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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Optimization of a Wcl6 CVD System to Coat UO2 Powder with Tungsten

In order to achieve deep space exploration via Nuclear Thermal Propulsion (NTP), Marshall Space Flight Center (MSFC) is developing W-UO2 CERMET fuel elements, with focus on fabrication, testing, and process optimization. A risk of fuel loss is present due to the CTE mismatch between tungsten and UO2 in the W-60vol%UO2 fuel element, leading to high thermal stresses. This fuel loss can be reduced by coating the spherical UO2 particles with tungsten via H2/WCl6 reduction in a fluidized bed CVD system. Since the latest incarnation of the inverted reactor was completed, various minor modifications to the system design were completed, including an inverted frit sublimer. In order to optimize the parameters to achieve the desired tungsten coating thickness, a number of trials using surrogate HfO2 powder were performed. The furnace temperature was varied between 930 C and 1000degC, and the sublimer temperature was varied between 140 C and 200 C. Each trial lasted 73-82 minutes, with one lasting 205 minutes. A total of 13 trials were performed over the course of three months, two of which were re-coatings of previous trials. The powder samples were weighed before and after coating to roughly determine mass gain, and Scanning Electron Microscope (SEM) data was also obtained. Initial mass results indicated that the rate of layer deposition was lower than desired in all of the trials. SEM confirmed that while a uniform coating was obtained, the average coating thickness was 9.1% of the goal. The two re-coating trials did increase the thickness of the tungsten layer, but only to an average 14.3% of the goal. Therefore, the number of CVD runs required to fully coat one batch of material with the current configuration is not feasible for high production rates. Therefore, the system will be modified to operate with a negative pressure environment. This will allow for better gas mixing and more efficient heating of the substrate material, yielding greater tungsten coating per trial.

Belancik, Grace A.↗
NASA NTRS2017

Near Earth Asteroid Solar Sail Engineering Development Unit Test Program

The Near Earth Asteroid (NEA) Scout project is a 30x20x10cm (6U) cubesat reconnaissance mission to investigate a near Earth asteroid utilizing an 86m2 solar sail as the primary propulsion system. This will be the largest solar sail NASA will launch to date. NEA Scout is a secondary payload currently manifested on the maiden voyage of the Space Launch System in 2018. In development of the solar sail subsystem, design challenges were identified and investigated for packaging within a 6U form factor and deployment in cis-lunar space. Analysis furthered understanding of thermal, stress, and dynamics of the stowed system and matured an integrated sail membrane model for deployed flight dynamics. This paper will address design, fabrication, and lessons learned from the NEA Scout solar sail subsystem engineering development unit. From optical properties of the sail material to folding and spooling the single 86m2 sail, the team has developed a robust deployment system for the solar sail. This paper will also address expected and received test results from ascent vent, random vibration, and deployment tests.

Lockett, Tiffany Russell↗
NASA NTRS2016

Experimentally Observed Electrical Durability of 4H-SiC JFET ICs Operating from 500 C to 700 C

Prolonged 500 degrees Celsius to 700 degrees Celsius electrical testing data from 4H-SiC junction field effect transistor (JFET) integrated circuits (ICs) are combined with post-testing microscopic studies in order to gain more comprehensive understanding of the durability limits of the present version of NASA Glenn's extreme temperature microelectronics technology. The results of this study support the hypothesis that T ≥ 500 degrees Celsius durability-limiting IC failure initiates with thermal-stress-related crack formation where dielectric passivation layers overcoat micron-scale vertical features including patterned metal traces.

high temperature↗
NASA NTRS2017

Environmental Testbed Development to Evaluate Power Distribution Materials in Electrified Aircraft (EA)

NASA is pursuing the development of electrified propulsion (EP) technologies to improve air transportation in terms of efficiency, affordability, and sustainability. The power requirements are expected to reach 20 megawatts for large EP commercial airliners. A key challenge is transmission and distribution of the high voltage (20 kilovolts) needed for some EP systems. This is a challenge because the risk of electrical failure in aircraft at high altitude (low pressure) due to corona discharge and other forms of partial discharge increases significantly when voltages exceed 327 V. Corona discharge is a form of partial discharge in which gaseous molecules are ionized by strong electric fields. Corona discharge leads to aging in power transmission lines. Aging is a leading cause of electrical failure in electrical insulation materials. In particular, aging from electrical, vibrational, and thermal stresses decrease the performance life of insulation materials. There are currently no test standards or equipment that can effectively age materials under high altitude, voltage and frequency conditions. This poster proposes a design for a test system including an environmental chamber that can simulate the environment of future EP systems for material and component aging tests.

