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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Haptic-Multimodal Flight Control System Update

The rapidly advancing capabilities of autonomous aircraft suggest a future where many of the responsibilities of today s pilot transition to the vehicle, transforming the pilot s job into something akin to driving a car or simply being a passenger. Notionally, this transition will reduce the specialized skills, training, and attention required of the human user while improving safety and performance. However, our experience with highly automated aircraft highlights many challenges to this transition including: lack of automation resilience; adverse human-automation interaction under stress; and the difficulty of developing certification standards and methods of compliance for complex systems performing critical functions traditionally performed by the pilot (e.g., sense and avoid vs. see and avoid). Recognizing these opportunities and realities, researchers at NASA Langley are developing a haptic-multimodal flight control (HFC) system concept that can serve as a bridge between today s state of the art aircraft that are highly automated but have little autonomy and can only be operated safely by highly trained experts (i.e., pilots) to a future in which non-experts (e.g., drivers) can safely and reliably use autonomous aircraft to perform a variety of missions. This paper reviews the motivation and theoretical basis of the HFC system, describes its current state of development, and presents results from two pilot-in-the-loop simulation studies. These preliminary studies suggest the HFC reshapes human-automation interaction in a way well-suited to revolutionary ease-of-use.

Goodrich, Kenneth H.↗
NASA NTRS2017

Deriving Global OH Abundance and Atmospheric Lifetimes for Long-Lived Gases: A Search for CH3CCl3 Alternatives

An accurate estimate of global hydroxyl radical (OH) abundance is important for projections of air quality, climate, and stratospheric ozone recovery. As the atmospheric mixing ratios of methyl chloroform (CH3CCl3) (MCF), the commonly used OH reference gas, approaches zero, it is important to find alternative approaches to infer atmospheric OH abundance and variability. The lack of global bottom-up emission inventories is the primary obstacle in choosing a MCF alternative. We illustrate that global emissions of long-lived trace gases can be inferred from their observed mixing ratio differences between the Northern Hemisphere (NH) and Southern Hemisphere (SH), given realistic estimates of their NH-SH exchange time, the emission partitioning between the two hemispheres, and the NH versus SH OH abundance ratio. Using the observed long-term trend and emissions derived from the measured hemispheric gradient, the combination of HFC-32 (CH2F2), HFC-134a (CH2FCF3, HFC-152a (CH3CHF2), and HCFC-22 (CHClF2), instead of a single gas, will be useful as a MCF alternative to infer global and hemispheric OH abundance and trace gas lifetimes. The primary assumption on which this multispecies approach relies is that the OH lifetimes can be estimated by scaling the thermal reaction rates of a reference gas at 272 K on global and hemispheric scales. Thus, the derived hemispheric and global OH estimates are forced to reconcile the observed trends and gradient for all four compounds simultaneously. However, currently, observations of these gases from the surface networks do not provide more accurate OH abundance estimate than that from MCF.

Lifetime↗
NASA NTRSDate not supplied

Predicting the Microgravity Performance of Terrestrial Portable Fire Extinguishers

Portable fire extinguishers (PFEs) are a key component of spacecraft emergency response systems. The International Space Station uses custom PFEs to meet the unique microgravity and enclosed space requirements of the vehicle. For future crewed missions to Low Earth Orbit and Deep Space destinations, terrestrial commercial off-the-shelf (COTS) PFEs may offer more economical solutions for the destination as well as the visiting vehicle. However, depending on the design of both the spacecraft and the PFE, the reduced gravity environment is likely to impact PFE performance, especially when multiphase microgravity liquid transport processes are present. Additionally, many terrestrial PFEs now use halocarbons as the suppressant. While studies show these are effective in certain terrestrial fires, some data suggest that low concentrations may actually exacerbate a fire, a phenomenon that would prove particularly concerning in spacecraft. To better characterize the potential of employing COTS hardware, two terrestrial PFEs, one charged with HFC-227ea and Nitrogen pressurant and one charged with carbon dioxide, were modeled to predict performance in both 1-g and microgravity environments. Testing was conducted in 1-g to validate the model. Testing was also conducted to evaluate the effect of sub-extinguishment HFC-227ea concentrations on burn rate in controlled samples. Here we provide a detailed description of the model, report the methods and results of PFE testing, discuss the predicted effects of microgravity on PFE performance, and report the results of material burn rates at sub-extinguishment levels of HFC-227ea.

