Engineering topics

Larson, S. A.

Publications and source records attributed to Larson, S. A..

4 records

NASA NTRS1993

Proprocessing: Geocoding of AVIRIS Data Using Navigation, Engineering, DEM, and Radar Tracking System Data

Remotely sensed data have geometric characteristics and representation which depend on the type of the acquisition system used. To correlate such data over large regions with other real world representation lools like conventional maps or Geographic Information Systems (GIS) for verification purposes, or for further treatment within different data sets, a coregistration has to be performed.

topography stability of the platform sensor flight↗

NASA NTRS1981

Multi-ring basin formation - Possible clues from impact cratering calculations

Finite difference continuum mechanics code calculations make it possible to vary the controlling variables in an impact event and to determine basic trends at scales unavailable to experimental analysis. Orphal et al. (1980) have summarized the results of a pair of such calculations for identical projectile/target characteristics but different impact velocities. One calculation considered a relatively low velocity iron impactor (5 km/s); the other, a high velocity iron impactor (15.8 km/s). The primary purpose was to investigate the generation and transport of impact melt for the two impact energies. Attention is given to crater growth, crater ejecta, and possible implications for basin-size events. Based on extrapolations, a new scenario is proposed. The scenario incorporates elements of several existing basin models.

Schultz, P. H.↗

NASA NTRS1981

Z-model analysis of impact cratering - An overview

The Maxwell Z-Model has been applied to two continuum mechanics computer calculations: (1) a laboratory-scale impact of an aluminum projectile into plasticene clay, and (2) a planetary-scale impact of an iron meteor into gabbroic anorthosite. The material flow in the cratering flow field may be well approximated by incompressible flow for most of the excavation stage of crater growth. The center of the flow field is located beneath, not at, the surface. Soon after energy partitioning is complete, Z can assume values less than 2.0 associated with the initial directedness of the projectile's momentum. The Z-Model parameters are time dependent during a significant portion of the crater growth time, and Z increases steadily with time from about 2.0 or slightly less at the beginning of the excavation stage to level off at values in the neighborhood of about 3.0 before the excavation stage is half-over.

Austin, M. G.↗

NASA NTRS1980

Impact melt generation and transport

The results from the first two calculations in a series of continuum mechanics computer code calculations, investigating the effects of variations in impactor mass and velocity on the generation and transport of impact melt, are reported. In the present calculations, the impactor is modeled as a spherical iron projectile with a mass of one trillion grams, and the target as a gabbroic anorthosite (GA) half-space, where the cases calculated have impact velocities of 5 and 15.8 km/sec. Early-time ejection velocities are 1-2 km/sec in both cases. The first calculation results in 0.07 projectile masses of GA being partly or completely melted, with all the melted GA being ejected from the crater, and a maximum impact range for the ejected melted material of 30 km. The second calculation yields 10.4 projectile masses of melted GA, 50% of which is ejected from the crater to ranges of up to about 130 km. Peak shock pressure attenuation with depth is reported for both cases, and transient cavity dynamics are described and compared to that for surface and near-surface explosions.

Orphal, D. L.↗