Showing papers by "Jet Propulsion Laboratory published in 1968"
TL;DR: Lunar Orbiter tracking data have been processed to supply a qualitatively consistent gravimetric map of the lunar nearside and the results indicate that there are large mass concentrations under the lunar ringed maria.
Abstract: Lunar Orbiter tracking data have been processed to supply a qualitatively consistent gravimetric map of the lunar nearside. While a simplified model was employed, the results indicate that there are large mass concentrations under the lunar ringed maria. These mass concentrations may have important implications for the various theories regarding lunar history.
424 citations
TL;DR: The products of pyrolysis of n-octacosane (C28H58) have been identified by capillary gas-liquid chromatography as discussed by the authors, and the reaction is affected by clay minerals.
Abstract: The products of pyrolysis of n-octacosane (C28H58) have been identified by capillary gas-liquid chromatography The reaction is affected by clay minerals The experiments provide further support for the view that thermal and catalytic alteration of the organic material present in sediments in part explains the genesis of petroleum and other hydrocarbon minerals
129 citations
TL;DR: The alpha-scattering experiment aboard Surveyor VII has provided a chemical analysis of the moon in the area of the crater Tycho, and preliminary results indicate a chemical composition similar to that already found at two mare sites, but with a lower concentration of elements of the iron group.
Abstract: The alpha-scattering experiment aboard Surveyor VII has provided a chemical analysis of the moon in the area of the crater Tycho. The preliminary results indicate a chemical composition similar to that already found at two mare sites, but with a lower concentration of elements of the iron group (titanium through copper).
85 citations
TL;DR: Rotating detonation-like wave concept explains phenomenon during destructive liquid rocket resonant combustion mode as mentioned in this paper, and it is used to explain the phenomenon during the launch of a liquid rocket.
Abstract: Rotating detonation-like wave concept explains phenomenon during destructive liquid rocket resonant combustion mode
66 citations
TL;DR: Lunar mascons, interpreting lunar gravitational field anomalies over maria in terms of near- surface slab-like model for maria structure suggests that the structure of maria is more like a slab than a sphere.
Abstract: Lunar mascons, interpreting lunar gravitational field anomalies over maria in terms of near- surface slab-like model for maria structure
62 citations
TL;DR: Stiffness matrices bandwidth minimization by automatic node relabeling in equilibrium problems of lumper-parameter systems is studied.
Abstract: Stiffness matrices bandwidth minimization by automatic node relabeling in equilibrium problems of lumper-parameter systems
50 citations
TL;DR: In this article, a general procedure for the solution of problems of elastoplasticity is developed by using the finite element and direct stiffness method, piecewise linear load deflection relationship, and step-by-step computational algorithm.
Abstract: By using the finite element and direct stiffness method, piecewise linear load deflection relationship, and step-by-step computational algorithm, a general procedure for the solution of problems of elastoplasticity is developed. The change of material properties at each step is expressed in the general differential form of Prandtl-Reuss equations of the theory of plastic deformations, with special treatment of the plane strain case. The effect of initial stresses is also considered when the rotations at each step are not negligible, although the strains are assumed small compared to unity. Application of the principle of virtual work to define the equilibrium of an element subject to initial and additional stresses yields a geometrical stiffness matrix which satisfies macroscopic equilibrium requirements. Computational difficulties arising from the repeated solution of large numbers of linear simultaneous equations are overcome by using an iteration method with an over-relaxation factor. The accuracy of the propagated solution is improved by the application of half-step procedure, which is a special case of the Runge-Kutta method.
45 citations
42 citations
TL;DR: Kaufman thrustor with curved stainless steel accelerating grid system noting operation, efficiency, plasma instability, etc. as discussed by the authors, which was used for the first time in the early 1990s.
Abstract: Kaufman thrustor with curved stainless steel accelerating grid system noting operation, efficiency, plasma instability, etc
32 citations
TL;DR: In this paper, the thermal entrance region for a steady, constant-property, uniform laminar flow of an electrically conducting fluid in a constant cross-section, parallel-plate channel with isothermal, electrically nonconducting walls is presented.
31 citations
Patent•
28 Mar 1968TL;DR: In this article, a sample cell is fabricated by supporting a lens barrel within the aperture, and a molten portion of glass is deposited in the lens barrel and cooled while in a horizontal position to form a lens having an acceptable angle of 130* to 170* at an aperture of f7 or below.
