Search NASA⌕ Search

SEARCH · Search NASA

Results for “PRIMARY”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Computational Study of Primary Electrons in the Cusp Region of an Ion Engine's Discharge Chamber

In this work a computer code called PRIMA is used to study the motion of primary electrons in the magnetic cusp region of the discharge chamber of an ion engine. Even though the amount of wall area covered by the cusps is very small, the cusp regions are important because prior computational analyses have indicated that most primary electrons leave the discharge chamber through the cusps. The analysis presented here focuses on the cusp region only. The affects of the shape and size of the cusp region on primary electron travel are studied as well as the angle and location at which the electron enters the cusp region. These affects are quantified using the confinement length and the number density distributions of the primary electrons. In addition to these results comparisons of the results from PRIMA are made to experimental results for a cylindrical discharge chamber with two magnetic rings. These comparisons indicate the validity of the computer code called PRIMA.

Stueber, Thomas J.↗
NASA NTRS1998

Abnormalities of the QT interval in primary disorders of autonomic failure

BACKGROUND: Experimental evidence shows that activation of the autonomic nervous system influences ventricular repolarization and, therefore, the QT interval on the ECG. To test the hypothesis that the QT interval is abnormal in autonomic dysfunction, we examined ECGs in patients with severe primary autonomic failure and in patients with congenital dopamine beta-hydroxylase (DbetaH) deficiency who are unable to synthesize norepinephrine and epinephrine. SUBJECTS AND METHODS: Maximal QT and rate-corrected QT (QTc) intervals and adjusted QTc dispersion [(maximal QTc - minimum QTc on 12 lead ECG)/square root of the number of leads measured] were determined in blinded fashion from ECGs of 67 patients with primary autonomic failure (36 patients with multiple system atrophy [MSA], and 31 patients with pure autonomic failure [PAF]) and 17 age- and sex-matched healthy controls. ECGs of 5 patients with congenital DbetaH deficiency and 6 age- and sex-matched controls were also analyzed. RESULTS: Patients with MSA and PAF had significantly prolonged maximum QTc intervals (492+/-58 ms(1/2) and 502+/-61 ms(1/2) [mean +/- SD]), respectively, compared with controls (450+/-18 ms(1/2), P < .05 and P < .01, respectively). A similar but not significant trend was observed for QT. QTc dispersion was also increased in MSA (40+/-20 ms(1/2), P < .05 vs controls) and PAF patients (32+/-19 ms(1/2), NS) compared with controls (21+/-5 ms(1/2)). In contrast, patients with congenital DbetaH deficiency did not have significantly different RR, QT, QTc intervals, or QTc dispersion when compared with controls. CONCLUSIONS: Patients with primary autonomic failure who have combined parasympathetic and sympathetic failure have abnormally prolonged QT interval and increased QT dispersion. However, QT interval in patients with congenital DbetaH deficiency was not significantly different from controls. It is possible, therefore, that QT abnormalities in patients with primary autonomic failure are not solely caused by lesions of the sympathetic nervous system, and that the parasympathetic nervous system is likely to have a modulatory role in ventricular repolarization.

Non-NASA Center↗
NASA NTRS2007

Measurement of Primary Ejecta From Normal Incident Hypervelocity Impact on Lunar Regolith Simulant

The National Aeronautics and Space Administration (NASA) continues to make progress toward long-term lunar habitation. Critical to the design of a lunar habitat is an understanding of the lunar surface environment. A subject for further definition is the lunar primary ejecta environment. The document NASA SP-8013 was developed for the Apollo program and is the latest definition of the primary ejecta environment. There is concern that NASA SP-8013 may over-estimate the lunar primary ejecta environment. NASA's Meteoroid Environment Office (MEO) has initiated several tasks to improve the accuracy of our understanding of the lunar surface primary ejecta environment. This paper reports the results of experiments on projectile impact into pumice targets, simulating lunar regolith. The Ames Vertical Gun Range (AVGR) was used to accelerate spherical Pyrex projectiles of 0.29g to velocities ranging between 2.5 km/s and 5.18 km/s. Impact on the pumice target occurred at normal incidence. The ejected particles were detected by thin aluminum foil targets placed around the pumice target in a 0.5 Torr vacuum. A simplistic technique to characterize the ejected particles was formulated. Improvements to this technique will be discussed for implementation in future tests.

