Resistance of motion to a small, hypervelocity sphere, sputtering through a gas

Abstract

Earlier work on the resistance acting on a small sphere moving through a gas is reviewed. A model for the resistance encountered by a sphere, the surface molecules of which are sputtered off during collisions with the gas molecules, is derived and compared with the case of specular reflection. The sputtering model is applied to the case of small 10-μm radius meteoroids entering the Earth's atmosphere. A possible link between the results obtained and the recent discovery of unheated, organic grains at an altitude of 40 km in the Earth's atmosphere is considered.