Materials Test chamber Design↗
NASA NTRS2019

Deviation of the Shape of Bennu from Rotational Figures of Stability

Images of asteroid (101955) Bennu acquired by the OSIRIS-­REx mission reveal a rocky world covered in rubble; Shape deviates from hydrostatic surface; Internal friction and/or cohesion even if no tensile strength; Understanding the deviation of the surface from idealized shape may help constrain mechanical properties of the interior; Geologic evolution of Bennu is driven by downslope migration of surface material and rubble; May be caused by YORP-induced spin-up, re-­accumulation, impact-induced seismic shaking, thermal stresses, or tidal disruption by close encounters to larger bodies.

Roberts, J. H.↗
NASA NTRS2019

Episodes of Particle Ejection from the Surface of the Active Asteroid (101955) Bennu

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

Lauretta, D. S.↗
NASA NTRSDate not supplied

Thermal Control in Hypersonic Leading Edges Using Liquid Metal High Temperature Oscillating Heat Pipes

The desire to increase the range and speed of hypersonic vehicles requires sharp, shape-stable Wing Leading Edges (WLE) with performance capabilities well beyond the current state of the art. The concentrated heat flux on sharp leading edges can lead to runaway thermal and mechanical failures. Heat pipes provide a passive solution to minimize the peak temperature, thermal gradients, and resulting thermal stresses near the WLE. Conventional heat pipes have been shown to address these issues at conditions as high as Mach 8. Oscillating heat pipes (OHPs) could be used to extend this benefit to missions with higher Mach numbers since their heat transport capacity typically exceeds that of conventional heat pipes. In the current investigation, several identical liquid metal high-temperature oscillating heat pipes (LMHOHPs) were constructed and tested to demonstrate the concept. The LMHOHPs had six turns, internal diameters of 2 mm, and total lengths of 100 mm. They were additively manufactured from C103 niobium alloy and charged with lithium to reach a fill ratio of approximately 50%. The boundary conditions of the experiment were designed to resemble those of various hypersonic flight profiles. Testing was performed with a system consisting of flow-controlled acetylene torch heating and radiation dominated heat rejection. The LMHOHP’s performance was measured using temperature data from an infrared camera and pyrometer. The experimental results were used to evaluate the capability of C103/lithium LMHOHPs under various flight regimes. A heat transfer model of the LMHOHP was proposed and validated against test data. Insights from the model were then extrapolated to evaluate a Tungsten-RHC/Gallium LMHOHP with anticipated capabilities beyond that of the C103/lithium system.

Max Pawlick↗
NASA NTRS2021

Coral Oxygen Isotopic Records Capture the 2015/2016 El Niño Event in the Central Equatorial Pacific

Coral oxygen isotopes (δ^(18)O) from the central equatorial Pacific provide monthly resolved records of El Niño-Southern Oscillation activity over past centuries to millennia. However, calibration studies using in situ data to assess the relative contributions of warming and freshening to coral δ^(18)O records are exceedingly rare. Furthermore, the fidelity of coral δ^(18)O records under the most severe thermal stress events is difficult to assess. Here, we present six coral δ^(18)O records and in situ temperature, salinity, and seawater δ^(18)O data from Kiritimati Island (2°N, 157°W) spanning the very strong 2015/16 El Niño event. Local sea surface temperature (SST) anomalies of +2.4 ± 0.4°C and seawater δ^(18)O anomalies of −0.19 ± 0.02‰ contribute to the observed coral δ^(18)O anomalies of −0.58 ± 0.05‰, consistent with a ∼70% contribution from SST and ∼30% from seawater δ^(18)O. Our results demonstrate that Kiritimati coral δ^(18)O records can provide reliable reconstructions even during the largest class of El Niño events.

Oxygen isotope anomalies↗
NASA NTRS2022

Silicon Photonic Transceiver for Spacecraft Navigational Lidar

NASA is developing an entry, descent, and landing (EDL) lidar system, the Navigation Doppler Lidar (NDL), for high-precision landing on the Moon, Mars, and beyond. The current flight NDL systems use 1550 nm fiber-optic components for frequency-modulated continuous wave (FMCW) ranging beyond 5 km, but have reduced performance under vibrational and thermal stresses during EDL. Here we describe recent efforts to develop a breadboard silicon photonic optical transceiver for integration into NDL to reduce instrument size and improve robustness to environment and demonstrate the optical balanced receiver performance during testing with the breadboard NDL unit. Initial testing shows improved suppression of common mode noise by 25 dB over the current receiver, but a 10 dB reduction in signal to noise ratio (SNR) resulting from coupling losses from fiber to the on-chip waveguides. Future work will target reduced coupling loss, hermetic packaging, and co-integration of a single sideband suppressed carrier modulator into the same chip.

