Method of constructing insulated metal dome structure for a rocket motor

Abstract

An elastomerized phenolic resin ablative insulation particularly suitable for use in connection with the thermal insulation of selected components of rocket motors. A composition for making the elastomerized ablative insulation is disclosed. Furthermore, an associated method of forming calendered sheets of material formed of the composition is disclosed. The preferred ingredients of the disclosed composition include acrylonitryle butadiene rubber, zinc borate, and phenol formaldehyde resin which can be cured and bonded to structures such as domes of open-ended rocket motors and other rocket motor components. The subject elastomerized ablative insulation is well suited for use independently or in connection with other insulative materials to form a thermal barrier which is highly resistant to the heat and the erosive nature associated with the combustion of propellant fuels, for example.

What is claimed is:  
     
         1 . A method of insulating a structure of a rocket motor, comprising: 
 disposing at least one layer of a curable ablative insulative material on at least one surface of a selected rocket motor structure, the curable ablative insulative material comprising acrylonitrile butadiene rubber, zinc borate, phenol formaldehyde resin, zinc oxide, tetramethyl thiuram disulfide, and stearic acid; and    curing the at least one layer of curable ablative insulative material.    
     
     
         2 . The method of  claim 1 , further comprising: 
 bonding the at least one layer of curable ablative insulative material onto the at least one surface.    
     
     
         3 . The method of  claim 2 , further comprising: 
 applying a vulcanizing adhesive to the at least one surface prior to disposing the at least one layer of curable ablative insulative material on the at least one surface.    
     
     
         4 . The method of  claim 3 , wherein applying the vulcanizing adhesive comprises applying at least one member of the group consisting of Chemlok 205, Chemlok 236, and TY PLY BN adhesives.  
     
     
         5 . The method of  claim 1 , further comprising: 
 curing the at least one layer of curable ablative insulative material by exposing the rocket motor structure and the at least one layer of curable ablative insulative material disposed upon the at least one surface to an elevated temperature at a predetermined pressure.    
     
     
         6 . The method of  claim 5 , wherein the curing is conducted in an autoclave after vacuum bagging the rocket motor structure and the at least one layer of curable ablative insulative material disposed upon the at least one surface.  
     
     
         7 . The method of  claim 5 , wherein the curing is conducted in an autoclave at a pressure greater than ambient pressure after vacuum bagging the rocket motor structure and the at least one layer of curable ablative insulative material disposed upon the at least one surface.  
     
     
         8 . The method of  claim 1 , further comprising disposing a shear-ply layer formed of a preselected elastomeric material to at least a portion of the at least one surface of the rocket motor structure and bonding upon the shear-ply layer at least one preformed insulator formed of a preselected material comprising carbonized rayon fibers impregnated with a phenol formaldehyde resin.  
     
     
         9 . The method of  claim 8 , further comprising initially forming the at least one pre-formed insulator formed of a preselected material comprising carbonized rayon fibers impregnated with a phenol formaldehyde resin, curing the at least one pre-formed insulator and thereafter bonding the at least one pre-formed insulator to the shear-ply layer.  
     
     
         10 . The method of  claim 8 , further comprising abutting and bonding an edge of the at least one layer of curable ablative insulative material against an edge of the at least one preformed insulator.  
     
     
         11 . The method of  claim 8 , wherein the shear-ply layer comprises curable elastomeric material and at least one material from a group consisting of silica and aramid.  
     
     
         12 . The method of  claim 1 , wherein the rocket motor structure is a dome shell.  
     
     
         13 . The method of  claim 1 , wherein the rocket motor structure is an igniter pellet cup.  
     
     
         14 . The method of  claim 1 , wherein the rocket motor structure is a stationary nozzle shell.  
     
     
         15 . The method of  claim 1 , further comprising providing constituents of the at least one layer of curable ablative insulative material on an approximate maximum parts per weight basis as follows: 
 acrylonitrile butadiene rubber—100;    zinc borate—80;    phenol formaldehyde resin—120;    zinc oxide—5;    tetramethyl thiuram disulfide—3; and    stearic acid—2.    
     
     
         16 . The method of  claim 15 , further comprising grinding and screening the phenol formaldehyde resin and preweighing and premixing the ground and screened phenol formaldehyde resin and zinc borate together to form a stoichiometric master batch in which the zinc borate acts as a partitioning agent to inhibit agglomeration of the phenol formaldehyde resin.  
     
