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At least 541 records · Page 30

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NASA NTRS1974

Maximum power transfer in n ports with passive loads

The problem of drawing maximum power from an n port by suitably terminating it with another passive n port is studied. Methods are derived for determining sets of passive impedance matrices which are 'optimal' in the sense that they draw maximum power from a given n port. It is shown that, in all nontrivial cases, if there exists any (passive or otherwise) optimum-load impedance matrix, then there exist, in fact, infinitely many passive optimum-load impedance matrices.

Vidyasagar, M.↗

NASA NTRS1973

Eddy-current measurements of thickness of high-temperature coatings

The eddy-current technique was applied to measuring the thickness of a fused silicide coating on a refractory alloy slab. Phase and magnitude of the test signal were measured at four places in 13 different samples, and thickness of coating was computed on the basis of each of these quantities. These results were then compared with those obtained by conventional metallographic methods. Phase-based measurements were most reliable, and the maximum error between the metallographically determined thickness and the thickness as determined by the least squares fit to the phase measurements was less than 0.01 mm (about 1%). Photomicrography of a typical sample shows that a large source of error resides in the fact that two regions - an outer rough region and an inner uniform region - of the coating layer exist rather than the single region upon which the calculations were based.

Dodd, C. V.↗

NASA NTRS1974

Hydraulic concentration of magnetic fields in the solar photosphere. II - Bernoulli effect

The magnetic filaments in the solar photosphere are subject to vigorous kneading and massaging by the convective turbulence at, and beneath, the visible surface. It is shown that the Bernoulli effect of the consequent surging of fluid up and down along the filaments is a major factor in concentrating the magnetic pressure of the filament (the mean square field). The mean field is also increased if the phase velocity of the external massaging exceeds the Alfven speed within the filament. The net observational magnetic result of the surging, then, depends upon the response of the observing instrument, and whether it essentially observes the mean field, the rms field, or whether there are saturation effects. It is suggested that the chromospheric mottles (spicules) seen in H alpha are in fact the intense magnetic filaments that carry most of the magnetic flux across the photospheric boundary of the sun.

Parker, E. N.↗

NASA NTRS1974

Auger analysis of films formed on metals in sliding contact with halogenated polymers

The use of Auger electron spectroscopy (AES) to search for transferred polymer must contend with the fact that there has been no published work on Auger analysis of polymers. Since this is a new area for AES, the Auger spectra of polymers and of halogenated polymers in particular is discussed. It is shown that the Auger spectra of halogenated polymers have certain characteristics that permit an assessment of whether a polymeric transfer film has been established by sliding contact. The discussion is general and the concepts should be useful in considering the Auger analysis of any polymer. The polymers chosen for this study are the halogenated polymers polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), and polychlorotrifluorethylene (PCTFE).

Pepper, S. V.↗

NASA NTRS1974

Magnetic properties of Apollo 16 samples and implications for their mode of formation

The Apollo 16 crystalline rocks have a greater average percentage of metallic iron than any other lunar material and are the most reduced in terms of their metallic iron/total iron ratio. They have greater metal content than the mare basalts, the only primary igneous rocks on the moon, and more iron metal than the associated Apollo 16 breccias and soils. This fact and the relatively coarse grain size suggest reduction of the iron during the formation of the crystalline rocks, probably during melts and partial melts in an impact base surge deposit.

Pearce, G. W.↗

NASA NTRS1974

Angiocardiographic methods for determination of left ventricular geometry and volume

Methods are described for calculating left ventricular (LV) dimensions and chamber volumes from radiographic films. The use of biplane films for the calculation of LV volume and volume change is based on the assumption of an ellipsoidal geometry. Calculation of LV volumes from biplane films usually overestimated known volumes in postmortem hearts regardless of the methods used for volume calculation. The reasons for this are probably best explained by the fact that a smooth-surface ellipse is used to represent the irregular cavity of the LV chamber. LV volume calculated from data in a single plane compared favorably and closely with volumes calculated from biplane films. A table of normal values of ventricular volume established by angiographic studies is presented.

