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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 NTRS1995

A high-speed photonic clock and carrier regenerator

As data communications rates climb toward 10 Gbits/s, clock recovery and synchronization become more difficult, if not impossible, using conventional electronic circuits. The high-speed photonic clock regenerator described in this article may be more suitable for such use. This photonic regenerator is based on a previously reported photonic oscillator capable of fast acquisition and synchronization. With both electrical and optical clock inputs and outputs, the device is easily interfaced with fiber-optic systems. The recovered electrical clock can be used locally and the optical clock can be used anywhere within a several kilometer radius of the clock/carrier regenerator.

Yao, X. S.↗
NASA NTRS2000

Regenerable Air Purification System for Gas-Phase Contaminant Control

Tests of a pre-prototype regenerable air purification system (RAPS) that uses water vapor to displace adsorbed contaminants from an adsorbent column have been performed at NASA Ames Research Center. A unit based on this design can be used for removing trace gas-phase contaminants from spacecraft cabin air or from polluted process streams including incinerator exhaust. During the normal operation mode, contaminants are removed from the air on the column. Regeneration of the column is performed on-line. During regeneration, contaminants are displaced and destroyed inside the closed oxidation loop. In this presentation we discuss initial experimental results for the performance of RAPS in the removal and treatment of several important spacecraft contaminant species from air.

Constantinescu, Ileana C.↗
NASA NTRS1995

Theoretical Analysis of a Pulse Tube Regenerator

A theoretical analysis of the behavior of a typical pulse tube regenerator has been carried out. Assuming simple sinusoidal oscillations, the static and oscillatory pressures, velocities and temperatures have been determined for a model that includes a compressible gas and imperfect thermal contact between the gas and the regenerator matrix. For realistic material parameters, the analysis reveals that the pressure and, velocity oscillations are largely independent of details of the thermal contact between the gas and the solid matrix. Only the temperature oscillations depend on this contact. Suggestions for optimizing the design of a regenerator are given.

Roach, Pat R.↗
NASA NTRS2002

Low Temperature Regenerators for Zero Boil-Off Liquid Hydrogen Pulse Tube Cryocoolers

Recently, a great deal of attention has been focused on zero boil-off (ZBO) propellant storage as a means of minimizing the launch mass required for long-term exploration missions. A key component of ZBO systems is the cooler. Pulse tube coolers offer the advantage of zero moving mass at the cold head, and recent advances in lightweight, high efficiency cooler technology have paved the way for reliable liquid oxygen (LOx) temperature coolers to be developed which are suitable for flight ZBO systems. Liquid hydrogen (LH2) systems, however, are another matter. For ZBO liquid hydrogen systems, cooling powers of 1-5 watts are required at 20 K. The final development from tier for these coolers is to achieve high efficiency and reliability at lower operating temperatures. Most of the life-limiting issues of flight Stirling and pulse tube coolers are associated with contamination, drive mechanisms, and drive electronics. These problems are well in hand in the present generation coolers. The remaining efficiency and reliability issues reside with the low temperature regenerators. This paper will discuss advances to be made in regenerators for pulse tube LH2 ZBO coolers, present some historical background, and discuss recent progress in regenerator technology development using alloys of erbium.

Salerno, Louis J.↗
NASA NTRS2003

Neuroprotection trek--the next generation: neuromodulation II. Applications--epilepsy, nerve regeneration, neurotrophins

Three examples of neuroprotective applications of electrical stimulation-neuromodulation-are considered: (1) the diagnosis and treatment of epilepsy, (2) the augmentation of peripheral nerve regeneration after transection, and (3) the interaction between electrical stimulation and neurotrophins (notably brain derived neurotrophic factor [BDNF]) in various neuroprotective situations. The research cited demonstrates clear benefit from appropriate electrical stimulation in the treatment of (1) certain patients with medication-refractory epilepsy, and (2) the functional regeneration of peripheral nerves after transection and surgical repair. Furthermore, neuromodulation of peripheral nerve regeneration has been associated with an increase in the neurotrophin BDNF. The roles of BDNF and other neurotrophins in several disorders of the nervous system are discussed in the context of neuromodulation and its augmentation of neurotrophins. Neuromodulation-at least in part through its effect on BDNF and other neurotrophins-will likely play a major role in the treatment (and possibly prevention) of disorders of the nervous system for which neuroproteive pharmacologic agents have traditionally been sought.

Review↗
NASA NTRS2004

Overview 2003 of NASA Multi-D Stirling Convertor Development and DOE and NASA Stirling Regenerator R and D Efforts

This paper will report on (1) continuation through the 3rd year of a NASA grant for multi-dimensional Stirling CFD code development and validation, (2) continuation through the 3rd and final year of a Department of Energy, Golden Field Office (DOE) regenerator research effort. Results of the NASA multi-D code development effort and the DOE regenerator research efforts will be summarized. Early results and planning for the new regenerator microfabrication contract will also be discussed.

