How did black powder make early military rockets possible?

Black powder made early military rockets possible by serving as a propulsive charge that generated the necessary thrust for flight. Composed of a mixture of charcoal, potassium nitrate (saltpetre), and sulfur, this mixture burns rapidly when ignited, producing a significant volume of gas.12

When contained within a tube, the expansion of these gases creates a propulsive jet that can launch a projectile. Early designs were often crude, utilizing tightly wrapped paper cases coated with shellac to hold the powder. By the late 18th century, engineers like Hyder Ali improved these weapons by using metal cylinders, which allowed for higher internal pressure and, consequently, greater thrust and range.134

Beyond providing propulsion, black powder also functioned as an incendiary agent against targets. Later refinements, such as those by Sir William Congreve, allowed for the use of black powder in explosive warheads, which could be timed to detonate in the air, further increasing the effectiveness of these early rocket and missile systems.14