Morgan B Abney↗
NASA NTRS2026

Improvement of Odor Control for the UWMS Hard-Sided Fecal Canister and the Alternate Fecal Canister

On longer range exploration missions, the mass and volume of critical hardware and consumables required to support crew will pose a big stowage challenge. This includes the hardware for the collection and storage of human metabolic solid waste. The amount of stowage needed for this hardware both before (empty) and after (full) use will be a significant burden on the overall spacecraft habitable volume, layout, and design. To help with this challenge, the National Aeronautics and Space Administration (NASA) Mars Campaign Office (MCO) Logistics Reduction (LR) Portfolio has developed a collapsible canister for the collection and containment of fecal deposits. The Alternate Fecal Canister (AFC) is a collapsible alternative to the exploration toilet Hard-sided Fecal Canister (HFC). The AFC in its empty state has a volumetric benefit to smaller vehicles on longer missions. The current designs for HFC and AFC were tested with human fecal material for odor containment at White Sands Test Facility (WSTF) where the tests on both were unsuccessful. The source of the lack of containment was isolated to a gasket used on both HFC and AFC. The gasket used was found to be open cell in design. This paper provides a summary of the materials selection and testing process to identify a replacement gasket material with the intention to replace the gaskets on both existing units as well as incorporate it into the designs going forward for future builds for exploration. Details will be provided on the design of the canisters interface with the odor bacteria lid which led to the selection of the thickness of the desired replacement. Finally, the paper will provide an update on the testing in advance of a return to WSTF for final testing and detail plans to complete testing and perform a demonstration on ISS with UWMS.

ECLSS↗
NASA NTRS2026

Improvement of Odor Control for the UWMS Hard-Sided Fecal Canister and the Alternate Fecal Canister

On longer range exploration missions, the mass and volume of critical hardware and consumables required to support crew will pose a big stowage challenge. This includes the hardware for the collection and storage of human metabolic solid waste. The amount of stowage needed for this hardware both before (empty) and after (full) use will be a significant burden on the overall spacecraft habitable volume, layout, and design. To help with this challenge, the National Aeronautics and Space Administration (NASA) Mars Campaign Office (MCO) Logistics Reduction (LR) Portfolio has developed a collapsible canister for the collection and containment of fecal deposits. The Alternate Fecal Canister (AFC) is a collapsible alternative to the exploration toilet Hard-sided Fecal Canister (HFC). The AFC in its empty state has a volumetric benefit to smaller vehicles on longer missions. The current designs for HFC and AFC were tested with human fecal material for odor containment at White Sands Test Facility (WSTF) where the tests on both were unsuccessful. The source of the lack of containment was isolated to a gasket used on both HFC and AFC. The gasket used was found to be open cell in design. This paper provides a summary of the materials selection and testing process to identify a replacement gasket material with the intention to replace the gaskets on both existing units as well as incorporate it into the designs going forward for future builds for exploration. Details will be provided on the design of the canisters interface with the odor bacteria lid which led to the selection of the thickness of the desired replacement. Finally, the paper will provide an update on the testing in advance of a return to WSTF for final testing and detail plans to complete testing and perform a demonstration on ISS with UWMS.

Toilet↗
DOE OSTI2021

Optimization of Refrigerant Compositions for Low-GWP Refrigerant Mixtures Using Segment-by-segment Heat Exchanger and Detailed System Models

The recently introduced hydrofluoroolefin (HFO) refrigerants, including R1234yf and R1234ze(E), have significantly lower global warming potentials (GWPs) than traditional hydrofluorocarbon (HFC) refrigerants like R410A. However, prior tests show that direct drop-in of pure R1234yf or R1234ze(E) into equipment designed for R410A results in a decrease in heat exchanger capacity and the system coefficient of performance. The primary reason is the lower in-tube heat transfer performance of R1234yf and R1234ze(E) compared with that of R410A. To address this issue, previous studies have mixed the mildly flammable HFC R32 with HFOs to improve system performance, with HFC R125 also added to suppress flammability. Previous studies selected compositions based on simple cycle analyses and did not consider modifications of the heat exchanger circuitry configuration to adapt to the new refrigerants. This study presents a novel multi-objective optimization approach to design a refrigerant composition that maximizes energy efficiency within flammability and GWP limits. The approach in this work simultaneously optimizes mixture composition and heat exchanger circuitry configuration. A case study on a rooftop unit indicates that, compared with mixture-only optimization, simultaneous optimization of mixture and heat exchanger circuitry yields a 5.9% improvement in cycle efficiency and a 48.6% reduction in refrigerant flammability with a GWP of 268. Circuitry optimization using refrigerants with different temperature glides shows that the larger the temperature glide is, the larger EER improvement is obtained. The results show that zeotropic blends with a large temperature glide are more sensitive to the refrigerant circuitry than pure refrigerants and may suffer significant performance degradation with subpar heat exchanger circuitry design. The proposed optimization approach is generally applicable to mixtures with any number of components. Using this approach to design a HVAC system can yield higher system efficiency within flammability and GWP constraints.

