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NASA NTRS1993

Space Station WP-2 application of LDEF MLI results

The Cascaded Variable Conductance Heat Pipe Experiment, which was developed by Michael Grote of McDonnell Douglas Electronic Systems Company, was located in Tray F-9 of the Long Duration Exposure Facility (LDEF), where it received atomic oxygen almost normal to its surface. The majority of the tray was covered by aluminized Kapton polyimide multilayer insulation (MLI), which showed substantial changes from atomic oxygen erosion. Most of the outermost Kapton layer of the MLI and the polyester scrim cloth under it were lost, and there was evidence of contaminant deposition which discolored the edges of the MLI blanket. Micrometeoroid and orbital debris (MM/OD) hits caused small rips in the MLI layers, and in some cases left cloudy areas where the vapor plume caused by a hit condensed on the next layer. The MLI was bent gradually through 90 deg at the edges to enclose the experiment, and the Kapton that survived along the curved portion showed the effects of atomic oxygen erosion at oblique angles. In spite of space environment effects over the period of the LDEF mission, the MLI blanket remained functional. The results of the analysis of LDEF MLI were used in developing the standard MLI blanket for Space Station Work Package-2 (WP-2). This blanket is expected to last 30 years when exposed to the low Earth orbit (LEO) environment constituents of atomic oxygen and MM/OD, which are the most damaging to MLI materials. The WP-2 standard blanket consists of an outer cover made from Beta-cloth glass fiber fabric which is aluminized on the interior surface, and an inner cover of 0.076-mm (0.003-in) double-side-aluminized perforated Kapton. The inner reflector layers are 0.0076-mm (0.0003-in) double-side aluminized, perforated Kapton separated by layers of Dacron polyester fabric. The outer cover was selected to be resistant to the LEO environment and durable enough to survive in orbit for 30 years. This paper describes the analyses of the LDEF MLI results, and how these results contributed to the selection of the WP-2 MLI blanket materials and configuration.

Smith, Charles A.↗

NASA NTRS1994

Reflective Packaging

The aluminized polymer film used in spacecraft as a radiation barrier to protect both astronauts and delicate instruments has led to a number of spinoff applications. Among them are aluminized shipping bags, food cart covers and medical bags. Radiant Technologies purchases component materials and assembles a barrier made of layers of aluminized foil. The packaging reflects outside heat away from the product inside the container. The company is developing new aluminized lines, express mailers, large shipping bags, gel packs and insulated panels for the building industry.

Source record↗

NASA NTRS1982

Effect of aluminum substitution on the reflectance spectra of hematite

Hematite and aluminous hematite were synthesized and the diffuse reflectance spectra were recorded for the region between 0.35 and 1.20 microns. Results show that the near-IR based minimum for the aluminous hematite is shifted longward by about 0.02 microns and is much more shallow. Also, the aluminous specimen is considerably more reflective shortward of approximately 0.55 microns where the ferritic specimen is strongly absorbing. This is noteworthy since the visible slope and the red shoulder are often used in the construction of false color and band ratio images.

Morris, R. V.↗

NASA NTRS1989

A slow positron beam generator for lifetime studies

A slow positron beam generator using well-annealed polycrystalline tungsten moderators and a Na-22 positron source was developed. A 250 micro c source, deposited on a 2.54 micron thick aluminized mylar, is sandwiched between two (2.54 cm x 2.54 cm x 0.0127 cm) tungsten pieces. Two (2.54 cm x 2.54 cm x t cm) test polymer films insulate the two tungsten moderator pieces from the aluminized mylar source holder (t=0.00127 to 0.0127). A potential difference of 10 to 100 volts--depending on the test polymer film thickness (t)--is applied between the tungsten pieces and the source foil. Thermalized positrons diffusing out of the moderator pieces are attracted to the source foil held at an appropriate potential below the moderator pieces. These positrons have to pass through the test polymer films before they can reach the source foil. The potential difference between the moderator pieces and the aluminized mylar is so adjusted as to force the positrons to stop in the test polymer films. Thus the new generator becomes an effective source of positrons for assaying thin polymer films for their molecular morphology.

