Search NASA⌕ Search

SEARCH · Search NASA

Results for “extended”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Extended Active Disturbance Rejection Controller

Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

Gao, Zhiqiang↗
NASA NTRS2016

Elaborated Odor Test for Extended Exposure

Concerns were raised when incidental exposure to a proprietary bonding material revealed the material had an irritating odor. The NASA-STD-6001B document describes a supplemental test method option for programs to evaluate materials with odor concerns (Test 6, Odor Assessment). In addition to the supplemental standard odor assessment with less than 10 seconds of exposure, the NASA White Sands Test Facility (WSTF) Materials Flight Acceptance Testing section was requested to perform an odor test with an extended duration to evaluate effects of an extended exposure and to more closely simulate realistic exposure scenarios. With approval from the NASA Johnson Space Center Industrial Hygienist, WSTF developed a 15-minute odor test method. WSTF performed this extended-duration odor test to evaluate the odor and physical effects of the bonding material configured between two aluminum plates, after the safety of the gas was verified via toxicity analysis per NASA-STD-6001B Test 7, Determination of Offgassed Products. During extended-duration testing, odor panel members were arranged near the test material in a small room with the air handlers and doors closed to minimize dilution. The odor panel members wafted gas toward themselves and recorded their individual assessments of odor and physical effects at various intervals during the 15-minute exposure and posttest. A posttest interview was conducted to obtain further information. Testing was effective in providing data for comparison and selection of an optimal offgassing and odor containment configuration. The developed test method for extended exposure is proposed as a useful tool for further evaluating materials with identified odors of concern if continued use of the material is anticipated.

Buchanan, Vanessa D.↗
NASA NTRS2023

Extended Kalman Filter Performance on the Artemis-1 Mission

The Artemis Program is NASA’s campaign to explore the Moon and beyond. Artemis-1, the uncrewed exoLEO test flight of the Orion spacecraft, was completed in 2022. There were four navigation Extended Kalman Filters (EKFs) that are part of the Orion navigation system. The Atmospheric Extended Kalman Filter (ATMEKF) estimates the vehicle position, velocity, and attitude (referred to as the vehicle state) during the ascent and entry phases of flight. Once Orion is outside of Earths atmosphere, the Earth Orbit Extended Kalman Filter (EOEKF) and CisLunar Extended Kalman Filter (CLEKF) estimate the translational states, depending on the phase of flight, while the Attitude Extended Kalman Filter (ATTEKF) estimates the rotational state of the vehicle. The Kalman filters propagate the vehicle state forward in time using a combination of dynamics models and the output data from the Inertial Measurement Unit (IMU). The filters update the vehicle states and associated uncertainties, in the form of the covariance matrix, using pseudorange measurements from GPS (in ATMEKF/EOEKF), optical navigation measurements of the Earth or Moon (in CLEKF), and star tracker measurements (in ATTEKF). Simultaneously, the Kalman filters estimate error sources in the sensors, which are included in the state vectors as Exponentially Correlated Random Variables (ECRVs). This paper will summarize the performance of these filters during the Artemis-1 mission.

