FEP Material Inventory

• Solar Array I Drive Arm Multi Layer Insulation (SA-I MLI)
  • 1 Sample
• Magnetic Sensing System Electronic Box Multi Layer Insulation (MSS MLI)
  • 2 Samples

• 3.6 years in orbit.
• Atomic Oxygen (AO) fluence in the ram direction estimated to be 7.59 x 10^20 atoms per centimeter squared.
• Solar Fluence
  • SA-I drive arm material not yet calculated but thought to be similar to the MSS calculated values.
  • MSS MLI solar fluence values calculated for the MSS MLI sample range from 0.51 to 1.90 sun years.

• Contamination
• Micrometeoroid or Debris
• Thickness
• Other Space Effects

• Contamination Aspects
  • Areas of yellow to brownish residue.
  • Water spots.
• X-ray Photoelectron Spectroscopy is to be performed on selected samples removed from this specimen.

SA-I Drive Arm MLI: Micrometeoroid or Debris

• 6 impact sites identified.
• Residue not yet identified as being man-made or naturally occurring.
• Shock ring size varies with regard to penetration hole size.

• Milky colored haziness.
• Predominant on the solar facing surfaces.
  • Darkening of the stitching materials.
  • Cracking of the FEP material.

• Contamination
• Micrometeoroid or Debris
• Thickness
• Tensile and Elongation
• Other Space Effects

MSS MLI Surface: Contamination

• Very brown areas.
  • Around cable holes.
  • Along edges of Velcro.
• Darkening seems only to occur in proximity to underlying acrylic adhesive layer.

• 3 impact sites identified
• Micro-photographs of these sites are still pending.
  • Site 1: 6 layers penetrated
  • Site 2: 4 layers penetrated
  • Site 3: 8 layers penetrated
• Residue to be identified as man-made or naturally-occurring.

• Milky colored haziness.
• Cracking is evident on the material with high solar fluence.
• Adhesive failure is noted for the FEP/Acrylic interface.
• Increase of surface hardness.

Conclusions

• FEP MLI shows damage from space environmental exposure.
  • Cracking occurrences increase with increased solar exposures.
  • Increased hardness and reduced elongation was observed in areas of high solar fluence.
  • Erosion yield appears to be greater for higher solar fluence surfaces and is an order of magnitude greater than LDEF values.
• FEP is still acceptable as a thermal blanket material provided:
  • No insitu deformation occurs.
  • A suitable backing is adhesively applied to the FEP layer to maintain structural integrity.

• Determine accurate AO fluences for erosion yield calculations.
• Contamination evaluation.
  • X-ray Photoelectron Spectroscopy.
  • Scanning electron microscopy with energy dispersive spectroscopy.
• Measure optical properties to determine changes in thermal control.
• Surface topography analysis with atomic force and scanning electron microscopy.
• Cross sectioned material analysis.
  • Crack depth measurement
  • Atomic force microscopy hardness as a function of distance from surface.
• Comparison of HST samples with both LDEF and ground-based samples.

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