In this paper the ageing behaviour of a composite solid propellant has been described by measuring its mechanical and ballistic properties at regular intervals during an accelerated ageing period. The solid propellant consists of Ammonium Perchlorate (AP), Hydroxyl Terminated Poly Butadiene (HTPB), Aluminium (Al) and ballistic modifiers, burning rate catalyst and other additives. Propellant blocks were aged at constant relative humidity of 50% at three different storage temperatures 70, 60 and 55 oC. The mechanical test conducted on the propellant was uniaxial tension test. The mechanical properties measured in the tension test were Young's modulus, breaking stress and percentage of elongation at the time of break. The propellant ballistic properties like burning rate and burning rate exponent were also determined during the ageing period from the ballistic tests. From this study it is observed that burning rate at low pressures did not undergo significant changes during the ageing period but the changes in Young's modulus and relaxation modulus were significant.

Key words: AP-HTPB based solid Propellant, Burning rate, Ageing behaviour.