Paul Turin FIELDS iPDR – TRL6 1

SPP-FIELDSTRL 6 Testing

Paul Turin

pturin@ssl.berkeley.edu

Paul Turin FIELDS iPDR – TRL6 2

TRL6 Philosophy

• The TRL of the Antenna assembly is a matter of verifying that the materials selected for the Antenna will perform as expected.

• The mechanical design and deployment of the Antenna is a straight forward application of mechanisms, design techniques and actuators with a long history of successful use at UCB/SSL.

• Subsequent mechanism engineering development is not considered part of the TRL promotion

Paul Turin FIELDS iPDR – TRL6 3

SSL Mechanism Heritage

Paul Turin FIELDS iPDR – TRL6

Overview

SPF_SYS_003 FIELDS Technology Development Plan has three test phases:

1. Basic material testing to determine the thermal and optical properties.• Outgassing • Optical properties• Thermal conductivity of metals and insulators• Electrical resistance of insulators

2. Thermal distortion testing, to determine whether residual stresses in the material will cause the whips to distort after being subjected to high temperatures.

3. Testing of Thermal Test Models (TTMs) to verify the analytical thermal predictions for the antenna, in the expected radiation environment, and for BOL and EOL performance.• Solar Simulator Testing -- Thermal Test Models• Furnace Testing -- material compatibility

Refractory metals were procured early in Phase B for testing and qualification. Flight components will be built from same lot.

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Paul Turin FIELDS iPDR – TRL6

Phase 1 Materials Test Matrix

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RT = Room TemperaturesHT = Hot Expected TemperaturesSRI = Southern Research InstituteVPE = Vacuum Process EngineeringPROMES= PROcess Materials and Solar Energy

M. Diaz-Aguado 6FIELDS iPDR – Thermal

Phase 1: Materials Testing

• Outgassing – Insignificant mass loss below 1500°C ~=0.3% TML/24hr at max

temp+100°C margin• Optical properties

– During APL BRDF testing found we need to randomize shield surface for uniform optical scattering. Material Scotch-Brited w/ random orbital sander.

– BOL/EOL – no difference from BRDF pre/post GRC 100hr hot testing– Absorptivity and emissivity

• APL extrapolated from room temp data:• Compares well with PROMES data:• We used PROMES values as they are actual data from flight materials at

temperature. We added 100C margin to hot temp predicts.

• Thermal conductivity– Used data collected by SAO for sapphire and alumina – switched to

sapphire– Manufacturer’s data for metals

• Insulator electrical resistivity – Used data from APL and SRI

• Provides adequate isolation at temperature

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Phase 2: Whip Thermal Distortion

Test performed two ways1. SRI: Short sample suspended in furnace

@1400°C, measured tip deflection with camera– Results: extrapolated to 2m length, distortion =

0.5° < 0.8° allocated in alignment budget

2. VPE: 4 x 96” (2.4m) samples

3. heated in vacuum furnace to 1000°C– Results: distortion = 0.3° < 0.8° allocated

in alignment budget

M. Diaz-Aguado 8FIELDS iPDR – Thermal

Phase 3: TTMs

Tested construction and isolation of components at temperature and provided data for thermal model correlation• For the purposes of correlating our thermal

model, we broke the test into two parts: 1. Whip and its thermal/electrical isolator

• Maximum temperature deviation from model 13°C (1%)

2. Stub and heat shield• Maximum temperature deviation from model 9°C

(<1%)

• Achieved good correlation (max predict 1303°C), but discovered partial melting of clamp/screw combination

• Subsequent furnace testing isolated problem to Ti used for heat shield clamp forming eutectic with steel screws– Replaced Ti clamp with Moly TZM which solved

problem.– New problems: Ti Stub tube softened and reduced

clamping force, was bent by DTE.

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Phase 3: TTMs cont.

• TTM testing results:– Moly TZM solved clamp melting issue– Ti not suitable for stub – too soft at

expected temps– DTE caused bending of Stub – Solutions:

• Switch to Nb C-103 tubing (with moly TZM for backup)

• Tubing has been ordered in both materials (delivery mid Dec)

• Added flexures to shield mounting• Based on performance of Nb and

Moly in other components, we don’t expect any more issues, but will repeat furnace test with new materials before mPDR.

