P120 (rocket stage)

The P120C is a solid-fuel rocket motor designed for use as the first stage of the Vega-C and as the boosters of the Ariane 6 launch vehicles. The solid rocket motors were developed by Europropulsion, a joint venture of Avio and ArianeGroup, for the European Space Agency. The "C" in the name signifies its "Common" use across these vehicles.

As of July 2022, it holds the title of the world's largest and most-powerful single-piece solid-fuel rocket motor, surpassing its predecessor, the P80.

Development and Testing
Initially, production of the P120C was planned to be divided between Avio's main facility in Italy and MT Aerospace in Germany. However, in 2018, ESA decided to consolidate production entirely in Italy, with MT Aerospace focusing on Ariane 6's turbopumps.

The first successful test firing occurred at the Guiana Space Centre in July 2018, lasting 140 seconds and simulating a complete first-stage burn. Subsequent tests in 2019 and 2020 confirmed the motor's flight readiness for both launcher configurations.

Design and Performance
The P120C builds upon the P80's design, utilizing a carbon fibre casing constructed via filament winding and fabric deposition techniques. It houses a 143.6 t of HTPB 1912 propellant, a blend of 19% aluminium powder, 69% ammonium perchlorate with 12% of hydroxyl terminated polybutadiene binder. The motor's 25 cm thick walls require a 3500 km of carbon fiber, wound over 33 days in a climate-controlled environment. When operational, the P120C generates an average thrust of 4.5 MN.

P120C+
In 2022, development began on the P120C+ variant. This extended version adds 1 m to the motor's length and an additional 14 t of propellant. This upgrade translates to a roughly 2 t improvement in lift performance on the Ariane 64 with four boosters. Notably, 16 of the planned 18 Kuiper launches by Ariane 6 will utilize this enhanced booster.