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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.

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At least 811 records · Page 45

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NASA NTRS1990

New correction procedures for the fast field program which extend its range

A fast field program (FFP) algorithm was developed based on the method of Lee et al., for the prediction of sound pressure level from low frequency, high intensity sources. In order to permit accurate predictions at distances greater than 2 km, new correction procedures have had to be included in the algorithm. Certain functions, whose Hankel transforms can be determined analytically, are subtracted from the depth dependent Green's function. The distance response is then obtained as the sum of these transforms and the Fast Fourier Transformation (FFT) of the residual k dependent function. One procedure, which permits the elimination of most complex exponentials, has allowed significant changes in the structure of the FFP algorithm, which has resulted in a substantial reduction in computation time.

West, M.↗

NASA NTRS1990

National launch strategy vehicle data management system

The national launch strategy vehicle data management system (NLS/VDMS) was developed as part of the 1990 NASA Summer Faculty Fellowship Program. The system was developed under the guidance of the Engineering Systems Branch of the Information Systems Office, and is intended for use within the Program Development Branch PD34. The NLS/VDMS is an on-line database system that permits the tracking of various launch vehicle configurations within the program development office. The system is designed to permit the definition of new launch vehicles, as well as the ability to display and edit existing launch vehicles. Vehicles can be grouped in logical architectures within the system. Reports generated from this package include vehicle data sheets, architecture data sheets, and vehicle flight rate reports. The topics covered include: (1) system overview; (2) initial system development; (3) supercard hypermedia authoring system; (4) the ORACLE database; and (5) system evaluation.

Cordes, David↗

NASA NTRS1991

Dual-purpose self-deliverable lunar surface PV electrical power system

A safe haven and work supported PV power systems on the lunar surface will likely be required by NASA in support of the manned outpost scheduled for the post-2000 lunar/Mars exploration and colonization initiative. Initial system modeling and computer analysis shows that the concept is workable and contains no major high risk technology issues which cannot be resolved in the circa 2000 to 2025 timeframe. A specific selection of the best suited type of electric thruster has not been done; the initial modeling was done using an ion thruster, but Rocketdyne must also evaluate arc and resisto-jets before a final design can be formulated. As a general observation, it appears that such a system can deliver itself to the Moon using many system elements that must be transported as dead payload mass in more conventional delivery modes. It further appears that a larger power system providing a much higher safe haven power level is feasible if this delivery system is implemented, perhaps even sufficient to permit resource prospecting and/or lab experimentation. The concept permits growth and can be expanded to include cargo transport such as habitat and working modules. In short, the combined payload could be manned soon after landing and checkout. NASA has expended substantial resources in the development of electric propulsion concepts and hardware that can be applied to a lunar transport system such as described herein. In short, the paper may represent a viable mission on which previous investments play an invaluable role. A more comprehensive technical paper which embodies second generation analysis and system size will be prepared for near-term presentation.

Arnold, Jack H.↗

NASA NTRS1990

AEOSS runtime manual for system analysis on Advanced Earth-Orbital Spacecraft Systems

Advanced earth orbital spacecraft system (AEOSS) enables users to project the required power, weight, and cost for a generic earth-orbital spacecraft system. These variables are calculated on the component and subsystem levels, and then the system level. The included six subsystems are electric power, thermal control, structure, auxiliary propulsion, attitude control, and communication, command, and data handling. The costs are computed using statistically determined models that were derived from the flown spacecraft in the past and were categorized into classes according to their functions and structural complexity. Selected design and performance analyses for essential components and subsystems are also provided. AEOSS has the feature permitting a user to enter known values of these parameters, totally and partially, at all levels. All information is of vital importance to project managers of subsystems or a spacecraft system. AEOSS is a specially tailored software coded from the relational database program of the Acius' 4th Dimension with a Macintosh version. Because of the licensing agreements, two versions of the AEOSS documents were prepared. This version, AEOSS Runtime Manual, is permitted to be distributed with a finite number of the restrictive 4D Runtime version. It can perform all contained applications without any programming alterations.

