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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Radiation durability of polymeric matrix composites

The combined effects of thermal cycling and high-dose electron irradiation on the mechanical properties of laminated graphite/polymeric CFRPs are investigated experimentally. The test apparatus and procedures are briefly described, and the results are presented in extensive tables and graphs. It is found that electron radiation produces similar significant reductions in the glass transition temperatures of the neat resins and CFRPs. The radiation-induced degradation products tend to plasticize the matrix at high temperature but embrittle it at low temperature.

Tenney, Darrel R.↗
NASA NTRS1989

Performance and durability of HgI2 X-ray detectors for space missions

Considerable progress has been achieved recently in HgI2 detector fabrication technology and amplification electronics. An energy resolution of 198 eV (full width at half maximum) has been obtained for the Mn k-alpha line of 5.9 keV in a practical X-ray probe without the use of cryogenic cooling. Detectors prepared with Parylene-C encapsulation have demonstrated perfect reliability in two-year tests under high vacuum and temperature and bias cycling. Other HgI2 detectors have been used to demonstrate proton-radiation-damage resistance to levels of 10 to the 12 protons/sq cm at 10.7 MeV. It is concluded that HgI2 detectors are suitable for the ordinary requirements of energy dispersive detectors in X-ray spectroscopy systems.

Iwanczyk, J. S.↗
NASA NTRS1990

Durable Bipolar Plates For Lead/Acid Batteries

New structure for positive faces of bipolar plates increases longevity of lead/acid batteries. Divides positive-electrode layer into many isolated segments so defects cannot spread across layer. Surfaces treated before assembly to promote adhesion. Ridges on body divide possible electrode into isolated squares, each typically 1 in. on side. Materials supporting electrochemically active components lightweight and resistant to acid.

Clough, Thomas J.↗
NASA NTRS1990

Determination of the durability of the fiberoptics in rocket engine environments

The results of a testing program in which selected optical fibers were exposed to extreme environments representative of those experienced on rocket engines are discussed. Included in the experiment are cold-bend testing, a moisture embrittlement test, a thermal cycling test, temperature extremes testing, vibration testing, and shock testing. Two of the fibers selected, the titanium-carbide-coated and the aluminum-jacketed silica samples succeeded in passing all the tests without a failure.

Delcher, R.↗
NASA NTRS1990

A highly durable injector faceplate design concept for O2/H2 propellants

Two different O2/H2 injector faceplate designs were used in a test bed rocket engine at the NASA Lewis Research Center facility. This test bed was operated in a pulsing mode to evaluate thrust chamber wall materials and coatings. Degradation of the sintered mesh injector face plates resulted in the substitution of a photoetched diffusion-bonded platelet faceplate. This faceplate accumulated over 4200 thermal cycles without damage or degradation. Prior testing for a total of 17,446 cycles required 19 sintered mesh faceplates. This average of 918 cycles per unit showed the diffusion bonded faceplate to have a thermal cycle capability ranging from 150 to 500 percent of that of the sintered wire unit. The test data also showed that the diffusion-bonded faceplate provided a more uniform flow of gaseous H2 through its discrete and uniformly spaced propellant orifices resulting in enhanced face cooling (no local hot spots) and increased performance. The injector faceplate designs are described and the results of the injector comparison test data are presented.

Mueggenburg, H. H.↗
NASA NTRS1991

Durability evaluation of photovoltaic blanket materials exposed on LDEF tray S1003

Several candidate protective coatings on Kapton and uncoated Kapton were exposed to the LEO environment on the LDEF in order to determine whether the coatings could be used to protect polymeric substrates from degradation in the LEO environment. These materials are used for flexible solar array panels in which the polymer is the structural member that supports the solar cell and current carriers. Arrays such as these are used on the Hubble Space Telescope and will be used on Space Station Freedom. The results of the experiments are presented.

