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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Cryogenic Insulation Bondline Studies for Reusable Launch Vehicles

Cryogenic insulations bonded to metallic substrates were characterized under simulated mission conditions representative for a reusable launch vehicle. The combined thermal and mechanical test consisted of 50 to a 100 cycles. These combined thermal and mechanical cycles simulated flight missions with temperatures ranging from -423 F to 450 F and a maximum mechanical tension load ranging from 20,000 lbs. to 97,650 lbs. The combined thermal and mechanical (uniaxial tension) test apparatus (1 ft. by 2 ft. Test Apparatus) developed at the NASA Langley Research Center, was used to perform cyclic tests on cryogenic insulations bonded to tank wall substrates. No visual delamination or degradation was observed in the cryogenic insulation-to-metallic substrate bondline or butt joints between cryogenic insulation panels. In addition, after cyclic testing was performed, residual property results from tension-pull and closed-cell content tests of the cryogenic insulations indicated a decrease in the bondline strength and closed-cell content.

Johnson, T. F.↗
NASA NTRS1981

Long term behavior of silicon germanium thermoelectric generators

Results of tests of the long term performance of SiGe radioisotope thermoelectric generators (RTG) are presented. Three modules were monitored for 17,000-32,300 hr at hot junction temperatures of 1,085, 1,055, and 1,000 C; coating the unicouples with a 12,000 A thick layer of Si3N4 protected the modules from Si sublimation. Output degraded less than 0.3-0.4%/1,000 hr over the testing period. Life tests on a multihundredwatt (MHW) SiGe generator with 312 couples at a hot shoe temperature of 1,040 C dealt with power of 150 W at 30 V, with 0.5%/1,000 hr performance degradation. Si deposition on the insulation was found to enhance electrical conductance until a saturation point was reached. Disassembly of a test module after 16,750 hr revealed a Mo build-up, SiN4 coating deterioration, and Ti diffustion from the hot shoe to cooler regions of the junction. The presence of an Al2O3 insulator was recognized as preventing coating loss. Performance records from the Voyager and Les-8 satellites' RTG's are compared and show similar, 0.25%/1,000 hr degradation rates; RTG storage is judged to be feasible and the tests lead to projections of a 600,000 hr lifetime for a SiGe RTG.

Shields, V.↗
DOE OSTI2024

A numerical study of process complexity in permafrost dominated regions

Numerical modeling of permafrost dynamics requires adequate representation of atmospheric and surface processes, a reasonable parameter estimation strategy, and site-specific model development. The three main research objectives of the study are: (i) to propose a novel methodology that determines the required level of surface process complexity of permafrost models by conducting parameter sensitivity and calibration, (ii) to design and compare three numerical models of increasing surface process complexity, and (iii) to calibrate and validate the numerical models at the Yakou catchment on the Qinghai-Tibet Plateau as an exemplary study site. The calibration was carried out by coupling the Advanced Terrestrial Simulator (numerical model) and PEST (calibration tool). Simulation results showed that (i) A simple numerical model that considers only subsurface processes can simulate active layer development with the same accuracy as other more complex models that include surface processes. (ii) Peat and mineral soil layer permeability, Van Genuchten alpha, and porosity are highly sensitive. (iii) Liquid precipitation aids in increasing the rate of permafrost degradation. (iv) Deposition of snow insulated the subsurface during the thaw initiation period. We have developed and released an integrated code that couples the numerical software ATS to the calibration software PEST. The numerical model can be further used to determine the impacts of climate change on permafrost degradation.

