US Government As Represented by the Secretary of the Army

Larry C Warren

William D Stephens

Darren M Thompson

Leo K Asaoka

Tactical missile propellant formulations are inherently sensitive to impact and friction stimuli. The impact and friction insensitivity of some tactical propellant formulations is improved significantly when internal conductive polymers PERCOL&reg;292, (copolymer of a quaternary acrylate salt and acrylamide, Allied Colloids, Inc.) and VERSICON&reg;, (Polyaniline)(Emeraldine salt), green/black powder, Monsanto Company) are added to the formulation. These two conductive polymers were evaluated in a high performance propellant formulation containing the same ingredients now being used in fielded tactical missiles. The impact and friction insensitivity of propellants containing these conductive polymers was improved thirty and sixty six percent, respectively.

Conductive polymers to improve propellant insensitivity-impact and friction-properties

A processing procedure for incorporating bismuth compounds into isocyanate cured hydroxy terminated binder propellants has been discovered. When added to the propellant formulation in ballistic modifier amounts (&gE;0.25%), bismuth salicylate and bismuth &bgr;-resorcylate significantly reduce the potlife to less than 1-hour. It was discovered that to maximize propellant potlife the temperature of the mixture at the time of the addition is critically important. The potlife of propellants containing bismuth compounds can be increased to greater than 15 hours at 70&deg; F., when the temperature of the mixture at the addition step for bismuth, is lowered from the normal addition temperature of 150&deg; F., to 60&deg; F. Depending on the formulation and solids loading, the viscosity of the propellant at 60&deg; F. is not greatly affected.

Processing procedure for isocyanate cured propellants containing some bismuth compounds

Environmentally friendly high performance minimum signature propellants have been demonstrated for use in next generation tactical missile applications. Bismuth salicylate and bismuth citrate have each been used in propellant formulations and evaluated for processing, ballistic, mechanical, aging and signature properties. These high performance formulations have potential to replace current formulations used in some fielded tactical systems. The propellant binder network is achieved using energetic nitramine polymers where inert polymers have been the polymer of choice for minimum signature propellants. The significance of this has to do with achieving propellant specific impulses greater than 245 seconds without nitroglycerin being used in the formulation. This improves propellant safety properties during the propellant processing and the manufacturing of the final missile configurations. The Army has mandated that the next generation propellant formulations show improvements in safety to the end users. These formulations are environmentally friendly (no-lead) and do not use nitroglycerin to achieve high performance.

Minimum signature isocyanate cured propellants containing bismuth compounds as ballistic modifiers

The addition of silicon (Si) powder from about 0.40 to 6.00 weight percent o ammonium nitrate (AN) propellant formulations as a fuel source results in a substantial increase in performance specific impulse (Isp). Theoretical Isp of AN propellant can be enhanced to levels approaching conventional in-service propellant formulations containing much more hazardous ingredients. Using inert or energetic polymer binders, AN propellant formulations are possible that will meet the performance requirements of most tactical missile systems when silicon is used as a fuel additive. Silicon powder when used to replace elemental carbon in most formulations has two major advantages: (1) an increase in theoretical Isp and (2) an improved propellant combustion efficiency by increasing propellant burning temperature. An improvement in propellant burning properties are also expected. The adjustment of weight percent ammonium nitrate in the AN propellant formulation is made as the silicon powder is adjusted over the range of 0.40 weight percent to 6.00 to achieve the preferred results. Formulations are mixed, cast and cured by techniques and methods that are commonly used in the industry and that are known by personnel skilled in the art of propellant formulating.

Silicon as high performance fuel additive for ammonium nitrate

A solid propellant composition employing 2,2-bis(t-butyldicyclopentadienyon)propane (TBD) as the burn rate enhancer in a weight percent from about 2 to about 6 weight percent yields higher threshold values for ignition by impact and improved friction and spark testing values to thereby render the solid propellant composition less hazardous to personnel during handling as compared to similar solid propellant compositions containing Catocene, (2,2-bis(ethyldicylopentadienyliron)propane). The TBD solid propellant composition also comprises from about 9 to about 10 weight percent of hydroxyterminated polybutadiene binder system including an isocyanate curative added in amount of up to 1.0 weight percent and optional modifiers in small amounts with adjustment of the weight percent of other ingredients. Other propellant ingredients comprise a trimodal mix of 200, 1.7, and 0.7 micron particle sizes of ammonium perchlorate oxidizer in amounts from about 66 to about 70 weight percent, and aluminum metal powder in amounts from about 18 to about 20 weight percent. TBD is synthesized to contain no alpha hydrogens, i.e., does not have hydrogens on carbon adjacent to the aromatic ring structure which contributes to long term oxidation and migration problems of Hycat 6D and Catocene.

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Huntsville, AL, United States of America

Larry C Warren