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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Applications of tunable high energy/pressure pulsed lasers to atmospheric transmission and remote sensing

Atmospheric transmission of high energy C12 O2(16) lasers were improved by pulsed high pressure operation which, due to pressure broadening of laser lines, permits tuning the laser 'off' atmospheric C12 O2(16) absorption lines. Pronounced improvement is shown for horizontal transmission at altitudes above several kilometers, and for vertical transmission through the entire atmosphere. The atmospheric transmission of tuned C12 O2(16) lasers compares favorably with C12 O2(18) isotope lasers and CO lasers. The advantages of tunable, high energy, high pressure pulsed lasers over tunable diode lasers and waveguide lasers, in combining high energies with a large tuning range, are evaluated for certain applications to remote sensing of atmospheric constituents and pollutants. Pulsed operation considerably increases the signal to noise ratio without seriously affecting the high spectral resolution of signal detection obtained with laser heterodyning.

Hess, R. V.↗
NASA NTRS1976

Tunable high pressure lasers

Atmospheric transmission of high energy CO2 lasers is considerably improved by high pressure operation which, due to pressure broadening, permits tuning the laser lines off atmospheric absorption lines. Pronounced improvement is shown for horizontal transmission at altitudes above several kilometers and for vertical transmission through the entire atmosphere. Applications of tunable high pressure CO2 lasers to energy transmission and to remote sensing are discussed along with initial efforts in tuning high pressure CO2 lasers.

Hess, R. V.↗
NASA NTRS1979

Multicyclic Controllable Twist Rotor Data Analysis

Rsults provide functional relationship between rotor performance, blade vibratory loads and dual control settings and indicate that multicyclic control produced significant reductions in blade flatwise bending moments and blade root actuator control loads. Higher harmonic terms of servo flap deflection were found to be most pronounced in flatwise bending moment, transmission vertical vibration and pitch link vibratory load equations. The existing test hardware represents a satisfactory configuration for demonstrating MCTR technology and defining a data base for additional wind tunnel testing.

Wei, F. S.↗
NASA NTRS2012

The Organic Aerosols of Titan's Atmosphere

One of Titan's many characteristics is the presence of a haze that veils its surface. This haze is composed of heavy organic particles and determining the chemical composition of these particles is a primary objective for future probes that would conduct in situ analysis. Meanwhile, solar occultations provide constraints on the optical characteristics of the haze layer. This paper describes solar occultation observations obtained by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. These observations strongly constrain the optical characteristics of the haze layer. We detail the different steps involved in the processing of these data and apply them to two occultations that were observed at the South Pole and at the equator in order to investigate the latitudinal dependence of optical properties. The light curves obtained in seven atmospheric windows between 0.933-microns to 5-microns allow us to characterize atmospheric layers from 300 km to the surface. Very good fits of the light curves are obtained using a simple profile of number density of aerosols that is characterized by a scale height. The main difference between the South Pole and the equator is that the value of the scale height increases with altitude at the South Pole whereas it decreases at the equator. The vertically integrated amount of aerosols is similar at the two locations. The curve describing the cross-section versus wavelength is identical at the two locations suggesting that the aerosols have similar characteristics. Finally, we find that the two-way vertical transmission at 5-microns is as large as 80% at both locations.

solar occultation↗
NASA NTRS2021

Persistence of a Potential Pathogen on a Plant Microbiome-Does Seed Sanitization Matter?

Microbial interactions on, in, and around the seeds can have profound effects on plant growth, development, and productivity. These interactions can be casual or intimate in nature, but ultimately they all contribute in varying degrees to an ever-evolving microbiome. Plant microbiomes have been investigated over decades and new data continue to reveal how microbiomes play an important role in the plant’s success. Many eubacteria and fungi have been found to have a symbiotic relationship with plants and other microorganisms. The source of the plant microbiome on adult plants is provided by the seed via vertical transmission to leaf, root, flowers or fruit, as well as the surrounding environment.

Anirudha R. Dixit↗
NASA NTRS1994

Feasibility study of transmission of OTV camera control information in the video vertical blanking interval

The Operational Television system at Kennedy Space Center operates hundreds of video cameras, many remotely controllable, in support of the operations at the center. This study was undertaken to determine if commercial NABTS (North American Basic Teletext System) teletext transmission in the vertical blanking interval of the genlock signals distributed to the cameras could be used to send remote control commands to the cameras and the associated pan and tilt platforms. Wavelength division multiplexed fiberoptic links are being installed in the OTV system to obtain RS-250 short-haul quality. It was demonstrated that the NABTS transmission could be sent over the fiberoptic cable plant without excessive video quality degradation and that video cameras could be controlled using NABTS transmissions over multimode fiberoptic paths as long as 1.2 km.

