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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Aircraft microwave observations and simulations of deep convection from 18 to 183 GHz. II - Model results

In this June 29, 1986 case study, a radiative transfer model is used to simulate the aircraft multichannel microwave brightness temperatures presented in the Adler et al. (1990) paper and to study the convective storm structure. Ground-based radar data are used to derive hydrometeor profiles of the storm, based on which the microwave upwelling brightness temperatures are calculated. Various vertical hydrometeor phase profiles and the Marshall and Palmer (M-P, 1948) and Sekhon and Srivastava (S-S, 1970) ice particle size distributions are experimented in the model. The results are compared with the aircraft radiometric data. The comparison reveals that the M-P distribution well represents the ice particle size distribution, especially in the upper tropospheric portion of the cloud; the S-S distribution appears to better simulate the ice particle size at the lower portion of the cloud, which has a greater effect on the low-frequency microwave upwelling brightness temperatures; and that, in deep convective regions, significant supercooled liquid water (about 0.5 g/cu m) may be present up to the -30 C layer, while in less convective areas, frozen hydrometeors are predominant above -10 C level.

Yeh, Hwa-Young M.↗
NASA NTRSDate not supplied

Growth Curve Parameterization of Metabolic Activity of Yeast Cells for BioSentinel

The goal of the BioSentinel small satellite payload is to measure the effect of deep space radiation on the growth and metabolic activity of yeast cells. Raw test data is generated by fluidics cards containing yeast cells rehydrated at different periods, with metabolic activity measured by the reduction of alamarBlue. Each card well has a sensor array that measures the amount of red, green, and infrared light transmitted through the yeast culture. This illumination data is then converted to absorbance values, which are further converted into concentrations. The ultimate objective is to convert these concentrations into biologically-relevant metrics that can be compared against one another to determine changes due to differential radiation exposure. Beginning with IR absorbance data (corresponding to cell density) from ground studies, three parameters from a sigmoidal growth curve were extracted and analyzed: 𝜆 (lag phase), 𝜇 (max growth rate), and A (max cell growth). The data was fit to the Gompertz model of microbial growth using non-linear regression (Minitab), as the fit error was reduced compared to the simpler logistic growth curve. Graphs showed that the data contained a discrepancy (drift) in the lag phase that is attributable to a slow, constant loss of moisture. Correcting this discrepancy by fitting the first 25 hours of the data to a power function and subtracting these values from the absorbance readings obtained a better statistical fit to the growth curve in the lag phase. A power fit was selected over a linear fit because it reflected the effects of constant volume loss. This correction to the BioSentinel data analysis pipeline will enable quantitative statistical analysis of the effect of different levels of deep space radiation on yeast cells. Future work includes automation of drift correction and curve modeling to extract these parameters directly from data.

Growth Curve↗
NASA NTRS1999

Deep Space One High-Voltage Bus Management

The design of the High Voltage Power Converter Unit on DS1 allows both the spacecraft avionics and ion propulsion to operate in a stable manner near the PPP of the solar array. This approach relies on a fairly well-defined solar array model to determine the projected PPP. The solar array voltage set-points have to be updated every week to maintain operation near PPP. Stable operation even to the LEFT of the Peak Power Point is achievable so long as you do not change the operating power level of the ion engine. The next step for this technology is to investigate the use of onboard autonomy to determine the optimum SA voltage regulation set-point (i.e. near the PPP); this is for future missions that have one or more ion propulsion subsystems.

Rachocki, Ken↗
NASA NTRS2014

Adapting a Large-Scale Multi-Mission Ground System for Low-Cost CubeSats

The majority of today's CubeSat fleet consists of Earth-orbiting missions that mostly use existing ground systems developed by universities because of availability, simplicity, and low-cost. The Interplanetary NanoSpacecraft Pathfinder In Relevant Environment (INSPIRE) mission is a revolutionary CubeSat mission that will launch a pair of CubeSats into deep space to study the feasibility of CubeSats beyond low-Earth orbit. This uncovers a new set of systems and software engineering challenges to the development of a robust and reliable ground system in a low-cost environment. In this paper, we discuss the approach to these challenges by using the Jet Propulsion Laboratory's (JPL) Advanced Multimission Operation System (AMMOS) Ground Data System (GDS) as well as the methodologies used to engineer the flight system to work with an existing ground system developed for large-scale missions. Specifically we will focus on the command and telemetry subsystem of AMMOS, the Multimission Data Processing and Control System. We conclude with a retrospective on the challenges encountered and a brief discussion on our efforts to provide AMMOS to support future deep space CubeSat missions.

Quach, William L.↗
NASA NTRS1974

The use of COD and plastic instability in crack propagation and arrest in shells

The initiation, growth, and possible arrest of fracture in cylindrical shells containing initial defects are dealt with. For those defects which may be approximated by a part-through semi-elliptic surface crack which is sufficiently shallow so that part of the net ligament in the plane of the crack is still elastic, the existing flat plate solution is modified to take into account the shell curvature effect as well as the effect of the thickness and the small scale plastic deformations. The problem of large defects is then considered under the assumptions that the defect may be approximated by a relatively deep meridional part-through surface crack and the net ligament through the shell wall is fully yielded. The results given are based on an 8th order bending theory of shallow shells using a conventional plastic strip model to account for the plastic deformations around the crack border.

