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NASA NTRS2002

Pure Water From a Pure Genius

Ammonium perchlorate is widely used throughout the aerospace, munitions, and pyrotechnics industries as a primary ingredient in solid rocket and missile propellants, fireworks, and explosive charges. This highly soluble salt has tainted soils and water sources all over the world, and is believed to be an endocrine disrupter, adversely affecting the growth patterns of a fetus or a young child. UMPQUA Research Company (URC), once a small drinking water testing laboratory and a research and development contractor for NASA's manned spaceflight applications, has evolved to become a leader in water purification and analysis. With a total of 11 patents issued for new technologies created by URC under NASA SBIR contracts and a 25-year commitment to water recycling, the company clearly possessed the qualifications necessary to tackle the presence of perchlorate in water. An SBIR contract with NASA's Marshall Space Flight Center that concentrated on the stringent water quality requirements of long-term, manned spaceflight was the source for URC's process and catalyst to facilitate the destruction of perchlorate and nitrate in water. URC licensed the rights of its unique reduction reaction process to Calgon Carbon Corporation for use with the company's perchlorate/nitrate remediation process, otherwise known as ISEP(R).

Source record↗
NASA NTRS1998

Stability and Phase Noise Tests of Two Cryo-Cooled Sapphire Oscillators

A cryocooled Compensated Sapphire Oscillator (CSO), developed for the Cassini Ka-band Radio Science experiment, and operating in the 8K - 10K temperature range was previously demonstrated to show ultra-high stability of sigma(sub y) = 2.5 x 10 (exp -15) for measuring times 200 seconds less than or equal to tau less than or equal to 600 seconds using a hydrogen maser as reference. We present here test results for a second unit which allows CSO short-term stability and phase noise to be measured for the first time. Also included are design details of a new RF receiver and an intercomparison with the first CSO unit. Cryogenic oscillators operating below about 10K offer the highest possible short term stability of any frequency sources. However, their use has so far been restricted to research environments due to the limited operating periods associated with liquid helium consumption. The cryocooled CSO is being built in support of the Cassini Ka-band Radio Science experiment and is designed to operate continuously for periods of a year or more. Performance targets are a stability of 3-4 x 10 (exp -15) (1 second less than or equal to tau less than or equal to 100 seconds) and phase noise of -73dB/Hz @ 1Hz measured at 34 GHz. Installation in 5 stations of NASA's deep space network (DSN) is planned in the years 2000 - 2002. In the previous tests, actual stability of the CSO for measuring times tau less than or equal to 200 seconds could not be directly measured, being masked by short-term fluctuations of the H-maser reference. Excellent short-term performance, however, could be inferred by the success of an application of the CSO as local oscillator (L.O.) to the JPL LITS passive atomic standard, where medium-term stability showed no degradation due to L.O. instabilities at a level of (sigma)y = 3 x 10 (exp -14)/square root of tau. A second CSO has now been constructed, and all cryogenic aspects have been verified, including a resonator turn-over temperature of 7.907 K, and Q of 7.4 x 10 (exp 8). These values compare to a turn-over of 8.821 K and Q of 1.0 x 10 (exp 9) for the first resonator. Operation of this second unit provides a capability to directly verify for the first time the short-term (1 second less than or equal to tau less than or equal to 200 seconds) stability and the phase noise of the CSO units. The RF receiver used in earlier tests was sufficient to meet Cassini requirements for tau greater than or equal to 10 seconds but had short-term stability limited to 2-4 x 10 (exp -14) at tau = 1 second, a value 10 times too high to meet our requirements. A new low-noise receiver has been designed to provide approximately equal to 10-15 performance at 1 second, and one receiver is now operational, demonstrating again short-term CSO performance with H maser-limited stability. Short-term performance was degraded in the old receiver due to insufficient tuning bandwidth in a 100MHZ quartz VCO that was frequency-locked to the cryogenic sapphire resonator. The new receivers are designed for sufficient bandwidth, loop gain and low noise to achieve the required performance.