     
         17 . The-method of  claim 1 , further comprising fibrous elements in the at least one layer of curable ablative insulative material.  
     
     
         18 . The method of  claim 17 , wherein at least a portion of the fibrous elements comprise at least one of the group consisting of aramid, cotton, cellulose, sisal, polybenzamidazole, mineral wool, nylon, carbon and polyester.  
     
     
         19 . A method of insulating a structure of a rocket motor, comprising: 
 disposing a curable ablative insulative material on at least one surface of a selected rocket motor structure, the curable ablative insulative material comprising a curable rubber, a flame retardant, a phenolic resin, and at least one curing system constituent.    
     
     
         20 . The method of  claim 19 , further comprising bonding the curable ablative insulative material onto the at least one surface.  
     
     
         21 . The method of  claim 20 , further comprising applying a vulcanizing adhesive to the at least one surface prior to disposing and bonding the curable ablative insulative material on the at least one surface.  
     
     
         22 . The method of  claim 19 , further comprising curing the curable ablative insulative material by exposing the rocket motor structure and the curable ablative insulative material disposed upon the at least one surface to an elevated temperature at a predetermined pressure.  
     
     
         23 . The method of  claim 22 , wherein the curing is conducted in an autoclave after vacuum bagging the rocket motor structure and the at least one layer of curable ablative insulative material disposed upon the at least one surface.  
     
     
         24 . The method of  claim 19 , further comprising precuring the curable ablative insulative material prior to disposing the curable ablative insulative material upon the at least one surface.  
     
     
         25 . The method of  claim 24 , further comprising applying an epoxy adhesive to the at least one surface prior to disposing the curable ablative insulative material.  
     
     
         26 . The method of  claim 19 , further comprising disposing a shear-ply layer formed of a preselected elastomeric material to at least a portion of the at least one surface of the rocket motor structure and bonding upon the shear-ply layer at least one preformed insulator formed of a preselected material comprising carbonized rayon fibers impregnated with a phenol formaldehyde resin.  
     
     
         27 . The method of  claim 26 , further comprising initially forming the at least one pre-formed insulator formed of a preselected material comprising carbonized rayon fibers impregnated with a phenol formaldehyde resin, curing the at least one preformed insulator and thereafter bonding the at least one pre-formed insulator to the shear-ply layer.  
     
     
         28 . The method of  claim 26 , further comprising abutting and bonding an edge of the curable ablative insulative material against an edge of the at least one preformed insulator.  
     
     
         29 . The method of  claim 26 , wherein the shear-ply layer comprises an elastomeric material containing ethylene propylene diene monomer and at least one material from a group consisting of silica and aramid.  
     
     
         30 . The method of  claim 19 , wherein the rocket motor structure is a dome shell.  
     
     
         31 . The method of  claim 19 , wherein the rocket motor structure is an igniter pellet cup.  
     
     
         32 . The method of  claim 19 , wherein the rocket motor structure is a stationary nozzle shell.  
     
     
         33 . The method of  claim 19 , further comprising providing constituents of the curable ablative insulative material on an approximate maximum parts per weight basis as follows: 
 curable rubber—100;    flame retardant—80;    phenolic resin—120; and    at least one curing system constituent—10.    
     
     
         34 . The method of  claim 33 , further comprising grinding and screening the phenolic resin, and preweighing and premixing the phenolic resin and flame retardant together to form a stoichiometric master batch in which the flame retardant acts as a partitioning agent to inhibit agglomeration of the phenolic resin.  
     
     
         35 . The method of  claim 19 , wherein the curable rubber comprises at least one from the group consisting of butadiene acrylonitrile (NBR), ethylene propylene diene monomer (EPDM), butadiene styrene (SBR), polychloroprene, polyisoprene, polyurethane, polyepichlorohydrin, polybutadiene, chlorinated polyethylene, halobutyl rubbers, and blends thereof; the flame retardant comprises at least one selected from the group consisting of alumina trihydrate, zinc borate, and antimony oxide in combination with a chlorinated hydrocarbon; the phenolic resin comprises at least one selected from the group consisting of a resole type and a novolac type; and the at least one curing system constituent is selected to be appropriate for the curable rubber.