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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Vulnerability of Passive Microwave Snowfall Retrievals to Physical Properties of Snowpack: A Perspective from Dense Media Radiative Transfer Theory

The uncertainty of passive microwave retrievals of snowfall is notoriously high where the high-frequency surface emissivity is significantly reduced and varies markedly in response to changes of snowpack physical properties. Using the dense media radiative transfer theory, this article studies the potential effects of terrestrial snow-cover depth, density, and6grain size on high-frequency channels 89 and 166 GHz of the radiometer onboard the Global Precipitation Measurement (GPM) core satellite, which are commonly used to capture the snowfall scattering signals. Integrating the inference across all feasible grain sizes, ranges of snowpack density and depth are identified over which the snowfall scattering signatures can be time varying and potentially obscured. Using 10 years of reanalysis data, the seasonal vulnerability of snowfall retrievals to changes of snowpack emissivity in the Northern Hemisphere is mapped in a probabilistic sense and connections are made with uncertainties of the GPM passive microwave snowfall retrievals. It is found that among different snow classes, relatively light Arctic tundra snow in fall, with a density below 260kg m−3, and shallow prairie snow during the winter, with a depth of less than 40cm, can reduce the surface emissivity and obscure the snowfall passive microwave signatures. It is demonstrated that, during the winter, the highly vulnerable areas are over Kazakhstan, and Mongolia with taiga and prairie snow. In the fall, these areas are largely over tundra and taiga snow in north of Russia and the Arctic Archipelagos as well as prairies in Canada and the Great Plains in the United States.

Reyhaneh Rahimi↗
NASA NTRSDate not supplied

Active and Passive Storage Solutions for Low Temperature Lunar Sample Return

Active and passive thermal storage solutions to return lunar biological, physical science and/or geology samples to the Earth are under development. Temperature requirements for biological/physical science sample conditioning range from -100˚C to -153˚C and possibly down to -253˚C for geological samples. The lower limit for geological samples is derived from the temperature of permanently shadowed regions on the lunar surface and the sublimation temperature of specific volatiles of interest (i.e., H2O, NH3 and CH4). Individual samples for the lunar application are expected to be less than 50 kg with a 700 kg allowance for the container and refrigeration. Requiring no electrical power or heat rejection, passive approaches, comprised of high performance insulation and consumable Joule-Thompson cooling, may be preferred for shorter duration missions (< 30 days) to provide significant mass savings. Active storage approaches with cryogenic cooling may be necessary to preserve samples for longer periods of time. A notional passive storage concept with an internal vapor cooled shield is shown below. The vapor cooled shield contains the sample and is isolated from the outer container with concentric reflective rigid shields and conventional multi-layer and/or aerogel insulation on the outer layer. A special removable, insulating end cap to stow or retrieve the sample is included.

Lunar Sample Return↗
NASA NTRSDate not supplied

Spacecraft Passive Safety Assessment Using Ellipse Constraints and Relative Orbital Elements

This paper presents necessary and sufficient conditions for validating spacecraft passive safety using relative orbital elements (ROE) centered around the far-field to near-field trajectory design of a hypothetical autonomous rendezvous and docking (AR&D) mission. The specific formulation of the ROEs used in this study are of quasi-nonsingular form based on elative eccentricity/inclination vectors. Current methodologies for ensuring passive safety apply keep-out volumes (KOV) to maintain appropriate separation between the Servicer and Client. Widely used techniques to assess the integrity of the KOV involve forward propagation of the relative Cartesian state to check for a potential KOV breach. In this study, an alternative approach to the propagation-based method is proposed using ROEs due to their valuable geometric insights of spacecraft relative motion. Modeling the relative trajectory and KOV ellipsoids as ellipses into the 2-D ROE sub-space simplifies the passive safety validation to a root-finding problem within the unit disk with high computational efficiency. Other approaches to intersection detection of the KOV are also evaluated in accuracy and run-time. Furthermore, a Monte Carlo simulation was employed to compare the ROE-based and relative Cartesian approaches in terms of maneuver error.

