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BalloonWinds Cracks Under Pressure

BalloonWinds Cracks Under Pressure. Jim Ryan University of New Hampshire. BalloonWinds Instrument Overview. Size : 8   8   12’ Gondola Mass : 5500 lbs Power Requirements : 1300 W Power System : 26 Lithium-Ion Batteries Thermal Management : Ice and Electric Heaters

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BalloonWinds Cracks Under Pressure

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  1. BalloonWinds Cracks Under Pressure Jim Ryan University of New Hampshire

  2. BalloonWindsInstrument Overview • Size: 8  8   12’ • Gondola Mass: 5500 lbs • Power Requirements: 1300 W • Power System: • 26 Lithium-Ion Batteries • Thermal Management: • Ice and Electric Heaters • Optical Systems: • Diode-Pumped Nd:YAG • ½-meter Telescope • Direct-Detection Receivers (2)

  3. BalloonWindsIntegrated Instrument

  4. Flight Timeline 5 4 • Liftoff - System Startup • Emit Laser and Signal Fiber Alignment • Flight Altitude Checkout • Eight-Hour Data Collection • Extended Data Collection (resources/weather) • Descent 6 1 2 3

  5. Mission Objectives • Measure wind velocity profiles with accuracy limited by photometric return and instrument technology. • Confirm instrument/atmosphere model for a space-like instrument. • Assess subsystem scalability for space. • Adapt model to a space-borne instrument and compare to data requirements.

  6. Previous BalloonWinds Schedule

  7. Thermal-Vacuum Test • 5 April 2007 at Kirtland AFB Phillips Lab • Catastrophic failure occurred during initial backfill • Damage assessment, failure analysis, redesign, and chamber reviews initiated

  8. External Pressure • Vacuum at 3:30 • Target P at 3:51 • Backfill at 3:55 • Internal Pressure • Pressurized at 2:05 • Failure at 3:50 • Tracks External P

  9. External Pressure • Linear decrease from pumping • Pressure wave from explosion measured at 3:50:22 • Internal Pressure • 1.21 bar initial • Rupture at 3:50:20 • 0.13 bar final • 1.07 bar differential

  10. Laser ChamberPre-Failure Cross-supports 29  47  ½-inch lid (0.35-inch eff. thickness)

  11. Laser ChamberPost-Failure I Cross-supports Secondary fractures from gondola impact Lid bottom Thermal insulation (yellow)

  12. Laser ChamberPost-Failure II Cross-support Secondary fractures from pipe interference Lid bottom Fibertek Laser

  13. Laser ChamberPost-Failure III Reverse angle showing the disorder

  14. Laser ChamberPost-Failure IV Fragments at the bottom of the thermal-vacuum chamber

  15. Damage Assessment • Laser chamber: Lid and walls • GPS, attitude sensors and heaters mounted on lid were damaged • External cooling lines were stressed • Internal damage was minimal • FiberTek laser and other key elements passed diagnostic testing 11 July 2007

  16. Failure Analysis Lid Support Structures • Lid required additional supports to counter pressure load (19,000 lbs) • Each cross-support was fastened to lid using 7 bolts • Middle beam took 20-39% of total load, depending on load/lid deformation

  17. Failure Analysis Lid Deformation & Reaction • Support beams much stiffer than lid • Lid pushed against middle beam in range of 3800-7400 lbs (calc.) • Only the two end bolts were under tension countering this load: 1800-3700 lbs each. Lid displacement contour acting against support beams

  18. Change of Lid Bolts • Small gauge bolt with insert to thread into Al. • New through-bolt fixation.

  19. Failure AnalysisPull-Out Strengths • Pull-out force for ¼-28 bolt in MIC-6 calculated to be 2100 lbs • Measurements on two samples reported 2100 & 2700 lbs • These values are at the lower-end of the expected 1800-3700 lbs load range Pull-Out Strength Measurements

  20. Pull Test Samples • Threads did not hold. • Too short • Too small diameter.

  21. Failure AnalysisFailure Sequence I • Pull-out occurred at an end of the middle support beam • Same-side bolts on neighboring beams let go • Unsupported lid then fractured • 4 end-bolts recovered with evidence of pull-out • 5th end bolt was released by a crack

  22. Failure AnalysisReconstructed Lid Fragments GPS & Attitude plate (damaged) Primary fracture line Secondary fractures Pull-out locations

