Solid rocket engine is mainly composed of shell, solid propellant, nozzle assembly and ignition device, among which the formulation and molding technology of solid propellant, nozzle design and material and manufacturing technology, shell material and manufacturing technology are the most critical links, which directly affect the performance of solid rocket engine. The mixture of all components in the solid propellant formula can be prefabricated into grain by extrusion molding process and then filled into the shell, or can be directly cast into the shell. The housing is directly used as a combustion chamber. The nozzle is used to discharge gas at supersonic speed to generate thrust; The nozzle assembly also has a thrust vector control (TVC) system to control the flight attitude of the missile. Under the control of the ignition instruction, the ignition device releases the safety insurance, ignites the propellant, generates a high-temperature and high-pressure flame, and ignites the propellant in the shell.
Solid rocket engine belongs to chemical rocket engine, with solid substances (energy and working medium) as propellant. After the solid propellant is ignited, it burns in the combustion chamber to produce high temperature and high pressure gas, that is, chemical energy is converted into heat energy; The gas expands and accelerates through the nozzle, and the thermal energy is converted into kinetic energy, which is discharged from the nozzle at a very high speed to generate thrust to push the missile forward.
Developed countries, represented by the United States and the Soviet Union, have experienced four stages in the development of large solid motors. In 1950s, the technologies of strategic solid motors were basically metal shell, CTPB, fixed nozzle and so on. In 1970s, the second generation engine used a large number of composite shells, HTPB propellants, complicated propellant designs and flexible single nozzle with large throat diameter to realize thrust vector control. Since 1980s, advanced design methods and experimental damage research have been widely used. The wide application of carbon fiber shell, high-energy propellant and various flexible extension nozzle structures has greatly improved the solid motor technology. Typical engines are MX, Trident and Poplar -M missile engines. At present, the development of foreign strategic solid motors has entered the fourth generation, and further develops in the direction of excellent comprehensive performance, high reliability, long storage life and simple use and maintenance.
In the future, China's large-scale solid motors will rely on the mature technologies of existing engines, learn from the experience and lessons in development, apply the research results of the strategic solid motor reliability growth project, and at the same time, run through a brand-new design concept, apply a brand-new R&D platform system, and adopt a series of pre-researched new technologies and achievements, so that the comprehensive performance will achieve leap-forward development at the existing technical level. These new technologies are mainly embodied in the overall design of high-pressure solid motor, N- 15/ 15B high-energy propellant, new high-energy propellant, carbon fiber composite shell (all-composite skirt), high-pressure propellant and its supporting thermal insulation lining, extended nozzle technology, light C/C material expansion section of nozzle, ablative throat lining and flexible joint of composite reinforcement, etc. Moreover, the localization degree of key materials of the engine is further improved, the application range of high-energy N- 15 propellant is expanded, and the relationship between the engine and the projectile is more harmonious in performance and structure. Thus, the comprehensive level of strategic solid motors in the future will basically reach the level of MX and Trident D-5 solid motors in the United States.