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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Effects of a gravity gradient on human cardiovascular responses

Eight subjects participated in one control and three rotation trials on a short-arm centrifuge such that the Gz levels at the feet were 0.5, 1.0, and 1.5 G. Trials consisted of 30 minutes of supine rest, 1 hour of rotation (or in the control, 30 additional minutes of rest and 30 minutes of standing), and a final 30-minute rest period. Measurements of heart rate, calf impedance, calf volume, and blood pressure support the findings that the highest G level is similar to standing and that the lower G levels fail to produce significant effects.

NASA Discipline Cardiopulmonary↗
NASA NTRS1998

Development of a Rotor-Body Coupled Analysis for an Active Mount Aeroelastic Rotor Testbed

At the Langley Research Center an active mount rotorcraft testbed is being developed for use in the Langley Transonic Dynamics Tunnel. This testbed, the second generation version of the Aeroelastic Rotor Experimental System (ARES-II), can impose rotor hub motions and measure the response so that rotor-body coupling phenomena may be investigated. An analytical method for coupling an aeroelastically scaled model rotor system to the ARES-II is developed in the current study. Models of the testbed and the rotor system are developed in independent analyses, and an impedance-matching approach is used to couple the rotor system to the testbed. The development of the analytical models and the coupling method is examined, and individual and coupled results are presented for the testbed and rotor system. Coupled results are presented with and without applied hub motion, and system loads and displacements are examined. The results show that a closed-loop control system is necessary to achieve desired hub motions, that proper modeling requires including the loads at the rotor hub and rotor control system, and that the strain-gauge balance placed in the rotating system of the ARES-II provided the best loads results.

Wilbur, Matthew L.↗
NASA NTRS2007

High-Temperature Characterization of Alumina Substrates and Folded Slot Antenna

The characterization of 99.6% polycrystalline alumina substrates and folded slot antennas is presented in this paper. Coplanar Waveguide (CPW) calibration standards where fabricated on 99.6% polycrystalline alumina substrates. Thru-Reflect-Line (TRL) calibrations were performed at temperatures of 25 to 400 C over a frequency range from 0.5 to 50 GHz. The effective dielectric constant of the alumina substrates was determined to be relatively constant at 5.4 from 25 to 200 C and then increased steadily to approximately 6 at 400 C. The loss of the CPW lines increased as temperature and frequency increased as well noting that the increase in loss is even more profound as both the temperature and frequency increased simultaneously. A CPW fed folded slot antenna fabricated on the alumina substrates is also presented. The Return Loss (RL) of a CPW fed folded slot antenna exhibits a self impedance matching technique. The RL of the folded slot antenna at 25 C displays a resonance at 3.5 GHz and is approximately 16 dB in magnitude. At 300 C the resonance shifts down in frequency to approximately 3.3 dB and has roughly the same magnitude. However the loss of the antenna response also increases at this elevated temperature. This work is part of the initial stages of an effort at NASA Glenn research Center to develop wireless sensors for harsh environments. This work can reduce cost, space to house all the hard wired connections, and reduce the weight of the overall units such as aerospace engines and allow for the placement of the wireless sensors in the engine which are not possible with hard wired sensors.

Scardelletti, Maximilian C.↗
NASA NTRS1989

Acoustic radiation from a shell with internal structures

A method is developed to compute frequency response and acoustic radiation of a complex shell. The axisymmetric geometry of the shell includes cylindrical, conical, and spherical segments stiffened by discrete rings and bulkheads. The shell is coupled to internal masses and elastic frames. Shell segments are treated by transfer matrices. Rings, bulkheads, frames, and concentrated masses are treated by impedances at junctions of segments. The shell is coupled to an external acoustic fluid treated by Green's function and curved surface elements. A major issue facing the method's treatment of the fluid would be lack of existence or uniqueness encountered in the uncoupled, external acoustic problem at characteristic wavenumbers. By using a simple spherical shell, without internal structures, this potential hindrance is shown not to arise. A fuller application of the method awaits subsequent results.

