SEARCH · Engineering Papers

Results for “PmS”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2

All sources NASA NTRS DOE OSTI

NASA NTRS2011

NEXT Propellant Management System Integration With Multiple Ion Thrusters

As a critical part of the NEXT test validation process, a multiple-string integration test was performed on the NEXT propellant management system and ion thrusters. The objectives of this test were to verify that the PMS is capable of providing stable flow control to multiple thrusters operating over the NEXT system throttling range and to demonstrate to potential users that the NEXT PMS is ready for transition to flight. A test plan was developed for the sub-system integration test for verification of PMS and thruster system performance and functionality requirements. Propellant management system calibrations were checked during the single and multi-thruster testing. The low pressure assembly total flow rates to the thruster(s) were within 1.4 percent of the calibrated support equipment flow rates. The inlet pressures to the main, cathode, and neutralizer ports of Thruster PM1R were measured as the PMS operated in 1-thruster, 2-thruster, and 3-thruster configurations. It was found that the inlet pressures to Thruster PM1R for 2-thruster and 3-thruster operation as well as single thruster operation with the PMS compare very favorably indicating that flow rates to Thruster PM1R were similar in all cases. Characterizations of discharge losses, accelerator grid current, and neutralizer performance were performed as more operating thrusters were added to the PMS. There were no variations in these parameters as thrusters were throttled and single and multiple thruster operations were conducted. The propellant management system power consumption was at a fixed voltage to the DCIU and a fixed thermal throttle temperature of 75 C. The total power consumed by the PMS was 10.0, 17.9, and 25.2 W, respectively, for single, 2-thruster, and 3-thruster operation with the PMS. These sub-system integration tests of the PMS, the DCIU Simulator, and multiple thrusters addressed, in part, the NEXT PMS and propulsion system performance and functionality requirements.

Sovey, James S.↗

DOE OSTI2023

An Assessment of Additively Manufactured Bonded Permanent Magnets for a Distributed Wind Generator

In this paper, we examine and compare the performance of a generator design optimized using additively manufactured NdFeB-SmFeN in nylon-polymer-bonded permanent magnets (PMs) against a generator design with conventional NdFeB sintered PMs. To realize this, a commercially available 15-kW wind generator's rotor is re-optimized using both additively manufactured and sintered NdFeB magnets using simple geometric parameterization that allowed for two specific magnet shapes, namely, arc-shaped and crown-shaped designs. Results showed that for a similar generator performance, the designs with additively manufactured bonded PMs are more cost-competitive in terms of the estimated PM material cost and also have negligible eddy current magnet losses.

additive manufacturing↗

DOE OSTI2021

Measuring Young Stars in Space and Time. II. The Pre-main-sequence Stellar Content of N44

The Hubble Space Telescope survey Measuring Young Stars in Space and Time (MYSST) entails some of the deepest photometric observations of extragalactic star formation, capturing even the lowest-mass stars of the active star-forming complex N44 in the Large Magellanic Cloud. We employ the new MYSST stellar catalog to identify and characterize the content of young pre-main-sequence (PMS) stars across N44 and analyze the PMS clustering structure. To distinguish PMS stars from more evolved line of sight contaminants, a non-trivial task due to several effects that alter photometry, we utilize a machine-learning classification approach. This consists of training a support vector machine (SVM) and a random forest (RF) on a carefully selected subset of the MYSST data and categorize all observed stars as PMS or non-PMS. Combining SVM and RF predictions to retrieve the most robust set of PMS sources, we find ∼26,700 candidates with a PMS probability above 95% across N44. Employing a clustering approach based on a nearest neighbor surface density estimate, we identify 16 prominent PMS structures at 1σ significance above the mean density with sub-clusters persisting up to and beyond 3σ significance. The most active star-forming center, located at the western edge of N44's bubble, is a subcluster with an effective radius of ∼5.6 pc entailing more than 1100 PMS candidates. Furthermore, we confirm that almost all identified clusters coincide with known H ii regions and are close to or harbor massive young O stars or YSOs previously discovered by MUSE and Spitzer observations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2022

Laminated Permanent Magnets Enable Compact Magnetic Components in Current-Source Converters

