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All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Residents' reactions to long-term sonic boom exposure: Preliminary results

This presentation is about residents' reactions to sonic booms in a long-term sonic boom exposure environment. Although two phases of the data collection have been completed, the analysis of the data has only begun. The results are thus preliminary. The list of four authors reflects the complex multi-disciplinary character of any field study such as this one. Carey Moulton is responsible for Wyle Laboratories' acoustical data collection effort. Robert Baumgartner and Jeff Thomas of HBRS, a social science research firm, are responsible for social survey field work and data processing. The study is supported by the NASA Langley Research Center. The study has several objectives. The preliminary data addresses two of the primary objectives. The first objective is to describe the reactions to sonic booms of people who are living where sonic booms are a routine, recurring feature of the acoustical environment. The second objective is to compare these residents' reactions to the reactions of residents who hear conventional aircraft noise around airports. Here is an overview of the presentation. This study will first be placed in the context of previous community survey research on sonic booms. Next the noise measurement program will be briefly described and part of a social survey interview will be presented. Finally data will be presented on the residents' reactions and these reactions will be compared with reactions to conventional aircraft. Twelve community studies of residents' reactions to sonic booms were conducted in the United States and Europe in the 1960's and early 1970's. None of the 12 studies combined three essential ingredients that are found in the present study. Residents' long-term responses are related to a measured noise environment. Sonic booms are a permanent feature of the residential environment. The respondents' do not live on a military base. The present study is important because it provides the first dose/response relationship for sonic booms that could be expected to apply to residents in civilian residential areas.

Fields, James M.↗
NASA NTRS1994

On the optical counterparts, long-term variabilities, radio jets, and accretion sources in 1E 1740.7-2942 and GRS 1758-258

In this paper we discuss a variety of issues concerning the exciting and mysterious Galactic center gamma-ray sources 1E 1740.7-2942 and GRS 1758-258. We discuss the problem associated with the highly uncertain X-ray absorption column toward 1E 1740.7-2942 and use the recent Roentgen Satellite (ROSAT) results to narrow its range to 0.5-1 x 10(exp 23)/sq cm. Then the current upper limits from deep optical and near-IR searches of stellar objects at these source locations are plotted on an H-R diagram, from which we find the mass of a potential companion star of the (supposed) black hole in GRS 1758-258 to be less than 4 solar mass and in 1E 1740.7-2942 to be less than 9 solar mass. The observed well-collimated radio jets in 1E 1740.7-2942 require the existence of a stable accretion disk (presumably from binary accretion). The apparent association of 1E 1740.7-2942 with a high-density molecular cloud, on the other hand, points to possible accretion directly from the interstellar medium (ISM). We present an analysis of the energetics and kinematics of the radio jets in 1E 1740.7-2942. We present the long-term X-ray light curves of the two sources which include both the Granat/SIGMA's 3 yr monitoring data and all the data from previous imaging balloon and satellite observations over the last decade. The possible physical mechanisms responsible for producing both the long-term X-ray variations and the radio jets are postulated. We also consider Roche lobe-overflowing, low-mass X-ray binaries and Bondi-Hoyle accretion directly from a high-density surrounding medium. We propose a plausible scenario in which both sources are binary systems with a black hole primary and a low-mass companion and they are accreting mainly from the ISM at a rate self-regulated by the interaction between the accretion flow and the emerging hard X-ray flux.

Chen, Wan↗
NASA NTRS1993

Quasi-decadal variability of the stratosphere: Influence of long-term solar ultraviolet variations

