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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Mariner 9 television observations of Phobos and Deimos.

Mariner 9 photographs of Phobos and Deimos have yielded new information about the orbits, rotation periods, sizes, shapes, and surface characteristics of the satellites. Both satellites appear to be in synchronous rotation. They are irregular, heavily cratered bodies whose shapes appear to have been determined largely by impact fragmentation and spalling. The surfaces of both satellites have crater densities close to saturation and nearly identical, very low albedos. Lower limits on the tensile and yield strengths are estimated, and it is concluded that both satellites may consist of well-consolidated, though possibly highly fractured material.

Pollack, J. B.↗
NASA NTRS1973

Moon - 'Ghost' craters formed during Mare filling.

This paper discusses formation of 'pathological' cases of crater morphology due to interaction of craters with molten lavas. Terrestrial observations of such a process are discussed. In lunar maria, a number of small impact craters (D less than 10 km) may have been covered by thin layers of fluid lavas, or formed in molten lava. Some specific lunar examples are discussed, including unusual shallow rings resembling experimental craters deformed by isostatic filling.

Cruikshank, D. P.↗
NASA NTRS1973

Mariner 9 television observations of Phobos and Deimos. II.

Analyses of the Mariner 9 pictures of the Martian satellites have yielded much new information: improved ephemerides, estimates of their principal axes, information about the texture of their surfaces, and estimates of the structural strength of their interiors. Both satellites are found to be in synchronous rotation, as was expected from tidal theory. A close examination of the preorbital satellite pictures has failed to show any unknown satellite. The photometric behavior of Phobos and Deimos indicates that they have intricate surface layers consistent with the presence of a regolith. Morphological features on Phobos and the expected collisional history of both satellites imply that both are made of well-consolidated material.

Pollack, J. B.↗
NASA NTRS1973

Martian surface and crust - Review and synthesis.

The nature of the classical marking of Mars are studied on the basis of Mariner 9 data and some earlier data. The analysis leads to a model of the Martian crust. Evidence for petrologic distinctions between surface materials in dark and light regions is obtained. It is shown that the classical markings are a complex result of three factors: (1) availability of two types of rock material transportable by wind, (2) topographic control of deposition, and (3) prevailing winds producing quasi-permanent preferential deposition patterns. The crust, especially in the Tharsis region, bears strong evidence of mantle-induced uplift of a type existing on earth. Such uplifts have obliterated ancient craters, caused fractures and graben systems, and have resulted in intense volcanism.

Hartmann, W. K.↗
NASA NTRS1973

Skylab SO71/SO72 circadian periodicity experiment

The circadian rhythm hardware activities from 1965 through 1973 are considered. A brief history of the programs leading to the development of the combined Skylab SO71/SO72 Circadian Periodicity Experiment (CPE) is given. SO71 is the Skylab experiment number designating the pocket mouse circadian experiment, and SO72 designates the vinegar gnat circadian experiment. Final design modifications and checkout of the CPE, integration testing with the Apollo service module CSM 117 and the launch preparation and support tasks at Kennedy Space Center are reported.

Fairchild, M. K.↗
NASA NTRS1974

Pioneer Mars 1979 mission options

A preliminary investigation of lower cost Mars missions which perform useful exploration objectives after the Viking/75 mission was conducted. As a study guideline, it was assumed that significant cost savings would be realized by utilizing Pioneer hardware currently being developed for a pair of 1978 Venus missions. This in turn led to the additional constraint of a 1979 launch with the Atlas/Centaur launch vehicle which has been designated for the Pioneer Venus missions. Two concepts, using an orbiter bus platform, were identified which have both good science potential and mission simplicity indicative of lower cost. These are: (1) an aeronomy/geology orbiter, and (2) a remote sensing orbiter with a number of deployable surface penetrometers.

Friedlander, A. L.↗
NASA NTRS1974

Mars - Clearing of the 1971 dust storm

A semiquantitative analysis of clearing in the 1971 great dust storm on Mars is presented as a function of time and altitude, using Mariner 9 orange- and visual-light photos. Steady settling of dust approximately accounts for the decline of the storm after Dec. 22, 1971. Continuous settling cannot be invoked prior to that date; injection of dust into the atmosphere, i.e., a storm resurgence, occurred in mid-December 1971. Theoretical models of optical depth vs time are developed for various distributions of particles in the atmosphere. By interpreting settling in terms of Stokes' law, estimates of the maximum radii of dust particles throughout the atmosphere have been obtained. Models which best account for the dust-storm decline indicate particles less than 5 microns in diameter high in the atmosphere, with a concentration of larger particles near the ground in the lowest parts of Mars.

