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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

3D Drop Size Distribution Extrapolation Algorithm Using a Single Disdrometer

Determining the Z-R relationship (where Z is the radar reflectivity factor and R is rainfall rate) from disdrometer data has been and is a common goal of cloud physicists and radar meteorology researchers. The usefulness of this quantity has traditionally been limited since radar represents a volume measurement, while a disdrometer corresponds to a point measurement. To solve that problem, a 3D-DSD (drop-size distribution) method of determining an equivalent 3D Z-R was developed at the University of Central Florida and tested at the Kennedy Space Center, FL. Unfortunately, that method required a minimum of three disdrometers clustered together within a microscale network (.1-km separation). Since most commercial disdrometers used by the radar meteorology/cloud physics community are high-cost instruments, three disdrometers located within a microscale area is generally not a practical strategy due to the limitations of these kinds of research budgets. A relatively simple modification to the 3D-DSD algorithm provides an estimate of the 3D-DSD and therefore, a 3D Z-R measurement using a single disdrometer. The basis of the horizontal extrapolation is mass conservation of a drop size increment, employing the mass conservation equation. For vertical extrapolation, convolution of a drop size increment using raindrop terminal velocity is used. Together, these two independent extrapolation techniques provide a complete 3DDSD estimate in a volume around and above a single disdrometer. The estimation error is lowest along a vertical plane intersecting the disdrometer position in the direction of wind advection. This work demonstrates that multiple sensors are not required for successful implementation of the 3D interpolation/extrapolation algorithm. This is a great benefit since it is seldom that multiple sensors in the required spatial arrangement are available for this type of analysis. The original software (developed at the University of Central Florida, 1998.- 2000) has also been modified to read standardized disdrometer data format (Joss-Waldvogel format). Other modifications to the software involve accounting for vertical ambient wind motion, as well as evaporation of the raindrop during its flight time.

Lane, John↗
NASA NTRS1991

Evaluation of bearing configurations using the single bearing tester in liquid nitrogen

Various bearing configurations were tested using the Marshall Space Flight Center single bearing tester with LN2 as the cryogenic coolant. The baseline was one Rocketdyne phase one high pressure oxidizer turbopump (HPOTP) pump end 45-mm bore bearing. The bearing configurations that were tested included a Salox/M cage configuration, a silicon nitride ball configuration, an elongated cage configuration, and a Bray 601 grease configuration.

Jett, T.↗
NASA NTRS1988

A Method for Producing a Shaped Contour Radiation Pattern Using a Single Shaped Reflector and a Single Feed

Eliminating the corporate feed network in shaped contour beam antennas will reduce the expense, weight, and RF loss of the antenna system. One way of producing a shaped contour beam without using a feed network is to use a single shaped reflector with a single feed element. For a prescribed contour beam and feed, an optimization method for designing the reflector shape is given. As a design example, a shaped reflector is designed to produce a continental U.S. coverage (CONUS) beam. The RF performance of the shaped reflector is then verified by physical optics.

Cherrette, A. R.↗
NASA NTRS1989

A method for producing a shaped contour radiation pattern using a single shaped reflector and a single feed

Eliminating the corporate feed network in shaped contour beam antennas will reduce the expense, weight, and RF loss of the antenna system. One way of producing a shaped contour beam without using a feed network is to use a single shaped reflector with a single feed element. For a prescribed contour beam and feed, an optimization method for designing the reflector shape is given. As a design example, a shaped reflector is designed to produce a continental U.S. coverage (CONUS) beam. The RF performance of the shaped reflector is then verified by physical optics.

Cherrette, Alan R.↗
NASA NTRS2015

Using Single-Scattering Albedo Spectral Curvature to Characterize East Asian Aerosol Mixtures

Spectral dependence of aerosol single-scattering albedo (SSA) has been used to infer aerosol composition. In particular, aerosol mixtures dominated by dust absorption will have monotonically increasing SSA with wavelength while that dominated by black carbon absorption has monotonically decreasing SSA spectra. However, by analyzing SSA measured at four wavelengths, 440, 675, 870, and 1020 nm from the Aerosol Robotic Network data set, we find that the SSA spectra over East Asia are frequently peaked at 675 nm. In these cases, we suggest that SSA spectral curvature, defined as the negative of the second derivative of SSA as a function of wavelength, can provide additional information on the composition of these aerosol mixtures. Aerosol SSA spectral curvatures for East Asia during fall and winter are considerably larger than those found in places primarily dominated by biomass burning or dust aerosols. SSA curvature is found to increase as the SSA magnitude decreases. The curvature increases with coarse mode fraction (CMF) to a CMF value of about 0.4, then slightly decreases or remains constant at larger CMF. Mie calculations further verify that the strongest SSA curvature occurs at approx. 40% dust fraction, with 10% scattering aerosol fraction. The nonmonotonic SSA spectral dependence is likely associated with enhanced absorption in the shortwave by dust, absorption by black carbon at longer wavelengths, and also the flattened absorption optical depth spectral dependence due to the increased particle size.