Dick, G. John↗
NASA NTRS1995

Long-term Enhancements in Solar Wind Speed

Long-term enhancements in solar wind speed over timescales on the order of a year appear to be a common feature throughout the heliosphere over heliocentric distances that range from less than 0.72 AU to greater than 60. The origin of these events remains to be determined, but they are almost certainly associated with long-term variations at the solar wind source, in contrast with smaller-scale structures such as CIRs, MIRs, and GMIRs which are dynamical in origin. We present a survey of the long-term speed enhancements observed at the Pioneer Venus Orbiter (PVO), IMP 8, Voyager 2, and Pioneer 10 between 1974 and 1994 and compare this with published reports of smaller-scale events such as MIRs. We examine several of these long-term speed enhancements in detail to identify and characterize aspects of their structure, then describe how that structure evolves with heliocentric distance. Finally we discuss some of the implications of these events.

Gazis, P. R.↗
NASA NTRS2012

Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291

We present Chandra studies of the X-ray binary (XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available Chandra observations totaling an effective exposure of 179 ks. We report photometric properties of these sources in a point-source catalog. There are approx. 40% of the bulge sources and approx. 25% of the ring sources showing > 3(sigma) long-term variability in their X-ray count rate. The X-ray colors suggest that a significant fraction of the bulge (approx. 75%) and ring (approx. 65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate that it is a low-luminosity AGN with moderate obscuration; spectral variability is observed between individual observations. We construct 0.3-8.0 keV X-ray luminosity functions (XLFs) for the bulge and ring XRB populations, taking into account the detection incompleteness and background AGN contamination. We reach 90% completeness limits of approx.1.5 x 10(exp 37) and approx. 2.2 x 10(exp 37) erg/s for the bulge and ring populations, respectively. Both XLFs can be fit with a broken power-law model, and the shapes are consistent with those expected for populations dominated by LMXBs. We perform detailed population synthesis modeling of the XRB populations in NGC 1291 , which suggests that the observed combined XLF is dominated by aD old LMXB population. We compare the bulge and ring XRB populations, and argue that the ring XRBs are associated with a younger stellar population than the bulge sources, based on the relative over-density of X-ray sources in the ring, the generally harder X-ray color of the ring sources, the overabundance of luminous sources in the combined XLF, and the flatter shape of the ring XLF.

Luo, B.↗
NASA NTRS1994

Nimbus-7 Earth radiation budget calibration history. Part 2: The Earth flux channels

Nine years (November 1978 to October 1987) of Nimbus-7 Earth radiation budget (ERB) products have shown that the global annual mean emitted longwave, absorbed shortwave, and net radiation were constant to within about + 0.5 W/sq m. Further, most of the small annual variations in the emitted longwave have been shown to be real. To obtain this measurement accuracy, the wide-field-of-view (WFOV) Earth-viewing channels 12 (0.2 to over 50 micrometers), 13 (0.2 to 3.8 micrometers), and 14 (0.7 to 2.8 micrometers) have been characterized in their satellite environment to account for signal variations not considered in the prelaunch calibration equations. Calibration adjustments have been derived for (1) extraterrestrial radiation incident on the detectors, (2) long-term degradation of the sensors, and (3) thermal perturbations within the ERB instrument. The first item is important in all the channels; the second, mainly in channels 13 and 14, and the third, only in channels 13 and 14. The Sun is used as a stable calibration source to monitor the long-term degradation of the various channels. Channel 12, which is reasonably stable to both thermal perturbations and sensor degradation, is used as a reference and calibration transfer agent for the drifting sensitivities of the filtered channels 13 and 14. Redundant calibration procedures were utilized. Laboratory studies complemented analyses of the satellite data. Two nearly independent models were derived to account for the thermal perturbations in channels 13 and 14. The global annual mean terrestrial shortwave and longwave signals proved stable enough to act as secondary calibration sources. Instantaneous measurements may still, at times, be in error by as much as a few Wm(exp -2), but the long-term averages are stable to within a fraction of a Wm(exp -2).

Kyle, H. Lee↗
NASA NTRS1994

The complete polarization state of Io-related radio storms from Jupiter: A statistical study

We report on the complete polarization state (four Stokes parameters) as a function of both frequency and time, of Io-related radiation from Jupiter as observed with the spectropolarimeter at Nancay, France. Our observations include 37 radio storms, with events of both lefthand (LH) and righthand (RH) elliptical polarization and from all Io-related sources (A,B,C and D), plus two non-Io events. The high degree of circular polarization often observed, particularly for LH emission, is difficult to explain in terms of the standard theory of cyclotron maser radiation. The interpretation of the observations in terms of the locations of the sources in Jupiter's magnetosphere is the subject of a companion paper.

