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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Nonlinear Thermal Analyses of a Liquid Hydrogen Tank Wall

A thermal evaluation of a composite tank wall design for a liquid hydrogen tank was performed in the present study. The primary focus of the current effort was to perform one-dimensional, temperature nonlinear, transient thermal analyses to determine the through-the-thickness temperature profiles. These profiles were used to identify critical points within the flight envelope that could have detrimental effects on the adhesive bondlines used in the construction of the tank wall. Additionally, this paper presents the finite element models, analysis strategies, and thermal analysis results that were determined for several vehicle flight conditions. The basic tank wall configuration used to perform the thermal analyses consisted of carbon-epoxy facesheets and a Korex honeycomb core sandwich that was insulated with an Airex cryogenic foam and an Alumina Enhanced Thermal Barrier (AETB-12). Nonlinear, transient thermal analyses were conducted using the ABAQUS finite element code. Tank wall models at a windward side location on the fuel tank were analyzed for three basic flight conditions: cold-soak (ground-hold), ascent, and re-entry. Additionally, three ambient temperature boundary conditions were applied to the tank wall for the cold-soak condition, which simulated the launch pad cooldown process. Time-dependent heating rates were used in the analyses of the ascent and reentry segments of the flight history along with temperature dependent material properties. The steady-state through-the-thickness temperature profile from the cold-soak condition was used as the initial condition for the ascent analyses. Results from the nonlinear thermal analyses demonstrated very good correlation with results from similar models evaluated by Northrop- Grumman using a different analysis tool. Wall through-the-thickness temperature gradients as a function of flight time were obtained for future incorporation into a full-scale thermostructural analysis to evaluate the adhesive bondlines. As a result of the thermal analyses conducted, a sufficient level of confidence was demonstrated in the thermal modeling and analysis capabilities of ABAQUS to warrant future use as a thermo-structural analysis tool to evaluate cryogenic tank wall designs.

Smeltzer, Stanley S., III↗
NASA NTRS2010

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

We describe the fabrication and thermal-stability analysis and test of a composite demonstration model of the Scanning Microwave Limb Sounder (SMLS) primary reflector, having full 4m height and 1/3 the width planned for flight. SMLS is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission between 180 and 660 GHz. Current MLS instruments in low Earth orbit scan pencil-beam antennas (sized to resolve about one scale height) vertically over the atmospheric limb. SMLS, planned for the Global Atmospheric Composition Mission of the NRC Decadal Survey, adds azimuthal scanning for better horizontal and temporal resolution and coverage than typical orbit spacing provides. SMLS combines the wide scan range of the parabolic torus with unblocked offset Cassegrain optics. The resulting system is diffraction-limited in the vertical plane but highly astigmatic in the horizontal, having a beam aspect ratio [tilde operator]1:20. Symmetry about the nadir axis ensures that beam shape is nearly invariant over +/-65(white bullet) azimuth. The a feeds a low-noise SIS receiver whose FOV is swept over the reflector system by a small scanning mirror. Using finiteelement models of antenna reflectors and structure, we evaluate thermal deformations and the resulting optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during wide-range (ambient+[-97,+75](white bullet) C) thermal soak tests of the primary in a chamber. This range exceeds predicted orbital soak ranges by large factors, implying in-orbit thermal stability of 0.21(mu)m rms/(white bullet)C, which meets SMLS requirements.

Thermal stability tests↗
NASA NTRS1972

Potentiometer, constant tension and lubrication device

Wiper assembly is described for feedback potentiometers which provides self cleaning, self lubrication, and tension within controlled limits. Each end of the assembly contains loose fitting leather pad thoroughly soaked in wiper lubricating fluid. Cleaning and lubrication of potentiometer resulting from use of lubrication soaked leather accomplishes noise free operation.

Smith, H. J.↗
NASA NTRS1974

Effect of chromia doping of thermal stability of silica fibers

Commercial silica fibers of the type being evaluated for reusable surface insulation for reentry vehicles were found to be porous and composed of subfibers. The effect on shrinkage and devitrification of soaking such silica fibers in water, acetic acid, chromium acetate, and chromium nitrate solutions was studied. Felted specimens made of chromia-doped fibers shrunk only about one-half as much as those made of untreated fibers after exposure in air for 4 hours at 1300 C. The devitrification rate of fibers given prolonged soaks in chromium nitrate was as low as that of as-received fibers.

