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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Fabrication and Test of an Optical Magnetic Mirror

Traditional mirrors at optical wavelengths use thin metalized or dielectric layers of uniform thickness to approximate a perfect electric field boundary condition. The electron gas in such a mirror configuration oscillates in response to the incident photons and subsequently re-emits fields where the propagation and electric field vectors have been inverted and the phase of the incident magnetic field is preserved. We proposed fabrication of sub-wavelength-scale conductive structures that could be used to interact with light at a nano-scale and enable synthesis of the desired perfect magnetic-field boundary condition. In a magnetic mirror, the interaction of light with the nanowires, dielectric layer and ground plate, inverts the magnetic field vector resulting in a zero degree phase shift upon reflection. Geometries such as split ring resonators and sinusoidal conductive strips were shown to demonstrate magnetic mirror behavior in the microwave and then in the visible. Work to design, fabricate and test a magnetic mirror began in 2007 at the NASA Goddard Space Flight Center (GSFC) under an Internal Research and Development (IRAD) award Our initial nanowire geometry was sinusoidal but orthogonally asymmetric in spatial frequency, which allowed clear indications of its behavior by polarization. We report on the fabrication steps and testing of magnetic mirrors using a phase shifting interferometer and the first far-field imaging of an optical magnetic mirror.

Hagopian, John G.↗
NASA NTRS2018

High/Low Temperature Contactless Radio Frequency Probes

A contactless radio frequency (RF) probe with inverted microstrip lines. The RF probe includes a microstrip associated with a device under test, and a broadside coupled inverted microstrip line configured to exchange RF signals to a network analyzer.

Jordan, Jennifer L.↗
NASA NTRS2019

X-57 Mod 2 Motor Thermal Analysis

This work covers the refinement of thermal models from design estimates to actual fabricated performance. Matching the experimental data of the first fully electrified version of the X-57 Maxwell experimental vehicle requires high fidelity thermal analysis to sufficiently capture the electric motor and inverter temperature profiles. Qualification test data of the motors and inverters is used to validate finite element analysis models used to simulate thermal performance over mission transients. An additional thermal-hydraulic models is used to estimate flow characteristics through the propulsor nacelle and component heat sinks. After calibration of the higher order models, overall component sizing and peak temperature constraints can be distilled to reduced order models, to improve modelflexibility and utility.

Chin, Jeffrey C.↗
NASA NTRS2021

Characterizing the Effects of Two Ground-based Outdoor Microphone Configurations

Multiple International and Federal regulations stipulate the acquisition of aircraft noise shall be conducted using inverted pressure microphones over a round ground board. These ground boards are used to provide an acoustically hard reflecting surface, limiting the effects of the potentially absorptive ground local to the test location. The microphone location is also specified to be offset from the center of the board to limit the effects of acoustic diffraction off the board edge. In order to determine the effects of the ground board on the measured acoustic signal, a comprehensive measurement campaign was undertaken at NASA Langley Research Center. The experimental setup included multiple ground board configurations placed on top of a sand pit, in an otherwise anechoic chamber. Ground board configurations included a microphone inverted and offset over the round ground board and a microphone offset and flush mounted in the ground board.White noise was then used to investigate the ground board effects on the recorded signal. Normal impedance measurements were also acquired to determine the reflection coefficients of the sand and ground boards. Experimental results are discussed, along with implications for future research and development.Results indicate that both microphone configurations perform adequately up to 10 kHz. When the ground substrate is a soft material and the sound comes in at angles near grazing incidence the sound energy is attenuated above 1 kHz. Additionally, the plastic material used to construct the ground boards was found to be acoustically hard between 0.1 –3.0 kHz, and likely extending to higher frequencies.

Mark C. Anderson↗
NASA NTRS2020

The AERONET Version 3 Aerosol Retrieval Algorithm, Associated Uncertainties and Comparisons to Version 2