Dulk, G. A.↗
NASA NTRS2001

Discovery of a Nonblazar Gamma-Ray Transient Source Near the Galactic Plane: GRO J1838-04

We report the discovery of a remarkable gamma-ray transient source near the Galactic plane, GRO J1838-04. This source was serendipitously discovered by EGRET in 1995 June with a peak intensity of approx. (4 +/- 1) x 10(exp -6) photons/sq cm s (for photon energies larger than 100 MeV) and a 5.9 sigma significance. At that time, GRO J1838-04 was the second brightest gamma-ray source in the sky. A subsequent EGRET pointing in 1995 late September detected the source at a flux smaller than its peak value by a factor of approx. 7. We determine that no radio-loud spectrally flat blazar is within the error box of GRO J1838-04. We discuss the origin of the gamma-ray transient source and show that interpretations in terms of active galactic nuclei or isolated pulsars are highly problematic. GRO J1838-04 provides strong evidence for the existence of a new class of variable gamma-ray sources.

Tavani, M.↗
NASA NTRS1972

An aircraft manufacturer's approach to rideability criteria

The approach of an aircraft manufacturer to ride quality in air transportation is presented. The subjects discussed are: (1) the external and internal environment in terms of vibration and acoustic sources and general response, (2) guidelines and criteria reflecting current practice, (3) present and future efforts to develop rideability criteria, and (4) requirements for data, criteria, and research in various rideability areas.

Omassey, R. C.↗
NASA NTRS1972

Jet engine exhaust noise due to rough combustion and nonsteady aerodynamic sources

Internal sources are accounted for in terms of fluctuations of mass and momentum at the nozzle exit plane. At low Mach numbers, mass flow fluctuations generated at the exit plane by acoustic resonant type fluctuations inside the engine are found to be dominant. In the subsonic Mach number range between 0.3 and 0.5, exit plane mass flow fluctuations at frequencies characteristic of turbulence become most dominant. Above Mach 0.5, the turbulent momentum fluctuations at the exit plane become dominant, and the jet contribution is not found significant at subsonic speeds.

Plett, E. G.↗
NASA NTRS1973

Status of wind-energy conversion

The utilization of wind energy is technically feasible as evidenced by the many past demonstrations of wind generators. The cost of energy from the wind has been high compared to fossil fuel systems. A sustained development effort is needed to obtain economical systems. The variability of the wind makes it an unreliable source on a short-term basis. However, the effects of this variability can be reduced by storage systems or connecting wind generators to fossil fuel systems, hydroelectric systems, or dispersing them throughout a large grid network. The NSF and NASA-Lewis Research Center have sponsored programs for the utilization of wind energy.

Thomas, R. L.↗
NASA NTRS1979

Simultaneous multifrequency observations of Jovian S bursts

The millisecond component of the Jovian decameter emission was studied at high resolution in order to examine the short-term behavior of the S-burst drift rates and to define the drift rate spectrum at high frequencies. By using dynamic spectra of 300 microsec and 3.3 kHz resolution and covering discrete frequency bands in the 26-33 MHz range, large systematic changes in the magnitude of the S-burst drift rates are observed on a time scale of seconds to minutes. The drift rate variability, its dependence on frequency, and absence of the predicted drift rate turnover in the spectrum are interpreted in terms of an ionospheric electron source. Low-resolution intensity-time tracings, abrupt changes in mean drift rates from group to group, and systematic variations in the group-to-group mean drift rates due to predictable temporal changes in the magnetic field gradient on the Io flux tube are discussed. These temporal changes are due to motion of the Io-associated magnetic flux tube in the Jovian magnetosphere.

Flagg, R. S.↗
NASA NTRS1982

Spectra of cosmic X-ray sources

X-ray measurements provide the most direct probes of astrophysical environments with temperatures exceeding one million K. Progress in experimental research utilizing dispersive techniques (e.g., Bragg and grating spectroscopy) is considerably slower than that in areas utilizing photometric techniques, because of the relative inefficiency of the former for the weak X-ray signals from celestial sources. As a result, the term "spectroscopy" as applied to X-ray astronomy has traditionally satisfied a much less restrictive definition (in terms of resolving power) than it has in other wavebands. Until quite recently, resolving powers of order unity were perfectly respectable, and still provide (in most cases) the most useful spectroscopic data. In the broadest sense, X-ray photometric measurements are spectroscopic, insofar as they represent samples of the overall electromagnetic continua of celestial objects.

