Patent Application
20250236569
Compositions for modifying the burning rate of solid rocket motor propellants, utilized in military operations, have included expensive, toxic, and/or polluting materials, most notably lead.
Features and advantages of embodiments of the present application will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical, components.
A more particular description of the application briefly described above will be rendered by reference to specific data presented in the tables and in the appended drawings. Understanding that these tables and drawings depict only information for typical embodiments of the application and are not, therefore, to be considered limiting of its scope, the application will be described and explained with additional specificity and detail using the accompanying drawings in which:
The present application pertains to the field of solid rocket propellants and is related to compositions for safely modifying the burning rate of solid rocket propellants without altering bulk properties such as processing properties, mechanical properties, aging properties, and bulk hazard classification properties. More particularly, the present application is related to solid rocket double-based propellant, that is, nitrocellulose-based, homogeneous propellants utilizing a lead-free ballistic modifier to modify the burning rate thereof.
Solid propellants are generally classified as homogeneous or composite. Homogeneous solid propellants usually contain nitrocellulose and are considered true monopropellants with each molecule containing elemental fuels and oxygen for combustion. The homogeneous nitrocellulose propellants are further subclassified as single, or double base, depending on the composition, nitrocellulose as the sole combustible or nitrocellulose combined with an energetic plasticizer namely nitroxy compounds, such as nitroglycerin.
For desired operation of a rocket motor or similar device, the propellant burning rate must be controlled and predictable. If the propellant burning rate is excessively fast, the pressure created within the casing may exceed the casing design capability, resulting in damage or destruction to the device. If the propellant burning rate is too slow, the resulting thrust may not be sufficient to propel the rocket/missile over the desired course. When the hypothetical burning rates of catalyzed and uncatalyzed double base propellant is plotted and on a base 10 logarithmic plot of burning rate in inches per second on the Y-axis and pressure in pounds per square inch on the X-axis in
This application can reduce exposure to toxic lead contaminants that affect even more than the warfighter health and the environment, but also affect workers and communities that are involved with the specific processes starting from propellant production all the way to demilitarization.
The present application includes modifier formulations used to effect super-rate burning of double-based propellants. These modifiers are particularly useful in solid rocket propellants. The double-based propellant modifier formulations of the present application include a combination of separate, that is, physically combined, cerium and carbon components. It has been discovered that the incorporation of a cerium modifier component and a carbon component provides unique advantages in controlling these parameters and imparts energetic properties advantageous for super-rate burning to the combination of the components once the modifier components are incorporated into the double-based propellant.
The terminology, double-based solid propellant composition, is intended to include propellant compositions based on a colloid of nitrocellulose and plasticizer(s) for the nitrocellulose, where the major plasticizer component by weight is nitroglycerin. The plasticizer(s) can be either the explosive or energetic type, the nonexplosive or inert type, or a combination of the two. It is to be understood that while the application discusses in detail double-based compositions, the application is equally applicable to any nitrocellulose-based composition, that is any propellant composition based on a colloid of nitrocellulose and plasticizer(s) for the nitrocellulose. Therefore, nitroglycerin in a colloid with nitrocellulose can be replaced with one or more conventional inert or energetic plasticizers. These variations in compositions alter propellant physical properties as well as burning rate. All or part of the energizing plasticizer such as nitroglycerin is replaced with these conventional plasticizers to form the double-based compositions discussed hereafter. By this means, a wide range of suitable nitrocellulose-based propellants can be prepared. These novel propellant formulations can be made in a variety of well-known methods to include but not be limited to slurry, rolling, extruding, and/or blocking methods described in U.S. Pat. Nos. 3,093,523, 3,102,834, 2,982,638, and 2,771,351.
