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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Effects of Cryogenic Temperature on Fracture Toughness of Core-Shell Rubber (CSR) Toughened Epoxy Nanocomposites

This study investigated the effects of core-shell rubber (CSR) nanoparticles on the mechanical properties and fracture toughness of an epoxy resin at ambient and liquid nitrogen (LN2) temperatures. Varying amounts of Kane Ace MX130 toughening agent were added to a commercially available EPON 862/Epikure W epoxy resin. Elastic modulus was calculated using quasi-static tensile data. Fracture toughness was evaluated by the resulting breaking energy measured in Charpy impact tests conducted on an instrumented drop tower. The size and distribution of the CSR nanoparticles were characterized using Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). Scanning Electron Microscopy (SEM) was used to study the fracture surface morphology. The addition of the CSR nanoparticles increased the breaking energy with negligible change in elastic modulus and ultimate tensile stress (UTS). At ambient temperature the breaking energy increased with increasing additions of the CSR nanoparticles, while at LN2 temperatures, it reached a maximum at 5 wt% CSR concentration. KEY WORDS: liquid nitrogen (LN2) properties, fracture toughness, core-shell rubber (CSR).

Wang, J.↗
NASA NTRS2013

The Total Hemispheric Emissivity of Painted Aluminum Honeycomb at Cryogenic Temperatures

NASA uses high-emissivity surfaces on deep-space radiators or thermal radiation absorbers in test chambers. Aluminum honeycomb core material, when coated with a high-emissivity paint, provides a lightweight, mechanically robust, and relatively inexpensive black surface that retains its high emissivity down to low temperatures. At temperatures below about 100 Kelvin, this material performs much better than the paint itself. We measured the total hemispheric emissivity of various painted honeycomb configurations using an adaptation of an innovative technique developed for characterizing thin black coatings. These measurements were performed from room temperature down to 30 Kelvin. We describe the measurement technique and compare the results with predictions from a detailed thermal model of each honeycomb configuration.

Tuttle, J.↗
NASA NTRS2018

Observing Ice Sublimation From Water-Doped Lunar Simulant at Cryogenic Temperatures

NASA's Resource Prospector (RP) mission is intended to characterize the three-dimensional nature of volatiles in lunar polar and permanently shadowed regions. The Near-Infrared Volatile Spectrometer System (NIRVSS) observes while a drill penetrates to a maximum depth of 1 m. Any 10 cm increment of soil identified as containing water ice can be delivered to a heating crucible with the evolved gas delivered to a gas chromatograph / mass spectrometer. NIRVSS consists of two components; a spectrometer box (SB) and bracket assembly (BA), connected by two fiber optic cables. The SB contains separate short- and long-wavelength spectrometers, SW and LW respectively, that collectively span the 1600-3400 nm range. The BA contains an IR emitter (lamp), drill observation camera (DOC, 2048 x 2048 CMOS detector), 8 different wavelength LEDs, and a longwave calibration sensor (LCS) measuring the surface emissivity at four IR wavelengths. Tests of various RP sub-systems have been under-taken in a large cryo-vacuum chamber at Glenn Re-search Center. The chamber accommodates a tube (1.2 m high x 25.4 cm diameter) filled with lunar simulant, NU-LHT-3M, prepared with known abundances of water. Thermocouples are embedded at different depths, and also across the surface of the soil tube. In the chamber the tube is cooled with LN2 as the pressure is reduced to approx. 5-6x10(exp -6) Torr. For the May 2016 tests two soil tubes were prepared with initially 2.5 Wt.% water. The shroud surrounding the soil tube was held at different temperatures for each tube to simulate a warm and cold lunar environment. Table 1 provides a summary of experimental conditions and Figure 1 shows the nominal view of the NIRVSS components, the drill foot, and the top of the soil tube. Once the average soil temperature reached approx. 178 K, drilling commenced. During drilling activities NIRVSS was alternating between obtaining spectra and obtaining images. Here we discuss NIRVSS spectral data obtained during controlled drill percussions.

Roush, T. L.↗
NASA NTRS2019

Thermal Design and Analysis of Cooling SOFIA HIRMES to 4K Cryogenic Temperature Using Cryocooler

HIgh Resolution Mid-infrarEd Spectrometer (HIRMES) is a facility-class instrument aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) Aircraft Observatory. A TransMIT PTD 406C pulse tube cryocooler (PTC) is used to cool the optical bench and optical components to 4K. A second PTC is dedicated to cool the 3He/4He sorption cooler. The first stages of the PTCs share the heat load from the intermediate temperature stage. The second stage of the first PTC removes nearly all the heat load from the 4 degrees Kelvin stage. The results of thermal analysis show that the 4 degrees Kelvin stage of the HIRMES thermal subsystem meets all of its requirements using the 100 percent heat load margin approach and conservative modeling assumptions.

