propellenti

Propellenti (propellants) are substances or mixtures used to produce thrust by expelling reaction mass. They are central to propulsion systems in aerospace, as well as in smaller-scale applications such as firearms. Selection depends on energy density, controllability, storage stability, and safety considerations.

In chemical propulsion, propellants are categorized as solid, liquid, or hybrid. Solid propellants consist of fuel and oxidizer bound in a single matrix, delivering high thrust with simple hardware but limited throttleability and no restart capability. Liquid propellants use separate fuel and oxidizer streams that are pumped into a combustion chamber, enabling throttling and restart. Hybrid systems combine a solid fuel with a liquid or gaseous oxidizer, offering intermediate performance and simpler handling than some liquids.

Electric propulsion relies on stored propellants that are ionized and accelerated by electric fields, providing high efficiency but low thrust. Common choices include xenon, krypton, or argon. Nuclear propulsion uses nuclear energy to heat or accelerate propellants, including nuclear thermal and nuclear electric concepts, which remain largely experimental for deep-space missions.

Performance is primarily described by specific impulse and thrust, as well as propellant mass, burn duration, and storage requirements. Safety and regulatory concerns address flammability, toxicity, chemical reactivity, and environmental impact, along with transport and handling protocols for materials used in ground and space facilities.

Historically, propellant development has driven rocket technology from black powder to modern formulations, with ongoing research into greener, safer, and more efficient propellants to meet evolving aerospace needs.