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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 37 records · Page 2
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NASA NTRS2013

From BASE-ASIA Toward 7-SEAS: A Satellite-Surface Perspective of Boreal Spring Biomass-Burning Aerosols and Clouds in Southeast Asia

In this paper, we present recent field studies conducted by NASA's SMART-COMMIT (and ACHIEVE, to be operated in 2013) mobile laboratories, jointly with distributed ground-based networks (e.g., AERONET, http://aeronet.gsfc.nasa.gov/ and MPLNET, http://mplnet.gsfc.nasa.gov/) and other contributing instruments over northern Southeast Asia. These three mobile laboratories, collectively called SMARTLabs (cf. http://smartlabs.gsfc.nasa.gov/, Surface-based Mobile Atmospheric Research & Testbed Laboratories) comprise a suite of surface remote sensing and in-situ instruments that are pivotal in providing high spectral and temporal measurements, complementing the collocated spatial observations from various Earth Observing System (EOS) satellites. A satellite-surface perspective and scientific findings, drawn from the BASE-ASIA (2006) field deployment as well as a series of ongoing 7-SEAS (2010-13) field activities over northern Southeast Asia are summarized, concerning (i) regional properties of aerosols from satellite and in situ measurements, (ii) cloud properties from remote sensing and surface observations, (iii) vertical distribution of aerosols and clouds, and (iv) regional aerosol radiative effects and impact assessment. The aerosol burden over Southeast Asia in boreal spring, attributed to biomass burning, exhibits highly consistent spatial and temporal distribution patterns, with major variability arising from changes in the magnitude of the aerosol loading mediated by processes ranging from large-scale climate factors to diurnal meteorological events. Downwind from the source regions, the tightly coupled-aerosolecloud system provides a unique, natural laboratory for further exploring the micro- and macro-scale relationships of the complex interactions. The climatic significance is presented through large-scale anti-correlations between aerosol and precipitation anomalies, showing spatial and seasonal variability, but their precise cause-and-effect relationships remain an open-ended question. To facilitate an improved understanding of the regional aerosol radiative effects, which continue to be one of the largest uncertainties in climate forcing, a joint international effort is required and anticipated to commence in springtime 2013 in northern Southeast Asia.

biomass burning aerosols↗
NASA NTRS1992

Melt production in large-scale impact events: Calculations of impact-melt volumes and crater scaling

Along with an apparent convergence in estimates of impact-melt volumes produced during planetary impact events, intensive efforts at deriving scaling relationships for crater dimensions have also yielded results. It is now possible to examine a variety of phenomena associated with impact-melt production during large cratering events and apply them to planetary problems. This contribution describes a method of combining calculations of impact-melt production with crater scaling to investigate the relationship between the two.

Cintala, Mark J.↗
NASA NTRS2011

Experimental Investigation and Analysis of an Annular Pogo Accumulator

An experimental investigation was conducted on a scaled annular pogo accumulator for the Ares I Upper Stage. The test article was representative of the LO2 feedline and preliminary accumulator design, and included multiple designs of a perforated ring connecting the accumulator to the core feedline flow. The system was pulse tested in water over a range of pulse frequency and flow rates. Time dependent measurements of pressure at various locations in the test article were used to extract system compliance, inertance, and resistance. Preliminary results indicated a significant deviation from standard orifice flow theory and suggest a strong dependence on feedline average velocity. In addition, several CFD analyses were conducted to investigate the details of the time variant flow field. Both two-dimensional and three-dimensional simulations were performed with time varying boundary conditions used to represent system pulsing. The CFD results compared well with the sub-scale results and demonstrated the influence of feedline average velocity on the flow into and out of the accumulator. This paper presents updated results of the investigation including a parametric design space for determining resistance characteristics. Using the updated experimental results a new scaling relationship has been defined for shear flow over a cavity. A comparison of sub-scale and full scale CFD simulations provided early verification of the scaling of the fluid flowfield and resistance characteristics.

Peugeot, John↗
NASA NTRS1978

Relationships between particle precipitation and auroral forms

The paper discusses recent measurements pertaining to the relationship between high-latitude particle (electron) precipitation and auroras. The discussion covers three topics: the large-scale relationships between auroral forms and the particle populations of the magnetosphere as determined from satellite measurements; (2) the relationship between satellite and sounding-rocket observations, particularly field-aligned pitch-angle distributions and upward field-aligned currents measured in the vicinity of auroral forms; and (3) recent results on the interaction of auroral electrons with the atmosphere.

Burch, J. L.↗
NASA NTRS1976

Model and full-scale large transport airframe noise

Results are presented for an airframe noise experiment intended to obtain airframe noise data of a 0.03-scale model of a large transport aircraft in a flow facility for comparison with similar airframe noise data from full-scale flyover tests of the same aircraft. The test model simulated the landing and cruise configuration, including individual flap systems. Considerable noise is found to be associated with the extension of the model's leading edge flap system and to be reduced across the noise spectra when the gaps between the leading-edge flaps and the leading edge of the wing are sealed. Amplitude and frequency scaling relationships are developed which correlate respective data for a variety of aircraft configurations. Normalized model landing gear noise failed to simulate full-scale data.

