PARAMETRIC SENSITIVITY ANALYSIS OF CONVEX STAR PORT PROPELLANT GRAIN FOR SOLID ROCKET MOTOR
Aqeel Nawaz1, Muhammad Ali Kamran1
ABSTRACT
Grain design takes the central place in a solid rocket motor design activity. Ballistic quality of a designed grain
can be evaluated by two vital indexes known as neutrality and sliver content. Sliver content results in tail-off of
the thrust-time curve. These two measures of merit are an important part of acceptable grain design. This paper is
restricted to the study of convex port star grain geometry and describes parametric evaluation to assess the effects
of seven independent and defining geometric variables of the star and other ballistic factors including density of
propellant and characteristic exhaust velocity on the burn pattern and performance profile for qualitative analysis of
sliver fraction (tail-off)and neutrality. The purpose of the study is to expand the design domain by evaluating entire
convex Star family under both neutral and least sliver content conditions.The computer program associated to it
is essentially the ballistic design analysis of the convex star grain configuration.Results showed that neutrality and
sliver fraction are dependent oncertain parameters. It has been observed that for good neutrality, higher angular
fraction and star angle close to neutrality must be maintained. Sliver fraction depends upon the star geometry and
can be reduced by decreasing angular fraction leading to reduced tail-off. Thus neutrality and reduced tail-off cannot
be achieved simultaneously and trade-off has to be made. However, higher value of characteristic exhaust velocity
(C*) will reduce tail-off.
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