Calibration↗
NASA NTRS2013

Bismuth Passivation Technique for High-Resolution X-Ray Detectors

The Athena-plus team requires X-ray sensors with energy resolution of better than one part in 3,000 at 6 keV X-rays. While bismuth is an excellent material for high X-ray stopping power and low heat capacity (for large signal when an X-ray is stopped by the absorber), oxidation of the bismuth surface can lead to electron traps and other effects that degrade the energy resolution. Bismuth oxide reduction and nitride passivation techniques analogous to those used in indium passivation are being applied in a new technique. The technique will enable improved energy resolution and resistance to aging in bismuth-absorber-coupled X-ray sensors. Elemental bismuth is lithographically integrated into X-ray detector circuits. It encounters several steps where the Bi oxidizes. The technology discussed here will remove oxide from the surface of the Bi and replace it with nitridized surface. Removal of the native oxide and passivating to prevent the growth of the oxide will improve detector performance and insulate the detector against future degradation from oxide growth. Placing the Bi coated sensor in a vacuum system, a reduction chemistry in a plasma (nitrogen/hydrogen (N2/H2) + argon) is used to remove the oxide and promote nitridization of the cleaned Bi surface. Once passivated, the Bi will perform as a better X-ray thermalizer since energy will not be trapped in the bismuth oxides on the surface. A simple additional step, which can be added at various stages of the current fabrication process, can then be applied to encapsulate the Bi film. After plasma passivation, the Bi can be capped with a non-diffusive layer of metal or dielectric. A non-superconducting layer is required such as tungsten or tungsten nitride (WNx).

Chervenak, James↗
NASA NTRS1999

Thermal Control Replacement Materials Evaluated for Durability and Selected for the Hubble Space Telescope

During the Hubble Space Telescope (HST) second servicing mission, astronauts noticed that the outer layer of the multilayer insulation (MLI) was cracked in many locations around the telescope. The insulation s outer layer is composed of 5-mil (0.127 mm) Teflon FEP (DuPont; fluorinated ethylene propylene) with vapor-deposited aluminum (VDA) on the backside. The MLI blankets, which are used on over 80 percent of the external surface of the telescope, provide passive thermal control for equipment. Two large cracks were observed on the light shield directly above the high gain antenna. The upper light shield crack propagated from a cut placed in the blanket during installation around a handrail standoff. Two cracks propagated almost normal to each other, with the outer layer curling tightly as the cracks propagated. A second much larger vertical crack had started to curl and lift away from the telescope, as seen in the figure. MLI on the equipment bays was cracked extensively also, and in some areas it had pulled away from the bay. Continued degradation of the equipment bay insulation would potentially cause limited observations because of housekeeping boxes; for example, the data interface unit could overheat during some portions of the year, in certain sun angles.

deGroh, Kim K.↗
NASA NTRS1999

High Temperature Resistant Organopolysiloxane Coating for Protecting and Repairing Rigid Thermal Insulation

Ceramics are protected from high temperature degradation, including high temperature, oxidative, aeroconvective degradation by a high temperature and oxidation resistant coating of a room temperature curing, hydrolyzed and partially condensed liquid polyorganosiloxane to the surface of the ceramic. The liquid polyorganosiloxane is formed by the hydrolysis and partial condensation of an alkyltrialkoxysilane with water or a mixture of an alkyltrialkoxysilane and a dialkyldialkoxysilane with water. The liquid polyorganosiloxane cures at room temperature on the surface of the ceramic to form a hard, protective, solid coating which forms a high temperature environment, and is also used as an adhesive for adhering a repair plug in major damage to the ceramic. This has been found useful for protecting and repairing porous, rigid ceramics of a type used on reentry space vehicles.

Leiser, Daniel B.↗
DOE OSTI2025

Ultrastable Gold Nanostars via Bottlebrush-like Block Copolymers

Gold (Au) nanostars are plasmonic nanostructures possessing potentials for small molecule detection, photocatalytic activities, and photothermal therapy. However, Au nanostars synthesized in the traditional way are often plagued by poor photo, thermal, and chemical stabilities. Here, we report an unconventional route to the synthesis of ultrastable colloidal Au nanostars enabled by bottlebrush-like block copolymers (BBCPs), dispensing with the need for Au seeds. Crafting of Au nanostars using BBCPs is rendered by bridging the latter with Au 3+ ions as cross-linkers that have multiple coordination sites. Notably, the presence of a covalently tethered polymer shell on the surface of Au nanostars (i.e., polymer-ligated Au nanostars) imparts remarkably high stability under high temperature and laser excitation over conventional cetyltrimethylammonium bromide (CTAB)-mediated Au nanostars. Due to enhanced laser stability, plasmonic fields near Au nanostars can be visualized under high laser fluence by ultrafast electron microscopy (UEM) without morphological degradation. Notably, the presence of insulating polystyrene chains does not compromise the plasmonic field distribution, with the highest field intensity observed along the star arms. In conclusion, the greatly improved long-term photo, thermal, and chemical stabilities make Au nanostars a prospective noble metal nanomaterial for a range of sensing applications.