Rutledge, Sharon K.↗
NASA NTRS1989

The durability of graphite/epoxy laminate subjected to repeated low velocity impact

Low velocity impact has been considered as quasi-static loading, as the dynamic effects are decaying before the pressure reaches its maximum. However, when the impact energy is low enough as not to cause visible damage, the dynamic effect at the beginning of the impact may cause internal damage to the laminate. Laminates were loaded quasi-statically and by impact to the same bending strain and with the same indenter shape several times. The laminates that were subjected to the impact loading failed much more rapidly. Analysis of the problem shows that the stress waves created by the impact at the beginning of contact intensify the damage zone created by the preceding impact until the final failure occurs.

Rotem, A.↗
NASA NTRS1992

High-temperature durability considerations for HSCT combustor

The novel combustor designs for the High Speed Civil Transport will require high temperature materials with long term environmental stability. Higher liner temperatures than in conventional combustors and the need for reduced weight necessitates the use of advanced ceramic matrix composites. The combustor environment is defined at the current state of design, the major degradation routes are discussed for each candidate ceramic material, and where possible, the maximum use temperatures are defined for these candidate ceramics.

Jacobson, Nathan S.↗
NASA NTRS1990

Atomic oxygen durability of solar concentrator materials for Space Station Freedom

The findings are reviewed of atomic oxygen exposure testing of candidate solar concentrator materials containing SiO2 and Al2O3 protective coatings for use on Space Station Freedom solar dynamic power modules. Both continuous and iterative atomic oxygen exposure tests were conducted. Iterative air plasma ashing resulted in larger specular reflectance decreases and solar absorptance increases than continuous ashing to the same fluence, and appears to provide a more severe environment than the continuous atomic oxygen exposure that would occur in the low Earth orbit environment. First generation concentrator fabrication techniques produced surface defects including scratches, macroscopic bumps, dendritic regions, porosity, haziness, and pin hole defects. Several of these defects appear to be preferential sites for atomic oxygen attack leading to erosive undercutting. Extensive undercutting and flaking of reflective and protective coatings were found to be promoted through an undercutting tearing propagation process. Atomic oxygen erosion processes and effects on optical performance is presented.

Degroh, Kim K.↗
NASA NTRS1992

Sliding durability of two carbide-oxide candidate high temperature fiber seal materials in air to 900 C

A test program to determine the friction and wear properties of two complex carbide oxide ceramic fibers for high temperature sliding seal applications is described. The fibers are based on Si, C, O, and Ti or Si, C, N, and O ceramic systems. Pin on disk tests using ceramic fiber covered pins and Inconel 718 disks, were conducted in air from 25 to 900 C to evaluate potential seal materials. This testing procedure was used in a previous study of oxide ceramic fibers which were found to exhibit wear behavior based predominantly on their mechanical properties. Like the oxide fibers tested previously, these carbide oxide ceramic fibers, show an increase in friction and wear with increased test temperature. At room temperature, the wear behavior seems to be based upon mechanical properties, namely tensile strength. At 500 and especially 900 C, the fibers wear by both mechanical fracture and by oxidative type wear. Based upon post test microscopic and x ray analyses, interaction between the fiber constituents and elements transferred from the counterface, namely Ni and Cr, may have occurred enhancing the tribochemical wear process. These results are interpreted.

Dellacorte, Christopher↗
NASA NTRS1992

Low earth orbit durability evaluation of Haynes 188 solar receiver material

The effects of elevated-temperature vacuum and elevated-temperature atomic oxygen exposure on the mass, surface chemistry, surface morphology, and optical properties of Haynes 188, a possible heat receiver material for space-based solar dynamic power systems, have been studied. Pristine and surface modified Haynes 188 were exposed to vacuum less than or equal to 10 exp -6 torr at 820 C for 5215.5 h, and to atomic oxygen in an air plasma asher at 34 and 827 C for fluences up to 5.6 x 10 exp 21 atoms/sq cm. Results obtained indicate that vacuum heat treatment caused surface morphology and chemistry changes with corresponding optical property changes. Atomic oxygen exposure caused optical property changes which diminished with time. Mass changes are considered to be negligible for both exposures.