• Small mass penalty of 20g/antenna (already included in latest CBE)

Paul Turin FIELDS iPDR – TRL6

Future Testing

• Expect to Finalize TRL-6 with one more test at VPE (Dec/Jan)– Material compatibility test -- Niobium C103 and Molybdenum

TZM Stubs– Verify added flexures eliminate bending

• Post TRL-6 Testing (TTM- 3, test at Harvard SAO)– V-shaped shield test and high temperature conductance (January 2014)

with 4 light sources in 6° beam. Allows us to correlate higher fidelity TTM

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BACKUP SLIDES

Paul Turin FIELDS iPDR – TRL6

• Current analysis shows max heat shield and whip temp of 1315°C

• Outgassing studies (tested at NASA Glenn Research Center)– Minimal mass loss at 1403°C (100°C margin) -- about 0.3% 24hrs for

comparison to ASTM E595

Outgassing Test

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Red is temperatureBlue is mass change

1403°C

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Optical testing at APL

• APL developed model to compute temperature dependent absorptance/emittance

• Used room temp. BRDF to measure reflectance• Measured DC resistivity as a function of temperature• This data used to develop model of optical constants

APL then computes a/e as a function of temperature

• APL tested coupons in BRDF, pre-/post- heating at GRC• Heating cycle used: 100 hour profile at 1450C• Representative of BOL/EOL condition of material• Reflectance data exhibits only minor changes between

BOL/EOL• Suggests EOL a/e is within margin assumed in analysis

• The APL model was based on the unrandomized coupons• It was on their to-do list to model the randomized

surface finish.• Not done as far as we know.

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Optical testing at APL cont.

• Tested at APL, Nb mill-finished samples (testing at room temperature – analysis to extrapolate to temp) – Bi-directional Reflectance Distribution Function (BRDF) and

Hemispherical Directional Reflectance (HDR)

0 500 1 103

1.5 103

2 103

0

2

4

6

8

10

12

Temperature [K]

Alp

ha/e

psil

lon

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Optical Properties: Surface Finish Effects

• BRDF Room Temperature Measurements (APL) Niobium C103

Roughened Niobium C103

• Untreated surface– Emissivity changed depending on the

sample orientation (vertical vs. horizontal)

• Roughened surface– Emissivity constant at all orientations

Paul Turin FIELDS iPDR – TRL6

Optical Properties

• Test conducted at PROMES Solar Simulator chamber at expected temperatures– Total Hemispherical optical properties for randomized surface

finish sample• Linear except at higher angles due to holding fixture• From graph we obtain α=0.54 ε=0.35 at 1330°C (1603.15K)

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Paul Turin FIELDS iPDR – TRL6

Insulator Resistivity at High Temperatures

• Original electrical isolator material choice was alumina• Was found to be a poor electrical isolator @ temp – switched

to sapphire• Graph below shows APL tested data and SRI tested data • Predicted values acceptable – to be confirmed

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1.E+00

1.E+02

1.E+04

1.E+06

1.E+08

1.E+10

1.E+12

1.E+14

1.E+16

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Resi

stivi

ty (

ohm-

cm)

Temperature (⁰C)

Resistivity of Insulators vs TemperatureSapphire - APL Model Alumina - APL Model

Sapphire C-axis - SRI Sapphire Random Axis - SRI

Paul Turin FIELDS iPDR – TRL6

Insulator Thermal Conductivity at High Temps

• We are using data from Harvard SAO (SRI)

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Metals Thermal Conductivity at High Temps

• We are using data from metal suppliers

Paul Turin FIELDS iPDR – TRL6

Whip Thermal Distortion

• Test – I @ SRI• 26” long tubes • Heated 6.6” section in vacuum furnace• Measurements were made in Photoshop based on the images

captured at the tip of these three tubes at 1400 °C (70 °C margin), for 40 min.