Zaplatynsky, I.↗
NASA NTRS1974

M558 radioactive tracer diffusion

This experiment was performed in Skylab 3 with two objectives in mind. First, the experimental self-diffusion coefficients for liquid zinc were to be determined in a convection-free environment. Secondly the reduction in convective mixing in earth gravity by going into the zero-gravity environment of space was to be estimated. The experiment was designed to utilize high temperatures and linear thermal gradients provided by the M518 Multipurpose Electric Furnace, and the radioactivity of zinc-65 of 245-day half-life to investigate self-diffusion in liquid zinc. The distribution of zinc-65 tracer, after melting, maintaining at soak temperature for 1 hour of soak time and then resolidifying, was obtained by sample sectioning. The concentration of activity of each section (microcurie-gram) was plotted against positions along the sample axial and radial position. Experimental data and theoretical results from solution of Fick's law of diffusion in one dimensional were compared. Samples tested on earth showed very rapid diffusion. Diffusion coefficient in unit gravity was 50 times the zero-gravity diffusion coefficient of Skylab.

Ukanwa, A. O.↗
NASA NTRS1974

Outer planet probe entry thermal protection. II - Heat shielding requirements

Solutions are presented for the material thermal response for heat shields of blunt probes entering Saturn and Uranus. Both monolithic and sandwich concepts were considered having exposed charring ablative or reflective materials. The solutions show that (1) Teflon heat shields are sized by mass loss considerations, other materials (unless entering the Uranus cold-dense atmosphere) by heat soak considerations, (2) steeper entries require less heat shield mass, (3) sizing requirements vary little about the bodies for heat soak dominated materials, and (4) carbon-phenolic appears superior overall, but silica is superior for the steeper entries and the high helium content atmospheres.

Nicolet, W. E.↗
NASA NTRS1974

LK21T1 S/N V-3 infrared detector

An infrared detector was fabricated to determine the feasibility of atmospheric sounding from synchronous orbit for water vapor and carbon dioxide. The device was extensively tested both before and after a 24-hour soak at 50 C and relative humidity of 95 percent. No degradation in performance as a result of the soak was observed. The device contains a single photoconductive HgCdTe element designed to operate in the six to fifteen micron region.

Source record↗
NASA NTRS1976

Effect of water and ice on strength and fracture toughness of intermittently bonded boron-epoxy composites

The effects of water and ice on the strength and fracture toughness of boron-epoxy composites with polyurethane intermittent bonding have been investigated. Neither simple soaking in water nor soaking followed by freezing and thawing have marked effects on the strength of the fully-coated composites, but they have disastrous effects on the uncoated composites. Toughness is affected only marginally, with some small reductions in the fully-coated samples, and with essentially no effect on the uncoated composites. An analysis is presented which explains adequately the experimental strength and toughness results obtained, and which is based on an argument that water absorption reduces the interfacial shear strength only of the uncoated areas and not those regions coated by the polyurethane varnish. The results indicate that the advantages of appropriate intermittent bonding (i.e., high strength combined with high toughness) are retained in wet conditions so that such composites may be favorably used in such adverse environmental conditions.

Atkins, A. G.↗
NASA NTRS1977

LPE growth of GaAs-Ga/1-x/Al/x/As solar cells

The procedures for the liquid phase epitaxial (LPE) growth of high efficiency p-Ga(1-x)Al(x)As,p-GaAs,n-GaAs solar cells have been developed. The methods are based on forming the structure by a one-step process in which the Zn-diffused p-n junction in the n-type GaAs substrate forms in conjunction with the LPE growth of the Zn-doped p-Ga(1-x)Al(x)As layer. For structures with 1-10 micron thick Ga(1-x)Al(x)As layers, an isothermal soak of the GaAs substrate in a saturated Ga-Al-As: Zn melt followed by ramp cooling produces good cells. For structures with less than one micron thick Ga(1-x)Al(x)As layers, it is necessary to isothermally soak the GaAs substrate in an undersaturated melt, and ramp cooling is not required.

Woodall, J. M.↗
NASA NTRS1982

Water absorption and desorption in shuttle ablator and insulation materials

Shuttle systems ablator and insulation materials underwent water soak with subsequent water desorption in vacuum. Water accumulation in these materials after a soak for 24 hours ranged from +1.1% for orbiter tile to +161% for solid rocket booster MSA-1. After 1 minute in vacuum, water retention ranged from none in the orbiter tile to +70% for solid rocket booster cork.

Whitaker, A. F.↗
NASA NTRS1984

Starting Silicon-Ribbon Growth Automatically

Semiautomatic system starts growth of silicon sheets more reliably than system with purely manual control. Control signals for starting sheetcrystal growth consist of ramps (during which signal changes linearly from one value to another over preset time interval) and soaks (during which signal remains constant). Ramps and soaks for best temperature and pulling speed determined by experimentation.

Mchugh, J. P.↗
NASA NTRS1984

Binder for Carbon-Fiber Coating

Insoluble, even coating formed by soaking in polyacrylic acid. Carbon fiber material prepared by soaking in solution of 20 percent polyacrylic acid in water. Material blotted and dried at 120 degrees C for at least 2 hours. Dried material reacted with boiling aqueous solution of calcium acetate. Treated material removed from boiling solution, blotted, dried at 120 degrees C, washed with distilled water, and dried again.