Magnetic components have become one of the primary barriers to high power density converters, especially to current-source converters (CSCs). In CSCs, the inductors/transformers have a predominantly dc flux to store energy, which can be offset by standard permanent magnets (PMs). However, eddy currents in standard PMs induce significant losses and thermal stress for medium-frequency applications. This article proposes using laminated PMs to offset the dc flux while reducing eddy currents, leading to significant reductions in the size, cost, and losses of inductors/transformers. Furthermore, the laminated PMs’ optimal location, orientation, and distribution are investigated to generalize this approach for maximum benefits. Here, three-dimensional finite-element analysis simulation and hardware experiments are presented to validate the effectiveness of the proposed approach in a medium-frequency transformer (MFT) for CSCs. Compared with standard PMs, the proposed use of laminated PMs reduces aggregate core-plus-PM losses by 85% in experiments, and thus, relaxes the MFT thermal design. Finally, the proposed approach is experimentally validated in a 40 kVA flyback-type MFT for a soft-switching solid-state transformer. Compared to the traditional design without any PMs, the proposed design increases the saturation current by 46% while inducing only 5% more losses, leading to significant savings in magnetics cost and size.

30 DIRECT ENERGY CONVERSION↗

NASA NTRS1987

Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years.

Feigelson, Eric D.↗

NASA NTRS1990

Automated platform management system scheduling

The Platform Management System (PMS) has been established to coordinate the operation of platform systems and payloads. Since platforms are to be out of contact with the ground more than the manned base, PMS functions are required to be more autonomous than those of the manned base. Automated replanning and rescheduling will be required to effectively and efficiently meet mission goals. In a FY88 study, we developed a phased approach to automated PMS scheduling based upon use of the same scheduling engine in both ground and space components. In the past year, we implemented a baseline, first phase, PMS scheduler prototype. Presently we are integrating this scheduler into two NASA Goddard Space Flight Center testbeds, as the ground scheduler in the Scheduling Concepts, Architectures, and Networks Testbed and as the onboard scheduler in the PMS Testbed. We will investigate rescheduling issues, evaluated operational performance and enhance the prototype to demonstrate our evolutionary approach to automated PMS scheduling.

Hull, Larry G.↗

NASA NTRS1984

Performance management system enhancement and maintenance

The research described in this report concludes a two-year effort to develop a Performance Management System (PMS) for the NCC computers. PMS provides semi-automated monthly reports to NASA and contractor management on the status and performance of the NCC computers in the TDRSS program. Throughout 1984, PMS was tested, debugged, extended, and enhanced. Regular PMS monthly reports were produced and distributed. PMS continues to operate at the NCC under control of Bendix Corp. personnel.

Cleaver, T. G.↗

NASA NTRS1987

The naked T Tauri stars - The low-mass pre-main sequence unveiled

The search for low-mass premain-sequence (PMS) stars associated with X-ray sources in regions of star formation is discussed. The survey to date has revealed at least 30 low-mass PMS stars in the Tau-Aur region, and a comparable number in Oph. These stars are the naked T Tau stars, unveiled versions of the well-known classical T Tau stars. The properties of these newly discovered PMS stars and their relation to the classical T Tau stars are discussed, and it is concluded that the naked T Tau stars are the true low-mass PMS stars, and that the observable characteristics defining the classical T Tau stars are due to the interaction of an underlying, fairly normal star with a dominant circumstellar environment. The impact the naked T Tau stars are likely to have on models of the PMS evolution of low-mass stars is considered.

Walter, Frederick M.↗

NASA NTRS1987

Pre-main sequence stars

Observations of premain-sequence (PMS) stars obtained with the IUE satellite since its launch in 1978 are reviewed. The major types of PMS stars are listed and briefly characterized: T Tau stars, Herbig Ae stars, FU Ori objects, weak-emission PMS stars, and Herbig-Haro objects. The IUE data for a catalog of PMS objects are then presented in a table, graphs, and sample spectra and described in detail. Topics addressed include general spectral profiles, the Mg II h and k lines, the FUV emission lines, the UV continuum, and the impact of the IUE on astrophysical models of PMS stars. The need for observations with higher spectral resolution and much greater sensitivity is indicated, and the ability of the Hubble Space Telescope High-Resolution Spectrograph and the proposed NASA/ESA Lyman FUV Spectroscopic Explorer to meet these requirements is considered.

