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Tensile, peel, and shear testing was performed on combinations of primers, adhesives, tycements and rubber compounds cured at various times and temperatures. The materials used in the fabrication of the solid rocket motor flex bearing as well as in other systems were evaluated. A compatibility study between adhesives and tycements was initiated. The flex bearing mold design was reviewed by our tooling experts.
Improvement in the high-pressure turbopumps, both fuel and oxidizer, in the Space Shuttle main engine were considered. The operation of these pumps is limited by temperature restrictions of the metallic components used in these pumps. Ceramic materials that retain strength at high temperatures and appear to be promising candidates for use as turbine blades and impellers are discussed. These high strength materials are sensitive to many related processing parameters such as impurities, sintering aids, reaction aids, particle size, processing temperature, and post thermal treatment. The specific objectives of the study were to: (1) identify and define the processing parameters that affect the properties of Si3N4 ceramic materials, (2) design and assembly equipment required for processing high strength ceramics, (3) design and assemble test apparatus for evaluating the high temperature properties of Si3N4, and (4) conduct a research program of manufacturing and evaluating Si3N4 materials as applicable to rocket engine applications.
In order to support materials selection for the next-generation supersonic civilian-passenger transport aircraft, a study has been undertaken to evaluate the material stress/strain relationships needed to describe advanced polymer matrix composites under conditions of high load and elevated temperature. As part of this effort, this paper describes the materials testing which was performed to investigate the viscoplastic behavior of graphite/thermoplastic and graphite/bismaleimide composites. Test procedures, results and data-reduction schemes which were developed for generating material constants for tension and compression loading, over a range of useful temperatures, are explained.
We have produced a variety of superconducting transition edge sensor array designs for microcalorimetric detection of x-rays. Designs include kilopixel scale arrays of relatively small sensors (~75 micron pitch) atop a thick metal heatsinking layer as well as arrays of membrane-isolated devices on 250 micron pitch and smaller arrays of devices up to 600 micron pitch. We discuss the fabrication techniques used for each type of array focusing on unique aspects where processes vary to achieve the particular designs and required device parameters. For example, we evaluate various material combinations in the production of the thick metal heatsinking, including superconducting and normal metal adhesion layers. We also evaluate the impact of added heatsinking on the membrane isolated devices as it relates to basic device parameters. Arrays can be characterized with a time division SQUID multiplexer such that greater than 10 devices from an array can be measured in the same cooldown. Device parameters can be measured simultaneously so that environmental events such as thermal drifts or changes in magnetic fields can be controlled. For some designs, we will evaluate the uniformity of parameters impacting the intrinsic performance of the microcalorimeters under bias in these arrays and assess the level of thermal crosstalk.
In support of the CA250 project, this paper details the results of a test campaign that was conducted at the Ames Arcjet Facility, wherein several novel low density thermal protection (TPS) materials were evaluated in an entry like environment. The motivation for these tests was to investigate whether novel conformal ablative TPS materials can perform under high heat flux and shear environment as a viable alternative to rigid ablators like PICA or Avcoat for missions like MSL and beyond. A conformable TPS over a rigid aeroshell has the potential to solve a number of challenges faced by traditional rigid TPS materials (such as tiled Phenolic Impregnated Carbon Ablator (PICA) system on MSL, and honeycomb-based Avcoat on the Orion Multi Purpose Crew Vehicle (MPCV)). The compliant (high strain to failure) nature of the conformable ablative materials will allow better integration of the TPS with the underlying aeroshell structure and enable monolithic-like configuration and larger segments to be used in fabrication.A novel SPRITE1 architecture, developed by the researchers at NASA Ames was used for arcjet testing. This small probe like configuration with 450 spherecone, enabled us to test the materials in a combination of high heat flux, pressure and shear environment. The heat flux near the nose were in the range of 500-1000 W/sq cm whereas in the flank section of the test article the magnitudes were about 50 of the nose, 250-500W/sq cm range. There were two candidate conformable materials under consideration for this test series. Both test materials are low density (0.28 g/cu cm) similar to Phenolic Impregnated Carbon Ablator (PICA) or Silicone Impregnated Refractory Ceramic Ablator (SIRCA) and are comprised of: A flexible carbon substrate (Carbon felt) infiltrated with an ablative resin system: phenolic (Conformal-PICA) or silicone (Conformal-SICA). The test demonstrated a successful performance of both the conformable ablators for heat flux conditions between 50-500 W/sq cm. The recession and temperature profile for these materials were comparable to PICA proving them to be viable alternatives for TPS technology development for future missions.
