SEARCH · Search NASA

Results for “TELL”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22

All sources NASA NTRS DOE OSTI

NASA NTRS2001

Deep Space 1 Ion Engine Completed a 3-Year Journey

A xenon ion engine and power processor system, which was developed by the NASA Glenn Research Center in partnership with the Jet Propulsion Laboratory and Boeing Electron Dynamic Devices, completed nearly 3 years of operation aboard the Deep Space 1 spacecraft. The 2.3-kW ion engine, which provided primary propulsion and two-axis attitude control, thrusted for more than 16,000 hr and consumed more than 70 kg of xenon propellant. The Deep Space 1 spacecraft was launched on October 24, 1998, to validate 12 futuristic technologies, including the ion-propulsion system. After the technology validation process was successfully completed, the Deep Space 1 spacecraft flew by the small asteroid Braille on July 29, 1999. The final objective of this mission was to encounter the active comet Borrelly, which is about 6 miles long. The ion engine was on a thrusting schedule to navigate the Deep Space 1 spacecraft to within 1400 miles of the comet. Since the hydrazine used for spacecraft attitude control was in short supply, the ion engine also provided two-axis attitude control to conserve the hydrazine supply for the Borrelly encounter. The comet encounter took place on September 22, 2001. Dr. Marc Rayman, project manager of Deep Space 1 at the Jet Propulsion Laboratory said, "Deep Space 1 plunged into the heart of the comet Borrelly and has lived to tell every detail of its spinetingling adventure! The images are even better than the impressive images of comet Halley taken by Europe's Giotto spacecraft in 1986." The Deep Space 1 mission, which successfully tested the 12 high-risk, advanced technologies and captured the best images ever taken of a comet, was voluntarily terminated on December 18, 2001. The successful demonstration of the 2-kW-class ion propulsion system technology is now providing mission planners with off-the-shelf flight hardware. Higher power, next generation ion propulsion systems are being developed for large flagship missions, such as outer planet explorers and sample-return missions.

Sovey, James S.↗

NASA NTRS2005

Effects of Nuclear Interactions on Accuracy of Space Radiation Transport

Space radiation risk to astronauts and electronic equipments is one major obstacle in long term human space explorations. Space radiation transport codes have been developed to calculate radiation effects behind materials in human missions to the Moon, Mars or beyond. We study how nuclear fragmentation processes affect the accuracy of predictions from such radiation transport. In particular, we investigate the effects of fragmentation cross sections at different energies on fluxes, dose and dose-equivalent from galactic cosmic rays behind typical shielding materials. These results tell us at what energies nuclear cross sections are the most important for radiation risk evaluations, and how uncertainties in our knowledge about nuclear fragmentations relate to uncertainties in space transport predictions.

Lin, Zi-Wei↗

NASA NTRS2005

STS-114: Discovery Post MMT Briefing

Wayne Hale, Space Shuttle Deputy Program Manager and Steve Poulos, Manager Orbit Project Office at Johnson Space Center is seen during a post Mission Management Team (MMT) briefing. The purpose of this briefing is to talk about the status of the Space Shuttle Discovery Orbiter, the Thermal Protection System (TPS) and the External Tank. Hale presents pictures of the missing foam off of the Hydrogen Protuberance Air Load (PAL) ramp and trajectory debris particles. Poulos explains in detail diagrams of the reinforced carbon-carbon system, possible scuff on the wing panel, coating damage, protruding gap filler and damaged tile blanket. Poulos tells what concerns him the most in terms of tile damage to the Space Shuttle Discovery.

Source record↗

NASA NTRS2005

How Space Radiation Risk from Galactic Cosmic Rays at the International Space Station Relates to Nuclear Cross Sections

Space radiation risk to astronauts is a major obstacle for long term human space explorations. Space radiation transport codes have thus been developed to evaluate radiation effects at the International Space Station (ISS) and in missions to the Moon or Mars. We study how nuclear fragmentation processes in such radiation transport affect predictions on the radiation risk from galactic cosmic rays. Taking into account effects of the geomagnetic field on the cosmic ray spectra, we investigate the effects of fragmentation cross sections at different energies on the radiation risk (represented by dose-equivalent) from galactic cosmic rays behind typical spacecraft materials. These results tell us how the radiation risk at the ISS is related to nuclear cross sections at different energies, and consequently how to most efficiently reduce the physical uncertainty in our predictions on the radiation risk at the ISS.

Lin, Zi-Wei↗

NASA NTRS2005

Instrumentation and Measurements for Electron Emission from Charged Insulators

The electron was first discovered in 1898 by Sir John Joseph Thomson and has since been the subject of detailed study by nearly every scientific discipline. At nearly the same time Heinrich Rudolf Hertz conducted a series of experiments using cathode tubes, high potentials and ultraviolet light. When applying a large potential to a cathode he found that an arching event across the metal plates would occur. In addition, when shining an ultraviolet light on the metal he found that less potential was required to induce the spark. This result, taken together with other electrical phenomena brought about by the shining of light upon metal and was eventually termed the photoelectric effect. The work of Thomson and Hertz represent the beginning of electron emission studies and a body of ideas that pervade nearly all aspects of physics. In particular these ideas tell us a great deal about the nature of physical interactions within solids. In this thesis we will focus on the emission of electrons induced by an incident electron source over a range of energies, in which one can observe changes in emitted electron flux and energy distribution. In particular, when energetic particles impinge on a solid they can impart their energy, exciting electrons within the material. If this energy is sufficient to overcome surface energy barriers such as the work function, electron affinity or surface charge potential, electrons can escape from the material. The extent of electron emission from the material can be quantified as the ratio of incident particle flux to emitted particle flux, and is termed the electron yield.