Cellulose↗
NASA NTRS1992

Pressurized Lunar Rover (PLR)

The objective of this project was to design a manned pressurized lunar rover (PLR) for long-range transportation and for exploration of the lunar surface. The vehicle must be capable of operating on a 14-day mission, traveling within a radius of 500 km during a lunar day or within a 50-km radius during a lunar night. The vehicle must accommodate a nominal crew of four, support two 28-hour EVA's, and in case of emergency, support a crew of six when near the lunar base. A nominal speed of ten km/hr and capability of towing a trailer with a mass of two mt are required. Two preliminary designs have been developed by two independent student teams. The PLR 1 design proposes a seven meter long cylindrical main vehicle and a trailer which houses the power and heat rejection systems. The main vehicle carries the astronauts, life support systems, navigation and communication systems, lighting, robotic arms, tools, and equipment for exploratory experiments. The rover uses a simple mobility system with six wheels on the main vehicle and two on the trailer. The nonpressurized trailer contains a modular radioisotope thermoelectric generator (RTG) supplying 6.5 kW continuous power. A secondary energy storage for short-term peak power needs is provided by a bank of lithium-sulfur dioxide batteries. The life support system is partly a regenerative system with air and hygiene water being recycled. A layer of water inside the composite shell surrounds the command center allowing the center to be used as a safe haven during solar flares. The PLR 1 has a total mass of 6197 kg. It has a top speed of 18 km/hr and is capable of towing three metric tons, in addition to the RTG trailer. The PLR 2 configuration consists of two four-meter diameter, cylindrical hulls which are passively connected by a flexible passageway, resulting in the overall vehicle length of 11 m. The vehicle is driven by eight independently suspended wheels. The dual-cylinder concept allows articulated as well as double Ackermann steering. The primary power of 8 kW is supplied by a dynamic isotope system using a closed Brayton cycle with a xenon-hydrogen mixture as the working fluid. A sodium-sulfur battery serves as the secondary power source. Excess heat produced by the primary power system and other rover systems is rejected by radiators located on the top of the rear cylinder. The total mass of the PLR 2 is 7015 kg. Simplicity and low total weight have been the driving principles behind the design of PLR 1. The overall configuration consists of a 7-m-long, 3-m-diameter cylindrical main vehicle and a two-wheeled trailer. The cylinder of the main body is capped by eight-section, faceted, semi-hemispherical ends. The trailer contains the RTG power source and is not pressurized. The shell of the main body is constructed of a layered carbon fiber/foam/Kevlar sandwich structure. Included in the shell is a layer of water for radiation protection. The layer of water extends from the front of the rover over the crew compartment and creates a safe haven for the crew during a solar flare-up. The carbon fiber provides the majority of the strength and stiffness and the Kevlar provides protection from micrometeoroids. The Kevlar is covered with a gold foil and multi-layer insulation (MLI) to reduce radiation degradation and heat transfer through the wall. A thin thermoplastic layer seals the fiber and provides additional strength.

Creel, Kenneth↗
NASA NTRS2000

Model-Based Testability Assessment and Directed Troubleshooting of Shuttle Wiring Systems

We have recently completed a pilot study on the Space shuttle wiring system commissioned by the Wiring Integrity Research (WIRe) team at NASA Ames Research Center, As the space shuttle ages, it is experiencing wiring degradation problems including arcing, chaffing insulation breakdown and broken conductors. A systematic and comprehensive test process is required to thoroughly test and quality assure (QA) the wiring systems. The NASA WIRe team recognized the value of a formal model based analysis for risk-assessment and fault coverage analysis. However. wiring systems are complex and involve over 50,000 wire segments. Therefore, NASA commissioned this pilot study with Qualtech Systems. Inc. (QSI) to explore means of automatically extracting high fidelity multi-signal models from wiring information database for use with QSI's Testability Engineering and Maintenance System (TEAMS) tool.

