Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “First principles”

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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

A Comprehensive Reliability Methodology for Assessing Risk of Reusing Failed Hardware Without Corrective Actions with and Without Redundancy

This paper deals with the development of a reliability methodology to assess the consequences of using hardware, without failure analysis or corrective action, that has previously demonstrated that it did not perform per specification. The subject of this paper arose from the need to provide a detailed probabilistic analysis to calculate the change in probability of failures with respect to the base or non-failed hardware. The methodology used for the analysis is primarily based on principles of Monte Carlo simulation. The random variables in the analysis are: Maximum Time of Operation (MTO) and operation Time of each Unit (OTU) The failure of a unit is considered to happen if (OTU) is less than MTO for the Normal Operational Period (NOP) in which this unit is used. NOP as a whole uses a total of 4 units. Two cases are considered. in the first specialized scenario, the failure of any operation or system failure is considered to happen if any of the units used during the NOP fail. in the second specialized scenario, the failure of any operation or system failure is considered to happen only if any two of the units used during the MOP fail together. The probability of failure of the units and the system as a whole is determined for 3 kinds of systems - Perfect System, Imperfect System 1 and Imperfect System 2. in a Perfect System, the operation time of the failed unit is the same as that of the MTO. In an Imperfect System 1, the operation time of the failed unit is assumed as 1 percent of the MTO. In an Imperfect System 2, the operation time of the failed unit is assumed as zero. in addition, simulated operation time of failed units is assumed as 10 percent of the corresponding units before zero value. Monte Carlo simulation analysis is used for this study. Necessary software has been developed as part of this study to perform the reliability calculations. The results of the analysis showed that the predicted change in failure probability (P(sub F)) for the previously failed units is as high as 49 percent above the baseline (perfect system) for the worst case. The predicted change in system P(sub F) for the previously failed units is as high as 36% for single unit failure without any redundancy. For redundant systems, with dual unit failure, the predicted change in P(sub F) for the previously failed units is as high as 16%. These results will help management to make decisions regarding the consequences of using previously failed units without adequate failure analysis or corrective action.

Putcha, Chandra S.↗
NASA NTRS2002

High-Temperature Gas Sensor Array (Electronic Nose) Demonstrated

The ability to measure emissions from aeronautic engines and in commercial applications such as automotive emission control and chemical process monitoring is a necessary first step if one is going to actively control those emissions. One single sensor will not give all the information necessary to determine the chemical composition of a high-temperature, harsh environment. Rather, an array of gas sensor arrays--in effect, a high-temperature electronic "nose"--is necessary to characterize the chemical constituents of a diverse, high-temperature environment, such as an emissions stream. The signals produced by this nose could be analyzed to determine the constituents of the emission stream. Although commercial electronic noses for near-room temperature applications exist, they often depend significantly on lower temperature materials or only one sensor type. A separate development effort necessary for a high-temperature electronic nose is being undertaken by the NASA Glenn Research Center, Case Western Reserve University, Ohio State University, and Makel Engineering, Inc. The sensors are specially designed for hightemperature environments. A first-generation high-temperature electronic nose has been demonstrated on a modified automotive engine. This nose sensor array was composed of sensors designed for hightemperature environments fabricated using microelectromechanical-systems- (MEMS-) based technology. The array included a tin-oxide-based sensor doped for nitrogen oxide (NOx) sensitivity, a SiC-based hydrocarbon (CxHy) sensor, and an oxygen sensor (O2). These sensors operate on different principles--resistor, diode, and electrochemical cell, respectively--and each sensor has very different responses to the individual gases in the environment. A picture showing the sensor head for the array is shown in the photograph on the left and the sensors installed in the engine are shown in the photograph on the right. Electronics are interfaced with the sensors for temperature control and signal conditioning, and packaging designed for high temperatures is necessary for the array to survive the engine environment.

