Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “design considerations”

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 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

A semiconductor bridge ignited hot gas piston ejector

The topics are presented in viewgraph form and include the following: semiconductor bridge technology (SCB); SCB philosophy; technology transfer; simplified sketch of SCB; SCB processing; SCB design; SCB test assembly; 5 mJ SCB burst based on a polaroid photograph; micro-convective heat transfer hypothesis; SCB fire set; comparison of SCB and hot-wire actuators; satellite firing sets; logic fire set; SCB smart component; SCB smart firing set; semiconductor design considerations; and the adjustable actuator system.

Grubelich, M. C.↗
NASA NTRS1992

Innovative techniques for the production of energetic radicals for lunar processing including cold plasma processing of local planetary ores

Hydrogen reduction of ilmenite has been studied by a number of investigators as a potential means for recovery of oxygen from lunar soil. Interest in this process has always rested with the simplicity of the flow diagram and the utilization of established technology. Effective utilization of hydrogen in the reduction process at temperatures of 1200 C and below has always been disappointing and, as such, has led other investigators to focus attention on other systems. Effective utilization of hydrogen in the reduction of ilmenite can be significantly enhanced in the presence of a non-equilibrium hydrogen plasma. Ilmenite at solid specimen temperatures of 600 C to 970 C were reacted in a hydrogen plasma. Those experiments revealed that hydrogen utilization can be significantly enhanced. At a specimen temperature of 850 C the fraction of H2 reacted was 24 percent compared to the 7 percent theoretical limit calculated with thermodynamic theory for the same temperature. An added advantage for a hydrogen plasma involves further reduction of TiO2. Reduction of the iron oxide in ilmenite yields TiO2 and metallic iron as by products. Titanium forms a number of oxides including TiO, Ti2O3, Ti3O5 and the Magneli oxides (Ti4O7 to Ti50O99). In conventional processing of ilmenite with hydrogen it is possible to reduce TiO2 to Ti7O13 within approximately an hour, but with poor utilization of hydrogen on the order of one mole of H2 per thousand. In the cold or non-equilibrium plasma TiO2 can be rapidly reduced to Ti2O3 with hydrogen utilization exceeding 10 percent. Based on design considerations of the plasma reactor greater utilization of the hydrogen in the reduction of TiO2 is possible.

Bullard, D.↗
NASA NTRS1990

Space Station fluid resupply

Viewgraphs on space station fluid resupply are presented. Space Station Freedom is resupplied with supercritical O2 and N2 for the ECLSS and USL on a 180 day resupply cycle. Resupply fluids are stored in the subcarriers on station between resupply cycles and transferred to the users as required. ECLSS contingency fluids (O2 and N2) are supplied and stored on station in a gaseous state. Efficiency and flexibility are major design considerations. Subcarrier approach allows multiple manifest combinations. Growth is achieved by adding modular subcarriers.

Winters, AL↗
NASA NTRS1992

A wind tunnel application of large-field focusing schlieren

A large-field focusing schlieren apparatus was installed in the NASA Lewis Research Center 9 by 15 foot wind tunnel in an attempt to determine the density gradient flow field of a free jet issuing from a supersonic nozzle configuration. The nozzle exit geometry was designed to reduce acoustic emissions from the jet by enhancing plume mixing. Thus, the flow exhibited a complex three-dimensional structure which warranted utilizing the sharp focusing capability of this type of schlieren method. Design considerations concerning tunnel limitations, high-speed photography, and video tape recording are presented in the paper.

Ponton, Michael K.↗
NASA NTRS1992

The Ulysses solar X-ray/cosmic gamma-ray burst experiment

The Ulysses X-ray and gamma-ray instrument is described, and its scientific objectives are presented. Some aspects of the history of the Ulysses mission are explained, as well as of the design considerations for this experiment. As this mission will be the most distant one from earth ever to carry a burst detector, the primary cosmic objective will be to localize gamma-burst sources by triangulation.