Sim, Alec M.↗

NASA NTRS2006

The Character and Variability of the Eta Carinae Wind Lines

The binarity of Eta Carinae has been debated for a long time. We have searched for more evidence for a companion star in a spectroscopic investigation of the Eta Carinae stellar wind lines, using moderate spectral and high angular resolution HST/STIS data. Over Eta Carinae's 5.54 year spectroscopic period many of the observable wind lines in the NUV/Optical spectral region exhibit peculiar line profiles with unusual velocity shifts relative to the system velocity. Some of the lines are exclusively blue-shifted over the entire cycle. Their ionization/excitation imply formation not in the stellar wind but rather in the interface between the two massive stars. We have analyzed velocity and intensity variations over the spectroscopic period and interpreted what the variations tell us about the geometry of the nebular structure close to Eta Carinae.

Nielsen, K. E.↗

NASA NTRS2006

Remote sensing of tropospheric constituents by OMI on the EOS Aura satellite

The Ozone Monitoring Instrument (OMI) was launched on NASA's EOS Aura satellite in July 2004. This instrument was built in the Netherlands with collaboration with Finland. The science data products are being developed jointly by scientists from the three countries. OMI is the first instrument to combine the high spatial resolution daily global mapping capability of TOMS with high spectral resolution measurements necessary for retrieving a number of trace gases of relevance to atmospheric chemistry, using techniques pioneered by GOME. In this talk I will show what our planet looks like at UV wavelengths and what these data can tell us about the effects of human activities on global air quality and climate.

Bhartia, Pawan K.↗

NASA NTRS2006

Normal and Starburst Galaxies in Deep X-ray Surveys

Cardiff, A. Hornschemeier↗

NASA NTRS2006

A Structural Characterization of Temporal Dynamic Controllability

An important issue for temporal planners is the ability to handle temporal uncertainty. Recent papers have addressed the question of how to tell whether a temporal network is Dynamically Controllable, i.e., whether the temporal requirements are feasible in the light of uncertain durations of some processes. Previous work has presented an O(N5) algorithm for testing this property. Here, we introduce a new analysis of temporal cycles that leads to an O(N4) algorithm.

Morris, Paul↗

NASA NTRS2005

Expanding the Frontiers of Knowledge

So space is supremely hostile, but we know this. But when we ask what is the cost of human space missions, we need to consider as many contingencies as possible. This is important because we want to do more than send people on one-way trips, we want to be able to bring astronauts back. So if exploration is what really matters and not just pride of nation, then perhaps we should genetically engineer a version of ourselves that can survive the hostile environments of space. We've got cloning. We're inside the genome. Let s just do it. Well in fact, we ve done that already. Yes, we have emissaries of ourselves that survive the hazards of space; they re called robots. You don t have to feed them or bring them back, and they don t complain if you lose them in space. So my concern is if costs turn out to be what they have historically been and the time to execute programs lasts as long as it historically has, then I am not convinced that economic cycles and political cycles will allow such programs to survive if they do not satisfy one of these three criteria. The record of history tells us this, unless somehow you want to believe that we are different today than 6,000 years of our predecessors.

deGrasse Tyson, Neil↗

NASA NTRS2006

Critical Issues in the History of Spaceflight

At a May 1981 "Proseminar in Space History"held at the Smithsonian Institution's National Air and Space Museum (NASM) in Washington, DC, historians came together to consider the state of the discipline of space history. It was an historic occasion. The community of scholars interested in the history of spaceflight was not large; previously, well-meaning but untrained aficionados consumed with artifacts had dominated the field, to the exclusion of the larger context. At a fundamental level, this proseminar represented a "declaration of independence" for what might be called the "new aerospace history." In retrospect, it may be interpreted as marking the rise of space history as a recognizable subdiscipline within the field of U.S. history. Bringing together a diverse collection of scholars to review the state of the art in space history, this proseminar helped in a fundamental manner to define the field and to chart a course for future research. Its participants set about the task of charting a course for collecting, preserving, and disseminating the history of space exploration within a larger context of space policy and technology. In large measure, the course charted by the participants in this 1981 proseminar aided in advancing a very successful agenda of historical research, writing, and understanding of space history. Not every research project has yielded acceptable results, nor can it be expected to do so, but the sum of the effort since 1981 has been impressive. The opportunities for both the exploration of space and for recording its history have been significant. Both endeavors are noble and aimed at the enhancement of humanity. Whither the history of spaceflight? Only time will tell. But there has been an emergent "new aerospace history" of which space history is a central part that moves beyond an overriding concern for the details of the artifact to emphasize the broader role of the spacecraft. More importantly, it emphasizes the whole technological system, including not just the vehicle but also the other components that make up the aerospace climate, as an integral part of the human experience. It suggests that many unanswered questions spur the development of flight and that inquisitive individuals seek to know that which they do not understand.