The results of an experimental evaluation of ablative materials suitable for the production of light weight, low cost rocket engine combustion chambers and nozzles are presented. Ten individual specimens of four different compositions of silica cloth-reinforced phenolic resin materials were evaluated for comparative erosion in a subscale rocket engine combustion chamber. Gaseous hydrogen and gaseous oxygen were used as propellants, operating at a nominal chamber pressure of 1138 kPa (165 psi) and a nominal mixture ratio (O/F) of 3.3. These conditions were used to thermally simulate operation with RP-1 and liquid oxygen, and achieved a specimen throat gas temperature of approximately 2456 K (4420 R). Two high-density composition materials exhibited high erosion resistance, while two low-density compositions exhibited approximately 6-75 times lower average erosion resistance. The results compare favorably with previous testing by NASA and provide adequate data for selection of ablatives for low pressure, low cost rocket engines.
Thermal–hydraulics (T-H) experiments have been on the progress to evaluate boiling heat transfer characteristics of accident tolerant fuel (ATF) candidates for further supporting the core-loading of these advanced ATF concepts in light water reactors (LWRs). Here this study covers recent experimental studies of ATF claddings and summarizes some significant results. Recent T-H experimental results of ATF cladding candidates demonstrated that the material thermal–physical properties have pronounced effects on critical heat flux (CHF). Such effects have not been well resolved in the current physics-governing models. These effects of cladding materials on CHF could be potentially rationalized by the material-conjugated boiling heat transfer, where the material-dominated heat conduction competes with the flow boiling-dominated heat convection. As progressively increasing the mass flux and/or liquid subcooling, CHF differences between different materials gradually decrease, which is in agreement with the recent T-H experimental results of ATF claddings. This is because the dominance of heat convection over heat conduction is primarily improved by liquid subcooling and/or mass flow rate. It is noteworthy that surface oxidization of claddings may have unknown impacts on T-H performances because the formation of oxide layers on cladding surfaces introduces variations of material thermal–physical properties and then changes the surface morphological features, which results in some difficulties in evaluating the thermal safety margins of ATF claddings.
Materials were evaluated that could be used in manufacturing electrical resistance strain gages for static strain measurements at temperatures at or above 1273 K. Strain gage materials must have a characteristic response to strain, temperature and time that is reproducible or that varies in a predictable manner within specified limits. Several metallic alloys were evaluated, as well as a series of transition metal carbides, nitrides and silicides.
Materials for solar-cell module construction have been studied on the basis of limited real-time outdoor exposure evaluations. The materials tested included transmission samples, sub-modules, and actual solar cells. The results suggest that glass, fluorinated ethylene propylene, and perfluoroalkoxy are good materials for the covering or encapsulation of solar-cell modules. In all cases, dirt accumulation and cleanability are important factors.
The friction and wear properties of two groups of magnetic fluids, one developed at NASA Lewis Research Center and a commercial fluid, were evaluated for boundary lubrication. Friction and wear measurements were made using a pin-on-disk apparatus. Three different ball materials were evaluated, (1) 440C, (2) Al2O3, and (3) Si3N4 against 440C disks. The first class of magnetic fluids have a low vapor pressure hydrocarbon base oil and are suitable for space application. Four variations of this fluid were evaluated: (1) the base oil, (2) base oil with anti-wear additives, (3) a 100 Gauss strength magnetic fluid, and (4) a 400 gauss magnetic fluid. The commercial fluid base oil and four different magnetic particle concentration levels have been evaluated. A space qualified fluorinated lubricant was tested for base line comparison. Hardness, optical microscopy, surface profilometry, and surface analysis were used to characterize the test specimens. Friction was unaffected by the concentration of magnetic particles. Wear rates for magnetic fluids were slightly higher than the base oil. The low vapor pressure magnetic fluid has better wear characteristics than the space qualified fluorinated lubricant.
