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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Curb Mounting, Vertical Mobility, and Inverted Mobility on Rough Surfaces Using Microspine-Enabled Robots

Three robots that extend microspine technology to enable advanced mobility are presented. First, the Durable Reconnaissance and Observation Platform (DROP) and the ReconRobotics Scout platform use a new rotary configuration of microspines to provide improved soldier-portable reconnaissance by moving rapidly over curbs and obstacles, transitioning from horizontal to vertical surfaces, climbing rough walls and surviving impacts. Next, the four-legged LEMUR robot uses new configurations of opposed microspines to anchor to both manmade and natural rough surfaces. Using these anchors as feet enables mobility in unstructured environments, from urban disaster areas to deserts and caves.

microspines↗
NASA NTRS2015

Superelastic Ball Bearings: Materials and Design to Avoid Mounting and Dismounting Brinell Damage in an Inaccessible Press-fit Application-: Detailed Analysis - II

Rolling element bearings utilized in precision rotating machines require proper alignment, preload, and interference fits to ensure overall optimum performance. Hence, careful attention must be given to bearing installation and disassembly procedures to ensure the above conditions are met. Usually, machines are designed in such a way that bearings can be pressed into housings or onto shafts through the races without loading the rolling elements. However, in some instances, either due to limited size or access, a bearing must be installed or removed in such a way that the load path travels through the rolling elements. This can cause high contact stresses between the rolling elements and the races and introduces the potential for Brinell denting of the races. This paper is a companion to the Part I paper by the authors that discusses material selection and the general design philosophy for the bearing. Here, a more in-depth treatment is given to the design of a dent-resistant bearing utilizing a superelastic alloy, 60NiTi, for the races. A common bearing analysis tool based on rigid body dynamics is used in combination with finite element simulations to design the superelastic bearing. The primary design constraints are prevention of denting and avoiding the balls riding over the edge of the race groove during a blind disassembly process where the load passes through the rolling elements. Through an iterative process, the resulting bearing geometry is tailored to improve axial static load capability compared to a deep-groove ball bearing of the same size. The results suggest that careful selection of materials and bearing geometry can enable blind disassembly without damage to the raceways, which is necessary in the current application (a compressor in the International Space Station Environmental Control and Life Support System), and results in potential design flexibility for other applications, especially small machines with miniature bearings.

metals↗
NASA NTRS2016

A Cryogenic Waveguide Mount for Microstrip Circuit and Material Characterization

A waveguide split-block fixture used in the characterization of thin-film superconducting planar circuitry at millimeter wavelengths is described in detail. The test fixture is realized from a pair of mode converters, which transition from rectangular-waveguide to on-chip microstrip-line signal propagation via a stepped ridge-guide impedance transformer. The observed performance of the W-band package at 4.2K has a maximum in-band transmission ripple of 2dB between 1.53 and 1.89 times the waveguide cutoff frequency. This metrology approach enables the characterization of superconducting microstrip test structures as a function temperature and frequency. The limitations of the method are discussed and representative data for superconducting Nb and NbTiN thin film microstrip resonators on single-crystal Si dielectric substrates are presented.

U-yen, Kongpop↗
NASA NTRS2016

A Cryogenic Waveguide Mount for Microstrip Circuit and Material Characterization

A waveguide split-block fixture used in the characterization of thin-film superconducting planar circuitry at millimeter wavelengths is described in detail. The test fixture is realized from a pair of mode converters, which transition from rectangular-waveguide to on-chip microstrip-line signal propagation via a stepped ridge-guide impedance transformer. The observed performance of the W-band package at 4.2K has a maximum in-band transmission ripple of 2dB between 1.53 and 1.89 times the waveguide cutoff frequency. This metrology approach enables the characterization of superconducting microstrip test structures as a function temperature and frequency. The limitations of the method are discussed and representative data for superconducting Nb and NbTiN thin film microstrip resonators on single-crystal Si dielectric substrates are presented.