Cryostat↗
NASA NTRS2000

Evaluation of GE-167 Silicone Rubber (RTV) For Possible Service As A Moisture-Barrier For Certain Strain Gage Applications

The Langley Research Center uses strain gages in a wide variety of demanding test environments. Strain gage installations, depending on the testing scenario, may see high temperatures, cryogenic temperature, moisture accumulation, mechanical abuse, or any combination of these conditions. At Langley, there is often a need to provide protection for strain gages against moisture and mechanical abuse, especially when large-scale, harsh environment testing is to be encountered. This technical memorandum discusses the evaluation of a room temperature curing silicone rubber sealant manufactured by the General Electric Company for consideration as a moisture-barrier for certain strain gage installations.

Hare, David A.↗
NASA NTRS1992

Development of magnetostrictive active members for control of space structures

The goal of this Phase 2 Small Business Innovative Research (SBIR) project was to determine the technical feasibility of developing magnetostrictive active members for use as truss elements in space structures. Active members control elastic vibrations of truss-based space structures and integrate the functions of truss structure element, actively controlled actuator, and sensor. The active members must control structural motion to the sub-micron level and, for many proposed space applications, work at cryogenic temperatures. Under this program both room temperature and cryogenic temperature magnetostrictive active members were designed, fabricated, and tested. The results of these performance tests indicated that room temperature magnetostrictive actuators feature higher strain, stiffness, and force capability with lower amplifier requirements than similarly sized piezoelectric or electrostrictive active members, at the cost of higher mass. Two different cryogenic temperature magnetostrictive materials were tested at liquid nitrogen temperatures, both with larger strain capability than the room temperature magnetostrictive materials. The cryogenic active member development included the design and fabrication of a cryostat that allows operation of the cryogenic active member in a space structure testbed.

Johnson, Bruce G.↗
NASA NTRS2006

Comparison of the Effects of Tool Geometry for Friction Stir Welding Thin Sheet Aluminum Alloys for Aerospace Applications

In this presentation, the results of a recent study on the effect of pin tool design for friction stir welding thin sheets (0.040") of aluminum alloys 2024 and 7075 are provided. The objective of this study was to investigate and document the effect of tool shoulder and pin diameter, as well as the presence of pin flutes, on the resultant microstructure and mechanical properties at both room temperature and cryogenic temperature. Specifically, the comparison between three tools will include: FSW process load analysis (tool forces required to fabricate the welds), Static Mechanical Properties (ultimate tensile strength, yield strength, and elongation), and Process window documenting the range of parameters that can be used with the three pin tools investigated. All samples were naturally aged for a period greater than 10 days. Prior research has shown 7075 may require post weld heat treatment. Therefore, an additional pair of room temperature and cryogenic temperature samples was post-weld aged to the 7075-T7 condition prior to mechanical testing.

Merry, Josh↗
NASA NTRS1998

Characterization of Al-Cu-Li Alloy 2090 Near Net Shape Extrusion

Aluminum-lithium (Al-Li) alloys near net shape extrusions are being evaluated for potential application in launch vehicle structures. The objective of this study was to determine tensile and fracture properties, corrosion resistance, and weldability of integrally stiffened panels of Al-Cu-Li alloy 2090 in the T8 temper. The microstructure was pre-dominantly unrecrystallized. Texture analyses revealed the presence of fiber components in the stiffeners and a combination of fiber and rolling components in the skin. Variations in grain morphology and texture through the extruded cross section were correlated with the tensile, fracture, and corrosion behavior. Tensile strengths at room and cryogenic temperatures of the 2090 extrusions were similar to other 2090 product forms and were higher than 2219-T87, the primary structural material in the Space Shuttle external tank; however, ductilities were lower. The fracture resistance of the 2090 extrusion was lower than 2219-T87 plate at room temperature. At cryogenic temperatures, tensile ductility and fracture behavior of the 2090 extrusion were similar to other 2090 product forms but were lower than 2219-T87 plate. The exfoliation and stress corrosion resistance of the 2090 extrusion compared favorably with the characteristics of other 2090 product forms. The weldability and weldment properties of the extrusions were similar to 2090 and 2219 plates.

Birt, M. J.↗
NASA NTRS2026

Fatigue Life of Flow-Formed Aluminum 2195 and 6061 Alloys

The successful design and fabrication of metallic cryotanks for commercial aviation applications require lightweight, durable materials capable of withstanding high pressures and cryogenic temperatures through tens of thousands of thermomechanical refueling cycles. Flow forming is an advanced manufacturing technique that offers high-rate production and scalability for fabricating integrally stiffened cylinders suitable for cryotank applications. This work establishes the durability of flow-formed aluminum alloys by characterizing their fatigue life performance under conditions that mimic cryotank refueling cycles. Residual stresses in flow-formed aluminum-lithium (Al-Li) 2195-T6 cylinders were assessed using the contour method and found to be minimal. Fatigue life testing was conducted on flow-formed Al-Li 2195-T6 at room temperature and cryogenic temperatures (-321°F [-196°C]), with wrought Al-Li 2195-T6 serving as a baseline for comparison. Results showed that flow-formed materials exhibited fatigue performance comparable to or better than wrought materials, with no statistically significant differences observed between different specimen orientations relative to processing directions. Fractography revealed reduced delaminations in the flow-formed Al-Li 2195 samples as compared to wrought, indicating potential improvement to the microstructure that could result in improved service properties. Texture analysis using electron backscattered diffraction (EBSD) indicated recrystallization during heat treatment, potentially contributing to reduced delamination susceptibility. These findings demonstrating flow-formed material durability coupled with the high manufacturing efficiency of flow forming, makes flow forming an attractive process to produce aircraft cryotanks.

