Europe’s Spaceport in French Guiana is preparing for the arrival of Ariane 6, ESA’s new heavy-lift rocket. This involves the final preparations of the new Ariane 6 launch complex and all the systems necessary for a launch.
On the launch pad, two ‘cryo-arms’ made and tested in France have been attached to the upper end of the mast. They are part of the fluidic connection system which connects to the Ariane 6 upper stage.
These ‘cryo arms’ support the upper umbilicals which supply the Ariane 6 upper stage with cryogenic top-up fuel, maintain the correct pressurisation of the upper stage tanks, cool the engines before ignition and generally keep the upper stage in an optimal condition right up to the point of liftoff. The same umbilicals allow the fuel to be drained safely if a launch is aborted.
Each arm is 13 m long and weighs 20 tonnes. One arm supplies liquid hydrogen at -250ºC, the other supplies liquid oxygen at -180ºC. When Ariane 6 lifts off, these arms will disconnect from the rocket and then pivot away quickly in just 2.6 seconds to avoid interfering with the rocket's ascent.
This manoeuvre requires great precision in order, almost simultaneously, to disconnect the arms, protect the supply hoses from gas ejections from the boosters and allow the launch vehicle to pass while avoiding any contact with it. A 50-tonne counterweight inside the mast – as heavy as a humpback whale – speeds up the retraction of the arms. A smart damping system allows the arms to brake before the end of their swing backwards in order to preserve the mechanical links with the mast.
Keeping the fluidic supplies connected with the rocket until the moment of liftoff guarantees the best availability and simplification of the interface with the launch vehicle.
The disconnect time for Ariane 6 is much faster than for Ariane 5, which is six seconds before liftoff. This means that the sequence for Ariane 6 can be triggered at the latest possible moment in the countdown reducing the chance of unnecessary disconnects on an aborted launch.
These articulated structures will now be tested with the mobile gantry fully retracted – as for a launch. They will repeat the tests performed in Fos-sur-Mer, France, but this time attached to the mast.