The worrying scenario drawn as far back as 1978 by the then NASA consultant and researcher Dr. Donald J. Kessler has become reality and, as it is possible to note, the scenario took the same name of the researcher (i.e. The KESSLER EFFECT).

Today, the volume of space debris in “low orbit” around the Earth is becoming more and more unwieldy as the orbiting objects themselves collide with each other several times, creating a real “chain reaction” and thus increasing the volume of debris themselves with the risk of further impacts (the so-called Cascade Effect or Domino Effect).

The relative speed of the orbiting objects reaches as high as 16 km/s, while the kinetic energy generated by the collision of two objects with a larger mass creates a veritable cloud of debris that turns into crazy shrapnel thrown in random directions.

As can easily be guessed, each individual fragment therefore poses a threat because it can, with the impact of fragments already present, create more space debris, not to mention more collisions between space stations.

Avoidance manoeuvres

Close encounters in space between these objects are known in advance to physicists, scientists and aerospace engineers well in advance, which is why sufficient time is available to shift (modify), even slightly, the orbit of the ISS (International Space Station) or satellites; an evasive action known as a debris avoidance manoeuvre. (NOTE: consider that between 1999 and 2020, the ISS conducted no less than 29 avoidance manoeuvres).

Occasionally, however, the tracking data are not accurate enough to justify such a manoeuvre. Unfortunately, although rarely, the close passage cannot be identified in real time and thus there is not sufficient time to carry out such a manoeuvre. In such cases, then, the international control centres located on Earth may agree that the best course of preventive action to take is, for example, to transfer the crew to a Russian or a US spacecraft (spacecrafts are often used to transport astronauts and cargo to other space modules).

Debris avoidance manoeuvres essentially depend on guidelines that draw an imaginary box known as a “pizza box” because of its flat, rectangular shape, a box drawn around the spacecraft. This box is approximately 2.5 miles deep, 30 miles wide and 30 miles long (4 x 50 x 50 kilometres), with the spacecraft placed in the centre. When predictions indicate that an intercepted object will pass in the immediate vicinity to raise an alarm situation and the quality of the tracking data is deemed sufficiently accurate, the mission control centres in Houston and Moscow cooperate simultaneously to develop a prudent course of action.

Explore NASA’s interactive Space-Junk map showing the current situation.