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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 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Aquatic Invertebrate Development Working Group

Little definitive evidence exists to show that gravity plays a major role in embyrogenesis of aquatic invertebrates. Two reasons for this may be: (1) few studies have been done that emphasize the role of gravity; and (2) there simply may not be any gravity effect. The buoyant nature of the aquatic environment could have obscured any evolutionary effect of gravity. The small size of most eggs and their apparent lack of orientation suggests reduced gravitational influence. Therefore, it is recommended that the term development, as applied to aquatic invertebrates, be loosely defined to encompass behavioral and morphological parameters for which baseline data already exist.

Meyers, D.↗
NASA NTRS1985

Report of the Microbial Development Working Group

In formulating ideas on the relationship of gravity to the development, growth, and reproduction of microorganisms, a rather liberal definition of microorganisms is used which includes bacteria, yeasts, protists, filamentous fungi, and single cells in culture. A principal advantage of microorganisms as experimental subjects is the rigor with which they can be defined and controlled. As single cells, each cell may be regarded as identical to the others in the population. This property applies to the morphology, physiology, and genetic parameters of the cells. The growth and development of the population is subject to precise manipulation as the nutritional requirements are known and minimal media formulations have been developed. Growth and differentiation can be manipulated in a variety of ways, such as alteration of the culture temperature and food supply, or by use of mutants. Finally, the short generation times of microorganisms provide the opportunity to conduct multigenerational studies within practical time limits and, in a similar vein, cellular responses to various stimuli or stresses are conveniently monitored because of the rapid response times of single cells.

Nelson, G.↗
NASA NTRS1984

Recent work on a microwave ion source

The performance of a microwave (2.45 GHz) plasma-disk ion source using a cylindrical microwave cavity is described. The operating characteristics in argon and xenon gases with 50-200 W of input power and gas flow rates from 10-80 sccm are presented. In particular, extracted beam current versus accelerating voltage, and specific energy vs. mass utilization efficiency and extracted beam current are presented. Double Langmuir probe measurements indicate that electron densities in excess of 10 to the 12th per cu cm can be readily achieved in the microwave generated plasma.

Asmussen, J.↗
NASA NTRS1985

Strategy for reflector pattern calculation: Let the computer do the work

Using high frequency approximations, the secondary pattern of a reflector antenna can be calculated by numerically evaluating a radiation integral I(u,v). In recent years, tremendous effort has been expended to reducing I(u,v) to Fourier integrals. These reduction schemes are invariably reflector geometry dependent. Hence, different analyses/computer software development must be carried out for different reflector shapes/boundaries. it is pointed out, that, as the computer power improves, these reduction schemes are no longer necessary. Comparable accuracy and computation time can be achieved by evaluating I(u,v) by a brute force FFT described in this note. Furthermore, there is virtually no restriction on the reflector geometry by using the brute force FFT.

Lam, P. T.↗
NASA NTRS1985

Report from the Transfer-Laser Working Group

Light absorbing molecules and lasing molecules were discussed with regard to satisfying the following criteria for blackbody transfer lasers: (1) Good absorbers of blackbody radiation at 1500-2000 K; (2) Near resonant energy transfer from the absorbing gas to the lasant, provided not too many quantum number changes are required; (3) Dipole-dipole interactions for most efficient energy transfer; (4) Exothermic forward transfer reaction; (5) Polyatomic lasant molecules with at least two fundamental vibrational modes to ensure one or more states between the upper laser level and the ground state; (6) Polyatomic lasant molecules should not be so large or so complex that fast V-V relaxation occurs; (7) Metastable upper laser level for maintaining inversion, at least with respect to radiative and V-V decay; (8) Fast V-V into the upper laser level and out of the lower laser level; and (9) Lasing wavelengths less than 10.6 microns. Possible combinations of absorbers and lasants satisfying these criteria were discussed.

Meador, W. E.↗
NASA NTRS1986

Working Group on Circumstellar/Interstellar Relationships

Stars of various types are believed to be the main source of interstellar (IS) dust grans. The most important confirmed source is evolved giant and supergiant stars. Supernovae also contribute to the mass loss. The differences between circumstellar (CS) and IS dust were reviewed using the following topics: alteration of CS dust grains, size distribution, space observation of CS and IS dust, comparison of infrared spectra, isotopic signatures, Magellanic clouds and nearby galaxies, life cycles of dust grains, and physical and chemical data.

