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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 NTRS1979

Characteristics of primary electric propulsion systems

The use of advanced electric propulsion systems will provide cost and performance benefits for future energetic space missions. A methodology to predict the characteristics of advanced electric propulsion systems was developed and programmed for computer calculations to allow evaluation of a broad set of technology and mission assumptions. The impact on overall thrust system characteristics was assessed for variations of propellant type, total accelerating voltage, thruster area, specific impulse, and power system approach. The data may be used both to provide direction to technology emphasis and allow for preliminary estimates of electric propulsion system properties for a wide variety of application.

Byers, D. C.↗
NASA NTRS2009

A Simple Sensor Model for THUNDER Actuators

A quasi-static (low frequency) model is developed for THUNDER actuators configured as displacement sensors based on a simple Raleigh-Ritz technique. This model is used to calculate charge as a function of displacement. Using this and the calculated capacitance, voltage vs. displacement and voltage vs. electrical load curves are generated and compared with measurements. It is shown this model gives acceptable results and is useful for determining rough estimates of sensor output for various loads, laminate configurations and thicknesses.

Campbell, Joel F.↗
NASA NTRS1981

Thrust and efficiency of a self-field MPD thruster

Thrust and efficiency of a quasi-steady multi-MW argon MPD thruster are determined for one-millisecond current pulses. Terminal voltage and impulse bit per pulse are measured for a benchmark thruster geometry on a swinging gate thrust stand in a dielectric vacuum tank, at a background pressure of 0.0001 torr, for a range of argon flow rates and arc currents. The quasi-steady thrust data scale quadratically with arc current, and confirm previous estimates of the electromagnetic and electrothermal components of thrust from magnetic and pressure probe measurements. Thruster efficiency is found to increase monotonically with specific impulse, reaching a value of 25% for 4.5 to 6.0 g/sec at 2000 seconds. Results of further experiments show that the inferred specific impulse for voltage fluctuation onset can be increased to 3000 seconds, and the thrust efficiency to above 30%.

Burton, R. L.↗
NASA NTRSDate not supplied

Materials for Power Transmission in Extreme Environments

NASA’s goal for a sustained human presence on the Moon and a future Lunar economy requires the development of novel power transmission materials for extreme environments. As an increasing number of public and private entities set their sights towards a future on the Moon, the demand for surface power will dramatically increase – potentially up to megawatt levels. A Lunar economy is envisioned to include a human habitat, manned and unmanned science exploration assets, excavation rovers and systems, and large-scale infrastructure construction such as solar arrays and power grids. A NASA trade study estimated that 1 to 3 km of power transmission lines (1 to 3 KV ac and dc) will be needed over time. Current high power and voltage SOA cables/wire can easily exceed 1 kg/m where mass is not as critical. Connectors, deployment spools and robots further increase the subsystem mass significantly increasing costs. On the other hand, advances in aeronautics provides path towards space missions. The operating environment on the Moon presents substantial risk to safe and reliable power transmission due to space weathering and degradation. These challenges include cosmic and UV radiation, extreme temperatures swings, the electrostatic Lunar exosphere, and the electrostatic and abrasive lunar regolith. The critical need for lightweight, safe and reliable power cables/wires materials is evident. In this presentation, the extreme high altitude and lunar environments and recent materials development from NASA Glenn Research Center’s High Voltage Materials team towards meeting NASA’s objectives and goals for aeronautics and space missions.

Cu/CNT conductors↗
NASA NTRS1979

Current leakage for low altitude satellites

Ionospheric plasma densities exceeding 1,000,000 per cu cm exist around satellites in low earth orbit. Operation of large solar arrays at high voltage may drive substantial leakage currents through this surrounding plasma. Power losses exceeding solar cell output have been observed for small arrays biased above +2,000 V. Estimates of these effects for very large power systems are developed. Recent large scale (10 meter) lab tests are reported. Estimates based on calculations of space charge limited sheath dimensions are identified as a good working model, leading to projected power losses for large arrays increasing much more slowly than for small arrays.

