Concrete recommendations
Ariane orbiting a satellite. Credits: CNES/ill.D.DUCROS,1998
Recommended solutions approved at international level fall into 3 main categories: “keeping space clean”, “eliminating explosive devices” and “protecting vital orbital regions”.
Rule n° 1: reduce the potential for creating too much debris.
Up to around the 1980's, space missions always used all sorts of pyrotechnic cables, bolts, covers and similar structures.
This type of orbital pollution has become the n° 1 target: today, on Ariane for example, separation systems are self-contained, cables are caught and the ejection of secondary structures is forbidden unless absolutely necessary.
Space debris after Ariane's 3rd stage explosion in 1986. A few months later, the debris almost covered Earth over hundreds of km of altitude.
Up to the start of 2009, 200 launcher stages and satellites have exploded in orbit.
Stages and satellites are still discarded too often without taking any precautions, even though they contain propellants or pressurized tanks.
Over time, they begin to heat up and their thermal protection systems gradually deteriorate, which can eventually trigger an explosion.
Hence, rule n° 2: systematically “passivate” anything left in orbit, that is, remove all stored energy on board.
In practical terms, this means venting residual propellant, relieving pressure vessels and discharging batteries.
Ariane 5 was the 1st launcher in the world designed from the outset to meet passivation requirements, despite their complexity.
Regions to protect. Credits: CNES
The LEO1 region is the spherical “shell” extending from the surface of Earth to 2,000 km, where most debris is found at this time.
These 2 regions must be protected by limiting the presence of orbiting objects in LEO to a maximum of 25 years after the end of their mission. Beyond that date, objects in LEO will have to be deorbited. Objects in GEO must be boosted at the end of their operating life into a graveyard orbit 200 km above GEO.
1 LEO: Low Earth Orbit
2 GEO: Geostationary Earth Orbit