  23. Failure AnalysisConclusions • Material selection (cast aluminum) was the primary cause of the failure • Poor strength required additional support • 3% elongation caused brittle fractures • Inaccuracies in the stress analysis • Failed to predict inadequate lid strength, which lead to the addition of cross-supports • Failed to predict pull-out of the cross-support bolts

  24. Laser Chamber RedesignThinking outside the box… RectangularCylindrical Feasible Feasible Aluminum Steel Lighter Stronger Reuse mounting scheme Gondola interference Simpler implementation Easier access Engineering costs Schedule

  25. Laser Chamber RedesignDesign Comparison I

  26. Laser Chamber RedesignDesign Comparison II Material: Cast Aluminum MIC6 Wrought Aluminum 6061-T6 Ultimate Strength: 166 MPa 310 MPa Yield Strength: 105 MPa 275 MPa Elongation at Break: 3% 12% Lid thickness (M/R) 0.5 (0.065) 2.25 (0.25) Lid/base attachment Inserted threads Through bolts Weight ~200 lbs ~400 lbs

  27. Chamber Reviews Coolant Tank Material 304L Stainless Steel Volume (empty) 18 cubic feet Design Pressure 18.75 psig Test Pressure (Hydrostatic) 28 psig Assembly Test Pressure (Pneumatic) 22.5 psig (1.5 MEOP) Electronics Chamber Material 304L Stainless Steel Volume (empty) 30 cubic feet Design Pressure 18.75 psig Test Pressure (Hydrostatic) 28 psig Assembly Test Pressure (Pneumatic) 22.5 psig (1.5 MEOP) Interferometer Chamber Material 304L Stainless Steel Volume 14 cubic feet Design Pressure 16.5 psig Assembly Test Pressure (Pneumatic) 22.5 psig (1.5 MEOP)

  28. Revised BalloonWinds Schedule

  29. Thermal Chamber Design ASME Pressure Vessel Code used Design validated using COMPress Software Material 304L Stainless Steel 24” Diameter 10 GA shell (.1345”) ASME Flanged and Dished heads Volume (empty) 18 cubic feet Design Pressure 18.75 psig Maximum Expected Operating Pressure (MEOP) ~15psig Fabrication Welded cylinder, Flanges and Heads Festival City Fabricators, Stratford ONT, CA Code approved pressure vessel manufacturer

  30. Thermal Chamber Testing Proof/Leak Test (Hydrostatic) 28 psig Functional/Leak testing UNH (Pneumatic) 16.5 psig (1.1 MEOP) 3 Complete pressure cycles to date.

  31. Electronics Chamber Design ASME Pressure Vessel Code used Design validated using COMPress Software Material 304L Stainless Steel 36 Diameter 10 GA shell (.1345”) ASME Flanged and Dished heads Volume (empty) 30 cubic feet Design Pressure 18.75 psig Maximum Expected Operating Pressure (MEOP) ~15psig Fabrication Welded cylinder, Flanges and Heads Festival City Fabricators, Stratford ONT, CA Code approved pressure vessel manufacturer

  32. Electronics Chamber Testing Proof/Leak Test (Hydrostatic) 28 psig Functional/Leak testing UNH (Pneumatic) 16.50 psig (1.1 MEOP) 3 Complete pressure cycles to date.

  33. Interferometer Chamber Design Material 304L Stainless Steel 20 Diameter 12 GA shell (.105”) Flat Heads with weight relief .625 thick Volume (empty) 18 cubic feet Design Pressure 16.5 psig ** Maximum Expected Operating Pressure (MEOP) ~15psig Fabrication Welded cylinder and flanges Shell made by Hollis Line Machining Hollis NH Code approved pressure vessel manufacturer Heads made by Advance Group Ann Arbor MI Testing Leak Test (Helium and Nitrogen) 16.3 psig Functional/Leak testing UNH (Pneumatic) 16.5 psig (1.1 MEOP) **Verified by mathematical analysis and OptiVessel Code

  34. Anyone want to golf on Thursday? • See this space for details.

  35. Laser Chamber Design Material MIC 6 Aluminum (Cast) Beams (added after initial lid deformation) 6061T6 Rectangular 29 x 45 x 13 Volume (empty) 9.5 cubic feet Design Pressure ? Maximum Expected Operating Pressure (MEOP) ~15psig Fabrication Welded side walls and O-ring seal top and bottom Advance Group Ann Arbor MI Testing Leak Test (Helium and Nitrogen) 16.32 psig Functional/Leak testing UNH (Pneumatic) 16.2 psig Failure Lid failed in TVAC at a differential pressure of 16.5 psig

  36. Laser ChamberFailure Analysis

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