Hurley, Kevin↗
NASA NTRS1992

Design and test hardware for a solar array switching unit

This paper describes the control of a pulse width modulated (PWM) type sequential shunt switching unit (SSU) for spacecraft applications. It is found that the solar cell output capacitance has a significant impact on SSU design. Shorting of this cell capacitance by the PWM switch causes input current surges. These surges are minimized by the use of a series filter inductor. The system with a filter is analyzed for ripple and the control to output-voltage transfer function. Stable closed loop design considerations are discussed. The results are supported by modeling and measurements of loop gain and of closed-loop bus impedance on test hardware for NASA's 120 V Earth Observation System (EOS). The analysis and modeling are also applicable to NASA's 160 V Space Station power system.

Patil, A. R.↗
NASA NTRS1993

Earth Observing System (EOS) real-time onboard orbit determination

The paper describes the TDRSS Onboard Navigation System (TONS) selected by NASA/GSFC for the EOS-AM1 spacecraft as the baseline navigation system for real-time onboard orbit determination. Particular attention is given to the TONS algorithms and environmental models, the general design considerations, the algorithm implementation, and the required hardware. Results are presented of the covariance analysis for the nominal onboard and instrument requirements.

Folta, David C.↗
NASA NTRS1993

GaAs optoelectronic neuron arrays

A simple optoelectronic circuit integrated monolithically in GaAs to implement sigmoidal neuron responses is presented. The circuit integrates a light-emitting diode with one or two transistors and one or two photodetectors. The design considerations for building arrays with densities of up to 10,000/sq cm are discussed.

Lin, Steven↗
NASA NTRS1992

The detrimental effect of friction on space microgravity robotics

The authors present an analysis of why control systems are ineffective in compensating for acceleration disturbances due to Coulomb friction. Linear arguments indicate that the effects of Coulomb friction on a body are most difficult to reject when the control actuator is separated from the body of compliance. The linear arguments were illustrated in a nonlinear simulation of optimal linear tracking control in the presence of nonlinear friction. The results of endpoint acceleration measurements for four robot designs are presented and are compared with simulation and to equivalent measurements on a human. It is concluded that Coulomb friction in common bearings and transmission induces unacceptable levels of endpoint acceleration, that these accelerations cannot be adequately attenuated by control, and that robots for microgravity work will require special design considerations for inherently low friction.

Newman, Wyatt S.↗
NASA NTRS1992

Concept for a lunar array for very low frequency radio astronomy

We discuss the design considerations relevant to a very low frequency array, to be deployed on the lunar near side during an early expedition. Such an array would operate in the frequency range 1-10 MHz, and would consist nominally of 20 antennas distributed over a region approximately 40 km in extent. Each antenna station would consist of a crossed-dipole antenna, together with a receiver, digitizer, solar cells, and batteries. In addition, the station will contain a UHF transmitter for relaying the digitized signal to a central station where it will be transmitted to Earth for subsequent processing, including cross-correlation with signals from other antennas. Each antenna station (including the central station) would be deployed as a self-contained unit, mounted on a miniature robotic vehicle. No fixed structures are required for the array.

Marsh, Kenneth A.↗
NASA NTRS1990

The 'problem' with automation - Inappropriate feedback and interaction, not 'over-automation'

Automation in high-risk industry is often blamed for causing harm and increasing the chance of human error when failures occur. It is proposed that the problem is not the presence of automation, but rather its inappropriate design. The problem is that the operations are performed appropriately under normal conditions, but there is inadequate feedback and interaction with the humans who must control the overall conduct of the task. The problem is that the automation is at an intermediate level of intelligence, powerful enough to take over control which used to be done by people, but not powerful enough to handle all abnormalities. Moreover, its level of intelligence is insufficient to provide the continual, appropriate feedback that occurs naturally among human operators. To solve this problem, the automation should either be made less intelligent or more so, but the current level is quite inappropriate. The overall message is that it is possible to reduce error through appropriate design considerations.