A multiple regression statistical model is applied to investigate the existence of upper-stratospheric ozone, temperature, and zonal wind responses to long-term (solar cycle) changes in solar ultraviolet radiation using 11.5 years of reprocessed Nimbus-7 Solar Backscattered Ultraviolet (SBUV) data and 12.4 years of National Meteorological Center (NMC) data. A positive solar cycle variation of independently measured ozone and temperature occurs with maximum amplitude near the low-latitude stratopause. The seasonal solar regression coefficients near 1 mb for both ozone and temperature occur at low latitudes supporting a role for photochemical and radiative forcing in their origin. Zonal wind perturbations that correlate with long-term solar ultraviolet variations are a strong function of season and pressure level. Above approximately 2 mbar, the largest solar-correlated zonal wind enhancements occur at middle winter latitudes near the time of winter solstice in both hemispheres. The Northern Hemisphere December enhancement at 1 mb was especially large, 23 +/- 9 m/s from solar minimum to maximum during the last solar cycle. The derived ozone, temperature, and zonal wind increases with increasing solar ultraviolet flux near the stratopause are larger than predicted by models that consider primarily photochemical and radiative processes. The higher ozone and temperature response amplitudes at low latitudes may be due to modified ozone transport and adiabatic temperature changes induced by the dynamical response. If the midlatitude winter solstice wind enhancements are solar induced, their high amplitudes require a positive feedback due to wave-mean flow interaction such that the planetary wave drag on the flow is reduced under solar maximum conditions.

Hood, L. L.↗
NASA NTRS1994

An overview of millimeter-wave spectroscopic measurements of chlorine monoxide at Thule, Greenland, February-March, 1992: Vertical profiles, diurnal variation, and longer-term trends

Measurements of chlorine monoxide in the stratosphere over Thule, Greenland (73.6 N, 68.4 W) were made quasi-continuously during the period February 8 to March 24, 1992, using a high-sensitivity ground based mm-wave spectrometer. These observations give diurnal, short term, and long term changes in the mixing ratio and vertical distribution of ClO. At an equivalent time after the Antarctic winter solstice, very large concentrations (up to approximately 1.5 ppbv) occur in lower stratospheric ClO, resulting in massive ozone destruction. We saw no evidence for large (approximately 1 top 1.5 ppbv) amounts of ClO in the 16-25 km range over Thule in February or March, in agreement with UARS (satellite) observations by the MLS mm-wave spectrometer for this period, and in marked contrast to UARS/MLS and ER-2 aircraft measurements over northern Europe and eastern Canada, respectively, during January, 1992. We have evidence for smaller enhancements (approximately 0.2 to 0.5 ppbv) in the 18-30 km range during late February-early March, which could result from transport of residual low NO2 air following earlier polar stratospheric cloud (PSC) processing (the last of which occurred at least one month earlier, however) or the result of chemical processing by Pinatubo aerosols. Direct influence of Pinatubo aerosols on Arctic ozone during the spring of 1992 has been difficult to assess, and this enhancement of low-altitude ClO might be a significant indicator of aerosol effects.

De Zafra, R. L.↗
NASA NTRS1995

A flying qualities study of longitudinal long-term dynamics of hypersonic planes

The NASA Dryden Flight Research Center and the Technical University of Munich are cooperating in a research program to assess the impact of unstable long-term dynamics on the flying qualities of planes in hypersonic flight. These flying qualities issues are being investigated with a dedicated flight simulator for hypersonic vehicles located at NASA Dryden. Several NASA research pilots have flown the simulator through well-defined steady-level turns with varying phugoid and height mode instabilities. Th data collected include pilot ratings and comments, performance measurements, and pilot workload measurements. The results presented in this paper include design guidelines for height and phugoid mode instabilities, an evaluation of the tapping method used to measure pilot workload, a discussion of techniques developed by the pilots to control large instabilities, and a discussion of how flying qualities of unstable long-term dynamics influence control power design requirements.

Cox, T.↗
NASA NTRS1996

Analytical Theory of the Destruction Terms in Dissipation Rate Transport Equations

Modeled dissipation rate transport equations are often derived by invoking various hypotheses to close correlations in the corresponding exact equations. D. C. Leslie suggested that these models might be derived instead from Kraichnan's wavenumber space integrals for inertial range transport power. This suggestion is applied to the destruction terms in the dissipation rate equations for incompressible turbulence, buoyant turbulence, rotating incompressible turbulence, and rotating buoyant turbulence. Model constants like C(epsilon 2) are expressed as integrals; convergence of these integrals implies the absence of Reynolds number dependence in the corresponding destruction term. The dependence of C(epsilon 2) on rotation rate emerges naturally; sensitization of the modeled dissipation rate equation to rotation is not required. A buoyancy related effect which is absent in the exact transport equation for temperature variance dissipation, but which sometimes improves computational predictions, also arises naturally. Both the presence of this effect and the appropriate time scale in the modeled transport equation depend on whether Bolgiano or Kolmogorov inertial range scaling applies. A simple application of these methods leads to a preliminary, dissipation rate equation for rotating buoyant turbulence.