Hunter, Gary W.↗
NASA NTRS2008

Fpack and Funpack Utilities for FITS Image Compression and Uncompression

Fpack is a utility program for optimally compressing images in the FITS (Flexible Image Transport System) data format (see http://fits.gsfc.nasa.gov). The associated funpack program restores the compressed image file back to its original state (as long as a lossless compression algorithm is used). These programs may be run from the host operating system command line and are analogous to the gzip and gunzip utility programs except that they are optimized for FITS format images and offer a wider choice of compression algorithms. Fpack stores the compressed image using the FITS tiled image compression convention (see http://fits.gsfc.nasa.gov/fits_registry.html). Under this convention, the image is first divided into a user-configurable grid of rectangular tiles, and then each tile is individually compressed and stored in a variable-length array column in a FITS binary table. By default, fpack usually adopts a row-by-row tiling pattern. The FITS image header keywords remain uncompressed for fast access by FITS reading and writing software. The tiled image compression convention can in principle support any number of different compression algorithms. The fpack and funpack utilities call on routines in the CFITSIO library (http://hesarc.gsfc.nasa.gov/fitsio) to perform the actual compression and uncompression of the FITS images, which currently supports the GZIP, Rice, H-compress, and PLIO IRAF pixel list compression algorithms.

Pence, W.↗
NASA NTRS2014

James Webb Space Telescope: The First Light Machine

NASA James Webb Space Telescope (JWST) will search for the first luminous objects of the Universe to help answer fundamental questions about how the Universe came to look like it does today. At 6.5 meters in diameter, JWST will be the world's largest space telescope. Its architecture, e.g. aperture, wavelength range and operating temperature, is driven by JWST's science objectives. Introduction: Scheduled to start its 5 year mission after 2018, JWST will study the origin and evolution of galaxies, stars and planetary systems. Its science mission is to: Identify the first bright objects that formed in the early Universe, and follow the ionization history. Determine how galaxies form. Determine how galaxies and dark matter, including gas, stars, metals, overall morphology and active nuclei evolved to the present day. Observe the birth and early development of stars and the formation of planets. And, study the physical and chemical properties of solar systems for the building blocks of Life. Principle: To accomplish the JWST science objectives requires a larger aperture infrared cryogenic space telescope. A large aperture is required because the objects are very faint. The infrared spectral range is required because the objects are so far away that their ultraviolet and visible wavelength spectral lines are red-shifted into the infrared. Because the telescope is infrared, it needs to be cryogenic. And, because of the telescope is infrared, it must operate above the Earth's atmosphere, i.e. in space. JWST is probably the single most complicated mission that humanity has attempted. It is certainly the most difficult optical fabrication and testing challenge of our generation. The JWST 6.5 m diameter primary mirror is nearly a parabola with a conic constant of -0.9967 and radius of curvature at 30K of 15.880 m. The primary mirror is divided into 18 segments with 3 different prescriptions; each with its own off-axis distance and aspheric departure. The radius of curvature for all 18 segments must match to +/- 0.150 mm at 30K. JWST is diffraction limited at 2 micrometers which translates into a transmitted wavefront specification of 156 nm rms. Of that amount, 50 nm rms is allocated to the primary mirror. Each segment is allocated 22 nm rms surface error. At the start of the JWST program, the capability to make such a mirror did not exist. In 1996, NASA began a systematic and comprehensive mirror technology development effort which resulted in JWST. This program resulted in a qualified mirror fabrication process being approved in 2006. Today, all JWST primary mirror segments meet their requirements and are on schedule for a 2018 launch. The next step is system level assembly, integration and test. Ambient tests will be conducted at Goddard Space Flight Center and cryogenic system level testing will be performed in Chamber A at the Johnson Space Center.

Stahl, H. Philip↗
NASA NTRSDate not supplied

Achieving Resilient In-Flight Performance for Advanced Air Mobility through Simplified Vehicle Operations

A research and development (R&D) approach is proposed for developing and validating concepts and technologies to achieve vehicle autonomy goals of Advanced Air Mobility (AAM) through Simplified Vehicle Operations (SVO). The approach applies resilience-engineering and human-automation teaming (HAT) principles to a framework for defining vehicle-based functions for the management of missions and flight trajectories, focusing initially on the en route flight domain. To achieve the SVO goal of reducing pilot training requirements and thereby increasing the pilot pool for AAM, while at the same time promoting ever-safer operations, a framework for identifying essential functions is proposed. In this framework, functions are first categorized by high-level functional purpose (mission management, flightpath management, tactical operations, and vehicle control) and then subcategorized by attributes of resilient-performing systems (abilities to monitor, respond, learn, and anticipate). The categorization by functional purpose provides structure within which HAT designs can be holistically explored and total levels of human vs. automation responsibility can be varied. The subcategorization by resilient-system attributes provides a mechanism for capturing safety-critical functions that may not be codified in current operational procedures and training curricula, particularly those where humans proactively enhance safety in currently undocumented ways. An R&D approach consisting of seven strategies is proposed in which automation engineering and human-factors communities can collaborate in the research, development, and design of an SVO roadmap to enable the ambitious objectives of AAM.

