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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1957

Steady Nuclear Combustion in Rockets

The astrophysical theory of stationary nuclear reactions in stars is applied to the conditions that would be met in the practical engineering cases that would differ from the former, particularly with respect to the much lower combustion pressures, dimensions of the reacting volume, and burnup times. This application yields maximum rates of hear production per unit volume of reacting gas occurring at about 10(exp 8) K in the cases of reactions between the hydrogen isotopes, but yields higher rates for heavier atoms. For the former, with chamber pressures of the order of 100 atmospheres, the energy production for nuclear combustion reaches values of about 10(exp 4) kilocalories per cubic meter per second, which approaches the magnitude for the familiar chemical fuels. The values are substantially lower for heavier atoms, and increase with the square of the combustion pressure. The half-life of the burnup in the fastest reactions may drop to values as low as those for chemical fuels so that, despite the high temperature, the radiated energy can remain smaller than the energy produced, particularly if an inefficiently radiating (i.e., easily completely ionized reacting material like hydrogen), is used. On the other hand, the fraction of completely ionized particles in the gases undergoing nuclear combustion must not exceed a certain upper limit because the densities (approximately 10(exp -10) grams per cubic centimeter)) lie in the range of high vacua and only for the previously mentioned fraction of nonionized particles can mean free paths be retained small enough so that the chamber diameters of several dozen meters will suffice. Under these conditions it appears that continuously maintained stable nuclear reactions at practical pressures and dimensions are fundamentally possible and their application can be visualized as energy sources for power plants and propulsion units.

Saenger, E.↗
NASA NTRS2008

Balanced Flow Meters without Moving Parts

Balanced flow meters are recent additions to an established class of simple, rugged flow meters that contain no moving parts in contact with flow and are based on measurement of pressure drops across objects placed in flow paths. These flow meters are highly accurate, minimally intrusive, easily manufacturable, and reliable. A balanced flow meter can be easily mounted in a flow path by bolting it between conventional pipe flanges. A balanced flow meter can be used to measure the flow of any of a variety of liquids or gases, provided that it has been properly calibrated. Relative to the standard orifice-plate flow meter, the balanced flow meter introduces less turbulence and two times less permanent pressure loss and is therefore capable of offering 10 times greater accuracy and repeatability with less dissipation of energy. A secondary benefit of the reduction of turbulence is the reduction of vibration and up to 15 times less acoustic noise generation. Both the balanced flow meter and the standard orifice-plate flow meter are basically disks that contain holes and are instrumented with pressure transducers on their upstream and downstream faces. The most obvious difference between them is that the standard orifice plate contains a single, central hole while the balanced flow meter contains multiple holes. The term 'balanced' signifies that in designing the meter, the sizes and locations of the holes are determined in an optimization procedure that involves balancing of numerous factors, including volumetric flow, mass flow, dynamic pressure, kinetic energy, all in an effort to minimize such undesired effects as turbulence, pressure loss, dissipation of kinetic energy, and non-repeatability and nonlinearity of response over the anticipated range of flow conditions. Due to proper balancing of these factors, recent testing demonstrated that the balanced flow-meter performance was similar to a Venturi tube in both accuracy and pressure recovery, but featured reduced cost and pipe-length requirements.

Kelley, Anthony R.↗
NASA NTRS1979

Area scaling investigations of charging phenomena

The charging and discharging behavior of square, planar samples of silvered, fluorinated ethylene-propylene (FEP) Teflon thermal control tape was measured. The equilibrium voltage profiles scaled with the width of the sample. A wide range of discharge pulse characteristics was observed, and the area dependences of the peak current, charge, and pulse widths are described. The observed scaling of the peak currents with area was weaker than that previously reported. The discharge parameters were observed to depend strongly on the grounding impedance and the beam voltage. Preliminary results suggest that measuring only the return-current-pulse characteristics is not adequate to describe the spacecraft discharging behavior of this material. The seams between strips of tape appear to play a fundamental role in determining the discharging behavior. An approximate propagation velocity for the charge cleanoff was extracted from the data. The samples - 232, 1265, and 5058 square centimeters in area - were exposed at ambient temperature to a 1- to 2-nA/sq cm electron beam at energies of 10, 15, and 20 kilovolts in a 19-meter-long by 4.6-meter-diameter simulation facility at the Lewis Research Center.

