Which motor type is characterized by a thrust curve that increases over time?

A progressive burn motor is characterized by a thrust curve that increases over time, meaning that the motor produces more thrust as it burns. This design allows for a gradual increase in propulsion, which can benefit flights by enhancing altitude and velocity during the initial phases of ascent. The progressive burn often involves a fuel grain configuration that provides a larger surface area as the propellant burns, resulting in a higher thrust output as the motor operates.

This type of motor is particularly advantageous in rocketry, as the initial thrust is lower to permit controlled liftoff before gaining more power for ascent, minimizing risks of structural failure or instability. This characteristic makes progressive burn motors suitable for higher-performance rockets where precise thrust management is essential.

In contrast, constant burn motors maintain a steady thrust output throughout their burn time, hybrid burn motors use a combination of solid and liquid propellant technology, and regressive burn motors typically have thrust that decreases over time, which is not conducive to maximizing early flight performance.