Li, Zhenning↗
DOE OSTI2021

Fabrication of Tantalum and Hafnium Carbide Fibers via Forcespinning TM for Ultrahigh‐Temperature Applications

In this work, a novel method for producing ultrafine tantalum and hafnium carbide fibers using the Forcespinning TM technique via a nonhalide‐based sol‐gel process was investigated. An optimal solution viscosity range was systematically determined via rheological studies of neat PAN/DMF as a function of fiber formation. Subsequently, Forcespinning TM parameters were also systemically studied to determine the optimal rotational velocity and spinneret‐to‐collecting rod distance required for ideal fiber formation. TaC and HfC fibers were synthesized via Forcespinning TM utilizing a mixture of PAN and refractory transition metal alkoxides (i.e., tantalum (V) ethoxide and hafnium (IV) tert‐butoxide) in DMF solution based on optimal conditions determined from the neat PAN/DMF. In all instances after calcination, powder X‐ray diffraction (PXRD) and energy dispersive spectroscopy (EDS) indicated that TaC and HfC fibers were produced. TGA/DSC confirmed the chemical stability of the resulting fibers.

Lee, Harold O.↗
DOE OSTI2022

Development of a Fuel Cell for the Perhydrodibenzyltoluene / Dibenzyltolluene Fuel Pair

An experimental study of the performance of an LFC with H-DBT and other cyclic hydrogenated aromatic fuels was carried out, along with a characterization of the fuel cell conversion products. A technoeconomic analysis (TEA) of the LFC operating in a class 8 truck powertrain using the H-DBT / DBT fuel pair was completed to determine the total cost of ownership (TCO), comparing LFC vehicles (LFCVs) to HFC vehicles (HFCVs), battery electric vehicles (BEVs), and diesel trucks on a pro-forma basis assuming the LFC could be developed to HFC benchmarks.

08 HYDROGEN↗
DOE OSTI2023

South Africa National Cooling Plan

South Africa is committed to preserving the environment and addressing climate change related issues based on science and equity. In 2019, South Africa ratified the Kigali Amendment to the Montreal Protocol to reduce the consumption and production of hydrofluorocarbons (HFCs) to simultaneously protect the ozone layer and contribute to mitigating climate change. In 2015, South Africa also signed the United Nations Framework Convention on Climate Change (UNFCCC) Paris Agreement to fight against climate change and committed to achieve a “peak, plateau and decline” greenhouse gas (GHG) trajectory at a level between 398 and 614 MtCO2e/year by 20301. In 2021 revised target ranges of 398-510 Mt CO 2 -eq for 2025, and 398-440 Mt CO 2 -eq for 2030 were issued, as well as aspiring to reach a net zero carbon economy by 2050. Addressing the environmental impacts of cooling products converges the objectives of these two treaties. Cooling products are the main source of HFC use and they consume a significant amount of electricity produced from emission intensive coal fired power plants. South Africa’s efforts to mitigate global warming can therefore be amplified if the energy efficiency (EE) of cooling products is improved at the same time a refrigerant transition from HFC is considered. Synergistic actions with respect to sustainable cooling access across sectors will have a higher impact than actions taken in isolation.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1973

Apollo 17 heat flow and convection experiments: Final data analyses results

A group of experiments called the Apollo 17 heat flow and convection (HFC) experiments was conducted, aboard the Apollo 17 spacecraft while in translunar coast on the way to the moon. These experiments together with the HFC experiments flown on Apollo 14 demonstrated and provided data on two types of low-g natural convection: cellular, surface tension-driven convection and convection in confined fluids caused by spacecraft and astronaut movements. Observed convection onset times show that surface tension-driven convection occurs at lower temperature gradients in low-g than in one-g environments. Data on heat flow in confined fluids show that spacecraft and astronaut movements can cause significant degrees of convection.

