Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “FUNDAMENTAL”

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.

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

At least 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

(abstract) Fundamental Mechanisms of Electrode Kinetics and Alkali Metal Atom Transport at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

The mechanisms of electrode kinetics and mass transport of alkali metal oxidation and alkali metal cation reduction at the solid electrolyte/porous electrode boundary as well as alkali metal transport through porous metal electrodes has important applications in optimizing device performance in alkali metal thermal to electric converter (AMTEC) cells which are high temperature, high current density electrochemical cells. Basic studies of these processes also affords the opportunity to investigate a very basic electrochemical reaction over a wide range of conditions; and a variety of mass transport modes at high temperatures via electrochemical techniques. The temperature range of these investigations covers 700K to 1240K; the alkali metal vapor pressures range from about 10(sup -2) to 10(sup 2) Pa; and electrodes studied have included Mo, W, Mo/Na(sub 2)MoO(sub 4), W/Na(sub 2)WO(sub 4), WPt(sub x), and WRh(sub x) (1.0 < x < 6.0 ) with Na at Na-beta'-alumina, and Mo with K at K-beta'-alumina. Both liquid metal/solid electrolyte/alkali metal vapor and alkali metal vapor/solid electrolyte/vapor cells have been used to characterize the reaction and transport processes. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes.

electrode kinetics thermal to electric conversion ↗
NASA NTRS1995

Advanced Laser Processing of Materials--Fundamentals and Applications

Preparation of amorphous thin films in semiconductors and their transition to the crystalline phase may apply to switching devices. Surfaces of single crystal samples of bulk In2Se3 and thin films of InSe were treated using an excimer laser, and microscopic examination showed the treated portions of the surface had become amorphous. Film samples of InSe were laser-treated like the bulk samples. Examination of these treated flims showed shifts in the optical transmittance spectra as well as surface morphology changes.

amorphous thin films semiconductors crystalline ph↗
NASA NTRS1994

Fundamental Aspects of Ion Transport in Solid Electrolytes

Solid electrolytes (also termed as superionic solids or fast ion conductors) are characterized by high electrical conductivity, comparable to concentrated liquid electrolytes or even molten salt electrolytes, made possible by rapid transport of ions in the crystalline lattice.

electrochemistry solid state ionics superionic sol↗
NASA NTRS2005

Use of New Communication Technologies to Change NASA Safety Culture: Incorporating the Use of Blogs as a Fundamental Communications Tool

The purpose of this paper is to explore an innovative approach to culture change at NASA that goes beyond reorganizations, management training, and a renewed emphasis on safety. Over the last five years, a technological social revolution has been emerging from the internet. Blogs (aka web logs) are transforming traditional communication and information sharing outlets away from established information sources such as the media. The Blogosphere has grown from zero blogs in 1999 to approximately 4.5 million as of November 2004 and is expected to double in 2005. Blogs have demonstrated incredible effectiveness and efficiency with regards to affecting major military and political events. Consequently, NASA should embrace the new information paradigm presented by blogging. NASA can derive exceptional benefits from the new technology as follows: 1) Personal blogs can overcome the silent safety culture by giving voice to concerns or questions that are not well understood or seemingly inconsequential to the NASA community at-large without the pressure of formally raising a potential false alarm. Since blogs can be open to Agency-wide participation, an incredible amount of resources from an extensive pool of experience can focus on a single issue, concern, or problem and quickly vetted, discussed and assessed for feasibility, significance, and criticality. The speed for which this could be obtained cannot be matched through any other process or procedure currently in use. 2) Through official NASA established blogs, lessons learned can be a real-time two way process that is formed and implemented from the ground level. Data mining of official NASA blogs and personal blogs of NASA personnel can identify hot button issues and concerns to senior management. 3) NASA blogs could function as a natural ombudsman for the NASA community. Through the recognition of issues being voiced by the community and taking a proactive stance on those issues, credibility within NASA Management can be restored. For NASA to harness the capabilities of blogs, NASA must develop an Agency-wide policy on blogging to encourage use and provide guidance. This policy should describe basic rules of conduct and content as well as a policy of non-retribution and/or anonymity. The Agency must provide sever space within their firewalls, provide appropriate software tools, and promote blogs in newsletters and official websites. By embracing the use of blogs, a potential pool of 19,000 experts could be available to address each posted safety issue, concern, problem, or question. Blogs could result in real NASA culture change.

Huls, Dale thomas↗
NASA NTRS2007

A Review of Hypersonics Aerodynamics, Aerothermodynamics and Plasmadynamics Activities within NASA's Fundamental Aeronautics Program

The research program of the aerodynamics, aerothermodynamics and plasmadynamics discipline of NASA's Hypersonic Project is reviewed. Details are provided for each of its three components: 1) development of physics-based models of non-equilibrium chemistry, surface catalytic effects, turbulence, transition and radiation; 2) development of advanced simulation tools to enable increased spatial and time accuracy, increased geometrical complexity, grid adaptation, increased physical-processes complexity, uncertainty quantification and error control; and 3) establishment of experimental databases from ground and flight experiments to develop better understanding of high-speed flows and to provide data to validate and guide the development of simulation tools.