Photonic Integrated Circuits↗
NASA NTRSDate not supplied

Critical Progressive Damage Analysis Model Features for Low-Velocity Impact on Thermoset and Thermoplastic Panels

A previous verification and validation framework evaluated the ability of various progressive damage analysis (PDA) tools to predict the mechanical response and damage state in post-buckled stiffened aerospace structures composed of fiber-reinforced thermoset composite materials. Herein, the ability of PDA tools to predict damage in thermoplastic composite materials subject to low-velocity impact (LVI) loading has been assessed. LVI tests and analyses have been conducted for similar panels, comprising thermoset or thermoplastic composite materials. Preliminary test/analysis correlations revealed that using the same combination of PDA model features and finite element model-building guidelines for the thermoset and thermoplastic LVI specimens resulted in underprediction of matrix crack lengths and delaminated area in the thermoplastic analyses despite yielding good correlations for the thermoset specimens. In this paper, the quality of the test/analysis correlations for analyses of thermoplastic LVI specimens performed with different combinations of PDA model features using the NASA CompDam material model are presented. Model features that were assessed in terms of effect on the quality of the test/analysis correlation include the representation of damageable interfaces, residual thermal stresses, and fiber damage.

Frank Leone↗
NASA NTRSDate not supplied

Critical Progressive Damage Analysis Model Features for Low-Velocity Impact on Thermoset and Thermoplastic Panels

A previous verification and validation framework evaluated the ability of various progressive damage analysis (PDA) tools to predict the mechanical response and damage state in post-buckled stiffened aerospace structures composed of fiber-reinforced thermoset composite materials. Herein, the ability of PDA tools to predict damage in thermoplastic composite materials subject to low-velocity impact (LVI) loading has been assessed. LVI tests and analyses have been conducted for similar panels, comprising thermoset or thermoplastic composite materials. Preliminary test/analysis correlations revealed that using the same combination of PDA model features and finite element model-building guidelines for the thermoset and thermoplastic LVI specimens resulted in underprediction of matrix crack lengths and delaminated area in the thermoplastic analyses despite yielding good correlations for the thermoset specimens. In this paper, the quality of the test/analysis correlations for analyses of thermoplastic LVI specimens performed with different combinations of PDA model features using the NASA CompDam material model are presented. Model features that were assessed in terms of effect on the quality of the test/analysis correlation include the representation of damageable interfaces, residual thermal stresses, and fiber damage.

Frank Leone↗
NASA NTRS2021

Missing the Reef for the Corals: Unexpected Trends Between Coral Reef Condition and the Environment at the Ecosystem Scale

It is incontrovertible that many coral reefs are in various stages of decline and may be unable to withstand the effects of global climate change, jeopardizing vital ecosystem goods and services to hundreds of millions of people around the world. An estimated 50% of the world's corals have already been lost, and those remaining may be lost by 2030 under the “business as usual” CO2 emissions scenario. However, the foundation of these predictions is a surprisingly sparse dataset, wherein ~0.01–0.1% of the world's reef area has been quantitatively surveyed. Further, the available data comprise observations at the 1–10 m scale, which are not evenly spaced across reefs, but often clustered in areas representing focused survey effort. This impedes modeling and predicting the impact of a changing environment at the ecosystem scale. Here we highlight deficiencies in our current understanding of the relationship between coral reefs and their environments. Specifically, we conduct a meta-analysis using estimates of coral cover from a variety of local surveys, quantitatively relating reef condition to a suite of biogeophysical forcing parameters. We find that readily available public data for coral cover exhibit unexpected trends (e.g., a positive correlation between coral cover and multi-year cumulative thermal stress), contrary to prevailing scientific expectations. We illustrate a significant gap in our current understanding, and thereby prediction, of coral reefs at the ecosystem scale that can only be remedied with uniform, high-density data across vast coral reef regions, such as that from remote sensing.

Eric J Hochberg↗
NASA NTRS2024

Transitional Flow in the Wake of a Pseudorandom Roughness on a Supersonic Flat Plate

Prediction of roughness-induced transition is a practical requirement for the optimized design of high-speed vehicles, which rely on a reduction of thermal stresses and drag for higher performance. This reduction is affected by boundary layer transition, which on real vehicles may be caused by unavoidable roughness such as inherent surface material roughness and deterioration or roughness in the form of sensing elements, fasteners, etc. A better understanding of transition resulting from roughness can help inform acceptable manufacturing tolerances or maintenance requirements on real vehicles.

