Ariane 5 utilizes two solid boosters, each standing more than 30 meters tall with 237.8 metric tons of propellant. The boosters are ignited on the launch pad once the main cryogenic stage’s Vulcain engine has stabilized its thrust output. They deliver more than 90 percent of the launcher’s total thrust at the start of flight and burn for 130 sec. before they are separated over a designated zone of the Atlantic Ocean.
The booster stage’s solid rocket motor is made up of three segments: the 11.1-meter-long aft (lower) segment, which is loaded with 106.7 metric tons of propellant; the center segment, with a length of 10.17 meters and 107.4 metric tons of propellant; and the 3.5-meter-long forward (upper) segment, loaded with 23.4 metric tons of propellant.
A propellant mix of 68 percent ammonium perchlorate (oxidizer), 18 percent aluminum (fuel), and 14 percent polybutadiene (binder) is used in the solid rocket motors. The combustion process is initiated by a pyrotechnic device, and the solid propellant burns at a radial velocity (from the center outward) of approximately 7.4 mm/sec. Flight control is provided by the boosters’ movable nozzle, which is driven by hydraulically-controlled servoactuators.