Schematic of damage morphology for impacts into composites (after Dooling and Kinckenor, 1999). Row 9 was facing the ram direction (the leading edge), and row 3 was the trailing edge.ДЇig. 28.30 shows a polar plot of the number of impacts around the LDEF ( See et al., 1992). This is the case for the LDEF, which was in LEO for 69 months. For a spacecraft with a fixed orientation relative to the ram velocity direction, the combined occurrence of micrometeoroid and orbital debris impacts is nonuniform around the spacecraft. 28.29 was developed based on the CourвЂ“Palais model, ( Cour-Palais et al., 1969) and the Debris Flux model was developed based on the Kessler model ( Kessler et al., 1988). The Micrometeoroid Flux Model shown in Fig. The orbital debris size distribution can be seen in Fig. Shipman and Williamson (1997) Because of the manmade origin and atmospheric drag, orbital debris flux is highly dependent on the worldвЂ™s spacecraft launch frequency and occurrences of orbital breakups. Orbital debris has an average velocity of 8.7В km/sec. Orbital debris is manmade as a result of spent solid rocket booster exhaust, satellite breakups or other man-caused origins.

28.29, as micrometeoroid particle size decreases, the flux of particles increases. Their velocity is typically in the 4в€’51В km/sec range, ( Kinard and Martin, 1991 Zook, 1991) with an average velocity near 20В km/sec. Micrometeoroids are of extraterrestrial origin and, as such, will have a flux that is reasonably constant with time.

Micro meteoroid