What is the reason solid high power rocket motors use composite fuel instead of black powder?

Solid high power rocket motors utilize composite fuels primarily because they provide more total impulse compared to traditional black powder. Total impulse refers to the overall momentum produced by the rocket motor during its burn time, and composite propellants are designed to offer a more efficient and powerful combustion process.

Composite fuels consist of a mixture of a fuel and an oxidizer, which can be optimized for performance. This enables the generation of a higher thrust and a more sustained burn over a period, contributing to greater total impulse. This characteristic makes composite fuels more suitable for high power rocketry, as they allow rockets to achieve higher velocities and reach greater altitudes.

While factors like weight, burn temperature, and cost are also important considerations in rocket design and operation, the primary advantage of composite fuels in high power rocketry is indeed their ability to produce more total impulse, leading to improved performance in flight.