Twe, Roy↗
NASA NTRS2010

A Mass Computation Model for Lightweight Brayton Cycle Regenerator Heat Exchangers

Based on a theoretical analysis of convective heat transfer across large internal surface areas, this paper discusses the design implications for generating lightweight gas-gas heat exchanger designs by packaging such areas into compact three-dimensional shapes. Allowances are made for hot and cold inlet and outlet headers for assembly of completed regenerator (or recuperator) heat exchanger units into closed cycle gas turbine flow ducting. Surface area and resulting volume and mass requirements are computed for a range of heat exchanger effectiveness values and internal heat transfer coefficients. Benefit cost curves show the effect of increasing heat exchanger effectiveness on Brayton cycle thermodynamic efficiency on the plus side, while also illustrating the cost in heat exchanger required surface area, volume, and mass requirements as effectiveness is increased. The equations derived for counterflow and crossflow configurations show that as effectiveness values approach unity, or 100 percent, the required surface area, and hence heat exchanger volume and mass tend toward infinity, since the implication is that heat is transferred at a zero temperature difference. To verify the dimensional accuracy of the regenerator mass computational procedure, calculation of a regenerator specific mass, that is, heat exchanger weight per unit working fluid mass flow, is performed in both English and SI units. Identical numerical values for the specific mass parameter, whether expressed in lb/(lb/sec) or kg/(kg/sec), show the dimensional consistency of overall results.

Juhasz, Albert J.↗
NASA NTRS2010

A Mass Computation Model for Lightweight Brayton Cycle Regenerator Heat Exchangers

Based on a theoretical analysis of convective heat transfer across large internal surface areas, this paper discusses the design implications for generating lightweight gas-gas heat exchanger designs by packaging such areas into compact three-dimensional shapes. Allowances are made for hot and cold inlet and outlet headers for assembly of completed regenerator (or recuperator) heat exchanger units into closed cycle gas turbine flow ducting. Surface area and resulting volume and mass requirements are computed for a range of heat exchanger effectiveness values and internal heat transfer coefficients. Benefit cost curves show the effect of increasing heat exchanger effectiveness on Brayton cycle thermodynamic efficiency on the plus side, while also illustrating the cost in heat exchanger required surface area, volume, and mass requirements as effectiveness is increased. The equations derived for counterflow and crossflow configurations show that as effectiveness values approach unity, or 100 percent, the required surface area, and hence heat exchanger volume and mass tend toward infinity, since the implication is that heat is transferred at a zero temperature difference. To verify the dimensional accuracy of the regenerator mass computational procedure, calculation of a regenerator specific mass, that is, heat exchanger weight per unit working fluid mass flow, is performed in both English and SI units. Identical numerical values for the specific mass parameter, whether expressed in lb/(lb/sec) or kg/ (kg/sec), show the dimensional consistency of overall results.

Juhasz, Albert J.↗
NASA NTRS2010

Microfabricated Segmented-Involute-Foil Regenerator for Stirling Engines

An involute-foil regenerator was designed, microfabricated, and tested in an oscillating-flow test rig. The concept consists of stacked involute-foil nickel disks (see figure) microfabricated via a lithographic process. Test results yielded a performance of about twice that of the 90-percent random-fiber currently used in small Stirling converters. The segmented nature of the involute- foil in both the axial and radial directions increases the strength of the structure relative to wrapped foils. In addition, relative to random-fiber regenerators, the involute-foil has a reduced pressure drop, and is expected to be less susceptible to the release of metal fragments into the working space, thus increasing reliability. The prototype nickel involute-foil regenerator was adequate for testing in an engine with a 650 C hot-end temperature. This is lower than that required by larger engines, and high-temperature alloys are not suited for the lithographic microfabrication approach.