Deb, Somnath↗
NASA NTRS1994

Outgassing of solid material into vacuum thermal insulation spaces

Many cryogenic storage tanks use vacuum between inner and outer tank for thermal insulation. These cryogenic tanks also use a radiation shield barrier in the vacuum space to prevent radiation heat transfer. This shield is usually constructed by using multiple wraps of aluminized mylar and glass paper as inserts. For obtaining maximum thermal performance, a good vacuum level must be maintained with the insulation system. It has been found that over a period of time solid insulation materials will vaporize into the vacuum space and the vacuum will degrade. In order to determine the degradation of vacuum, the rate of outgassing of the insulation materials must be determined. Outgassing rate of several insulation materials obtained from literature search were listed in tabular form.

Wang, Pao-Lien↗
NASA NTRS2006

Aerogels for Thermal Insulation of Thermoelectric Devices

Silica aerogels have been shown to be attractive for use as thermal-insulation materials for thermoelectric devices. It is desirable to thermally insulate the legs of thermoelectric devices to suppress lateral heat leaks that degrade thermal efficiency. Aerogels offer not only high thermal- insulation effectiveness, but also a combination of other properties that are especially advantageous in thermoelectric- device applications. Aerogels are synthesized by means of sol-gel chemistry, which is ideal for casting insulation into place. As the scale of the devices to be insulated decreases, the castability from liquid solutions becomes increasingly advantageous: By virtue of castability, aerogel insulation can be made to encapsulate devices having any size from macroscopic down to nanoscopic and possibly having complex, three-dimensional shapes. Castable aerogels can permeate voids having characteristic dimensions as small as nanometers. Hence, practically all the void space surrounding the legs of thermoelectric devices could be filled with aerogel insulation, making the insulation highly effective. Because aerogels have the lowest densities of any known solid materials, they would add very little mass to the encapsulated devices. The thermal-conductivity values of aerogels are among the lowest reported for any material, even after taking account of the contributions of convection and radiation (in addition to true thermal conduction) to overall effective thermal conductivities. Even in ambient air, the contribution of convection to effective overall thermal conductivity of an aerogel is extremely low because of the highly tortuous nature of the flow paths through the porous aerogel structure. For applications that involve operating temperatures high enough to give rise to significant amounts of infrared radiation, opacifiers could be added to aerogels to reduce the radiative contributions to overall effective thermal conductivities. One example of an opacifier is carbon black, which absorbs infrared radiation. Another example of an opacifier is micron- sized metal flakes, which reflect infrared radiation. Encapsulation in cast aerogel insulation also can help prolong the operational lifetimes of thermoelectric devices that must operate in vacuum and that contain SiGe or such advanced skutterudite thermoelectric materials as CoSb3 and CeFe3.5Co0.5Sb12. The primary cause of deterioration of most thermoelectric materials is thermal decomposition or sublimation (e.g., sublimation of Sb from CoSb3) at typical high operating temperatures. Aerogel present near the surface of CoSb3 can impede the outward transport of Sb vapor by establishing a highly localized, equilibrium Sb vapor atmosphere at the surface of the CoSb3.

Sakamoto, Jeffrey↗
NASA NTRS2001

Overall Thermal Performance of Flexible Piping Under Simulated Bending Conditions

Flexible, vacuum-insulated transfer lines for low-temperature applications have higher thermal losses than comparable rigid lines. Typical flexible piping construction uses corrugated tubes, inner and outer, with a multilayer insulation (MLI) system in the annular space. Experiments on vacuum insulation systems in a flexible geometry were conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center. The effects of bending were simulated by causing the inner tube to be eccentric with the outer tube. The effects of spacers were simulated in a controlled way by inserting spacer tubes for the length of the cylindrical test articles. Two material systems, standard MLI and a layered composite insulation (LCI), were tested under the full range of vacuum levels using a liquid nitrogen boiloff calorimeter to determine the apparent thermal conductivity (k-value). The results indicate that the flexible piping under simulated bending conditions significantly degrades the thermal performance of the insulation system. These data are compared to standard MLI for both straight and flexible piping configurations. The definition of an overall k-value for actual field installations (k(sub oafi)) is described for use in design and analysis of cryogenic piping systems.