Rubinstein, Robert↗
NASA NTRS1996

Reducing On-Board Computer Propagation Errors Due to Omitted Geopotential Terms by Judicious Selection of Uploaded State Vector

Several future, and some current missions, use an on-board computer (OBC) force model that is very limited. The OBC geopotential force model typically includes only the J(2), J(3), J(4), C(2,2) and S(2,2) terms to model non-spherical Earth gravitational effects. The Tropical Rainfall Measuring Mission (TRMM), Wide-field Infrared Explorer (WIRE), Transition Region and Coronal Explorer (TRACE), Submillimeter Wave Astronomy Satellite (SWAS), and X-ray Timing Explorer (XTE) all plan to use this geopotential force model on-board. The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) is already flying this geopotential force model. Past analysis has shown that one of the leading sources of error in the OBC propagated ephemeris is the omission of the higher order geopotential terms. However, these same analyses have shown a wide range of accuracies for the OBC ephemerides. Analysis was performed using EUVE state vectors that showed the EUVE four day OBC propagated ephemerides varied in accuracy from 200 m. to 45 km. depending on the initial vector used to start the propagation. The vectors used in the study were from a single EUVE orbit at one minute intervals in the ephemeris. Since each vector propagated practically the same path as the others, the differences seen had to be due to differences in the inital state vector only. An algorithm was developed that will optimize the epoch of the uploaded state vector. Proper selection can reduce the previous errors of anywhere from 200 m. to 45 km. to generally less than one km. over four days of propagation. This would enable flight projects to minimize state vector uploads to the spacecraft. Additionally, this method is superior to other methods in that no additional orbit estimates need be done. The definitive ephemeris generated on the ground can be used as long as the proper epoch is chosen. This algorithm can be easily coded in software that would pick the epoch within a specified time range that would minimize the OBC propagation error. This techniques should greatly improve the accuracy of the OBC propagation on-board future spacecraft such as TRMM, WIRE, SWAS, and XTE without increasing complexity in the ground processing.

Greatorex, Scott↗
NASA NTRS1996

Long-term archiving and data access: modelling and standardization

This paper reports on the multiple difficulties inherent in the long-term archiving of digital data, and in particular on the different possible causes of definitive data loss. It defines the basic principles which must be respected when creating long-term archives. Such principles concern both the archival systems and the data. The archival systems should have two primary qualities: independence of architecture with respect to technological evolution, and generic-ness, i.e., the capability of ensuring identical service for heterogeneous data. These characteristics are implicit in the Reference Model for Archival Services, currently being designed within an ISO-CCSDS framework. A system prototype has been developed at the French Space Agency (CNES) in conformance with these principles, and its main characteristics will be discussed in this paper. Moreover, the data archived should be capable of abstract representation regardless of the technology used, and should, to the extent that it is possible, be organized, structured and described with the help of existing standards. The immediate advantage of standardization is illustrated by several concrete examples. Both the positive facets and the limitations of this approach are analyzed. The advantages of developing an object-oriented data model within this contxt are then examined.

