Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Description”

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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

A description and evaluation of TIMER: A time-based terminal flow-control concept

A description of a time-based ATC concept called TIMER (Traffic Intelligence for the Management of Efficient Runway-scheduling) and the results of a fast time and real time computer evaluation are presented. The concept was designed to improve the efficiency of extended terminal area operations (en route approach, transition, and terminal flight to the runway). TIMER integrates en route metering, fuel efficient cruise and profile descents, terminal sequencing and spacing together with computer-generated controller aids, in order to fully use runway capacity and improve efficiency of delay absorption. The concept, by using simplified aircraft models, accommodates both 4-D and non 4-D equipped aircraft and is designed for integration into the manual, voice linked ATC system in an evolutionary manner and still be able to accommodate proposed system upgrade features such as data link and further ground automation. Fast time and real time computer simulation results identify and show the effects and interactions of such key variables as horizon of control, metering fix and final approach delivery time errors, aircraft separation requirements, delay discounting, wind, flight technical error, and knowledge of aircraft final approach speed. The current ATC system has a runway interarrival-error standard deviation of approx. 26 seconds. Simulation results indicate that, with computer aiding, the runway interarrival-error standard deviation for non 4-D equipped traffic can be reduced to the region of 8 to 12 seconds if expected final approach speed is known; however, the reduction is only in the region of 16 to 20 seconds if expected final approach speed is unknown. Another major finding is that en route metering fix delivery-error standard deviation should be kept to less than a number somewhere between 35 to 45 seconds to achieve full runway capacity. This requirement implies the need for either airborne automation or assistance to the controller since the current manual performance in today's en route metering environment is in the order of 1.5 minutes.

Credeur, Leonard↗
NASA NTRS1990

A description of results from the handbook on signal fade degradation for the land mobile satellite service

During the period 1983 to 1988 a series of experiments were undertaken by the Electrical Engineering Research Laboratory of the University of Texas and the Applied Physics Laboratory of the Johns Hopkins University in which propagation impairment effects were investigated for the Land Mobile Satellite Service (LMSS). The results of these efforts have appeared in a number of publications, technical reports, and conference proceedings. The rationale for the development of a 'handbook' was to locate the salient and useful results in one single document for use by communications engineers, designers of planned LMSS communications systems, and modelers of propagation effects. Where applicable, the authors have also drawn from the results of other related investigations. A description of sample results contained in this handbook which should be available in the latter part of 1990 is given.

Goldhirsh, Julius↗
NASA NTRS1991

Description of the Large Gap Magnetic Suspension System (LGMSS) ground-based experiment

A description of the Large Gap Magnetic Suspension System (LGMSS) ground-based experiment is presented. The LGMSS provides five degrees of freedom control of a cylindrical suspended element which is levitated above a floor-mounted array of air core electromagnets. The uncontrolled degree of freedom is rotation about the long axis of the cylinder (roll). Levitation and control forces are produced on a permanent magnet core which is embedded in the cylinder. The cylinder also contains light emitting diodes (LEDs), assorted electrons, and a power supply. The LEDs provide active targets for an optical position measurement system which is being developed in-house at the Langley Research Center. The optical position measurement system will provide six degrees of freedom position information for the LGMSS control system.

Groom, Nelson J.↗
NASA NTRS1991

Description, characteristics and testing of the NASA airborne radar

Presented here is a description of a coherent radar scattermeter and its associated signal processing hardware, which have been specifically designed to detect microbursts and record their radar characteristics. Radar parameters, signal processing techniques and detection algorithms, all under computer control, combine to sense and process reflectivity, clutter, and microburst data. Also presented is the system's high density, high data rate recording system. This digital system is capable of recording many minutes of the in-phase and quadrature components and corresponding receiver gains of the scattered returns for selected spatial regions, as well as other aircraft and hardware related parameters of interest for post-flight analysis. Information is given in viewgraph form.

Jones, W. R.↗
NASA NTRS1991

Optical model description of momentum transfer in relativistic heavy ion collisions

An optical model description of momentum transfer in relativistic heavy ion collisions, based upon composite particle multiple scattering theory, is presented. The imaginary component of the complex momentum transfer, which comes from the absorptive part of the optical potential, is identified as the longitudinal momentum downshift of the projectile. Predictions of fragment momentum distribution observables are made and compared with experimental data. Use of the model as a tool for estimating collision impact parameters is discussed.

Khan, F.↗
NASA NTRS1990

Description and performance of a digital mobile satellite terminal

A major goal of the Mobile Satellite Experiment (MSAT-X) program at the Jet Propulsion Lab (JPL) is the development of an advanced digital terminal for use in land mobile satellite communication. The terminal has been developed to minimize the risk of applying advanced technologies to future commercial mobile satellite systems (MSS). Testing with existing L band satellites was performed in fixed, land mobile and aeronautical mobile environments. JPL's development and tests of its mobile terminal have demonstrated the viability of narrowband digital voice communications in a land mobile environment through geostationary satellites. This paper provides a consolidated description of the terminal architecture and the performance of its individual elements.