Ibrahim, Mounir↗
NASA NTRS2003

Toxicological Assessment of the International Space Station Atmosphere with Emphasis on Metox Canister Regeneration

Space-faring crews must have safe breathing air throughout their missions to ensure adequate performance and good health. Toxicological assessment of air quality depends on the standards that define acceptable air quality, measurements of pollutant levels during the flight, and reports from the crew on their in-flight perceptions of air quality. Air samples returned from ISS on flights 8A, UF2, 9A, and 11A were analyzed for trace pollutants. On average, the air during this period of operations was safe for human respiration. However, about 3 hours into the regeneration of 2 Metox canisters in the U.S. airlock on 20 February 2002 the crew reported an intolerable odor that caused them to stop the regeneration, take refuge in the Russian segment, and scrub air in the U.S. segment for 30 hours. Analytical data from grab samples taken during the incident showed that the pollutants released were characteristic of nominal air pollutants, but were present in much higher concentrations. The odors reported by the crew were due to relatively high concentrations of n-butanol, and possibly other pollutants in the mixture. Later data taken during regeneration of Metox canisters that had not been subject to long-term flows showed minimal effects on air quality. Long-term trending data suggest that a disruption in atmospheric mixing between the Service Module and the U.S. Laboratory has occurred and that formaldehyde concentrations are gradually increasing in the U.S. Laboratory. Trending data also show that the releases of octafluoropropane (OFP) have subsided.

James, John T.↗
NASA NTRS2014

Carbon-Based Regenerable Sorbents for the Combined Carbon Dioxide and Ammonia Removal for the Primary Life Support System (PLSS)

Results are presented on the development of reversible sorbents for the combined carbon dioxide and trace-contaminant (TC) removal for use in Extravehicular Activities (EVAs). Since ammonia is the most important TC to be captured, data on TC sorption presented in this paper are limited to ammonia, with results relevant to other TCs to be reported at a later time. The currently available life support systems use separate units for carbon dioxide, trace contaminants, and moisture control, and the long-term objective is to replace the above three modules with a single one. Furthermore, the current TC-control technology involves the use of a packed bed of acid-impregnated granular charcoal, which is non-regenerable, and the carbon-based sorbent under development in this project can be regenerated by exposure to vacuum at room temperature. The objective of this study was to demonstrate the feasibility of using carbon sorbents for the reversible, concurrent sorption of carbon dioxide and ammonia. Several carbon sorbents were fabricated and tested, and multiple adsorption/vacuum-regeneration cycles were demonstrated at room temperature, and also a carbon surface conditioning technique that enhances the combined carbon dioxide and ammonia sorption without impairing sorbent regeneration.

Wojtowicz, Marek A.↗
NASA NTRS2016

Life Support Catalyst Regeneration Using Ionic Liquids and In Situ Resources

Oxygen recovery from metabolic carbon dioxide is an enabling capability for long-duration manned space flight. Complete recovery of oxygen (100%) involves the production of solid carbon. Catalytic approaches for this purpose, such as Bosch technology, have been limited in trade analyses due in part to the mass penalty for high catalyst resupply caused by carbon fouling of the iron or nickel catalyst. In an effort to mitigate this challenge, several technology approaches have been proposed. These approaches have included methods to prolong the life of the catalysts by increasing the total carbon mass loading per mass catalyst, methods for simplified catalyst introduction and removal to limit the resupply container mass, methods of using in situ resources, and methods to regenerate catalyst material. Research and development into these methods is ongoing, but only use of in situ resources and/or complete regeneration of catalyst material has the potential to entirely eliminate the need for resupply. The use of ionic liquids provides an opportunity to combine these methods in a technology approach designed to eliminate the need for resupply of oxygen recovery catalyst. Here we describe the results of an initial feasibility study using ionic liquids and in situ resources for life support catalyst regeneration, we discuss the key challenges with the approach, and we propose future efforts to advance the technology.

Abney, Morgan B.↗
NASA NTRS2016

Life Support Catalyst Regeneration Using Ionic Liquids and In Situ Resources

Oxygen recovery from metabolic carbon dioxide is an enabling capability for long-duration manned space flight. Complete recovery of oxygen (100%) involves the production of solid carbon. Catalytic approaches for this purpose, such as Bosch technology, have been limited in trade analyses due in part to the mass penalty for high catalyst resupply caused by carbon fouling of the iron or nickel catalyst. In an effort to mitigate this challenge, several technology approaches have been proposed. These approaches have included methods to prolong the life of the catalysts by increasing the total carbon mass loading per mass catalyst, methods for simplified catalyst introduction and removal to limit the resupply container mass, methods of using in situ resources, and methods to regenerate catalyst material. Research and development into these methods is ongoing, but only use of in situ resources and/or complete regeneration of catalyst material has the potential to entirely eliminate the need for resupply. The use of ionic liquids provides an opportunity to combine these methods in a technology approach designed to eliminate the need for resupply of oxygen recovery catalyst. Here we describe the results of an initial feasibility study using ionic liquids and in situ resources for life support catalyst regeneration, we discuss the key challenges with the approach, and we propose future efforts to advance the technology.

