Managing Ariane debris

At the moment, every launch operator from the Guianese Space Centre is authorised to create a single item of debris for each payload injected into orbit (final stage plus the adaptor in the case of multiple payloads), while the threshold is reduced to zero for the satellite operator: the only debris is the satellite itself at the end of its life. The designer has to develop an intelligent architecture that will satisfy this requirement and attenuate the possible impact, for example by locating fragile equipment behind other less delicate elements or by reinforcing them with Kevlar or similar materials.

Since a country can be held responsible for any damage caused by a Space object launched from one of its bases, France, as a launch country, has made CNES/CSG responsible for monitoring the risk of fall-back by launcher stages while CNES Toulouse tracks the movements of 15 satellites to avoid any risk of collision.

CNES/CSG is responsible for the safety of persons and property at CSG and in Kourou, where it applies a particularly strict doctrine and range safety rules, for the tightest possible management of the fall-back of stages and other launcher parts, in the same way that it deals with potential toxicity hazards. These rules also serve as the basis for drafting the decrees and orders corresponding to the Space Act that was passed in June 2008.

Stage fall-back policy at Europe’s Spaceport

Each launch first requires a mission analysis. The CNES/CSG Range Safety Department ensures that all stages will be able to fall back into the sea, whichever launcher is used. The operator is required to provide all the information necessary for determining fall-back dynamics. The Department is then required to inform the maritime and air authorities about which region could be at risk from fall-back for each specific mission. Air traffic controllers then keep aircraft clear of the region concerned, but maritime traffic is left to the discretion of the captain of each vessel.

For an Ariane 5-type mission to a geostationary orbit, the launch vehicle will be jettisoning its boosters, its fairing and the Main Cryogenic Stage (EPC). Only the final or Storable Propellant Stage (EPS), the Upper Cryogenic Stage, version A (ESCA) and the payload adaptors (the SYLDA units) remain in the geostationary transfer orbit. The EPS or ESCA is ‘passivated’, meaning that the valves are opened to purge any remaining propellant from the tanks, so that they cannot explode.

This measure, which is now an integral part of the Ariane 5 launch procedure, is a consequence of the accident suffered by the Cerise satellite that was damaged by fragments from an Ariane propellant tank that had exploded earlier.

Same procedure for Soyuz and Vega

As with Ariane 5, Vega stages will follow exactly the same passivation procedure before falling back into the sea. For Soyuz, the Russians have added valves to their 4 boosters. Should it prove necessary to neutralise the vehicle, the passivation system would open the valves to purge the maximum possible quantity of propellant so that seawater can flow in and sink the structure.

When debris from CSG fall back to Earth

The first object was a piece of the fairing of V35 that turned up in Barbados. Other objects were found in Martinique, Guiana and Trinidad. On the beach at Kourou, it was part of a panel for sound-proofing the fairing. The fairing is made of light materials that do not sink, and although it is unlikely to cause any danger to shipping it drifts with the currents. Although all possible measures are taken to ensure that debris falls into the sea, Space activities at Kourou have frequently caused some surprises. Whenever an element from an Ariane 5 washes up on the coast of French Guiana, CNES/CSG does everything possible to recover it, particularly to eliminate any danger. The primary task is to make sure that the element offers no threat of explosion. CNES/CSG usually requests the help of the armed forces to recover or remove the part. With the exception of special campaigns to recover Ariane 5 boosters every two or three years for evaluation purposes, the heavy elements that inevitably sink are transformed little by little into artificial reefs by the marine environment.