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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Mesoscale Variability in SUCCESS Data

Analysis of meteorological, chemical, and microphysical data from the airborne SUCCESS mission is reported. Careful analysis of the complex DC-8 flight pattern of May 2, 1996 reveals 19 linear or nearly linear flight segments within six main geographical areas, which we have analyzed. Significant mountain wave activity is revealed in the data from the MMS and MTP instruments on the DC-8, which resembles previous observations of mountain wave structures near Boulder, CO. Strong mountain-wave-induced upwelling downwind of the Rockies is noted. Turbulence is also noted in regions of the mountain wave consistent with overturning near the tropopause. Zonal winds recorded on the ER-2 are shown to consistent with mountain wave breaking at or near critical levels in the stratosphere, consistent with the strong turbulence reported by the pilot during the ER-2 flight. Those observations have been supported with spectral analyses and modeling studies. "Postcasts" of mountain wave activity on May 2, 1996, using the Naval Research Laboratory Mountain Wave Forecast Model (NRL/MWFM) predicts both strong mountain wave activity near the tropopause (as measured by the DC-8) and strong mountain-wave-induced turbulence in the stratosphere (as encountered by the ER-2). Two-dimensional simulations of fluid flow over topography reveal similar isentropic structures to observations.

Eckermann, Stephen D.↗
NASA NTRS1998

Observations of the Spectral Distribution of Solar Irradiance at the Ground During SUCCESS

During SUCCESS two independent and independently calibrated spectrometers were deployed at a surface site to determine the spectrally resolved downwelling solar irradiance. Preliminary evidence shows that for cloud-free conditions there is general agreement between measurements and model derived irradiance, at least to within instrumental and model uncertainties of 5%, with greatest disagreement Occurring in the 400 nm - 700 nm band. Cirrus effects are most prominent in the near-infrared bands beyond 1500 nm while the influence of very thin (subvisual) cirrus is evident in the scattered flux at the surface. Further remote sensing applications and the assessment of cloud absorption is contingent upon measurements of the surface spectral albedo.

Pilewskie, Peter↗
NASA NTRS2000

Marshall Convergent Coating Development Team: An Aerospace Success Story

The external thermal insulation systems for the Space Shuttle solid rocket boosters and the Air Force Titan IV payload fairings were in jeopardy due to EPA regulatory problems, endangering the flight status of both vehicles. The Marshall Convergent Coating (MCC-1) Development Team was formed in February 1994 to develop and implement an EPA-compliant external thermal insulation system for both systems. MCC-1 made use of a process known as Convergent Spray Technology (CST), a solventless, sprayable process that eliminated the environmentally hazardous chemicals involved with the old methods. Implemented in record time, the new insulation was so successful that it was selected for two additional flight vehicles, Boeing's Sea Launch and Delta TV. The activity also led to commercial spin-off pilot projects. The team continues today to share data between the various production sites, resolve production issues, expand the material's use, and consider potential improvements for the future.

Lester, Carl N.↗
NASA NTRS2000

Fault Tree in the Trenches, A Success Story

Getting caught up in the explanation of Fault Tree Analysis (FTA) minutiae is easy. In fact, most FTA literature tends to address FTA concepts and methodology. Yet there seems to be few articles addressing actual design changes resulting from the successful application of fault tree analysis. This paper demonstrates how fault tree analysis was used to identify and solve a potentially catastrophic mechanical problem at a rocket motor manufacturer. While developing the fault tree given in this example, the analyst was told by several organizations that the piece of equipment in question had been evaluated by several committees and organizations, and that the analyst was wasting his time. The fault tree/cutset analysis resulted in a joint-redesign of the control system by the tool engineering group and the fault tree analyst, as well as bragging rights for the analyst. (That the fault tree found problems where other engineering reviews had failed was not lost on the other engineering groups.) Even more interesting was that this was the analyst's first fault tree which further demonstrates how effective fault tree analysis can be in guiding (i.e., forcing) the analyst to take a methodical approach in evaluating complex systems.