The Aerosol Robotic Network (AERONET) Version 3 (V3) aerosol retrieval algorithm is described, which is based on the Version 2 (V2) algorithm with numerous updates. Comparisons of V3 aerosol retrievals to those of V2 are presented, along with a new approach to estimate uncertainties in many of the retrieved aerosol parameters. Changes in the V3 aerosol retrieval algorithm include (1) a new polarized radiative transfer code (RTC), which replaced the scalar RTC of V2, (2) detailed characterization of gas absorption by adding NO2 and H2O to specify total gas absorption in the atmospheric column, specification of vertical profiles of all the atmospheric species, (3) new bidirectional reflectance distribution function (BRDF) parameters for land sites adopted from the MODIS BRDF/Albedo product, (4) a new version of the extraterrestrial solar flux spectrum, and (5) a new temperature correction procedure of both direct Sun and sky radiance measurements. The potential effect of each change in V3 on single scattering albedo (SSA) retrievals was analyzed. The operational almucantar retrievals of V2 versus V3 were compared for four AERONET sites: GSFC, Mezaira, Mongu, and Kanpur. Analysis showed very good agreement in retrieved parameters of the size distributions. Comparisons of SSA retrievals for dust aerosols (Mezaira) showed a good agreement in 440 nm SSA, while for longer wavelengths V3 SSAs are systematically higher than those of V2, with the largest mean difference at 675 nm due to cumulative effects of both extraterrestrial solar flux and BRDF changes. For non-dust aerosols, the largest SSA deviation is at 675 nm due to differences in extraterrestrial solar flux spectrums used in each version. Further, the SSA 675 nm mean differences are very different for weakly (GSFC) and strongly (Mongu) absorbing aerosols, which is explained by the lower sensitivity to a bias in aerosol scattering optical depth by less absorbing aerosols. A new hybrid (HYB) sky radiance measurement scan is introduced and discussed. The HYB combines features of scans in two different planes to maximize the range of scattering angles and achieve scan symmetry, thereby allowing for cloud screening and spatial averaging, which is an advantage over the principal plane scan that lacks robust symmetry. We show that due to an extended range of scattering angles, HYB SSA retrievals for dust aerosols exhibit smaller variability with solar zenith angles (SZAs) than those of almucantar (ALM), which allows extension of HYB SSA retrievals to SZAs less than 50∘ to as small as 25∘. The comparison of SSA retrievals from closely time-matched HYB and ALM scans in the 50 to 75∘ SZA range showed good agreement with the differences below ∼0.005. We also present an approach to estimate retrieval uncertainties which utilizes the variability in retrieved parameters generated by perturbing both measurements and auxiliary input parameters as a proxy for retrieval uncertainty. The perturbations in measurements and auxiliary inputs are assumed as estimated biases in aerosol optical depth (AOD), radiometric calibration of sky radiances combined with solar spectral irradiance, and surface reflectance. For each set of Level 2 Sun/sky radiometer observations, 27 inputs corresponding to 27 combinations of biases were produced and separately inverted to generate the following statistics of the inversion results: average, standard deviation, minimum and maximum values. From these statistics, standard deviation (labeled U27) is used as a proxy for estimated uncertainty, and a lookup table (LUT) approach was implemented to reduce the computational time. The U27 climatological LUT was generated from the entire AERONET almucantar (1993–2018) and hybrid (2014–2018) scan databases by binning U27s in AOD (440 nm), Angström exponent (AE, 440–870 nm), and SSA (440, 675, 870, 1020 nm). Using this LUT approach, the uncertainty estimates U27 for each individual V3 Level 2 retrieval can be obtained by interpolation using the corresponding measured and inverted combination of AOD, AE, and SSA.

Aliaksandr Siniuk↗
NASA NTRSDate not supplied

A Nonlinear Schur Complement Solver for CFD-Based Multidisciplinary Models

CFD-based multidisciplinary models are the fundamental building blocks of multidis- ciplinary design optimization frameworks. Linear and nonlinear solutions of these coupled models are difficult, especially when the Jacobian matrices represent a saddle point problem, where a block-diagonal corresponding to a discipline is non-invertible. These scenarios necessitate the use of a coupled solver algorithm such as the Newton’s method instead of the popular block Gauss– Seidel-based methods because of this non-invertible block. To address this challenge, we introduce a nonlinear Schur complement solver suitable for CFD-based multidisciplinary models. The solver leverages the specialized linear and nonlinear solvers of the CFD code, and therefore, does not require the solution of a large coupled linear system as the coupled Newton’s method. Further- more, because the solver primarily uses the specialized linear and nonlinear solvers of the CFD code, it does not suffer from the same robustness limitations as the coupled Newton’s method. In this work, we will implement this solver in NASA’s OpenMDAO framework and demonstrate its effectiveness using a CFD-based aeropropulsive model. The solver will contribute to the develop- ment of aeropropulsive design optimization and CFD-based design optimization methods with the ultimate goal of accelerating the design and integration of advanced propulsion systems.

Nonlinear Solvers↗
NASA NTRS2021

Anisotropic Wet Etching of Si as a Fabrication Tool Enabling 3-D Microphotonics Structures and Devices

It is shown that due to high speed and large volume of production, anisotropic wet etching of Si is a unique method of manufacturing high quality micropyramidal arrays for silicon photonics. Four types of arrays were fabricated: (i) square pyramids with the 54.7 slope of the sidewall surface, (ii) microcones with the 45 slope of sidewall surface, (iii) inverted square pyramids with 54.7 slope, and (iv) inverted triangular pyramids with different angles of the sidewalls. It is shown that the first type of arrays has a capability to produce tightly focused mid-wave infrared (MWIR) beams at the tips of the pyramids. Other arrays can be also used as light concentrators and various multifunctional microphotonic components.