Sandler, H.↗

NASA NTRS1974

Climatic variations on Mars. I - Astronomical theory of insolation

Description of variations in the solar insolation on Mars that result from oscillations of the orbital eccentricity and the obliquity of the planet. Changes in the eccentricity and obliquity are produced by gravitation perturbations from the sun and the other planets, and a detailed account of the time evolution of these quantities is given. Particular attention is paid to the obliquity oscillations, which exert a strong influence on the climate of Mars. Changes in the earth's obliquity are also calculated, and its behavior is contrasted with that of Mars. Although the eccentricity produces important north-south seasonal asymmetries, a change in the obliquity causes a strong latitudinal redistribution of the solar insolation. Especially noteworthy is the fact that the yearly insolation at the poles of Mars varies by over 100% between the extremes of the obliquity range.

Ward, W. R.↗

NASA NTRS1974

Jupiter after Pioneer - A progress report

In December 1973, Pioneer 10 became the first spacecraft to reach the vicinity of Jupiter. The spacecraft passed through the Jovian magnetosphere in two weeks and sent back more than 300 pictures of the big planet. Measurements were conducted of EM fields, energetic particles, and micrometeoroids. Radio occultations observed are discussed along with observations in the infrared and ultraviolet range, magnetic measurements, questions of trajectory analysis, and data obtained with the aid of a plasma analyzer. Pioneer 10 has confirmed as inescapable the fact that Jupiter radiates more energy than it receives from the sun.

Mcdonough, T. R.↗

NASA NTRS1974

Dicarboxylic acids from electric discharge

An investigation was conducted concerning the possible synthesis of a suite of dicarboxylic acids similar to that found in the Murchison meteorite. The investigation included the conduction of a chemical evolution experiment which simulated electric discharge through the primitive atmosphere of the earth. The suite of dicarboxylic acids obtained in the electric discharge experiment is similar to that of the Murchison meteorite, except for the fact that 2-chlorosuccinic acid is present in the spark discharge.

Zeitman, B.↗

NASA NTRS1974

Remote profiling of lake ice thickness using a short pulse radar system aboard a C-47 aircraft

Description of the design and operation of two new short-pulse radar systems developed for use aboard aircraft for remote profiling of lake ice thickness. The principle of operation is based on the fact that the return signal is composed of a pulse return from the top of the ice and another, delayed in time, from the ice-water interface. The delay time between these two pulses directly gives the ice thickness when allowance is made for the slower RF propagation through the ice. The two systems are the S band and the C band systems, and their comparative merits are discussed.

Cooper, D. W.↗

NASA NTRS1974

Production of edible carbohydrates from formaldehyde in a spacecraft. pH variations in the calcium hydroxide catalyzed formose reaction

The study of the calcium hydroxide catalyzed condensation of formaldehyde was extended to a batch reactor system. Decreases in pH were observed, often in the acid regime, when using this basic catalyst. This observation was shown to be similar to results obtained by others using less basic catalysts in the batch mode. The relative rates of these reactions are different in a batch reactor than in a continuous stirred tank reactor. This difference in relative rates is due to the fact that at any degree of advancement in the batch system, the products have a history of previous products, pH, and dissolved catalyst. The relative rate differences can be expected to yield a different nature of product sugars for the two types of reactors.

Weiss, A. H.↗

NASA NTRS1974

Water survey of Canada: Application for use of ERTS-A for retransmission of water resources data

The author has identified the following significant results. The fact that water resources data can be retransmitted from remote areas of Canada by polar orbiting spacecraft to users in population centers on a near real time basis reliably, accurately, and at relative low cost continues to be demonstrated. Over 60,000 transmissions from the nine data collection platforms installed at Water Survey of Canada gauging stations have been received. The stage and ice-out data retransmitted via ERTS-1 have been plotted on a chart record produced by a water stage servo-manometer installed on the Albany River. The stage increased smoothly until shortly after noon on May 19, 1974. During this time the indicator showed that the ice surface was intact. The stage then dropped sharply and the indicator read that the ice was out. The erratic chart trace after that was consistent with the assumption that the ice surface had broken up and that some short duration jams of broken ice were occurring.

