Speaker
Description
The key to dealing with dust contamination lies in understanding its adhesive behaviour. It is currently unclear which of several adhesion forces (namely electrostatic and van der Waals forces) would dominate for the different particle sizes present on the Moon. The complex radiative environment under ultra-high vacuum as well as the high variation in shape, composition, and size of the particles makes it difficult to separate different contributions. This PhD research will use complimentary experimental techniques to investigate the adhesion of lunar dust simulant particles; centrifuge testing at Onera and AFM (atomic force microscope) testing at ESA/ESTEC. The use of different approaches allows us to overcome some of the limitations associated with on-earth testing. The objective is to obtain useful data and improve our understanding of the parameters determining adhesion behaviour.
Centrifuge testing is a method for measuring the adhesion behaviour of a large population of particles. This technique can be carried out in a vacuum chamber, thus affords some control over the environment. Centrifuge testing on space-relevant optical solar reflector (OSR) surfaces was carried out at under high vacuum both with and without vacuum ultra-violet illumination in order to compare adhesion values under different charging conditions. In order to measure the adhesion of the smallest particles AFM force-distance curves were obtained under N2 atmosphere, using individual LDS particles which were bonded to the cantilevers, in lieu of standard AFM tips. The surface roughness of each particle can be characterised using AFM topography measurements in order to provide context for the importance of van der Waals forces under these conditions. Methods of charging the particles in situ prior to measurement are also being investigated.