Astratov, Vasily N.↗
NASA NTRSDate not supplied

An Investigation of the Dragonfly Mission Aeroshell/Parachute Dynamics through Subscale Drop Tests

The Dragonfly mission will place a rotorcraft/lander on Titan by 2034. The entry, descent, and landing system of the Dragonfly mission includes two parachutes: a drogue and a main. To provide needed data, subscale drop tests were used to conduct an experimental investigation of the aeroshell/parachute dynamics. The drop tests used a Disk-Gap-Band drogue parachute and two types of Ringslot main parachutes. All tests used a representative aeroshell which included the heatshield. All models were geometrically scaled to 16.7 percent. The model aeroshell had a diameter of 0.75 m. The model parachute nominal diameters were 0.9 m for the drogue and 2.78 m for the main. The aeroshell’s mass properties were dynamically scaled to simulate flight at an altitude of 4 km at Titan. This dynamic scaling allowed the conversion of model test results to full-scale Titan conditions. Onboard instrumentation on the aeroshell provided data on the rotation rates, from which the Euler angles were determined. Tests were conducted by lifting the models with a drone to an altitude of 350 m and dropping them inverted. Key results from these tests were: 1) the models were able to recover from the extreme inverted initial condition and settle to low-amplitude oscillations; 2) ninety nine percent of the time the oscillation amplitudes observed with the drogue parachute were 11.4 degrees or less; 3) ninety nine percent of the time the oscillation amplitudes observed with the 20 percent porosity main parachute were 15.4 degrees or less.

Parachutes↗
NASA NTRSDate not supplied

An Investigation of the Dragonfly Mission Aeroshell/Parachute Dynamics through Subscale Drop Tests

The Dragonfly mission will place a rotorcraft/lander on Titan by 2034. The entry, descent, and landing system of the Dragonfly mission includes two parachutes: a drogue and a main. To provide needed data, subscale drop tests were used to conduct an experimental investigation of the aeroshell/parachute dynamics. The drop tests used a Disk-Gap-Band drogue parachute and two types of Ringslot main parachutes. All tests used a representative aeroshell which included the heatshield. All models were geometrically scaled to 16.7 percent. The model aeroshell had a diameter of 0.75 m. The model parachute nominal diameters were 0.9 m for the drogue and 2.78 m for the main. The aeroshell’s mass properties were dynamically scaled to simulate flight at an altitude of 4 km at Titan. This dynamic scaling allowed the conversion of model test results to full-scale Titan conditions. Onboard instrumentation on the aeroshell provided data on the rotation rates, from which the Euler angles were determined. Tests were conducted by lifting the models with a drone to an altitude of 350 m and dropping them inverted. Key results from these tests were: 1) the models were able to recover from the extreme inverted initial condition and settle to low-amplitude oscillations; 2) ninety nine percent of the time the oscillation amplitudes observed with the drogue parachute were 11.4 degrees or less; 3) ninety nine percent of the time the oscillation amplitudes observed with the 20 percent porosity main parachute were 15.4 degrees or less.

Parachutes↗
NASA NTRSDate not supplied

Observation of Deep Convective Cloud-Top Height and Vertical Temperature Structure of Hurricane Using Hyperspectral Infrared Sounder and its Single-Field-View Retrieval Products

Hurricanes, severe tropical cyclones (TC), or typhoons are significant natural disasters that often result in substantial loss of life and property damage. Numerous studies have indicated that changes in TC intensity are closely linked to deep convective clouds (DCC), with stronger TCs typically exhibiting higher cloud top heights (CTH) compared to weaker TCs. The CTH can help determine if a tropical depression is at the onset of rapid intensification based on case studies. Therefore, accurate determination of TC CTH will be greatly helpful for monitoring TC development and studying TC dynamics. One traditional and most common method to derive CHT from satellite observations is using the thermal brightness temperature in atmospheric channels to match the sounding temperature profile. However, it was found that thermally derived CTH has a lower bias of approximately 1 km, and this bias tends to worsen for the tallest clouds. A new method using the hyperspectral infrared sounder will be presented. From the measurements of Cross-track Infrared Sounder (CrIS) on S-NPP and J-1, along with radiative transfer simulations, we identified the inverted-V spectral feature in the ozone (O3) band (near 9.6 μm) corresponding to high clouds. The depth of the inverted-V can be used to estimate the CTH. Since the depth is computed using the peak absorption O3 channel and the nearby most transparent O3 channel in this O3 band, the uncertainties associated with cloud emissivity and scattering by cloud particles in the traditional method can be ignored. From several hurricane case studies, we found that the CHT derived using this method can accurately capture the structure of the cloud tops in the eyewall, spiral rainbands, and surrounding regions. For example, Hurricane Dorian on September 2, 2019, showed a nicely outward-sloping and circular shape eye cloud in the early morning, but the circular shape of the eyewall cloud became distorted in the afternoon. For various hurricanes we examined, the distribution of CHT for the eyewall clouds differed significantly. To better study the thermodynamic structure of hurricane clouds, this research will analyze the vertical temperature profiles from a new single Field of View (SFOV) Sounder Atmospheric Products (SiFSAP), derived using CrIS and the Advanced Technology Microwave Sounder (ATMS) onboard SNPP and JPSS-1. SiFSAP has a spatial resolution of 15 km at nadir, which surpasses most global weather and climate models and other current operational sounding products. The combined use of ATMS and CrIS allows for retrievals near hurricane eyewalls and spiral rainbands. Wind fields from NASA’s Modern-Era Retrospective Analysis for Research and Applications Version-2 (MERRA-2) and ERA5 will be used to characterize transport, and comparisons between the model temperature and water vapor profiles with the corresponding SiFSAP products will also be provided.