Imhoff, Catherine L.↗

NASA NTRS1989

Lithium abundances among solar-type pre-main-sequence stars

Measurements of Li I 6707 A line strengths were carried out for two samples of pre-main-sequence (PMS) stars (L 1641 and Taurus-Auriga), and the Li abundances estimated for PMS stars are compared with those deduced from observations of Li line strengths for main-sequence stars in the Alpha Persei cluster. It was found that the maximum Li abundances among the PMS stars with solar mass values greater than 1.0 exceed the maximum abundances for Alpha Per stars by at least 0.3 dex. Some PMS stars, including few apparently young stars, showed large (greater than 1.0 dex) Li depletion, and some apparently old PMS stars showed little or no depletion.

Strom, Karen M.↗

NASA NTRS1994

A multiwavelength study of star formation in the L1495E cloud in Taurus

We have carried out a deep (t = 30,000 s) X-ray search of the eastern portion of the L1495 cloud centered on the well-known weak line T Tauri star (WTTS) V410 Tau using the Roentgen Satellite (ROSAT) PSPC. This deep exposure enabled a search for candidate pre-main-sequence (PMS) objects in this cloud to a limit approximately 20 times more sensitive than that typical of the fields examined with the Einstein searches. Despite assertions that the PMS population in Taurus-Auriga is nearly completely known, this Stet survey revealed eight new PMS objects in a region 50 min in diameter, as compared to a previously known stellar population of 12 objects, including deeply embedded Infrared Astronomy Satellite (IRAS) sources. Spectroscopic and photometric observations enable us to place these objects in the H-R diagram. The newly discovered objects are predominantly stars of spectral-type M0 and later, and a large fraction (6/8) appear to be surrounded by circumstellar accretion disks as judged by their infrared excess and H alpha emission. We combined the data for these Stet-discovered objects with extant and new data for the previously identified PMS stars in this region to examine the history of star formation and the frequency distribution of stellar masses in this cloud. If the 'post-ROSAT' population is either complete or representative, we conclude (1) that star formation in L1495 East took place approximately 1 x 10(exp 6) yr ago and that the spread in ages is small; (2) the frequency distribution of masses, N(M), in this apparently coeval group appears to peak near log M = -0.5 (using masses derived from recently published PMS tracks of D'Antona & Mazzitelli and Swenson et al. and to decline toward lower masses. The derived N(log M) for L1495E compares well with the IMF derived from studies of stars in the solar neighborhood, a result which suggests that the Taurus-Auriga clouds are currently producing stars whose mass spectrum approximates the time/space-averaged IMF for the solar neighborhood.

Strom, Karen M.↗

NASA NTRS1995

Deep ROSAT HRI observations of the Orion nebula region

We present results from three deep ROSAT high-resolution imager observations of the Orion Nebula star-forming region. The X-ray images contain over 1500 cataloged stars in a roughly 0.8 sq deg region centered on the Trapezium. In all, 389 distinct X-ray sources have been detected, at least two-thirds of which are associated with a single proper-motion cluster member. X-ray emission is detected from stars of all spectral types, from massive O- and B-type components of the Trapezium to the coolest, low-mass pre-main-sequence (PMS) stars. In this paper we focus primarily on X-ray emission from the late-type PMS stars. Of the approximately 100 late-type cluster members with measured spectral types, approximately three-fourths have been detected; we have derived X-ray luminosity upper limits for the remaining stars. We found coronal X-ray emission turns on around spectral type F6, with the upper envelope of activity increasing with deceasing effective temperature. When plotted in an X-ray luminosity versus bolometric luminosity diagram, late-type PMS stars lie below a 'saturation' line corresponding to L(sub x)/L(sub bol) approximately 10(exp -3). For approximately solar-mass PMS stars, we find a median X-ray luminosity approximately 1 x 10(exp 30) ergs/s. The late G, K, and M stars exhibit nearly a two order of magnitude spread in X-ray luminosity and in L(sub x)/L(sub bol) at a given effective temperature. Plots of X-ray activity versus v sin i rotational velocity and rotational period appear to show no clear dependence of activity on rotation. However, because only a small fraction of late-type PMS stars in the Orion Nebula have measured v sin i or P(sub rot) and because of uncertainties in L(sub x) and L(sub x)/L(sub bol), we believe the data are not conclusive on this point. Light curves of the detected X-ray sources have revealed at least 10 strong X-ray flares with characteristic rise times greater than or approximately equal to 1 hr and decay times ranging from approximately 2 to 12 hr. All the flares have X-ray energies in excess of 3 x 10(exp 35) ergs. Many of the X-ray sources associated with late-type cluster members have been observed in more than one ROSAT HRI exposure, allowing us to look for variability on the approximately 1 yr timescale between HRI observations. A statistical analysis of the resulting count rate ratios suggests that at least one-fourth of the late-type cluster stars are significantly variable on this timescale.

