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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Adaptive filtering and prediction of the Southern Oscillation index

Singular spectrum analysis (SSA), a variant of principal component analysis, is applied to a time series of the Southern Oscillation index (SOI). The analysis filters out variability unrelated to the Southern Oscillation and separates the high-frequency, 2- to 3-year variability, including the quasi-biennial oscillation, from the lower-frequency 4- to 6-year El Nino cycle. The maximum entropy method (MEM) is applied to forecasting the prefiltered SOI. Prediction based on MEM-associated autoregresive models has useful skill for 30-36 months. A 1993-1994 La Nina event is predicted based on data through February 1992.

Keppenne, Christian L.↗
NASA NTRS1972

Exploratory flight investigation of aircraft response to the wing vortex wake generated by jet transport aircraft

The effect of intercepting wing tip vortices generated by large jet transports, including jumbo jets, over separation distances from 1 nautical mile to 15 nautical miles is evaluated on the basis of the response of a vortex probe airplane in the roil mode. The vortex probe test aircraft included a representative general aviation airplane, an executive jet, a fighter, and light and medium weight jet transports. The test conditions and airplane configurations were comparable to those normally used during takeoff, landing, or holding pattern operations. For flight safety the tests were performed at altitudes from 9500 feet to 12,500 feet. In addition to an evaluation of the probe airplane response, a flight test technique is suggested for determining minimum separation distance, using as variable the ratio of vortex-induced roll acceleration to maximum lateral control acceleration and the gross weight of the generating aircraft.

Andrews, W. H.↗
NASA NTRS1981

Software control program for 25 kW breadboard testing

A data acquisition software program developed to operate in conjunction with the automated control system of the 25 kW PM Electric Power System Breadboard Test facility is described. The proram provides limited interactive control of the breadboard test while acquiring data and monitoring parameters, allowing unattended continuous operation. The breadboard test facility has two positions for operating separate configurations. The main variable in each test setup is the high voltage Ni-Cd battery.

Pajak, J. A.↗
NASA NTRS1981

Picture gallery: A structured presentation of OAO-2 photometric data supported by UBV, ANS, and TD1 observations

Stellar fluxes for 531 stars in the wavelength range lambda 5500-1330A lambda are presented in the form of graphs. The stars are divided into 52 different categories on the basis of their spectral types and objects within one category are shown together. The agreement between the various ultraviolet photometric systems for early type stars is generally better than 0.10 mag. Stars with known and/or observed variability have been grouped separately. A list of stars with observed photometric properties which are indicative of stellar or interstellar anomalies is also provided.

Koornneed, J.↗
NASA NTRS1981

Chromospheres and coronae in binary systems

Recent observations and spectral analysis of chromospheres and coronae are discussed for various types of binary systems containing cool stars. These include the W UMa-type systems, the RS CVn variables, and selected widely separated binary systems such as VV Cephei and the giant stars in the Hyades cluster. In many cases evidence for extreme examples of solar activity are found. Radiative losses in ultraviolet resonance lines can be at least one or two orders of magnitude larger than those found in the quiet sun. In lambda And, a RS CVn type system, there is evidence for inhomogeneous structure in the chromosphere and transition region. Rotation appears to be a determinant in the energy losses of these atmospheres although not the only one.

Dupree, A. K.↗
NASA NTRS1984

Cockpit Window Edge Proximity Effects on Judgements of Horizon Vertical Displacement

To quantify the influence of a spatially fixed edge on vertical displacement threshold, twenty-four males (12 pilots, 12 non-pilots) were presented a series of forced choice, paired comparison trials in which a 32 deg arc wide, thin, luminous horizontal stimulus line moved smoothly downward through five angles from a common starting position within a three second-long period. The five angles were 1.4, 1.7, 2, 2.3, and 2.6 deg. Each angle was presented paired with itself and the other four angles in all combinations in random order. For each pair of trials the observer had to choose which trial possessed the largest displacement. A confidence response also was made. The independent variable was the angular separation between the lower edge of a stable 'window' aperture through which the stimulus was seen to move and the lowest position attained by the stimulus. It was found that vertical displacement accuracy is inversely related to the angle separating the stimulus and the fixed window edge (p = .05). In addition, there is a strong tendency for pilot confidence to be lower than that of non-pilots for each of the three angular separations. These results are discussed in erms of selected cockpit features and as they relate to how pilots judge changes in aircraft pitch attitude.