Shearin, J. G.↗
NASA NTRS1988

Aerodynamics of Seeing on Large Transport Aircraft

Efforts were undertaken to obtain a set of data that examined the level of turbulence and the scale sizes in the shear layer existing over the fence quieted cavity on the NASA-Ames Kuiper Airborne Observatory (KAO). These data were to be taken during the present study and compared with data taken from previous wind tunnel experiments, for which both aerodynamic and direct optical measurements were made. The data obtained during the present study were presented and discussed in light of their impact on the quality of optical images, that is, seeing through the shear layer. In addition, scaling relationships were presented that allow optical data obtained in one aerodynamic environment to be estimated for another one at perhaps different Mach numbers, scale sizes, or aircraft configurations.

Rose, William C.↗
NASA NTRS2010

X-Ray Variability of ULXs and the Mass of NGC 5408 X-1

Several of the brightest ULXs now have detections of characteristic variability timescales in the X-ray; including quasiperiodic oscillation and power spectral break frequencies. The best example at present is NGC5408 X-1, which has shown X-ray timing and spectral behavior closely analogous to that observed in Galactic, stellar mass black holes, but at systematically higher luminosities and longer timescales. I will present recent XMM-Newton observations of X-1 that reveal a QPO frequency -- spectral index relationship consistent with that seen in stellar-mass black hole systems of known mass. I will show that extension of the frequency -- spectral index scaling relationship from the stellar-mass systems to X-1 suggests that it harbors an intermediate mass black hole. I will also present the results of regular, ongoing monitoring of X-1 with Swift, including the discovery of an 113 day periodicity that is likely the orbital period of the black hole binary.

Strohmayer, Todd↗
NASA NTRS1977

Acoustic loads on upper-surface-blown powered-lift systems

Powered-lift concepts are utilized in aircraft currently under development for STOL application. One of the concepts, upper surface blowing, places the jet exit just above the upper surface of the wing to produce powered lift from the jet exhaust blowing over the deflected flap. New data are presented to show the effects of airspeed, angle of attack, and angle of jet impingement. Scaling relationships are investigated concerning their applicability for extrapolating data to a different model size. The effects of a number of test parameters are examined and full-scale spectra are predicted from model data. It is concluded that scale models are an effective means for obtaining fluctuating pressure spectra for use in aircraft design. The prediction of full-scale loads from model data will require geometrically accurate models and closely spaced measurement locations.

Willis, C. M.↗
NASA NTRS1986

Aerodynamics of seeing on large transport aircraft

Data were obtained in the full scale flight environment of the Kuiper Airborne Observatory (KAO) on the nature of turbulent shear layer over the open cavity. These data were used to verify proposed aerodynamic scaling relationships to describe the behavior of the turbulent layers and to estimate the optical performance of systems of various wavelengths operating within the KAO environment. These data and wind tunnel data are used to scale the expected optical effects for a potential stratospheric observatory for infrared astronomy (SOFIA) in which a telescope approximately 3.5 times larger than that on the KAO is envisioned. It appears that the use of combinations of active and passive aeromechanical flow control techniques can improve the optical behavior of systems in the SOFIA environment. Experiments to verify these potential improvements can be performed on the KAO with sufficient modifications to the cavity and aero-mechanical technique installations.

Rose, W. C.↗
NASA NTRS1985

Experimental investigation of crater growth dynamics

This work is a continuation of an ongoing program whose objective is to perform experiments and to develop scaling relationships for large-body impacts onto planetary surfaces. The centrifuge technique is used to provide experimental data for actual target materials of interest. With both power and gas guns mounted on the rotor arm, it is possible to match various dimensionless similarity parameters, which have been shown to govern the behavior of large-scale impacts. The development of the centrifuge technique has been poineered by the present investigators and is documented by numerous publications, the most recent of which are listed below. Understanding the dependence of crater size upon gravity has been shown to be key to the complete determination of the dynamic and kinematic behavior of crater formation as well as ejecta phenomena. Three unique time regimes in the formation of an impact crater have been identified.

Schmidt, R. M.↗
NASA NTRS1994

Rime-, mixed- and glaze-ice evaluations of three scaling laws

This report presents the results of tests at NASA Lewis to evaluate three icing scaling relationships or 'laws' for an unheated model. The laws were LWC x time = constant, one proposed by a Swedish-Russian group and one used at ONERA in France. Icing tests were performed in the NASA Lewis Icing Research Tunnel (IRT) with cylinders ranging from 2.5- to 15.2-cm diameter. Reference conditions were chosen to provide rime, mixed and glaze ice. Scaled conditions were tested for several scenarios of size and velocity scaling, and the resulting ice shapes compared. For rime-ice conditions, all three of the scaling laws provided scaled ice shapes which closely matched reference ice shapes. For mixed ice and for glaze ice none of the scaling laws produced consistently good simulation of the reference ice shapes. Explanations for the observed results are proposed, and scaling issues requiring further study are identified.