Examples of the energizing plasticizer include but are not limited to the nitrate esters of polyhydric alcohols such as nitroglycerin (NG), butane triol trinitrate (BTTN), diglycerol tetranitrate (DGTN), diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN), and trimethylolethane trinitrate (TMETN); and nitramines such as N-Methyl-N-(2-nitroxyethyl)nitramine (MeNENA), N-Ethyl-N-(2-nitroxyethyl)nitramine (EtNENA), and N-Butyl-N-(2-nitroxyethyl)nitramine (BuNENA); glycidyl azide polymer (GAP) plasticizer or glycidyl azide; and combinations and mixtures thereof, and the like.
Examples of inert plasticizers typically include, but are not limited to, simple esters with alkyl carbon chains ranging from C1 to C20 with an emphasis on those molecules having large liquidous ranges and typically being liquids at ambient working conditions, typically alkyl carbon chains C2-C10 having desirably liquidous, low water solubility, and plasticization properties for nitrocellulose. Esters (R′—O—C(═O)—R—C(⊚O)—O—R′) or (R′—C(⊚O)—O—R—O—C(⊚O)—R″) can be created from a combination of linear or branched alkyl, alkenyl, or alkynyl, or phenyl polyol (—OH functionality n>2) condensed with one to n equivalents of n-alkyl, n-alkoxy, alkenyl, alkynyl, or aryl carboxylate esters or from a combination of n-alkyl or n-aryl polycarboxylic groups condensed with one to n equivalents of pendant O—R alkyl or aryl groups.
Examples of inert plasticizers include but are not limited to commonly used plasticizers, either alone or as mixtures, including, 1,6-bis(n-propyl) hexane dioate (di-n-propyl adipate), 1,6-bis(ethyl) hexane dioate (diethyl adipate), 1,6-bis(n-butyl) hexane dioate (di-n-butyl adipate), 1,2,3-tris(acetoxy)propane (triacetin), tris(ethyl)-2-hydroxypropane-1,2,3-tricarboxylate (triethyl citrate), tris(n-propyl)-2-hydroxypropane-1,2,3-tricarboxylate (tri-n-propyl citrate), tris(n-butyl)-2-hydroxypropane-1,2,3-tricarboxylate (tri-n-butyl citrate), 1,2-bis(acetoxy)-benzene (diethyl phthalate), 1,3-bis(acetoxy)-benzene (diethyl phthalate), 1,2-bis(butoxy)benzene (dibutyl phthalate), 1,3-bis(butoxy)benzene (dibutyl phthalate), and di-n-butyl-n-decane dioate (dibutyl sebacate), and similar isomers using oxalates, malonates, succinates, glutarates, and simple hydroxy carboxylic acid structures such as ethyl 2-hydroxypropanoate (ethyl levulinate). Plasticizers may also contain nitrile functional groups (R—C═N) typically having at least two or more terminal nitriles such as 1,4-dicyanobutane (adiponitrile), 1,6-dicyano-hexane (octane dinitrile) or as mixtures with the aforementioned carboxylate esters.
Plasticizers may also contain additional ether linkages such as 1,5-diacetoxy-3-oxo-pentane (diethylene glycol diacetate) and/or carbonyl (ketone) linkages such as 1,7,7-trimethyl bicyclo [2.2.1] heptan-2-one (camphor) within the carbon backbone with or without ester functionality and/or nitrile functionality to serve as a plasticizer. Similarly, simple inorganic esters may also be created using phosphorous-based plasticizers, both with n-alkoxy or n-alkyl substituted phosphate groups [O═P(OR)3] and combinations and mixtures thereof, and the like.
The thermal stabilizer can be one or more of the following compounds: 2-nitrodiphenylamine(2-NDPA), symmetrical diethyl diphenyl urea, diphenylamine, methyl ethyl diphenyl urea, resorcinol, and the like. The preferred thermal stabilizer system is based on the use of 2-NDPA widely used in solventless double-based propellants.
At least one cerium compound burning rate modifier is incorporated into the compositions such as, but not limited to, cerium (IV) or (III) oxides, oxalates, carbonates, salicylates, stannates, stearates, carbides, 1,4 dihydroxy-2-naphthoates, and combinations and mixtures thereof, and the like. In addition, the compositions can contain, by physical mixture, carbon black, processing aids such as candelia wax, and other lead-free burning rate modifiers including but not limited to bismuth, tin, and copper compounds of citrate, gallate, oxide, resorcylate, salicylate, and stannate anions.
