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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 289 records · Page 16
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NASA NTRS2024

TOI-3568 b: A Super-Neptune in the Sub-Jovian Desert

The sub-Jovian desert is a region in the mass–period and radius–period parameter space that typically encompasses short-period ranges between super-Earths and hot Jupiters, and exhibits an intrinsic dearth of planets. This scarcity is likely shaped by photo evaporation caused by the stellar irradiation received by giant planets that have migrated inward. We report the detection and characterization ofTOI-3568 b, a transiting super-Neptune with a mass of26.4±1.0M⊕, a radius of5.30±0.27R⊕, a bulk density of0.98±0.15g cm−3, and an orbital period of 4.417965 (5) d situated in the vicinity of the sub-Jovian desert. This planet orbiting a K dwarf star with solar metallicity was identified photometrically by the Transiting Exoplanet Survey Satellite (TESS). It was characterized as a planet by our high-precision radial-velocity (RV) monitoring program using MAROON-X at Gemini North, supplemented with additional observations from the SPICE large program with SPIRou at CFHT. We performed a Bayesian MCMC joint analysis of the TESSand ground-based photometry, and MAROON-X and SPIRou RVs, to measure the orbit, radius, and mass of the planet, as well as a detailed analysis of the high-resolution flux and polarimetric spectra to determine the physical parameters and elemental abundances of the host star. Our results reveal TOI-3568 b to be a hot super-Neptune rich in hydrogen and helium, with a core of heavier elements of between 10 and 25 M⊕in mass. We analyzed the photo evaporation status of TOI-3568 b and find that it experiences one of the highest extreme-ultraviolet (EUV) luminosities among planets with a mass of Mp<2MNep, yet it has an evaporation lifetime exceeding 5 Gyr. Positioned in the transition between two significant populations of exoplanets on the mass–period and energy diagrams, this planet presents an opportunity to test theories concerning the origin of the sub-Jovian desert.

stars: individual: TOI-3568↗
NASA NTRS2026

Swamp Works Regolith Compaction Technologies

While the level of compaction below the lunar surface increases quickly after only a few cm of depth, in many cases during a construction mission there will be a need to excavate and transport regolith to a new location for cut-and-fill or horizontal construction of structures such as berms. In these cases to achieve high levels of bulk density, compaction must be per-formed. Additionally, in some cases surface technolo-gies such as systems that sinter/melt the surface may desire the maximum possible compaction at the sur-face to improve melting/heating performance and the final material strength properties. Kennedy Space Center’s (KSC) Swamp Works has developed two means of compaction, lunar and mar-tian compaction. Planetary Autonomous Compaction Technology (PACT) which is part of the Multifunction End Effector for Regolith Compaction Acquisition and Transfer (MEERCAT [1]) robotic arm end effector system’s capabilities and the Site Preparation Tooling for Operations on Mobility Platforms (STOMP [2]) vibratory roller compactor. PACT on MEERCAT has been demonstrated to a TRL 5 and STOMP to a TRL 4 in ambient testing. The results of PACT on MEERCAT and STOMP testing will be shared with results for various simulants including BP-1, ICN-LHT-1G (aka CSM-LHT-1G), RDW-LHT-1GH (a simulant developed for the Mason Tipping Point to match characteristics of ICN-LHT-1G), and Exolith LHS-1E. This will also include discus-sions on methods used to verify relative density before and after compaction and means to verify density effects below depth. To calculate relative density, maximum and minimum densities for simulants were taken from literature [3] [4] [5] and additional lab test-ing (publication in work).

vibration↗
NASA NTRSDate not supplied

Swamp Works Regolith Compaction Technologies

While the level of compaction below the lunar surface increases quickly after only a few cm of depth, in many cases during a construction mission there will be a need to excavate and transport regolith to a new location for cut-and-fill or horizontal construction of structures such as berms. In these cases to achieve high levels of bulk density, compaction must be per-formed. Additionally, in some cases surface technologies such as systems that sinter/melt the surface may desire the maximum possible compaction at the sur-face to improve melting/heating performance and the final material strength properties. Kennedy Space Center’s (KSC) Swamp Works has developed two means of compaction, lunar and mar-tian compaction. Planetary Autonomous Compaction Technology (PACT) which is part of the Multifunction End Effector for Regolith Compaction Acquisition and Transfer (MEERCAT) robotic arm end effector system’s capabilities and the Site Preparation Tooling for Operations on Mobility Platforms (STOMP) vibratory roller compactor. PACT on MEERCAT has been demonstrated to a TRL 5 and STOMP to a TRL 4 in ambient testing. The results of PACT on MEERCAT and STOMP testing will be shared with results for various simulants including BP-1, ICN-LHT-1G (aka CSM-LHT-1G), RDW-LHT-1GH (a simulant developed for the Mason Tipping Point to match characteristics of ICN-LHT-1G), and Exolith LHS-1E. This will also include discussions on methods used to verify relative density before and after compaction and means to verify density effects below depth. To calculate relative density, maximum and minimum densities for simulants were taken from literature and additional lab testing (publication in work).

redwire↗
NASA NTRS1972

Relationship of dislocation density of silicon to solar cell current loss at low temperature.