Gagne, Marc↗

NASA NTRS1995

Coronagraphic imaging of pre-main-sequence stars: Remnant evvelopes of star formation seen in reflection

We have obtained R- and I-band coronagraphic images of the vicinities of 11 pre-main sequence (PMS) stars to search for faint, small-scale reflection nebulae. The inner radius of the search and the field of view are 1.9 arcsec and 1x1 arcmin, respectively. Reflection nebulae were imaged around RY Tau, T Tau,DG Tau, SU Aur, AB Aur, FU Ori, and Z CMa. No nebulae were detected around HBC 347, GG Tau, V773 Tau, and V830 Tau. Categorically speaking, most of the classical T Tauri program stars and all the FU Orionis-type program stars are associated with the reflection nebulae, while none of the weak-line T Tauri program stars are associated with nebulae. The detected nebulae range in size from 250 to 37 000 AU. From the brightness ratios of the stars and nebulae, we obtain a lower limit to the visual extinction of PMS star light through the nebulae of (A(sub V))(sub neb) = 0.1. The lower limits of masses and volume densities of the nebulae associated with the classical T Tauri stars are 10(exp-6) Solar mass and N(sub H) = 10(exp 5)/cu cm, respectively. Lower limits for the nebulae around FU Orionis stars are 10(exp -5) Solar mass and n(sub H) = 10 (exp 5)/cu cm, respectively. Some reflection nebulae may trace the illuminated surfaces of the optically thick dust nebulae, so these mass estimates are not stringent. All the PMS stars with associated nebulae are strong far-infrared emitters. Both the far-infrared emission and the reflection nebulae appear to originate from the remnant envelopes of star formation. The 100 micrometers emitting regions of SU Aur and FU Ori are likely to be cospatial with the reflection nebulae. A spatial discontinuity between FU Ori and its reflection nebula may explain the dip in the far-infrared spectral energy distribution at 60 micrometers. The warped, disk-like nebulae around T Tau and Z CMa are aligned with and embrace the inner star/circumstellar disk systems. The arc-shaped nebula around DG Tau may be in contact with the coaligned inner star/disk system. These three-reflection nebulae may trace the surfaces of pseudodisks from which matter accretes onto the stars or the inner circumstellar disks. 19 stellar objects brighter than I = 19 were detected around 9 program stars. Using a color-magnitude diagram, we have identified three new PMS candidates aroun Z CMa and one previously known PMS candidate, GG Tau/c.

Nakajima, Tadashi↗

DOE OSTI2022

Ultra High-Temperature Magnetic Bearing System for s-CO 2 Turbines/Expanders. Phase II Final Report

The goal of this project is to design and construct of a prototype of ultra-high temperature permanent magnet (UHT–PM), which provides the force to pull the spinning shaft towards the target position in the magnetic bearing (MB) clearance circle. This project will develop a PM biased MB system, that is actively cooled to the 550°C maximum operating temperature limit of PMs. The MB test environment will include 700°C, 40krpm and 4,000 psi requirements to advance the supercritical carbon dioxide (sCO 2 ) and other types of Brayton power cycle systems. The proposed novel MBs combine PMs for supplying the bias field and electromagnets for supplying the control field, both in UHT conditions. The choice of material is the UHT Sm-Co PMs (US patent 6,451,132) due to their significantly better thermal stability. The 6-pole homopolar design permits uninterrupted force delivery via a redundant control capability (US patent 7,429,811) even if 3 poles were to fail. The Phase I efforts was to focus on development and demonstration of component technologies and detailed design of full scale components and a demonstrator test rig for use in Phase II. UHT–PMs were produced and used in the MB actuator. The operating environment of the EEC-T550 Sm-Co magnet material could be extended by implementing active cooling. Electromagnetic coils imbedded in the MB provide forces to stabilize the shaft position at the target via sensing and control stages. Shaft position sensors enable to identify the present position of the spinning shaft relative to its desired target position in the MB clearance circle (air gap). Auxiliary bearings will be installed to provide a backup support system in the event that power to the MB fails or there is a fault in a device providing current to the MB coils. For control, reliability and safety reasons the sensors and auxiliary bearings are typically located as close as possible to the MBs, which exposes them to the same environmental conditions. Development of only the actuator for the UHT environment is an inadequate approach to complete integration of the MB system in the turbine/expander. Therefore the UHT sensor and auxiliary bearing were designed and developed along with the actively cooled, UHT-PM actuator development. Although shaft position sensors are commercially available (Kaman) they may cost up to $10k per channel, and a full 5 axis magnetic suspension is best implemented with up to 20 sensors. Once successfully completed, this project will significantly extend the operating environment capability for turbomachinery applications such as nuclear power, concentrated solar thermal, fossil fuel, geothermal, and shipboard propulsion. The further advancement of UHT-PM-MB will also strengthen the US position in PM technology, which is presently heavily dominated by China. The UHT Sm-Co magnet material that will be utilized in the proposed work has been developed exclusively by the project proposer. Many actuators, motors, generators and other MB applications will greatly benefit from the proposed work.