The Materials on International Space Station Experiment (MISSE) is being conducted with funding from NASA and the U.S. Department of Defense, in order to evaluate candidate materials and processes for flight hardware. MISSE modules include test specimens used to validate NASA technical standards for part markings exposed to harsh environments in low-Earth orbit and space, including: atomic oxygen, ultraviolet radiation, thermal vacuum cycling, and meteoroid and orbital debris impact. Marked test specimens are evaluated and then mounted in a passive experiment container (PEC) that is affixed to an exterior surface on the International Space Station (ISS). They are exposed to atomic oxygen and/or ultraviolet radiation for a year or more before being retrieved and reevaluated. Criteria include percent contrast, axial uniformity, print growth, error correction, and overall grade. MISSE 1 and 2 (2001-2005), MISSE 3 and 4 (2006-2007), and MISSE 5 (2005-2006) have been completed to date. Acceptable results were found for test specimens marked with Data Matrix(TradeMark) symbols by Intermec Inc. and Robotic Vision Systems Inc using: laser bonding, vacuum arc vapor deposition, gas assisted laser etch, chemical etch, mechanical dot peening, laser shot peening, laser etching, and laser induced surface improvement. MISSE 6 (2008-2009) is exposing specimens marked by DataLase(Registed TradeMark), Chemico technologies Inc., Intermec Inc., and tesa with laser-markable paint, nanocode tags, DataLase and tesa laser markings, and anodized metal labels.
This paper presents the current status of the ART program for the Future Attack Airvehicle. Consideration is given to the general configuration, the weights methodology, the reliability methodology, the noise evaluation, and materials analyses. It is shown that the methodologies developed for weights analysis and reliability will be useful in future design concept evaluations and that the noise prediction methodology under development can provide an indication of noise levels during the design process.
Aluminum-Lithium (AL-Li) alloys offer significant performance benefits for aerospace structural applications due to their higher specific properties compared with conventional aluminum alloys. For example, the application of an Al-Li alloy to the space shuttle external cryogenic fuel tank contributed to the weight savings that enabled successful deployment of International Space Station components. The composition and heat treatment of this alloy were optimized specifically for strength-toughness considerations for an expendable cryogenic tank. Time dependent properties related to reliability, such as thermal stability, fatigue, and corrosion, will be of significant interest when materials are evaluated for a reusable cryotank structure. As most aerospace structural hardware is weight sensitive, a reusable cryotank will be designed to the limits of the materials mechanical properties. Therefore, this effort was designed to establish the effects of thermal exposure on the mechanical properties and microstructure of one relatively production mature alloy and two developmental alloys C458 and L277. Tensile and fracture toughness behavior was evaluated after exposure to temperatures as high as 3oooF for up to IO00 hrs. Microstructural changes were also evaluated to correlate with the observed data trends. The ambient temperature parent metal data showed an increase in strength and reduction in elongation after exposure at lower temperatures. Strength reached a peak with intermediate temperature exposure followed by a decrease at highest exposure temperature. Characterizing the effect of thermal exposure on the properties of Al-Li alloys is important to defining a service limiting temperature, exposure time, and end-of-life properties.
Progress in the application of ultrasonic techniques to nondestructive measurement of mechanical strength of engineering materials is reviewed. A dormant concept in nondestructive evaluation (NDE) is invoked. The availability of ultrasonic methods that can be applied to actual parts to assess their potential susceptibility to failure under design conditions is discussed. It was shown that ultrasonic methods yield measurements of elastic moduli, microstructure, hardness, fracture toughness, tensile strength, yield strength, and shear strength for a wide range of materials (including many types of metals, ceramics, and fiber composites). It was also indicated that although most of these methods were shown feasible in laboratory studies, more work is needed before they can be used on actual parts in processing, assembly, inspection, and maintenance lines.
Use of masks is a primary tool to prevent the spread of the novel COVID-19 virus resulting from unintentional close contact with infected individuals. However, detailed characterization of the chemical properties and physical structure of common mask materials is lacking in the current literature. In this study, a series of commercial masks and potential mask materials, including 3M Particulate Respirator 8210 N95, a material provided by Oak Ridge National Laboratory Carbon Fiber Technology Facility (ORNL/CFTF), and a Filti Face Mask Material, were characterized by a suite of techniques, including scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Wetting properties of the mask materials were quantified by measurements of contact angle with a saliva substitute. Mask pass-through experiments were performed using a dispersed metal oxide nanoparticle suspension to model the SARS-CoV-2 virus, with quantification via spatially resolved X-ray fluorescence mapping. Notably, all mask materials tested provided a strong barrier against respiratory droplet breakthrough. The comparisons and characterizations provided in this study provide useful information when evaluating mask materials for respiratory protection.