Lee, Hwa-Ping↗

NASA NTRS1991

IDE spatio-temporal impact fluxes and high time-resolution studies of multi-impact events and long-lived debris clouds

During the first 12 months of the Long Duration Exposure Facility (LDEF) mission, the Interplanetary Dust Experiment (IDE) recorded over 15,000 total impacts on six orthogonal faces with a time resolution on the order of 15 to 20 seconds. When combined with the orbital data and the stabilized configuration of the spacecraft, this permits a detailed analysis of the micro-particulate environment. The functional status of each of the 459 detectors was monitored every 2.4 hours, and post-flight analyses of these data has now permitted an evaluation of the effective active detection area as a function of time, panel by panel and separately for the two sensitivity levels. Thus, total impacts were transformed into areal fluxes, and are presented here for the first time. Also discussed are possible effects of these fluxes on previously announced results: apparent debris events, meteor stream detections, and beta meteoroids in observationally significant numbers.

Mulholland, J. Derral↗

NASA NTRS1990

Compound estimation procedures in reliability

At NASA, components and subsystems of components in the Space Shuttle and Space Station generally go through a number of redesign stages. While data on failures for various design stages are sometimes available, the classical procedures for evaluating reliability only utilize the failure data on the present design stage of the component or subsystem. Often, few or no failures have been recorded on the present design stage. Previously, Bayesian estimators for the reliability of a single component, conditioned on the failure data for the present design, were developed. These new estimators permit NASA to evaluate the reliability, even when few or no failures have been recorded. Point estimates for the latter evaluation were not possible with the classical procedures. Since different design stages of a component (or subsystem) generally have a good deal in common, the development of new statistical procedures for evaluating the reliability, which consider the entire failure record for all design stages, has great intuitive appeal. A typical subsystem consists of a number of different components and each component has evolved through a number of redesign stages. The present investigations considered compound estimation procedures and related models. Such models permit the statistical consideration of all design stages of each component and thus incorporate all the available failure data to obtain estimates for the reliability of the present version of the component (or subsystem). A number of models were considered to estimate the reliability of a component conditioned on its total failure history from two design stages. It was determined that reliability estimators for the present design stage, conditioned on the complete failure history for two design stages have lower risk than the corresponding estimators conditioned only on the most recent design failure data. Several models were explored and preliminary models involving bivariate Poisson distribution and the Consael Process (a bivariate Poisson process) were developed. Possible short comings of the models are noted. An example is given to illustrate the procedures. These investigations are ongoing with the aim of developing estimators that extend to components (and subsystems) with three or more design stages.

Barnes, Ron↗

NASA NTRS1991

Selectable towline spin chute system

An emergency spin recovery parachute is presented that is housed within a centrally mounted housing on the aft end of an aircraft and connected to a ring fitting within the housing. Two selectively latching shackles connected to separate towlines are openly disposed adjacent the ring fitting. The towlines extend in opposite directions from the housing along the aircraft wing to attachment points adjacent the wing-tips where the other end of each towline is secured. Upon pilot command, one of the open shackles latches to the ring fitting to attach the towline connected thereto, and a second command signal deploys the parachute. Suitable break-away straps secure the towlines to the aircraft surface until the parachute is deployed and the resulting force on the towline attached to the parachute overcomes the straps and permits the towline to extend to the point of attachment to exert sufficient drag on the spinning aircraft to permit the pilot to regain control of the aircraft. To employ the parachute as a drag chute to reduce landing speeds, both shackles and their respective towlines are latched to the ring fitting.

Vairo, Daniel M.↗

NASA NTRS1991

Spur-gear optimization using SPUROPT computer program

A computer program developed for optimizing spur gear designs, SPUROPT, was updated by installing a new subroutine that uses AGMA 908-B89 standards to calculate the J-factor for determining tooth-bending stress. The updated SPUROPT program was then used to optimize a spur gear set for maximum fatigue life, minimum dynamic load, or minimum weight. All calculations were made with constraints on as many as 13 parameters by using three design variables: the number of teeth, diametral pitch, and tooth-face width. Results depended largely on constraints values. When the limiting bending stress was set at a high value, the optimal solution was the highest allowable number of teeth. When the allowable bending stress was lowered, the optimal solution moved toward the fewest number of teeth permitted. Final results were also affected by the amount of transmission error. A lower error permitted a higher number of teeth.