Bruce Barbour↗
NASA NTRSDate not supplied

Environmental and Polarization Characterizations of E-Beam Plasma-Based AlF 3 -Passivated Aluminum Mirrors for Astronomical Telescopes

Astronomical space telescopes to study astrophysical phenomena from the far ultraviolet (FUV) to the near infrared (NIR) will require mirror coatings with high reflectance over this entire spectral region. While coatings for the optical and NIR part of the spectrum are fairly well developed with proven performance, the FUV range has presented significant challenges, particularly below 120nm. Recent developments in electron-beam (e-Beam) generated plasma treatment in a SF 6 environments has enabled the effective passivation of aluminum (Al) coatings for applications in the FUV, by native oxide removal and the formation of a AlF 3 passivation layer which could be tuned to any desired AlF 3 thickness. These results have been produced through a collaboration between the Goddard Space Flight Center (GSFC) and the Naval Research Laboratory (NRL). The passivation experiments have been carried out using the Large Area Plasma Processing System (LAPPS) at NRL using bare aluminum samples and provided by the coating group at GSFC. This novel procedure has demonstrated improved Al mirrors with state-of-the-art FUV reflectivity (e.g. R=91% at 121.6nm). In this paper, we will be reporting on environmental testing, micro-roughness, as well as polarization studies of these E-beam treated samples. These characterizations are being done in order to advance the Technology Readiness Level (TRL) for these Al+AlF 3 mirror coatings produced at LAPPS. The ultimate goal is to demonstrate the promise of using this coating technology to deliver reflectance performance plus stability and uniformity over a large area for a future IR/O/UV space telescope observatory.

FUV reflectance↗
NASA NTRSDate not supplied

Lunar Passive Fuel Cell Technologies: Evaporator + Fluid Polishing Elements

This project investigates key elements of a fully-passive, fuel-cell based, surface power generation concept. The overall concept replaces the actively pumped thermal management of a state of the art (SOA) fuel cell/electrolyzer stack with a passive 2-phase thermosyphon for heat transport and a passive shape memory actuating radiator for temperature management. The elements of the concept investigated in this project are: Evaporator Element: Evaluating the compatibility of common fuel-cell interconnect materials in the evaporator of a 2-phase water thermosyphon Fluid Polishing element: The use of membrane gas separation and resin water polishing to address non-condensable gas removal and water purity.

Fuel Cell↗
NASA NTRSDate not supplied

Comparison of Active and Passive Head Impulse Testing of the Horizontal Vestibulo-Ocular Reflex: Exploring the Feasibility of Different Approaches for Spaceflight