Mccoy, J. E.↗
NASA NTRS2008

Assessments of Hollow Cathode Wear in the Xenon Ion Propulsion System (XIPs(c)) by Numerical Analyses and Wear Tests

The standard approach presently followed by NASA to qualify electric propulsion for the required mission throughput has been based largely on life tests, which can be costly and time consuming. Revised electric propulsion lifequalification approaches are being formulated that combine analytical and/or computational methods with (shorter-duration) wear tests. As a model case, a wear test is being performed at JPL to assess the lifetime of the discharge hollow cathode in the Xenon Ion Propulsion System (XIPS(c)), a 25-cm ion engine developed by L-3 Communications Electron Technologies, Inc. for commercial applications. Wear and plasma data accumulated throughout this life-assessment program are being used to validate the existing 2-D hollow cathode code OrCa2D. We find that the OrCa2D steady-state solution predicts very well the time-averaged plasma data and the keeper voltage after 5500 hrs of operation in high-power mode. When the wave motion that occurs naturally in these devices is accounted for, based on an estimate of the maximum wave amplitude, the molybdenum-keeper erosion profile observed in the XIPS(c) discharge cathode is also reproduced within a factor of two of the observation. When the same model is applied to predict the erosion of a tantalum keeper we find that erosion is reduced by more than two orders of magnitude compared to the molybdenum keeper due the significantly lower sputtering yield of tantalum. A tantalum keeper would therefore allow keeper lifetimes that greatly exceed the present requirements for deep-space robotic missions considered by NASA. Moreover, such large reduction of the erosion renders the largest uncertainties in the models, which are associated with the wave amplitude estimates and the electron transport model, negligible.

plasma simulations↗
NASA NTRS1980

Measurements of potential of a cylindrical monopole antenna on a rotating spacecraft

Measurements of antenna potential on the Helios 1 spacecraft are presented and discussed. The behavior of the potential indicates that Lyman-alpha and shorter wavelengths play an important role in determining antenna and spacecraft potential, and that conversely, longer wavelengths are unimportant. As expected, a voltage spike usually occurs when the antenna is shadowed. However, when the spike is not present, the potential variations on an antenna which is not shadowed can be estimated. For this case, the spectrum is about (Fourier coefficient) 2 V x (2fo/f)2 where fo is the spacecraft spin frequency, and f is an even harmonic of the spin frequency. Suggestions for measuring low-frequency waves are briefly discussed in relation to the experimental results, and slight tipping of the spacecraft is recommended to avoid shadowing.

Kellogg, P. J.↗
NASA NTRS2013

NASA Tech Briefs, October 2013

Topics include: A Short-Range Distance Sensor with Exceptional Linearity; Miniature Trace Gas Detector Based on Microfabricated Optical Resonators; Commercial Non-Dispersive Infrared Spectroscopy Sensors for Sub-Ambient Carbon Dioxide Detection; Fast, Large-Area, Wide-Bandgap UV Photodetector for Cherenkov Light Detection; Mission Data System Java Edition Version 7; Adaptive Distributed Environment for Procedure Training (ADEPT); LEGEND, a LEO-to-GEO Environment Debris Model; Electronics/Computers; Millimeter-Wave Localizers for Aircraft-to-Aircraft Approach Navigation; Impedance Discontinuity Reduction Between High-Speed Differential Connectors and PCB Interfaces; SpaceCube Version 1.5; High-Pressure Lightweight Thrusters; Non-Magnetic, Tough, Corrosion- and Wear-Resistant Knives From Bulk Metallic Glasses and Composites; Ambient Dried Aerogels; Applications for Gradient Metal Alloys Fabricated Using Additive Manufacturing; Passivation of Flexible YBCO Superconducting Current Lead With Amorphous SiO2 Layer; Propellant-Flow-Actuated Rocket Engine Igniter; Lightweight Liquid Helium Dewar for High-Altitude Balloon Payloads; Method to Increase Performance of Foil Bearings Through Passive Thermal Management; Unibody Composite Pressurized Structure; JWST Integrated Science Instrument Module Alignment Optimization Tool; Radar Range Sidelobe Reduction Using Adaptive Pulse Compression Technique; Digitally Calibrated TR Modules Enabling Real-Time Beamforming SweepSAR Architectures; Electro-Optic Time-to-Space Converter for Optical Detector Jitter Mitigation; Partially Transparent Petaled Mask/Occulter for Visible-Range Spectrum; Educational NASA Computational and Scientific Studies (enCOMPASS); Coarse-Grain Bandwidth Estimation Scheme for Large-Scale Network; Detection of Moving Targets Using Soliton Resonance Effect; High-Efficiency Nested Hall Thrusters for Robotic Solar System Exploration; High-Voltage Clock Driver for Photon-Counting CCD Characterization; Development of the Code RITRACKS; and Enabling Microliquid Chromatography by Microbead Packing of Microchannels.

