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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Hubble Space Telescope-Space Shuttle interface dynamic verification test

A test program has been developed for the interface between the Space Shuttle Orbiter and the Hubble Space Telescope which couples a standard modal test for a simple suspended structure with a novel, 'interface verification' test. While the free-free modal test is used to verify the high loads generating structural modes due to the interaction of internal components of the structure with the rest of the structure, the interface verification test verifies the character of the high-loading generating modes in which the structure reacts against the booster interface. The novel method excites the structure at a single payload-booster interface DOF, while all other interfaces are left free to move.

Blair, Mark A.↗
NASA NTRSDate not supplied

Flight Performance Estimates for the NASA X-57 Distributed Electric Propulsion Flight Demonstrator

The X-57 flight demonstrator concept featured four configurations starting with a conventional combustion-powered multiengine airplane and ending with a fully electric configuration with two forms of distributed propulsion and a highly modified wing. These configurations, called Mods, were designed to gain incremental insight into different aircraft propulsion configuration options and their impact on the aircraft performance. The gasoline-powered Mod I configuration consumed 2.6 to 2.9 times more stored energy in cruise than the electric but otherwise conventionally configured Mod II configuration. The highly loaded wing of Mod III led to an increase of 40% in the power-off lift-to-drag ratio as compared to Mod II at the project high-speed cruise target speed and altitude. The power-on lift-to-drag ratio of Mod III was 53% higher than Mod II due to the beneficial aero-propulsive interaction of the wingtip-mounted cruise propellers in Mod III. The high-lift propeller system of Mod IV recovered the low-speed performance of the conventional configuration in Mod II that was otherwise lost with the introduction of the highly loaded Mod III wing. The battery-electric configurations also benefitted from a lack of power lapse in the electric motors with increasing air density as compared to the combustion-powered baseline aircraft.

Distributed Performance↗
NASA NTRSDate not supplied

Flight Performance Estimates for the NASA X-57 Distributed Electric Propulsion Flight Demonstrator

The X-57 flight demonstrator concept featured four configurations starting with a conventional combustion-powered multiengine airplane and ending with a fully electric configuration with two forms of distributed propulsion and a highly modified wing. These configurations, called Mods, were designed to gain incremental insight into different aircraft propulsion configuration options and their impact on the aircraft performance. The gasoline-powered Mod I configuration consumed 2.6 to 2.9 times more stored energy in cruise than the electric but otherwise conventionally configured Mod II configuration. The highly loaded wing of Mod III led to an increase of 40% in the power-off lift-to-drag ratio as compared to Mod II at the project high-speed cruise target speed and altitude. The power-on lift-to-drag ratio of Mod III was 53% higher than Mod II due to the beneficial aero-propulsive interaction of the wingtip-mounted cruise propellers in Mod III. The high-lift propeller system of Mod IV recovered the low-speed performance of the conventional configuration in Mod II that was otherwise lost with the introduction of the highly loaded Mod III wing. The battery-electric configurations also benefitted from a lack of power lapse in the electric motors with increasing air density as compared to the combustion-powered baseline aircraft.

Distributed Performance↗
NASA NTRS1992

Aeroloads and secondary flows in a transonic mixed flow turbine stage

A numerical simulation of a transonic mixed flow turbine stage has been carried out using an average passage Navier-Stokes analysis. The mixed flow turbine stage considered here consists of a transonic nozzle vane and a highly loaded rotor. The simulation was run at the design pressure ratio and is assessed by comparing results with those of an established throughflow design system. The three-dimensional aerodynamic loads are studied as well as the development and migration of secondary flows and their contribution to the total pressure loss. The numerical results indicate that strong passage vortices develop in the nozzle vane, mix out quickly, and have little impact on the rotor flow. The rotor is highly loaded near the leading edge. Within the rotor passage, strong spanwise flows and other secondary flows exist along with the tip leakage vortex. The rotor exit loss distribution is similar in character to that found in radial inflow turbines. The secondary flows and non-uniform work extraction also tend to significantly redistribute a non-uniform inlet total temperature profile by the exit of the stage.

