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Vedder, J. F.

Publications and source records attributed to Vedder, J. F..

46 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Some physical parameters of micrometeoroids

Detailed morphological parameters (depth/diameter ratio, circularity index) of microcraters in the 0.2 to 100 micron diameter range were obtained via SEM techniques for three lunar glass surfaces. The depth/diameter ratios are typically 0.5 to 0.8 with a range of 0.3 to 1.3. The circularity index varies from 0.4 to 1.0 with a pronounced maximum at 0.7 to 0.9. These parameters are compared with microcraters produced in the laboratory via electrostatic particle accelerators. The following conclusions are drawn: The great majority of observed crater depths are compatible with micrometeoroid densities of 2 to 4 g/cu cm; crater depths are incompatible for projectile densities less than 1 g/cu cm and greater than 7 g/cu cm. The circularity index of microcrater pits indicates rather equidimensional, if not spherical, projectiles. Needles, platelets and other highly irregular shapes can be excluded. Less than 5% of all craters observed may offer different conclusions.

Brownlee, D. E.↗
NASA NTRS1972

Craters formed in mineral dust by hypervelocity microparticles.

As a simulation of erosion processes on the lunar surface, impact craters were formed in dust targets by 2- to 5-micron-diameter polystyrene spheres with velocities between 2.5 and 12 km/sec. For weakly cohesive, thick targets of basalt dust with a maximum grain size comparable to the projectile diameter, the craters had an average projectile-to-diameter diameter ratio of 25, and the displaced mass was 3 orders of magnitude greater than the projectile mass. In a simulation of the effect of a dust covering on lunar rocks, a layer of cohesive, fine-grained basalt dust with a thickness nearly twice the projectile diameter protected a glass substrate from damage, but an area about 50 times the cross-sectional area of the projectile was cleared of all but a few grains. Impact damage was produced in glass under a thinner dust layer.

Vedder, J. F.↗
NASA NTRS1972

Accretionary processes in the early solar system - An experimental approach.

Results are given of an experiment to determine the range of silicate particle velocities over which accretion occurs. It was shown that micrometer-size silicate flakes do not accrete during impacts in the velocity range of 1.5 to 9.5 km/sec. Silicate accretion took place only between particles whose orbits were similar. Over at least part of the velocity range in which silicate accretion was efficient, metal particles would have rebounded without accreting. This suggests that if both metal and silicate were present during accretion, fractionation of one with respect to the other would have occurred.

Kerridge, J. F.↗
NASA NTRS1972

Profiling with the electron microscope.

Discussion of a profiling technique using a scanning electron microscope for obtaining depth information on a single micrograph of a small specimen. A stationary electron beam is used to form a series of contamination spots in a line across the specimen. Micrographs obtained by this technique are useful as a means of projection and display where stereo viewers are not practical.

Vedder, J. F.↗
NASA NTRS1972

An experimental approach to circumsolar accretion.

Experimental investigation of planetesimal accretion from grains in intersecting orbits. The study is aimed particularly at the velocity impact behavior of silicates, which comprise the major fraction of condensable material in the solar system.

Kerridge, J. F.↗
NASA NTRS1971

Microcraters formed in glass by low density projectiles

Microcraters were produced in soda-lime glass by the impact of low density projectiles of polystyrene with masses between 0.7 and 62 picograms and velocities between 2 and 14 kilometers per second. The morphology of the craters depends on the velocity and angle of incidence of the projectiles. The transitions in morphology of the craters formed by polystyrene spheres occur at higher velocities than they do for more dense projectiles. For oblique impact, the craters are elongated and shallow with the spallation threshold occuring at higher velocity. For normal incidence, the total displaced mass of the target material per unit of projectile kinetic energy increases slowly with the energy.

Mandeville, J.-C.↗
NASA NTRS1971

Microcraters in glass and minerals

Microcrater morphology in lunar soil glass, oligoclase and olivine, determining projectile velocity, impact angle and shape effects

Vedder, J. F.↗
NASA NTRS1971

Microcraters formed in glass by low density projectiles

Microcraters were produced in soda-lime glass by the impact of low density projectiles of polystyrene (p = 1.06 g/cu cm) with masses between 0.7 and 62 picograms and velocities between 2 and 14 km/s. The morphology of the craters depended on the velocity and the angle of incidence of the projectiles and these are discussed in detail. It was found that the transitions in morphology of the craters formed by polystyrene spheres occurred at higher velocities than they did for more dense projectiles.

Mandeville, J.-C.↗
NASA NTRS1965

Micrometeoroids.

Size, distribution, velocities, penetration and densities of meteoroids and micrometeoroids, noting sounding rocket data

MICROMETEOROID↗