AAM↗
NASA NTRS1973

Analysis of the feasibility of an experiment to measure carbon monoxide in the atmosphere

The feasibility of measuring atmospheric carbon monoxide from a remote platform using the correlation interferometry technique was considered. It has been determined that CO data can be obtained with an accuracy of 10 percent using this technique on the first overtone band of CO at 2.3 mu. That band has been found to be much more suitable than the stronger fundamental band at 4.6 mu. Calculations for both wavelengths are presented which illustrate the effects of atmospheric temperature profiles, inversion layers, ground temperature and emissivity, CO profile, reflectivity, and atmospheric pressure. The applicable radiative transfer theory on which these calculations are based is described together with the principles of the technique.

Bortner, M. H.↗
NASA NTRS1991

The width of fault zones in a brittle-viscous lithosphere: Strike-slip faults

A fault zone in an ideal brittle material overlying a very weak substrate could, in principle, consist of a single slip surface. Real fault zones have a finite width consisting of a number of nearly parallel slip surfaces on which deformation is distributed. The hypothesis that the finite width of fault zones reflects stresses due to quasistatic flow in the ductile substrate of a brittle surface layer is explored. Because of the simplicity of theory and observations, strike-slip faults are examined first, but the analysis can be extended to normal and thrust faulting.

Parmentier, E. M.↗
NASA NTRS1993

The mechanosensory calcium-selective ion channel: key component of a plasmalemmal control centre?

Mechanosensory calcium-selective ion channels probably serve to detect not only mechanical stress but also electrical, thermal, and diverse chemical stimuli. Because all stimuli result in a common output, most notably a shift in second messenger calcium concentration, the channels are presumed to serve as signal integrators. Further, insofar as second messenger calcium in turn gives rise to mechanical, electrical, and diverse chemical changes, the channels are postulated to initiate regulatory feedbacks. It is proposed that the channels and the feedback loops play a wide range of roles in regulating normal plant function, as well as in mediating disturbance of normal function by environmental stressors and various pathogens. In developing evidence for the physiological performance of the channel, a model for a cluster of regulatory plasmalemmal proteins and cytoskeletal elements grouped around a set of wall-to-membrane and transmembrane linkers has proved useful. An illustration of how the model might operate is presented. It is founded on the demonstration that several xenobiotics interfere both with normal channel behaviour and with gravitropic reception. Accordingly, the first part of the illustration deals with how the channels and the control system within which they putatively operate might initiate gravitropism. Assuming that gravitropism is an asymmetric expression of growth, the activities of the channels and the plasmalemmal control system are extrapolated to account for regulation of both rate and allometry of cell expansion. Finally, it is discussed how light, hormones, redox agents and herbicides could in principle affect growth via the putative plasmalemmal control cluster or centre.

NASA Program Space Biology↗
NASA NTRS1986

Distributions of (C-13)O emission in the disks of late-type spiral galaxies

In studies of molecular clouds in external galaxies, the distribution of (C-12)O emissivity as a function of radius in a galaxy has been employed to infer the surface density of molecular hydrogen with galactocentric radius. In principle, observations of more optically thin molecular species, such as (C-13)O, can be used as an alternative tracer of the mass of molecular hydrogen in a galaxy. Since the (C-13)O lines have a much lower opacity than the saturated, nearly thermalized (C-12)O lines, their intensity variations as a function of galactocentric radius are more readily interpreted in terms of gas density variations. The first strip maps of the (C-13)O distributions in six spiral galaxies are presented, and the (C-13)O and (C-12)O radial distributions are compared. Attention is given to the reliability of H2 masses and H2 distributions derived from (C-12)O data.