Amanda Chou↗
DOE OSTI2014

Development of nanodiamond foils for H- stripping to Support the Spallation Neutron Source (SNS) using hot filament chemical vapor deposition

Thin diamond foils are needed in many particle accelerator experiments regarding nuclear and atomic physics, as well as in some interdisciplinary research. Particularly, nanodiamond texture is attractive for this purpose as it possesses a unique combination of diamond properties such as high thermal conductivity, mechanical strength and high radiation hardness; therefore, it is a potential material for energetic ion beam stripper foils. At the ORNL Spallation Neutron Source (SNS), the installed set of foils must be able to survive a nominal five-month operation period, without the need for unscheduled costly shutdowns and repairs. Thus, a small foil about the size of a postage stamp is critical to the operation of SNS and similar sources in U.S. laboratories and around the world. We are investigating nanocrystalline, polycrystalline and their admixture films fabricated using a hot filament chemical vapor deposition (HFCVD) system for H- stripping to support the SNS at Oak Ridge National Laboratory. Here we discuss optimization of process variables such as substrate temperature, process gas ratio of H2/Ar/CH4, substrate to filament distance, filament temperature, carburization conditions, and filament geometry to achieve high purity diamond foils on patterned silicon substrates with manageable intrinsic and thermal stresses so that they can be released as free standing foils without curling. An in situ laser reflectance interferometry tool (LRI) is used for monitoring the growth characteristics of the diamond thin film materials. The optimization process has yielded free standing foils with no pinholes. The sp3/sp2 bonds are controlled to optimize electrical resistivity to reduce the possibility of surface charging of the foils. The integrated LRI and HFCVD process provides real time information on the growth of films and can quickly illustrate growth features and control film thickness. The results are discussed in the light of development of nanodiamond foils that will be able to withstand a few MW proton beam and hopefully will be able to be used after possible future upgrades to the SNS to greater than a 3MW beam.

Vispute, R D↗
DOE OSTI2013

Expert Meeting Report: Cladding Attachment Over Exterior Insulation (BSC Report)

The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of both wood framed walls as well as mass masonry wall assemblies. The location of the insulation to the exterior of the structure has many direct benefits including better effective R-value from reduced thermal bridging, better condensation resistance, reduced thermal stress on the structure, as well as other commonly associated improvements such as increased air tightness and improved water management (Hutcheon 1964, Lstiburek 2007). The intent of the meeting was to review the current state of industry knowledge regarding cladding attachment over exterior insulation with a specific focus on: 1. Gravity load resistance, 2. Wind load resistance. The presentations explore these topics from an engineering design, laboratory testing, field monitoring, as well as practical construction perspective. By bringing various groups together (who have been conduction research or have experience in this area), a more holistic review of the design limits and current code language proposals can be completed and additional gaps identified. The results of which will help inform design standards and criteria.

Building America↗
DOE OSTI2017

Real-Time Measurement of Machine Efficiency during Inertia Friction Welding.

Process efficiency is a crucial parameter for inertia friction welding (IFW) that is largely unknown at the present time. A new method has been developed to determine the transient profile of the IFW process efficiency by comparing the workpiece torque used to heat and deform the joint region to the total torque. Particularly, the former is measured by a torque load cell attached to the non-rotating workpiece while the latter is calculated from the deceleration rate of flywheel rotation. The experimentally-measured process efficiency for IFW of AISI 1018 steel rods is validated independently by the upset length estimated from an analytical equation of heat balance and the flash profile calculated from a finite element based thermal stress model. The transient behaviors of torque and efficiency during IFW are discussed based on the energy loss to machine bearings and the bond formation at the joint interface.

42 ENGINEERING↗
DOE OSTI2018

Interwoven channels for internal cooling of airfoil

An apparatus and method for passing fluid flow through at least a portion of a blade of turbomachinery, such as a gas turbine or the like. The fluid flow is directed through a plurality of flow channels which are interwoven with each other. Each flow channel is non-intersecting with any other flow channel and thus does not contact fluid flowing within any other flow channel. The method and apparatus can be used to reduce heat transfer and thus reduce thermal stresses, particularly in the blade.

42 ENGINEERING↗
DOE OSTI2019

Numerical evaluation of thermal effects from nuclear waste disposed in horizontal drillholes

© 2019 American Nuclear Society, Inc. We examine the temperature evolution near horizontal drillholes designed for the disposal of spent nuclear fuel and high-level radioactive waste. In this concept, directional drilling technology is used to complete a small-diameter, vertical access hole, which at the target depth gradually turns into a horizontal section dedicated for the end-to-end disposal of nuclear waste canisters in a suitable, low-permeable formation. Decay heat emanating from the waste leads to temperature increases within the drillhole and the surrounding host rock. Predicting the thermal evolution within the engineered and natural barrier systems is important, because high temperatures may lead to thermal stresses, alter material properties, or induce driving forces that affect the migration of radionuclides along the drillhole and in the near field of the repository. We present the results of numerical design calculations that examine the spatial and temporal evolution of temperature as a function of uncertain material properties and adjustable design parameters.

Finsterle, S↗