During the Hubble Space Telescope (HST) second servicing mission (SM2), degradation of unsupported Teflon ® FEP (fluorinated ethylene propylene), used as the outer layer of the multilayer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon ® FEP sample evaluation and additional testing of pristine Teflon ® FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations, and that the damage increased with the combined total dose of electrons, protons, ultraviolet and x-ray radiation along with thermal cycling. This paper discusses the testing and evaluation of the retrieved Teflon ® FEP.

Metallized Teflon ® fluorinated ethylene propylene (FEP) thermal control material on the Hubble Space Telescope (HST) is degrading in the space environment. Teflon ® FEP insulation was retrieved during servicing missions, which occurred in 1993, 1997 and 1999. During the second servicing mission (SM2), the 5 mil aluminized-FEP (Al-FEP) outer layer of multilayer insulation (MLI) covering the telescope was found to be cracked in many locations around the telescope. Teflon ® FEP retrieved during SM2 was more embrittled than the FEP retrieved 2.8 years later from a different location, during the third servicing mission (SM3A). Studies have been conducted to understand the degradation of FEP on HST, and the difference in the degree of degradation of FEP from each of the servicing missions. The retrieved SM2 material experienced a higher temperature extreme during thermal cycling (200 • C) than the first servicing mission (SM1) and SM3A materials (upper temperature of 50 • C), therefore an investigation on the effects of heating FEP was also conducted. Samples of pristine FEP and SM1, SM2 and SM3A retrieved FEP were heated to 200 • C and evaluated for changes in properties. Heating at 130 • C was also investigated because FEP bi-stem thermal shields are expected to cycle to a maximum temperature of 130 • C on-orbit. Tensile, density, x-ray diffraction crystallinity and differential scanning calorimetry data were evaluated. It was found that heating pristine FEP caused an increase in the density and practically no change in tensile properties. However, when as-retrieved space samples were heated, the density increased and the tensile properties decreased. Upon heating, all samples experienced an increase in crystallinity, with larger increases in the space-exposed FEP. These results indicate that irradiation of FEP in space causes chain scission, resulting in embrittlement, and that excessive heating allows increased mobility of space-environment-induced scissioned chains. Thermal exposure was therefore found to have a major impact on the extent of embrittlement of FEP on HST.

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This paper presents the results of the hypervelocity projectile bombardment of a gold-coated beryllium substrate telescope mirror. Individual latex (ρ = 1.1 g/cm 3 ) and iron ( 7.9 g/cm 3 ) projectiles , in the size range 0.70 to 1.44µm (avg. mass = 0.24 -7.1 x 10 -15 kg), representative of interplanetary dust, with velocities from 2 -20 km/s, created impact craters in the composite mirror structure that were approximate hemispheres. The ratio of impact damage diameter to projectile energy was found experimentally to be close to 0.1µm/nJ for both latex and iron projectiles. These dimension data, combined with recent measurements of interplanetary and interstellar dust fluxes, can be used to estimate expected space telescope mirror surface damage and scattering increase due to hypervelocity dust impacts.

The new generation of offshore support vessels (OSVs) has become increasingly sophisticated and technically advanced in response to demands from deepwater drilling and production operations. This paper reviews design issues and trends for the development of the next generation of OSVs, highlighting recently enhanced classification technical requirements. The new requirements address safety criteria and environmental protection for the design, construction and operation of OSVs.The paper also includes applicable criteria and new notations for each specialized service of the OSV including transportation of supplies and equipment, towing and anchoring of offshore structures, well stimulation and testing, fire fighting, heavy lift, oil spill containment, pipeline installation, diving activities and safety stand-by as well as provisions for the integration of multifunctional services.Additionally, the paper addresses the use of LNG as a fuel for propulsion primarily to reduce emissions.