Halliday, R. A.↗

NASA NTRS1974

Determining particle density using known material Hugeniot curves

A method is detailed to determine the density of particles wherein the closing velocity is known between the impacting particles and a plate of known material. Either the shock wave velocity or the material velocity produced in the plate upon impact by an unknown material particle is determined and compared with the corresponding shock wave or material velocity that would by produced by different known material particles having the same closing velocity upon impact with the plate. The unknown material particle density is derived by obtaining a coincidence of the shock wave velocity or material velocity conditions initially produced upon impact between the known material plate and one of the different material particles and from the fact that shock wave velocity and material velocity are ordered on the impacting particle material density alone.

Dibattista, J. D.↗

NASA NTRS1974

A study of the operation of selected national research facilities

The operation of national research facilities was studied. Conclusions of the study show that a strong resident scientific staff is required for successful facility operation. No unique scheme of scientific management is revealed except for the obvious fact that the management must be responsive to the users needs and requirements. Users groups provide a convenient channel through which these needs and requirements are communicated.

Eisner, M.↗

NASA NTRS1974

A General Theory of Unsteady Compressible Potential Aerodynamics

The general theory of potential aerodynamic flow around a lifting body having arbitrary shape and motion is presented. By using the Green function method, an integral representation for the potential is obtained for both supersonic and subsonic flow. Under small perturbation assumption, the potential at any point, P, in the field depends only upon the values of the potential and its normal derivative on the surface, sigma, of the body. Hence, if the point P approaches the surface of the body, the representation reduces to an integro-differential equation relating the potential and its normal derivative (which is known from the boundary conditions) on the surface sigma. For the important practical case of small harmonic oscillation around a rest position, the equation reduces to a two-dimensional Fredholm integral equation of second-type. It is shown that this equation reduces properly to the lifting surface theories as well as other classical mathematical formulas. The question of uniqueness is examined and it is shown that, for thin wings, the operator becomes singular as the thickness approaches zero. This fact may yield numerical problems for very thin wings.

Morino, L.↗

NASA NTRS1974

Experimental determination of the principal moments of inertia of the Helios prototype spacecraft

The moment of inertia of the Helios Spacecraft about its spin axis was determined by use of a roll-fixture using two sets of crossed flexure pivots as elastic constraints. The test procedure entailed measurement of a system oscillation period with each of a set of added moment-of-inertia increments. The tare effect of the fixture was determined by a like process and was subtracted from the gross value to yield the spacecraft roll moment of inertia to an estimated accuracy of 0.2%. Lateral moments of inertia (i.e., about each of three axes normal to the spin axis) were determined by a gravity pendulum method that makes use of the fact that any physical pendulum has a minimum period of oscillation determined by a particular distance from the axis of rotation to the system center of gravity.

Gayman, W. H.↗

NASA NTRS1975

Auxiliary propulsion thruster performance with ion machined accelerator grids

A substantial improvement in the performance of an 8-centimeter-diameter auxiliary propulsion thruster was achieved by reducing the diameter of the accelerator grid apertures. The accelerator grid hole geometry was defined by ion machining accelerator grids on an 8-centimeter thruster at thrust levels of 2.2, 4.4, and 6.7 millinewtons was (mN). A thruster with an ion machined accelerator grid was operated at a thrust of 4.4 mN for 1000 hours. The discharge propellant utilization was 92% at an eV/ion of 338. Thruster performance and accelerator grid hole geometry was documented as a function of thrust level. It was also determined that the small hole accelerator grid has a very low backstreaming voltage limit. In fact the thruster can be operated with the acclerator grid held at neutralizer tip potential.

Hudson, W. R.↗

NASA NTRS1975

Space science

A fact sheet on the NASA space science program is presented. Some of the subjects considered include the following: (1) the Orbiting Astronomical Observatory, (2) the Orbiting Solar Observatory, (3) the Small Astronomy Satellite, (4) lunar programs, (5) planetary programs using the Mariner, Pioneer 10, and Viking space probes, and (6) the Scout, Thor-Delta, and Atlas-Centaur launch vehicles. For each program there is a description of the effort, the schedule, management, program officials, and funding aspects in outline form.

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