De Groh, Kim K.↗
NASA NTRS1992

Predicted and tested performance of durable TPS

The development of thermal protection systems (TPS) for aerospace vehicles involves combining material selection, concept design, and verification tests to evaluate the effectiveness of the system. The present paper reviews verification tests of two metallic and one carbon-carbon thermal protection system. The test conditions are, in general, representative of Space Shuttle design flight conditions which may be more or less severe than conditions required for future space transportation systems. The results of this study are intended to help establish a preliminary data base from which the designers of future entry vehicles can evaluate the applicability of future concepts to their vehicles.

Shideler, John L.↗
NASA NTRS1993

Characterization and durability testing of plasma-sprayed zirconia-yttria and hafnia-yttria thermal barrier coatings. Part 1: Effect of spray parameters on the performance of several lots of partially stabilized zirconia-yttria powder

Initial experiments conducted on thermal barrier coatings prepared in the newly upgraded research plasma spray facility and the burner rig test facilities are discussed. Part 1 discusses experiments which establish the spray parameters for three baseline zirconia-yttria coatings. The quality of five similar coating lots was judged primarily by their response to burner rig exposure supplemented by data from other sources such as specimen characterizations and thermal diffusivity measurements. After allowing for burner rig variability, although there appears to be an optimum density (i.e., optimum microstructure) for maximum burner rig life, the distribution tends to be rather broad about the maximum. In Part 2, new hafnia-yttria-based coatings were evaluated against both baseline and alternate zirconia-yttria coatings. The hafnia-yttria coatings and the zirconia-yttria coatings that were prepared by an alternate powder vendor were very sensitive to plasma spray parameters, in that high-quality coatings were only obtained when certain parameters were employed. The reasons for this important observation are not understood. Also not understood is that the first of two replicate specimens sprayed for Part 1 consistently performed better than the second specimen. Subsequent experiments did not display this spray order affect, possibly because a chiller was installed in the torch cooling water circuit. Also, large changes in coating density were observed after switching to a new lot of electrodes. Analyses of these findings were made possible, in part, because of the development of a sensitive density measurement technique described herein in detail. The measured thermal diffusivities did not display the expected strong relationship with porosity. This surprising result was believed to have been caused by increased microcracking of the denser coatings on the stainless steel substrates.

Miller, Robert A.↗
NASA NTRS1992

Structural durability of a composite pressure vessel

The effect of local ply fiber fracture on the load-carrying capability and structural behavior of a composite cylindrical shell under internal pressure is investigated, using the CODSTRAN computer code to simulate the composite structural degradation under loading. Results show that an initial outer-surface defect in the vessel begins to grow at a relatively low pressure but exhibits localized gradual damage growth prior to structural fracture and that an initial inner-surface defect shows an overall damage progression and fracture behavior closely similar to that of the outer surface defect. An initial defect located near the mid-thickness of the shell requires a higher pressure to cause damage initiation, but, once the damage initiation pressure is reached, a sudden structural fracture stage is entered by rapid damage propagation at a slightly higher pressure.

Minnetyan, Levon↗
NASA NTRS1993

A hot dynamic seal rig for measuring hypersonic engine seal durability and flow performance

A test fixture for measuring the dynamic performance of candidate high-temperature engine seal concepts has been installed at NASA Lewis Research Center. The test fixture has been designed to evaluate seal concepts under development for advanced hypersonic engines, such as those being considered for the National Aerospace Plane (NASP). The fixture can measure dynamic seal leakage performance from room temperature up to 840 C (1550 F) and air pressure differentials up to 690 kPa (100 psi). Performance of the seals can be measured while sealing against flat or distorted walls. In the fixture two seals are preloaded against the sides of a 30 cm (1 ft) long saber that slides transverse to the axis of the seals, simulating the scrubbing motion anticipated in these engines. This report covers the capabilities of this test fixture along with preliminary data showing the dependence of seal leakage performance on high temperature cycling.

Miller, Jeffrey H.↗