INTRODUCTION: Astronauts experience a wide variety of sensorimotor disturbances primarily due to microgravity-induced vestibular adaptations during spaceflight. Head Impulse Testing (HIT) will be conducted during the Complement of Integrated Protocols for Human Exploration Research program(CIPHER) Vestibular Health study to examine changes in the horizontal vestibulo-ocular reflex in response to high-velocity head movements to detect changes in peripheral vestibular function [1,2]. However, correct interpretation will require consideration of potential artifacts and the constraints of conducting this test across different phases of the mission. Therefore, the aims of our study were to (1) examine reliability across different test operators, and (2) compare results of active (aHIT) versus passive (pHIT) approaches to evaluate the feasibility of self-administered versus operator-assisted approaches. A comparison of responses with visual viewing of a wall target (default condition) versus vision occluded evaluated the influence of other oculomotor control influence across conditions, and comparison with computer-generated rotator head impulse tests (rHIT) examined the variability associated with the ocular responses independent of the variability in executing the head movements themselves. METHODS: Seventeen non-astronaut volunteers (male n=12, age=22.9 ± 3.0; female n=5, age=27.0 ± 6.0, mean ± std) completed HIT testing using video-oculography (VOG) goggles and a high-torque rotator system. The test order was counterbalanced across conditions: (1) passive head-on-torso (pHIT, default condition for flight study) using two operators (Op1 and Op2), (2) active head-on-torso (aHIT, subject initiated), and (3) passive head and torso using rotary chair (rHIT). Eye and head movement data were processed to obtain gain in each direction. The main outcome measures were average gain and asymmetry [1], as well as the percentage of acceptable trials not excluded due to insufficient head amplitude or recording artifacts. RESULTS: While the pHIT gains were similar with vision (1.032 ± 0.043) and vision occluded (1.029 ± 0.038) conditions, the percentage of acceptable trials was greater with vision (Op1 = 93.0%, Op2 = 93.2%) versus occluded (Op1 = 70.7%, Op2 = 67.6%). The reliability between operators was greater for pHIT gain (Intraclass Correlation, ICC = 0.66, p = 0.001) than for pHIT asymmetry (ICC = 0.57, p = 0.01). The percentage of acceptable trials reduced by ~20% during the self-administered aHITs for both visual conditions and tended to be lower than computer-generated rHITs (76% versus 83%). While the aHIT gains were not significantly different than pHIT gains for vision or vision occluded conditions, these measures were poorly correlated. Both aHIT and pHIT gains were significantly greater than the rHIT gains, presumably due to the reduced velocities from the rotator. The asymmetry measures were poorly correlated across pHIT, aHIT, and rHIT conditions, although none of the subjects had asymmetries greater than 16%. DISCUSSION: Our findings support the feasibility of using the standard pHIT methodology for spaceflight. Similarities between visual conditions reflect that these responses are mediated by the peripheral lateral canals rather than other oculomotor mechanisms. The inter-tester reliability was acceptable despite differences in the tester training. In addition to concerns of non-vestibular mechanisms introduced during self-administered aHITs [2], operator-assisted pHITs resulted in higher percentage of acceptable trials and should result in more efficient and reliable measures during spaceflight.

M R Ehrenburg↗
NASA NTRSDate not supplied

Passive fuel-Cell Surface power System (PaCeSS)

This effort produces a fully-passive surface power generation capability for fuel cell technology. The concept replaces the actively pumped thermal management of a state of the art (SOA) fuel cell/electrolyzer stack with a passive 2-phase thermosyphon for heat transport and a passive shape memory actuating radiator for temperature management.

Fuel Cell↗
NASA NTRSDate not supplied

Analysis of a Landing System for Planetary Payloads Utilizing Passive Energy Absorbing Composite Structure

Delivery of a payload from space to a planetary surface currently requires the development of an application specific landing system to protect the payload from forces imparted during impact with the planet surface. Often, active energy attenuating systems such as retro-rockets, deployable parachutes, and airbags are utilized within these landing systems to reduce landing impact energy. Unfortunately, these active systems come at a cost; active energy attenuating systems are susceptible to system faults which may limit or completely negate their energy attenuating capability. Additionally, components needing to be stowed such as fuel, parachutes, and airbags increase design complexity, cost, and weight. To overcome these limitations, this study examines the potential of passive energy attenuation through energy absorbing structural design and composite materials to mitigate landing loads for small payload planetary delivery. Researchers at the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) have conducted extensive research into developing energy absorbing structures and components for the attenuation of impact energy under various loading conditions including aircraft crash and spacecraft impact. The current study leverages this research to design a lightweight planetary delivery system which utilizes unique outer mold line (OML) geometry and passive energy absorbing structural design to limit landing loads across potential planetary surface environments. The OML geometry is designed to control impact orientation and provide self-righting capabilities for slopped impact surfaces. The internal structure is composed of composite material structures arranged to provide energy absorption which is robust to impact angle and impact velocity. The developed planetary delivery design concept will be evaluated using finite element (FE) model analysis. Simulations of landing impacts with representative soil surface environments will be used to characterize the energy absorbing capabilities of the landing system. Sensitivity of predicted impact force to landing environment, impact angle, and impact velocity will be assessed to identify capabilities and limitations of the initial structural design. Results will be used to determine the feasibility of a lightweight composite structure to passively absorb landing energy for robust planetary payload delivery.