U-yen, Kongpop↗
NASA NTRS2017

Top-Mounted Propulsion Test Plans (TMP17)

NASA recently completed a study of propulsion cycles and nozzle types applicable to a 70-passenger, M1.6 supersonic airliner, paying especial attention to the noise produced during landing and take-off. The results of the study were validated in a model-scale test at NASA Glenn last summer. The findings of that study and test, along with other studies, have resulted in a new strategy for achieving the Commercial Supersonic Technologys goals for noise and performance. Key to that strategy is moving the propulsion to the top-side of the vehicle and modifying the nozzle and inlet to maximally shield the propulsion noise while maintaining efficient operation. Installed exhaust configurations have been designed to minimize the exhaust noise using new acoustic design tools. A test planned for the fall of 2017 will validate both the new design tools and the low-noise concept using a new translating phased array. During the test, questions regarding modifications of convected waves in the jet near-field that are key to new understandings of aft jet noise will be addressed. Also, to better tie rig results to real-world measurements, a model-scale version of a nozzle that was flight tested by Glenn Research Center in 2001 will be tested.

Jet noise↗
NASA NTRS2019

PIV/Phased Array/Far-Field Noise Measurements of a Low-Noise Top-Mounted Propulsion Installation for a Supersonic Airliner

A model-scale exhaust system was tested to validate low-noise concepts and noise prediction methods. The tests involved far-field acoustics, translating phased array, and particle image velocimetry; this report covers the far-field acoustic measurements. Data were acquired for a series of nozzles with different chevron designs, both uninstalled and installed on a representative aircraft planform. The impact of the various chevron treatments on the far-field noise was documented, along with the impact of the pylon and planform. For the baseline nozzle, installation produced a 2 EPNdB (Effective Perceived Noise in deciBels) reduction, as assumed in system studies. Chevrons were used to shift noise sources upstream to maximize the installation benefits and to reduce unshielded sources downstream. These resulted in reductions of 4-5 EPNdB...

Bridges, James↗
NASA NTRS2021

3. Climbing to the Top of Mount Fuji: Uniting Theory and Observations of Oxygen Triple Isotope Systematics

The near-simultaneous discovery of both minor isotopes of oxygen in 1929 was a watershed moment for modern science, to say nothing of its impacts on isotope geochemistry. At the time, oxygen was the international standard for atomic weight, as it had been for over twenty-five years. However, chemists and physicists had grown fond of different definitions: physicists used the weight of the 16O atom, while chemists used half the weight of atmospheric oxygen (O2) to define the precise weight of 16 atomic mass units. While they usually avoided direct conflicts, these contrasting definitions found an unexpected impasse in the near-infrared absorption spectrum of atmospheric oxygen: it contained a series of faint lines that could not be explained by any known atmospheric constituents.

Laurence Y. Yeung↗
NASA NTRS2021

Impacts of the Eruption of Mount Pinatubo on Surface Temperatures and Precipitation Forecasts With the NASA GEOS Subseasonal-to-Seasonal System

A contemporary seasonal forecasting system is used to study the impacts of a volcanic sulfate injection into the stratosphere on the seasonal forecasts for surface temperatures, the El Niño Southern Oscillation (ENSO), and precipitation. The focus is a case study of the June 1991 eruption of Mt. Pinatubo, Philippines and the period from July 1991 to February 1992. Version 2 of the Goddard Earth Observing System (GEOS) subseasonal-to-seasonal (S2S) forecasting system is used in this study. GEOS-S2S includes the GOddard Chemistry, Aerosols, Radiation and Transport (GOCART) aerosol module, which allows to prognostically simulate aerosol distributions. GOCART is coupled to the radiation and cloud modules to include the impact of the eruption on forecasted radiation and precipitation. The coupled GEOS-S2S system was initialized in May 1991 with fields based on observations to produce ten-member 9-month forecasts with and without the volcanic sulfur injection. The results of these ensemble experiments demonstrate that including Mt. Pinatubo in seasonal forecasts would improve the forecasts of the 1991–1992 global mean temperature and precipitation but worsen the forecast of ENSO by strengthening of El Niño beyond what showed in observations. Most significant changes in the forecasts of temperatures and precipitation are limited to the tropics. The only land area where the inclusion of Pinatubo significantly lowered the forecasted precipitation is tropical Africa.

Mt. Pinatubo↗