Long, R. Allen↗
NASA NTRS2001

The Standard Autonomous File Server, a Customized, Off-the-Shelf Success Story

The Standard Autonomous File Server (SAFS), which includes both off-the-shelf hardware and software, uses an improved automated file transfer process to provide a quicker, more reliable, prioritized file distribution for customers of near real-time data without interfering with the assets involved in the acquisition and processing of the data. It operates as a stand-alone solution, monitoring itself, and providing an automated fail-over process to enhance reliability. This paper will describe the unique problems and lessons learned both during the COTS selection and integration into SAFS, and the system's first year of operation in support of NASA's satellite ground network. COTS was the key factor in allowing the two-person development team to deploy systems in less than a year, meeting the required launch schedule. The SAFS system his been so successful, it is becoming a NASA standard resource, leading to its nomination for NASA's Software or the Year Award in 1999.

Semancik, Susan K.↗
NASA NTRS1995

The Study of the Successive Metal-Ligand Binding Energies for Fe(sup +), Fe(sup -), V(sup +) and Co(sup +)

The successive binding energies of CO and H2O to Fe(sup +), CO to Fe(sup -), and H2 to Co(sup +) and V(sup +) are presented. Overall the computed results are in good agreement with experiment. The trends in binding energies are analyzed in terms of metal to ligand donation, ligand to metal donation, ligand-ligand repulsion, and changes in the metal atom, such as hybridization, promotion, and spin multiplicity. The geometry and vibrational frequencies are also shown to be directly affected by these effects.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1995

Building a Successful Security Infrastructure: What You Want vs. What You Need vs. What You Can Afford

With the fast growing popularity of the Internet, many organizations are racing to get onto the on-ramp to the Information Superhighway. However, with frequent headlines such as 'Hackers' break in at General Electric raises questions about the Net's Security', 'Internet Security Imperiled - Hackers steal data that could threaten computers world-wide' and 'Stanford Computer system infiltrated; Security fears grow', organizations find themselves rethinking their approach to the on-ramp. Is the Internet safe? What do I need to do to protect my organization? Will hackers try to break into my systems? These are questions many organizations are asking themselves today. In order to safely travel along the Information Superhighway, organizations need a strong security framework. Developing such a framework for a computer site, whether it be just a few dozen hosts or several thousand hosts is not an easy task. The security infrastructure for a site is often developed piece-by-piece in response to security incidents which have affected that site over time. Or worse yet, no coordinated effort has been dedicated toward security. The end result is that many sites are still poorly prepared to handle the security dangers of the Internet. This paper presents guidelines for building a successful security infrastructure. The problem is addressed in a cookbook style method. First is a discussion on how to identify your assets and evaluate the threats to those assets; next are suggestions and tips for identifying the weak areas in your security armor. Armed with this information we can begin to think about what you really need for your site and what you can afford. In this stage of the process we examine the different categories of security tools and products that are available and then present some tips for deciding what is best for your site.

Crabb, Michele D.↗
NASA NTRS1994

The Study of the Successive Metal-ligand Binding Energies for Fe(+), Fe(-), V(+) and Co(+)

The successive binding energies of CO and H2O to Fe(+), CO to Fe(-), and H2 to Co(+) and V(+) are presented. Overall the computed results are in good agreement with experiment. The trends in binding energies are analyzed in terms of metal to ligand donation, ligand to metal donation, ligand-ligand repulsion, and changes in the metal atom, such as hybridization, promotion, and spin multiplicity. The geometry and vibrational frequencies are also shown to be directly affected by these effects.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1995

The Study Of The Successive Metal-Ligand Binding Energies For Fe+, Fe-, V+ and Co+

The successive binding energies of CO and H2O to Fe(+), CO to Fe(-), and H2 to Co(+) and V(+) are presented. Overall the computed results are in good agreement with experiment. The trends in binding energies are analyzed in terms of metal to ligand donation, ligand to metal donation, ligand-ligand repulsion, and changes in the metal atom, such as hybridization, promotion, and spin multiplicity. The geometry and vibrational frequencies are also shown to be directly affected by these effects.