White, Preston A., III↗
NASA NTRS1973

Tropospheric Transmissivity Measurements Using the Raman Nitrogen Lidar Technique

LIDAR measurements in Azusa, California, during October 1972, were made in which the backscattered Raman-shifted nitrogen return was ratioed at different altitudes in order to obtain transmissivity. Rawinsonde data from nearby El Monte were used to determine the temperature and nitrogen number density altitude profiles. These data and other meteorological data are compared to the vertical aerosol and transmissivity structure determined by LIDAR. Also data analysis techniques are shown for obtaining q2 (transmissivity) and beta (attenuation coefficient) as a function of altitude.

McCormick, M. P.↗
NASA NTRS1973

Continuous liquid level measurements with time-domain reflectometry

Description of the basic principles of radar measurements of cryogenic liquid levels in storage vessels by time-domain reflectometry. The probe consists of a right circular coaxial transmission line positioned vertically in the storage vessel and having holes drilled in the outer conductor to permit penetration of the liquid into the annular gap. RF pulses transmitted through the probe are reflected at liquid/gas interface and returned for sampling at the input. The measured delay of the return pulse is displayed as the level of liquid in the vessel.

Cruz, J. E.↗
NASA NTRS1976

Effective mie-scattering and CO2 absorption in the dust-laden Martian atmosphere and its impact on radiative-convective temperature changes in the lower scale heights

A time dependent computer model of radiative-convective-conductive heat transfer in the Martian ground-atmosphere system was refined by incorporating an intermediate line strength CO2 band absorption which together with the strong-and weak-line approximation closely simulated the radiative transmission through a vertically inhomogeneous stratification. About 33,000 CO2 lines were processed to cover the spectral range of solar and planetary radiation. Absorption by silicate dust particulates, was taken into consideration to study its impact on the ground-atmosphere temperature field as a function of time. This model was subsequently attuned to IRIS, IR-radiometric and S-band occultation data. Satisfactory simulations of the measured IRIS spectra were accomplished for the dust-free condition. In the case of variable dust loads, the simulations were sufficiently fair so that some inferences into the effect of dust on temperature were justified.

Pallmann, A. J.↗
NASA NTRS2018

Magnetic Gearing Research at NASA

Magnetic gearing is an alternative to mechanical gearing, where torque is transferred through magnetic force as opposed to contact force. The technology has the potential to be used in aircraft applications, without the lubrication, noise, and maintenance issues that can exist with mechanical gearing. Initial design and prototype development work was done at NASA to create a foundational understanding of the technology and the factors that influence its specific torque. The specific torque achieved through design optimization was found to be less than that of high-torque mechanical aircraft transmissions, but may be comparable to that of lower torque mechanical transmissions for electrified vertical takeoff and landing aircraft. The lessons learned from NASA's initial technology development and the direction of NASA's future work in field are discussed.

propulsion systems↗
NASA NTRS2018

Magnetic Gearing Research at NASA

Magnetic gearing is an alternative to mechanical gearing, where torque is transferred through magnetic force as opposed to contact force. The technology has the potential to be used in aircraft applications, without the lubrication, noise, and maintenance issues that can exist with mechanical gearing. Initial design and prototype development work was done at NASA to create a foundational understanding of the technology and the factors that influence its specific torque. The specific torque achieved through design optimization was found to be less than that of high-torque mechanical aircraft transmissions, but may be comparable to that of lower torque mechanical transmissions for electrified vertical takeoff and landing aircraft. The lessons learned from NASA's initial technology development and the direction of NASA's future work in field are discussed.

electric aircraft propulsion↗
NASA NTRS2004

Vertical Profiles of Aerosol Volume from High Spectral Resolution Infrared Transmission Measurements: Results