Haines, R. F.↗
NASA NTRS1985

The Scaling of Coronal Models from One Star to Another

The requirements that must be met in order that stationary numerical corona models can be scaled from one star to another are discussed. A corona model is a solution of the conservation equations for mass, momentum, and energy, subject to appropriate boundary conditions, and of the equation of state. In general, the mass M and radius R of the star enter these equations and boundary conditions as free parameters. A given solution can be scaled to other stars only if all equations can be rewritten in such a form that M and R do no longer appear explicitly as free parameters, but only implicitly as scaling factors of the variables. An adequate means to find these scaling factors is a homologous transformation: one multiplies all variables and parameters by separate constants (i.e., scaling factors) and requires that the equations and boundary conditions remain valid. This leads to a set of nonlinear relations between the transformation constants. Only if in this set the two constants associated with M and R can be chosen independently, can a given numerical corona model be scaled to arbitrary stars.

Hammer, R.↗
NASA NTRS1992

A new response surface approach for structural reliability analysis

This paper describes a new approach for computing structural reliability by post-processing previously computed probabilistic results for stress and strength. The objective is to provide an accurate method whereby independent probabilistic analyses for stress and strength functions can be performed independently and combined at a later time to compute probability of failure. The method provides a capability for testing different strength measures without the need for re-computing the probabilistic stress response. The proposed approach takes full account of the basic random variables effecting both stress and strength, and the failure region in the variable space identified during separate stress/strength probabilistic analyses. A simple closed-form example and a more complex analysis of a turbine blade subject to creep rupture is used to illustrate the method.

Thacker, B. H.↗
NASA NTRS1994

Highly crosslinked silicon polymers for gas chromatography columns

A new highly crosslinked silicone polymer particle for gas chromatography application and a process for synthesizing such copolymer are described. The new copolymer comprises vinyltriethoxysilane and octadecyltrichlorosilane. The copolymer has a high degree of crosslinking and a cool balance of polar to nonpolar sites in the porous silicon polymer assuring fast separation of compounds of variable polarity.

Shen, Thomas C.↗
NASA NTRS1961

Laminar Heat-Transfer and Pressure-Distribution Studies on a Series of Reentry Nose Shapes at a Mach Number of 19.4 in Helium

An experimental investigation has been conducted in the 2-inch helium tunnel at the Langley Research Center at a Mach number of 19.4 to determine the pressure distributions and heat-transfer characteristics of a family of reentry nose shapes. The pressure and heat-transfer-rate distributions on the nose shapes are compared with theoretical predictions to ascertain the limitations and validity of the theories at hypersonic speeds. The experimental results were found to be adequately predicted by existing theories. Two of the nose shapes were tested with variable-length flow-separation spikes. The results obtained by previous investigators of spike-nose bodies were found to prevail at the higher Mach number of the present investigation.