Fesmire, James E.↗
DOE OSTI2024

Material characterization of seven photovoltaic backsheets using seven accelerated test conditions

A variety of polymeric backsheet materials can be found in fielded photovoltaic (PV) modules, mostly based on fluoropolymer and polyethylene terephthalate (PET) materials. Cost reduction and sustainability considerations drive the recent development of alternative backsheet materials and designs [1]. In some fielded PV installations, polymeric materials are susceptible to environmental degradation in the form of backsheet cracking. To prevent backsheet degradation that can result in a module failure, thorough laboratory reliability testing is needed. In this report we studied the durability of seven commercial and experimental PV backsheets through accelerated stress testing using seven photolytic, hygrometric, and custom tests with the goal to understand if novel fluoropolymer-free backsheets are sufficiently environmentally durable to be commercialized. We divided the mechanisms observed during aging into two categories: core degradation and surface degradation. Although core degradation due to hydrolysis was observed in all commercial PET-, and polyamide (PA)-based backsheets aged with 85 degrees C/85% relative humidity, this test is unlikely to be field relevant. Photo-oxidative reactions on the exposed surface during UV weathering affected all seven backsheets regardless of the outer layer polymer material and additives. This degradation was limited to the outermost micrometers of the surface, except for backsheets containing PA-12, which resulted in surface cracking. A custom test combining UV with water spray caused the most severe backsheet degradation, including surface erosion and loss of insulating properties in polyolefin (PO)- and PA-based backsheets. This highlights the importance of combined accelerated stress testing to screen for complex backsheet degradation mechanisms. We also showed that, with material and design optimization, coextruded experimental PO-based backsheets have the potential to be a durable alternative to commercial PET- and fluoropolymer-based PV backsheets.

14 SOLAR ENERGY↗
NASA NTRS2024

Preliminary Measurements of Partial Discharge Inception Voltage Degradation with Constant Temperature Aging of Magnet Wire Twisted Pairs for Electric Aircraft Motors

Electric aircraft require high reliability electric motors to meet the stringent safety standards of the aviation industry. Motor winding insulation lifetime and reliability models for electric aircraft applications are needed to enable design of high reliability and high-performance electric motors for aviation applications. Three primary stresses effect the lifetime of motor winding insulation: thermochemical, mechanical, and electrical. This paper presents preliminary experiments on twisted pairs of magnet wire targeting understanding the thermo-chemical degradation of motor winding insulation through constant temperature thermal aging. Three types of magnet wire twisted pairs where tested: polyimide insulated magnet wire, epoxy coated polyimide insulated magnet wire, and epoxy potted polyimide magnet wire. The degradation of the samples over time at temperature was tracked using partial discharge inception voltage measurements. These initial experiments were used for development of procedures and expertise in partial discharge testing and thermo-chemical aging to inform future testing. The preliminary nature of these experiments should be noted when viewing the results. Lessons learned from the experiments are documented.

Thomas Tallerico↗
NASA NTRS2002

Thermal Performance of Cryogenic Piping Multilayer Insulation in Actual Field Installations

A standardized way of comparing the thermal performance of different pipelines in different sizes is needed. Vendor data for vacuum-insulated piping are typically given in heat leak rate per unit length (W/m) for a specific diameter pipeline. An overall k-value for actual field installations (k(sub oafi)) is therefore proposed as a more generalized measure for thermal performance comparison and design calculation. The k(sub oafi) provides a direct correspondence to the k-values reported for insulation materials and illustrates the large difference between ideal multilayer insulation (MLI) and actual MLI performance. In this experimental research study, a section of insulated piping was tested under cryogenic vacuum conditions, including simulated spacers and bending. Several different insulation systems were tested using a 1-meter-long cylindrical cryostat test apparatus. The simulated spacers tests showed significant degradation in the thermal performance of a given insulation system. An 18-meter-long pipeline test apparatus is now in operation at the Cryogenics Test Laboratory, NASA Kennedy Space Center, for conducting liquid nitrogen thermal performance tests.

