Design Analysis of A Scientific Balloon Instrument Support Structure ISS

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Design Analysis of A Scientific Balloon
Instrument Support Structure (ISS)

• Victor Eyo
• Mechanical Systems Branch (Code 548)
• Wallops Flight Facility
• Chip Frohlich
• Swales Aerospace

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Motivation

• Scientific Balloon ISS Analysis Design
• Simple structure
• Becoming complex
• Lightweight
• Longer flight duration
• Optimization maintain integrity of science
• Example using 04 CREAM campaign
• WFF Mechanical Systems Branch (Code 548)
• Broad support services in the areas of
• Structural analysis
• Mechanical design
• Thermal engineering
• Materials research and development
• Assembly, integration and testing
• Balloons Program Office (http//www.wff.nasa.gov/
  code820/)
• http//www.wff.nasa.gov/about/capabilities.php

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Scientific Balloons
459 ft.
396 ft.
Balloon vehicle
Parachute with UV- protective shroud
Flight train
300ft.
Ballooncraft
Cable ladder

• Volume 39.57mcf
• Weight 4,055lb
• Float Altitude 125Kft
• Payload 4,153lb
• Film 20.32mm (0.8mil)

Rotator
ISS
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The Instrument Support Structure

• ISS
• Assembled set of mechanical components that
  provide the primary load path to support the
  weight and inertial loads of the
• science payload
• ballooncraft support systems
• The National Scientific Balloon Facility (NSBF),
  Palestine, TX
• Specifies loading conditions
• Responsible for flight worthiness certification
  of the ballooncraft
• Responsible for flight operations

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CREAM ISS Initial Design

• Cosmic Ray Energetics And Mass Experiment
• December 2004 Flight - Long Duration Balloon
• Investigate ultra high energy cosmic rays (1012
  to gt 5 x 1014 eV)
• Collaboration
• Universities of Maryland, Chicago, Penn State
  University
• Universities and Organizations in Italy, Korea,
  France and Mexico
• Initial ISS design and analysis by Swales
  Aerospace
• MSC NASTRAN Model
• 42500 Elements, 44428 Nodes
• Total model weight 5,185 lb
• Plate, bar, solid, RBE3, and mass elements used
• All bolt interfaces represented
• Bolt bars modeled to be stiff compared to joint
  material
• All Panel doublers and closeouts represented with
  modified plate properties
• Fasteners CRES, Minimum 160Ksi Tensile Strength
• Material Al 7075-T7451, 7075-T7351

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CREAM ISS Initial Design
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CREAM ISS Initial Design

• Loading Condition
• Transient
• Applied analytically as a static load
• Imparted to structure at termination
• End of scientific experiments
• Ballooncraft flight train separate from balloon
  vehicle
• Balloon free-falls to earth
• Rest of ballooncraft free-falls also
• Shock load at parachute deployment

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ISS Loading Condition

• The ISS design is such that all load-carrying
  structural members are capable of withstanding
  the NSBF prescribed conditions without ultimate
  structural failure.

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Initial Design Loading Condition
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CREAM ISS Evolution

• Q3 2003
• ISS delivered to WFF
• FEA model delivered to WFF
• Q4 2003
• Completed load test on fabricated structure
• Updated FEA model
• 2004
• Lots of changes

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CREAM ISS Design Update
CDM Assembly
Solar Array Assembly
Legs Crush Pads and Heater Assembly
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CREAM ISS Design Update

• Problem 1 - Big
• Massive fastener failure

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CREAM ISS Design Update
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CREAM ISS Design Update

• Fasteners inaccessible for replacement

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CREAM ISS Design Update

• Solution
• Add shear pins

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CREAM ISS Design Update

• Problem 2 - Bigger
• Single point failure
• Flight tested
• Conflict Flight experience with part vs FEA data

• Bench Test Data Confirmed FEA Results
• Possibility of fastener yielding

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ISS Design Analysis Challenges

• What failure criteria to apply?
• Yield/ultimate
• Quick turn-around flight
• Re-flight ? aborted primary flight
• Re-flight ? opportunity
• Post yield post buckling analyses
• System Constraints
• ULDB vs LDB missions
• ISS boundary conditions
• Loading Condition
• Better definition of termination loads

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CREAM ISS - Images
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CREAM ISS - Images
Upper Tri-Plate Rotator
Lifting Exercises
Men _at_ Work
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CREAM ISS - Images
Balloon Inflation
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CREAM ISS - Images
Landing Recovery