Abney, Morgan B.↗
DOE OSTI2025

Sorbent Regeneration via Radiofrequency-Assisted Dielectric Heating for Direct Air Capture of CO 2

Direct air capture (DAC) of CO 2 is a negative emission technology that utilizes sorbents requiring a regeneration step for repeated ab(/d)sorption–desorption cycles. Here we report an unconventional approach to desorb captured CO 2 from a porous sorbent using radiofrequency (RF) irradiation for dielectric heating and targeted energy transfer, thus enabling modularity and promoting renewable energy input. Regeneration of composites of functional ionic liquid and metal–organic framework with high CO 2 capacity and enhanced transport is demonstrated under conditions relevant to DAC. RF-assisted dielectric heating at the megahertz frequency range shows effective absorption of electromagnetic energy and consequently rapid release of the captured CO 2 .

Ionic liquids↗
DOE OSTI2024

The Role of Cu Species in the Regeneration of a Coked Cu/BEA Zeolite Catalyst

Active site occlusion by carbon species, often referred to as coke, is a common deactivation mechanism for heterogeneous catalysts. While it is known that transition metals can lower the temperature required for oxidative coke removal, the roles of ionic species and metal nanoparticles in coke removal are not well understood. This work aims to differentiate how ionic and nanoparticle Cu sites catalyze oxidative regeneration of a coked beta (BEA) zeolite catalyst. This was accomplished by synthesizing catalysts containing exclusively CuOx nanoparticles (NPs) or Cu2+ ions supported on BEA, physically mixing Cu/BEA with a coked BEA catalyst, and monitoring coke removal using in situ spectroscopy. Our results point to an improved combustion activity for CuOx NPs relative to Cu2+ ions, especially in the combustion of graphitic-type coke species. This improved understanding of coke combustion in transition metal containing catalysts informs strategies to improve catalyst regeneration, thereby increasing operational lifetimes.

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND AN↗
NASA NTRS2005

Genome-wide transcriptional analysis of flagellar regeneration in Chlamydomonas reinhardtii identifies orthologs of ciliary disease genes

The important role that cilia and flagella play in human disease creates an urgent need to identify genes involved in ciliary assembly and function. The strong and specific induction of flagellar-coding genes during flagellar regeneration in Chlamydomonas reinhardtii suggests that transcriptional profiling of such cells would reveal new flagella-related genes. We have conducted a genome-wide analysis of RNA transcript levels during flagellar regeneration in Chlamydomonas by using maskless photolithography method-produced DNA oligonucleotide microarrays with unique probe sequences for all exons of the 19,803 predicted genes. This analysis represents previously uncharacterized whole-genome transcriptional activity profiling study in this important model organism. Analysis of strongly induced genes reveals a large set of known flagellar components and also identifies a number of important disease-related proteins as being involved with cilia and flagella, including the zebrafish polycystic kidney genes Qilin, Reptin, and Pontin, as well as the testis-expressed tubby-like protein TULP2.

Polycystic Kidney Diseases/genetics↗
DOE OSTI2026

Protonated Tungsten Bronze (H x WO 3 ) Acts as an Easily Regenerable Reagent for PCET Reactions

In this study, protonated tungsten bronze powder (H x WO 3 ) was synthesized by a microwave heating technique from tungsten(VI) chloride in benzyl alcohol. This material facilitates a proton-coupled electron transfer (PCET) reaction with 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) in toluene, an aprotic solvent, to form TEMPOH, evidenced by UV–vis analysis of the organic product and X-ray photoelectron spectroscopy (XPS) analysis showing the oxidation of W 5+ to W 6+ in the remaining powder. Then, under illumination in an acidic aqueous solution, the oxidized WO 3 powder reacts photochromically to regenerate H x WO 3 . The regenerated H x WO 3 reagent remains active for further PCET reactions.

Granular materials↗
DOE OSTI2026

Chain entanglements enable regeneration of high-performance thermosets

Thermoset plastics underpin structural materials, electronics and transportation, yet the permanent covalent networks that prevent flow and provide dimensional stability also make them difficult to recycle without sacrificing performance. In this work we show that high-performance thermosets can be built around dense chain entanglements, the physical interlacing of long polymer strands, rather than dense permanent crosslinks, with only a small number of selectively cleavable junctions preserving connectivity. Long, rigid, entangled polyolefin backbones generated by frontal polymerization form glassy polymers with high stiffness, high toughness and excellent creep suppression yet can be fully deconstructed into soluble, linear oligomers. Varying oligomer length and end-group chemistry enables their reuse as re-entangling building blocks that regenerate thermosets with thermal and mechanical properties that remain unchanged across generations. The strategy further extends to high-temperature fibre-reinforced composite matrices and additively manufactured structures, establishing chain entanglement as a design principle for durable, regenerable thermosets.

36 MATERIALS SCIENCE↗