Edwards, David L.↗
NASA NTRS2018

Wave-Front Error Measurements and Alignment of CLASP2 Telescope with a Dual-Band Pass Cold Mirror Coated Primary Mirror

"Chromospheric LAyer Spectro-Polarimeter (CLASP2)" is the next sounding rocket experiment of the "Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)" that succeeded in observing for the first time the linear polarization spectra in the hydrogen Lyman- line (121.6 nm) and is scheduled to be launched in 2019. In CLASP2, we will carry out full Stokes-vector spectropolarimetric observations in the Mg II h & k lines near 280 nm with the spectro-polarimeter (SP), while imaging observations in the Lyman- line will be conducted with the slitjaw optics (SJ). For the wavelength selection of CLASP2, the primary mirror of the telescope uses a new dual-band pass cold mirror coating targeting both at 121.6 nm and 280 nm. Therefore, we have to perform again the alignment of the telescope after the installation of the recoated primary mirror. Before unmounting the primary mirror from the telescope structure, we measured the wave-front error (WFE) of the telescope. The measured WFE map was consistent with what we had before the CLASP flight, clearly indicating that the telescope alignment has been maintained even after the flight. After the re-coated primary mirror was installed the WFE was measured, and coma aberration was found to be larger. Finally, the secondary mirror shim adjustments were carried out based on the WFE measurements. In CLASP2 telescope, we improved a fitting method of WFE map (applying 8th terms circular Zernike polynomial tting instead of 37th terms circular Zernike fitting) and the improved method enables to achieve better performance than CLASP telescope. Indeed, WFE map obtained after the final shim adjustment indicated that the required specification (< 5:5 m RMS spot radius) that is more stringent than CLASP telescope was met.

chromosphere; polarimetry; sounding rocket↗
NASA NTRSDate not supplied

Metallic Vs Inflatable Primary Structure: A Comprehensive Trade for a Mars Transit Habitat

Large diameter inflatable habitat solutions are hypothesized to have an advantage over traditional metallic habitats of equal volume and functional requirements in terms of minimizing mass. A fair and comprehensive trade of metallic primary structure versus inflatable softgoods primary structure for a Mars Transit Habitat was conducted by The Boeing Company under the NASA Next Space Technologies for Exploration Partnerships-2 (NextSTEP-2)Appendix A contract in order to determine the minimum mass option from a system level. A Mars Transit Habitat is a major system mass driver because small increases in the mass can create large mass changes in the propulsive stage, adding complexity and cost to the mission. Three different vehicle configurations were traded using a fixed volume constraint and the same Ground Rules and Assumptions(GR&A)provided by NASA. The configurations were 1) 5.5 m diameter metallic habitat, 2) 7.0 m diameter metallic habitat, and 3) 7.63 m diameter inflatable habitat. In order to complete the trade, each configuration was analyzed and sized, but a system level approach had to be taken to ensure other aspects and subsystems besides the structure were captured. The primary functions (i.e. restraint layer, bladder, multilayer insulation [MLI], micro-meteoroid orbital debris [MMOD]) and strength advantages of softgoods are well understood, but there were other system level impacts that were discovered or addressed that are unique to softgoods. For the metallic structure, a modern and mass optimal material and manufacturing process was adopted to ensure the lightest weight options were evaluated. Two different aluminium lithium structures were evaluated, a longer length 5.5 m diameter and a shorter length 7 m diameter structure. The trade demonstrates that each configuration is feasible and close to the target dry mass for the Mars Transit Habitat Trans-Martian Injection burn. System level mass was the primary consideration, but since the three concepts were close in total mass, a clear winner did not arise. Secondary factors were evaluated such as architecture habitability (human factors), development considerations, on-orbit activation and outfitting, extensibility to other applications, and configuration flexibility. The aggregation of the lowest mass, most benefits, and fewest challenges resulted in the 5.5m diameter metallic configuration being the most favorable.