Bannister, T. C.↗
NASA NTRS1974

High-temperature mass spectrometry - Vaporization of group 4-B metal carbides

The high temperature vaporization of the metal-carbon systems TiC, ZrC, HfC, and ThC was studied by the Knudsen effusion - mass spectrometric method. For each system the metal dicarbide and tetracarbide molecular species were identified in the gas phase. Relative ion currents of the carbides and metals were measured as a function of temperature. Second- and third-law methods were used to determine enthalpies. Maximum values were established for the dissociation energies of the metal monocarbide molecules TiC, ZrC, HfC, and ThC. Thermodynamic functions used in the calculations are discussed in terms of assumed molecular structures and electronic contributions to the partition functions. The trends shown by the dissociation energies of the carbides of Group 4B are compared with those of neighboring groups and discussed in relation to the corresponding oxides and chemical bonding. The high temperature molecular beam inlet system and double focusing mass spectrometer are described.

Stearns, C. A.↗
NASA NTRS1986

Langley hypersonic facilities complex - Description and application

The Langley Hypersonic Facilities Complex (HFC) consists of hypersonic, blowdown wind tunnels developed and put into operation between the late 1950's and early 1970's. These facilities complement one another to presently provide ranges of Mach number from 6 to 22, unit Reynolds number from 0.1 to 15 million per foot, and normal shock density ratio from 4 to 12. Descriptions of these facilities are presented along with the testing techniques routinely used. Examples of the application of the HFC to generate data bases for proposed entry vehicles and for the verification of computer codes are given. Plans to upgrade the facilities to improve flow quality, productivity, capability and reliability are discussed.

Miller, C. G.↗
NASA NTRS1990

Degradation mechanisms of selected hydrochlorofluorocarbons in the atmosphere: An assessment of the current knowledge

Volatile organic compounds are mainly degraded in the troposphere by attack of OH with abstraction of H atoms or addition to unsaturated linkages. The chlorofluorocarbons (CFC's) do not contain these reactive sites and consequently cannot be degraded in this way in the lower atmosphere. This results in pollution of the stratosphere by these molecules and attendant problems for ozone. The proposed replacements for CFC's, the hydrochlorofluorocarbons (HCFC's), and hydrofluorocarbons (HFC's), contain at least one hydrogen atom in the molecule, which confers on these compounds a greater sensitivity toward oxidation by OH in the troposphere and in the lower stratosphere, resulting in much shorter atmospheric lifetimes than the CFC's. Consequently, the Ozone Depletion Potential and the Atmospheric Warming Potential are reduced substantially compared to the CFC's. All the possible degradation processes of the HCFC's and HFC's proposed to replace the CFC's are examined with the principal aim of identifying chlorine- and fluorine-containing products which are stable under tropospheric conditions.

Cox, Richard A.↗
NASA NTRS1990

An assessment of potential impact of alternative fluorocarbons on tropospheric ozone

While the chlorofuorocarbons (CFCs) such as CFC-11 (CFCl3) and CFC-12 (CF2Cl2) are chemically inert in the troposphere, the hydrogen-containing halocarbons being considered as their replacements can, to a large extent, be removed in the troposphere by the HO radical. These alternative halocarbons include the hydrochlorofluorocarbons (HCFCs) 123 (CF3CHCl2), 141b (CFCl2CH3), 142b (CF2ClCH3), 22 (CHF2Cl), and 124 (CF3CHFCl) and the hydrofluorocarbons (HCFs) 134a (CF3CH2F), 152a (CHF2CH3) and 125 (CF3CHF2). Listed are the rate constants (k) for the HO radical reaction of these compounds and their estimated chemical lifetimes in the troposphere. In this table, values of the lifetimes of these selected HCFCs and HCFs are seen to vary by more than a factor of more than ten ranging from 1.6 years for HFC 152a and HCFC 125 to as long as 28 years for HFC 125. Clearly, from the standpoint of avoiding or minimizing impact on stratospheric O3, those halocarbons with short tropospheric lifetimes are the desirable alternates. However, potential environmental consequences of their degradation in the troposphere should be assessed and taken into account in the selection process.

