Ariane 5 is a launcher composed of a single-stage central body equipped with two solid fuel boosters and an upper stage.
This architecture, designed around a cryotechnical main stage (EPC), combines simplicity and robustness with a limited number of propulsion components, while offering wide possibilities for evolution, especially for the upper parts.
The Vulcain engine
The Vulcain engine is the propulsive unit of the cryotechnical stage. It delivers up to 116 tonnes of thrust in a vacuum. It is fired 7 seconds before takeoff to to control climb and power stabilisation perfectly.
The solid boosters (EAP)
The two solid boosters have to lift the launcher's 725 tonnes off the launchpad with an acceleration of 0.5 G on takeoff.
The boosters are 30 m tall and are each filled with 237 tonnes of solid fuel. They deliver a combined thrust of 1370 tonnes at takeoff, more than 90% of the total thrust of the launcher at that moment.
They run for 130 seconds with an average thrust of 1000 tonnes before being ejected at an altitude of 70 km. They fall into a controlled area of the Atlantic Ocean and are, if necessary, retrieved for inspection.
Main storable propellant stage (EPS)
The EPS is the upper stage that sends the payload of Ariane 5 towards its final orbit and provides precise injection into the orbit. To do this it carries 9.7 tonnes of storable propellant for its Aestus engine with 3 tonnes of thrust, fed simply by pressurising the tanks.
Captions for the illustration
1. Payload fairing
2. Payload adapters
3. Speltra and Sylda 5
4 (dual satellite support structures). Equipment bay
5. Upper storable propellant stage
6. Main cryogenic stage
7. Solid fuel engine
8. Solid fuel boosters
9. Vulcain propulsion system