Aron, P. R.↗
NASA NTRS1990

Integrated controls-structures design methodology development for a class of flexible spacecraft

Future utilization of space will require large space structures in low-Earth and geostationary orbits. Example missions include: Earth observation systems, personal communication systems, space science missions, space processing facilities, etc., requiring large antennas, platforms, and solar arrays. The dimensions of such structures will range from a few meters to possibly hundreds of meters. For reducing the cost of construction, launching, and operating (e.g., energy required for reboosting and control), it will be necessary to make the structure as light as possible. However, reducing structural mass tends to increase the flexibility which would make it more difficult to control with the specified precision in attitude and shape. Therefore, there is a need to develop a methodology for designing space structures which are optimal with respect to both structural design and control design. In the current spacecraft design practice, it is customary to first perform the structural design and then the controller design. However, the structural design and the control design problems are substantially coupled and must be considered concurrently in order to obtain a truly optimal spacecraft design. For example, let C denote the set of the 'control' design variables (e.g., controller gains), and L the set of the 'structural' design variables (e.g., member sizes). If a structural member thickness is changed, the dynamics would change which would then change the control law and the actuator mass. That would, in turn, change the structural model. Thus, the sets C and L depend on each other. Future space structures can be roughly divided into four mission classes. Class 1 missions include flexible spacecraft with no articulated appendages which require fine attitude pointing and vibration suppression (e.g., large space antennas). Class 2 missions consist of flexible spacecraft with articulated multiple payloads, where the requirement is to fine-point the spacecraft and each individual payload while suppressing the elastic motion. Class 3 missions include rapid slewing of spacecraft without appendages, while Class 4 missions include general nonlinear motion of a flexible spacecraft with articulated appendages and robot arms. Class 1 and 2 missions represent linear mathematical modeling and control system design problems (except for actuator and sensor nonlinearities), while Class 3 and 4 missions represent nonlinear problems. The development of an integrated controls/structures design approach for Class 1 missions is addressed. The performance for these missions is usually specified in terms of (1) root mean square (RMS) pointing errors at different locations on the structure, and (2) the rate of decay of the transient response. Both of these performance measures include the contributions of rigid as well as elastic motion.

Maghami, P. G.↗
NASA NTRS1981

Preliminary comparison of material charging properties using single-energy and multienergy electron beams

Results of tests designed to compare the charging properties of spacecraft material under a monoenergetic beam and under a continuously distributed beam are summarized. In the test setup the electron source was mounted in the top of a cylindrical vacuum chamber. A sheet of 5-mil-thick Kapton was placed on an insulated metal substrate at the bottom of the vacuum chamber. The dc current arriving on the substrate was measured and a field meter measured the potential of the test sample. A retarding potential analyzer measured the energy spectrum of the incident electron beam. With the monoenergetic beam, the sample charged to 12 kV and electrical discharges occurred. With the multi-energy spectra the samples charged to only 6 kV and 4 kV, and no discharger were observed. In these experiments, no effort was made to duplicate the spectra occurring in space. The tests were intended to simply to compare spacecraft material charging properties using monoenergetic and continuous multi-energy beams.

Adamo, R. C.↗
NASA NTRS1983

Device Stores and Discharges Metered Fluid

Hand-held container accepts measured amount of liquid from pressurized supply. Supply pressure drives spring-loaded piston that stores enough mechanical energy to discharge measured liquid into another container. Original application of container was to rehydrate sterilized pre-packaged food in zerogravity environment of space vehicles. Possible terrestrial applicatios include dispensing of toxic fluids or metering of fluids for household, commercial or laboratory uses.

Hooper, S. L.↗
NASA NTRS1986

ASTROMAG: A superconducting particle astrophysics magnet facility for the space station

This paper describes a superconducting magnet system which is the heart of a particle astrophysics facility to be mounted on a portion of the proposed NASA space station. This facility will complete the studies done by the electromagnetic observatories now under development and construction by NASA. The paper outlines the selection process of the type of magnet to be used to analyze the energy and momentum of charged particles from deep space. The ASTROMAG superconducting magnet must meet all the criteria for a shuttle launch and landing, and it must meet safety standards for use in or near a manned environment such as the space station. The magnet facility must have a particle gathering aperture of at least 1 square meter steradian and the facility should be capable of resolving heavy nuclei with a total energy of 10 Tev or more.

Green, M. A.↗
NASA NTRS1974

A feasibility study for a remote laser water turbidity meter

A technique to remotely determine the attenuation coefficient (alpha) of the water was investigated. The backscatter energy (theta = 180 deg) of a pulse laser (lambda = 440 - 660 nm) was found directly related to the water turbidity. The greatest sensitivity was found to exist at 440 nm. For waters whose turbidity was adjusted using Chesapeake Bay sediment, the sensitivity in determining alpha at 440 nm was found to be approximately 5 - 10%. A correlation was also found to exist between the water depth (time) at which the peak backscatter occurs and alpha.