El-Raheb, M.↗
NASA NTRS2016

Acute Effects of Simulated Space Radiation and Micro-Gravity on Cancellous Bone Loss in Mice Tibiae

Space radiation and micro-gravity are the two major obstacles impeding human exploration of Mars and beyond. Long-duration space flights expose astronauts to high doses of high linear energy transfer (LET) radiation as well as prolonged periods of skeletal disuse due to weightlessness. One important consequence of both radiation exposure and micro-gravity is acute bone loss. However, biological responses to different radiation types and combined radiation and micro-gravity environments remain unknown. Thus, the purpose of this study is to compare the acute effects of different radiation species and simulated weightlessness on bone degeneration for the purpose of developing accurate risk assessments of prolonged space flight. Mouse models were used to simulate space flight-relevant doses of different radiation types as well as weightlessness via hind-limb unloading. Three groups of mice (n 9) were irradiated with 1 Gy (Gray) H+, 1 Gy 56Fe, and 1 Gy combined H+ and 56Fe (dual ion) respectively and compared to sham irradiated (n 9) and 2 Gy 56Fe irradiated positive controls (n 6). Two groups of mice (n 9) were hind-limb unloaded for three days and then either sham irradiated or dual ion irradiated respectively, followed by subsequent hind-limb unloading for 11 days. Cancellous tissue from tibiae metaphyses were harvested 11 days post-irradiation for ex vivo micro-computed tomography analysis. Microarchitecture parameters including bone volume to total volume ratio (BVTV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular spacing (Tb.S), and connectivity density (Conn.D) will be quantified using a novel automated segmentation procedure developed in our lab. The anticipated results will be instrumental in developing counter-measures against micro-gravity and radiation-induced bone loss. Moreover, possible synergistic effects may provide insight into underlying mechanisms mediating biological response.

Micro-Gravity↗
NASA NTRSDate not supplied

Control and Scaling Approach for the Emulation of Dynamic Subscale Torque Loads

Research and development of electrified aircraft propulsion powertrains is moving toward the use electro-mechanical systems to emulate the loads a system imparts on another. Replacing a prime mover with a model driving an electro-mechanical system capable of emulating loads that regulate the system to produce a desired response is a lower risk, lower cost alternative to using the traditional prime mover for control system verification. This paper outlines a control and scaling approach for emulating scaled dynamic torque loads using electric machine (EM) hardware for electrified aircraft propulsion research and development purposes. The approach, known as the Sliding Mode Impedance Controller with Scaling (SMICS), drives a mechanically coupled two-EM system that provides a scaled hardware representation of an electrified turbomachinery shaft. One EM reflects inertial dynamics and load of the shaft under steady-state and transient operation while the second EM represents a motor/generator connected to the shaft. This closed loop system applies impedance and sliding mode control schemes to match desired dynamics in real-time along with parameter scaling to effectively scale full scale torque inputs, a full-scale desired inertia, and sub-scale speed feedback. The result is a sub-scale hardware implementation of a coupled EM system that is command-able by a model and control system designed for a full-scale electrified aircraft propulsion powertrain. The paper elaborates on the need for closed loop control and scaling as well as impedance and sliding mode control theory, shows a derivation of the controller and scaling, its implementation, and presents a comparison of theoretical and actual simulation results acquired during hardware-in-the-loop testing of a partial turboelectric propulsion concept at the NASA Electric Aircraft Testbed (NEAT).

Santino J Bianco↗
NASA NTRS1972

High sensitivity infrared 10.6 micrometer heterodyne receiver development

The results are presented for a study on the design of an infrared 10.6-micrometer quantum-noise-limited optical receiver subsystem. Performance measurements of the HgCdTe photomixer preamplifier combination were carried out for photomixer temperatures up to 152 K and a photomixer frequency response of up to 420 MHz was obtained. Results of temperature and bias cycling of HgCdTe photomixers are reported. Design considerations for an operational 10.6 micrometer heterodyne receiver are presented. These consist of design data on required laser LO illumination, heat load levels for photomixer cooler, photomixer uniformity and the effects of photomixer impedance match on receiver sensitivity. Analysis and measurements of 10.6 micrometer heterodyne detection in an extrinsic photoconductive (p-type) HgCdTe photomixer are also presented.

Source record↗
NASA NTRS2017

Methodology for Time-Domain Estimation of Storm Time Geoelectric Fields Using the 3-D Magnetotelluric Response Tensors

Geoelectric fields at the Earth's surface caused by magnetic storms constitute a hazard to the operation of electric power grids and related infrastructure. The ability to estimate these geoelectric fields in close to real time and provide local predictions would better equip the industry to mitigate negative impacts on their operations. Here we report progress toward this goal: development of robust algorithms that convolve a magnetic storm time series with a frequency domain impedance for a realistic three-dimensional (3-D) Earth, to estimate the local, storm time geoelectric field. Both frequency domain and time domain approaches are presented and validated against storm time geoelectric field data measured in Japan. The methods are then compared in the context of a real-time application.