Artemis-1↗
NASA NTRSDate not supplied

Extending the Duration of Crewed Stays on the Lunar Surface

NASA’s Artemis missions aim to return humans to the Moon for the first time since the Apollo Program. Unlike the Apollo missions, Artemis missions will take advantage of pre-emplaced assets on the lunar surface to support crewed exploration, science, and utilization. Although the initial Artemis surface missions are intended to keep crew on the lunar surface for durations ranging from several days to several weeks, crewed stays of longer periods may provide additional support toward NASA’s Moon to Mars Objectives, including long-term exploration and continuous human lunar presence. If mission durations are extended beyond the expected few weeks, the elements and concepts of operation for the lunar architecture will need to be capable of supporting that extension. This paper uses an integrated systems analysis perspective to examine the architectural considerations of extending the duration of human missions on the lunar surface. By identifying these key architectural considerations, this paper offers insight into how elements and operations might meet the demands of potential future mission concepts. This paper does not recommend changes to NASA’s lunar architecture, and it does not evaluate whether any mission concepts affect the relative satisfaction of the Moon to Mars Objectives. However, if crew do remain on the surface for progressively longer periods of time, the functions and capabilities provided by the assets supporting the crew may need to adjust to support the needs of those missions. The functions and capabilities identified as key to enable such extended duration missions include power generation and storage, logistics delivery, radiation mitigation, provision of medical and exercise capability, abort from the lunar surface, maintenance, and the provision of pressurized volume. For example, the medical capabilities available to the crew may become more extensive, and habitable elements may need to change to support longer crewed periods (and shorter quiescent periods). In some cases, these changes may be accomplished through alterations to use cases, operational changes, or the evolution of lunar surface elements, but in other cases, new elements may be preferable. By identifying key considerations for the functions and capabilities of notional lunar surface elements as the length of each crewed mission is extended from several days to continuous human presence on the Moon, this paper assesses how the elements of NASA’s lunar architecture might support the extension of mission durations. In addition, this analysis can help inform future evaluation of whether such extended duration missions improve NASA’s ability to address its Moon to Mars Objectives.

Garrett M. Carman↗
NASA NTRS2007

Adaptive Cross-correlation Algorithm and Experiment of Extended Scene Shack-Hartmann Wavefront Sensing

We have developed a new, adaptive cross-correlation (ACC) algorithm to estimate with high accuracy the shift as large as several pixels in two extended-scene images captured by a Shack-Hartmann wavefront sensor (SH-WFS). It determines the positions of all of the extended-scene image cells relative to a reference cell using an FFT-based iterative image shifting algorithm. It works with both point-source spot images as well as extended scene images. We have also set up a testbed for extended0scene SH-WFS, and tested the ACC algorithm with the measured data of both point-source and extended-scene images. In this paper we describe our algorithm and present out experimental results.

Shack - Hartmann sensor↗
NASA NTRS1972

Extended precision software packages

A description of three extended precision packages is presented along with three small conversion subroutines which can be used in conjunction with the extended precision packages. These extended packages represent software packages written in FORTRAN 4. They contain normalized or unnormalized floating point arithmetic with symmetric rounding and arbitrary mantissa lengths, and normalized floating point interval arithmetic with appropriate rounding. The purpose of an extended precision package is to enable the user to use and manipulate numbers with large decimal places as well as those with small decimal places where precision beyond double precision is required.

Phillips, E. J.↗
NASA NTRS1982

Extended-performance 8-cm ion thruster operation

The performance of an 8-cm ion thruster has been extended to 32-mN thrust, 4062-s specific impulse, and 0.033-mN/W thrust-to-power ratio. The design of this thruster is similar to the IAPS (Ion Auxiliary Propulsion System), which has a performance of 5-mN thrust, 3500-s specific impulse, and 0.036-mN/W thrust-to-power ratio. The above level of extended performance has been achieved by increasing the discharge power, ion-beam accelerating voltage, and propellant flowrate, and by modifying the propellant-vapor injection, discharge-chamber magnetic-field strength, high-voltage insulators, and electron baffle. This paper describes results obtained in characterizing the extended-performance operation of both the unmodified thruster (i.e., in an IAPS-like configuration) and the modified thruster. Lifetime-estimating measurements for the modified thruster at extended-performance conditions are also presented.

Wessel, F. J.↗
NASA NTRS1987

Signature-extendable technology - Global space-based crop recognition

The use of signature-extendable technology to improve the efficiency of machine processing of remotely sensed data is examined. Temporal profile technology is employed to automatically recognize crops; the technique uses the Kauth and Thomas (1976) transform of Landsat, multidata, and parameters derived from a model of each crop's greenness-time trajectory. The basic characteristics of temporal profile technology and the U.S. based labeling algorithm are described. Consideration is given to signature extension, signature-extendable spaces, and signature-extendable features. The greenness and brightness parameters used in temporal profile technology are derived. The signature extendability of the parameters is evaluated by applying them to the analysis of corn and soybean crops in the U.S. and Argentina. It is noted that the technique is an affordable and efficient method for deriving data on crops on a global basis.