EBF3↗
NASA NTRS2008

Active Co-Storage of Cryogenic Propellants for Lunar Explortation

Long-term storage of cryogenic propellants is a critical requirement for NASA's effort to return to the moon. Liquid hydrogen and liquid oxygen provide the highest specific impulse of any practical chemical propulsion system, and thus provides the greatest payload mass per unit of launch mass. Future manned missions will require vehicles with the flexibility to remain in orbit for months, necessitating long-term storage of these cryogenic liquids. For decades cryogenic scientific satellites have used dual cryogens with different temperatures to cool instruments. This technology utilizes a higher temperature cryogen to provide a stage that efficiently intercepts a large fraction of the heat that would otherwise be incident on the lower temperature cryogen. This interception reduces the boil-off of the lower temperature cryogen and increasing the overall life-time of the mission. The Active Co-Storage concept is implemented similarly; the 101 K liquid oxygen thermally shields the 24 K liquid hydrogen. A thermal radiation shield that is linked to the liquid oxygen tank shrouds the liquid hydrogen tank, thereby preventing the liquid hydrogen tank from being directly exposed to the 300 K external environment. Modern cryocooler technology can eliminate the liquid oxygen boil-off and also cool the thermal radiation shield thereby reducing the liquid hydrogen boil-off to a small fraction of the unshielded rate. The thermal radiation shield can be a simple conductive shroud or a more sophisticated but lighter Broad Area Cooling (BAC) shroud. The paper describes the design impact of an active co-storage system for the Altair Descent Vehicle. This paper also compares the spacecraft-level impacts of the conductive shroud and the BAC shroud active co-storage concepts with a passive storage option in the context of the different scales of spacecraft that will be used for the lunar exploration effort - the Altair Ascent and Descent Vehicles, the Orion, and the Ares V Earth Departure Stage. The paper also reports on a subscale test of this active co-storage configuration. The test tank is 0.7 m in diameter, approximately one-third the dimension of tanks that would be needed in a lunar ascent module. A thin-walled fiberglass skirt supports and isolates the tank from a 100 K stage. A similar thin-walled skirt supports the lOOK stage from the ambient temperature structure. An aluminum shield with a heavy MLI blanket surrounds the tank and is attached at the 100 K stage. In this initial phase of the project, there is no tank on the 100 K stage, but it is actively cooled by a single-stage cryocooler similar in design to the one used on the RHESSI mission. The test configuration includes a number of innovative elements, including a helical support heat exchanger and an external thermodynamic vent/heat interception system. To avoid the complexity of an explosive gas handling system, testing will be done with liquid helium and liquid neon as simulant fluids. The properties of these fluids bracket the properties of liquid hydrogen. Instrumentation allows tank temperature and shield temperature profiles, tank liquid levels, and pressure drops through the flow lines, to be measured.

Mustafi, S.↗
NASA NTRS2003

Cryogenic Temperature-Gradient Foam/Substrate Tensile Tester

The figure shows a fixture for measuring the tensile strength of the bond between an aluminum substrate and a thermally insulating polymeric foam. The specimen is meant to be representative of insulating foam on an aluminum tank that holds a cryogenic liquid. Prior to the development of this fixture, tensile tests of this type were performed on foam/substrate specimens immersed in cryogenic fluids. Because the specimens were cooled to cryogenic temperatures throughout their thicknesses, they tended to become brittle and to fracture at loads below true bond tensile strengths. The present fixture is equipped to provide a thermal gradient from cryogenic temperature at the foam/substrate interface to room temperature on the opposite foam surface. The fixture includes an upper aluminum block at room temperature and a lower aluminum block cooled to -423 F (approx. -253 C) by use of liquid helium. In preparation for a test, the metal outer surface (the lower surface) of a foam/substrate specimen is bonded to the lower block and the foam outer surface (the upper surface) of the specimen is bonded to the upper block. In comparison with the through-the-thickness cooling of immersion testing, the cryogenic-to-room-temperature thermal gradient that exists during testing on this fixture is a more realistic approximation of the operational thermal condition of sprayed insulating foam on a tank of cryogenic liquid. Hence, tensile tests performed on this fixture provide more accurate indications of operational bond tensile strengths. In addition, the introduction of the present fixture reduces the cost of testing by reducing the amount of cryogenic liquid consumed and the time needed to cool a specimen.

Vailhe, Christophe↗