Large decreases in short circuit current of silicon solar cells have been reported to occur as temperature is decreased below -60 C. Experimental results are presented which relate high dislocation density of the silicon bulk material of cells to the large current loss effect. These results reveal a direct relationship between low bulk dislocation density and low current loss at low temperature. Oxygen content does not appear to play a significant role in the low temperature-large current loss effect, since some Czochralski cells did not suffer from this effect whereas some float-zone cells did. Other float-zone silicon cells had only medium current losses at low temperature despite their high bulk dislocation density. It appears that use of low-dislocation-density silicon can eliminate the current loss problem in low temperature cell operation.

Mandelkorn, J.↗
NASA NTRS2024

Enhancing Consistency of Microphysical Properties of Precipitation Across the Melting Layer in the Dual-Frequency Precipitation Radar Data

Stratiform rain and the overlying ice play crucial roles in Earth's climate system. From a microphysics standpoint, water mass flux primarily depends on two variables: particles' concentration and their mass. The Dual-frequency Precipitation Radar (DPR) on the Global Precipitation Measurement mission core satellite is a spaceborne instrument capable of estimating these two quantities through dual-wavelength measurements. In this study, we evaluate bulk statistics on the ice particle properties derived from dual-wavelength radar data in relation to the properties of rain underneath. Specifically, we focus on DPR observations over stratiform precipitation, characterized by columns exhibiting a prominent bright band, where the melting layer can be easily detected. Our analysis reveals a large increase in the retrieved mass flux as we transition from the ice to the rain phase in the official DPR product. This observation is in disagreement with our expectation that mass flux should remain relatively stable across the bright band in cold-rain conditions. To address these discrepancies, we propose an alternative retrieval algorithm that ensures a gradual transition of Dm (mean mass-weighted particle melted-equivalent diameter) and the precipitation rate across the melting zone. This approach also helps in estimating bulk ice density above the melting level. These findings demonstrate that DPR observations can not only quantify ice particle content and their size above stratiform rain regions but also estimate bulk density, provided uniform conditions that minimize uncertainties related to partial beam filling.

radar measurements from space↗
NASA NTRS2015

Spacecraft Charging Sensitivity to Material Properties

Evaluating spacecraft charging behavior of a vehicle in the space environment requires knowledge of the material properties relevant to the charging process. Implementing surface and internal charging models requires a user to specify a number of material electrical properties including electrical resistivity parameters (dark and radiation induced), dielectric constant, secondary electron yields, photoemission yields, and breakdown strength in order to correctly evaluate the electric discharge threat posed by the increasing electric fields generated by the accumulating charge density. In addition, bulk material mass density and/or chemical composition must be known in order to analyze radiation shielding properties when evaluating internal charging. We will first describe the physics of spacecraft charging and show how uncertainties in material properties propagate through spacecraft charging algorithms to impact the results obtained from charging models. We then provide examples using spacecraft charging codes to demonstrate their sensitivity to material properties. The goal of this presentation is to emphasize the importance in having good information on relevant material properties in order to best characterize on orbit charging threats.

Minow, Joseph I.↗
NASA NTRS1974

UCB current detector experiment on Swedish auroral payloads

A split Langmuir probe has been developed to make in situ measurements of ionospheric current density and plasma bulk flow. The probe consists of two conducting elements that are separated by a thin insulator that shield each other over a 2 pi solid angle, and that are simultaneously swept from negative to positive with respect to the plasma. By measuring the current to each plate and the difference current between plates, information is obtained on the plasma's current density, bulk flow, electron temperature, and density. The instrument was successfully flown twice on sounding rockets into auroral events. Measurement data indicate that the total auroral current configuration is composed of several alternating east and west electrojets associated with several alternating up and down Birkeland currents.