Source record↗
NASA NTRS2011

A Universal Tare Load Prediction Algorithm for Strain-Gage Balance Calibration Data Analysis

An algorithm is discussed that may be used to estimate tare loads of wind tunnel strain-gage balance calibration data. The algorithm was originally developed by R. Galway of IAR/NRC Canada and has been described in the literature for the iterative analysis technique. Basic ideas of Galway's algorithm, however, are universally applicable and work for both the iterative and the non-iterative analysis technique. A recent modification of Galway's algorithm is presented that improves the convergence behavior of the tare load prediction process if it is used in combination with the non-iterative analysis technique. The modified algorithm allows an analyst to use an alternate method for the calculation of intermediate non-linear tare load estimates whenever Galway's original approach does not lead to a convergence of the tare load iterations. It is also shown in detail how Galway's algorithm may be applied to the non-iterative analysis technique. Hand load data from the calibration of a six-component force balance is used to illustrate the application of the original and modified tare load prediction method. During the analysis of the data both the iterative and the non-iterative analysis technique were applied. Overall, predicted tare loads for combinations of the two tare load prediction methods and the two balance data analysis techniques showed excellent agreement as long as the tare load iterations converged. The modified algorithm, however, appears to have an advantage over the original algorithm when absolute voltage measurements of gage outputs are processed using the non-iterative analysis technique. In these situations only the modified algorithm converged because it uses an exact solution of the intermediate non-linear tare load estimate for the tare load iteration.

balance calibration analysis↗
NASA NTRS1984

Electrodynamic Tethers. 1: Power Generator in LEO. 2: Thrust for Propulsion and Power Storage

An electrodynamic tether consists of a long insulated wire in space whose orbital motion cuts across lines of magnetic flux to produce an induce voltage that in typical low orbits averages about 200 v/km. Such a system should be capable of generating substantial electrical power, at the expense of IXB drag acting on its orbital energy. If a reverse current is driven against the induced voltage, the system should act as a motor producing IXB thrust. A reference system was designed, capable of generating 20 KW of power into an electrical load located anywhere along the wire at the expense of 2.6N (20,000 J/sec) drag on the wire. In an ideal system, the conversion between mechanical and electrical energy would reach 100% efficiency. In the actual system part of the 20 KW is lost to internal resistance of the wire, plasma and ionosphere, while the drag force is increased by residual air drag. The 20 KW PMG system as designed is estimated to provide 18.7 KW net power to the load at total drag loss of 20.4 KJ/sec, or an overall efficiency of 92%. Similar systems using heavier wire appear capable of producing power levels in excess of 1 Megawatt at voltages of 2-4 KV, with conversion efficiency between mechanical and electrical power better than 95%. The hollow cathode based system should be readily reversible from generator to motor operation by driving a reverse current using onboard power.

Mccoy, J. E.↗
NASA NTRS1995

Dynamic interactions between ionospheric plasma and spacecraft

Studies of the interactions between the Space Station Freedom and ionospheric plasma led to an improved understanding of the dynamics of these interactions. Some of the issues related to developing and sustaining arcs in ionospheric conditions are considered. A technique for the estimation of the amplitude and duration of arcs is presented. The technique uses the capacitance of the system to estimate the peak current and then uses the charge stored to estimate the arc duration. As new technologies are implemented on spacecraft, new environmental compatibility issues will arise. Some of the issues related to driving dielectric surfaces with alternating current voltages are considered. The steady state charging criteria is that over an oscillation, the ion charge collected is compensated for by the electron charge collected. This tends to drive the average potential negative so that the dielectric surface is positive for only a small portion of the cycle.