Fesmire, J.↗
NASA NTRS1978

Thermal performance of gaseous-helium-purged tank-mounted multilayer insulation system during ground-hold and space-hold thermal cycling and exposure to water vapor

An experimental investigation was conducted to determine (1) the ground-hold and space-hold thermal performance of a multilayer insulation (MLI) system mounted on a spherical, liquid-hydrogen propellant tank and (2) the degradation to the space-hold thermal performance of the insulation system that resulted from both thermal cycling and exposure to moisture. The propellant tank had a diameter of 1.39 meters (4.57ft). The MLI consisted of two blankets of insulation; each blanket contained 15 double-aluminized Mylar radiation shields separated by double silk net spacers. Nineteen tests simulating basic cryogenic spacecraft thermal (environmental) conditions were conducted. These tests typically included initial helium purge, liquid-hydrogen fill and ground-hold, ascent, space-hold, and repressurization. No significant degradation of the space-hold thermal performance due to thermal cycling was noted.

Sumner, I. E.↗
NASA NTRS1999

Gas Sensor Evaluations in Polymer Combustion Product Atmospheres

Toxic gases produced by the combustion or thermo-oxidative degradation of materials such as wire insulation, foam, plastics, or electronic circuit boards in space shuttle or space station crew cabins may pose a significant hazard to the flight crew. Toxic gas sensors are routinely evaluated in pure gas standard mixtures, but the possible interferences from polymer combustion products are not routinely evaluated. The NASA White Sands Test Facility (WSTF) has developed a test system that provides atmospheres containing predetermined quantities of target gases combined with the coincidental combustion products of common spacecraft materials. The target gases are quantitated in real time by infrared (IR) spectroscopy and verified by grab samples. The sensor responses are recorded in real time and are compared to the IR and validation analyses. Target gases such as carbon monoxide, hydrogen cyanide, hydrogen chloride, and hydrogen fluoride can be generated by the combustion of poly(vinyl chloride), polyimide-fluoropolymer wire insulation, polyurethane foam, or electronic circuit board materials. The kinetics and product identifications for the combustion of the various materials were determined by thermogravimetric-IR spectroscopic studies. These data were then scaled to provide the required levels of target gases in the sensor evaluation system. Multisensor toxic gas monitors from two manufacturers were evaluated using this system. In general, the sensor responses satisfactorily tracked the real-time concentrations of toxic gases in a dynamic mixture. Interferences from a number of organic combustion products including acetaldehyde and bisphenol-A were minimal. Hydrogen bromide in the products of circuit board combustion registered as hydrogen chloride. The use of actual polymer combustion atmospheres for the evaluation of sensors can provide additional confidence in the reliability of the sensor response.

Delgado, Rafael H.↗
DOE OSTI2023

Status of Cable Aging Knowledge Gaps Identified in the Expanded Materials Degradation Assessment (EMDA)

This report summarizes research relevant to cable aging knowledge gaps identified in NUREG/CR-7153, “Expanded Materials Degradation Assessment (EMDA) Volume 5: Aging of Cables and Cable Systems” (EMDA Vol. 5), performed since the EMDA Vol. 5 was published in 2014. It begins with a discussion of the status of cables in long-term operation of U.S. nuclear power plants (NPPs) and the most common cables found in NPP containment. Next, the major polymer cable insulations, and the mechanisms of concern for degradation of those polymers in service are reviewed. A description of the environmental qualification (EQ) process historically used for safety-related cables is provided as is a review of the potential concerns with that process highlighted in the EMDA Vol. 5. Research addressing each of these is then reviewed. Finally, three potential strategies to support continued safe operation of aging cables are proposed: advanced condition-based verification, targeted material aging studies, and predictive simulation.

42 ENGINEERING↗