Dick, Steven J.↗

NASA NTRS2006

Normal and Starburst Galaxies in Deep X-ray Surveys

This talk will cover progress of the last several years in unraveling the nature of normal and starburst galaxies in deep X-ray surveys. This includes discussion of the normal galaxy X-ray Luminosity Function in deep field and cluster surveys and what it tells us about the binary populations in galaxies. The utility of broad band X-ray emission, especially as compared to other multiwavelength measurements of current/recent star formation, will be reviewed. These broad band X-ray measurements of star formation are based upon X-ray/Star Formation Rate correlations that span the currently available redshift range (0 < z < 1). I will also discuss new efforts underway to systematically characterize the X-ray emission from galaxies in group and cluster environments, including a new effort underway in the Coma cluster of galaxies. I will finish with discussion of the redshift frontier for studies of X-ray star formation, currently 2 approx.4, where the UV-selected Lyman Break galaxies are the best glimpse we have into X-ray emission from star formation in the early Universe. Lyman Break galaxies are of particular interest due to the overlap in basic properties with starburst galaxies in the more local Universe. Understanding the outflows in such starburst galaxies is of critical importance to constraining the "stellar" portion of cosmic feedback. The talk will close with a brief discussion of distant normal galaxy science with future X-ray observatories such as the upcoming Con-X/XEUS mission(s).

Hornschemeier, Ann↗

NASA NTRS1996

Jet Propulsion Laboratories in Space: The Production of Astrophysical Jets by Magnetic Accretion Disks, and a Super-Eddington Wind Model for the Early Stages of GROJ1455-40

Measurements of the properties of gravitational lenses have the power to tell us what sort of universe we live in. The brightest known radio Einstein ring/gravitational lens PKS 1830-211, whilst obscured by our galaxy at optical wavelengths, has recently provided a lensing galaxy redshift of 0.89 through the detection of a new absorption feature, most likely due to neutral hydrogen in a second redshift system at z=0.19.

PKS 1830-211↗

NASA NTRS1996

PKS 1830-211: A Possible Compound Gravitational Lens

Measurements of the properties of gravitational lenses have the power to tell us what sort of universe we live in. The brightest known radio Einstein ring/gravitational lens PKS 1830-211, whilst obscured by our Galaxy at optical wavelengths, has recently provided a lensing galaxy redshift of 0.89 through the detection of molecular absorption in the millimetre waveband.

new absorption feature lensing galaxy redshift sec↗

NASA NTRS1995

On the Feasibility of Satellite Altimeter Tomography

The time-varying field of sea surface height (SSH) reflects a large number of dynamical processes including a broad range of baroclinic waves. Inertia-gravity (IG) and Rossby waves (RW) are readily detected in power spectra F(k) of SSH spatial variations, as well as in wavenumber-frequency spectral, ,k), and autocorrelation functions W(). these statistical characteristics contain information on dynamical processes in the upper thermocline. We show that the well-known 3-segment shape of 1-d spectra (based on SSH variations along satellite tracks) is determined by the Internal Rossby radius of deformation and by the degree of nonlinearity of baroclinic IG waves. Analyzing altimeter-based spectra of SSH variations in the light of a recently proposed theory for IG wave turbulence, we demonstrate that baroclinic IG waves are typically highly nonlinear. For a number of mid- and high-latitude regions, the internal Rossby radius and the wave nonlinearity are estimated from T/P data and shown to agree with expected values. The degree of the wave nonlinearity is of great practical interest. In particular, it tells us about the intensity of internal wave breaking. Furthermore, estimating the velocity of baroclinic RW we derive additional information on the upper layer stratification. These experiments point to the feasibility of using observed SSH field statistics (such F(k) and W()) to monitor properties of and dynamical processes in the upper mixed layer of the ocean.

Satellite Altimeter↗

NASA NTRS2005

Mars Exploration Rover surface operations: driving opportunity at Meridiani Planum

This paper will detail the experience of driving Opportunity through this alien landscape from the point of view of the Rover Planners, the people who tell the rover where to drive and how to use its robotic arm.

robot autonomy↗

NASA NTRS2005

Formulation refinement and access to space for the ST8 mission

This paper tells the story of the steps taken in the formulation refinement of the ST8 mission leading to its establishment as a formal flight project, with some insights and comments on the benefits and risks of the approach.

space technology flight validation↗

NASA NTRS2004

From hybrid systems to universal plans via domain compilation

While universal plans tell a system how to reach a goal regardless of what state it is in, such plans are typically too large to represent. Hybrid systems execute plans where each action is implemented to robustly produce effects if the world does not stray outside the action's control envelopes.

embedded real-time planning↗