Dowler, W. L.↗
NASA NTRS1992

Environmental qualification testing of payload G-534, the Pool Boiling Experiment

Payload G-534, the prototype Pool Boiling Experiment (PBE), is scheduled to fly on the STS-47 mission in September 1992. This paper describes the purpose of the experiment and the environmental qualification testing program that was used to prove the integrity of the hardware. Component and box level vibration and thermal cycling tests were performed to give an early level of confidence in the hardware designs. At the system level, vibration, thermal extreme soaks, and thermal vacuum cycling tests were performed to qualify the complete design for the expected shuttle environment. The system level vibration testing included three axis sine sweeps and random inputs. The system level hot and cold soak tests demonstrated the hardware's capability to operate over a wide range of temperatures and gave wider latitude in determining which shuttle thermal attitudes were compatible with the experiment. The system level thermal vacuum cycling tests demonstrated the hardware's capability to operate in a convection free environment. A unique environmental chamber was designed and fabricated by the PBE team and allowed most of the environmental testing to be performed within the hardware build laboratory. The completion of the test program gave the project team high confidence in the hardware's ability to function as designed during flight.

Sexton, J. Andrew↗
NASA NTRS1992

Environmental qualification testing of the prototype pool boiling experiment

The prototype Pool Boiling Experiment (PBE) flew on the STS-47 mission in September 1992. This report describes the purpose of the experiment and the environmental qualification testing program that was used to prove the integrity of the prototype hardware. Component and box level vibration and thermal cycling tests were performed to give an early level of confidence in the hardware designs. At the system level, vibration, thermal extreme soaks, and thermal vacuum cycling tests were performed to qualify the complete design for the expected shuttle environment. The system level vibration testing included three axis sine sweeps and random inputs. The system level hot and cold soak tests demonstrated the hardware's capability to operate over a wide range of temperatures and gave the project team a wider latitude in determining which shuttle thermal altitudes were compatible with the experiment. The system level thermal vacuum cycling tests demonstrated the hardware's capability to operate in a convection free environment. A unique environmental chamber was designed and fabricated by the PBE team and allowed most of the environmental testing to be performed within the project's laboratory. The completion of the test program gave the project team high confidence in the hardware's ability to function as designed during flight.

Sexton, J. Andrew↗
NASA NTRS1994

Three-frequency, polarimetric, airborne SAR observations of the Greenland ice sheet

Synthetic aperture radar (SAR) images of the Greenland ice sheet collected by an airborne system clearly reveal the four melting facies of this sheet defined 30 years ago from snow stratigraphy studies by glaciologists. In particular, the radar echoes from the percolation facies have radiometric and polarimetric characteristics that are unique among terrestrial surfaces, but that resemble the exotic radar echoes recorded from the icy Galilean satellites. There, the radar signals interact with subsurface, massive ice features created in the cold, dry snow by seasonal melting and refreezing events. The subsurface features act as efficient reflectors of the incident radiation most likely via internal reflections. In the soaked-snow facies, the radar reflectivity is much lower because radar signals are attenuated by the wetter snow before they can interact with subsurface structures. Inversion algorithms to derive geophysical information from the SAR data are developed in both cases to estimate snow wetness in the soaked-snow facies and the mass of ice water retained in the percolation facies.

Rignot, E.↗
NASA NTRS2003

Fabrication of Large Bulk High Temperature Superconducting Articles

A method of fabricating large bulk high temperature superconducting articles which comprises the steps of selecting predetermined sizes of crystalline superconducting materials and mixing these specific sizes of particles into a homogeneous mixture which is then poured into a die. The die is placed in a press and pressurized to predetermined pressure for a predetermined time and is heat treated in the furnace at predetermined temperatures for a predetermined time. The article is left in the furnace to soak at predetermined temperatures for a predetermined period of time and is oxygenated by an oxygen source during the soaking period.

Ronald Koczor↗
NASA NTRS2009

Operation of SOI P-Channel Field Effect Transistors, CHT-PMOS30, under Extreme Temperatures

