Ariane 5 ES
|Main data||Ariane 5 ES|
|Height||up to 53 m|
|Diameter||up to 5.4 m|
|Liftoff mass||760 t|
|Payload mass*||more than 20 t|
* into ISS orbit
The Ariane 5 ES version is an evolution of the initial Ariane 5 generic launcher. With a more powerful lower composite, identical to the one used on Ariane 5 ECA, it reuses the small storable propellant stage (EPS: Etage à Propergols Stockables) of the generic version, which has been upgraded to allow reignition and long coast phases.
EPS reignition maximises the launcher's performance into the target orbit and meets a wider range of mission requirements.
These capabilities are necessary to deliver the Automated Transfer Vehicle** (ATV) into its rendezvous orbit with the International Space Station or to inject a cluster of four Galileo satellites into their operational orbit.
Reignition is also required to vacate the injection orbit after releasing the payload. This guarantees a controlled and safe deorbiting of the empty stage and an orbit free of major debris.
Ariane 5 ES missions
ESA's ATV is injected into a 260 km circular low orbit inclined at 51.6˚ to the Equator. From this orbit, the 20 t ATV uses its own engines to reach and dock with the International Space Station.
The maiden flight of the Ariane 5 ES took place on 9 March 2008 with the first ATV mission, Jules Verne. The second ATV, Johannes Kepler, was launched on 16 February 2011.
Three more ATV missions are planned: Edoardo Amaldi in 2012 and Albert Einstein in 2013, with ATV-5 to be scheduled.
For the ATV launch, the first EPS burn takes place immediately following the separation of the cryogenic main stage. The EPS engine is then shut down and the composite (VEB, EPS and ATV) begins a long coast of about 45 minutes. The second, short, EPS burn circularises the orbit, before ATV is released into its target orbit.
The third and last burn dispatches the almost-empty VEB–EPS composite to reenter the atmosphere, where it safely breaks up at high altitude.
Galileo satellites are injected at an altitude of 23 222 km in an orbit inclined at 56° to the Equator in three orbital planes. Ten satellites will be spread evenly around each plane. One satellite in each plane will be a spare, standing by should any operational satellite fail.
Four Galileo satellites, each about 730 kg, can be launched by Ariane 5 ES. An ATV-like launch sequence is followed by longer ballistic phases between the EPS reignitions.
Ariane 5 ES elements
Ariane 5 ES consists of three parts.
1. Lower composite (EAP and EPC)
The lower composite is identical to that used on Ariane 5 ECA and operates in the same way. It comprises two solid-propellant boosters (EAP: Etage d’Accélération à Poudre) and the cryogenic main stage (EPC: Etage Principal Cryotechnique) equipped with the Vulcain 2 engine.
2. Upper composite (EPS, VEB and supporting structure)
The upper composite comprises:
- The upper stage (EPS: Etage à propergols stockables) containing 10 t of storable propellants (MMH: monomethyl hydrazine and N204: nitrogen tetroxide), with the Aestus rocket engine providing 2.7 t of thrust;
- The Vehicle Equipment Bay (VEB), ‘the brain’, autonomously controls the whole vehicle;
- The supporting structure interfacing with the payload.
3. Launcher upper part (fairing and payload adaptor)
The launcher upper part comprises:
- The fairing, protecting the payload during the atmospheric flight;
- The dedicated structure accommodating the heavy payload or providing multiple satellite releases.
** The ATV supplies the ISS with pressurised cargo, water, air, nitrogen and oxygen, and attitude control propellant. It is also used to remove waste from the station and to re-boost the ISS to a higher altitude to compensate for atmospheric drag.