Ariane 5 is equipped with two Main Boosters that provide 90% of the thrust needed for takeoff. After burnout, about 2 minutes from launch, the Main Boosters have to be separated from the Space Vehicle. The remaining stages will continue acceleration for another 10 minutes in order to reach sufficient velocity for leaving the atmosphere and bringing the payload into orbit.
The French company Astrium Space Transportation is Prime Contractor for Ariane 5, and Nammo is supplier of Separation Boosters (FE), Acceleration Boosters (FA) and Safe & Arm Mechanisms (BSA).
For each launch of Ariane 5, a total of 16 Separation Boosters are used to safely release the two Main Boosters. At this stage Ariane 5 has already reached an altitude of 70 km in its trajectory.
For some configurations of Ariane 5, a total of 4 Acceleration Boosters are used in addition to provide extra thrust for the second stage to increase payload capacity. Several BSA's are also installed for each Launch Vehicle to arm the propulsion systems and various pyrotechnical devices on board.