Coe, Harold H.↗

NASA NTRS1991

An advanced hypervelocity aerophysics facility - A ground-based flight-test range

The paper discusses a concept for a ground-based flight-test facility, a large aeroballistic range capable of launching models large enough to permit the installation of significant amounts of onboard instrumentation. The large model size would also provide thick shock/boundary layers, thus providing the opportunity to measure flow-field properties via advanced offboard diagnostics. Current fabrication technology should permit the construction of a two-stage light-gas gun capable of accelerating 20 to 25 cm diameter models to velocities on the order of 6 km/sec. An electromagnetic launcher or a ram accelerator is considered as a potential means for achieving larger model sizes and/or greater launch velocities. Possible methods for obtaining and recording data are discussed as are the test chamber and model deceleration section requirements.

Witcofski, R. D.↗

NASA NTRS1991

Anomalous gain in an isotopically mixed CO2 laser and application to absolute wavelength calibration

Measurements are reported on a grating-tuned CO2 laser, containing an isotropic mixture of O-16C-12O-16, O-16C-12O-18, and O-18C-12O-18. The P6 and R14 lines of O-16C-12O-16 were found to have anomalously high intensities. These anomalies are produced by the near coincidence of the transition frequencies in two distinct isotopes, permitting them to act as a single indistinguishable population. These two lines can be used to identify the rotational quantum numbers in the P and R branch spectra, thereby permitting absolute wavelength calibration to be achieved.

Hewagama, Tilak↗

NASA NTRS1990

Multistep fluorescence gated proportional counters

A proportional counter is introduced in which the levels of energy and spatial resolutions and background rejection permit the application of the device to X-ray astronomy. A multistep approach is employed in which photons cause a signal that triggers the system and measures the energy of the incident photon. The multistep approach permits good energy resolution from parallel geometry and from the imaging stage due to coupling of the imaging and amplification stages. The design also employs fluorescence gating to reduce background, a method that is compatible with the multistep technique. Use of the proportional counter is reported for NASA's supernova campaign, and the pair background is below 0.0001 counts/sq cm sec keV at the xenon k-edge. Potential improvements and applications are listed including the CASES, POF, and EXOSS mission programs.

Ramsey, Brian D.↗

NASA NTRS1990

Infrared fiber coupled acousto-optic tunable filter spectrometer

A spectrometer design is introduced which combines an acoustooptic tunable filter (AOTF) and IR-transmitting flouride-glass fibers. The AOTF crystal is fabricated from TeO2 and permits random access to any wavelength in less than 50 microseconds, and the resulting spectrometer is tested for the remote analysis of gases and hydrocarbons. The AOTF spectrometer, when operated with a high-speed frequency synthesizer and optimized algorithms, permits accurate high-speed spectroscopy in the mid-IR spectral region.

Levin, K. H.↗

NASA NTRS1992

High-Dynamic-Range Fiber-Optic Link For Microwave Signals

Ultrastable fiber-optic communications system transmits microwave signals between antenna sites of Deep Space Network (DSN) and central processing station several kilometers away. Permits relocation of critical components from front-end areas of DSN antennas to central location, permitting radio-frequency (RF) antenna arraying, improving DSN flexibility, maintainability, and system performance. Also useful in commercial analog and digital communications.

Logan, Ronald T., Jr.↗

NASA NTRS1991

Advanced infrared astronomy

This task supports the application of infrared heterodyne spectroscopy and other high resolution techniques, as well as infrared arrays to ultra-high resolution studies of molecular constituents of planetary atmospheres. High spectral and spatial resolution measurement and analysis of individual spectral lines permits the retrieval of distributions of atmospheric molecular abundances and temperatures and thus, information on local photochemical processes. Determination of absolute line positions to better than 10(exp -8) permits direct measurement of gas velocities to a few m/sec and thus, the study of dynamics. Observations are made from ground based observatories.

