note on Transportation
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 4 of 43
Physical size of antenna elements will influence transport cost.
Remote fabrication of smaller elements allows use of global labor competition.
Remote fabrication usually means greater on site assembly labor.
Onsite fabrication of large elements can allow lower on site assembly labor.
Non modal transport is also possible, but likely more expensive.
Types of Reflectors & Support
This is an arbitrary
identification system
just for discussion
This slide just a reminder about initial choices
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 5 of 43
•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 elementSingle shell or stressed skin
Jump to single shell
On Az-El mount
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 6 of 43
•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 Implementation
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 7 of 43
•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 .
•Another study showed 3mm alum 3003 can be extended to a 12m symmetric.
JPL, DSN, Prototype
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 8 of 43
Identify 3 Optical Designs of Interest
B1
E2
D1E1
Data points for SKA cost model
Inform Tradeoff symmetric vs offset
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 9 of 43
Select 3 Designs for Costing
FEA Design & Costing for HMR to meet survival requirements
HMR = Hydroformed Metal Reflector
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 10 of 43
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.
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 11 of 43
TDP Antenna Cost ( summary estimates )
8% 15%0% 0% 11%
Adding 15% 113,000 122,000 130,000 137,000 152,000
25%
( survival design shown )( add 15% for performance design )
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 12 of 43
TDP Antenna Cost (summary estimate )
a little more detail
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 13 of 43
Optics 42 used for costing
2 Gregorian feeds with rotary
indexer & possibly a PAF
Shown with Feed Up but optics can
be the same with Feed Down
Costing Allows Selection
PAF = Phased Array Feed
Preffered mechanical configuration
Acceptable optical configuration
Note feed support locations
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 14 of 43
Computed RMS
0.008 inches
0.20 mm
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 15 of 43
Computed RMS
0.013 inches
0.33 mm
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 16 of 43
Computed RMS
0.001 inches
0.03 mm
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 17 of 43
HM & FRP shells are similarBoth hydroformed metal and fiber reinforced
plastic create good monocoque structures
FRP can replace HM reflectors
and can provide edge support
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 18 of 43
Specifications 1 of 2
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 19 of 43
Specifications 2 of 2
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 20 of 43
Beginning to work on details
Rain snow ice
Survival wind
Security and vandalism
Ease of maintenance
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 21 of 43
Additional Views
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 22 of 43
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
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 23 of 43
Pedestal Mount & Frame
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 24 of 43
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
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 25 of 43
Pedestal Fabrication
Consider use of
ring forgings
Machined Flange
Alternate foundation
concepts are still under
consideration
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 26 of 43
Transport Check
Looks good for global sourcing
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 27 of 43
Turret Head Assembly
Deliverable Assembly
Includes az drives, bearings, encoders, electronics
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 28 of 43
Transport Check
Note 3.1 m secondary shown
Looks like a little larger is possible.
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 29 of 43
Primary Center Frame
Pentagonal frame shown
Machining of this portion
may be necessary and a
little expensive
Tubes all have
parallel end cuts
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 30 of 43
Transport CheckNot so good
Design for assembly or ship prepared
kit to near site fabricator for final weld
and paint then transport to site.
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 31 of 43
Secondary Support Frame
FRP fabrication may be ideal for
rear section from the primary lower
rim to the feed support plane.
If made from metal, we will
consider some on site
assembly.
More information is needed
about feed support
requirements.
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 32 of 43
Transport CheckNot good
Density very poor
Reconsider this
Design for assembly or ship prepared
kit to near site fabricator for final weld
and paint then transport to site.
Electronics
enclosure
shown
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 33 of 43
Turret Head & Az drives
Deliverable Assy
Double row ang contact
Or crossed roller
With oil bath
Lubrication 60 months
Machined
fabrication
Az drive
modules
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 34 of 43
Azimuth Drives
Dual idler supported pinion
Multiple modular drives
Access to drives
Full oil bath lubrication
for 60 month period
RFI control
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 35 of 43
El Bearings & El drive
Gravity loading helpful.
Low clearance important
Bearing choices tuff.
Currently envision a
custom actuator
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 36 of 43
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
may enhance
performance
Unatainium box on back of
dish is the best option
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 37 of 43
Cable Wraps & Enclosures
Cooling is important to
consider early in the design
Current Az wrap 540 and envisioned with only 5 elements
Power 1, Power 2, Ground, Control fibers, Signal fibers
Security, access, swapping
Current El wrap 75
envisioned with many elements
Power 1, Power 2, Ground,
Control fibers, Signal fibers
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 38 of 43
Feeds and Indexer 1
Space for PAF implies two
leg support frame
Pivot & structural support
Lindgren in canATA in glass
Track ?
PAF shown
1m x 1m x 1m
Maybe sector
not turntable
Min angle
on wraps
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 39 of 43
Feeds and Indexer 2
Some comments:
It will be expensive.
It will introduce additional deflection.
It will introduce additional pointing considerations.
It will require more cables and cable wrap loading.
Is it really possible to imagine future feed upgrades?
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 GHz
to another solution then the dish is much simpler.
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 40 of 43
Mount Discussions
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 41 of 43
Issues to remember
and questions remaining
For the SKA TDPFeed high – feed low – feed shrouds ?
Aperture diameter ?
Optics design – shaping – illumination angle ?
PAF at prime – PAF at secondary – PAF at all ?
Diffraction from secondary support braces and other items ?
Is hydroforming reliable for shallow 12m & 15m offsets ?
Do we plan to prototype and develop the HM process ?
US SKA Consortium, Madison, 2008-11-17 Matt Fleming slide 42 of 35
For DVA1Questions above plus.
Does FRP represent HM well enough ?
HM secondary ?
Do we need the TDP mount ?
Do we need an indexer or just mounting fixture plate ?
If 12m is chosen, list what is unanswered for 15m.
Questions
DVA1, NSF, Arlington, 2010-04-16 Matt Fleming slide 43 of 43