Bauschicher, Charles W., Jr.↗
NASA NTRS1997

SUCCESS Evidence for Cirrus Cloud Ice Nucleation Mechanisms

During the SUCCESS mission, several measurements were made which should improve our understanding of ice nucleation processes in cirrus clouds. Temperature and water vapor concentration were made with a variety of instruments on the NASA DC-8. These observations should provide accurate upper tropospheric humidities. In particular, we will evaluate what humidities are required for ice nucleation. Preliminary results suggest that substantial supersaturations frequently exist in the upper troposphere. The leading-edge region of wave-clouds (where ice nucleation occurs) was sampled extensively at temperatures near -40 and -60C. These observations should give precise information about conditions required for ice nucleation. In addition, we will relate the observed aerosol composition and size distributions to the ice formation observed to evaluate the role of soot or mineral particles on ice nucleation. As an alternative technique for determining what particles act as ice nuclei, numerous samples of aerosols inside ice crystals were taken. In some cases, large numbers of aerosols were detected in each crystal, indicating that efficient scavenging occurred. Analysis of aerosols in ice crystals when only one particle per crystal was detected should help with the ice nucleation issue. Direct measurements of the ice nucleating activity of ambient aerosols drawn into airborne cloud chambers were also made. Finally, measurements of aerosols and ice crystals in contrails should indicate whether aircraft exhaust soot particles are effective ice nuclei.

Jensen, Eric↗
NASA NTRS1996

The Successive OH Binding Energies of Sc(OH)n+ for n=1-3

The geometries of Sc(OH)n+, for n = 1-3, have been optimized using density functional theory, in conjunction with the B3LYP hybrid functional. The zero-point energies are computed at the same level of theory. The successive OH bond energies have been computed at the CCSD(T) level for ScOH+ and Sc(OH)2+. The computed result for ScOD+ is in excellent agreement with the recent experiment of Armentrout and co-workers. There is a dramatic drop for the third OH, because Sc+ has only two valence electrons and therefore the bonding changes when the third OH is added. The difference between the B3LYP and CCSD(T) OH binding energies for the first two OH groups is discussed.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1996

SUCCESS Studies of the Impact of Aircraft on Cirrus Clouds

During April of 1996 NASA will sponsor the SUCCESS project to better understand the impact of subsonic aircraft on the Earth's radiation budget. We plan to better determine the radiative properties of cirrus clouds and of contrails so that satellite observations can better determine their impact on Earth's radiation budget. We hope to determine how cirrus clouds form, whether the exhaust from subsonic aircraft presently affects the formation of cirrus clouds, and if the exhaust does affect the clouds whether the changes induced are of climatological significance. We seek to pave the way for future studies by developing and testing several new instruments. We also plan to better determine the characteristics of gaseous and particulate exhaust products from subsonic aircraft and their evolution in the region near the aircraft. In order to achieve our experimental objectives we plan to use the DC-8 aircraft as an in situ sampling platform. It will carry a wide variety of gaseous, particulate, radiative, and meteorological instruments. We will also use a T-39 aircraft primarily to sample the exhaust from other aircraft. It will carry a suite of instruments to measure particles and gases. We will employ an ER-2 aircraft as a remote sensing platform. The ER-2 will act as a surrogate satellite so that remote sensing observations can be related to the in situ parameters measured by the DC-8 and T-39. The mission strategy calls for a 5 week deployment beginning on April 8, 1996, and ending on May 10, 1996. During this time all three aircraft will be based in Salina, Kansas. A series of flights, averaging one every other day during this period, will be made mainly near the Department of Energy's Climate and Radiation Testbed site (CART) located in Northern Oklahoma, and Southern Kansas. During this same time period an extensive set of ground based measurements will be made by the DOE, which will also be operating several aircraft in the area to better understand the radiative properties of the atmosphere. Additional flights will be made over the Rocky Mountains, to investigate wave clouds. Flights will also be made over the Gulf of Mexico to utilize an oceanic background for remote sensing measurements. The results of this mission will be presented in this talk.

Toon, Owen B.↗
NASA NTRS1997

Ice Nucleation Processes in Upper Tropospheric Wave-Clouds Observed During SUCCESS

We have compared in situ measurements near the leading-edges of wave-clouds observed during the SUCCESS experiment with numerical modeling of ice nucleation. Observations of high supersaturations with respect to ice (\geq 150\%) near the leading edge of a very cold wave cloud (T < --60^\circC) are consistent with recent theoretical and laboratory studies suggesting that large supersaturations are required to homogeneously freeze sulfate aerosols. Also, the peak ice crystal number densities observed in this cloud (about 4cm -3/sup>) are consistent with the number densities calculated in our model. The consistency between model results (using homogeneous freezing and the observations indicates that the number density of effective heterogeneous ice nuclei must be no more than about 2 cm -3 . In the warmer wave-cloud (T (approx.)eq --37^\circC) relatively large ice number densities were observed (20--40 cm -3 . Our model calculations suggest that these large number densities are only possible if liquid droplets were activated at the cloud leading-edge, followed by subsequent homogeneous freezing. If sulfate aerosols had frozen before liquid droplets could be activated, then the peak ice crystal number density should have been less than 10 cm -3 .