Hickman, G. D.↗
NASA NTRS1973

Microwave radiation hazards around large microwave antenna.

The microwave radiation hazards associated with the use of large antennas become increasingly more dangerous to personnel as the transmitters go to ever higher powers. The near-field area is of the greatest concern. It has spill over from subreflector and reflections from nearby objects. Centimeter waves meeting in phase will reinforce each other and create hot spots of microwave energy. This has been measured in front of and around several 26-meter antennas. Hot spots have been found and are going to be the determining factor in delineating safe areas for personnel to work. Better techniques and instruments to measure these fields are needed for the evaluation of hazard areas.

Klascius, A.↗
NASA NTRS2019

PDC19 Impact Exercise: Probabilistic Asteroid Impact Risk Assessment

Probabilistic Asteroid Impact Risk (PAIR) - PDC (Planetary Defense Conference) 2019 Hypothetical Exercise, NASA Ames, Asteroid Threat Assessment Project (ATAP) - Characterization Summary and Updates: Assessment date: 19 April 2027; Impact date: 29 April 2027 (10 days); Earth impact probability: 100 percent, New York Area; Diameter (meters): 60 plus or minus 10 (1 minus sigma), range 26–93; Energy: mean 11 megatons, range 650 kilotons to 46 megatons; Type: S class, remaining chunk of disrupted contact binary. Risk Summary: Affected population: mean 2.4 million, range zero to 10.2 million; Likely airburst at approximately16 kilometers altitude (8 to 29 kilometers); Blast overpressure is primary hazard; Damage out to approximately 70 kilometers if larger, lower burst; Little-to-no damage if burst is small and high.

Wheeler, Lorien↗
NASA NTRS1983

The value of residential photovoltaic systems: A comprehensive assessment

Utility-interactive photovoltaic (PV) arrays on residential rooftops appear to be a potentially attractive, large-scale application of PV technology. Results of a comprehensive assessment of the value (i.e., break-even cost) of utility-grid connected residential photovoltaic power systems under a variety of technological and economic assumptions are presented. A wide range of allowable PV system costs are calculated for small (4.34 kW (p) sub ac) residential PV systems in various locales across the United States. Primary factor in this variation are differences in local weather conditions, utility-specific electric generation capacity, fuel types, and customer-load profiles that effect purchase and sell-back rates, and non-uniform state tax considerations. Additional results from this analysis are: locations having the highest insolation values are not necessary the most economically attractive sites; residential PV systems connected in parallel to the utility demonstrate high percentages of energy sold back to the grid, and owner financial and tax assumptions cause large variations in break-even costs. Significant cost reduction and aggressive resolution of potential institutional impediments (e.g., liability, standards, metering, and technical integration) are required for a residential PV marker to become a major electric-grid-connected energy-generation source.

Borden, C. S.↗
NASA NTRS2003

Characterization of Pixelated Cadmium-Zinc-Telluride Detectors for Astrophysical Applications

Comparisons of charge sharing and charge loss measurements between two pixelated Cadmium-Zinc-Telluride (CdZnTe) detectors are discussed. These properties along with the detector geometry help to define the limiting energy resolution and spatial resolution of the detector in question. The first detector consists of a 1-mm-thick piece of CdZnTe sputtered with a 4x4 array of pixels with pixel pitch of 750 microns (inter-pixel gap is 100 microns). Signal readout is via discrete ultra-low-noise preamplifiers, one for each of the 16 pixels. The second detector consists of a 2-mm-thick piece of CdZnTe sputtered with a 16x16 array of pixels with a pixel pitch of 300 microns (inter-pixel gap is 50 microns). This crystal is bonded to a custom-built readout chip (ASIC) providing all front-end electronics to each of the 256 independent pixels. These detectors act as precursors to that which will be used at the focal plane of the High Energy Replicated Optics (HERO) telescope currently being developed at Marshall Space Flight Center. With a telescope focal length of 6 meters, the detector needs to have a spatial resolution of around 200 microns in order to take full advantage of the HERO angular resolution. We discuss to what degree charge sharing will degrade energy resolution but will improve our spatial resolution through position interpolation.

