Ariane 5

Ariane 5 was designed from the outset to reduce launch costs and increase reliability compared to its predecessor, Ariane 4. The core stage, called the Étage Principal Cryotechnique (EPC), burns liquid hydrogen and liquid oxygen, fed by a single Vulcain engine. Two solid rocket boosters (SRBs), each producing about 7,000 kN of thrust, provide the majority of liftoff thrust. The upper stage, the Étage à Propergols Stockables (EPS), uses storable propellants for multiple restarts, enabling precise orbital insertions.

The vehicle's modular design allowed for two main configurations: the Ariane 5G (generic) and later the Ariane 5 ECA (Evolution Cryotechnique type A), which increased GTO capacity to 10 tonnes for single launches or 9.6 tonnes for dual launches. The ECA version introduced a new cryogenic upper stage (ESC-A) with an HM7B engine, derived from Ariane 4's third stage. Development began in 1988, with the first flight on 4 June 1996, which ended in failure due to a software error in the inertial reference system, leading to a self-destruct 37 seconds after liftoff.¹

After the initial failure, Ariane 5 underwent a rigorous redesign and returned to flight in October 1997. Over its operational life, it launched a wide range of payloads, including commercial telecommunications satellites, Earth observation spacecraft, and deep-space probes. Notable missions include the Rosetta comet chaser, the Herschel and Planck space observatories, and the James Webb Space Telescope, which launched on an Ariane 5 ECA in December 2021.²

The vehicle's dual-payload capability was a key commercial advantage, allowing Arianespace to offer competitive pricing. It also supported European institutional missions, such as the Galileo navigation satellites and the Automated Transfer Vehicle (ATV) resupply craft for the International Space Station. The final flight, VA261, took place on 5 July 2023, launching the Syracuse 4B and Heinrich Hertz satellites, marking the end of a 27-year career.

Ariane 5 experienced two failures in its 117 flights. The first, on flight 501 in 1996, was caused by an integer overflow in the inertial reference system's software, which was reused from Ariane 4 without adequate protection. The second, on flight 517 in December 2002, involved a malfunction in the Vulcain 2 engine's nozzle cooling system, leading to loss of thrust and the vehicle's destruction. Both incidents prompted extensive investigations and design changes, resulting in a perfect record from 2003 onward.³

The 2002 failure led to the development of the ECA variant, which first flew successfully in February 2005. The vehicle's reliability was further enhanced by a policy of strict quality control and conservative margins. Notably, Ariane 5 achieved 80 consecutive successful launches, a record for a heavy-lift vehicle, demonstrating its maturity and the effectiveness of European aerospace engineering.

Beyond its commercial role, Ariane 5 was used for several unique missions. It launched the ATV, a pressurized cargo module that docked with the International Space Station, requiring precise orbital insertion and rendezvous capabilities. It also deployed the European Space Agency's LISA Pathfinder, a technology demonstrator for gravitational wave detection, and the BepiColombo mission to Mercury, which required a complex interplanetary trajectory.

One obscure fact: the Ariane 5's solid rocket boosters are the largest ever used in a commercial launch vehicle, each containing 237 tonnes of propellant. The vehicle's launch site, the Guiana Space Centre in French Guiana, was chosen for its proximity to the equator, providing a rotational speed boost of about 460 m/s. Additionally, Ariane 5 was the first launch vehicle to use a fully digital flight control system, which contributed to its high accuracy but also introduced the software vulnerability that caused the 1996 failure.⁴

GTO

Geostationary transfer orbit, an elliptical orbit used to reach geostationary orbit.

EPC

Étage Principal Cryotechnique, the cryogenic main stage of Ariane 5.

SRB

Solid rocket booster, a large solid-propellant motor providing additional thrust at liftoff.

Vulcain

The main engine of Ariane 5's core stage, burning liquid hydrogen and oxygen.