Currently the United States relies on a single source, foreign company, Eumeca (formerly Normetex) for the supply of an all metal vacuum scroll pump to process tritium. This “one of a kind”, all metal, vacuum scroll pump utilizes no “wetted”, polymeric materials that degrade prematurely when exposed to tritium. U.S. based vacuum scroll pump suppliers typically utilize a polymer, Teflon®, as a tip seal material at the edge of the scroll impellers for proper pump function. Teflon® is known to degrade within a relatively short time frame (approximately 1 year) when continually exposed to tritium gas. This degradation results in “flaking” of the Teflon® material which results in particulate contamination of the process gas stream. While filtration of the particulate is possible, doing so requires additional maintenance which is costly in a glovebox environment. In addition, filtration can degrade pumping system performance as particulate collects in the filter media over time. To date, all of the well established U.S and European based vacuum scroll pump manufacturers have been uninterested in developing an all metal vacuum scroll pump that does not use a polymeric scroll tip seal. This position is taken as the vacuum scroll pump manufacturers do not see a large enough market to make it profitable for them to develop and market an all metal vacuum scroll pump. In the mid 2000s, one company, Air Squared, Inc., a small Original Equipment Manufacturer (OEM) specializing in design and fabrication of custom scroll vacuum pumps and compressors, was willing to pursue the effort. The first design effort incorporated Vespel® as a polymeric tip seal material. Results of this effort led to realizing the affect that the Met-Bel MB-601 metal bellows pump has on performance when used as a backing pump for an all metal vacuum scroll pump without a scroll tip seal. As a result, Air Squared subsequently designed an all metal vacuum scroll pump without a tip seal material for evaluation. Although the initial, all metal version of the Air Squared pump was found deficient in regard to scroll impeller stiffness, which resulted in scroll contact, general design and pump performance was verified to be adequate. SRS PDRD Project 19039 was launched in 2019 as a 3rd attempt with Air Squared, Inc. in regard to development of an all metal vacuum scroll pump for consideration as an equivalent to the Eumeca/ Normetex pump. The effort specified 300 series stainless steel for the scroll impellers, all metal sealing, and design to meet tritium throughput and ultimate vacuum requirements. In addition, a 60 psig design pressure rating requirement was specified for the pump containment boundary. The 3rd generation Air Squared pump has been designed, fabricated, and has received preliminary testing. Preliminary testing has indicated proper leak tightness and pump performance. However, work continues regarding development of a pumping chamber containment bellows that can be subjected to 66 psig without damage to the bellows. Work will continue in 2020 and 2021 to pursue a pumping chamber containment bellows that meets the pressure rating requirement.
This paper presents the details of a test program for the evaluation of the electrostatic discharge susceptibility of extravehicular activity equipment in polar orbits. In this program, laboratory simulation tests were performed to obtain the charging and ESD characteristics of the spacesuit material. The results from the simulation tests were used to generate the parameters for a system level ESD test for the existing EVA equipment. These test parameters were also used as a guide for the selection of the test apparatus.
The use of solid particles as a heat transfer medium is being explored for concentrated solar power plants (CSP) to increase their efficiency by achieving operating temperature >700 °C. During operation, these hot particles are expected to move along the various components within the collector system, resulting in material degradation from a combination of high-temperature oxidation and erosion. In the present study, the performance of candidate materials was evaluated through a series of abrasion erosion experiments at room temperature as well as at 800 °C. Wear in metallic and refractory type materials was investigated using CarboBead® HSP 40/70 particles inside a resistance heated kiln. Furthermore, cross-sectional scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) analysis on the specimens tested at 800 °C determined that the specific wear rate in Inconel 740H and stainless steel 316 metallic specimens was influenced by the thermally grown oxide morphology. High chromium Inconel 740H specimens exhibited greater resistance to wear with a steady state specific wear rate of 1.92E-4 mm 3 N -1 m –1 compared to 5.7E-3 mm 3 N -1 m –1 for Stainless Steel 316.