Showing papers on "Burn rate (chemistry) published in 1991"

A Theoretical Study of the Combustion of Magnesium/Teflon/Viton Pyrotechnic Compositions

Abstract: : A theoretical study has been conducted using the NASA-Lewis CEC 76 computer code to model the combustion of pyrotechnic compositions based on magnesium/Teflon/Viton. The study examines the effect of formulation changes on the distribution of reaction products, the reaction temperature and the heat of reaction. The maximum temperature and heat are produced in the stoichiometric fuel concentration whilst the reaction products change significantly with the concentration of magnesium. The Teflon and Viton oxidizers generally have only a minor effect on the system thermodynamics. The major reaction products are magnesium fluoride, magnesium and solid carbon. The proportion of carbon as a combustion product remains relatively constant over a large range of fuel or oxidant concentration. The choice of the optimal MTV composition for IR decoy applications appears to be based more on burn rate and ignitability requirements than on temperature, heat output or optimization of reaction products.

Chlorine-free solid rocket propellant for space boosters

Abstract: A stable chlorine-free solid rocket propellant composition containing a low energy binder component having an HEX value not exceeding about 0 cal/gm and comprising, in combination, a nitrate salt and/or phase stabilized nitrate salt as oxidizer component, a Mg/Al alloy of limited Mg content as a fuel component, at least one energetic plasticizer component, and a burn rate catalyst.

Effects of liquid burn rate catalysts on Rheological Properties of High-Energy Composite Propellants

Abstract: Effects of several liquid burning rate catalysts on rheological properties of composite rocket propellants on the basis of hydroxy-terminated polybutadiene as a binder and ammonium perchlorate as an oxidizer have been examined. Theoretical explanation of the observed effects of liquid catalysts on certain rheological properties of the mentioned propellants are given. Laboratory procedures for synthesis of used catalysts are described. The results of physico-chemical characterization of synthesized catalyst are also presented.

Deuterium isotope effects during RDX combustion : mechanistic burn rate-controlling step determination

Abstract: High pressure (500 psig/3.55 MPa and 1000 psigl6.99 MPa) burn rate comparisons from the combustion of solid RDX (hexahydro- 1.3,.5-trinitro-1,3,5-triazine) and perdeuterio-labeled RDX-dh cylindrical pressed pellets reveals a large kinetic deuterium isotope cffect (KDIE). This experimental KDIE confirms that chemical reaction kinetics are a significant mechanistic factor in controlling the inherent RDX burn rate and further shows the six-membered RDX hcterocycle's rate-controlling mechanistic step during com- bustion is the same as that previously reported for its larger eight-membered HMX (octahydro-l.3,5,7-tetranitro-l.3.5,7 tetrazocine) homologuc. As with HMX. This experimental KDTE approach also demonstrates a direct mechanistic relationship between RDX's higher order cornbustion regime and its ambient pressure thermochemical decomposition process.

Liquid oxygen/metal gelled monopropellants

Abstract: The objectives of this program were to establish the feasibility of metallized/liquid oxygen monopropellants and select the best monopropellant formulation for continued study. The metal powders mixed with the liquid oxygen were aluminum/magnesium (80/20), silicon and iron (Iron was only tested for burning properties). The formulations were first evaluated on whether they detonated when ignited or burned. The formulations only burned when ignited. The viscosity for the formulations ranged from 900 cps to 100 cps at shear rates up to 300 seconds(sup -1). Two percent (by weight) of Cab-O-Sil was added to the aluminum and aluminum/magnesium formulations for gelling while the silicon formulation used three percent. Within a seven hour period, settling was suggested only in the 29 percent aluminum and 29 percent aluminum/magnesium formulations. The monopropellants were burned in a cylinder submerged in a liquid nitrogen bath. Experimental data at ambient pressure indicated that the monopropellants were extinguished when the flame front reached regions submerged under the liquid nitrogen. The burn rate increased dramatically when burned in a cylinder enclosure with less heat sink available to the monopropellant. The test results were inconclusive as to whether the increased burn rate was due to the lower heat sink capacity or the small amount of pressure (2 psi) generated during the burning of the monopropellant. The burning of the aluminum and aluminum/magnesium resulted in a brilliant white flame similar to that of an arc welder. These monopropellants burned in a pulsating manner with the aluminum/magnesium appearing to have less pulsating combustion. The silicon monopropellant burned with an orange glow. No sparks or energetic burning was apparent as with the aluminum or aluminum/magnesium.

A Novel Technique to Stimulate the Flow in a Solid Propellant Rocket.

Abstract: : An experimental study has been carried out to investigate the occurrence of acoustically generated turbulence and the possible role of this turbulence in the velocity coupling phenomenon that is believed to occur in some acoustically unstable solid propellant rocket motors. A new technique has been developed to carry out this investigation. The burning propellant is simulated by subliming dry ice. This simulation allows relatively long run times and ease of instrumentation as compared to using actual propellants. The technique also reduces the possibility of turbulence being generated by the injection process in a cold flow simulation. Subliming dry ice also has a positive pressure exponent, similar to, but weaker than, an actual propellant. In the experiment a small section of dry ice is contained in a closed tube approximately two meters long which is equipped with a mechanically driven piston at one end. This piston is used to produce strong pressure and velocity waves which propagate over dry ice.