Mozer, F.↗
NASA NTRS1979

Full-scale engine tests of bulk absorber acoustic inlet treatment

Three different densities of Keviar bulk absorber fan inlet treatment were tested on a YF 102 turbofan engine. This bulk absorber material may have potential for flight application. Farfield noise measurements were made and the attenuation properties of the three treatment densities were compared. In addition, the best bulk treatment was compared to the best single degree of freedom, SDOF (honeycomb and perforated cover sheet) treatment from another investigation. Although the density was varied over a large range, (3 to 1) the effect on attenuation was small. The highest density treatment, 11.8 lb/cubic ft., had a somewhat broader attenuation bandwidth. The comparison of the best bulk and SDOF treatments showed the bulk to have a much greater attenuation bandwidth. At the design frequency both types of treatment had almost equal performance.

Heidelberg, L. J.↗
NASA NTRS1979

Full-scale engine tests of bulk absorber acoustic inlet treatment

Three different densities of Kevlar bulk absorber fan inlet treatment were tested on a YF 102 turbofan engine. This bulk absorber material may have potential for flight application. Far-field noise measurements were made and the attenuation properties of the three treatment densities were compared. In addition the best bulk treatment was compared to the best single degree of freedom, SDOF (honeycomb and perforated cover sheet) treatment from another investigation. Although the density was varied over a large range, (3 to 1) the effect on attenuation was small. The highest density treatment, 11.8 lb/cu ft, had a somewhat broader attenuation bandwidth. The comparison of the best bulk and SDOF treatments showed the bulk to have a greater attenuation bandwidth. At the design frequency both types of treatment had almost equal performance.

Heidelberg, L. J.↗
NASA NTRS1992

Method for determining transport critical current densities and flux penetration depth in bulk superconductors

A contact-less method for determining transport critical current density and flux penetration depth in bulk superconductor material. A compressor having a hollow interior and a plunger for selectively reducing the free space area for distribution of the magnetic flux therein are formed of superconductor material. Analytical relationships, based upon the critical state model, Maxwell's equations and geometrical relationships define transport critical current density and flux penetration depth in terms of the initial trapped magnetic flux density and the ratio between initial and final magnetic flux densities whereby data may be reliably determined by means of the simple test apparatus for evaluating the current density and flux penetration depth.

Israelsson, Ulf E.↗
NASA NTRS1975

The Pioneer 10 plasma analyzer results at Jupiter

Results are reported for the Pioneer 10 plasma-analyzer experiment at Jupiter. The analyzer system consisted of dual 90-deg quadrispherical electrostatic analyzers, multiple charged-particle detectors, and attendant electronics; it was capable of determining the incident plasma-distribution parameters over the energy range from 100 to 18,000 eV for protons and from approximately 1 to 500 eV for electrons. Data are presented on the interaction between the solar wind and the Jovian magnetosphere, the interplanetary ion flux, observations of the magnetosheath plasma, and traversals of the bow shock and magnetopause. Values are estimated for the proton isotropic temperature, number density, and bulk velocity within the magnetosheath flow field as well as for the beta parameter, ion number density, and magnetic-energy density of the magnetospheric plasma. It is argued that Jupiter has a reasonably thick magnetosphere somewhat similar to earth's except for the vastly different scale sizes involved.

Wolfe, J. H.↗
NASA NTRS2016

Foundational Methane Propulsion Related Technology Efforts, and Challenges for Applications to Human Exploration Beyond Earth Orbit

Current interest in human exploration beyond earth orbit is driving requirements for high performance, long duration space transportation capabilities. Continued advancement in photovoltaic power systems and investments in high performance electric propulsion promise to enable solar electric options for cargo delivery and pre-deployment of operational architecture elements. However, higher thrust options are required for human in-space transportation as well as planetary descent and ascent functions. While high thrust requirements for interplanetary transportation may be provided by chemical or nuclear thermal propulsion systems, planetary descent and ascent systems are limited to chemical solutions due to their higher thrust to weight and potential planetary protection concerns. Liquid hydrogen fueled systems provide high specific impulse, but pose challenges due to low propellant density and the thermal issues of long term propellant storage. Liquid methane fueled propulsion is a promising compromise with lower specific impulse, higher bulk propellant density and compatibility with proposed in-situ propellant production concepts. Additionally, some architecture studies have identified the potential for commonality between interplanetary and descent/ascent propulsion solutions using liquid methane (LCH4) and liquid oxygen (LOX) propellants. These commonalities may lead to reduced overall development costs and more affordable exploration architectures. With this increased interest, it is critical to understand the current state of LOX/LCH4 propulsion technology and the remaining challenges to its application to beyond earth orbit human exploration. This paper provides a survey of NASA's past and current methane propulsion related technology efforts, assesses the accomplishments to date, and examines the remaining risks associated with full scale development.