Hartmann, W. K.↗
NASA NTRS1974

Research Investigation Directed Toward Extending the Useful Range of the Electromagnetic Spectrum

The report discusses completed and proposed research in atomic and molecular physics conducted at the Columbia Radiation Laboratory from July 1972 to June 1973. Central topics described include the atomic spectra and electronic structure of alkali metals and helium, molecular microwave spectroscopy, the resonance physics of photon echoes in some solid state systems (including Raman echoes, superradiance, and two photon absorption), and liquid helium superfluidity.

Hartmann, S. R.↗
NASA NTRS1974

The new Mars: The discoveries of Mariner 9

The Mariner 9 encounter with Mars is extensively documented with photographs taken by the satellite's onboard cameras, and an attempt is made to explain the observed Martian topography in terms of what is known about the geomorphological evolution of the earth. Early conceptions about the Mars surface are compared with more recent data made available by the Mariner 9 cameras. Other features of the planet Mars which are specifically discussed include the volcanic regions, the surface channels, the polar caps and layered terrain, the Martian atmosphere, and the planet's two moons--Phobos and Deimos.

Hartmann, W. K.↗
NASA NTRS1975

The effect of circumferential distortion on fan performance at two levels of blade loading

Single stage fans designed for two levels of pressure ratio or blade loading were subjected to screen-induced circumferential distortions of 90-degree extent. Both fan rotors were designed for a blade tip speed of 425 m/sec, blade solidity of 1.3 and a hub-to-tip radius ratio of 0.5. Circumferential measurements of total pressure, temperature, static pressure, and flow angle were obtained at the hub, mean and tip radii at five axial stations. Rotor loading level did not appear to have a significant influence on rotor response to distorted flow. Losses in overall pressure ratio due to distortion were most severe in the stator hub region of the more highly loaded stage. At the near stall operating condition tip and hub regions of (either) rotor demonstrated different response characteristics to the distorted flow. No effect of loading was apparent on interactions between rotor and upstream distorted flow fields.

Hartmann, M. J.↗
NASA NTRS1974

Transition radiation from relativistic electrons in periodic radiators

The generation and detection of transition radiation have been studied in a series of experiments with electrons from 1 to 15 GeV at SLAC and at the Cornell Synchrotron. Periodic radiators, consisting of thin plastic foils stretched in air at constant spacings, were used, and proportional chambers filled with krypton or xenon served as detectors. A detailed discussion of the theoretical predictions is given, and the measurements are systematically compared with the predictions by varying the most critical parameters, such as configuration of radiators and detectors, and energy of the electrons. In general, good agreement between theory and experiment has been found. On the basis of these results, the criteria are summarized under which transition radiation can readily be observed.

Cherry, M. L.↗
NASA NTRS1975

The generation of transition radiation by relativistic particles in plastic foam radiators

The design of large area transition radiation detectors for highly relativistic particles can be greatly simplified if plastic foam radiators are employed. Using electron beams with energies 1-9 GeV at the Cornell synchrotron, we have studied the properties of a large variety of transition radiators consisting of commercially available foam materials. In most cases, a measurable transition radiation signal has been observed, but only a few materials have been found to be suitable for practical purposes. The observed radiation yield is in these cases very similar to that of equivalent multifoil radiators. A detailed discussion is given of the particle detection efficiency that can be obtained with high yield foam radiators.

Prince, T. A.↗
NASA NTRS1975

Satellite-sized planetesimals and lunar origin

Exploratory calculations using accretionary theory are made to demonstrate plausible sizes of second-largest, third-largest, etc., bodies at the close of planet formation in heliocentric orbits near the planets, assuming asteroid-like size distributions at the start of the calculation. Many satellite-sized bodies are found to be available for capture, cratering, or collisional fragmentation. In the case of earth-sized planets, the models suggest second-largest bodies of 500 to 3000 km radius, and tens of bodies larger than 100 km radius. Many of these interact with the planet before suffering any fragmentation events with each other. Collision of a large body with earth could eject iron-deficient crust and upper mantle material, forming a cloud of refractory, volatile-poor dust that could form the moon. Other satellite systems may have been affected by major capture or collision events of chance character.

Hartmann, W. K.↗
NASA NTRS1975

Mars - Satellite origin and angular momentum

The origin of Phobos and Deimos is considered with a view to accounting for the existence of very small satellites with circular orbits in the Martian equatorial plane, and simultaneously for the suspected angular momentum deficiency of the Mars system. All models considered failed to satisfy at least one requirement, and the problem is considered more puzzling than is at first apparent. The Martian angular momentum deficiency, if physically significant, may be unrelated to the present satellites' origin, but might relate to a large ancient satellite, long ago destroyed. Accretion onto Mars of large amounts of asteroidal dust brought in by Poynting-Robertson drag may have some bearing on the angular momentum problem.

Hartmann, W. K.↗