Singh, Jag J.↗

NASA NTRS2002

Vacuum Ultraviolet Radiation and Atomic Oxygen Durability Evaluation of HST Bi-Stem Thermal Shield Materials

Bellows-type thermal shields were used on the bi-stems of replacement solar arrays installed on the Hubble Space Telescope (HST) during the first HST servicing mission (SMI) in December 1993. These thermal shields helped reduce the problem of thermal gradient- induced jitter observed with the original HST solar arrays during orbital thermal cycling and have been in use on HST for eight years. This paper describes ground testing of the candidate solar array bi-stem thermal shield materials including backside aluminized Teflon(R)FEP (fluorinated ethylene propylene) with and without atomic oxygen (AO) and ultraviolet radiation protective surface coatings for durability to AO and combined AO and vacuum ultraviolet (VOV) radiation. NASA Glenn Research Center (GRC) conducted VUV and AO exposures of samples of candidate thermal shield materials at HST operational temperatures and pre- and post-exposure analyses as part of an overall program coordinated by NASA Goddard Space Flight Center (GSFC) to determine the on-orbit durability of these materials. Coating adhesion problems were observed for samples having the AO- and combined AO/UV-protective coatings. Coating lamination occurred with rapid thermal cycling testing which simulated orbital thermal cycling. This lack of adhesion caused production of coating flakes from the material that would have posed a serious risk to HST optics if the coated materials were used for the bi-stem thermal shields. No serious degradation was observed for the uncoated aluminized Teflon(R) as evaluated by optical microscopy, although atomic force microscopy (AFM) microhardness testing revealed that an embrittled surface layer formed on the uncoated Teflon(R) surface due to vacuum ultraviolet radiation exposure. This embrittled layer was not completely removed by AO erosion, No cracks or particle flakes were produced for the embrittled uncoated material upon exposure to VUV and AO at operational temperatures to an equivalent exposure of approximately five years in the HST environment. Uncoated aluminized FEP Teflon(R) was determined to be the most appropriate thermal shield material and was used on the bi-stems of replacement solar arrays installed on HST during SMI in December 1993. The SMI -installed solar arrays air scheduled to be replaced during MST's fourth servicing mission (SM3B) in early 2002.

Dever, Joyce↗

NASA NTRS1978

Wall Covering

The attractive wall covering shown below is one of 132 styles in the Mirror Magic II line offered by The General Tire & Rubber Company, Akron, Ohio. The material is metallized plastic fabric, a spinoff from space programs. Wall coverings are one of many consumer applications of aluminized plastic film technology developed for NASA by a firm later bought by King-Seeley Thermos Company, Winchester, Massachusetts, which now produces the material. The original NASA use was in the Echo 1 passive communications satellite, a "space baloon" made of aluminized mylar; the high reflectivity of the metallized coating enabled relay of communications signals from one Earth station to another by "bouncing" them off the satellite. The reflectivity feature also made the material an extremely efficient insulator and it was subsequently widely used in the Apollo program for such purposes as temperature control of spacecraft components and insulation of tanks for fuels that must be maintained at very low temperatures. I Used as a wall covering, the aluminized material offers extra insulation, reflects light and I resists cracking. In addition to General Tire, King-Seeley also supplies wall covering material to Columbus Coated Fabrics Division of Borden, Incorporated, Columbus, Ohio, among others.

