M.Sc Thesis


M.Sc StudentMeshali Omri
SubjectExamination of the Safety Factor in Solid Propellant Grain
under Pressure Loads during Ignition
DepartmentDepartment of Design and Manufacturing Management
Supervisors ASSOCIATE PROF. Haim Abramovich
DR. Emanuel Ore
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

The main element in a solid rocket motor is the propellant, which is a viscoelastic material whose properties depend on temperature, time and strain rate. The two main mechanical loads applied on the propellant grain are thermal loading and ignition pressure.

The structural integrity assessment process which is used to evaluate the ability of a solid propellant grain to withstand the applied loads is a major factor in the design of solid rocket motors. The prediction methods for the safety factor (SF) vary from countries and companies.

In the present study the structural integrity of a propellant has been examined through an analogue motor SEC (Strain Evolution Cylinder) under thermal and pressure loads. A dedicated experimental system had been designed, built and calibrated to test the SEC motors. In parallel structural analyses were performed using the finite element method to assess the failure and provide numerical results to be compared with a series of tests being carried out.

The tests performed showed an unexpected failure mode. The failure in 2 of the 3-tests performed that led to the grain failure, was by aggressive propellant ignition during increasing the pressure. Most probably the failure occurred, because of hot spot in the propagating crack tip.