The P120C is the largest solid-propellant rocket motor ever built in one segment. Each P120C will hold over 140 tonnes of propellant in a carbon fibre casing almost 11.5 m long and about 3.4 m in diameter. It is derived from Vega’s current first stage motor, the P80, which holds 88 tonnes of propellant.
The design builds on existing expertise and lessons learned with Vega’s P80, and it increases Vega performance with Vega-C. Two or four P120Cs will be strapped onto Ariane 6 as boosters for liftoff.
The use of this solid rocket on both the upgraded Vega-C and the larger Ariane 6 illustrates how the privately controlled ArianeGroup is trying to reduce costs. In the past, Arianespace would have had different companies within the ESA build different solid rockets for Vega-C and Ariane 6 in order to distribute the work to different member countries, even though having two different development contracts would have increased costs.