Editing Solid-propellant rocket (section)

===Minimum-signature (''smokeless'') propellants===
One of the most active areas of solid propellant research is the development of high-energy, minimum-signature propellant using C<sub>6</sub>H<sub>6</sub>N<sub>6</sub>(NO<sub>2</sub>)<sub>6</sub> [[Hexanitrohexaazaisowurtzitane|CL-20 nitroamine]] ([[Naval Air Weapons Station China Lake|China Lake]] compound #20), which has 14% higher energy per mass and 20% higher energy density than HMX. The new propellant has been successfully developed and tested in tactical rocket motors. The propellant is non-polluting: acid-free, solid particulates-free, and lead-free. It is also smokeless and has only a faint shock diamond pattern that is visible in the otherwise transparent exhaust. Without the bright flame and dense smoke trail produced by the burning of aluminized propellants, these smokeless propellants all but eliminate the risk of giving away the positions from which the missiles are fired. The new CL-20 propellant is shock-insensitive (hazard class 1.3) as opposed to current HMX smokeless propellants which are highly detonable (hazard class 1.1). CL-20 is considered a major breakthrough in solid rocket propellant technology but has yet to see widespread use because costs remain high.<ref name="navair.navy.mil"/>