Salas, Manuel D.↗
NASA NTRS2006

Testing Fundamental Properties of Ionic Liquids for Colloid Microthruster Applications

NASA's New Millennium Program is scheduled to test a Disturbance Reduction System (DRS) on Space Technology 7 (ST7) as part of the European Space Agency's (ESA's) LISA Pathfinder Mission in late 2009. Colloid Micronewton Thrusters (CMNTs) will be used to counteract forces, mainly solar photon pressure, that could disturb gravitational reference sensors as part of the DRS. The micronewton thrusters use an ionic liquid, a room temperature molten salt, as propellant. The ionic liquid has a number of unusual properties that have a direct impact on thruster design. One of the most important issues is bubble formation before and during operation, especially during rapid pressure transitions from atmospheric to vacuum conditions. Bubbles have been observed in the feed system causing variations in propellant flow rate that can adversely affect thruster control. Bubbles in the feed system can also increase the likelihood that propellant will spray onto surfaces that can eventually lead to shorting high voltage electrodes. Two approaches, reducing the probability of bubble formation and removing bubbles with a new bubble eliminator device in the flow system, were investigated at Busek Co., Inc. and the Jet Propulsion Laboratory (JPL) to determine the effectiveness of both approaches. Results show that bubble formation is mainly caused by operation at low pressure and volatile contaminants in the propellant coming out of solution. A specification for the maximum tolerable level of contamination has been developed, and procedures for providing system cleanliness have been tested and implemented. The bubble eliminator device has also been tested successfully and has been implemented in recent thruster designs at Busek. This paper focuses on the propellant testing work at JPL, including testing of a breadboard level bubble eliminator device.

bubble formation↗
NASA NTRS2007

Fundamentals of Aerospace Medicine: Cosmic Radiation

Cosmic rays were discovered in 1911 by the Austrian physicist, Victor Hess. The planet earth is continuously bathed in high-energy galactic cosmic ionizing radiation (GCR), emanating from outside the solar system, and sporadically exposed to bursts of energetic particles from the sun referred to as solar particle events (SPEs). The main source of GCR is believed to be supernovae (exploding stars), while occasionally a disturbance in the sun's atmosphere (solar flare or coronal mass ejection) leads to a surge of radiation particles with sufficient energy to penetrate the earth's magnetic field and enter the atmosphere. The inhabitants of planet earth gain protection from the effects of cosmic radiation from the earth s magnetic field and the atmosphere, as well as from the sun's magnetic field and solar wind. These protective effects extend to the occupants of aircraft flying within the earth s atmosphere, although the effects can be complex for aircraft flying at high altitudes and high latitudes. Travellers in space do not have the benefit of this protection and are exposed to an ionizing radiation field very different in magnitude and quality from the exposure of individuals flying in commercial airliners. The higher amounts and distinct types of radiation qualities in space lead to a large need for understanding the biological effects of space radiation. It is recognized that although there are many overlaps between the aviation and the space environments, there are large differences in radiation dosimetry, risks and protection for airline crew members, passengers and astronauts. These differences impact the application of radiation protection principles of risk justification, limitation, and the principle of as low as reasonably achievable (ALARA). This chapter accordingly is divided into three major sections, the first dealing with the basic physics and health risks, the second with the commercial airline experience, and the third with the aspects of cosmic radiation appertaining to space travel including future considerations.

Bagshaw, Michael↗
NASA NTRS2007

A Deeper Look at the Fundamentals of Heterodyne Detection Requirements

We generally accept the experimentally observed criteria for heterodyne detections that the two waves that are mixed must (i) be collinear, (ii) have matched wave fronts and (iii) cannot be orthogonally polarized. We have not found in the literature adequate physical explanations for these requirements. The purpose of this paper is to find deeper physical understanding of the coherent heterodyne detection processes that could lead to better coherent laser radar system designs1. We find that there are a number of unresolved paradoxes in classical and quantum optics regarding the definitions and understanding of the "interference" and "coherence" properties of light, which are attributed as essentially due to inherent properties of the EM waves. A deeper exploration indicates that it is the various quantum mechanical properties of the detecting material dipoles that make light detectable (visible, or measurable) to us. Accordingly, all the properties that we generally attribute to only light, are in reality manifestations of collective properties of dipole-light interactions. "Interference" and "coherence" can be better understood in terms of this mutual interaction, followed by energy absorption by the dipoles from EM wave fields, manifesting in some measurable transformation of the detecting dipoles. Light beams do not interfere by themselves. The superposition effects due to light beams become manifest through the response characteristics of the detecting dipoles. In this paper, we will show some preliminary expe rimental results that clearly demonstrate that the heterodyning wave fronts have quantitative degradation in signal generation as the angle between them deviates from perfect collinearity. Subsequently, we will propose a hypothesis for this behavior. We will present experimental data establishing that the so called incoherent light can be detected through heterodyne mixing as long as the pulse length contained in the "incoherent" light is longer than the response time of the detector. We will also present a correspondingly better interpretation of two distinguishable coherence properties, temporal coherence and spectral coherence. Our investigation provides a deeper insight into how to rela x various system requirements for heterodyne detection and accordingly develop systems that are simpler, more reliable and lower in cost. Also, we believe that engineering of detector architecture by appropriately modifying dipole behavior using emerging nanotechnology to optimize heterodyne efficiency will be advantageous.

Roychoudhuri, Chandrasekhar↗