Propellant Performance

A practical application of dinitrogen pentoxide in methylene chloride reagent involves the nitration of either ammonium carbamate or nitrourethane, followed by ammonolysis to yield ammonium dinitramide, an energetic oxidizer with enormous potential for use in future high performance propellant compositions. This important reaction is discussed in more detail in Chapter 9. 

Treatment of the bis(pyrazoyl)tetrazine (197) with an excess of hydrazine hydrate generates 3,6-bis(hydrazino)-l,2,4,5-tetrazine (208), a compound which might find use as an energetic additive in high performance propellants. Several salts of (208) have been reported, including the dinitrate and diperchlorate. 3,6-Dichloro-l,2,4,5-tetrazine (209), the product from treating (208) with chlorine in acetonitrile, reacts with the sodium salt of 5-aminotetrazole (210) to yield (211) (C4H4N14 - 79 % N). ... 

It may however, be noted that these values for different parameters are influenced by purity, morphology and particle size of the sample. The calculated values of VOD for FOX-7 and RDX are 9090ms 1 and 8940 ms 1 respectively (Cheetah Thermochemical Code). Based on these results, it was concluded that FOX-7 is better than RDX which is used as a benchmark explosive for comparison with other explosives. Consequently, it is an attractive ingredient for application in high performance IM compliant explosive formulations. FOX-7 also increases the burning-rate in propellants and as a natural consequence, is of interest for high performance propellants. 

The propellant performances calculated using ISPBKW are shown in Table 2.13 for various high performance propellants, including those of Table 2.5 whose explosive performance has been determined. 

A comparison of the characteristics associated with propellant burning, explosive detonation, and the performance of conventional fuels (see Coal Gas, NATURAL Petroleum) is shown ia Table 1. The most notable difference is the rate at which energy is evolved. The energy Hberated by explosives and propellants depends on the thermochemical properties of the reactants. As a rough rule of thumb, these materials yield about 1000 cm of gas and 4.2 kj (1000 cal) of heat per gram of material. 

Both RDX and HMX are substantially desensitized by mixing with TNT to form cyclotols (RDX) and octols (HMX) or by coating with waxes, synthetic polymers, and elastomeric biaders. Most of the RDX made ia the United States is converted to Composition B (60% RDX, 40% TNT, 1 part wax added). Composition A5 (RDX 98.5/stearic acid 1.5) and composition C4 (RDX91/nonexplosive plasticizer) account for the next largest uses. HMX is used as a propellant and ia maximum-performance plastic bonded explosives such as PBX 9401 and PBX N5 and the octols (147—150). 

Table 4. Thermochemical, Thermodynamic, and Performance Characteristics of Nitrocellulose Gun Propellants ...

Experimental Determination of the Burning Rate. Experimental determinations of the burning rate are made with the closed tomb for gun propellants and the strand burner for rocket propellants. The closed bomb is essentially a heavy-wahed cylinder capable of withstanding pressures to 689 MPa (100,000 psi). It is equipped with a piezoelectric pressure gauge and the associated apparatus requited to measure the total chamber pressure, which is directly related to the force of the propellant. It also measures the rate of pressure rise as a function of pressure which can then be related to the linear burning rate of the propellant via its geometry. Other devices, such as the Dynagun and the Hi—Low bomb, have also been developed for the measurement of gun propellant performance. 

RocketPropella.nts, Liquid propellants have long been used to obtain maximum controUabiUty of rocket performance and, where required, maximum impulse. Three classes of rocket monopropellants exist that differ ia the chemical reactions that release energy (/) those consisting of, eg, hydrogen peroxide, ethylene oxide, C2H4O and nitroethane, CH2CH2NO2 that can undergo internal oxidation—reduction reactions (2) those... 

Black Powder. Black powder is mainly used as an igniter for nitrocellulose gun propellant, and to some extent in safety blasting fuse, delay fuses, and in firecrackers. Potassium nitrate black powder (74 wt %, 15.6 wt % carbon, 10.4 wt % sulfur) is used for military appHcations. The slower-burning, less cosdy, and more hygroscopic sodium nitrate black powder (71.0 wt %, 16.5 wt % carbon, 12.5 wt % sulfur) is used industrially. The reaction products of black powder are complex (Table 12) and change with the conditions of initia tion, confinement, and density. The reported thermochemical and performance characteristics vary greatly and depend on the source of material, its physical form, and the method of determination. Typical values are Hsted in Table 13. 

L. S. Lussier and co-workers, "The Use of Thermodynamic Codes for Comparison of Propellant Performance," in Tifth International Gun Propellant... 

Fan Rating. Axial fans have the capabiUty to do work, ie, static pressure capabiUty, based on their diameter, tip speed, number of blades, and width of blades. A typical fan used in the petrochemical industry has four blades, operates neat 61 m/s tip speed, and can operate against 248.8 Pa (1 in. H2O). A typical performance curve is shown in Figure 11 where both total pressure and velocity pressure are shown, but not static pressure. However, total pressure minus velocity pressure equals static pressure. Velocity pressure is the work done just to collect the air in front of the fan inlet and propel it into the fan throat. No useflil work is done but work is expended. This is called a parasitic loss and must be accounted for when determining power requirements. Some manufacturers fan curves only show pressure capabiUty in terms of static pressure vs flow rate, ignoring the velocity pressure requirement. This can lead to grossly underestimating power requirements. 

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