curvature↗
NASA NTRS2024

Characterizing Face Sheet/Core Disbonding Using the Single Cantilever Beam Test: Results from an International Round Robin

Test results from an international round robin are presented. The single cantilever beam (SCB) test was used to characterize face sheet/core disbonding in sandwich components in an effort to help standardization. Each of the seven participating laboratories performed a set of five baseline tests using the same protocol, however, using their own specific equipment. In addition, each laboratory performed two sets of tests with altered tests conditions which included using a test fixture with a translating carriage and performing the tests with different loading and unloading speeds. The orientation of the disbond front with respect to the honeycomb core cells was varied and the effect on the fracture toughness was also studied. Additional factors that could influence test results were investigated, such as the use of a saw cut starter disbond as an alternative to Teflon® release film, and the effects of using a face sheet doubler to increase the bending stiffness. For each set of tests, summary results such as load/displacements plots, observed disbond growth location and calculated energy release rates are reported and a comparison of results between labs is presented. Critical strain energy release rate measurements from SCB tests are also compared with measurements made from an alternative test, namely the double cantilever beam with uneven bending moments (DCB-UBM) test, which has been studied extensively at the Technical University of Denmark and proposed as a mixed-mode test standard. A set of recommendations are made with respect to improving the SCB test and a path to standardization is presented.

Ronald Krueger↗
NASA NTRS1985

Estimation of lift losses of hovering vehicles using a single jet

This paper discusses the development of handbook techniques for the preliminary assessment of V/STOL aircraft performance while hovering in the proximity of the ground. In particular, the suckdown forces due to entrainment are described for configurations using a single jet. Corrections to current methods are suggested from an analysis of recent large-scale test data.

Christiansen, R. S.↗
NASA NTRS2010

Assessment of the Damage Tolerance of Postbuckled Hat-Stiffened Panels Using Single-Stringer Specimens

A procedure is proposed for the assessment of the damage tolerance and collapse of stiffened composite panels using a single-stringer compression specimen. The dimensions of the specimen are determined such that the specimen s nonlinear response and collapse are representative of an equivalent multi-stringer panel in compression. Experimental tests are conducted on specimens with and without an embedded delamination. A shell-based finite element model with intralaminar and interlaminar damage capabilities is developed to predict the postbuckling response as well as the damage evolution from initiation to collapse.

Bisagni, Chiara↗
NASA NTRS1993

A 200 GHz tripler using a single barrier varactor

The GaAs Schottky varactor diode is the nonlinear device most commonly used for submillimeter wave harmonic generation. Output power adequate to serve as a local oscillator source for SIS tunnel junctions has been demonstrated with whisker-contacted GaAs Schottky varactor multipliers in waveguide mounts up to about 800 GHz. In this paper, we present results for a tripler to 200 GHz using a new multiplier device, the single barrier varactor (SBV). This new varactor has potential advantages such as stronger nonlinearities or special symmetry, which make it attractive for submillimeter wave frequency multiplication. The performance of a tripler using a SBV over a output frequency range from 186 to 207 GHz has been measured in a crossed waveguide mount. The theoretical performance of the device has been calculated using large signal analysis. A comparison of theoretical and measured results and a discussion of various losses in the mount and the varactor have also been presented.

Choudhury, Debabani↗
NASA NTRS2011

Radiation Protection Using Single-Wall Carbon Nanotube Derivatives

This invention is a means of radiation protection, or cellular oxidative stress mitigation, via a sequence of quenching radical species using nano-engineered scaffolds, specifically single-wall carbon nanotubes (SWNTs) and their derivatives. The material can be used as a means of radiation protection by reducing the number of free radicals within, or nearby, organelles, cells, tissue, organs, or living organisms, thereby reducing the risk of damage to DNA and other cellular components (i.e., RNA, mitochondria, membranes, etc.) that can lead to chronic and/or acute pathologies, including but not limited to cancer, cardiovascular disease, immuno-suppression, and disorders of the central nervous system. In addition, this innovation could be used as a prophylactic or antidote for accidental radiation exposure, during high-altitude or space travel where exposure to radiation is anticipated, or to protect from exposure from deliberate terrorist or wartime use of radiation- containing weapons.