Hall, Forrest G.↗
NASA NTRS1987

Far-infrared continuum emission from the nucleus, starburst, and extended spiral arms of NGC 1068

Far-infrared slit scans across NGC 1068 are used to better define the contribution of the active nucleus, starburst disk, and extended spiral arms in the luminous output of this bright Seyfert 2 galaxy. The decomposition of the emission from the bright, inner 3 kpc of this galaxy suggests that at 50 microns, about half the emission is from star formation in a starburst disk and half from the compact, centrally heated circumnuclear cloud. The 100-micron profile of the starburst disk is asymmetric with respect to the nucleus. This appears to be the result of an extraordinary star-forming complex about a kiloparsec away from the center. With the application of maximum entropy deconvolution to the scans, evidence is found for 100-micron emission from the extended spiral arms of the galaxy. The far-infrared emission from the starburst region is distinguished from that of the extended spiral arms. In terms of both total luminosity and surface brightness, the extended spiral arms of NGC 1068 are at the bright end of the range of far-infrared emission from quiescent, noninteracting spirals.

Lester, D. F.↗
NASA NTRS1990

The extended tracking network and indications of baseline precision and accuracy in the North Andes

The CASA Uno Global Positioning System (GPS) experiment (January-February 1988) included an extended tracking network which covered three continents in addition to the network of scientific interest in Central and South America. The repeatability of long baselines (400-1000 km) in South America is improved by up to a factor of two in the horizontal vector baseline components by using tracking stations in the Pacific and Europe to supplement stations in North America. In every case but one, the differences between the mean solutions obtained using different tracking networks was equal to or smaller than day-to-day rms repeatabilities for the same baselines. The mean solutions obtained by using tracking stations in North America and the Pacific agreed at the 2-3 millimeter level with those using tracking stations in North America and Europe. The agreement of the extended tracking network solutions suggests that a broad distribution of tracking stations provides better geometric constraints on the satellite orbits and that solutions are not sensitive to changes in tracking network configuration when an extended network is use. A comparison of the results from the North Andes and a baseline in North America suggests that the use of a geometrically strong extended tracking network is most important when the network of interest is far from North America.

Freymueller, Jeffrey T.↗
NASA NTRS1990

Extended Duration Orbiter Medical Project

The Extended Duration Orbiter (EDO) program addresses a need for more time to perform experiments and other tasks during Space Shuttle missions. As a part of this program, the Extended Duration Orbiter Medical Project (EDOMP) has been instituted to obtain information about physiologic effects of extending mission duration and the effectiveness of countermeasures against factors that might compromise crew health, safety, or performance on extended-duration missions. Only those investigations that address and characterize operational problems, develop countermeasures, or evaluate the effectiveness of countermeasures will be pursued. The EDOMP investigations will include flight-associated Detailed Supplementary Objectives as well as ground-based studies simulating the influence of microgravity. Investigator teams have been formed in the following areas: biomedical physiology, cardiovascular and fluid/electrolyte physiology, environmental health, muscle and exercise physiology, and neurophysiology. Major operational questions must be answered in each of these areas, and investigations have been designed to answer them. The EDO program will proceed only after countermeasures have been shown to be effective in preventing or mitigating the adverse changes they have been designed to attenuate. The program is underway and will continue on each Shuttle flight as the manifest builds toward a 16-day orbital flight.

