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SPP-FIELDS TRL 6 Testing

SPP-FIELDS TRL 6 Testing. Paul Turin pturin@ssl.berkeley.edu. TRL6 P hilosophy. The TRL of the Antenna assembly is a matter of verifying that the materials selected for the Antenna will perform as expected.

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SPP-FIELDS TRL 6 Testing

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  1. SPP-FIELDSTRL 6 Testing Paul Turin pturin@ssl.berkeley.edu

  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

  3. SSL Mechanism Heritage

  4. Overview SPF_SYS_003 FIELDS Technology Development Plan has three test phases: • Basic material testing to determine the thermal and optical properties. • Outgassing • Optical properties • Thermal conductivity of metals and insulators • Electrical resistance of insulators • Thermal distortion testing, to determine whether residual stresses in the material will cause the whips to distort after being subjected to high temperatures. • 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.

  5. Phase 1 Materials Test Matrix RT = Room Temperatures HT = Hot Expected Temperatures SRI = Southern Research Institute VPE = Vacuum Process Engineering PROMES= PROcess Materials and Solar Energy

  6. 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

  7. Phase 2: Whip Thermal Distortion Test performed two ways • 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 • VPE: 4 x 96” (2.4m) samples • heated in vacuum furnace to 1000°C • Results: distortion = 0.3° < 0.8° allocated in alignment budget

  8. 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: • Whip and its thermal/electrical isolator • Maximum temperature deviation from model 13°C (1%) • 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.

  9. 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)

  10. 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

  11. BACKUP SLIDES

  12. OutgassingTest 1403°C Red is temperature Blue is mass change • 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

  13. 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.

  14. 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)

  15. Optical Properties: Surface Finish Effects Niobium C103 • Untreated surface • Emissivity changed depending on the sample orientation (vertical vs. horizontal) • Roughened surface • Emissivity constant at all orientations Roughened Niobium C103 BRDF Room Temperature Measurements (APL)

  16. 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)

  17. 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

  18. Insulator Thermal Conductivity at High Temps • We are using data from Harvard SAO (SRI)

  19. Metals Thermal Conductivity at High Temps • We are using data from metal suppliers

  20. 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

  21. Whip Thermal Distortion • 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 3 meter T-VAC

  22. Odeillo Facilities Sun Heliostats Heat Flux controlled by opening doors Parabola Tower – Focal Point PROMES solar test facility can produce SSP flux levels, but with +-80° beam

  23. Odeillo Facilities- PROMES Chamber Water Cooled Air Cooled Heat Flux controlled by opening doors

  24. Thermal Choke TTM Whip Disk Whip Choke Choke Water Cooling

  25. Thermal Shield TTM Shield Clamp Bracket Water Cooled Stub

  26. 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

  27. TTM-1 Choke Thermal Balance • 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 B.C.

  28. TTM-2a - Shield Thermal Balance • 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 B.C. B.C. Found silver plated screws melted at higher shield temperature (1400°C)

  29. 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.

  30. Material Compatibility Test II • 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

  31. 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 NbC-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

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