Source record↗

NASA NTRS2003

High-Energy-Density Capacitors

Capacitors capable of storing energy at high densities are being developed for use in pulse-power circuits in such diverse systems as defibrillators, particle- beam accelerators, microwave sources, and weapons. Like typical previously developed energy-storage capacitors, these capacitors are made from pairs of metal/solid-dielectric laminated sheets that are wound and pressed into compact shapes to fit into cans, which are then filled with dielectric fluids. Indeed, these capacitors can be fabricated largely by conventional fabrication techniques. The main features that distinguish these capacitors from previously developed ones are improvements in (1) the selection of laminate materials, (2) the fabrication of the laminated sheets from these materials, and (3) the selection of dielectric fluids. In simplest terms, a high-performance laminated sheet of the type used in these capacitors is made by casting a dielectric polymer onto a sheet of aluminized kraft paper. The dielectric polymer is a siloxane polymer that has been modified with polar pendant groups to increase its permittivity and dielectric strength. Potentially, this polymer is capable of withstanding an energy density of 7.5 J/cm3, which is four times that of the previous state-of-the-art-capacitor dielectric film material. However, the full potential of this polymer cannot be realized at present because (1) at thicknesses needed for optimum performance (.8.0 m), the mechanical strength of a film of this polymer is insufficient for incorporation into a wound capacitor and (2) at greater thickness, the achievable energy density decreases because of a logarithmic decrease in dielectric strength with increasing thickness. The aluminized kraft paper provides the mechanical strength needed for processing of the laminate and fabrication of the capacitor, and the aluminum film serves as an electrode layer. Because part of the thickness of the dielectric is not occupied by the modified siloxane polymer, the achievable energy density must be somewhat less than the maximum value. The laminate is produced by a continuous film-casting process, using the machinery depicted schematically in the figure. The designs of the process and machinery are dictated partly by the fact that during the processing step prior to casting the polymer, the aluminized kraft paper becomes wet with water. Because the polymer resin to be cast is hydrophobic, the paper must be dried to make it possible to coat the paper uniformly, leaving no pinholes. Accordingly, an infrared heater is placed next to the paper feed roll to dry the paper prior to casting.

Slenes, Kirk↗

NASA NTRS1972

Diffusion of chromium and aluminum in Ni-20Cr and TDNiCr /Ni-20Cr-2ThO2/.

Diffusion coefficients have been measured for Cr51 in fine- and coarse-grained TDNiCr (Ni-20Cr-2ThO2) and in fine-grained Ni-20Cr in the temperature range from 1038 to 1200 C. Selective diffusivities have also been determined for specimens of these alloys which were aluminized to give an initial surface concentration of 5.8 wt % Al. Finally, diffusion coefficients for interdiffusion of aluminum in TDNiCr and Ni-20Cr have been obtained from electron probe microanalysis of the aluminized specimens. For a given grain size and temperature there is no difference in diffusivities for chromium diffusion in TDNiCr or Ni-20Cr. Diffusion coefficients increase with decreasing grain size for both alloys. Comparison of aluminum diffusion data obtained from electron microprobe profiles with radiotracer chromium diffusivities suggests that aluminum diffuses approximately three times faster than chromium in TDNiCr and Ni-20Cr.

Seltzer, M. S.↗

NASA NTRS1975

Development of fracture mechanics data for two hydrazine APU turbine wheel materials

The effects of high temperature, high pressure ammonia were measured on the fracture mechanics and fatigue properties of Astroloy and Rene' 41 turbine wheel materials. Also, the influence of protective coatings on these properties was investigated. Specimens of forged bar stock were subjected to LCF and HCF tests at 950 K (1250 F) and 3.4 MN/sq m (500 psig) pressure, in ammonia containing about 1.5 percent H2O. Aluminized samples (Chromizing Company's Al-870) and gold plated test bars were compared with uncoated specimens. Comparison tests were also run in air at 950 K (1250 F), but at ambient pressures. K sub IE and K sub TH were determined on surface flawed specimens in both the air and ammonia in both uncoated and gold plated conditions. Gold plated specimens exhibited better properties than uncoated samples, and aluminized test bars generally had lower properties. The fatigue properties of specimens tested in ammonia were higher than those tested in air, yet the K sub TH values of ammonia tested samples were lower than those tested in air. However, insufficient specimens were tested to develop significant design data.

