The Threat of Space Debris and Micrometeoroids to Spacecraft Operations

To date, there are roughly 9,000 catalogued
objects in orbit with a size larger
than 10 cm (Figure 1), of which only
about 600 are functioning satellites and
the remaining ca. 8,400 classified as
space debris. Most of the Space Debris
mass consists of non-functional satellites
and upper stages of launchers. The
majority of millimeter- and sub-millimeter-
sized debris particles were generated
through one of the ca. 170 explosions
that have been registered up to
now. Such explosions can be caused by
spontaneously triggered combustion of
residual amounts fuel in upper stages or
by overcharged batteries. The micronsized
debris particles mostly stem from
the combustion products of solid rocket
motor firings and fragments of varnish.
The encounter velocities between space
debris and spacecraft in low earth orbits
are in the range up to about 15 km/s,
which corresponds to head-on collisions.
Micrometeoroids can have much higher
impact velocities, depending on their
origin. Even tiny particles possess considerable
kinetic energies as a result of
the very high impact velocities.