The high-resolution infrared absorption spectra of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment are utilized to derive vertical profiles of sulfate aerosol volume density and extinction coefficient. Following the eruption of Mt. Pinatubo in June 1991, the ATMOS spectra obtained on three Space Shuttle missions (1992, 1993, and 1994) provide a unique opportunity to study the global stratospheric sulfate aerosol layer shortly after a major volcanic eruption and periodically during the decay phase. Synthetic sulfate aerosol spectra are fit to the observed spectra, and a global fitting inversion routine is used to derive vertical profiles of sulfate aerosol volume density. Vertical profiles of sulfate aerosol volume density for the three missions over portions of the globe are presented, with the peak in aerosol volume density occurring from as low as 10 km (polar latitudes) to as high as 20 km (subtropical latitudes). Derived aerosol volume density is as high as 2-3.5 (mu)m(exp 3) per cubic centimeter +/-10% in 1992, decreasing to 0.2-0.5 (mu)m(exp 3) per cubic centimeter +/-20% in 1994, in agreement with other experiments. Vertical extinction profiles derived from ATMOS are compared with profiles from Improved Stratospheric And Mesospheric Sounder (ISAMS) and Cryogenic Limb Array Etalon Spectrometer (CLAES) that coincide in space and time and show good general agreement. The uncertainty of the ATMOS vertical profiles is similar to CLAES and consistently smaller than ISAMS at similar altitudes.

stratospheric aerosol↗
NASA NTRS1975

Vibrations transmitted to human subjects through passenger seats and considerations of passenger comfort

An experimental study was conducted to determine the vertical and lateral vibration-transmission characteristics of several types of transport vehicle seats (two aircraft and one bus) to obtain preliminary estimates and comparisons of the ride acceptability of the various seat types. Results of this investigation indicate that from the standpoint of human comfort the seats exhibit undesirable dynamic response characteristics. Amplification of floor vibrations occurred at the frequencies known to be most critical for human comfort in both vertical and lateral axes. An average transmissibility function for aircraft seats was tabulated together with the associated variability for use by designers who incorporate similar types of seats in their vehicles. The acceptability of vibrations resulting from floor inputs of 0.10g and 0.15g was low over a broad range of frequencies for both axes and all seat types, and was especially low at frequencies where the input was being amplified.

Leatherwood, J. D.↗
NASA NTRS1973

A simplified scheme for computing radiation transfer in the troposphere

A scheme is presented, for the heating of clear and cloudy air by solar and infrared radiation transfer, designed for use in tropospheric general circulation models with coarse vertical resolution. A bulk transmission function is defined for the infrared transfer. The interpolation factors, required for computing the bulk transmission function, are parameterized as functions of such physical parameters as the thickness of the layer, the pressure, and the mixing ratio at a reference level. The computation procedure for solar radiation is significantly simplified by the introduction of two basic concepts. The first is that the solar radiation spectrum can be divided into a scattered part, for which Rayleigh scattering is significant but absorption by water vapor is negligible, and an absorbed part for which absorption by water vapor is significant but Rayleigh scattering is negligible. The second concept is that of an equivalent cloud water vapor amount which absorbs the same amount of radiation as the cloud.

Katayama, A.↗
NASA NTRS1977

Dynamic characteristics of rotor blades with pendulum absorbers

The point transmission matrix for a vertical plane pendulum on a rotating blade undergoing combined flapwise bending, and chordwise bending and torsion is derived. The equilibrium equation of the pendulum is linearized for small oscillations about the steady state. A FORTRAN program was written for the case of a vertical plane pendulum attached to a uniform blade with flapwise bending degree of freedom for cantilever boundary conditions. The frequency has a singular value right at the uncoupled pendulum natural frequency and thus introduces two frequencies corresponding to the nearest natural frequency of the blade without pendulum. In both of these modes it was observed that the pendulum deflection is large. One frequency can be thought of as a coupled pendulum frequency and the other as a coupled bending and pendulum frequency.

Murthy, V. R.↗
NASA NTRS2012

Estimation and Bias Correction of Aerosol Abundance using Data-driven Machine Learning and Remote Sensing

Air quality information is increasingly becoming a public health concern, since some of the aerosol particles pose harmful effects to peoples health. One widely available metric of aerosol abundance is the aerosol optical depth (AOD). The AOD is the integrated light extinction coefficient over a vertical atmospheric column of unit cross section, which represents the extent to which the aerosols in that vertical profile prevent the transmission of light by absorption or scattering. The comparison between the AOD measured from the ground-based Aerosol Robotic Network (AERONET) system and the satellite MODIS instruments at 550 nm shows that there is a bias between the two data products. We performed a comprehensive analysis exploring possible factors which may be contributing to the inter-instrumental bias between MODIS and AERONET. The analysis used several measured variables, including the MODIS AOD, as input in order to train a neural network in regression mode to predict the AERONET AOD values. This not only allowed us to obtain an estimate, but also allowed us to infer the optimal sets of variables that played an important role in the prediction. In addition, we applied machine learning to infer the global abundance of ground level PM2.5 from the AOD data and other ancillary satellite and meteorology products. This research is part of our goal to provide air quality information, which can also be useful for global epidemiology studies.

Malakar, Nabin K.↗