The Ariane 5 Rocket - 100 Launches!

Video from the channel Scott Manley about Ariane 5, linked on its Above Ten Thousand entry. Duration: 9:30. Language: English. Video type: Documentary.

An educational video recorded hours before Ariane 5's hundredth launch. It covers the rocket's design, its role in the geostationary satellite market, some incidents from its history and the failure of its maiden flight, in June 1996.

Ariane 1 to 4 used hypergolic propellants. Ariane 5 was a complete redesign, with a central stage powered by liquid hydrogen and oxygen through a Vulcain engine and two solid strap-on boosters. It was conceived in the early 1990s with crewed-flight qualification in mind, intended for the European Space Agency's Hermes spaceplane, a project that was later abandoned. The hypergolic upper stage of the early versions gave way to a cryogenic hydrogen one in the ECA version, though the hypergolic stage was kept to launch the European cargo vehicle to the space station. The author also mentions a recent launch in which an incorrectly entered azimuth left two satellites in an orbit inclined about 20 degrees, which they had to correct using their own propulsion.

The maiden flight carried the Cluster satellites. The inertial platform software, inherited from Ariane 4 and written in Ada, converted a 64-bit floating-point value, the horizontal bias, into a 16-bit integer. That function was only needed on the ground, but remained active for about 40 seconds after liftoff. Ariane 5, much faster, overflowed the integer and the main computer shut down. The backup suffered the same failure, and the rocket, with no guidance, had to be destroyed. Despite that start, Ariane 5 became established as a reliable launcher, able to place two satellites into geostationary orbit at once. The upgraded version of the Vulcain engine, with 40% more thrust, delivers around 1,390 kilonewtons. The video mentions its successor, Ariane 6, and the future launch of the James Webb telescope.