Lay, N.↗
NASA NTRS1992

Learning class descriptions from a data base of spectral reflectance with multiple view angles

A learning program has been developed which combines 'learning by example' with the generate-and-test paradigm to furnish a robust learning environment capable of handling error-prone data. The problem is shown to be capable of learning class descriptions from positive and negative training examples of spectral and directional reflectance data taken from soil and vegetation. The program, which used AI techniques to automate very tedious processes, found the sequence of relationships that contained the most important information which could distinguish the classes.

Kimes, Daniel S.↗
NASA NTRS1992

Description of the SSF PMAD DC testbed control system data acquisition function

The NASA LeRC in Cleveland, Ohio has completed the development and integration of a Power Management and Distribution (PMAD) DC Testbed. This testbed is a reduced scale representation of the end to end, sources to loads, Space Station Freedom Electrical Power System (SSF EPS). This unique facility is being used to demonstrate DC power generation and distribution, power management and control, and system operation techniques considered to be prime candidates for the Space Station Freedom. A key capability of the testbed is its ability to be configured to address system level issues in support of critical SSF program design milestones. Electrical power system control and operation issues like source control, source regulation, system fault protection, end-to-end system stability, health monitoring, resource allocation, and resource management are being evaluated in the testbed. The SSF EPS control functional allocation between on-board computers and ground based systems is evolving. Initially, ground based systems will perform the bulk of power system control and operation. The EPS control system is required to continuously monitor and determine the current state of the power system. The DC Testbed Control System consists of standard controllers arranged in a hierarchical and distributed architecture. These controllers provide all the monitoring and control functions for the DC Testbed Electrical Power System. Higher level controllers include the Power Management Controller, Load Management Controller, Operator Interface System, and a network of computer systems that perform some of the SSF Ground based Control Center Operation. The lower level controllers include Main Bus Switch Controllers and Photovoltaic Controllers. Power system status information is periodically provided to the higher level controllers to perform system control and operation. The data acquisition function of the control system is distributed among the various levels of the hierarchy. Data requirements are dictated by the control system algorithms being implemented at each level. A functional description of the various levels of the testbed control system architecture, the data acquisition function, and the status of its implementationis presented.

Baez, Anastacio N.↗
NASA NTRS1992

Framework Programmable Platform for the Advanced Software Development Workstation (FPP/ASDW). Demonstration framework document. Volume 2: Framework process description

In the second volume of the Demonstration Framework Document, the graphical representation of the demonstration framework is given. This second document was created to facilitate the reading and comprehension of the demonstration framework. It is designed to be viewed in parallel with Section 4.2 of the first volume to help give a picture of the relationships between the UOB's (Unit of Behavior) of the model. The model is quite large and the design team felt that this form of presentation would make it easier for the reader to get a feel for the processes described in this document. The IDEF3 (Process Description Capture Method) diagrams of the processes of an Information System Development are presented. Volume 1 describes the processes and the agents involved with each process, while this volume graphically shows the precedence relationships among the processes.

Mayer, Richard J.↗
NASA NTRS1992

Overview of Venus geology: Preliminary description of terrain units for Venus global geological mapping

Venus terrain units can be categorized on the basis of morphology, reflectivity, backscatter, roughness, and emissivity. Morphology can be inferred from Magellan left-looking nominal incidence angle image mosaics, right-looking coverage, and more limited left-looking stereo. The typical resolution is about 300 m down to about 120 m near periapsis in the cycle one nominal coverage. The scale of geologic mapping governs definition of mappable terrain units. Initial global mapping is being compiled at a scale of 1:50 million. At this scale, the smallest individual features that can be mapped are about 125 km. The categories of terrain types are plains, complex ridge terrain, features with morphology suggesting volcanic or volcano-tectonic origin, features interpreted to be tectonic in origin, crater units, and surficial units such as splotches and streaks. Brief descriptions of terrain units are provided.

Saunders, R. Stephen↗
NASA NTRS1991

Space transfer concepts and analysis for exploration missions. Implementation plan and element description document (draft final). Volume 3: Nuclear thermal rocket vehicle

This document presents the nuclear thermal rocket (NTR) concept design developed in support of the Space Transfer Concepts and Analysis for Exploration Missions (STCAEM) study. The evolution of the NTR concept is described along with the requirements, guidelines and assumptions for the design. Operating modes and options are defined and a systems description of the vehicle is presented. Artificial gravity configuration options and space and ground support systems are discussed. Finally, an implementation plan is presented which addresses technology needs, schedules, facilities and costs.