Wagner, Richard D., Jr.↗
NASA NTRS2003

The Plant Research Unit: An International Space Station Habitat

The Plant Research Unit (PRU) is one of six life science habitats being developed as part of the Space Station Biological Research Program. The PRU is designed for experiments in microgravity and will utilize the ISS Centrifuge Facility to provide gravity levels between microgravity and 29. The PRU will provide and control all aspects of a plant s needs in a nearly closed system. In other words, the shoot and root environments will not be open to the astronaut s environment except for experiment maintenance such as planting, harvesting and plant sampling. This also means that all lighting, temperature and humidity control, "watering," and air filtering and cleaning .must be done within strict limitations of volume, weight, power, and crew time while at the same time providing a very high level of reliability and a service life in excess of 10 years. The PRU will contain two plant chambers 31.5 cm tall, each with independent control of temperature, humidity, light level and photoperiod, CO2 level, nutrient and water delivery, and video and data acquisition. The PRU is currently in the preliminary design phase and a number of subsystem components have been prototyped for testing, including the temperature and humidity control systems, the plant chambers, the LED lighting system, the atmospheric control system and a variety of nutrient delivery systems. The LED prototype provides independent feedback control of 5 separate spectral bands and variable output between 0 and 1000 micro-mol sq m/sec. The water and nutrient delivery system (WNDS) prototypes have been used to test particulate based, thin film, and gel-based WNDS configurations.

Morrow, Robert↗
NASA NTRS2016

Extreme Mapping: Looking for Water on the Moon

There are many challenges when exploring extreme environments. Gathering accurate data to build maps about places that you cannot go is incredibly complex. NASA supports scientists by remotely operating robotic rovers to explore uncharted territories. One potential upcoming mission is to look for water near a lunar pole (the Resource Prospector mission). Learn about the technical hurdles and research steps that NASA takes before the mission. NASA practices on Earth with Mission Analogs which simulate the proposed mission. This includes going to lunar-type landscapes, building field networks, testing out rovers, instruments and operational procedures. NASA sets up remote science back rooms just as there are for actual missions. NASA develops custom Ground Data Systems software to support scientific mission planning and monitoring over variable time delays, and separate commanding software and infrastructure to operate the rovers.

MOON↗
NASA NTRS2020

SMAP Validation Experiment 2019-2020 (SMAPVEX19/20): Detection of Soil Moisture Under Forest Canopy

The retrieval of soil moisture under forest canopy has long been an important goal for low frequency remote sensing. The NASA mission started a dedicated field experiment in May 2019 by deploying two temporary soil moisture networks in northeast US that cover two separate SMAP pixels with variable degree of forest cover. The measurements will run through 2020 and they will be augmented with two intensive observation periods (IOP). The first IOP will be conducted in June-July 2020 and the other one in October 2020. The IOPs will see deployment of the airborne PALS (Passive Active L-band sensor) instrument, which is similar to the SMAP instrument, and intensive manual measurements of soil moisture and vegetation. The measurements also include tower-based radiometer observations with ground truth measurements within the instrument footprint. The early results have shown that the SMAP measurement signal at L-band is sensitive to soil moisture changes observed on the ground.

Andreas Colliander↗
NASA NTRS2021

SMAP Validation Experiment 2019-2021 (SMAPVEX19-21): Detection of Soil Moisture Under Temperate Forest Canopy

The retrieval of soil moisture under forest canopy has long been an important goal for low frequency remote sensing. The NASA mission started a dedicated field experiment in May 2019 by deploying two temporary soil moisture networks in northeast US that cover two separate SMAP pixels with variable degree of forest cover. The measurements will be augmented with two intensive observation periods (IOP). The first IOP is planned for July and the other one for October. The IOPs will see deployment of the airborne PALS (Passive Active L-band sensor) instrument, which is similar to the SMAP instrument, and intensive manual measurements of soil moisture and vegetation. The measurements also include tower-based radiometer observations with ground truth measurements within the instrument footprint. The early results have shown that the SMAP measurement signal at L-band is sensitive to soil moisture changes observed on the ground.

Yueh, Simon H.↗
NASA NTRS1995

Variable stars in the dwarf galaxy GR 8 (DDO 155)

Observations of the resolved stars in dwarf galaxy GR 8, obtained over the period 1980 February to 1994 March, are presented. Thirty-four separate epochs were searched for variable stars, and a total of six were found, of which one has Cepheid characteristics. After correction for Galactic extinction this single Cepheid yields a distance modulus of m - M = 26.75 +/- 0.35. This corresponds to a distance of 2.24 Mpc, placing GR 8 near the Local Group (LG) zero-velocity surface. The other five variable stars are very red, and possibly have long periods of order 100 days or more.

Tolstoy, Eline↗