Exhaust Jet — Dust Layer Interaction During a Lunar Landing

Abstract

A'1though our present knowledge of the lunal: envirorunent is rather incomplete , it appears very likely that there exists on the moon a dust layer of limited depth. A spacecraft landing on such a surface would cause erosion and possibly alocal dust stonn, since the retrograde rockets would interact with the surface in the final phase of the descent. The paper defines a theoretical model to describe the erosion and subsequent transport of dust in the vicinity of the landing vehicle. Available experimental information is examined, and a more complete description of the exhaust jet-dust layer interaCtion is established. Particular attention is paid to three important phases of the problem: a) The gas dynamic s of the exhaust b) The mechanics of the surface erosion c) Visibility through the dust cloud It is shown that the Mach number and Reynolds number of the exhaust flow, together with certain dust parameters determine the character of the erosion. The shape of the crater caused by this erosion is calculated and shown to be in qualitative agreement with the expe rimental results. The extent of the dust cloud and visibility through the cloud are shown to depend on the size of the particles, the depth of the dust layer, and the location of the vehicle above the surface. Interaction veine d'~chappement-couche de poussi~re au cours d'un atterrissage sur la Lune. Bien que nos connaissances actuelles de l'en-vironnement lunaire soient assez incompl~tes, il est tr~s probable qu'une couche depoussi~re de profondeur limit~e ~xiste sur la Lune. Un astronef atterrissant sur une pareille surface, y provoquera l'~rosion et peut-~tre m~me une temp~te locale de poussi~re, puisque durant la phase finale de la d~scente il y aura interaction entre les fU8~es r~trogrades et la surface. La pr~sente communication dHinit un modHe th~orique pour d~crire I '~rosion et Ie transport de poussi~re qui s 'ensuit au voisinage du v~hi­ cule atterrissant. Les donn~es exp~rimentales disponibles sont ~xamin~es * AeroSpace EngIneer.