Niki, Hiromi↗
NASA NTRS1990

Toxicology of atmospheric degradation products of selected hydrochlorofluorocarbons

Trifluoroacetic acid (TFA) is a liquid with a sharp biting odor. It has been proposed as the product of environmental degradation of the hydrochlorofluorocarbons HCFC-123, HCFC-124, HFC-134a, and HFC-125. Compounds HCFC-141b and HCFC-142b could yield mixed fluorochloroacetic acids, for which there is no available toxicologic data. The release of hydrochlorofluorocarbons into the environment could also give rise to HF, but the additional fluoride burden (1 to 3 ppb) in rainwater is trivial compared to levels in fluoridated drinking water (1 ppm), and would provide an insignificant risk to humans. Thus, in this paper only the toxocologic data on TFA is reviewed to assess the potential risks of environmental exposure.

Kaminsky, Laurence S.↗
NASA NTRS1993

Rates of hydroxyl radical reactions with some HFCs

Relative rate constants for OH reactions with some HFCs have been determined at 298 K by a technique which measures the loss of HFC greater than OH. The following ratios were determine: k(152a)/k(CH4) = 5.2 +/- 0.5, k(CH4)/k(125) = 3.9 +/- 0.5, k(CH4)/k(134a) = 2.1 +/- 0.2, k(134a)/k(125) = 2.0 +/- 0.2, and k(C2H6)/k(152a) = 6.2 +/- 1.0. These results are in good agreement with literature values for the absolute rate constants except for HFC 134a, where a slower rate constant is indicated.

Demore, William B.↗
NASA NTRS1993

Tensile and stress-rupture behavior of hafnium carbide dispersed molybdenum and tungsten base alloy wires

The tensile strain rate sensitivity and the stress-rupture strength of Mo-base and W-base alloy wires, 380 microns in diameter, were determined over the temperature range from 1200 K to 1600 K. Three molybdenum alloy wires; Mo + 1.1w/o hafnium carbide (MoHfC), Mo + 25w/o W + 1.1w/o hafnium carbide (MoHfC+25W) and Mo + 45w/o W + 1.1w/o hafnium carbide (MoHfC+45W), and a W + 0.4w/o hafnium carbide (WHfC) tungsten alloy wire were evaluated. The tensile strength of all wires studied was found to have a positive strain rate sensitivity. The strain rate dependency increased with increasing temperature and is associated with grain broadening of the initial fibrous structures. The hafnium carbide dispersed W-base and Mo-base alloys have superior tensile and stress-rupture properties than those without HfC. On a density compensated basis the MoHfC wires exhibit superior tensile and stress-rupture strengths to the WHfC wires up to approximately 1400 K. Addition of tungsten in the Mo-alloy wires was found to increase the long-term stress rupture strength at temperatures above 1400 K. Theoretical calculations indicate that the strength and ductility advantage of the HfC dispersed alloy wires is due to the resistance to recrystallization imparted by the dispersoid.

Yun, Hee Mann↗
NASA NTRS1994

High Performance Arcjet Engines

This effort sought to exploit advanced single crystal tungsten-tantalum alloy material for fabrication of a high strength, high temperature arcjet anode. The use of this material is expected to result in improved strength, temperature resistance, and lifetime compared to state of the art polycrystalline alloys. In addition, the use of high electrical and thermal conductivity carbon-carbon composites was considered, and is believed to be a feasible approach. Highly conductive carbon-carbon composite anode capability represents enabling technology for rotating-arc designs derived from the Russian Scientific Research Institute of Thermal Processes (NIITP) because of high heat fluxes at the anode surface. However, for US designs the anode heat flux is much smaller, and thus the benefits are not as great as in the case of NIITP-derived designs. Still, it does appear that the tensile properties of carbon-carbon can be even better than those of single crystal tungsten alloys, especially when nearly-single-crystal fibers such as vapor grown carbon fiber (VGCF) are used. Composites fabricated from such materials must be coated with a refractory carbide coating in order to ensure compatibility with high temperature hydrogen. Fabrication of tungsten alloy single crystals in the sizes required for fabrication of an arcjet anode has been shown to be feasible. Test data indicate that the material can be expected to be at least the equal of W-Re-HfC polycrystalline alloy in terms of its tensile properties, and possibly superior. We are also informed by our colleagues at Scientific Production Association Luch (NP0 Luch) that it is possible to use Russian technology to fabricate polycrystalline W-Re-HfC or other high strength alloys if desired. This is important because existing engines must rely on previously accumulated stocks of these materials, and a fabrication capability for future requirements is not assured.

Kennel, Elliot B.↗