Ammonium nitrate propellants

Characteristics of common inorganic oxidizers are Hsted in Table 5. In any homologous series, potassium perchlorate-containing propellants bum fastest ammonium nitrate propellants bum slowest (79,80). 

Dekker and Zimmerman [24] described a cast ammonium nitrate propellant containing polyester styrene-methyl acrylate binder. 

Greek, Dougherty and Mundy [25] give two typical formulations for castable and extrudable ammonium nitrate propellants (Table 89). 

Use Synthetic intermediate, catalyst in ammonium nitrate propellants, wood impregnating solutions. See barbiturate. 

The enormous differences in temperature one can create depend (disregarding energy dissipation) on heat output, rate of reactioo, and on the physical properties of the ingredients and the products. Of these factors, the phases of the products—solid, liquid, or gaseous —are undoubtedly the most important. We need only think of a certain amount of thermite compared with the same amount of an ammonium nitrate propellant, both of identical heat output per unit weight, to appreciate the extremes of behavior due to phase.changes. 

Polymer-based rocket propellants are generally referred to as composite propellants, and often identified by the elastomer used, eg, urethane propellants or carboxy- (CTPB) or hydroxy- (HTPB) terrninated polybutadiene propellants. The cross-linked polymers act as a viscoelastic matrix to provide mechanical strength, and as a fuel to react with the oxidizers present. Ammonium perchlorate and ammonium nitrate are the most common oxidizers used nitramines such as HMX or RDX may be added to react with the fuels and increase the impulse produced. Many other substances may be added including metallic fuels, plasticizers, stabilizers, catalysts, ballistic modifiers, and bonding agents. Typical components are Hsted in Table 1. 

Oxidizers. The characteristics of the oxidizer affect the baUistic and mechanical properties of a composite propellant as well as the processibihty. Oxidizers are selected to provide the best combination of available oxygen, high density, low heat of formation, and maximum gas volume in reaction with binders. Increases in oxidizer content increase the density, the adiabatic flame temperature, and the specific impulse of a propellant up to a maximum. The most commonly used inorganic oxidizer in both composite and nitroceUulose-based rocket propellant is ammonium perchlorate. The primary combustion products of an ammonium perchlorate propellant and a polymeric binder containing C, H, and O are CO2, H2, O2, and HCl. Ammonium nitrate has been used in slow burning propellants, and where a smokeless exhaust is requited. Nitramines such as RDX and HMX have also been used where maximum energy is essential. 

Propellants with ammonium nitrate have very low burning rates (0.01 cm/s). 

S. H. Hasty, Ammonium Nitrate Pocket Propellants, CPTR 91-48, CPIA Pubhcations, Johns Hopkins University, Laurel, Md., Sept. 1991. 

L. Asaoka, Phase Stabili d Ammonium Nitrate Effects on Minimum Signature Propellant Properties, Vol. 5, 3 CPIA Pubhcation 550, Anaheim, Calif., 1990. 

Most limestone quarries use either 100% ammonium nitrate [6484-52-2] (fertilizer grade) and fuel oil (ANFO), or a combination of ANFO and ammonium or gelatin dynamite, for blasting (see Explosives and propellants, explosives). After blasting, oversized boulders usually are reduced to manageable sizes by drop ball cranes. 

Industrial. Nitric acid is itself the starting material for ammonium nitrate, nitroglycerin [55-63-0] trinitrotoluene [118-96-7]., nitroceUulose [9004-70-0] and other nitrogen compounds used in the manufacture of explosives (see Explosives and propellants). Nitric acid is made by oxidation of ammonia to nitrogen dioxide [10102-44-0] which is subsequently absorbed by water. 

When used in blasting, ammonium nitrate is mixed with fuel oil and sometimes sensitizers such as powdered aluminum. Lower density ammonium nitrate is preferred for explosive formulation, because it absorbs the oil more effectively. When detonated,these mixtures have an explosive power of 40 to 50% that of TNT (see Explosives and propellants). 

A small but important use of ammonium nitrate is in the production of nitrous oxide during the 1980s consumption for this purpose averaged about 30,000 t. The gas is generated by controlled heating of ammonium nitrate above 200°C. Nitrous oxide is used primarily as an anesthetic and as an aerosol propellant for food products (see Anesthetics Aerosols). 