Electronic systems are required to operate under extreme temperatures in NASA planetary exploration and deep space missions. Electronics on-board spacecraft must also tolerate thermal cycling between extreme temperatures. Thermal management means are usually included in today s spacecraft systems to provide adequate temperature for proper operation of the electronics. These measures, which may include heating elements, heat pipes, radiators, etc., however add to the complexity in the design of the system, increases its cost and weight, and affects its performance and reliability. Electronic parts and circuits capable of withstanding and operating under extreme temperatures would reflect in improvement in system s efficiency, reducing cost, and improving overall reliability. Semiconductor chips based on silicon-on-insulator (SOI) technology are designed mainly for high temperature applications and find extensive use in terrestrial well-logging fields. Their inherent design offers advantages over silicon devices in terms of reduced leakage currents, less power consumption, faster switching speeds, and good radiation tolerance. Little is known, however, about their performance at cryogenic temperatures and under wide thermal swings. Experimental investigation on the operation of SOI, N-channel field effect transistors under wide temperature range was reported earlier [1]. This work examines the performance of P-channel devices of these SOI transistors. The electronic part investigated in this work comprised of a Cissoid s CHT-PMOS30, high temperature P-channel MOSFET (metal-oxide semiconductor field-effect transistor) device [2]. This high voltage, medium-power transistor is designed for geothermal well logging applications, aerospace and avionics, and automotive industry, and is specified for operation in the temperature range of -55 C to +225 C. Table I shows some specifications of this transistor [2]. The CHT-PMOS30 device was characterized at various temperatures over the range of -190 C to +225 C in terms of its voltage/current characteristic curves. The test temperatures included +22, -50, -100, -150, -175, -190, +50, +100, +150, +175, +200, and +225 C. Limited thermal cycling testing was also performed on the device. These tests consisted of subjecting the transistor to a total of twelve thermal cycles between -190 C and +225 C. A temperature rate of change of 10 C/min and a soak time at the test temperature of 10 minutes were used throughout this work. Post-cycling measurements were also performed at selected temperatures. In addition, re-start capability at extreme temperatures, i.e. power switched on while the device was soaking for a period of 20 minutes at the test temperatures of -190 C and +225 C, was investigated.

Patterson, Richard↗
NASA NTRS2012

Supercritical CO2 Cleaning System for Planetary Protection and Contamination Control Applications

Current spacecraft-compatible cleaning protocols involve a vapor degreaser, liquid sonication, and alcohol wiping. These methods are not very effective in removing live and dead microbes from spacecraft piece parts of slightly complicated geometry, such as tubing and loosely fitted nuts and bolts. Contamination control practices are traditionally focused on cleaning and monitoring of particulate and oily residual. Vapor degreaser and outgassing bakeout have not been proven to be effective in removing some less volatile, hydrophilic biomolecules of significant relevance to life detection. A precision cleaning technology was developed using supercritical CO2 (SCC). SCC is used as both solvent and carrier for removing organic and particulate contaminants. Supercritical fluid, like SCC, is characterized by physical and thermal properties that are between those of the pure liquid and gas phases. The fluid density is a function of the temperature and pressure. Its solvating power can be adjusted by changing the pressure or temperature, or adding a secondary solvent such as alcohol or water. Unlike a regular organic solvent, SCC has higher diffusivities, lower viscosity, and lower surface tension. It readily penetrates porous and fibrous solids and can reach hard-to-reach surfaces of the parts with complex geometry. Importantly, the CO2 solvent does not leave any residue. The results using this new cleaning device demonstrated that both supercritical CO2 with 5% water as a co-solvent can achieve cleanliness levels of 0.01 mg/cm2 or less for contaminants of a wide range of hydrophobicities. Experiments under the same conditions using compressed Martian air mix, which consists of 95% CO2, produced similar cleaning effectiveness on the hydrophobic compounds. The main components of the SCC cleaning system are a high-pressure cleaning vessel, a boil-off vessel located downstream from the cleaning vessel, a syringe-type high-pressure pump, a heat exchanger, and a back pressure regulator (BPR). After soaking the parts to be cleaned in the clean vessel for a period, the CO2 with contaminants is flushed out of the cleaning vessel using fresh CO2 in a first-in-first-out (FIFO) method. The contaminants are either precipitating out in the boil-off container or being trapped in a filter subsystem. The parts to be cleaned are secured in a basket inside and can be rotated up to 1,400 rpm by a magnetic drive. The fluid flows within the vessel generate tangential forces on the parts surfaces, enhancing the cleaning effectiveness and shortening the soaking time. During the FIFO flushing, the pump subsystem pushes fresh CO2 into the cleaning vessel at a constant flow rate between 0.01 and 200 mL/min, while the BPR regulates the pressure in the cleaning vessel to within 0.1 bar by controlling the needle position in an outlet valve. The fresh CO2 gas flows through the heat exchanger at a given temperature before entering the cleaning vessel. A platinum resistance thermometer (PRT) reads the cleaning vessel interior temperature that can be controlled to within 0.1 K. As a result, cleaning vessel temperature remains constant during the FIFO flushing. There is no change in solvent power during FIFO flushing since both temperature and pressure inside the cleaning vessel remain unchanged, thus minimizing contaminants left behind. During decompression, both temperature and pressure are strictly controlled to prevent bubbles from generating in the cleaning vessel that could stir up the contaminants that sank to the bottom by gravity.

Lin, Ying↗