Erdogan, F.↗
NASA NTRS1978

Study of electronic properties in proton- and electron-irradiated GaAlAs and GaAs solar cell materials

Diagnostical measurement techniques such as dark I-V, C-V, the thermally insulated capacitance, and the deep level transient spectroscopy methods were employed to study defect properties in the proton-irradiated n-GaAs materials. Defect energy levels, thermal emission rates, and capture cross sections of electrons as well as trap densities were deduced from these measurements and the results are presented. Correlations between the measured defect parameters and the dark I-V characteristics of the n-GaAs Schottky barrier diodes are also discussed. Defect energy levels (i.e., electron traps) determined are also compared with published data in order to identify their physical origins.

Li, S. S.↗
NASA NTRS1977

Lunar regolith dynamics based on analysis of the cosmogenic radionuclides Na-22, Al-26, and Mn-53

Depth profiles of Na-22 and Al-26 in the upper portions of five lunar cores are analyzed. From the analyses, it is concluded that the natural gardening processes on the lunar surface result in mixing of the regolith to a depth of 2-3 cm over a time period which is short compared with the half-life of Al-26 (0.73 m.y.). It is also concluded that the rotary drill processes which were used to obtain the deep drill samples generally resulted in loss and/or mixing of the upper portions of the cores. In contrast, the near-surface regions of the drive tube cores appear to have a well-preserved stratigraphy. Analysis of Mn-53 in samples of six lunar rocks helps substantiate the accuracy of age date estimates by other means, and provides definite information that the total lunar surface exposure of two of these rocks has occurred during a single surface event which continued to their collection.

Fruchter, J. S.↗
NASA NTRS1988

X-band system performance of the very large array

The Very Large Array (VLA) is being equipped to receive telemetry from Voyager 2 during the Neptune encounter in 1989. Cryogenically cooled amplifiers are being installed on each of the 27 antennas. These amplifiers are currently a mix of field effect transistors (FETs) and high electron mobility transistors (HEMTs) and exhibit zenith system temperatures that range from 30 to 52 K. The system temperatures and aperture efficiencies determined during the past year are summarized. The nominal values of the noise diode calibration are compared with derived values made under the assumption of a uniform atmosphere over the array. Gain values are determined from observations of unresolved radio sources whose flux densities are well known. The tests suggest that the completed VLA will have a ratio of gain to system temperature that is approximately 4.4 dB above that of a single 64 m antenna of the Deep Space Network.

Ulvestad, J. S.↗
NASA NTRS1988

The ice band in IRAS 09371 + 1212

Spectra from 2 to 4 microns of the unusual IRAS source 09371 + 1212, a bipolar nebula, reveal a deep H2O ice absorption band near 3.1 microns. No long-wavelength wing is present, implying that the absorbing grain mantles are of high purity. The structure of the absorption feature is reasonably well modeled by a mixture of amorphous and crystalline H2O ice mantles on silicate grains, but discrepancies remain that could indicate other absorbers also.

Geballe, T. R.↗
NASA NTRS1992

Tektite origin by hypervelocity asteroidal or cometary impact: The quest for the source craters

Tektites are natural glasses that are chemically homogeneous, often spherically symmetrical objects several centimeters in size, and occur in four known strewn fields on the surface of the Earth: the North American, moldavite (or Central European), Ivory Coast, and Australasian strewn fields. Tektites found within such strewn fields are related to each other with respect to their petrological, physical, and chemical properties as well as their age. A theory of tektite origin needs to explain the similarity of tektites in respect to age and certain aspects of isotopic and chemical composition within one strewn field, as well as the variety of tektite materials present in each strewn field. In addition to tektites on land, microtektites (which are generally less than 1 mm in diameter) have been found in deep-sea cores. Tektites are classified into three groups: (1) normal or splash-form tektites, (2) aerodynamically shaped tektites, and (3) Muong Nong-type tektites (sometimes also called layered tektites). The aerodynamic ablation results from partial remelting of glass during atmospheric passage after it was ejected outside the terrestrial atmosphere and quenched from a hot liquid. Aerodynamically shaped tektites are known mainly from the Australasian strewn field where they occur as flanged-button australites. The shapes of splash-form tektites (spheres, droplets, teardrops, dumbbells, etc., or fragments thereof) are the result of the solidification of rotating liquids in the air or vacuum. Mainly due to chemical studies, it is now commonly accepted that tektites are the product of melting and quenching of terrestrial rocks during hypervelocity impact on the Earth. The chemistry of tektites is in many respects identical to the composition of upper crustal material.