Leach, C. S.↗
NASA NTRS1991

Imaging observations of the extended sodium atmosphere of the moon

Pilot ground-based optical imaging observations of the extended lunar environment were conducted at McDonald Observatory in February 1991. One set of images taken on February 20 revealed emission at the combined D1 (5896 A) and D2 (5890 A) lines of neutral sodium extending out to about 5 lunar radii from the center of the moon on the sunward side and much fainter emission extending out to about 15-20 lunar radii on the antisunward side. Peak emission (D1 + D2) above the moon's limb at a distance of 1.8 lunar radii along the lunisolar axis was measured to be 900 Rayleighs, decreasing with distance as r exp -4. The morphology of the emitting region is qualitatively that of a comet, i.e., a bright coma centered on the moon and an extended tail trailing away in the antisunward direction.

Mendillo, Michael↗
NASA NTRS1992

Aperture codes for sensors viewing extended objects from space

The paper describes aperture codes viewing extended objects form space which find application in imaging an extended object which may have relatively low contrast, and whose lateral limits extend beyond the FOV of the sensor. Those elements of an extended object lying near the FOV limits are only partially coded, i.e., flux from those elements cannot cast a shadow of the entire aperture code onto the detector, as can elements near the center of the FOV. This has consequences for the algorithms used to reconstruct the image. The object field is divided into a number of elements which is smaller than the number of detector pixels, and a least squares fit to the data is performed. The methods used for choosing the matrices representing the aperture codes are discussed, and computer simulations of the effects of noise are described.

Curtis, C. C.↗
NASA NTRS1954

Preliminary Investigation of Performance of Variable-throat Extended-plug-type Nozzles over Wide Range of Nozzle Pressure Ratios

As part of an overall program for the experimental investigation of large-scale jet nozzles, a preliminary evaluation of the internal performance characteristics of several variable-throat extended-plug-type nozzles was obtained over a range of nozzle pressure rations from 2 to 15 with nozzle throat variations as great as 2:1. The extended-plug nozzle attained peak thrust coefficients as high as those which have been attained with fixed-geometry convergent-divergent nozzles. The thrust coefficients of the extended-plug nozzles were relatively insensitive to both nozzle pressure ratio and throat area over the range investigated. The lack of sensitivity of thrust coefficient to nozzle pressure ratio and throat area was due primarily to the absence of severe decreases in thrust coefficient, which are normally observed at low nozzle pressure ratios for convergent-divergent nozzles because of overexpansion. For choked flow, the flow coefficients of the extended-plug nozzles varied from 0.95 to 0.997. A ratio of the outer-shell exit area to nozzle throat area was found to be an important variable affecting nozzle performance. Most of the configurations reported herein showed a small decrease in thrust coefficient at low nozzle pressure ratios; however, it is believed that this characteristic can nearly be eliminated by proper nozzle design.

NOZZLES↗
NASA NTRS1994

The origin of extended interstellar shells around Wolf-Rayet stars having bright optical ring nebulae

Investigations of the interstellar environment around Wolf-Rayet (WR) stars have lead to the discovery of extended shells of gas and dust 50-100 pc in diameter in the lines of sight toward three WR stars. In this paper, several origins for these extended shells are discussed. While positional coincidences cannot be excluded, the locations of the WR stars near the projected centers of the shells, the detection of only shortward-shifted, high-velocity UV absorption line components in their IUE spectra, plus commonality of some WR star properties which are rare in the general WR star population suggest some casual connections between the WR stars and formation of interstellar shells. To access whether the high-velocity UV interstellar absorption lines are a frequent phenomenon related to WR stellar winds, we present a survey of such features in all WR stars observed with IUE through 1991. Of 35 stars studied, only four are found to have components with velocity displacements greater than 45 km/s which are not attributable to previously identified OB association superbubbles. The means a surprising 82% of non-OB association WR stars show no evidence of high-velocity gas in their lines of sight at IUE's spectral resolution, suggesting that high-velocity interstellar absorption lines are not a common consequence of Wolf-Rayet star stellar winds alone. We review the properties of three WR stars (HD 50896, HD 96548, and HD 192163) which may reside inside extended interstellar shells and find that they are similar in terms of spectral class (WN5-8), presence of an optical ring nebula, and reported photometric variability. Evaluation of possible origins of the extended shells suggests these three stars are in a post X-ray binary stage of high-mass binary star evolution. If this is correct, then the large interstellar shells detected might be evidence of either supernova remnant shells generated by the explosion of the binary's primary star, or non-conservative mass transfer during a Roche Lobe overflow stage of the binary after the supernova explosion. In either of these cases the bright optical ring nebulae associated with these three WR stars may signify recent Roche Lobe overflows consistent with spectroscopic abundance analysis.