Young, J. S.↗
NASA NTRS1999

Electrodynamic Thrust Performance for Space Solar Satellite Applications

The use of spinning tethers to transfer payloads from low earth orbit (LEO) to geosynchronous earth orbit (GEO) has previously been considered for payload masses up to 4000 kg (4 MT). The construction of the solar power station requires a transfer of 22,568 MT per year from LEO to GEO. This is envisioned to be carried out in payload units of 20 MT or 40 MT, which implies a frequency of 1188 or 594 flights per year, respectively. We could say from the outset that the use of spinning tethers for such large payloads at such high launch frequencies does not appear promising. This is inherent in the principles of spinning tether transfer, which we will briefly sketch below. Somewhat different scenarios are possible, but the basic physics remains the same. We consider only a single stage from LEO to GTO tether system, since the complexity involved in phasing the launches, docking, and spinups for a two-stage system for so many payloads rules out a two-stage system, in our opinion. The payload must first be launched to LEO, where it docks with the tether launch platform and is connected to the tether. The tether (tens of kilometers long) is then deployed with the payload upward. In order to give the payload the velocity necessary to launch it into a geosynchronous transfer orbit (GTO), i.e., to impart the required Av, the tethered system must be spun up about the center of mass of the tether-platform-payload system. The two end masses (platform and payload) are driven to rotate about the center of mass of the tethered system. Both the final rotational velocity and the phasing of the tether spin have to be controlled so that payload is in the vertically up position at the perigee of the LEO and with the velocity required to achieve the GTO when it is released at that point. Upon release, the payload then goes into GTO, where it again requires an acceleration to reach GEO (circularization of the orbit). The platform goes into a lower orbit, from which it must be raised in order to be at the proper LEO for docking with another payload. For this scheme to make sense at all, the platform must be envisioned as having a solar powered electrical thrust system to regain LEO and to spin up the tethered system. Similarly, solar powered electrical propulsion would be used to circularize the orbit to GEO.

Estes, Robert D.↗
NASA NTRS2004

A Resonant Pulse Detonation Actuator for High-Speed Boundary Layer Separation Control

A variety of different types of actuators have been previously investigated as flow control devices. Potential applications include the control of boundary layer separation in external flows, as well as jet engine inlet and diffuser flow control. The operating principles for such devices are typically based on either mechanical deflection of control surfaces (which include MEMS flap devices), mass injection (which includes combustion driven jet actuators), or through the use of synthetic jets (diaphragm devices which produce a pulsating jet with no net mass flow). This paper introduces some of the initial flow visualization work related to the development of a relatively new type of combustion-driven jet actuator that has been proposed based on a pulse detonation principle. The device is designed to utilize localized detonation of a premixed fuel (Hydrogen)-air mixture to periodically inject a jet of gas transversely into the primary flow. Initial testing with airflow successfully demonstrated resonant conditions within the range of acoustic frequencies expected for the design. Schlieren visualization of the pulsating air jet structure revealed axially symmetric vortex flow, along with the formation of shocks. Flow visualization of the first successful sustained oscillation condition is also demonstrated for one configuration of the current test section. Future testing will explore in more detail the onset of resonant combustion and the approach to conditions of sustained resonant detonation.

Beck, B. T.↗
NASA NTRS1975

The development of a portable cardiac ultrasonoscope

This paper describes a new, portable, battery powered echocardioscope developed at the NASA-Ames Research Center in cooperation with the Stanford University School of Medicine. This instrument has three major advantages over existing equipment. First, it is compact and light weight for easy portability. Second, its DC operation makes it safer to use in remote settings where AC power is unavailable or in intensive care and neonatal units where AC instruments could present electrical hazards for the patient. Third, its design and packaging should enable it to sell for several thousand dollars less than presently marketed ultrasonoscopes. The cooperative development of this instrument, its principles of operation, and the significance of its unique features are presented.

Schmidt, G.↗
NASA NTRS1992

Advanced mechanisms for robotics

An overview of applied research and development at NASA-Goddard (GSFC) on mechanisms and the collision avoidance skin for robots is presented. First the work on robot end effectors is outlined, followed by a brief discussion on robot-friendly payload latching mechanisms and compliant joints. This, in turn, is followed by the collision avoidance/management skin and the GSFC research on magnetostrictive direct drive motors. Finally, a new project, the artificial muscle, is introduced. Each of the devices is described in sufficient detail to permit a basic understanding of its purpose, fundamental principles of operation, and capabilities. In addition, the development status of each is reported along with descriptions of breadboards and prototypes and their test results. In each case, the implications of the research for commercialization is discussed. The chronology of the presentation will give a clear idea of both the evolution of the R&D in recent years and its likely direction in the future.