Kirtley, K. R.↗
NASA NTRS2021

A Dark Target research aerosol algorithm for MODIS observations over eastern China: increasing coverage while maintaining accuracy at high aerosol loading

Satellite aerosol products such as the Dark Target (DT) produced from the MODerate resolution Imaging Spectroradiometer (MODIS) are useful for monitoring the progress of air pollution. Unfortunately, the DT often fails to retrieve during the heaviest aerosol events as well as the more moderate events in winter. Some of the literature at-tributes this lack of retrieval to the cloud mask. However, we found this lack of retrieval is mainly traced to thresholds used for masking of inland water and snow. Modifications to these two masks greatly increase 50 % of the retrievals of aerosol optical depth at 0.55 μm (AOD) greater than 1.0. The “extra”-high-AOD retrievals tend to be biased when com-pared with a ground-based sun photometer (AErosol RObotic NETwork, AERONET). Reducing bias in new retrievals re-quires two additional steps. One is an update to the assumed aerosol optical properties (aerosol model); the haze in this region is both less absorbing and lower in altitude than what is assumed in the global algorithm. The second is account-ing for the scale height of the aerosol, specifically that the heavy-aerosol events in the region are much closer to the surface than what is assumed by the global DT algorithm. The resulting combination of modified masking thresholds, new aerosol model, and lower aerosol layer scale height was applied to 3 months of MODIS observations (January–March2013) over eastern China. After these two additional steps are implemented, the significant increase in new retrievals introduces no overall bias at a high-AOD regime but does degrade other overall validation statistics. We also find that the research algorithm is able to identify additional pollution events that AERONET instruments may not due to different spatial sampling. Mean AOD retrieved from the re-search algorithm increases from 0.11 to 0.18 compared to values calculated from the operational DT algorithm during January to March of 2013 over the study area. But near Beijing, where the severe pollution occurs, the new algorithm increases AOD by as much as 3.0 for each 0.5°grid box over the previous operational-algorithm values.

Dark Target↗
NASA NTRS1977

Ultra high tip speed (670.6 m/sec) fan stage with composite rotor: Aerodynamic and mechanical design

A highly loaded, single-stage compressor having a tip speed of 670.6 m/sec was designed for the purpose of investigating very high tip speeds and high aerodynamic loadings to obtain high stage pressure ratios at acceptable levels of efficiency. The design pressure ratio is 2.8 at an adiabatic efficiency of 84.4%. Corrected design flow is 83.4 kg/sec; corrected design speed is 15,200 rpm; and rotor inlet tip diameter is 0.853 m. The rotor uses multiple-circular-arc airfoils from 0 to 15% span, precompression airfoils assuming single, strong oblique shocks from 21 to 43% span, and precompression airfoils assuming multiple oblique shocks from 52% span to the tip. Because of the high tip speeds, the rotor blades are designed to be fabricated of composite materials. Two composite materials were investigated: Courtaulds HTS graphite fiber in a Kerimid 601 polyimide matrix and the same fibers in a PMR polyimide matrix. In addition to providing a description of the aerodynamic and mechanical design of the 670.0 m/sec fan, discussion is presented of the results of structural tests of blades fabricated with both types of matrices.

Halle, J. E.↗
NASA NTRS1989

The measurement of boundary layers on a compressor blade in cascade. Volume 1: Experimental technique, analysis and results

Measurements were made of the boundary layers and wakes about a highly loaded, double-circular-arc compressor blade in cascade. These laser Doppler velocimetry measurements have yielded a very detailed and precise data base with which to test the application of viscous computational codes to turbomachinery. In order to test the computational codes at off-design conditions, the data were acquired at a chord Reynolds number of 500,000 and at three incidence angles. Moreover, these measurements have supplied some physical insight into these very complex flows. Although some natural transition is evident, laminar boundary layers usually detach and subsequently reattach as either fully or intermittently turbulent boundary layers. These transitional separation bubbles play an important role in the development of most of the boundary layers and wakes measured in this cascade and the modeling or computing of these bubbles should prove to be the key aspect in computing the entire cascade flow field. In addition, the nonequilibrium turbulent boundary layers on these highly loaded blades always have some region of separation near the trailing edge of the suction surface. These separated flows, as well as the subsequent near wakes, show no similarity and should prove to be a challenging test for the viscous computational codes.