Brown, Thomas↗
NASA NTRS1993

Galileo observations of the motions of ion and electron plasmas in the magnetotail

A series of simultaneous determinations is presented of the 3D bulk flows of ion and electron plasmas in the magnetotail at radial distances near the lunar orbit. In the plasma mantle the ion and electron bulk velocities are identical within measurement accuracy. In the plasma sheet the electron bulk flows, densities, and temperatures are consistent with the results of the previous ISEE-3 survey at these radial distances as given by Zwickl et al. (1984). The present observations show that the electron bulk flows are often dominantly field-aligned and attributable to field-aligned currents, not convective motions within the magnetotail. The E x B convection of the plasmas as determined directly from the ion observation is often significantly slower and/or in a different direction than the bulk motions of either the ion or the electron plasmas. Thus, the ISEE-3 observations of electron bulk flows cannot be reliably used as measures of the E x B convection of plasmas or ion bulk motions at these distances in the plasma sheet.

Frank, L. A.↗
NASA NTRS1998

A Coupled Plasma Dynamics and Gas Flow Model for Semiconductor Processing

A continuum modeling approach by self-consistently coupling plasma dynamics and gas flow will be presented for the analysis of high density plasma reactors. Experimental data shows that gas flow distribution affects the etch rate uniformity even at low pressures (6-20 mTorr) and flow rates (20-70 sccm). This study will investigate the effects of gas flow and gas energy on bulk plasma densities and temperatures using a continuum model. The model solves multidimensional equations of mass balance for neutrals and ions, gas momentum, separate energy equations for electrons and neutrals and Maxwell's equations for power coupling. A test case of N2 plasma in a 300mm TCP etch reactor, for which hybrid model and Langmuir probe data are available, is chosen for this analysis. Our preliminary results show that modeling gas flow and energy improves the predictions of electron density and its spatial variation in the reactor when compared with the experimental data. The aim of this study is to identify the operating conditions for the TCP reactor when a self-consistent modeling of gas flow is important.

Bose, Deepak↗
NASA NTRS1972

A shock-induced phase change in iron-silicate garnet.

Hugoniot measurements on iron-silicate garnet demonstrate that above a shock pressure of about 205 kbar transition to a high-pressure phase(s), having an apparent zero-pressure density and bulk modulus of 4.44 g/cu cm and 3.3 Mbar, occurs. Crystal chemical systematics and Debye-Scherrer X-ray patterns of a recovered phase(s), which may be the shock-induced high-pressure form, suggest possible formation of a phase with a density of 4.48/cu cm. Occurrence of such a polymorph of garnet in the mantle would give rise to an increase in density and seismic velocity below 600 km in the earth.

Ahrens, T. J.↗
NASA NTRS1995

DE-1 observations of polar O(+) stream bulk parameters and comparison with a model of the centrifugally-accelerated polar wind

A survey of bulk parameters of analyzable O(+) outward streams in the mid-altitude (3-4.7 R(sub E) geocentric distance) polar cap magnetosphere is obtained from measurements by the Retarding Ion Mass Spectrometer (RIMS) aboard the Dynamics Explorer-1 (DE-1) spacecraft. There is wide scatter in the obtained densities, but they do display discernible trends: the average O(+) density in these streams decreases from about 60 ions/cc at 3.5 R(sub E) to about 1 ion/cc at 4.6 R(sub E). The streaming velocities are somewhat more defined, and their average increases from about 8 km/s at 3.5 R(sub E) to about 12 km/s at 4.6 R(sub E). The densities and bulk velocities are inversely correlated. We have further compared these observational trends with model profiles for the centrifugally-accelerated polar wind as recently described by Horwitz et al. (1994). The large outflow velocities observed can be understood in part as centrifugally-driven by convection with ionospheric electric field magnitudes of the order 50-70 mV/m, perhaps including plasma expansion effects.

Ho, C. Wing↗
NASA NTRS1991

Plasma observations at Venus with Galileo

Plasma measurements were obtained with the Galileo spacecraft during an approximately 3.5-hour interval in the vicinity of Venus on February 10, 1990. Several crossings of the bow shock in the local dawn sector were recorded before the spacecraft passed into the solar wind upstream from this planet. Solar wind densities and bulk speeds were determined from the electron velocity distributions. A magnetic field-aligned distribution of hotter electrons or 'strahl' was also found in the solar wind. Ions streaming into the solar wind from the bow shock were detected. Electron heating at the bow shock, about 20 percent, was notably small, with substantial density increases by factors of 2 to 3 at the day side of the shock that decrease for shock crossings further downstream from the planet. A search for pickup ions from the hot hydrogen and oxygen planetary coronas yielded an upper limit for these densities in the range of 0.001 ion/cu cm, which is consistent with densities expected from current models of neutral gas densities.

Frank, L. A.↗