Nichols, J. S.↗
NASA NTRS1990

Integrating Commercial Off-The-Shelf (COTS) graphics and extended memory packages with CLIPS

This paper addresses the question of how to mix CLIPS with graphics and how to overcome PC's memory limitations by using the extended memory available in the computer. By adding graphics and extended memory capabilities, CLIPS can be converted into a complete and powerful system development tool, on the other most economical and popular computer platform. New models of PCs have amazing processing capabilities and graphic resolutions that cannot be ignored and should be used to the fullest of their resources. CLIPS is a powerful expert system development tool, but it cannot be complete without the support of a graphics package needed to create user interfaces and general purpose graphics, or without enough memory to handle large knowledge bases. Now, a well known limitation on the PC's is the usage of real memory which limits CLIPS to use only 640 Kb of real memory, but now that problem can be solved by developing a version of CLIPS that uses extended memory. The user has access of up to 16 MB of memory on 80286 based computers and, practically, all the available memory (4 GB) on computers that use the 80386 processor. So if we give CLIPS a self-configuring graphics package that will automatically detect the graphics hardware and pointing device present in the computer, and we add the availability of the extended memory that exists in the computer (with no special hardware needed), the user will be able to create more powerful systems at a fraction of the cost and on the most popular, portable, and economic platform available such as the PC platform.

Callegari, Andres C.↗
NASA NTRS1998

The X-33 Extended Flight Test Range

Development of an extended test range, with range instrumentation providing continuous vehicle communications, is required to flight-test the X-33, a scaled version of a reusable launch vehicle. The extended test range provides vehicle communications coverage from California to landing at Montana or Utah. This paper provides an overview of the approaches used to meet X-33 program requirements, including using multiple ground stations, and methods to reduce problems caused by reentry plasma radio frequency blackout. The advances used to develop the extended test range show other hypersonic and access-to-space programs can benefit from the development of the extended test range.

Dale A Mackall↗
NASA NTRS1999

Microflaring in Low-Lying Core Fields and Extended Coronal Heating in the Quiet Sun

We have previously reported analyses of Yohkoh SXT data examining the relationship between the heating of extended coronal loops (both within and stemming from active regions) and microflaring in core fields lying along neutral lines near their footpoints (J. G. Porter, D. A. Falconer, and R. L. Moore 1998, in Solar Jets and Coronal Plumes, ed. T. Guyenne, ESA SP-421, and references therein). We found a surprisingly poor correlation of intensity variations in the extended loops with individual microflares in the compact heated areas at their feet, despite considerable circumstancial evidence linking the heating processes in these regions. Now, a study of Fe XII image sequences from SOHO EIT show that similar associations of core field structures with the footpoints of very extended coronal features can be found in the quiet Sun. The morphology is consistent with the finding of Wang et al. (1997, ApJ 484, L75) that polar plumes are rooted at sites of mixed polarity in the magnetic network. We find that the upstairs/downstairs intensity variations often follow the trend, identified in the active region observations, of a weak correspondence. Apparently much of the coronal heating in the extended loops is driven by a type of core field magnetic activity that is "cooler" than the events having the coronal signature of microflares, i.e., activity that results in little heating within the core fields themselves. This work was funded by the Solar Physics Branch of NASA's Office of Space Science through the SR&T Program and the SEC Guest Investigator Program.

Porter, Jason G.↗