Koeberl, Christian↗
NASA NTRS1992

Operational strategies for contamination control of composite materials

Composite materials, used on many instruments, are a potential contamination source for sensitive sensors, especially for sensors or detectors cooled below -80 C. It is a well known fact that composite materials absorb water during fabrication, integration, test, and launch activities and desorb this water under vacuum conditions. Water absorption can be divided into two types: shallow water and deep water. Shallow water is generally about 500 A thick on a clean material surface and is easily desorbed under vacuum conditions. Deep water is a function of the material and is absorbed into the bulk of the material. Deep water can outgas for weeks, months, or years, depending on the vent path, the amount of absorbed water, and the temperature of the material. Several operational strategies have been successfully employed on the Wide Field Planetary Camera. The operational strategies include ultradry gaseous nitrogen purge, dew point of less than -80 C, and vacuum bake-out with verification of outgassing rates. The nitrogen purge is instituted during the fabrication phase and is continued through launch activities. Great care is taken to avoid extended periods of time that the material is exposed to the ambient environment (50 percent relative humidity). On-orbit operational strategies include heat-up and cool-down scenarios which allow the deep water to be sufficiently outgassed before cooling the sensors or detectors.

Hansen, Patricia A.↗
NASA NTRS2009

The Deep Impact Network Experiment Operations Center

Delay/Disruption Tolerant Networking (DTN) promises solutions in solving space communications challenges arising from disconnections as orbiters lose line-of-sight with landers, long propagation delays over interplanetary links, and other phenomena. DTN has been identified as the basis for the future NASA space communications network backbone, and international standardization is progressing through both the Consultative Committee for Space Data Systems (CCSDS) and the Internet Engineering Task Force (IETF). JPL has developed an implementation of the DTN architecture, called the Interplanetary Overlay Network (ION). ION is specifically implemented for space use, including design for use in a real-time operating system environment and high processing efficiency. In order to raise the Technology Readiness Level of ION, the first deep space flight demonstration of DTN is underway, using the Deep Impact (DI) spacecraft. Called the Deep Impact Network (DINET), operations are planned for Fall 2008. An essential component of the DINET project is the Experiment Operations Center (EOC), which will generate and receive the test communications traffic as well as "out-of-DTN band" command and control of the DTN experiment, store DTN flight test information in a database, provide display systems for monitoring DTN operations status and statistics (e.g., bundle throughput), and support query and analyses of the data collected. This paper describes the DINET EOC and its value in the DTN flight experiment and potential for further DTN testing.

flight experiment↗
NASA NTRSDate not supplied

NASA Radiation Operations Sources, Models, and Standards

Space radiation is one of the major challenges of spaceflight. Astronauts spending time in low Earth orbit, the lunar surface, deep space, and elsewhere will all be exposed to multiple space radiation sources. These sources include trapped radiation in Earth’s upper atmosphere, solar energetic particles, and the omnipresent galactic cosmic radiation, as well as non-ionizing radiation from inside and outside a vehicle or habitat. The Space Radiation Analysis Group (SRAG) at Johnson Space Center is responsible for ensuring astronauts are protected from short- and long-term risks of radiation exposure. This talk details the radiation operational standards employed by NASA.

space radiation↗
NASA NTRS2003

Radiometric orbit determination activities in support of navigating Deep Space 1 to Comet Borrelly

After several months of planning, development and testing, new software was uploaded that allowed Deep Space 1 to restore celestial inertia reference and begin thrusting towards an encounter with comet Borrelly. The new mission plan would have to work within the constraints of the new software as well as minimize use of the dwindling supply of hydrazine, the fuel needed to maintain the spacecraft attitude.

DS1↗
NASA NTRS2002

Time resolved studies of proton irradiated quantum dots

The effects of proton irradiation on carrier dynamics were measured by time-resolved photoluminescence on InGaAs/GaAs quantum dot structures with different dot density and substrate orientation, as well as on InAlAs/AlGaAs quantum dots.

nanotechnology↗
NASA NTRS1974

A system of automated processing of deep water hydrological information

An automated system for primary and scientific analysis of deep water hydrological information is presented. Primary processing of the data in this system is carried out on a drifting station, which also calculates the parameters of vertical stability of the sea layers, as well as their depths and altitudes. Methods of processing the raw data are described.

Romantsov, V. A.↗
NASA NTRS1977

DSN tracking system: Mark III-77

The Deep Space Network tracking system is described. Revisions of subsystem Mark III-75 are briefly outlined, and the currently used multimission support subsystem Mark III-77 is described. Tracking functions performed are given as well.

Chaney, W. D.↗
NASA NTRS1980

Crystal growth of device quality GaAs in space

The apparatus and techniques used in effort to determine the relationships between crystal growth and electronic properties are described with emphasis on electroepitaxy and melt-grown gallium aresenide crystal. Applications of deep level transient spectroscopy, derivative photocapitance spectroscopy, and SEM-cathodoluminescene in characterizing wide bandgap semiconductors; determining photoionization in MOS, Schottky barriers, and p-n junctions; and for identifying inhomogeneities are examined, as well as the compensation of indium phosphide.

Gatos, H. C.↗