Snyder, David B.↗
NASA NTRS1975

Numerical procedure for analyzing Langmuir probe data

A numerical procedure is proposed for analyzing Langmuir probe data in the presence of a two-group plasma containing both primary and Maxwellian electrons. The procedure is known as a least-squares differential-correction technique for determining the unknown coefficients of the governing equation. It is shown that for a given set of input data the results of the analysis are unique and independent of the initial estimate of electron temperature, that convergence is fastest when electron temperature is overestimated, that the results are sensitive to the region of the curve used as input and also to the voltage increment, and that plasma properties determined by the proposed numerical procedure are either consistent with those determined graphically or closer to expected values. With a suitable data acquisition system, the Fortran IV program worked out for this procedure could be used to provide real-time plasma diagnostic information for an operating ion thruster.

Beattie, J. R.↗
NASA NTRS1978

Ion beam divergence characteristics of two-grid accelerator systems

The first comprehensive experimental investigation of two-grid accelerator systems is presented. A wide range of geometrical grid parameters and grid set operating conditions were investigated for their effect on ion beam divergence. Ion beam divergence was found to depend most strongly on normalized perveance per hole, grid separation ratio, net-to-total accelerating voltage ratio, and discharge-to-total accelerating voltage ratio variations. The graphical results contained herein provide guidelines for the design of ion accelerator systems. A general ion beam divergence angle correlation was developed to permit approximate beam divergence estimates, at parametric values other than those tested, of present grid set designs. Although argon was the main test gas used in this study, it is shown that the results are applicable to other propellants as well.

Aston, G.↗
NASA NTRS2007

Carbon Nanotubes for Space Photovoltaic Applications

Carbon nanotubes (CNTs) can be envisioned as an individual graphene sheet rolled into a seamless cylinder (single-walled, SWNT), or concentric sheets as in the case of a multi-walled carbon nanotube (MWNT) (1). The role-up vector will determine the hexagonal arrangement and "chirality" of the graphene sheet, which will establish the nanotube to be metallic or semiconducting. The optoelectronic properties will depend directly on this chiral angle and the diameter of the SWNT, with semiconductor types exhibiting a band gap energy (2). Characteristic of MWNTs are the concentric graphene layers spaced 0.34 nm apart, with diameters from 10-200 nm and lengths up to hundreds of microns (2). In the case of SWNTs, the diameters range from 0.4 - 2 nm and lengths have been reported up to 1.5 cm (3). SWNTs have the distinguishable property of "bundling" together due to van der Waal's attractions to form "ropes." A comparison of these different structural types is shown in Figure 1. The use of SWNTS in space photovoltaic (PV) applications is attractive for a variety of reasons. Carbon nanotubes as a class of materials exhibit unprecedented optical, electrical, mechanical properties, with the added benefit of being nanoscale in size which fosters ideal interaction in nanomaterial-based devices like polymeric solar cells. The optical bandgap of semiconducting SWNTs can be varied from approx. 0.4 - 1.5 eV, with this property being inversely proportional to the nanotube diameter. Recent work at GE Global Research has shown where a single nanotube device can behave as an "ideal" pn diode (5). The SWNT was bridged over a SiO2 channel between Mo contacts and exhibited an ideality factor of 1, based on a fit of the current-voltage data using the diode equation. The measured PV efficiency under a 0.8 eV monochromatic illumination showed a power conversion efficiency of 0.2 %. However, the projected efficiency of these junctions is estimated to be > 5 %, especially when one considers the enhanced absorption (from nanotubes whose bandgap is tailored to illumination) and electromagnetic coupling in a network of nanotubes.

Efstathiadis, Harry↗
NASA NTRS1995

TROPIX Power System Architecture

This document contains results obtained in the process of performing a power system definition study of the TROPIX power management and distribution system (PMAD). Requirements derived from the PMADs interaction with other spacecraft systems are discussed first. Since the design is dependent on the performance of the photovoltaics, there is a comprehensive discussion of the appropriate models for cells and arrays. A trade study of the array operating voltage and its effect on array bus mass is also presented. A system architecture is developed which makes use of a combination of high efficiency switching power convertors and analog regulators. Mass and volume estimates are presented for all subsystems.