Crashworthiness↗
NASA NTRSDate not supplied

Passive Fluid Transport in Microgravity Environments for the Stabilization of Rotating Spacecrafts

Rotating spacecraft offers the potential to create artificial gravity for extended space missions. However, designing a guidance and control system for such vehicles involves complex considerations. This paper examines a vehicle segmented into three parts, with the propulsion unit positioned at the vehicle’s center of mass. The vehicle must maintain stability around this central point, even under atypical conditions. Consequently, a durable and passive spin stabilization system is essential, requiring the passive transport of fluids. A combined system consisting of microcapillary bundles and hydraulic ram pumps is explored to transport fluids without any external energy added to the system. The dynamics of such a system are investigated, establishing performance and control limitations, and developing a control strategy predicated on the fluid dynamics between the segments. A model of the system is developed to validate the approach, showing that passive stabilization is possible, however, not as effective as an active stabilization system. Additionally, the model can be expanded for broader applications, including mass redistribution, a theoretical fluid ring, and three axis rotating systems.

Dynamics↗
NASA NTRSDate not supplied

Challenges in Remote-Sensing of Hail: Examining the Performance and Biases of Satellite Hail Retrievals Using Aqua MODIS Visible/IR and AMSR-E Passive-Microwave Observations

Hail poses threats to myriad aspects of human life and society, infrastructure, and agriculture. Scientifically, hail can often cause large errors in precipitation retrieval and estimation, posing challenges to establishing the current climatology of severe storms and their future trend in a changing Earth system. Fortunately, hailstorms exhibit distinct signatures in spaceborne remote-sensing datasets (e.g. overshooting cloud tops in visible/IR, or brightness temperature depressions in passive-microwave imagery). Approaches that leverage these signatures, however, are not without their pitfalls,: passive-microwave channels have large footprints and exhibit non-uniform beam filling. Visible/IR instruments have fine horizontal resolution but are limited by their insensitivity to processes occurring below cloud top. Large horizontal areas of smaller scatterers may also meaningfully lower the brightness temperatures, especially if they are able to occupy large portions of the footprint. Radiative transfer simulations show that low frequencies such as 19- and 37-GHz can be scattered to extremely low brightness temperatures by high concentrations of smaller (graupel-sized) ice scatterers, especially in larger features that are more likely to occupy the footprint, which may cause climatologies to overestimate the frequency severe hail. To address this, we investigate the nearly simultaneous and colocated MODIS (visible/IR) and AMSR-E (passive-microwave) onboard the Aqua satellite to leverage both datasets together, pairing AMSR-E and MODIS signatures of severe convection with ground-based weather radar, severe weather reports, and environmental parameters defined by the MERRA-2 reanalysis over CONUS, and then explore the performance and challenges of the algorithm when we expand outside the United States into six different geographical regimes throughout the Aqua domain.

Sarah D Bang↗
NASA NTRS2026

Assessing the Adhesion of Nanofibrous PVDF-HFP as Passive Thermal Control Coatings for the Extraterrestrial Storage of Cryogenic Propellants

Cryogenic propellant passive thermal management techniques in space are essential complements to active thermal management methods, helping reduce absolute dependence on the latter. Particularly, materials with superior optical properties (high solar reflectance and infrared emittance) would be beneficial for passive thermal control to reject most of the incident solar radiation and enhance thermal emission from the storage tank, leading to self-cooling. We developed a nanofibrous, porous passive thermal control material by electrospinning polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) co-polymer onto an aluminum foil substrate. The material exhibits a very high solar reflectance (>99%) and infrared emittance (~86%) when characterized in the ultraviolet-visible-near infrared and mid-infrared wavelengths. This study focuses on the adhesion of the nanofibrous PVDF-HFP to the substrate. We incorporated in-lab fabricated and commercial adhesives, under normal room conditions, between the nanofibers and the aluminum foil substrate to improve their adhesion. Some samples were also exposed to space-like conditions – vacuum and thermal cycling, to investigate their effects on the strengths of adhesives. Subsequently, adhesion peel tests were conducted on all the samples to assess the peel strengths of the bonds. Peel test strengths after space environment conditioning of the adhesives were generally higher than those observed in the pristine, unaged samples. The results are discussed in this study.