Curbishley, G.↗

NASA NTRS1975

Hot corrosion evaluation of aluminide coated superalloys in support of an ASTM Round Robin program

Commercial aluminized coatings on substrates were hot corroded at 900 C in a 0.3 Mach burner rig with 5 ppm synthetic sea salt and at two cycling frequencies. Extensive post-exposure examinations were conducted on the corroded specimens such as metallography, X-ray diffraction, scanning electron microscopy, microprobe raster scans, and spectrographic analyses. Thermodynamic calculations were made of the equilibrium burner flame composition and the calculations were compared to the experimental findings. It was found that localized spalling of the coatings preceded coating failure. It is suggested that the spalling of the coatings is due to the formation of localized stresses caused by the depletion of chromium and aluminum in the coating or the enrichment of the coating with sulfur. For the materials and test conditions investigated, it was found that coating life is dependent only upon the initial coating thickness and not on the type of aluminized coating, the substrate, or the cycle frequency.

Santoro, G.↗

NASA NTRS1975

Thermodynamics and kinetics of reactions in protective coating systems

A study of the aluminization of Ni from packs containing various percentages of unalloyed Al confirmed that the surface aluminum content of specimens aluminized tends to decrease with time and consequently a simple parabolic law for the weight-gain vs. time relationship is not obeyed. The diffusivity-composition relationship in NiAl was examined, and a set of curves is presented. A numerical method for the calculation of coating dissolution rates was developed and applied to NiAl-Ni3Al type of coatings.

Gupta, B.↗

NASA NTRS1976

Coatings for directional eutectics

Significant advances have been made in the development of an environmentally stable coating for a very high strength, directionally solidified eutectic alloy designated NiTaC-13. Three duplex (two-layer) coatings survived 3,000 hours on a cyclic oxidation test (1,100 C to 90 C). These coatings were fabricated by first depositing a layer of NiCrAl(Y) by vacuum evaporation from an electron beam heated source, followed by depositing an aluminizing overlayer. The alloy after exposure with these coatings was denuded of carbide fibers at the substrate/coating interface. It was demonstrated that TaC fiber denudation can be greatly retarded by applying a carbon-bearing coating. The coating was applied by thermal spraying followed by aluminization. Specimens coated with NiCrAlCY+Al survived over 2,000 hours in the cyclic oxidation test with essentially no TaC denudation. Coating ductility was studied for coated and heat-treated bars, and stress rupture life at 871 C and 1,100 C was determined for coated and cycled bars.

Rairden, J. R.↗

NASA NTRS1976

Cryogenic Hydrogen/helium Storage and Supply System, Phase 1

An existing cryogenic tank was refurbished, microspheres were installed in the tank annulus, and the thermal performance of the unit was tested. The performance data was compared with NRC-2 multilayer insulation and low emittance aluminized surfaces installed in tanks of the same basic design. The cryogenic tank modified during the program was originally designed for the Manned Orbiting Laboratory (MOL) Program, and subsequently modified by vacuum-depositing aluminum on all annulus surfaces and leaving out the NRC-2 multilayer insulation. It is concluded that the application of aluminized-microsphere insulation is not yet very predictable for tank design purposes, especially at LH2 temperature and in the presence of a vapor-cooled shield.

Norman, R. H.↗

NASA NTRS1978

Clast assemblages of possible deep-seated /77517/ and immiscible-melt /77538/ origins in Apollo 17 breccias

Breccia samples 77517 and 77538 are composed of abundant mineral and lithic clasts set in porous, poorly sintered matrices. Clast assemblages in the two rocks are of contrasting composition and origin. Breccia 77517 has Mg-rich olivine and pyroxene and calcic plagioclase clasts, indicating limited, almost exclusively ANT-suite parentage. A significant feature is the presence of an assemblage (aluminous enstatite, forsterite, anorthite, aluminous spinel) corresponding to spinel cataclasite, a rock type of deep-seated (about 60 km) crustal origin. Breccia 77538 contains Fe-rich pyroxene and rather sodic plagioclase clasts, indicative of predominantly KREEP and/or mare derivation. An important feature is the occurrence of high-K and high-Fe lithic clasts whose compositions resemble those of immiscible-melts produced during late-stage magmatic crystallization, and which probably originated via silicate liquid immiscibility in a KREEP or mare basalt magma. Both rocks contain numerous fine-grained breccia clasts which represent material that has been modified by impact processes at or very near the moon's surface.