Hoc, Claude↗
NASA NTRS1994

An Exact Separation of the Spin-Free and Spin-Dependent Terms of the Dirac-Coulomb-Breit Hamiltonian

The Dirac Hamiltonian is transformed by extracting the operator (sigma x p)/2mc from the small component of the wave function and applying it to the operators of the original Hamiltonian. The resultant operators contain products of Paull matrices that can be rearranged to give spin-free and spin-dependent operators. These operators are the ones encountered in the Breit-Pauli Hamiltonian, as well as some of higher order in alpha(sup 2). However, since the transformation of the original Dirac Hamiltonian is exact, the new Hamiltonian can be used in variational calculations, with or without the spin-dependent terms. The new small component functions have the same symmetry properties as the large component. Use of only the spin-free terms of the new Hamiltonian permits the same factorization over spin variables as in nonrelativistic theory, and therefore all the post-Self-Consistent Field (SCF) machinery of nonrelativistic calculations can be applied. However, the single-particle functions are two-component orbitals having a large and small component, and the SCF methods must be modified accordingly. Numerical examples are presented, and comparisons are made with the spin-free second-order Douglas-Kroll transformed Hamiltonian of Hess.

Dyall, Kenneth G.↗
NASA NTRS1998

A Multigroup Method for the Calculation of Neutron Fluence with a Source Term

Current research on the Grant involves the development of a multigroup method for the calculation of low energy evaporation neutron fluences associated with the Boltzmann equation. This research will enable one to predict radiation exposure under a variety of circumstances. Knowledge of radiation exposure in a free-space environment is a necessity for space travel, high altitude space planes and satellite design. This is because certain radiation environments can cause damage to biological and electronic systems involving both short term and long term effects. By having apriori knowledge of the environment one can use prediction techniques to estimate radiation damage to such systems. Appropriate shielding can be designed to protect both humans and electronic systems that are exposed to a known radiation environment. This is the goal of the current research efforts involving the multi-group method and the Green's function approach.

Heinbockel, J. H.↗
NASA NTRS1998

Temperature climatology of the middle atmosphere from long-term lidar measurements at mid- and low-latitudes

The temperature structure of the middle atmosphere has been studied for several decades using a variety of techniques. However, temperature profiles derived from lidar measurements can provide improved vertical resolution and accuracy. Lidars can also provide long-term data series relatively absent of instrumental drift, and integration of the measurements over several hours removes most of the gravity wave-like short-scale disturbances. This paper describes a seasonal climatology of the middle atmosphere temperature derived from lidar measurements obtained at several mid- and low-latitude locations. Results from the following lidars, which have all obtained a long-term measurement record, were used in this study: the two Rayleigh lidars of the Service d'Aeronomie du CNRS, France, located at the Observatoire de Haute Provence (OHP, 44.0 deg N) and at the Centre d'Essais des Landes (CEL, 44.0 deg N), the two Rayleigh/Raman lidars of the Jet Propulsion Laboratory, USA, located at Table Mountain, California (TMF, 34.4 deg N) and at Mauna Loa, Hawaii (MLO, 19.5 deg N), and the Colorado State University, USA, sodium lidar located at Fort Collins, Colorado (CSU, 40.6 deg N). The overall data set extends from 1978 to 1997 with different periods of measurements depending on the instrument. Three of the instruments are located at primary or complementary stations (OHP, TMF, MLO) within the Network for Detection of Stratospheric Change (NDSC). Several aspects of the temperature climatology obtained by lidar in the middle atmosphere are presented, including the climatological temperature average through the year; the annual and semi-annual components, and the differences compared to the CIRA-86 climatological model.

McDermid, I. Stuart↗
NASA NTRS1998

Determination of Stress Coefficient Terms in Cracked Solids for Monoclinic Materials with Plane Symmetry at x3 = 0

Determination of all the coefficients in the crack tip field expansion for monoclinic materials under two-dimensional deformation is presented in this report. For monoclinic materials with a plane of material symmetry at x(sub 3) = 0, the in-plane deformation is decoupled from the anti-plane deformation. In the case of in-plane deformation, utilizing conservation laws of elasticity and Betti's reciprocal theorem, together with selected auxiliary fields, T-stress and third-order stress coefficients near the crack tip are evaluated first from path-independent line integrals. To determine the T-stress terms using the J-integral and Betti's reciprocal work theorem, auxiliary fields under a concentrated force and moment acting at the crack tip are used respectively. Through the use of Stroh formalism in anisotropic elasticity, analytical expressions for all the coefficients including the stress intensity factors are derived in a compact form that has surprisingly simple structure in terms of the Barnett-Lothe tensors, L. The solution forms for degenerated materials, orthotropic, and isotropic materials are presented.