Matthew Ziglar↗
NASA NTRSDate not supplied

Anhydrous Primary Minerals in Ryugu, Ivuna, and Bennu

Samples returned from asteroid Ryugu are chemically and mineralogically similar to CI chondrites [e.g., 1–3]. Both are predominantly composed of low-temperature aqueously formed secondary minerals, whereas high-temperature anhydrous primary minerals, such as olivine, low-Ca pyroxene, spinel, and hibonite, are rarely present. Using secondary ion mass spectrometry (SIMS; Cameca ims-1280HR at Hokkaido University), we performed O [4] and Al–Mg [5] isotope measurements of anhydrous primary minerals in samples of Ryugu and the Ivuna CI chondrite to constrain their origin.Anhydrous primary minerals in our samples of Ryugu and Ivuna occur mostly as monomineralic isolated grains embedded in hydrated matrix. Their O-isotope compositions are distributed along the slope-1 line on the O three-isotope diagram and range from Δ17O ~ –23 to 0‰. Mg-Al spinel grains are 16O-rich (Δ17O ~ –23‰). Low-Ca pyroxene grains are 16O-poor (Δ17O ~ –5‰). Olivine grains show a bimodal distribution of O-isotope composition:10 of 34 grains measured are 16O-rich (Δ17O ~ –23‰) and 24 grains are 16O-poor (Δ17O ~ –7 to 0‰). We found refractory inclusions composed of Mg-Al spinel and hibonite, one from Ryugu and one from Ivuna. Also, in Ivuna, we found an amoeboid olivine aggregate ( AOA) composed of olivine, diopside, anorthite, and Mg-Al spinel and an inclusion composed of olivine and Mg-Al spinel. The minerals in all of these inclusions are 16O-rich (Δ17O ~ –24‰).The 16O-rich grains and inclusions are mineralogically and O-isotopically similar to calcium-aluminum–rich inclusions (CAIs) and AOAs reported in other carbonaceous chondrites [6, 7]. In addition, the initial 26Al/27Al ratios of the two spinel-hibonite inclusions are inferred as ~4.4 × 10–5, also similar to most CAIs in carbonaceous chondrites [6, 8]. The range of Δ17O values for the 16O-poor olivine and low-Ca pyroxene grains is consistent withthat of these minerals in chondrules in most carbonaceous chondrites [9]. Moreover, the most frequent Δ17O value (–6‰) for Mg-rich (Mg# > 97) olivine grains is identical to those for chondrules. Although CI chondrites and Ryugu samples are devoid of chondrules, the 16O-poor grains most likely represent fragments of chondrule-like objects. The presence of both 16O-poor chondrule-like and 16O-rich refractory inclusion–like minerals in Ryugu and Ivuna suggests that some of their building blocks are similar to those of other carbonaceous chondrite groups. They both probably formed in the inner solar protoplanetary disk and were subsequently transported outward.Preliminary data for petrography of asteroid Bennu samples and chemical and isotopic compositions of theiranhydrous primary minerals will also be presented in the meeting.

N Kawasaki↗
NASA NTRSDate not supplied

Nutrient Controls on Net Primary Production Decline in the Subtropical North Atlantic

The subtropical North Atlantic Ocean (STNA) has been experiencing a steady decline in both Chlorophyll a (the primary photosynthetic pigment in phytoplankton used to identify abundance in the ocean) and net primary production (the net amount carbon fixed in the surface ocean by phytoplankton after losses to respiration). This decline is spread across the entire STNA and has been ongoing since the beginning of the satellite ocean color record in 1997. Previous work has attributed these changes to decreased nutrient exchange between nutrient-poor surface waters and nutrient-rich deep waters resulting from increased stratification driven by surface warming due to climate change. Our results from an analysis of satellite data, Argo float data, and historical cruise data show significant inconsistencies with this hypothesis. We observe a trend of increased stratification for half the STNA basin but decreased stratification in the other half. Where we see increased stratification, we also see changes in nitrate that would result in an increased delivery of nitrate to surface waters if vertical transport across the stratified layers was the dominant source of nutrients. Our working hypothesis is that changes in circulation in the subtropical gyre have resulted in an altered mix of source waters with distinct nutrient characteristics. The mechanism behind the decline in primary production in the STNA remains unclear. We will use the ECCO-Darwin data-assimilative global ocean biogeochemistry model to further investigate the mechanisms behind the observed changes in production and nutrients in the STNA.

Nutrient↗
NASA NTRS1968

Telescope mount with azimuth-only primary

In large aperture telescope primary reflectors, the primary mirror is fixed with respect to the gravity vector to avoid varying gravity deflection problems. The primary reflector does not become distorted in various positions nor in changing positions.

Wells, W. H.↗
NASA NTRS1965

Primary feeds for the Goonhilly satellite-communication aerial

The 85-ft. diameter aerial at Goonhilly Downs, Cornwall uses a focal-plane paraboloidal reflector illuminated from a primary feed at the focus, Circularly polarized waves are transmitted and received. For optimum gain and uniformity of the aerial radiation patterns, circular symmetry of the primary feed radiation pattern is desirable. The primary feed has therefore been made circularly symmetric.

GROUND STATION↗
NASA NTRS1973

Internal performance of a wedge nozzle for a supersonic cruise aircraft with a multispoke primary for noise suppression

Nozzle performance was obtained with cold primary and secondary flows over a range of nozzle pressure ratio from 2 to 31 and corrected secondary-to primary-flow ratio from 0 to 11 percent. Several fixed shroud positions were tested to simulate a translating outer cylindrical shroud to provide data for both supersonic cruise and takeoff configurations. The addition of 14 spokes in the primary nozzle for noise suppression reduced the thrust efficiency 3 percent at supersonic cruise and 4.5 percent at takeoff.