Vranish, John M.↗
NASA NTRS1997

Numerical Schemes for the Hamilton-Jacobi and Level Set Equations on Triangulated Domains

Borrowing from techniques developed for conservation law equations, numerical schemes which discretize the Hamilton-Jacobi (H-J), level set, and Eikonal equations on triangulated domains are presented. The first scheme is a provably monotone discretization for certain forms of the H-J equations. Unfortunately, the basic scheme lacks proper Lipschitz continuity of the numerical Hamiltonian. By employing a virtual edge flipping technique, Lipschitz continuity of the numerical flux is restored on acute triangulations. Next, schemes are introduced and developed based on the weaker concept of positive coefficient approximations for homogeneous Hamiltonians. These schemes possess a discrete maximum principle on arbitrary triangulations and naturally exhibit proper Lipschitz continuity of the numerical Hamiltonian. Finally, a class of Petrov-Galerkin approximations are considered. These schemes are stabilized via a least-squares bilinear form. The Petrov-Galerkin schemes do not possess a discrete maximum principle but generalize to high order accuracy.

Barth, Timothy J.↗
NASA NTRS2009

Series-Coupled Pairs of Silica Microresonators

Series-coupled pairs of whispering-gallery-mode optical microresonators have been demonstrated as prototypes of stable, narrow-band-pass photonic filters. Characteristics that are generally considered desirable in a photonic or other narrow-band-pass filter include response as nearly flat as possible across the pass band, sharp roll-off, and high rejection of signals outside the pass band. A single microresonator exhibits a Lorentzian filter function: its peak response cannot be made flatter and its roll-off cannot be made sharper. However, as a matter of basic principle applicable to resonators in general, it is possible to (1) use multiple resonators, operating in series or parallel, to obtain a roll-off sharper, and out-of-band rejection greater, relative to those of a Lorentzian filter function and (2) to make the peak response (the response within the pass band) flatter by tuning the resonators to slightly different resonance frequencies that span the pass band. The first of the two microresonators in each series-coupled pair was a microtorus made of germania-doped silica (containing about 19 mole percent germania), which is a material used for the cores of some optical fibers. The reasons for choosing this material is that exposing it to ultraviolet light causes it to undergo a chemical change that changes its index of refraction and thereby changes the resonance frequency. Hence, this material affords the means to effect the desired slight relative detuning of the two resonators. The second microresonator in each pair was a microsphere of pure silica. The advantage of making one of the resonators a torus instead of a sphere is that its spectrum of whispering-gallery-mode resonances is sparser, as needed to obtain a frequency separation of at least 100 GHz between resonances of the filter as a whole.

Savchenkov, Anatoliy↗
NASA NTRS1982

Can we detect antimatter from other galaxies

A novel particle detection technique employing well established principles of high order quantum electrodynamics for searching for antimatter in cosmic rays is described, and shown to have both collecting power and resolution superior to conventional alternatives. By taking into account various estimates of the metagalactic cosmic-ray energy density, and the possible modulation of metagalactic cosmic rays by a galactic wind within the framework of the dynamical halo model, it is shown that the experiment proposed would be the first to be sensitive to the presence of extragalactic antimatter.

Ahlen, S. P.↗
NASA NTRS1985

Application of TVD schemes for the Euler equations of gas dynamics

Highly accurate and yet stable shock-capturing finite difference schemes have been designed for the computation of the Euler equations of gas dynamics. Four different principles for the construction of high resolution total variation diminishing (TVD) schemes are available, including hybrid schemes, a second-order extension of Godunov's scheme by van Leer (1979), the modified flux approach of Harten (1983, 1984), and the numerical fluctuation approach of Roe (1985). The present paper has the objective to review the class of second-order TVD schemes via the modified flux approach. Attention is given to first-order TVD schemes, a second-order accurate explicit TVD scheme, the global order of accuracy of the second-order TVD scheme, extensions to systems and two-dimensional conservation laws, numerical experiments with a second-order explicit TVD scheme, implicit TVD schemes, and second-order implicit TVD schemes.

Yee, H. C.↗
NASA NTRS1997

Emergency Flight Control Using Only Engine Thrust and Lateral Center-of-Gravity Offset: A First Look

Normally, the damage that results in a total loss of the primary flight controls of a jet transport airplane, including all engines on one side, would be catastrophic. In response, NASA Dryden has conceived an emergency flight control system that uses only the thrust of a wing-mounted engine along with a lateral center-of-gravity (CGY) offset from fuel transfer. Initial analysis and simulation studies indicate that such a system works, and recent high-fidelity simulation tests on the MD-11 and B-747 suggest that the system provides enough control for a survivable landing. This paper discusses principles of flight control using only a wing engine thrust and CGY offset, along with the amount of CGY offset capability of some transport airplanes. The paper also presents simulation results of the throttle-only control capability and closed-loop control of ground track using computer-controlled thrust.

Burcham, Frank W., Jr.↗