Yuan, F. G.↗
NASA NTRS1997

Very Long Term Oxidation of Ti-48Al-2Cr-2Nb at 704 C In Air

Introduction Titanium aluminides are of great interest for intermediate-temperature (600 C - 850 C) aerospace and power generation applications because of their high specific properties. Replacement of conventional superalloys by titanium aluminides offers the potential of significant weight savings. Extensive development efforts over the past IO years have led to the identification of y (TiAl) + alpha(sub 2) (Ti3Al) alloys, such as the G.E. alloy Ti48Al-2Cr-2Nb (all composition in at. %), which offer a balance of room temperature mechanical properties and high-temperature strength retention. The two phase gamma + alpha(sub 2) class of titanium aluminides also offers superior oxidation and embrittlement resistance compared to the alpha(sub 2) and orthorhombic classes of titanium aluminides. However, environmental durability is still a major concern. Significant progress has recently been made in understanding the fundamental aspects of the oxidation behavior of binary gamma + alpha(sub 2) Ti-Al alloys. However, most of this work has concentrated on short term (less than 1000 hours), high temperature (900 C - 1000 C) exposures. Also little data are available in the literature regarding the oxidation behavior of the quaternary and higher order gamma + alpha(sub 2) engineering alloys. This is especially true for the very long-term, low temperature conditions likely to be experienced during engineering applications. The present work addresses this regime to fill this gap by characterizing the oxidation behavior of Ti48Al-2Cr-2Nb for periods up to 9000 h at 704 C in air.

Locci, I. E.↗
NASA NTRS1991

Long-Term Observations of Her X-1 with BATSE

Pulsed emission from Her X-1 has been observed by BATSE during each Main High state throughout the CGRO (Compton Gamma-Ray Observatory) mission . This long observation set by a single instrument provides new information on long-term behavior of the Her X-1 system. The luminosity varies by more than a factor of 3 between different 35d cycles. Frequency and flux histories do not show a simple relationship between the source intensity and spin behavior, but do show that only spindown occurs when the source is in its lowest intensity state. Orbital analyses will be presented, including tests for consistency of the observed orbital epoch with the long-term ephemeris reported by (Deeter 1991). The intensity profile and onset times of cycles observed by both BATSE and the RXTE ASM (All Sky Monitor) will be compared. Behavior of the cycle start times versus source Main High peak intensity will be presented.

Wilson, R. B.↗
NASA NTRS1999

Antimatter Production for Near-Term Propulsion Applications

This presentation discusses the use and potential of power generated from Proton-Antiproton Annihilation. The problem is that there is not enough production of anti-protons, and that the production methods are inefficient. The cost for 1 gram of antiprotons is estimated at 62.5 trillion dollars. Applications which require large quantities (i.e., about 1 kg) will require dramatic improvements in the efficiency of the production of the antiprotons. However, applications which involve small quantities (i.e., 1 to 10 micrograms may be practical with a relative expansion of capacities. There are four "conventional" antimatter propulsion concepts which are: (1) the solid core, (2) the gas core, (3) the plasma core, and the (4) beam core. These are compared in terms of specific impulse, propulsive energy utilization and vehicle structure/propellant mass ratio. Antimatter-catalyzed fusion propulsion is also evaluated. The improvements outlined in the presentation to the Fermilab production, and other sites. capability would result in worldwide capacity of several micrograms per year, by the middle of the next decade. The conclusions drawn are: (1) the Conventional antimatter propulsion IS not practical due to large p-bar requirement; (2) Antimatter-catalyzed systems can be reasonably considered this "solves" energy cost problem by employing substantially smaller quantities; (3) With current infrastructure, cost for 1 microgram of p-bars is $62.5 million, but with near-term improvements cost should drop; (4) Milligram-scale facility would require a $15 billion investment, but could produce 1 mg, at $0.1/kW-hr, for $6.25 million.