SiFSAP↗
NASA NTRSDate not supplied

Probing ExoMiner for Effectiveness against False Alarms in Kepler Data

We present a study on the effectiveness of ExoMiner against False Alarms in Kepler data. ExoMiner is a deep learning model that was used to validate around 370 Kepler Objects of Interest. We follow the analysis conducted in Coughlin et al (2017) “DR25 Robovetter Completeness and Effectiveness” for Robovetter, a rule-based model used to vet TCEs for this data release and automatically generate the Q1-Q17 DR 25 KOI Table. The ExoMiner model is trained on observed transit data from Kepler Q1-Q17 DR25 and evaluated on Kepler inverted and scrambled data. The results provide a more comprehensive insight into the capacities and limitations of ExoMiner, especially the vetting of not-transit-like signals and, more generally, the use of deep learning models to model transit photometry data for vetting and validation purposes.

exoplanet↗
NASA NTRSDate not supplied

NASA's X-57 High Lift Motor Controller: Detailed Design, Test Results, and Outcomes

NASA's X-57 all-electric aircraft was a research project aimed at investigating lightweight and efficient electric propulsion components. The general approach was to utilize a distributed electric propulsion (DEP) design. An essential component of this design was the High Lift Motor Controller (HLMC), a motor drive which provided power to the High Lift Motors (HLMs) and High Lift Propellers (HLPs) responsible for providing additional thrust for take-off and landing. This paper presents the detailed design, test results, and outcomes from the development of the HLMC, a 14 kW, 1kg, 98.3% efficient, outer mold line (OML) cooled, silicon carbide (SiC) MOSFET-based inverter and controller.

Electric Aircraft↗
NASA NTRS2024

NASA's X-57 High Lift Motor Controller: Detailed Design, Test Results, and Outcomes

NASA's X-57 all-electric aircraft was a research project aimed at investigating lightweight and efficient electric propulsion components. The general approach was to utilize a distributed electric propulsion (DEP) design. An essential component of this design was the High Lift Motor Controller (HLMC), a motor drive which provided power to the High Lift Motors (HLMs) and High Lift Propellers (HLPs) responsible for providing additional thrust for take-off and landing. This paper presents the detailed design, test results, and outcomes from the development of the HLMC, a 14 kW, 1kg, 98.3% efficient, outer mold line (OML) cooled, silicon carbide (SiC) MOSFET-based inverter and controller.

Electric Aircraft↗
NASA NTRS1962

Study of Umbrella-Type Erectable Paraboloidal Solar Concentrators for Generation of Spacecraft Auxiliary Power

An investigation was made of some aspects of erectable umbrella-type paraboloidal solar-energy concentrators for use in spacecraft auxiliary power systems. An analysis is presented for the design of concentrators employing radial ribs and membrane-type coverings. The rib stiffness necessary to give a desired parabolic curvature upon erection is determined. Rib contour measurements were made in an upright and inverted position on an experimental 10-foot-diameter concentrator giving a focal length of 30.78 inches and 30.6 inches, respectively, as compared with a design focal length of 30 inches. Calorimetric tests employing spherical heat receivers showed a maximum geometrical concentrator efficiency of 75.3 percent with a concentration ratio of 92.2 at a focal length of approximately 30.5 inches. Within the scope of this investigation, it was found that, as the concentrator size increases, the weight per unit projected area increases, time to damp to one-half amplitude increases, and the natural frequency decreases. Umbrella-type solar concentrators appear to be feasible for power conversion systems using low concentration ratios; however, for large concentrators the time required to damp out disturbances may be a problem.

SPACECRAFT↗