24 POWER TRANSMISSION AND DISTRIBUTION↗

NASA NTRS1987

An X-ray survey for pre-main-sequence stars in the Taurus-Auriga and Perseus molecular cloud complexes

Seventy-five fields from the Einstein X-Ray Observatory IPC detector between 3h and 5h right ascension and 15 deg and 35 deg declination are examined to search for X-ray-emitting low-mass pre-main-sequence (PMS) stars. Six such stars were previously found; they appear to be similar to T Tauri stars but without dense circumstellar envelopes or winds. Finding charts are presented for 59 X-ray sources that may be PMS stars. While some are likely to be spurious X-ray sources, chance coincidences with unrelated stars, or non-PMS stellar sources such as RS CVn type binaries, approximately half are probably X-ray-selected PMS stars.

Feigelson, E. D.↗

NASA NTRS1986

The Expert Project Management System (EPMS)

Successful project managers (PMs) have been shown to rely on 'intuition,' experience, and analogical reasoning heuristics. For new PMs to be trained and experienced PMs to avoid repeating others' mistakes, it is necessary to make the knowledge and heuristics of successful PMs more widely available. The preparers have evolved a model of PM thought processes over the last decade that is now ready to be implemented as a generic PM aid. This aid consists of a series of 'specialist' expert systems (CRITIC, LIBRARIAN, IDEA MAN, CRAFTSMAN, and WRITER) that communicate with each other via a 'blackboard' architecture. The various specialist expert systems are driven to support PM training and problem solving since any 'answers' they pass to the blackboard are subjected to conflict identification (AGENDA FORMULATOR) and GOAL SETTER inference engines.

Silverman, Barry G.↗

NASA NTRS1991

Pre-main-sequence evolution

The primary uncertainty that remains concerning the premain sequence (PMS) stage of stellar evolution is the possible role of accretion in the hydrodynamic stage. Possible PMS evolution scenarios are presented with a view to extant or potentially obtainable observational data that may unravel the details of PMS evolution. Attention is given to recent evolution calculations which encompass the role of rotation; it is concluded that the rotational feature of PMS can be tested within the framework of the chemical abundance of trace elements in the solar system, on the sun, and on solar analogs of various ages.

Sofia, S.↗

NASA NTRS1992

An IRAS study of pre-main sequence stars in B209

We have constructed high resolution IRAS maps of the B209 star forming region in the Taurus complex. By combining survey scans with pointed observations using advanced techniques specially developed to handle IRAS data in crowded fields, we have constructed images that reveal two new premain-sequence (PMS) objects. One of these, IRAS 04114+2757G, has FIR colors close to those of typical T Tauri stars and is probably associated with a faint stellar object visible on the POSS prints. The other new PMS source, IRAS 04111+2800G, is a deeply embedded object not detected at 12 microns and not optically visible. The object is projected close to the center of an ammonia core. Our detection of compact blue and red shifted (C-12)O emission peaks around the position of IRAS 04111+2800G confirms the PMS nature and youth of this object. We have examined the reasons for the exclusion of IRAS 04111+2800G and IRAS 04114+2757G from the IRAS Point Source Catalog and estimated the incompleteness of the currently known sample of embedded PMS stars in Taurus. The implications for the determination of evolutionary time scales in low mass star formation are discussed.

Prusti, T.↗