FIGURE 4-8 Average time spent in LEO for GTO, inclination 27.5 degrees.

Random choice for initial argument of perigee and right ascension of ascending node of orbit plane. SOURCE: National Aeronautics and Space Administration.

The damage caused by debris impact depends on the size and velocity of the impacting debris, the configuration and composition of the spacecraft being struck, the component(s) impacted, and the angle at which the impactor strikes the spacecraft. To protect their spacecraft against the debris hazard, designers can calculate typical collision velocities and impact angles and then, if necessary, modify their spacecraft design to protect the areas most likely to be struck by debris. While not perfect, analyses of typical collision velocities and impact angles are based on the known debris population, so they have less uncertainty than many of the other elements factored into debris hazard predictions.

Collision velocities vary with orbital altitude and inclination (see Box 4-2). In LEO, collision velocities vary from almost 0 km/s to greater than 15 km/s. Figure 4-9 shows the calculated proportion of collisions (with cataloged objects) at various velocities as a function of a LEO object's