Holt, S. S.↗
NASA NTRS1985

Mathematical physics approaches to lightning discharge problems

Mathematical physics arguments useful for lightning discharge and generation problems are pursued. A soliton Ansatz for the lightning stroke is treated including a charge generation term which is the ultimate source for the phenomena. Equations are established for a partially ionized plasma inding the effects of pressure, magnetic field, electric field, gravitation, viscosity, and temperature. From these equations is then derived the non-stationary generalized Ohm's Law essential for describing field/current density relationships in the horizon channel of the lightning stroke. The discharge initiation problem is discussed. It is argued that the ionization rate drives both the convective current and electric displacement current to increase exponentially. The statistical distributions of charge in the thundercloud preceding a lightning dischage are considered. The stability of the pre-lightning charge distributions and the use of Boltzmann relaxational equations to determine them are discussed along with a covered impedance path provided by the aircraft.

Kyrala, A.↗
NASA NTRS1985

Charge state distributions of oxygen and carbon in the energy range 1 to 300 keV/e observed with AMPTE/CCE in the magnetosphere

Observations of charge state distributions of oxygen and carbon are presented that were obtained with the charge-energy-mass spectrometer onboard the AMPTE/CCE spacecraft. Data were selected for two different local time sectors (apogee at 1300 LT and 0300 LT, respectively), three L-ranges (4-6, 6-8, and greater than 8), and quiet to moderately disturbed days (Kp less than or equal to 4). The charge state distributions reveal the existence of all charge states of oxygen and carbon in the magnetosphere. The relative importance of the different charge states strongly depends on L and much less on local time. The observations confirm that the solar wind and the ionosphere contribute to the oxygen population, whereas carbon only originates from the solar wind. The L-dependence of the charge state distributions can be interpreted in terms of these different ion sources and of charge exchange and diffusion processes that largely influence the distribution of oxygen and carbon in the magnetosphere.

Kremser, G.↗
NASA NTRS1988

Nd and Sr isotope systematics of river water suspended material - Implications for crustal evolution

Sm-Nd and Rb-Sr isotopic data on suspended material from rivers draining a variety of rock types and ages are presented. The bulk load of rivers and their source rocks are compared in terms of their isotopic characteristics and model ages. The Nd and Sr isotope systematics of the upper crust exposed to weathering are obtained along with the Nd model age distribution of the North American continental surface. The average Sm-Nd and Rb-Sr isotopic parameters for the upper continental crust today are refined.

Goldstein, Steven J.↗
NASA NTRS1990

Symmetry assessment of an air-blast atomizer spray

This study represents an evaluation of the extent to which conventional and recently introduced modern diagnostics can assess the symmetry of sprays formed by three atomizers of identical design. The conventional diagnostics include sheet-lit photography, patternation, and laser diffraction. The modern diagnostic is laser interferometry (phase Doppler). Symmetry is assessed in ambient conditions for four atomizer orientations, and comparisons are made between the diagnostic techniques. The results demonstrate that conventional and modern diagnostics are consistent in the assessment of symmetry, patternation and phase Doppler are most effective in establishing symmetry of mass flux, and phase Doppler, although more tedious to employ, provides the additional information necessary to establish the sources of detected asymmetries in terms of nonuniformities in droplet velocities, size distributions, volume flux, and concentration.

Mcdonnell, V. G.↗
NASA NTRS1990

Scoping estimates of the LDEF satellite induced radioactivity

The Long Duration Exposure Facility (LDEF) satellite was recovered after almost six years in space. It was well-instrumented with ionizing radiation dosimeters, including thermoluminescent dosimeters, plastic nuclear track detectors, and a variety of metal foil samples for measuring nuclear activation products. The extensive LDEF radiation measurements provide the type of radiation environments and effects data needed to evaluate and help resolve uncertainties in present radiation models and calculational methods. A calculational program was established to aid in LDEF data interpretation and to utilize LDEF data for assessing the accuracy of current models. A summary of the calculational approach is presented. The purpose of the reported calculations is to obtain a general indication of: (1) the importance of different space radiation sources (trapped, galactic, and albedo protons, and albedo neutrons); (2) the importance of secondary particles; and (3) the spatial dependence of the radiation environments and effects expected within the spacecraft. The calculational method uses the High Energy Transport Code (HETC) to estimate the importance of different sources and secondary particles in terms of fluence, absorbed dose in tissue and silicon, and induced radioactivity as a function of depth in aluminum.

Armstrong, Tony W.↗