Abstract: Apparatus suitable for receiving a sample for optimetric analysis along with a method of fabricating the apparatus is disclosed. The apparatus includes a sample cell comprising an opaque hollow tubing. A plurality of apertures are defined in the wall of the tubing and a lens barrel which extends beyond the opposite surfaces of the wall is supported within at least one of the apertures. A glass lens is mounted in the lens barrel. A housing is provided with a first channel for receiving the sample cell and a further series of channels extending from the exterior of the housing to the sample cell apertures. A filter element is housed in each of these latter channels. These channels also slidingly receive an excitation light source or a photodetector cell to permit selective focusing thereof. A sample cell containing at least three apertures in the walls thereof can be mounted for rotation relative to a light source or photodetection means for simultaneous or alternate optimetric determination of the components of a single sample. The sample cell is fabricated by supporting a lens barrel within the aperture. A molten portion of glass is deposited in the lens barrel and cooled while in a horizontal position to form a lens having an acceptable angle of 130* to 170* at an aperture of f7 or below.
TL;DR: The radius of Venus has been determined from radar-range data taken at the Jet Propulsion Laboratory's Goldstone facility from equations of motion of the solar-system fit to this time-delay data.
Abstract: Venus radius determination from ground based radar range data compared with Mariner 5 and Venera 4 observations and other radar measurements
TL;DR: In this paper, several extensions in quasilinearization techniques for optimal control problems are presented, and a method for extending the region over which the method converges is presented and the theoretical advantage of the extended method is shown.
Abstract: This paper presents several extensions in quasilinearization techniques for optimal control problems. Techniques are developed that facilitate the application of quasilinearization to control problems where bounds on the controls exist. Toward this end, quadratic convergence for bounded continuous control is shown. A method for extending the region over which the method converges is presented, and the theoretical advantage of the extended method is shown. The work of Long is modified to provide more accurate integration while preserving its usefulness in solving problems where the final time is free. A companion paper presents computational results.
TL;DR: Explicit expressions for stiffness matrix of triangular torus elements associated with linear displacement fields and generalized Hookian material are given in this article for linear displacement field and generalized hookian material.
Abstract: Explicit expressions for stiffness matrix of triangular torus elements associated with linear displacement fields and generalized Hookian material
TL;DR: High dispersion spectroscopic studies of Venus, discussing spectrograms of one micron carbon dioxide bands, rotational temperatures and reflecting model of atmosphere were discussed in this article.
TL;DR: Performance characteristics of single wavelength liquid metal MHD induction generator with end loss compensation, determining electrical losses and power production were discussed in this article, where the authors considered the case of a single wavelength MHD generator.
Abstract: Performance characteristics of single wavelength liquid metal MHD induction generator with end loss compensation, determining electrical losses and power production
TL;DR: In this article, the authors discuss the invariants of triangular shell element stiffness matrices associated with polyhedral deflection distribution, and discuss the effect of geometry on these matrices and their properties.
Abstract: Invariants of triangular shell element stiffness matrices associated with polyhedral deflection distribution, discussing effect of geometry
TL;DR: A simple algorithmic solution is developed for the discrete time, nonlinear, system identification problem based on a stochastic approximation method that is applicable to the noisy, as well as the noiseless, input-output measurement case.
Abstract: A simple algorithmic solution is developed for the discrete time, nonlinear, system identification problem based on a stochastic approximation method. The method is applicable to the noisy, as well as the noiseless, input-output measurement case. A minimal statistical knowledge of the noise and input sequences is required for this method; also, the algorithm is very easy to program. The proof of convergence for the algorithm is given along with some experimental results obtained from some control system input-output data.
TL;DR: In a companion paper as mentioned in this paper, several extensions in quasilinearization were presented for two problems: the brachistochrone problem and the reentry vehicle problem.
Abstract: In a companion paper (Ref. 1), several extensions in quasilinearization were presented. These results are studied computationally in this paper for two problems: the brachistochrone problem and the reentry vehicle problem. For the brachistochrone free-time problem, it is shown that much more rapid convergence is obtained than that presented in previous literature (Ref. 2). It is also shown that, if the techniques of the companion paper are used, the normal region of convergence is extended significantly. Similar results are obtained for the reentry vehicle problem.