• Total distortion for a 2m long whip calculated to be < 0.5°, < 0.77° allocated

 

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Paul Turin FIELDS iPDR – TRL6

• TEST II @ VPE – Long TV with temperatures up to 1000°C

• Four Nb 96” (2.4m) tubes heated to 1000°C for 1hr (max oven temp)• Maximum distortion seen <0.4°, < 0.77° allocated

Whip Thermal Distortion

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3 meter T-VAC

Paul Turin FIELDS iPDR – TRL6

Odeillo Facilities

• PROMES solar test facility can produce SSP flux levels, but with +-80° beam

SunHeliostats

Parabola

Tower – Focal Point

Heat Flux controlled by opening doors

Paul Turin FIELDS iPDR – TRL6

Odeillo Facilities- PROMES Chamber

Water Cooled Air Cooled

Heat Flux controlled by opening doors

Paul Turin FIELDS iPDR – TRL6

Thermal Choke TTM

Whip Disk

Whip Choke

Choke

Water Cooling

Paul Turin FIELDS iPDR – TRL6

Thermal Shield TTM

Shield

Clamp

Bracket

Stub

Water Cooled

Paul Turin FIELDS iPDR – TRL6

TTM Shield Lessons Learned

• Melting of silver coating on bolts– Might have created gaps

on joints at high temperatures

• Rapid heating/cooling– Probably deformed shield

Paul Turin FIELDS iPDR – TRL6

• This test looked at the temp drop in the “thermal choke” – shaded portion of whip

• Test conducted at Odeillo – PROMES chamber at several temperatures– Thermal balance the model at two temperatures of the disk (1455°C and 1040°C)– Maximum discrepancy = 13°C

TTM-1 Choke Thermal Balance

B.C.

Paul Turin FIELDS iPDR – TRL6

• Test conducted at Odeillo – PROMES chamber at several temperatures. Flat heat shield necessitated by ±80° incident beam– Thermal balance the model at one temperature of the disk (1054°C) (limited by weather)– Maximum discrepancy = 9°C

TTM-2a - Shield Thermal Balance

B.C.

B.C.

Found silver plated screws melted at higher shield temperature (1400°C)

Paul Turin FIELDS iPDR – TRL6

Material Compatibility Test I

• Thermal balance data from PROMES testing correlated well, but had apparent melting of silver plating on screws

• Debug materials problem with oven testing (don’t need gradients)– Replaced silver-plated 18-8 screws with 18-8 and A286 screws

• TTM-2b -- Testing shield/bracket/stub assembly– Assembled model of just Stub, Heat Shield and its bracket,

isolators and fasteners– Test chamber at Vacuum Process Engineering (VPE) in

Sacramento– Tested from 750°C and 1150°C (clamp temp) at 100°C increments in

vacuum, observing results between steps– Stainless steel screws used had nickel which forms a eutectic with titanium

• Titanium clamp and screws started melting at 750°C – Titanium bracket still formed eutectics with screws. Rather than try Ti

screws in Ti clamp, we decided to change to refractory alloys for the hottest components.

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Paul Turin FIELDS iPDR – TRL6

Material Compatibility Test II

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• TTM-3a -- Changed to 2 molybdenum TZM clamps and screws, and flight peaked shield geometry

• Testing shield/bracket/stub assembly– Test chamber at VPE in Sacramento– Tested at 750°C in vacuum with stub– Maximum temperature from titanium stub in the

model (100°C margin from model)– No signs of melting or material interactions– Shield-Stub clamps loose

• Testing shield/bracket assembly– Test chamber at VPE– Removed stub from assembly– Testing assembly to temperatures of 1150°C – Maximum temperature from bracket in the model

(100°C margin from model)– No signs of melting or material interactions

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Material Compatibility Test II cont.

• 750C test:– No signs of melting or material interactions– Softening of titanium and differential expansion between stub

and shield loosened clamps• 1150C test:

– No signs of melting or material interactions• Conclusions:

– Ti not suitable for stub – too soft at expected temps– Switch to Nb C-103 (with moly TZM for backup)– Added flexures to shield mounting to accommodate DTE– Tubing is being procured in both materials (expected delivery

mid Dec)– TTM-3b -- Rerun test with these materials late Dec or early Jan– Based on performance of Nb and Moly in other components,

don’t expect any more issues