Warner, R. D.↗

NASA NTRS1981

Evacuation-induced pressure differentials in multilayer insulation systems

The pressure differentials induced across three types of multilayer insulation systems during evacuation have been measured and compared with values predicted using an idealized parallel plate geometric model. The systems tested were double-aluminized Mylar with a Tissuglas or silk net spacer and crinkled single-aluminized Mylar. Test samples were circular. The influence of purge gas type, layer density, sample diameter, and temperature was systematically investigated. The experimental approach was to measure the absolute pressure history and corresponding pressure differential induced across the insulation during evacuation. The measured pressure differentials were nondimensionalized and compared with those predicted by the parallel plate model as a function of Knudsen number. It was concluded that the parallel plate model is adequate for making engineering analyses. The influence of all parameters, except layer density, is well represented by the model. Representation of the influence of layer density is less satisfactory, but can be improved by modification of the flat plate model to allow for the more obvious practical nonidealities, such as crinkling, or the presence of a net spacer.

Glassford, A. P. M.↗

NASA NTRS1982

Further efforts to limit lunar internal temperatures from electrical conductivity determinations

A representative set of 18 electrical conductivity profiles consistent with lunar transfer function data in the 0.00001 to 0.001 Hz range is generated by means of a Monte Carlo procedure. Laboratory electrical conductivity vs temperature data extrapolated to lower and higher temperatures are used to convert the 18 profiles into temperature profiles for a series of radially homogeneous olivine-pyroxene mixtures ranging from 100% olivine to 100% aluminous orthopyroxene. The former yields selenotherms approaching the Ringwood-Essene solidus at depths near 500 km, while additions of the latter in concentrations greater than 15-30 vol% leads to cooler selenotherms which approach the solidus only at depths greater than about 1000 km. On the basis of independent geophysical constraints, the profile envelopes for compositions containing more than 15-30 vol% aluminous orthopyroxene are considered to be the most probable.

Hood, L. L.↗

NASA NTRS1982

Thermal performance of aircraft polyurethane seat cushions

Measurements were conducted on 7.6 x 7.6 cm samples of polyurethane seat cushion material in a modified National Bureau of Standards smoke density chamber to simulate real life conditions for an onboard aircraft fire or post-crash fire. In this study, a non-flaming heat radiation condition was simulated. Two aluminized polymeric fabrics (Norfab 11HT-26-A and Preox 1100-4) and one neoprene type material in two thicknesses (Vonar 2 and 3) were tested as heat blocking layers to protect the urethane foam from rapid heat degradation. Thermogravimetric analysis and differential scanning calorimetry were performed to characterize thermally the materials tested. It was found that Vonar 2 or 3 provided approximately equal thermal protection to F.R. urethane as the aluminized fabrics, but at a significant weight penalty. The efficiency of the foams to absorb heat per unit mass loss when protected with the heat blocking layer decreases in the heating range of 2.5-5.0 W/sq cm, but remains unchanged or slightly increases in the range of 5.0-7.5 W/sq cm. The results show that at all heat flux ranges tested the usage of a heat blocking layer in aircraft seats significantly improves their thermal performance.

Kourtides, D. A.↗

NASA NTRS1984

Apollo 16 site geology and impact melts - Implications for the geologic history of the lunar highlands

The geology of the Apollo 16 site is reconsidered on the basis of data from photogeology, geochemical remote sensing, and lunar samples. The site possesses an upper surface of anorthositic gabbro and related rocks. Mafic components were deposited as basin ejecta. The events involved in its geological evolution were the Nectaris impact and the Imbrium impact. The role of large, local craters in the history of the region was to serve as topographic depressions to accumulate basin ejecta. The most abundant melt composition at Apollo 16 is an aluminous variety of LKFM basalt supplied by the Nectaris impact as ejected basin impact melt. The mafic LKFM melt may have been supplied by the Imbrium impact. More aluminous melt groups are probably derived from local, small craters. The remainder of the deposits in the region are composed of anorthositic clastic debris derived from the Nectaris basin, the local crustal substrate, and Imbrium and other basins.

Spudis, P. D.↗