Glassgold, A. E.↗
NASA NTRS1985

Permanent presence - Making it work; Proceedings of the Twenty-second Goddard Memorial Symposium, Greenbelt, MD, March 15, 16, 1984

Among the topics discussed are: electrophoresis operations in space for pharmaceutical processing; Space Station program operations; and Space Station platform configurations. Consideration is also given to: the human role in future space systems; EVA operations; spherical shell applications; and a container material for alloy processing in near-zero gravity. Among additional topics discussed are: Space Station platform thermal control; environmental control and life support for an evolving capability manned Space Station; and the commercial prospects of the Space Station.

Bekey, I.↗
NASA NTRS1986

Strategy for reflector pattern calculation - Let the computer do the work

Using high frequency approximations, the secondary pattern of a reflector antenna can be calculated by numerically evaluating a radiation integral I(u,v). In recent years, tremendous effort has been expended to reducing I(u,v) to Fourier integrals. These reduction schemes are invariably reflector geometry dependent. Hence, different analyses/computer software development must be carried out for different reflector shapes/boundaries. It is pointed out, that, as the computer power improves, these reduction schemes are no longer necessary. Comparable accuracy and computation time can be achieved by evaluating I(u,v) by a brute force FFT described in this note. Furthermore, there is virtually no restriction on the reflector geometry by using the brute force FFT.

Lam, P. T.↗
NASA NTRS1985

Astrophysics and the Space Station - Executive summary of the NASA Working Group

Current plans for astrophysics experiments using the Space Station are summarized. The planning history is briefly traced; the fundamental roles of the Station as observatory, assembly plant, and service point for free-flying astrophysics platforms are considered; the NASA astrophysics programs are described; the chief outstanding problems are listed; and the need for smaller experiments is stressed. Lists of desired Station performance parameters and charts showing projected completion dates for Station components are provided.

Pellerin, C. J.↗
NASA NTRS1987

Gas tungsten arc welding in a microgravity environment: Work done on GAS payload G-169

GAS payload G-169 is discussed. G-169 contains a computer-controlled Gas Tungsten Arc Welder. The equipment design, problem analysis, and problem solutions are presented. Analysis of data gathered from other microgravity arc welding and terrestrial Gas Tungsten Arc Welding (GTAW) experiments are discussed in relation to the predicted results for the GTAW to be performed in microgravity with payload G-169.

Welcher, Blake A.↗
NASA NTRS1987

Remedial training: Will CRM work for everyone

The subject of those pilots who seem unresponsive to Cockpit Resource Management (CRM) training is addressed. Attention is directed to the need and opportunity for remedial action. Emphasis is given to the requirement for new perspectives and additional training resources. It is also argued that, contrary to conventional training wisdom, such individuals do not represent a hard core which is beyond assistance. Some evidence is offered that such a new perspective will lend itself to a wider appreciation of certain specific training needs. The role of appropriately trained specialists is briefly outlined, and a selected bibliography is attached. The combined experiences of several Pilot Advisory Groups (PAG's) within IFALPA member association form the basis for this discussion. It does not purport to desribe the activities of any one PAG. While much of the activities of PAG's have no relevance to CRM, there are clearly some very important points of intersection. The relevance of these points to diagnostic skills, and remedial training in the general domain of CRM is made obvious.

Johnston, A. N.↗
NASA NTRS1987

Commit your works to the Lord, and your thoughts shall be established (Prov. 16:3). Inter-stable control systems

Algebraic structures are discussed for control systems that maintain stability in the presence of resonance uncertainties. Dual algebraic operations serve as elementary connections that propagate the stability of inter-stable subsystems. Frequency responses within complex half-planes define different types of inter-stability. Dominance between incompatible types is discussed. Inter-stability produces sufficient but unnecessary stability conditions, except for conservative systems where the conditions become also necessary. Multivariable systems, colocation of actuator and sensor, and virtual colocation are treated. Instead of passivity, inter-stability relates stability to the mapping of poles and zeros by transfer functions and transfer matrices. Inter-stability determines stability on the subsystem level, is less complex even for multivariable systems, adds design flexibility, and relaxes the dynamic data problem of large systems such as space stations.

Vonpragenau, George L.↗