Gaskin, Jessica↗
NASA NTRS2003

Characterization of a 2-mm thick, 16x16 Cadmium-Zinc-Telluride Pixel Array

The detector under study is a 2-mm-thick, 16x16 Cadmium-Zinc-Telluride pixel array with a pixel pitch of 300 microns and inter-pixel gap of 50 microns. This detector is a precursor to that which will be used at the focal plane of the High Energy Replicated Optics (HERO) telescope currently being developed at Marshall Space Flight Center. With a telescope focal length of 6 meters, the detector needs to have a spatial resolution of around 200 microns in order to take full advantage of the HERO angular resolution. We discuss to what degree charge sharing will degrade energy resolution but will improve our spatial resolution through position interpolation. In addition, we discuss electric field modeling for this specific detector geometry and the role this mapping will play in terms of charge sharing and charge loss in the detector.

Gaskin, Jessica↗
NASA NTRS1997

Experimental Characterization of Hysteresis in a Revolute Joint for Precision Deployable Structures

Recent studies of the micro-dynamic behavior of a deployable telescope metering truss have identified instabilities in the equilibrium shape of the truss in response to low-energy dynamic loading. Analyses indicate that these micro-dynamic instabilities arise from stick-slip friction within the truss joints (e.g., hinges and latches). The present study characterizes the low-magnitude quasi-static load cycle response of the precision revolute joints incorporated in the deployable telescope metering truss, and specifically, the hysteretic response of these joints caused by stick-slip friction within the joint. Detailed descriptions are presented of the test setup and data reduction algorithms, including discussions of data-error sources and data-filtering techniques. Test results are presented from thirteen specimens, and the effects of joint preload and manufacturing tolerances are investigated. Using a simplified model of stick-slip friction, a relationship is made between joint load-cycle behavior and micro-dynamic dimensional instabilities in the deployable telescope metering truss.

Lake, Mark S.↗
NASA NTRS1986

Two classes of solar energetic particle events associated with impulsive and long-duration soft X-ray flares

For the period 1978 September to 1983 December, 67 solar particle events have been identified for which the instruments detected electrons above 3 MeV and for which there are soft X-ray observations. The events are divided into two classes impulsive and long-duration - based on their signature in soft X-rays, and it is found that they have different properties. The events originating with impulsive flares are associated with intensed meter-wavelength type III bursts with associated type V continuum. The events associated with long-duration flares can originate anywhere on the solar disk, extend to much higher proton energies, and are well associated with coronal and interplanetary shocks; for about half of the long-duration events, the associated meter-wavelength events do not include type III bursts. The results discovered by Evenson et al. (1984) and by Kahler et al. (1984) are extended.

Cane, H. V.↗
NASA NTRS1982

Solar-Energy System for a Commercial Building--Topeka, Kansas

Report describes a solar-energy system for space heating, cooling and domestic hot water at a 5,600 square-foot (520-square-meter) Topeka, Kansas, commercial building. System is expected to provide 74% of annual cooling load, 47% of heating load, and 95% of domestic hot-water load. System was included in building design to maximize energy conservation.

Source record↗
NASA NTRS2012

The Gamma-Ray Imager/Polarimeter for Solar Flares (GRIPS)

The balloon-borne Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) instrument will provide a near-optimal combination of high-resolution imaging, spectroscopy, and polarimetry of solar-flare gamma-ray/hard X-ray emissions from approximately 20 keV to greater than approximately 10 MeV. GRIPS will address questions raised by recent solar flare observations regarding particle acceleration and energy release, such as: What causes the spatial separation between energetic electrons producing hard X-rays and energetic ions producing gamma-ray lines? How anisotropic are the relativistic electrons, and why can they dominate in the corona? How do the compositions of accelerated and ambient material vary with space and time, and why? The spectrometer/polarimeter consists of sixteen 3D position-sensitive germanium detectors (3D-GeDs), where each energy deposition is individually recorded with an energy resolution of a few keV FWHM and a spatial resolution of less than 0.1 cubic millimeter. Imaging is accomplished by a single multi-pitch rotating modulator (MPRM), a 2.5-centimeter thick tungsten alloy slit/slat grid with pitches that range quasi-continuously from 1 to 13 millimeters. The MPRM is situated 8 meters from the spectrometer to provide excellent image quality and unparalleled angular resolution at gamma-ray energies (12.5 arcsec FWHM), sufficient to separate 2.2 MeV footpoint sources for almost all flares. Polarimetry is accomplished by analyzing the anisotropy of reconstructed Compton scattering in the 3D-GeDs (i.e., as an active scatterer), with an estimated minimum detectable polarization of a few percent at 150-650 keV in an X-class flare. GRIPS is scheduled for a continental-US engineering test flight in fall 2013, followed by long or ultra-long duration balloon flights in Antarctica.

Shih, Albert Y.↗