Rocket motors, insulation

The cycloaliphatic resins also are clearly superior in arc resistance and arc track resistance. This has led to applications in the tension insulators, rocket motor cases and transformer encapsulation. 

The products also are clearly superior in arc resistance and are track resistant. Thus although bisphenol A-based epoxies decompose in the presence of a high-temperature arc to produce carbon which leads to tracking and insulation failure, cycloaliphatic epoxies oxidize to volatile products which do not cause tracking. This has led to such applications as heavy-duty electrical castings and laminates, tension insulators, rocket motor cases, and transformer encapsulation. 

Phenolic resins are adaptable to many applieations. The list is very long, however, the major uses are wood binders, glass insulation binders, molding compounds, laminates, foundry binders, coatings, friction linings, abrasives, and oil well propants [59-66]. They have found their way into a number of new, high technology uses such as rocket motor wear parts, military armor, sports equipment. 

FIGURE 12.18 Stress-strain curves of rubber-fiber composites developed for solid rocket motor insulator A, ethylene-propylene-diene monomer (EPDM) rubber-carbon fiber composites B, EPDM mbber-melamine fiber composites C, EPDM mbber-aramid fiber composites and D, EPDM rubber-aramid pulp composites. 1 and 2 stands for unaged and aged composites respectively. Carbon fiber- and melamine fiber-reinforced composites contain resorcinol, hexamine, and silica in the concentrations 10, 6 and 15, respectively and aramid fiber- and aramid pulp-based composites contain resorcinol, hexamine, and silica in the concentrations 5, 3 and 15, respectively. (From Rajeev, R.S., Bhowmick, A.K., De, S.K., and John, B., Internal communication. Rubber Technology Center, Indian Institute of Technology, Kharagpur, India, 2002.)... 

The temperature and composition of propellant combustion products are of interest to those concerned with materials of construction and insulation for the combustion chamber and nozzle of the rocket motor. These values are readily computed from basic thermodynamic data for the specific propellant composition and operating pressure of interest with the aid of today s large-scale digital computers. By way of illustration, however, the products of combustion computed this way for the three typical plastisol propellants given in Table I are shown in Table III for a combustion pressure of 1000 p.s.i.a. Approximate propellant composition is also shown for convenient reference. 

Such polymeric materials or rubbers are known as insulating materials or insulators and the process of their application is known as insulation. The motor insulation not only provides protection to motor but also functions as an inhibitor. The case-bonded motors have a little less inert mass and as a result, give slightly better performance. However, they are more stressed and more difficult and expensive to manufacture. Many tactical missiles and almost all larger rockets or missiles for defense and space applications use case-bonded motors. 

Neoprene and nitrile rubbers (gum stocks) filled with silica are generally used for insulation of rocket motors and the general process consists of (i) sand blasting of rocket motor followed by cleaning with petrol or organic solvent and drying,... 

Another rubber which appears to be of interest for insulation of rocket motors is hydrogenated hydroxy-terminated polybutadiene (HHTPB). As this rubber is derived from HTPB, it is more compatible and would also have strong bond with the HTPB-based propellants. Further, as the quantum of unsaturahon is considerably reduced in HHTPB, the life of rocket motors insulated with HHTPB will also be more. In a nutshell, the use of HHTPB results in an increased stability to... 

Herring, LG. (1985) Elastomeric insulating materials for rocket motors. 

Rao, S.S., and Ninan, K.N. (2000) Development of EPDM rubber based low density insulator for solid propellant rocket motors. Proc. 3rd Inti High Energy Materials Conf. and Exhibit, Dec. 6-8, 2000, Thiruvananthapuram, pp. 265-268. 

Guillot, D.G (2008) Method of insulating case of solid propellant rocket motor. U S Patent No. 7,410,607. 

Guillot, D.G. (2000) Novel EPDM rocket motor insulation. Inti Patent WO 00/43445. 

Metcalf, G.S. and White, W.E. 2003. Method of constructing insulated metal dome structure for a rocket motor. U.S. Patent 6,544,936. 

A solid propellant rocket motor is quite simple in concept, although in practice a complete motor is more complex. As shown in Fig. 37.15, the rocket propellant is contained within a case, which may be metal or a reinforced high-performance composite. Frequently, the case is internally shielded by a bonded layer of insulation. The insulation is coated with a liner that bonds the propellant to the insulation. The integrity of the propellant-to-liner bond is of utmost importance failure at this interface during a motor firing can result in a sudden increase in the area of propellant surface exposed to combustion, with potentially catastrophic results. 

Siltemp [Ametek], TM for a substantially pure fibrous silica for use in rocket and missile construction and for high-temperature insulation of motor components and similar applications. 

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