01 Oct 1968
TL;DR: A survey of the theory and applications of the class of random processes is presented in this paper, which includes the law of large numbers, covariance estimation, and the relationship of linear to normal processes.
Abstract: A survey of the theory and applications of the class of random processes is presented. Topics discussed include the law of large numbers, covariance estimation, and the relationship of linear to normal processes. Various applications of the linear process to problems of communication theory are considered. These include prediction, signal extraction, and detection, using the linear process as a model for the signal or noise. Several exmples illustrating certain aspects of linear processes are given.
TL;DR: In this paper, a model probability distribution for the RF phase error was developed to predict the performance of phase-shifted keyed and differentially coherent communication systems, which is directly applicable to the Mariner and Pioneer-type communication systems.
Abstract: In phase-coherent communication systems, where bandpass limiters precede the radio frequency (RF) carrier tracking loop, it is of interest to understand how the noisy RF carrier reference effects system performance. This paper characterizes a model probability distribution for the RF phase error and uses this to predict the performance of phase-shifted keyed and differentially coherent systems. The theory developed is directly applicable to the Mariner- and Pioneer-type communication systems. For these systems two physical situations are considered: 1) system performance when the phase error is constant over the duration of one bit, and 2) system performance when the phase error is allowed to vary over the duration of one bit.
TL;DR: In this article, the authors used high-resolution TV images from Surveyor 1 spacecraft to study the properties of the target areas from high resolution TV pictures received by Surveyor 2.
Abstract: Photometric properties of lunar surface target areas from high resolution TV pictures received from Surveyor 1 spacecraft
TL;DR: In this paper, the breakdown potential of argon flow between flat parallel plate electrodes between flat plate electrodes has been studied in terms of dynamic gas velocity and pressure effects on breakdown potential.
Abstract: Dynamic gas velocity and pressure effects on breakdown potential of argon flow between flat parallel plate electrodes
TL;DR: Atmospheric gas composition effects on shock layer radiative heat transfer and heat shield response in Venus entry simulated by earth reentry were studied in this paper. But the results were limited to the case of Earth reentry.
Abstract: Atmospheric gas composition effects on shock layer radiative heat transfer and heat shield response in Venus entry simulated by earth reentry
TL;DR: The results of these missions vary from 1 m for the Lunar Orbiter to 1 2m for the impacting Ranger to millimeters for Luna-IX and the Surveyors as discussed by the authors.
Abstract: The lunar photography missions have included flyby, impacter, lander, and orbiter spacecrafts. These missions have provided photographs of the far side of the moon and a ten-fold increase in frontside resolution plus higher resolution of selected frontside areas. The resolutions which have been achieved vary from 1 m for the Lunar Orbiter to 1/2 m for the impacting Ranger to millimeters for Luna-IX and the Surveyors. The return from these missions have resolved much of the mystery surrounding the moon.
TL;DR: In this paper, the authors discuss the role of failure analysis in support of system development, indicate the relative proportion of part failures due to various major causes, and present several examples of failures.
Abstract: Failure analysis experience gained in support of several major spacecraft programs has shown the vast majority of electronic part failures encountered to be the result of relatively straightforward quality defects and misuse Within the framework of this experience, it is estimated that the number of part failures resulting from these simple causes is at least 100 percent greater than that due to more subtle time/environment dependent failure mechanisms Therefore, even first-order failure analysis without resort to sophisticated facilities and techniques can provide substantial information regarding the cause of equipment malfunction It is the intent of this paper to briefly discuss the role of part failure analysis in support of system development, indicate the relative proportion of part failures due to various major causes, and present several examples of failure analysis results
TL;DR: For tetrahedral molecules, this paper developed a quantum mechanical theory which relates the octopole moment to the integrated absorption of the collision-induced rotational spectrum, applied to recent far-infrared data on CH 4, CD 4 and CF 4.
01 Jan 1968
TL;DR: In this paper, the forebody shape effects on drogue drag were tested for various forebody-drogue configurations in supersonic flow in a single-person flight.
Abstract: Forebody shape effects on drogue drag tested for various forebody-drogue configurations in supersonic flow