Gerrish, Harold P.↗
NASA NTRS1999

Estimates of Long Term Surface Soil Moisture in the Midwestern U.S. Derived from Satellite Microwave Observations

Soil moisture is a key component of the water and energy balances of the Earth's surface, and has been identified as a parameter of significant potential for improving the accuracy of large-scale land surface-atmosphere interaction models. However, soil moisture is often somewhat difficult to measure accurately in both space and time, especially at large spatial scales. Soil moisture is highly variable, and while point measurements are typically quite accurate, subsequent areal averaging of these measurements often leads to large errors. Since remotely sensed land surface observations are already a spatially averaged or areally integrated value, they are a logical input parameter to regional or larger scale land process models. A database of long-term soil moisture was compared to satellite microwave observations over test sites in the Midwestern United States. Ground measurements of average volumetric surface soil moisture in the top ten cm were made bimonthly at 19 locations throughout the state of Illinois. Nighttime microwave brightness temperatures were observed at a frequency of 6.6 GHz, by the Scanning Multichannel Microwave Radiometer (SMMR), onboard the Nimbus 7 satellite. The life of the SMMR instrument spanned from Nov. 1978 to Aug. 1987. At 6.6 GHz, the instrument provided a spatial resolution of approximately 150 km, and a temporal frequency over the test area of about 3 nighttime orbits per week. Vegetation radiative transfer characteristics, such as the canopy transmissivity, were estimated from vegetation indices such as the Normalized Difference Vegetation Index (NDVI) and the 37 GHz Microwave Polarization Difference Index (MPDI). Because the time of satellite coverage does not always coincide with the ground measurements of soil moisture, the existing ground data were used to calibrate a water balance for the top IO cm surface layer in order to interpolate daily surface moisture values. Such a climate-based approach is often more appropriate for estimating large-area average soil moisture because meteorological data are generally more spatially representative than isolated point measurements of soil moisture, Passive microwave remote sensing presents the greatest potential for providing regular spatially representative estimates of surface soil moisture at global scales. Real time estimates should improve weather and climate modelling efforts, while the development of historical data sets will provide necessary information for simulation and validation of long-term climate and global change studies.

Owe, M.↗
NASA NTRS1999

Antimatter Requirements and Energy Costs for Near-Term Propulsion Applications

The superior energy density of antimatter annihilation has often been pointed to as the ultimate source of energy for propulsion. However, the limited capacity and very low efficiency of present-day antiproton production methods suggest that antimatter may be too costly to consider for near-term propulsion applications. We address this issue by assessing the antimatter requirements for six different types of propulsion concepts, including two in which antiprotons are used to drive energy release from combined fission/fusion. These requirements are compared against the capacity of both the current antimatter production infrastructure and the improved capabilities that could exist within the early part of next century. Results show that although it may be impractical to consider systems that rely on antimatter as the sole source of propulsive energy, the requirements for propulsion based on antimatter-assisted fission/fusion do fall within projected near-term production capabilities. In fact, a new facility designed solely for antiproton production but based on existing technology could feasibly support interstellar precursor missions and omniplanetary spaceflight with antimatter costs ranging up to $6.4 million per mission.

Schmidt, G. R.↗
NASA NTRS1995

A Flying Qualities Study of Longitudinal Long-Term Dynamics of Hypersonic Planes

The NASA Dryden Flight Research Center and the Technical University of Munich are cooperating in a research program to assess the impact of unstable long-term dynamics on the flying qualities of planes in hypersonic flight. These flying qualities issues are being investigated with a dedicated flight simulator for hypersonic vehicles located at NASA Dryden. Several NASA research pilots have flown the simulator through well defined steady-level turns with varying phugoid and height mode instabilities. The data collected include Pilot ratings and comments, performance measurements, and Pilot workload measurements. The results presented in this paper include design guidelines for height and Phugoid mode instabilities, an evaluation of the tapping method used to measure pilot workload, a discussion of techniques developed by the pilots to control large instabilities, and a discussion of how flying qualities of unstable long-term dynamics influence control Power design requirements.

Cox, Timothy H.↗