Tour, James M.↗
NASA NTRS1996

Utilizing GPS to Determine Ionospheric Delay over the Ocean

Several spaceborne altimeters have been built and flown, and others are being developed to provide measurements of ocean and ice sheet topography. Until the launch of TOPEX, altimeters were single frequency systems incapable of removing the effects of ionospheric delay on the radar pulse. With the current state of the art in satellite altimetry, the ionosphere causes the largest single error when using single frequency altimeters. Ionospheric models provide the only recourse short of adding a second frequency to the altimeter. Unfortunately, measurements of the ionosphere are lacking over the oceans or ice sheets where they are most needed. A possible solution to the lack of data density may result from an expanded use of the Global Positioning System (GPS). This paper discusses how the reflection of the GPS signal from the ocean can be used to extend ionospheric measurements by simply adding a GPS receiver and downward-pointing antenna to satellites carrying single frequency altimeters. This paper presents results of a study assessing the feasibility and effectiveness of adding a GPS receiver and downward-pointing antenna to satellites carrying single frequency altimeters.

Katzberg, Stephen J.↗
NASA NTRS2023

Modeling holes and voids in three dimensions using a single element within the Extended Finite Element framework

This paper introduces a highly efficient computational approach using the extended finite element method to model three-dimensional mechanics of holes and voids. The defect is encapsulated within a single element with a tailored exponential enrichment function that captures the behavior near the discontinuity boundary and can account for the pressure acting on the void’s surface through an equivalent nodal force vector. The method’s results were compared against analytical solutions and conventional finite element method results for problems involving single and multiple holes. The comparison demonstrated that the method provides accurate stress concentration estimates while adhering to computational constraints.

Adnan Shahriar↗
NASA NTRS1992

Thermal protection systems manned spacecraft flight experience

Since the first U.S. manned entry, Mercury (May 5, 1961), seventy-five manned entries have been made resulting in significant progress in the understanding and development of Thermal Protection Systems (TPS) for manned rated spacecraft. The TPS materials and systems installed on these spacecraft are compared. The first three vehicles (Mercury, Gemini, Apollo) used ablative (single-use) systems while the Space Shuttle Orbiter TPS is a multimission system. A TPS figure of merit, unit weight lb/sq ft, illustrates the advances in TPS material performance from Mercury (10.2 lb/sq ft) to the Space Shuttle (1.7 lb/sq ft). Significant advances have been made in the design, fabrication, and certification of TPS on manned entry vehicles (Mercury through Shuttle Orbiter). Shuttle experience has identified some key design and operational issues. State-of-the-art ceramic insulation materials developed in the 1970's for the Space Shuttle Orbiter have been used in the initial designs of aerobrakes. This TPS material experience has identified the need to develop a technology base from which a new class of higher temperature materials will emerge for advanced space transportation vehicles.

Curry, Donald M.↗
NASA NTRS1995

Building an LO source at 1036 GHz for a receiver

The goal of the UMass work on this grant was to build an LO source at 1036 GHz for a receiver which was to be built at JPL. The 1 THz source will consist of a high power Gunn oscillator at 86 GHz followed by a cascaded pair of planar diode doublers and finally a whisker contacted tripler. All multipliers will use single mode waveguide mounts. This use of single mode waveguide even for the final mount is a departure from the original plan, and reflects the progress that has been made in fabricating small structures. The advantages to the use of waveguide over a quasi-optical approach are that the complete system is much more compact, and much easier to use.

Erickson, Neal R.↗
NASA NTRSDate not supplied

Best Practices for Predicting Acoustics of a Single Rotor Using the NASA RVLT Conceptual Design Toolchain

To facilitate the development of the Urban Air Mobility (UAM) market, the NASA Revolutionary Vertical Lift Technology Project has created the Conceptual Design Toolchain, a suite of tools developed and/or selected to assist rotorcraft designers in all stages of rotorcraft design. Of particular interest to the UAM noise community are the following two steps in this toolchain: comprehensive analysis and acoustic prediction. Since the UAM application is relatively new, there is a need for a systematic study on how best to utilize these codes. To this end, the current study documents best practices for using the comprehensive analysis codes, CAMRAD II and CHARM, along with the acoustic code AARON. Two single rotors are considered: i) a simple rotor and ii) a rotor that is more exemplary of what UAM designers might use. Best practices are presented for the prediction of both tonal and broadband self-noise, along with the corresponding results. The goal is to provide conceptual designers the tools to conduct accurate noise prediction using the RVLT Conceptual Design Toolchain.

Acoustics↗
NASA NTRS1976

Acquisition of quantitative physiological data and computerized image reconstruction using a single scan TV system

A single-scan radiography system has been interfaced to a minicomputer, and the combined system has been used with a variety of fluoroscopic systems and image intensifiers available in clinical facilities. The system's response range is analyzed, and several applications are described. These include determination of the gray scale for typical X-ray-fluoroscopic-television chains, measurement of gallstone volume in patients, localization of markers or other small anatomical features, determinations of organ areas and volumes, computer reconstruction of tomographic sections of organs in motion, and computer reconstruction of transverse axial body sections from fluoroscopic images. It is concluded that this type of system combined with a minimum of statistical processing shows excellent capabilities for delineating small changes in differential X-ray attenuation.

Baily, N. A.↗