Chieloka Ibekwe↗
DOE OSTI2012

A Passive Tamper Indicating Enclosure For Use Within A Nuclear Weapons Monitoring Regime

AWE and PNNL are engaged in a technical collaboration investigating techniques to enhance continuity of knowledge over Treaty Accountable Items, with emphasis on a verified nuclear weapons dismantlement process. Tamper Indicating Enclosures (TIE) will likely be deployed as part of a chain of custody regime to indicate an unauthorised attempt to access a Treaty Accountable Item, or secure authenticated monitoring equipment. In 2011, the collaboration presented a paper at the INMM annual conference held in Palm Desert, CA titled “Passive Tamper Indicating Enclosures Incorporating Embedded Optical Fibre”, which discussed the concept of integrating optical fibres into TIEs for use as a passive tamper indicating mechanism. This paper provides an update on the Fibre Optic based TIE and introduces a second passive TIE concept based on the use of Poly(Methyl MethAcrylate) (PMMA). Concepts relating to deployment, tamper indication, and unique identification will be discussed.

Arms Control, tamper indicating enclosure, chain o↗
DOE OSTI2014

Ammonia Generation over TWC for Passive SCR NOX Control for Lean Gasoline Engines

A commercial three-way catalyst (TWC) was evaluated for ammonia (NH3) generation on a 2.0-liter BMW lean burn gasoline direct injection engine as a component in a passive ammonia selective catalytic reduction (SCR) system. The passive NH3 SCR system is a potential low cost approach for controlling nitrogen oxides (NOX) emissions from lean burn gasoline engines. In this system, NH3 is generated over a close-coupled TWC during periodic slightly rich engine operation and subsequently stored on an underfloor SCR catalyst. Upon switching to lean, NOX passes through the TWC and is reduced by the stored NH3 on the SCR catalyst. NH3 generation was evaluated at different air-fuel equivalence ratios at multiple engine speed and load conditions. Near complete conversion of NOX to NH3 was achieved at =0.96 for nearly all conditions studied. At the =0.96 condition, HC emissions were relatively minimal, but CO emissions were significant. Operation at AFRs richer than =0.96 did not provide more NH3 yield and led to higher HC and CO emissions. Results of the reductant conversion and consumption processes were used to calculate a representative fuel consumption of the engine operating with an ideal passive SCR system. The results show a 1-7% fuel economy benefit at various steady-state engine speed and load points relative to a stoichiometric engine operation.

Prikhodko, Vitaly Y↗
DOE OSTI2015

Passive absolute age and temperature history sensor

A passive sensor for historic age and temperature sensing, including a first member formed of a first material, the first material being either a metal or a semiconductor material and a second member formed of a second material, the second material being either a metal or a semiconductor material. A surface of the second member is in contact with a surface of the first member such that, over time, the second material of the second member diffuses into the first material of the first member. The rate of diffusion for the second material to diffuse into the first material depends on a temperature of the passive sensor. One of the electrical conductance, the electrical capacitance, the electrical inductance, the optical transmission, the optical reflectance, or the crystalline structure of the passive sensor depends on the amount of the second material that has diffused into the first member.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Designing Passivating, Carrier-Selective Contacts for Photovoltaic Devices