Zierke, William C.↗
NASA NTRS1997

Small Engine Technology. Task 4: Advanced Small Turboshaft Compressor (ASTC) Performance and Range Investigation

This contact had two main objectives involving both numerical and experimental investigations of a small highly loaded two-stage axial compressor designated Advanced Small Turboshaft Compressor (ASTC) winch had a design pressure ratio goal of 5:1 at a flowrate of 10.53 lbm/s. The first objective was to conduct 3-D Navier Stokes multistage analyses of the ASTC using several different flow modelling schemes. The second main objective was to complete a numerical/experimental investigation into stall range enhancement of the ASTC. This compressor was designed wider a cooperative Space Act Agreement and all testing was completed at NASA Lewis Research Center. For the multistage analyses, four different flow model schemes were used, namely: (1) steady-state ADPAC analysis, (2) unsteady ADPAC analysis, (3) steady-state APNASA analysis, and (4) steady state OCOM3D analysis. The results of all the predictions were compared to the experimental data. The steady-state ADPAC and APNASA codes predicted similar overall performance and produced good agreement with data, however the blade row performance and flowfield details were quite different. In general, it can be concluded that the APNASA average-passage code does a better job of predicting the performance and flowfield details of the highly loaded ASTC compressor.

Hansen, Jeff L.↗
NASA NTRS2019

Structural Analysis and Performance-Based Validation of a Composite Wing Spar

Electric-motor powered aircraft possess the ability to operate with efficient energy delivery, but lack the operational range of internal combustion engine powered aircraft. This range limitation requires the use of high aspect ratio, thin-chord wings to minimize aerodynamic drag losses, which results in highly loaded composite spar structures. High aspect ratio wings are required to increase mission durations for a NASA-developed experimental multi-rotor electric powered aircraft denoted as the Scalable Convergent Electric Propulsion Technology and Operations Research (SCEPTOR) or “X-57”. This paper examines the structural performance of the composite main wing spars to validate spar strength using ply-based laminate finite element methods. Geometric scaling of a main spar test-section was initially proposed for proof-testing but sacrificed stability. Ply-based structures modeling with local structural features was implemented as a risk-reduction methodology. Ply-based modeling was selected to augment the conventional “building block” approach to reduce risk, and leverage a “performance-based” approval processes encouraged in Federal Aviation Administration (FAA) design guidance. Therefore, ply-based laminate modeling of the full-scale main spar and forward spar shear-web attachments were subsequently undertaken to determine load path complexity with predicted flight loads. Ply-based modeling included stress concentrations and interlaminate behavior at interface locations that can be obscured in traditional finite element sizing models. Analysis of the wing spar laminate ply-based models compared with bearing test coupon performance was used to reduce future wing assembly proof-testing burden and facilitate performance-based flight hardware safety for the X-57 experimental aircraft.

Moore, James B.↗
NASA NTRS1967

Temperature responsive valve withstands high impact loading

Valve regulates the flow of a reactant to a chemical heater used in a space application and withstands extreme impact loading. The valve has an upper and a lower housing, the lower containing an inlet and an outlet port, and upper containing a cavity.

Gram, M. B.↗
NASA NTRS1973

Hingeless rotor vibration and loads at high advance ratio

Experimental values of mean and oscillatory shaft force aeroelastic derivatives with respect to cyclic pitch are presented in dimensionless coefficient form for stiff-bladed hingeless rotors operating at high advance ratio. Good agreement with theory is obtained for the 2P components, in rotating axes, of the oscillatory hub moment derivatives. Trends were predicted for the mean components. Experimental plots of the azimuthal distribution of blade flap bending moment due to cyclic pitch are compared with theoretical for high values of flap frequency ratio and advance ratio. Good agreement is found near the blade root. The similarity parameters that should be preserved in the scale model testing of stiff-bladed hingeless rotors at high advance ratio are reviewed, and some aspects of hingeless rotor wind tunnel testing are considered.

Watts, G. A.↗
NASA NTRS1978

Step motor damping for high-inertia loads

Brushless tachometer generates signals for moving large and varying loads precisely. Stepper waveform generator sends short sequence of pulses to instruct control logic circuit to perform its function-that is, to select proper windings and directions of excitation to drive and damp motor. Control logic circuit bases decisions on following logic signals, derived from tachometer: rate direction, rate threshold, and position.

Veillette, L. J.↗
NASA NTRS1980

Electronic system for high power load control

Parallel current paths are divided into two groups, with control devices in the current paths of one group each having a current limiting resistor, and the control devices in the other group each having no limiting resistor, so that when the control devices of the second group are turned fully on, a short circuit is achieved by the arrangement of parallel current paths. Separate but coordinated control signals are provided to turn on the control devices of the first group and increase their conduction toward saturation as a function of control input, and when fully on, or shortly before, to turn on the control devices of the second group and increase their conduction toward saturation as a function of the control input as that input continues to increase. Electronic means may be used to generate signals. The system may be used for 1-V characteristic measurements of solar arrays as well as for other load control purposes.

Miller, E. L.↗