Kelbert, Anna↗
NASA NTRS2020

AD8065 Voltage Feedback Amplifier’s Total Ionizing Dose Characterization Report

The purpose of this testing was to characterize Analog Devices’ AD8065 FastFET amplifier for low-dose rate (LDR) total ionizing dose (TID) response based on the Lucy project requirements and will be used on the L’ORRI instrument being built by Johns Hopkins University Applied Physics Lab. The AD8065 is a voltage feedback amplifier with FET inputs developed with the proprietary eXtra Fast Complementary Bipolar (XFCB) process. The amplifier boasts low noise operation and very high input impedance with a wide supply voltage range.

Megan Casey↗
NASA NTRS1982

Generation of desired signals from acoustic drivers

A procedure to control transient signal generation is developed for the study of internal noise propagation from aircraft engines. A simple algorithm incorporating transform techniques is used to produce signals of any desired waveform from acoustic drivers. The accurate driver response is then calculated, and from this the limiting frequency characteristics are determined and the undesirable frequencies where the driver response is poor are eliminated from the analysis. A synthesized signal is then produced by convolving the inverse of the response function with the desired signal. Although the shape of the synthesized signal is in general quite awkward, the driver generates the desired signal when the distorted signal is fed into the driver. The results of operating the driver in two environments, in a free field and in a duct, are presented in order to show the impedance matching effect of the driver. In addition, results using a high frequency cut-off value as a parameter is presented in order to demonstrate the extent of the applicability of the synthesis procedure. It is concluded that the desired signals can be generated through the signal synthesis procedure.

Ramakrishnan, R.↗
NASA NTRSDate not supplied

Challenges Associated with In-Situ Calibration of Load Cells in Force Limited Vibration Testing

The difference in mounting configuration between flight and test can significantly impact the effectiveness of the test in environmental vibration testing. Many tests are performed with large electrodynamic shakers, which utilize interfaces that seek to replicate a fixed base, such as slip tables and head expanders. This fixed base configuration is rarely seen in flight configurations; rather a more realistic configuration would include a flexible mounting structure with its own compliance and dynamics. This causes significant over and under tests in various frequency bands depending on the differences between the test article and fixture dynamics. The traditional way of avoiding these high loads is to limit the acceleration responses at multiple locations on the test article. However, the effectiveness of this approach is highly dependent upon the validity of the test article’s analytical in order to derive accurate acceleration response limit specifications. Also this technique requires limiting the acceleration responses at many locations throughout the test article, which may not be implementable due to such things as access and cleanliness issues An improved environmental vibration testing technique known as force limiting incorporates measurements of the forces between the test article and shaker system interface and limiting them to a specification that more accurately replicates the interface impedance of the structure the test article will be mounted to in flight. In effect this transforms the high mechanical impedance at the test article to shaker interface to more closely match the mechanical impedance of the flight interface, which avoids producing the unrealistically high interface loads. Typically force gauges or load cells are used to measure these interface forces. However, utilizing load cells can present a multitude of challenges depending upon such things as their installation method, geometric layout, and test fixture setup. Regardless, it is extremely important to perform an in-situ calibration of the load cells prior to vibration testing at any significant levels. This paper will discuss the challenges associated with utilizing load cells during the NASA Evolutionary Xenon Thruster – Commercial (NEXT-C) gridded ion thruster proto-flight vibration test performed at the NASA Glenn Research Center’s Structural Dynamics Laboratory.

Kenneth J Pederson↗
NASA NTRSDate not supplied

Challenges Associated with In-Situ Calibration of Load Cells in Force Limited Vibration Testing

The difference in mounting configuration between flight and test can significantly impact the effectiveness of the test in environmental vibration testing. Many tests are performed with large electrodynamic shakers, which utilize interfaces that seek to replicate a fixed base, such as slip tables and head expanders. This fixed base configuration is rarely seen in flight configurations; rather a more realistic configuration would include a flexible mounting structure with its own compliance and dynamics. This causes significant over and under tests in various frequency bands depending on the differences between the test article and fixture dynamics. The traditional way of avoiding these high loads is to limit the acceleration responses at multiple locations on the test article. However, the effectiveness of this approach is highly dependent upon the validity of the test article’s analytical in order to derive accurate acceleration response limit specifications. Also this technique requires limiting the acceleration responses at many locations throughout the test article, which may not be implementable due to such things as access and cleanliness issues An improved environmental vibration testing technique known as force limiting incorporates measurements of the forces between the test article and shaker system interface and limiting them to a specification that more accurately replicates the interface impedance of the structure the test article will be mounted to in flight. In effect this transforms the high mechanical impedance at the test article to shaker interface to more closely match the mechanical impedance of the flight interface, which avoids producing the unrealistically high interface loads. Typically force gauges or load cells are used to measure these interface forces. However, utilizing load cells can present a multitude of challenges depending upon such things as their installation method, geometric layout, and test fixture setup. Regardless, it is extremely important to perform an in-situ calibration of the load cells prior to vibration testing at any significant levels. This paper will discuss the challenges associated with utilizing load cells during the NASA Evolutionary Xenon Thruster – Commercial (NEXT-C) gridded ion thruster proto-flight vibration test performed at the NASA Glenn Research Center’s Structural Dynamics Laboratory.