Source record↗
NASA NTRS1991

Space transfer concepts and analysis for exploration missions. Implementation plan and element description document (draft final). Volume 5: Nuclear electric propulsion vehicle

The nuclear electric propulsion (NEP) concept design developed in support of the Space Transfer Concepts and Analysis for Exploration Missions (STCAEM) study is presented. The evolution of the NEP concept is described along with the requirements, guidelines, and assumptions for the design. Operating modes and options are defined and a systems description of the vehicle is presented. Artificial gravity configuration options and space and ground support systems are discussed. Finally, an implementation plan is presented which addresses technology needs, schedules, facilities and costs.

Source record↗
NASA NTRS1991

Space transfer concepts and analysis for exploration missions. Implementation plan and element description document (draft final). Volume 4: Solar electric propulsion vehicle

This document presents the solar electric propulsion (SEP) concept design developed as part of the Space Transfer Concepts and Analysis for Exploration Missions (STCAEM) study. The evolution of the SEP concept is described along with the requirements, guidelines and assumptions for the design. Operating modes and options are defined and a systems description of the vehicle is presented. Artificial gravity configuration options and space and ground support systems are discussed. Finally, an implementation plan is presented which addresses technology needs, schedules, facilities, and costs.

Source record↗
NASA NTRS1991

Space transfer concepts and analysis for exploration missions. Implementation plan and element description document (draft final). Volume 6: Lunar systems

NASA's two Office of Space Flight (Code M) Space Transfer Vehicle (STV) contractors supported development of Space Exploration Initiative (SEI) lunar transportation concepts. This work treated lunar SEI missions as the far end of a more near-term STV program, most of whose missions were satellite delivery and servicing requirements derived from Civil Needs Data Base (CNDB) projections. Space Transfer Concepts and Analysis for Exploration Missions (STCAEM) began to address the complete design of a lunar transportation system. The following challenges were addressed: (1) the geometry of aerobraking; (2) accommodation of mixed payloads; (3) cryogenic propellant transfer in Low Lunar Orbit (LLO); (4) fully re-usable design; and (5) growth capability. The leveled requirements, derived requirements, and assumptions applied to the lunar transportation system design are discussed. The mission operations section includes data on mission analysis studies and performance parametrics as well as the operating modes and performance evaluations which include the STCAEM recommendations. Element descriptions for the lunar transportation family included are a listing of the lunar transfer vehicle/lunar excursion vehicle (LTV/LEV) components; trade studies and mass analyses of the transfer and excursion modules; advanced crew recovery vehicle (ACRV) (modified crew recovery vehicle (MCRV)) modifications required to fulfill lunar operations; the aerobrake shape and L/D to be used; and some costing methods and results. Commonality and evolution issues are also discussed.

Source record↗
NASA NTRS1991

Space transfer concepts and analysis for exploration missions. Implementation plan and element description document (draft final). Volume 2: Cryo/aerobrake vehicle

The cryogenic/aerobrake (CAB) and the cryogenic all-propulsive (CAP) concept designs developed in support of the Space Transfer Concepts and Analysis for Exploration Missions (STCAEM) study are presented. The evolution of the CAB and CAP concepts is described along with the requirements, guidelines and assumptions for the designs. Operating modes and options are defined and systems descriptions of the vehicles are presented. Artificial gravity configuration options and space and ground support systems are discussed. Finally, an implementation plan is presented which addresses technology needs, schedules, facilities, and costs.

Source record↗
NASA NTRS1993

A functional description of the Buffered Telemetry Demodulator (BTD)

This article gives a functional description of the buffered telemetry demodulator (BTD), which operates on recorded digital samples to extract the symbols from the received signal. The key advantages of the BTD are as follows: (1) its ability to reprocess the signal to reduce acquisition time; (2) its ability to use future information about the signal and to perform smoothing on past samples; and (3) its minimum transmission bandwidth requirement as each sub carrier harmonic is processed individually. The first application of the BTD would be the Galileo S-band contingency mission, where the signal is so weak that reprocessing to reduce the acquisition time is crucial. Moreover, in the event of employing antenna arraying with full spectrum combining, only the sub carrier harmonics need to be transmitted between sites, resulting in significant reduction in data rate transmission requirements. Software implementation of the BTD is described for various general-purpose computers.

Tsou, H.↗
NASA NTRS1993

Alternative descriptions of wave and particle aspects of the harmonic oscillator

The dynamical properties of the wave and particle aspects of the harmonic oscillator can be studied with the help of the time-dependent Schroedinger equation (SE). Especially the time-dependence of maximum and width of Gaussian wave packet solutions allow to show the evolution and connections of those two complementary aspects. The investigation of the relations between the equations describing wave and particle aspects leads to an alternative description of the considered systems. This can be achieved by means of a Newtonian equation for a complex variable in connection with a conservation law for a nonclassical angular momentum-type quantity. With the help of this complex variable, it is also possible to develop a Hamiltonian formalism for the wave aspect contained in the SE, which allows to describe the dynamics of the position and momentum uncertainties. In this case the Hamiltonian function is equivalent to the difference between the mean value of the Hamiltonian operator and the classical Hamiltonian function.

Schuch, Dieter↗