Norman, D. A.↗
NASA NTRS1992

Design of a monopulse SAR system to determine elevation angles

Terrain height variations in mountainous areas cause problems in radiometric corrections of synthetic aperture radar (SAR) images. To determine the elevation angle and the height at the different parts of an image, an application of the monopulse principle is proposed. From the ratios of images radiometrically modulated by the difference and sum antenna pattern in range it is possible to calculate the appropriate elevation angle at any point in the image. Design considerations for a corresponding airborne SAR-system are presented, and some estimates of error influences (e.g., ambiguities), expected performance and precision in topographic mapping are given.

Oettl, H.↗
NASA NTRS1955

Effect of high rotor pressure-surface diffusion on performance of a transonic turbine

The subject turbine was investigated to determine the effect of high rotor pressure-surface diffusion on turbine performance. A comparison of the subject turbine with the most efficient transonic turbine in the present series of investigations showed that the efficiency of the subject turbine was almost as high, the suction-surface diffusion parameter was about the same, and the solidity was reduced by 36 percent. Because the loss per blade increased greatly with an increase in pressure-surface diffusion, the latter is also considered to be an important design consideration.

Miser, James W↗
NASA NTRS1953

Charts and approximate formulas for the estimation of aeroelastic effects of the lateral control of swept and unswept wings

Charts and approximate formulas are presented for the estimation of static aeroelastic effects on the spanwise lift distribution, rolling-moment coefficient, and rate of roll due to the deflection of ailerons on swept and unswept wings at subsonic and supersonic speeds. Some design considerations brought out by the results of this report are discussed. This report treats the lateral-control case in a manner similar to that employed in NACA Report 1140 for the symmetric-flight case, and is intended to be used in conjunction with NACA Report 1140 and the charts and formulas presented therein.

Foss, Kenneth A↗
NASA NTRS1972

Laboratory and Industrial Ventilation

This handbook supplements the Facilities Engineering Handbook (NHB 7320.1) and provides additional policies and criteria for uniform application to ventilation systems. It expands basic requirements, provides additional design and construction guidance, and places emphasis on those design considerations which will provide for greater effectiveness in the use of these systems. The provisions of this handbook are applicable to all NASA field installations and the Jet Propulsion Laboratory. Since supply of this handbook is limited, abstracts of the portion or portions applicable to a given requirement will be made for the individual specific needs encountered rather than supplying copies of the handbook as has been past practice.

Source record↗
NASA NTRS1989

Design of a Solar Sail Mission to Mars

A new area of interest in space vehicles is the solar sail. Various applications for which it has been considered are attitude control of satellites, focusing light on the jungles of Vietnam, and a Halley's comet rendezvous. Although for various reasons these projects were never completed, new interest in solar sails has arisen. The solar sail is an alternative to the rocket-propelled space vehicle as an interplanetary cargo vehicle, and manufacture of solar sails on the space station is a possibility. Solar sails have several advantages over rockets, including an unlimited power supply and low maintenance. The purpose of this project is to design a solar sail mission to Mars. The spacecraft will efficiently journey to Mars powered only by a solar sail. The vehicle weighs 487.16 kg and will be launchable on an expendable launch vehicle. The project includes an investigation of options to minimize cost, weight, and flight duration. The design of the sail and its deployment system are a major part of the project, as is the actual mission planning. Various topics researched include solar power, material, space environment, thermal control, trajectories, and orbit transfer. Various configurations are considered in order to determine the optimal structure. Another design consideration is the control system of the vehicle. This system includes the attitude control and the communication system of the sail. This project will aid in determining the feasibility of a solar sail and will raise public interest in space research.

Feaux, K.↗
NASA NTRS1993

More sense for less cents: Cost effective servicing of remote sensing satellites

This paper addresses the design considerations for Earth observation spacecraft bus and payload subsystems such that cost-effective spacecraft maintainability is enhanced through optimized reliability and the application of robotic on-orbit support. In the past, for most satellites, maintainability has been associated with the clever application of telemetry reconfiguration and the use of redundant systems as necessary over the life cycle of the spacecraft. This presentation addresses the opportunities and challenges of leveraging the extensive work already accomplished in the development of on-orbit servicing technologies.

Lee, Jeannie↗