K. J. Pederson↗
NASA NTRS1990

Analysis and design of a high power, digitally-controlled spacecraft power system

The progress to date on the analysis and design of a high power, digitally controlled spacecraft power system is described. Several battery discharger topologies were compared for use in the space platform application. Updated information has been provided on the battery voltage specification. Initially it was thought to be in the 30 to 40 V range. It is now specified to be 53 V to 84 V. This eliminated the tapped-boost and the current-fed auto-transformer converters from consideration. After consultations with NASA, it was decided to trade-off the following topologies: (1) boost converter; (2) multi-module, multi-phase boost converter; and (3) voltage-fed push-pull with auto-transformer. A non-linear design optimization software tool was employed to facilitate an objective comparison. Non-linear design optimization insures that the best design of each topology is compared. The results indicate that a four-module, boost converter with each module operating 90 degrees out of phase is the optimum converter for the space platform. Large-signal and small-signal models were generated for the shunt, charger, discharger, battery, and the mode controller. The models were first tested individually according to the space platform power system specifications supplied by NASA. The effect of battery voltage imbalance on parallel dischargers was investigated with respect to dc and small-signal responses. Similarly, the effects of paralleling dischargers and chargers were also investigated. A solar array and shunt model was included in these simulations. A model for the bus mode controller (power control unit) was also developed to interface the Orbital replacement Unit (ORU) model to the platform power system. Small signal models were used to generate the bus impedance plots in the various operating modes. The large signal models were integrated into a system model, and time domain simulations were performed to verify bus regulation during mode transitions. Some changes have subsequently been incorporated into the models. The changes include the use of a four module boost discharger, and a new model for the mode controller, which includes the effects of saturation. The new simulations for the boost discharger show the improvement in bus ripple that can be achieved by phase-shifted operation of each of the boost modules.

Lee, F. C.↗
NASA NTRS2014

NASA Tech Briefs, January 2014

Topics include: Multi-Source Autonomous Response for Targeting and Monitoring of Volcanic Activity; Software Suite to Support In-Flight Characterization of Remote Sensing Systems; Visual Image Sensor Organ Replacement; Ultra-Wideband, Dual-Polarized, Beam-Steering P-Band Array Antenna; Centering a DDR Strobe in the Middle of a Data Packet; Using a Commercial Ethernet PHY Device in a Radiation Environment; Submerged AUV Charging Station; Habitat Demonstration Unit (HDU) Vertical Cylinder Habitat; Origami-Inspired Folding of Thick, Rigid Panels; A Novel Protocol for Decoating and Permeabilizing Bacterial Spores for Epifluorescent Microscopy; Method and Apparatus for Automated Isolation of Nucleic Acids from Small Cell Samples; Enabling Microliquid Chromatography by Microbead Packing of Microchannels; On-Command Force and Torque Impeding Devices (OC-FTID) Using ERF; Deployable Fresnel Rings; Transition-Edge Hot-Electron Microbolometers for Millimeter and Submillimeter Astrophysics; Spacecraft Trajectory Analysis and Mission Planning Simulation (STAMPS) Software; Cross Support Transfer Service (CSTS) Framework Library; Arbitrary Shape Deformation in CFD Design; Range Safety Flight Elevation Limit Calculation Software; Frequency-Modulated, Continuous-Wave Laser Ranging Using Photon-Counting Detectors; Calculation of Operations Efficiency Factors for Mars Surface Missions; GPU Lossless Hyperspectral Data Compression System; Robust, Optimal Subsonic Airfoil Shapes; Protograph-Based Raptor-Like Codes; Fuzzy Neuron: Method and Hardware Realization; Kalman Filter Input Processor for Boresight Calibration; Organizing Compression of Hyperspectral Imagery to Allow Efficient Parallel Decompression; and Temperature Dependences of Mechanisms Responsible for the Water-Vapor Continuum Absorption.

