The Grain Integrity Analysis Of Nozzless Solid Booster

Solid ramjet rocket(SRR) with the characteristic of high specific impulse, high reliability, long working time and simple structure, will be used as the main engine of land-air missile and air-air missile in the future. Integrated SRR using the chamber of nozzless solid rocket booster(NSRB) as the supplement chamber of SRR, is more simply than other type SRR, so it can increase the performance of the missile. In this paper, the grain integrality of NSRB was researched. The main results are listed as follows:One dimension fluid model is used to analyze the inner ballistic trajectory of NSRB, on the assumption that queasy constant insulated mass flow, constant burning component fractions and ideal gas condition. The pressure acting on the inner surface of grain is obtained.The solid propellant relaxation module is fitted with three parameter fractional derivative (VFD) model. They were in good agreement from 10-3 to 105 seconds. Three parameter viscoelastic VFD model's accuracy can compare with 19 parameter Prony series model. Long period large fixed strain tension test shows that the stress also meet VFD model until the test specimens are going to be broken with the phenomenon of surface macrocrackls, but the model parameters are different from those in relaxation module test. The VFD model can be used not only in short time vibration analysis but also in long period storage relaxation calculation so long as different parameters are adopted. It shows that the VFD model character the nature of the propellant.The strength of infinite length grain is studied using elastic and VFD model respectively, which represent the tube part of NSBR grain. Stress and stain under the load of grain solidify process is gained. The results showed that the stains of the two model's are equal, while the VFD stress is higher than that of elastic model. The method of dynamic finite element using VFD model is conducted with Laplace transmission and counter Laplace transmission.Using general Kelven model, MARC software is adopted to calculate the strength of the grain under the inner pressure in NSRB firing period. Silicon phenophthalein and 5-â…¢were used as the thermo insulator respectively. The results show that the strength of silicon phenolphthalein case was better the that of 5-â…¢. The combined safety coefficient is calculated under loads of grain solidify process and working inner pressure. The results shows that the grain with silicon henolphthalein thermo insulator can undergo the working pressure in ground firing.In the engineering research, the NSRB grain appeared no disbond or fracture. The calculated inner ballistic trajectory is according with the experimental data. The experimental thrust and pressure are little lower than that of calculated. The grain hold integrality during NSRB firing, which indicate the calculating model in this paper is viable. The achievement of this paper will useful in future NSRB development.