Infrared irradiance reduction in minimum smoke propellants by addition of potassium salt

One of the plume characteristics of minimum smoke propellant is the infrared (IR) radiation signature, which may be useful for detection of rocket. The IR irradiance is known to be reduced by afterburning suppression in rocket plume by addition of potassium salt in propellant. The minimum smoke propellant with nitrate ester polyether (NEPE) binder system and nitramine oxidizers was researched for the afterburning and IR irradiance difference according to the content of potassium salt as afterburning suppressant in propellant formulation. The propellants were formulated to satisfy the level of AGARD smoke class AA and potassium sulfate was selected as afterburning inhibitor suitable for NEPE propellant. The afterburning flame length and mid-range IR intensity were measured, while conducting static firing tests of 6 inch (15.24 cm) standard rocket motors loaded with minimum smoke propellants of the different contents of potassium sulfate. The total IR irradiance of HMX/RDX propellant with 1.1% potassium sulfate was reduced to about 23% compared to the propellant without afterburning suppressant due to the inhibition of afterburning. Also, the total IR irradiance of the HNIW (30%)/RDX propellant was found to be almost three times more than that of the HMX/RDX propellant although the content of potassium sulfate was the same of 1.1% in both propellants.