Title of Presentation: Contamination Transport from Spacecraft due to Winds

Primary (Corresponding) Author: Parthasarathy Shakkottai

Organization of Primary Author: NASA Jet Propulsion Laboratory

Co-Authors: Julian Bunn

Abstract: Particle transport from spacecraft surfaces to the ground due to Martian winds is of interest in estimating contamination levels. There are two aspects to the problem. First we have to find how particles detach from surfaces in a given wind and next determine particle trajectories and the final landing point.

Particle detachment from surfaces occurs when the moment due to particle drag in the wall shear region overcomes the restraining moment due to adhesion and gravitational forces. Available experimental data are compared with theoretical expressions of adhesion moment based on areas of contact of smooth, rough, elastic and plastic deformations. It turns out that smooth elastic contact is best supported by experimental data.

Rules for determining local winds on a bluff body are given based on locating stagnation points and attached flow regions.

The last step is to solve for trajectories given an initial particle distribution which is distributed at random on various surfaces and allowed to be dislodged by a wind distribution. An example will be shown of result from the Contamination Transport Program developed in Java which takes as input a vrml file of a lander and a cleanliness level and calculates particle trajectories and distributions on the ground.