Source record↗
NASA NTRS1993

Cerebral blood velocity and other cardiovascular responses to 2 days of head-down tilt

Spaceflight induces a cephalad redistribution of fluid volume and blood flow within the human body, and space motion sickness, which is a problem during the first few days of space flight, could be related to these changes in fluid status and in blood flow of the cerebrum and vestibular system. To evaluate possible changes in cerebral blood flow during simulated weightlessness, we measured blood velocity in the middle cerebral artery (MCA) along with retinal vascular diameters, intraocular pressure, impedance cardiography, and sphygmomanometry on nine men (26.2 +/- 6.6 yr) morning and evening for 2 days during continuous 10 deg head-down tilt (HDT). When subjects went from seated to head-down bed rest, their heart rate and retinal diameters decreased, and intraocular pressures increased. After 48 h of HDT, blood flow velocity in the MCA was decreased and thoracic impedance was increased, indicating less fluid in the thorax. Percent changes in blood flow velocities in the MCA after 48 h of HDT were inversely correlated with percent changes in retinal vascular diameters. Blood flow velocities in the MCA were inversely correlated (intersubject) with arterial pressures and retinal vascular diameters. Heart rate, stroke volume, cardiac output, systolic arterial pressure, and at times pulse pressure and blood flow velocities in the MCA were greater in the evening. Total peripheral resistance was higher in the morning. Although cerebral blood velocity is reduced after subjects are head down for 2 days, the inverse relationship with retinal vessel diameters, which have control analogous to that of cerebral vessels, indicates cerebral blood flow is not reduced.

Frey, Mary A. B.↗
NASA NTRS1994

Hemodynamic Responses to Head and Neck Cooling

Personal thermoregulatory systems which provide head and neck cooling are used in the industrial and aerospace environments to alleviate thermal stress. However, little information is available regarding the physiologic and circulatory changes produced by routine operation of these systems. The objective of this study was to measure the scalp temperature and circulatory responses during use of one commercially available thermal control system. The Life Support Systems, Inc. Mark VII portable cooling system and a liquid cooling helmet were used in this study. Two EEG electrodes and one skin temperature transducer were placed on the anterior midline of the scalp to measure the scalp blood and temperature. Blood flow was measured using a bipolar impedance rheograph. Ten subjects, seated in an upright position at normal room temperature, were tested at high, medium, moderate, moderate-low and low coolant temperatures. Scalp blood flow was recorded continuously using a computer data acquisition system with a sampling frequency of 200 Hz. Scalp temperature and cooling helmet Inlet temperature was logged periodically during the test period. This study quantifies the effect of head cooling upon scalp temperature and blood flow. These data may also be used to select operational specifications of the head cooling system for biomedical applications such as the treatment of migraine headaches, scalp cooling during chemotherapy, and cooling of multiple sclerosis patients.

Ku, Yu-Tsuan E.↗
NASA NTRS1965

Digital Distributed Parameter Model for Analysis of Unsteady Flow in Liquid-Filled Lines

A distributed parameter model for computing unsteady flow conditions in liquid systems is presented. The model is adapted for use in conjunction with a digital computer. The analytical method employed is essentially a solution synthesized from the effects of incremental step pressure pulses. The pressure pulses are generated because of incremental flow-rate changes that originate in a fluid system from a variety of sources, including the mechanical motion of the system structure. The pressure pulses propagate throughout the system at sonic velocity and are partially transmitted and reflected at each discontinuity. The velocity change caused by each pressure pulse is obtained from the relation for the characteristic acoustic impedance. Pressure and velocity time histories at any point in the system are obtained by a timewise summation of the contributions of the incremental pressure pulses passing that point. The analysis is presented in a form general enough to be applied to a variety of liquid-filled fluid systems. To illustrate the application of the method to a specific system, the response of a long, straight propellant line to a sinusoidal inlet flow and pressure perturbation is computed. Both a constant-cross-section line and a tapered line are analyzed in the example.

UNSTEADY FLOW↗
NASA NTRS1989

Thunderstorm related variations in stratospheric conductivity measurements

The vector electric field and polar conductivities were measured by zero-pressure balloon-borne payloads launched from Wallops Island, Virgina during the summers of 1987 and 1988. Data were collected over thunderstorms (or electrified clouds) during 6-hour flights at altitudes near 30 km. The vector electric field measurements were made with the double Langmuir probe high-impedance method, and the direct conductivity measurements were obtained with the relaxation technique. Evidence is presented for conductivity variations over thunderstorms (or electrified clouds). It is found that both positive and negative polar conductivity data do show variations of up to a factor of 2 from ambient values associated with the disturbed periods. Some ideas for possible physical mechanisms which may be responsible for the conductivity variations over thunderstorms are also discussed in this paper.

Hu, Hua↗