Johns, A. L.↗
NASA NTRS1976

Apollo experience report guidance and control systems: Primary guidance, navigation, and control system development

The primary guidance, navigation, and control systems for both the lunar module and the command module are described. Development of the Apollo primary guidance systems is traced from adaptation of the Polaris Mark II system through evolution from Block I to Block II configurations; the discussion includes design concepts used, test and qualification programs performed, and major problems encountered. The major subsystems (inertial, computer, and optical) are covered. Separate sections on the inertial components (gyroscopes and accelerometers) are presented because these components represent a major contribution to the success of the primary guidance, navigation, and control system.

Holley, M. D.↗
NASA NTRS1976

Phenomenological model of nuclear primary air showers

The development of proton primary air showers is described in terms of a model based on a hadron core plus an electromagnetic cascade. The muon component is neglected. The model uses three parameters: a rate at which hadron core energy is converted into electromagnetic cascade energy and a two-parameter sea-level shower-age function. By assuming an interaction length for the primary nucleus, the model is extended to nuclear primaries. Both models are applied over the energy range from 10 to the 13th power to 10 to the 21st power eV. Both models describe the size and age structure (neglecting muons) from a depth of 342 to 2052 g/sq cm.

Tompkins, D. R., Jr.↗
NASA NTRS1978

Primary reflector for solar energy collection systems

A fixed, linear, ground-based primary reflector is disclosed which has an extended curved sawtooth-contoured surface covered with a metalized polymeric reflecting material. The device reflects solar energy to a movably supported collector that is kept at the concentrated line focus of the reflector primary. The primary reflector may be constructed by a process utilizing well-known freeway paving machinery.

Miller, C. G.↗
NASA NTRS1979

Primary reflector for solar energy collection systems and method of making same

Solar energy is reflected to a movably supported collector that is kept at the concentrated line focus of the reflector primary by a fixed, linear, ground-based primary reflector having an extended curved sawtooth contoured surface covered with a metalized polymeric reflecting material. The primary reflector was constructed by a process utilizing well-known freeway paving machinery.

Miller, C. G.↗
NASA NTRS1978

The response of an RC line MWPC to primary cosmic rays

A simple 50 x 50 sq cm MWPC plane was arranged as an RC-line and flown on a balloon flight with the MSFC-UAH Cosmic Ray experiment. Positions of primary cosmic ray tracks in the RC-line were determined by the risetime method and compared with the expected position as indicated by a best line fitted through four planes of the conventional MWPC hodoscope. Mean errors were estimated for sea-level muons, and CNO group and iron group particles. It is believed that the delta-rays accompanying the primaries degraded the position resolution. Measured standard deviations allowing for uncertainty in the true track position are of the order of 1 cm or less in the primary charge region between 7 and 26.

Gregory, J. C.↗
NASA NTRS1978

Effects of secondary electrons from heavy primary cosmic rays in a MWPC hodoscope

A multi-wire proportional counter hodoscope, efficient for both primary track recovery and reading out all wires set by secondary electrons, was flown in a balloon flight experiment covering the range of cosmic ray charge from 4 to 28 and kinetic energy T greater than 0.5 GeV/nucleon. Data on the secondary electron effects in the hodoscope is presented for primary nuclei between C and Fe and kinetic energies between 0.6 and 7.0 GeV/nucleon. The total number of affected anodes in the hodoscope is seen to increase linearly with the cosmic ray change, with a slope that depends strongly on energy over this limited primary energy range.

Derrickson, J. H.↗
NASA NTRS1979

The performance of primary Cs beam clocks using quadrupole and hexapole deflection systems. Consequences for time keeping

Since 1978 the time-and-frequency standard CS1 of the Physikalisch-Technische Bundesanstalt (PTB) has operated continuously as a 'primary clock'. Its uncertainty (7.1 to the negative 15th power) is considerably smaller than that of the other existing primary standards. The CS1 is equipped with a combination of quadrupole and hexapole magnets and uses a longitudinal C-field. Consequences of utilizing primary clocks of this quality for the generation of the International Atomic Time Scale TAI are discussed.

Becker, G.↗
NASA NTRS1980

Primary cosmic ray positrons and galactic annihilation radiation

The observation (Leventhal et al, 1978) of positron annihilation radiation at 0.511 MeV from the direction of the Galactic Center is reexamined, suggesting the possibility of a primary positron component of the cosmic rays. The observed 0.511 MeV emission requires a positron production rate nearly two orders of magnitude greater than the production rate of secondary cosmic ray positrons from pion decay produced in cosmic ray interactions. Possible sources of positrons are reviewed with both supernovae and pulsars appearing to be the more likely candidates. If only about 1% of these positrons were accelerated along with the cosmic ray nucleons and electrons to energies not less than 100 MeV, it is believed that these primary positrons would be comparable in intensity to those secondary positrons resulting from pion decay. Some observational evidence for the existence of primary positrons in the cosmic rays is also discussed.

Lingenfelter, R. E.↗