Conventional and hybrid propulsion systems

The performance of propulsion techniques used to accelerate projectiles is discussed including the conventional solid propellant gun, liquid propellant gun, hybrid systems, ram accelerator, and the electric gun. In particular, the limitations encountered in chemically driven devices are described which, in general, depend upon the temperature, molar mass, and degree of freedom of the reaction species formed during the combustion of the propellant. Existing chemical propulsion devices including both the fielded and experimental guns propel a projectile within a range of several hundreth m/s to a maximum launch velocity which has recently been extended to 3650 m/s. In order to approach the chemical propulsion, novel concepts for propelling projectiles are currently being investigated. Such concepts are the electrical propulsion techniques including the hybrid combinations; that is the electrothermal-chemical (ETC) gun, the powder or solid propellant/electrothermal (PET or SPETC) gun, an d the liquid propellant/electrothermal (LET or LPETC) gun as well as the ram accelerator. Both the electromagnetic acceleration and the hybrid systems signify a real progress in propulsion technology. The hybrid systems bridge the gap that exists between the enormous weight and size of the present electrical power supplies and the desired high density electrical energy storage of future systems.