Sodium nitrate is used as a fertiliser and in a number of industrial processes. In the period from 1880—1910 it accounted for 60% of the world fertiliser nitrogen production. In the 1990s sodium nitrate accounts for 0.1% of the world fertiliser nitrogen production, and is used for some specific crops and soil conditions. This decline has resulted from an enormous growth in fertiliser manufacture and an increased use of less expensive nitrogen fertilisers (qv) produced from synthetic ammonia (qv), such as urea (qv), ammonium nitrate, ammonium phosphates, ammonium sulfate, and ammonia itself (see Ammonium compounds). The commercial production of synthetic ammonia began in 1921, soon after the end of World War I. The main industrial market for sodium nitrate was at first the manufacture of nitric acid (qv) and explosives (see Explosives and propellants). As of the mid-1990s sodium nitrate was used in the production of some explosives and in a number of industrial areas. 

WEB Dinitrogen oxide, commonly called nitrous oxide, is used as a propellant gas for whipped-cream dispensers. It is prepared by heating ammonium nitrate to 250°C Water vapor is also formed. 

For civilian aircraft the facility for rapid starting is not important and cartridge operation is not often employed, particularly because it involves storing and handling explosives, even though the hazards of these explosives are those of fire and not of detonation. For military purposes, however, particularly for fighter aircraft which are best scattered on an airfield, a rapid start is of considerable importance. Therefore cartridge operated starters are much used for these aeroplanes. In Britain, development has been essentially with propellants based on ballistite, namely double base propellants of the solventless type, whereas in the United States composite propellants based on ammonium nitrate have proved more popular. 

Ammonium nitrate (AN NH4NO3) is a white, crystalline material, the crystal structure of which varies with temperature.melting point is 442 K and its heat of fusion is 71.4 kj kg . Though the mass fraction of oxygen of AN is 0.5996, it is highly hygroscopic and absorbs moisture from the atmosphere to form liquid AN acid. This limits its application in propellants and pyrolants. However, AN is widely used as an oxidizer of explosives such as slurry explosives and ANFO (ammonium nitrate fuel oil) explosives. 

The physicochemical properties of explosives are fundamentally equivalent to those of propellants. Explosives are also made of energetic materials such as nitropolymers and composite materials composed of crystalline particles and polymeric materials. TNT, RDX, and HMX are typical energetic crystalline materials used as explosives. Furthermore, when ammonium nitrate (AN) particles are mixed with an oil, an energetic explosive named ANFO (ammonium nitrate fuel oil) is formed. AN with water is also an explosive, named slurry explosive, used in industrial and civil engineering. A difference between the materials used as explosives and propellants is not readily evident. Propellants can be detonated when they are subjected to excess heat energy or mechanical shock. Explosives can be deflagrated steadily without a detonation wave when they are gently heated without mechanical shock. 

Ammonium perchlorate (NH ClO ) This is a good oxidizer, and can be used to make excellent propellants and colored flames. However, it is a self-contained oxidizer-fuel system (much like ammonium nitrate). The mixing of NH f (fuel) and ClOa (oxidizer) occurs at the ionic level. The potential for an explosion cannot be ignored. Conclusion if this material is used, it must be treated with respect and minimum quantities of bulk powder should be prepared. 

Ishpeming, Mich - Water gel Kenvil, N J — Smokeless powder, diazo Louisiana, Mo — Ammonium nitrate, nitric acid Parlin, N.J — Nitrocellulose Port Ewen, NY— Detonators, initiators Rocket Center, W Va - Propellants Radford, Va — Government owned, company operated... 

Humidity can affect explosives and propellants both adversely and beneficiently. If the humidity is very high, an explosive can pick up enough moisture to cause it to deteriorate or malfunction. A prime example of this is Ammonium Nitrate which must be stored and handled in special dehumidified areas to prevent caking. The humidity above which a substance deliquesces, or below which it ceases to be hygroscopic is called the critical relative humidity (CRH). 

In addition to the general tests listed above a number of studies tests for specific ingredients have been published. These data for propellants, NC and for ammonium nitrate (AN) are summarized below ... 

Low Melting Ammonium Nitrate Explosives. See under Ammonium Nitrate Blasting Explosives, High Explosives and Propellants (AN High Explosives) in Encycl 1 (1960), A346-R to A348-L, A352-R... 

Rocket fuel Ammonium nitrate. Ammonium perchlorate. Polyester resin. Charcoal powder Improvised projectile propellant... 

Explosive Compositions are mixtures of explosive and non-explosive substances. They are listed in this Encycl as individual items such.e.s Amatols, Ammonals, Ammonium Nitrate Blasting Explosives, Black Powder, Compositions A, B, C D, Cyclonites, Dynamites and as Explosive Compositions listed-further in this Vol. (See also Composite Propellants described in Vol 3, pp C464 to C473)... 

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