Nondestructive Aging and Cross-Link Density Damage Detection in Solid Rocket Fuel Propellant

Abstract

Aging effects can have a significant consequence on the mission readiness of solid propellant rocket systems. A potential end result of grain cracking caused by aging is the catastrophic failure of the rocket motor. Propellant changes leading to grain cracking are an increase in cross -link density and/or induced dam age. The detection of this crack generating degradation within the solid propellant is critical. Initial manufacturing variability creates rocket motor assets with varying vulnerability to grain cracking. This significantly raises maintenance requirement s, reduces operational life times and threatens mission readiness. Several experimental methods are currently used to determine the cross link density of solid propellant. Unfortunately, these cross -link density measurement methods are all destructive te st determinations meaning the solid rocket propellant material must be dissected out of the main rocket asset for analysis. Dissection work is extremely expensive in terms of manpower, materials and money. Current non -destructive evaluation (NDE) and non -destructive inspection (NDI) techniques offer limited capability for the determination of cross -link density and/or induced damage. Photon Induced Positron Annihilation (PIPA) has demonstrated that non -destructive results on strain buildup and grain crac king in solid rocket propellant can be determined using the PIPA technique and that propellant damage could be detected using this technique through the rocket case of actual rocket systems, which could result in accurate and reliable assessments of compon ent readiness either at the manufacturing level or during field inspections. This NDI process will provide reliable material damage characterization including the buildup of defects and changes in the atomic structure of the propellant without disassembly and at detection levels below current NDI methods.