An ablation model is described that can be used to estimate the effect on a large meteoroid of passage through a planetary atmosphere. The effect on ablation and deceleration of breakup due to aerodynamic pressure is investigated. Results from arc‐jet wind‐tunnel tests and strength measurements of meteorite samples have been used to help determine the material properties needed in the calculations. Results are given from a series of calculations of the ablation and breakup of bronzite and carbonaceous chondrite meteoroids in the earth's atmosphere. It is shown that evidence from meteor observations and meteorite falls can be interpreted in terms of a preponderance in space of meteoroids of density comparable to that of meteorites rather than low density. Carbonaceous chondrite is a likely candidate as the most common type of meteoroid in space.

A finite-difference machine code is brought to bear on the wake-vortex problem in the quasi-cylindrical boundary-layer approximation. A turbulent-energy model containing new features is developed that accounts for the major effects disclosed by more advanced models in which the parameters are not yet established.Several puzzles are resolved that arose in previous theoretical investigations of wake vortices.

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