Specific impulsion

Elemental fluorine has been studied as a rocket propellant as it has an exceptionally high specific impulse value. 

Enef Delivery Requirements Specific impulse or force... 

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. 

Aluminum-containing propellants deflver less than the calculated impulse because of two-phase flow losses in the nozzle caused by aluminum oxide particles. Combustion of the aluminum must occur in the residence time in the chamber to meet impulse expectations. As the residence time increases, the unbumed metal decreases, and the specific impulse increases. The soHd reaction products also show a velocity lag during nozzle expansion, and may fail to attain thermal equiUbrium with the gas exhaust. An overall efficiency loss of 5 to 8% from theoretical may result from these phenomena. However, these losses are more than offset by the increase in energy produced by metal oxidation (85—87). 

Oxidant Fuel Ratio oxidant/fuel Specific impulse, s... 

P. Kuent2mann, Specific Impulse Tosses ofMetalli d Solid Propellants, PTD-NC-23-2717-74, Air Eorce Eoreign Technology Division, Wright Patterson Air Eorce Base, Dayton, Ohio, 1974. 

Propellants and Explosives. Hydrazine fuels include anhydrous hydrazine (AH), monomethyUiydrazine (MMH), and unsymmetrical dimethyUiydrazine (UDMH) for military and space programs. These compounds are used mainly as bipropeUant fuels, ie, with oxidizers, in rockets such as the Titan, MX missile, and the Ariane (UDA4H7X30. Using oxygen or fluorine as the oxidizer, hydrazine is exceeded only by hydrogen in specific impulse, ie, kilograms of thmst developed for each kilogram of fuel consumed per second (196). 

Detonation flame arresters and associated piping mnst be able to withstand the effects of explosion transients that inclnde the pressnre or pres-snre-related force, the specific impulse (integral of the dme versus overpressure) or net impulse (upstream minns downstream impulse) highspeed gas momentnm transfer and flnx, and temperatnre-, heat-, and dier-mal-flnx related loads (White and Oswald 1992). Wliite and Oswald con-... 

There are no clearly discernable, broadly applicable, correlations between the 6-inch and 1 S-inch deflagration and detonation experiments. Therefore, comparisons were done on a parameter-byparameter basis. However, comparisons of data taken during experiments with the two pipe sizes reveal that enough scale-related differences exist that interpolation between the two scales for an intermediate size should be done only where conditions are very similar. Then, overpressure and specific impulse can be estimated based on L/D. 

Venting an explosion ahead of a flame arrester can reduce the thermal flux and the impulse to which the arrester is subjected. Test results indicate that peak side-on overpressure is halved, specific impulse is reduced by a factor of three, and the temperature is substantially reduced. However, overpressure and flame speed at the flame arrester do not appear to be changed significantly. 

Specific Impulse The area under the overpressure versus time curve. 

Application of the Baker-Strehlow method for evaluating blast effects from a vapor cloud explosion involves defining the energy of the explosion, calculating the scaled distance (/ ), then graphically reading the dimensionless peak pressure (Ps) and dimensionless specific impulse (i ). Equations (4.41) and (4.42) provide the means to calculate incident pressure and impulse based on the dimensionless terms. 

Figure 4.21. Dimensionless blast side-on specific impulse for vapor cloud explosions (Strehlow et al. 1979).

Uses. A review of its use as an oxidizer in rocket proplnts is given in Ref 6. A 50 50 mixt of N trifluoride F, with ammonia as fuel, yields a specific impulse of 295sec and a d impulse (specific impulse X d) of 340 (Ref 6). Mixts with methyl fluoride, 1,1 -difluoropropane, and 1,3-dlfluoropropane have been patented as monoptoplnts(Ref 9). AN trifluoride/H flame has been proposed as a cutting and welding torch (Ref 8)... 

Petrin acrylate proplnts. PETRIN acrylate could be used as a mono pro pint because it has a specific impulse of 214 lb-sec/lb and a burning rate of 0.2 inch/sec. The addition of an oxidizer increases both the impulse and burning rate A typical compn is as follows ... 

Measured specific impulse 238 lb-sec/lb, at d 1.3g/cc See also under Pentaerythritol Trinitrate in this Vol... 

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