ESA is gearing up to test on one of the largest solid rocket motors ever built this week. At the space agency's Spaceport in French Guiana, the first complete P120C rocket motor, which that will act as a booster for ESA's Vega-C and Ariane 6 rockets, will be mounted on a static test stand where 600 sensors will monitor the motor during its 135-second burn.

There have been previous solid rocket motors that were bigger than the P120C, but, where previous motors were made of welded or bolted sections, the new motor holds the record for the largest solid rocket made in one piece. Instead of metal, the casing of the P120C is made of a spun carbon composite and epoxy material, and is based on the previous P80 that included electromagnetic actuators for thrust vectoring.

The type of fuel used in the P120C has not been revealed, but if it is like similar rockets, the motor will be filled with a type of synthetic rubber compound mixed with an accelerant and a metal powder mix that acts as the oxidizer. The motor stands 13.5 m (44 ft) high and is 3.4 m (11 ft) wide and includes 142 tonnes of propellant providing 1,037,493 lb (4,615 kN) of thrust.

According to ESA, the main components have already undergone testing, including the nozzle, igniter, propellant, and motor case. This week's static fire test will determine how well the fully integrated motor operates and will provide information for future improvements that will be included in the P120C qualification motor, which will fire later this year.

When the P120C comes online, it will act as the first stage for the Vega-C launcher and as a strap-on booster for the Ariane 6 and larger configuration Vega-Cs.

Source: ESA