Manner, David B.↗
NASA NTRS1982

Extended-performance 8-cm ion thruster operation

The performance of an 8-cm ion thruster has been extended to 32-mN thrust, 4062-s specific impulse, and 0.033-mN/W thrust-to-power ratio. The design of this thruster is similar to the IAPS (Ion Auxiliary Propulsion System), which has a performance of 5-mN thrust, 3500-s specific impulse, and 0.036-mN/W thrust-to-power ratio. The above level of extended performance has been achieved by increasing the discharge power, ion-beam accelerating voltage, and propellant flowrate, and by modifying the propellant-vapor injection, discharge-chamber magnetic-field strength, high-voltage insulators, and electron baffle. This paper describes results obtained in characterizing the extended-performance operation of both the unmodified thruster (i.e., in an IAPS-like configuration) and the modified thruster. Lifetime-estimating measurements for the modified thruster at extended-performance conditions are also presented.

Wessel, F. J.↗
NASA NTRS2007

Effect of Head-Down Bed Rest and Artificial Gravity Countermeasure on Cardiac Autonomic and Advanced Electrocardiographic Function

To study the effects of 21 days of head-down bed rest (HDBR), with versus without an artificial gravity (AG) countermeasure, on cardiac autonomic and advanced electrocardiographic function. Fourteen healthy men participated in the study: seven experienced 21 days of HDBR alone ("HDBR controls") and seven the same degree and duration of HDBR but with approximately 1hr daily short-arm centrifugation as an AG countermeasure ("AG-treated"). Five minute supine high-fidelity 12-lead ECGs were obtained in all subjects: 1) 4 days before HDBR; 2) on the last day of HDBR; and 3) 7 days after HDBR. Besides conventional 12-lead ECG intervals and voltages, all of the following advanced ECG parameters were studied: 1) both stochastic (time and frequency domain) and deterministic heart rate variability (HRV); 2) beat-to-beat QT interval variability (QTV); 3) T-wave morphology, including signal-averaged T-wave residua (TWR) and principal component analysis ratios; 4) other SAECG-related parameters including high frequency QRS ECG and late potentials; and 5) several advanced ECG estimates of left ventricular (LV) mass. The most important results by repeated measures ANOVA were that: 1) Heart rates, Bazett-corrected QTc intervals, TWR, LF/HF power and the alpha 1 of HRV were significantly increased in both groups (i.e., by HDBR), but with no relevant HDBR*group differences; 2) All purely "vagally-mediated" parameters of HRV (e.g., RMSSD, HF power, Poincare SD1, etc.), PR intervals, and also several parameters of LV mass (Cornell and Sokolow-Lyon voltages, spatial ventricular activation times, ventricular gradients) were all significantly decreased in both groups (i.e., by HDBR), but again with no relevant HDBR*group differences); 3) All "generalized" or "vagal plus sympathetic" parameters of stochastic HRV (i.e., SDNN, total power, LF power) were significantly more decreased in the AG-treated group than in the HDBR-only group (i.e., here there was a relevant HDBR*group difference); and 4) QTV index was also significantly more changed (increased) in the AG-treated group than in the HDBR-only group, although this was clearly due to a greater decrease in generalized HRV and not to a greater increase in QTV proper because there was no relevant HDBR*group effect for either the SDNN or the RMSSD of QTV. Brief daily AG treatment by short-arm centrifuge during each of 21 days of HDBR does not appear to protect against HDBR-related losses of cardiac autonomic function or of LV mass as estimated by ECG.

Schlegel, T. T.↗
NASA NTRS1982

Environmentally induced discharges on satellites

A discharge process whose trigger conditions are a negative exposed metallic surface surrounded by a less negative dielectric, and a large voltage gradient at a dielectric/metal interface is proposed. Analysis of SCATHA data for a discharge substantiates the postulation. Surface discharges cause a small transient charge transfer to space which results in voltage transients. A method of computing these transients, based on the charge lost through the capacitance to space and a fraction of charge stored in the dielectric at the discharge source was developed. It gives an estimate of the discharge transients at the discharge site, which is used as input for coupling code analysis of structure/system response. The transient computations were applied to a three-axis stabilized, geosynchronous satellite for both sunlight and eclipse charging. The energy of the transient pulses are about 1 mJ for sunlight discharge and 8 mJ for eclipse. Changing of selected coatings on the satellite would relieve the stress.

Stevens, N. J.↗