Powder acceleration stage

The powder acceleration stage works with two solid fuel boosters, each one 30 metres tall with 237.8 metric tonnes of fuel.

The boosters are ignited on the launch pad once the Vulcain engine of the Main Cryogenic Stage has stabilised its thrust power.

The engines provide more than 90 percent of the total thrust of the launcher at the start of flight. Their fuel is spent in 130 seconds after which they are ejected and fall to a precise spot in the ocean.

The solid fuel booster is made up of three segments: the rear (lower) segment 11.1 metres long which is loaded with 106.7 metric tonnes of fuel; the central segment which is10.17 metres long and contains 107.4 metric tonnes of fuel; and the front (upper) segment, loaded with 23.4 metric tonnes of fuel.

The fuel used for the solid fuel boosters contains 68% of ammonium perchlorate (oxidiser), 18% of aluminium (fuel) and 14% of polybutadiene (binder).

The combustion process is triggered by a pyrotechnic device, and the solid fuel burns with a radial velocity of about 7.4 mm/sec (from the external central face).

The flight is controlled by the mobile engine nozzle which is controlled by hydraulic servo-controls.