Jensen, E. J.↗
NASA NTRS1997

Dynamics of Rocky Mountain Lee Waves Observed During Success

On two days during SUCCESS, the DC-8 sampled wave clouds which formed downstream of the ridges east of the Rocky Mountains. Wave morphology for both flights is deduced from temperature and 3-dimensional wind measurements from the MMS, isentrope profiles from the MTP, and linear perturbation theory. The waves observed on 960430 are smaller and found to be decaying with altitude, while the waves sampled on 960502 are vertically propagating and consist of larger, multiple wave scales. Wave orientations are consistent with the underlying topography and regions of high ice crystal concentration. Updraft velocities were estimated from the derived wave properties and are consistent with MMS vertical winds.

Dean-Day, J.↗
NASA NTRS1998

Mesoscale Variability in SUCCESS Data

Analysis of meteorological, chemical and microphysical data from the airborne SUCCESS (SUbsonic aircraft Contrail and Cloud Effects Special Study) mission is reported. Careful analysis of the complex DC-8 flight pattern of May 2, 1996 reveals 19 linear flight segments within six main geographical areas, which we have analyzed. Significant mountain wave activity is revealed in the data from the MMS (Meteorology Measurement System) and MTP (Microwave Temperature Profiler) instruments on the DC-8, which resembles previous observations of mountain wave structures near Boulder, Colorado. Strong mountain-wave-induced upwelling downwind of the Rockies is noted. Turbulence is also noted in regions of the mountain wave consistent with overturning near the tropopause. Zonal winds recorded on the ER-2 are shown to be consistent with mountain wave breaking at or near critical levels in the stratosphere, consistent with the strong turbulence reported by the pilot during the ER-2 flight. These observations have been supported with spectral analyses and modeling studies. 'Postcasts' of mountain wave activity on May 2, 1996 using the Naval Research Laboratory Mountain Wave Forecast Model predicts both strong mountain wave activity near the tropopause and strong mountain-wave-induced turbulence in the stratosphere.

Eckermann, Stephen D.↗
NASA NTRS2003

Successes and Challenges of Incompressible Flow Simulation

During the past thirty years, numerical methods and simulation tools for incompressible flows have been advanced as a subset of CFD discipline. Even though incompressible flows are encountered in many areas of engineering, simulation of compressible flow has been the major driver for developing computational algorithms and tools. This is probably due to rather stringent requirements for predicting aerodynamic performance characteristics of flight vehicles, while flow devices involving low speed or incompressible flow could be reasonably well designed without resorting to accurate numerical simulations. As flow devices are required to be more sophisticated and highly efficient, CFD tools become indispensable in fluid engineering for incompressible and low speed flow. This paper is intended to review some of the successes made possible by advances in computational technologies during the same period, and discuss some of the current challenges.

Kwak, Dochan↗
NASA NTRS2002

Continuous In Vitro Evolution of a Ribozyme that Catalyzes Three Successive Nucleotidyl Addition Reactions

Variants of the class I ligase ribozyme, which catalyzes joining of the 3' end of a template bound oligonucleotide to its own 5' end, have been made to evolve in a continuous manner by a simple serial transfer procedure that can be carried out indefinitely. This process was expanded to allow the evolution of ribozymes that catalyze three successive nucleotidyl addition reactions, two template-directed mononucleotide additions followed by RNA ligation. During the development of this behavior, a population of ribozymes was maintained against an overall dilution of more than 10(exp 406). The resulting ribozymes were capable of catalyzing the three-step reaction pathway, with nucleotide addition occurring in either a 5' yieldig 3' or a 3' yielding 5' direction. This purely chemical system provides a functional model of a multi-step reaction pathway that is undergoing Darwinian evolution.

McGinness, Kathleen E.↗