Kostiuk, Theodor↗

NASA NTRS1991

Investigation of air transportation technology at Ohio University, 1990-1991

The status of the Joint University Program is given. Brief synopsis of some areas of research follow. The study of spectrum efficient methods for transmitting weather information to aircraft has resulted in definition of an improved amplitude and phase modulation process which permits reutilization of voice channels for both voice and data. The system is being implemented for testing. Multisensor navigation systems introduce increased flexibility and performance for aviation, at the expense of increased complexity. Insuring a high level of system reliability and integrity requires that faults not only be detected, but also isolated to specific elements, so that the remaining capabilities of the system may be used with confidence. An algorithm was developed. The JUP has served as a vehicle for reporting work accomplished in evoked potential vision tracking experiments to determine the engineering parameters of this input and control method. Application of GPS in an interferometric mode permits accurate measurement of differential motion; aircraft attitude may be determined using GPS only, with multiple antennas.

Lilley, Robert W.↗

NASA NTRS1991

The Jade File System

File systems have long been the most important and most widely used form of shared permanent storage. File systems in traditional time-sharing systems, such as Unix, support a coherent sharing model for multiple users. Distributed file systems implement this sharing model in local area networks. However, most distributed file systems fail to scale from local area networks to an internet. Four characteristics of scalability were recognized: size, wide area, autonomy, and heterogeneity. Owing to size and wide area, techniques such as broadcasting, central control, and central resources, which are widely adopted by local area network file systems, are not adequate for an internet file system. An internet file system must also support the notion of autonomy because an internet is made up by a collection of independent organizations. Finally, heterogeneity is the nature of an internet file system, not only because of its size, but also because of the autonomy of the organizations in an internet. The Jade File System, which provides a uniform way to name and access files in the internet environment, is presented. Jade is a logical system that integrates a heterogeneous collection of existing file systems, where heterogeneous means that the underlying file systems support different file access protocols. Because of autonomy, Jade is designed under the restriction that the underlying file systems may not be modified. In order to avoid the complexity of maintaining an internet-wide, global name space, Jade permits each user to define a private name space. In Jade's design, we pay careful attention to avoiding unnecessary network messages between clients and file servers in order to achieve acceptable performance. Jade's name space supports two novel features: (1) it allows multiple file systems to be mounted under one direction; and (2) it permits one logical name space to mount other logical name spaces. A prototype of Jade was implemented to examine and validate its design. The prototype consists of interfaces to the Unix File System, the Sun Network File System, and the File Transfer Protocol.

Rao, Herman Chung-Hwa↗

NASA NTRS1992

Elliptic surface grid generation in three-dimensional space

A methodology for surface grid generation in three dimensional space is described. The method solves a Poisson equation for each coordinate on arbitrary surfaces using successive line over-relaxation. The complete surface curvature terms were discretized and retained within the nonhomogeneous term in order to preserve surface definition; there is no need for conventional surface splines. Control functions were formulated to permit control of grid orthogonality and spacing. A method for interpolation of control functions into the domain was devised which permits their specification not only at the surface boundaries but within the interior as well. An interactive surface generation code which makes use of this methodology is currently under development.

Kania, Lee↗

NASA NTRS1990

Optical depth measurements and atmospheric correction of remotely sensed data for FIFE

Data derived from an airborne tracking-sun photometer are used to provide quantitative corrections for atmospheric effects in remotely sensed data. The atmospheric correction involves the validation of radiometric and atmospheric measurements and the application of single scattering approximation which permits the separation of Rayleigh scattering from aerosol scattering. Sun-photometer data are used to generate plots of spectral optical depths, aerosol size distributions, aerosol phase functions, and aerosol single-scattering albedos. The atmospheric correction model and the atmospheric optical properties are incorporated into a program which is applied to two flightlines of data. Atmospheric corrections tested on remotely sensed data permitted the removal of limb brightening, although the results require verification by means of ground measurements.

Wrigley, R. C.↗