Composite propellant manufacture

Many compounds explode when triggered by a suitable stimulus however, most are either too sensitive or fail to meet cost and production-scale standards, requirements for safety in transportation, and storage stability. Propellants and explosives in large-scale use are based mosdy on a relatively small number of well-proven iagredients. Propellants and explosives for military systems are manufactured ia the United States primarily ia government owned plants where they are also loaded iato munitions. Composite propellants for large rockets are produced mainly by private iadustry, as are small arms propellants for sporting weapons. 

It is in the technique of solidifying the mass that plastisol propellants differ so markedly from composite propellants. In composite propellants, the nonvolatile liquid is comprised of monomers or low molecular weight prepolymers. Solidification is accomplished by completion of the polymerization reactions. Much attention must be given to the degree of completion of these reactions during manufacture so as to minimize changes in physical properties as a consequence of continued slow polymerization, or so-called post-cure, following manufacture. 

The first successful static firing of plastisol propellant took place late in 1950 as part of a broad program conducted by Atlantic Research Corp. to investigate and evaluate plastisol propellants and methods for their manufacture (16). Major attention was directed to poly (vinyl chloride), cellulose acetate, and nitrocellulose, although other polymers were tested for their suitability (17). Patent applications were filed for plastisol propellant compositions and manufacturing processes, based on poly(vinyl chloride) (PVC) (19) and on nitrocellulose (18). The commercial availability of dispersion grade PVC enabled work with this resin to advance rapidly. The balance of this paper is devoted to a discussion of PVC plastisol propellants and their manufacture. 

There are two other mixing systems that should be considered as having progressed beyond the development stage and will likely be instituted as production systems for the manufacture of composite propellant. The first is a proprietary system developed by Rocketdyne and referred to as the Quickmix system (10). Here the solid ingredients, such as oxidizer and fuel additives, are placed in a dilute slurry with low viscosity, volatile, and immiscible carrier. These slurries, a minimum of two, and the fluid polymer and curing agent streams are metered to a continuous fluid mixer. The effluent from the mixer then flows to a separator and... 

However, its application for bulk manufacture of composite propellants for missiles or satellite launch vehicles is not reported in the literature. 

Paris-based Societe Nationale des Poudres et Explosifs (SNPE) France has recently developed a new binder known as butacene (a ferrocene derivative chemically bound to the HTPB backbone) for composite propellants. The butacene-based composite propellants are available for use and have higher burn rates compared with HTPB. In addition, the chief advantage of this binder is that the same facilities which are used for the manufacture of HTPB-based propellants, can be used for the manufacture of butacene-based composite propellants as well. 

The Armed Forces demand a long shelf-life (min 10-12 years) for propellants for use in different rockets and missiles. However, the shelf-life of propellants is limited. There are some chemicals which on their addition to these propellants during their manufacture retard the processes responsible for their deterioration and consequently, increase their shelf-life. The main purpose of addition of these chemicals in propellant formulations is to enhance their shelf-life without adversely affecting their manufacturing processes and properties. Such chemicals or additives are known as stabilizers in case of DB and composite modified double-base (CMDB) propellants whereas anti-oxidants in the case of composite propellants. The additives for this purpose are therefore selected depending on the type of propellant. 

A general discusion of the factors important in choosing the composition and methods of manufacture of the composite propellants was given by Mishuck and Carleton [1]. 

THE TECHNOLOGY OF THE MANUFACTURE OF ROCKET CHARGES CONTA NIG COMPOSITE PROPELLANTS WITH THIOKOL... 

It is characteristic of the technology of the manufacture of rocket charges containing composite propellants with thiokol that the semi-liquid mixture is poured directly into the rocket chamber lined from within with an insulating layer to which the charge adheres tightly ( case-bonded charge). This is a very cheap and rapid method of manufacture. 

The final operation in propellant manufacture is the curing of the binder. The shaped material is placed in a curing oven for 16-48 hr at 80-110°C. The temperature and duration of this operation depend on the composition of the mixture, the dimensions of the charge and the physical properties desired. 

The composition of German rocket propellants manufactured during World War II are given in Table 193. 

The Effect of Temperature Conditioning on Stability and Sensitivity Characteristics and the Chemical Composition of Ml and M6 Propellants Manufactured with Crude or Refined Dinitro-toluene , PATR 4841 (1975) (limited distrib)... 

Burning composite propellants containing ammonium perchlorate Modifications of composite propellants (Mechanical profterties Manufacture of composite propellants Shapes of the propellant grains Explosive properties of composite propellants References... 

A vast amount of work is being done and continuing progress now merits a special modern monograph. Only the principles of the formulation of composite propellants and their manufacture will be given here. The description will... 

The technology of the manufacture of rocket charges containing composite propellants with ihiokol... 

The principles of the manufacture of composite propellants outlined in Vol. Ill are still valid. They are also described by Fluke (14) who gave a few schematic presentations for preparing the mixtures. 

B) W.H. Rinkenbach, Calorific Values of Smokeless Powders as Affected by Variations in Composition, Granulation, etc , PATR 673 (1935) C) C.S. Davis, Development of Improved Propellant and Primer to Reduce Flash in Caliber. 50 Ammunition (Ignition Study) , PATR 1672 (1947) D) W.H. Rinkenbach, Study of Stability of Double-Base Propellants , PATR 1674 (1948) E) J.E. Rainier W.M. Rowe, Propellant for 2ES-40,000 Jato, T29 , PATR 1692 (1948) F) N.S. Garman et al, The Effect of Temperature Conditioning on Stability and Sensitivity Characteristics and the Chemical Composition of Ml and M6 Propellants Manufactured with Crude or Refined Dinitro-toluene , PATR 4841 (1975) (limited distrib)... 

Figure 7.4 Prototype composite propeller built by the Advanced Composites Manufacturing Centre at the University of Plymouth...

Figure 23.25 Composite propeller blade construction used by Dowty Rotol. Source Reprinted from Abraham D, McCarthy R, Design of polymer composite structural components for manufacture by resin transfer moulding (RTM). SAMPE 20 Jubilee Europe Conference Exhibition, in Paris, 13-15 April, 407-415, 1999.

Dow Chemical Company, Midland, Michigan, USA—manufacture epoxy and vinylester resins. Dowty Aerospace Propellers, Gloucester, England—produces composite propeller blades utilizing a fail-safe root retention system. 

Modern composite propellants are heterogeneous powders (mixtures) which use a crystallized or finely ground mineral salt as an oxidizer, often ammonium perchlorate, which constitutes between 60 and 90% of the mass of the propellant. The fuel itself is highly pyrophoric aluminum metal powder. The propellant is held together by a polymeric binder, usually polyurethane or polybutadienes. Additional compounds are sometimes included, such as a catalyst to help increase the burning rate, or other agents to make the powder easier to manufacture. The final product is a rubber-like substance with the consistency of a hard rubber eraser. 

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