"The first step towards building a high-efficiency solar cell is to develop an absorber with few recombination-active defects. Many photovoltaic technologies have already achieved this (monocrystalline Si, III-V materials grown on lattice-matched substrates, perovskites, polycrystalline CdTe and CIGS); those that have not (a-Si:H, organics) have been limited to low open-circuit voltage. The second step is to develop contacts that both inhibit surface recombination and allow for low-resistance collection of either only electrons or only holes. For most photovoltaic technologies, this step is both more difficult and less explored than the first, and we are unaware of a prescribed methodology for selecting materials for contacts to solar cells. We elucidate a unified, conceptual understanding of contacts within which existing contacting schemes can be interpreted and future contacting schemes can be imagined. Whereas a split of the quasi-Fermi levels of holes and electrons is required in the absorber of any solar cell to generate a voltage, carriers are eventually collected through a metallic wire in which no such quasi-Fermi-level split exists. We define a contact to be all layers between the bulk of the absorber and the recombination-active interface through which carriers are extracted. The quasi-Fermi levels must necessarily collapse at this interface, and thus the transition between maximal quasi-Fermi-level splitting (in the absorber) and no splitting occurs entirely in the contact. Depending on the solar cell architecture, the contact will usually extend from the surface of the absorber to the surface of a metal or transparent conductive oxide layer, and may include deposited or diffused doped layers (e.g., as in crystalline and thin-film Si cells) and heterostructure buffer layers (e.g., the CdS layer in a CdTe device). We further define a passivating contact as one that enables high quasi-Fermi-level splitting in the absorber (large “internal” voltage), where “high” is relative to the splitting dictated by bulk recombination. Finally, we define a carrier-selective contact as one that enables a high “external” voltage measured across the contacts, where “high” is relative to the internal voltage. With these definitions, passivating contacts are those that allow only electrons, only holes, or neither electrons or holes to transport from the absorber to any position in the contact that has recombination-active defects. An excellent example of this is a SiNx layer on a Si wafer: the layer removes dangling bonds at the wafer surface (where there are both electrons and holes) and does not allow either carrier type to travel to its outermost surface, where there are undoubtedly defects. Carrier-selective contacts are then passivating contacts that also allow for low-impedance flow of either electrons or holes (but not both) to the recombination-active, extracting interface. The most common example is a heavily doped layer that establishes an electric field at the absorber surface, which then “filters” the carriers that may pass to the contact according to the sign of their charge.

14 SOLAR ENERGY↗
DOE OSTI2014

Passive Method to Characterize Atmospheric Turbulence

In remote sensing of materials using both passive and active illumination, atmospheric effects reduce the ability to make these measurements because they add spatial and spectral scintillation. While methods for compensating for turbulence effects exist for vertical paths (from space), reliable methods to compensate and/or measure turbulence for horizontal paths do not exist. The first step to compensation is a reliable measurement. We examined the mathematical basis for new methods to measure the strength of turbulence. We collected a large quantity of video imagery, which was used to confirm our new, passive method that characterizes the strength of the atmospheric turbulence. The results from this passive method are compared to scintillometer data. This work is ready to extend to atmospheric compensation.

Terry, Dr. David↗
DOE OSTI2017

Model predictive control of a lean-burn gasoline engine coupled with a passive selective catalytic reduction system

Lean-burn gasoline engines have demonstrated 10–20% engine efficiency gain over stoichiometric engines and are widely considered as a promising technology for meeting the 54.5 miles-per-gallon (mpg) Corporate Average Fuel Economy standard by 2025. Nevertheless, NOx emissions control for lean-burn gasoline for meeting the stringent EPA Tier 3 emission standards has been one of the main challenges towards the commercialization of highly-efficient lean-burn gasoline engines in the United States. Passive selective catalytic reduction (SCR) systems, which consist of a three-way catalyst and SCR, have demonstrated great potentials of effectively reducing NOx emissions for lean gasoline engines but may cause significant fuel penalty due to ammonia generation via rich engine combustion. The purpose of this study is to develop a model-predictive control (MPC) scheme for a lean-burn gasoline engine coupled with a passive SCR system to minimize the fuel penalty associated with passive SCR operation while satisfying stringent NOx and NH3 emissions requirements. Simulation results demonstrate that the MPC-based control can reduce the fuel penalty by 47.7% in a simulated US06 cycle and 32.0% in a simulated UDDS cycle, compared to the baseline control, while achieving over 96% deNOx efficiency and less than 15 ppm tailpipe ammonia slip. The proposed MPC control can potentially enable high engine efficiency gain for highly-efficient lean-burn gasoline engine while meeting the stringent EPA Tier 3 emission standards.

Chen, Pingen↗
DOE OSTI2018

Hydrogenation of passivated contacts

Methods of hydrogenation of passivated contacts using materials having hydrogen impurities are provided. An example method includes applying, to a passivated contact, a layer of a material, the material containing hydrogen impurities. The method further includes subsequently annealing the material and subsequently removing the material from the passivated contact.

36 MATERIALS SCIENCE↗