Anderson, David N.↗
NASA NTRS1987

Centrifuge impact cratering experiments: Scaling laws for non-porous targets

This research is a continuation of an ongoing program whose objective is to perform experiments and to develop scaling relationships for large body impacts onto planetary surfaces. The development of the centrifuge technique has been pioneered by the present investigator and is used to provide experimental data for actual target materials of interest. With both powder and gas guns mounted on a rotor arm, it is possible to match various dimensionless similarity parameters, which have been shown to govern the behavior of large scale impacts. Current work is directed toward the determination of scaling estimates for nonporous targets. The results are presented in summary form.

Schmidt, Robert M.↗
NASA NTRS1985

Centrifuge Impact Cratering Experiments

The kinematics of crater growth, impact induced target flow fields and the generation of impact melt were determined. The feasibility of using scaling relationships for impact melt and crater dimensions to determine impactor size and velocity was studied. It is concluded that a coupling parameter determines both the quantity of melt and the crater dimensions for impact velocities greater than 10km/s. As a result impactor radius, a, or velocity, U cannot be determined individually, but only as a product in the form of a coupling parameter, delta U micron. The melt volume and crater volume scaling relations were applied to Brent crater. The transport of melt and the validity of the melt volume scaling relations are examined.

Schmidt, R. M.↗
NASA NTRS1983

Thermoneutral zone and scaling of metabolic rate on body mass in small mammals

A 4-species animal model suitable for experimental study of the effect of change in gravitational loading on the scale relationship between metabolic rate and total body mass is used to study the effect of temperature on metabolic rate in six male animals, 8-10 months of age, of each of the four species in the ambient temperature range 20-36 C. The measurements taken permitted partitioning of total body heat output into sensible heat loss by radiation, conduction and convection, and into latent heat loss by evaporation of water from the body surface. It is shown that the condition of thermoneutrality is important for metabolic scale effect studies, and that the thermoneutral zone for the species considered here is a narrow one.

Pace, N.↗
NASA NTRS2023

Compressible Turbulence in the Near-Sun Solar Wind Parker Solar Probe's First Eight Perihelia

Many questions remain about the compressibility of solar wind turbulence with respect to its origins and properties. Low plasma beta (ratio of thermal to magnetic pressure) environments allow for the easier generation of compressible turbulence, enabling study of the relationship between density fluctuations and turbulent Mach number. Utilizing Parker Solar Probe plasma data, we examine the normalized proton density fluctuations as a function of turbulent Mach number M t conditioned on plasma beta and cross helicity. With consideration of statistical error in the parameters computed from in situ data, we find a general result consistent with both linear-wave theory and nearly incompressible turbulence in an inhomogeneous background field. We compare observational results conditioned on plasma beta and cross helicity with 3D magnetohydrodynamic simulations and observe rather significant similarities with respect to how those parameters affect the proportionality between density fluctuations and turbulent Mach number. This study further investigates the complexity of compressible turbulence as viewed by the density scaling relationship and may help better understand the compressible environment of the near-Sun solar wind.

Manuel Enrique Cuesta↗
NASA NTRS1999

Low-Power Ion Thruster Development Status

An effort is on-going to examine scaling relationships and design criteria for ion propulsion systems, and to address the need for a light weight, low power, high specific impulse propulsion option for small spacecraft. An element of this activity is the development of a low-power (sub-0.5 kW) ion thruster. This development effort has led to the fabrication and preliminary performance assessment of an 8 cm prototype xenon ion thruster operating over an input power envelope of 0.1-0.3 kW. Efficiencies for the thruster vary from 0.31 at 1750 seconds specific impulse at 0.1 kW, to about 0.48 at 2700 seconds specific impulse and 0.3 kW input power. Discharge losses for the thruster over this power range varied from about 320-380 W/A down to about 220-250 W/A. Ion optics performance compare favorably to that obtained with 30 cm ion optics, when scaled for the difference in beam area. The neutralizer, fabricated using 3 mm hollow cathode technology, operated at keeper currents of about 0.2-0.3 A, at a xenon flow rate of about 0.06 mg/s, over the 0.1-0.3 kW thruster input power envelope.

Patterson, Michael J.↗
NASA NTRS1963

On the use of dynamic models for studying launch vehicle buffet and ground-wind loads

The complex nature of the random aerodynamic input forces associated with transonic buffet and ground winds leads to difficulty in analytical treatment of the response of launch vehicles to these important loading conditions. The application of aeroelastically scaled models in the wind tunnel as a mechanical analog of the matharnatically complex problem requiring solution is described. Scaling relationships involved in this approach are developed and some checks on their validity are presented. Model design and support techniques are discussed, and some typical results given. Some problems arising from the increased size of launch vehicles are discussed.

Perry W. Hanson↗