Cerium citrate was among the first forms of cerium compounds reported to catalyze decomposition in double-based propellant formulation with no mention of the combustion catalytic effect on burning rate.
The nitrocellulose was selected from a group that likely contained at least 12.0% nitrogen and likely also contained up to 13.5% nitrogen but ranged from 11.11% nitrogen to 14.14% nitrogen. The nitrocellulose was derived from cellulose of wood, cotton linter, bacterial, or other origin.
In a detailed description, the present application relates to a method of using cerium metal complexes/compounds to modify the burning rate of solid rocket motor propellants comprising the steps of preparing a double-based propellant composition comprising an admixture of nitrocellulose, energetic plasticizer for nitrocellulose, inert plasticizer for nitrocellulose, a thermal stabilizer, and burning rate modifiers including cerium metal complexes/compounds.
In one embodiment of the above method, the cerium metal complexes/compounds are selected from the group consisting of cerium (III) salicylate, cerium (IV) oxide, cerium (III) oxalate, cerium (III) carbonate, and combinations thereof.
In another embodiment of the above method, the cerium metal complexes/compounds are combined with at least one of copper salt compounds, bismuth salt compounds and tin salt compounds.
In yet another embodiment of the above method, the cerium metal complexes/compounds are combined with carbon black.
In another embodiment of the above method, the energetic plasticizer is selected from the group consisting of nitrate esters of polyhydric alcohols, nitramines, glycidyl azide polymer (GAP) plasticizer, glycidyl azide and combinations thereof.
In yet another embodiment of the above method, the nitrate esters of polyhydric alcohols in the energetic plasticizer are selected from the group consisting of nitroglycerin (NG), butane triol trinitrate (BTTN), diglycerol tetranitrate (DGTN), diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN), trimethylolethane trinitrate (TMETN), and combinations thereof.
In another embodiment of the above method, the nitrate esters of polyhydric alcohols are selected from the group consisting of nitroglycerin (NG), butane triol trinitrate (BTTN), diglycerol tetranitrate (DGTN), diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN), trimethylolethane trinitrate (TMETN), and combinations thereof.
In still another embodiment of the method, the nitramines are selected from the group consisting of: N-Methyl-N-(2-nitroxyethyl)nitramine (MeNENA), N-Ethyl-N-(2-nitroxyethyl)nitramine (EtNENA), N-Butyl-N-(2-nitroxyethyl)nitramine (BuNENA), and combinations thereof.
In still another embodiment of the above method, the inert plasticizers comprise simple esters with alkyl carbon chains selected from the group consisting of from C1 to C20 and combinations thereof.
In an additional embodiment of the above method, the inert plasticizers comprise liquidous, carbon chains with low water solubility and plasticization for cellulose and are selected from the group consisting of from C2 to C10 and combinations thereof.
In a further embodiment of the above method, the simple esters are selected from the group consisting of (R′—O—C(⊚O)—R—C(═O)—O—R′), (R′—C(═O)—O—R—O—C(═O)—R″) and combinations thereof,
In a yet further embodiment, the simple esters are selected from the group consisting of 1) a combination of a) linear or branched alkyl, alkenyl, or alkynyl, or phenyl polyol (—OH functionality n>2) condensed with b) one to n equivalents of n-alkyl, n-alkoxy, alkenyl, alkynyl, or aryl carboxylate esters; and 2) a combination of a) n-alkyl or n-aryl polycarboxylic groups condensed with b) one to n equivalents of pendant O—R alkyl or aryl groups.
In yet another embodiment of the above method, the thermal stabilizer is selected from the group consisting of 2-nitrodiphenylamine(2-NDPA), symmetrical diethyl diphenyl urea, diphenylamine, methyl ethyl diphenyl urea, resorcinol and combinations thereof.
The present application also relates to a composition of a lead-free solid rocket motor propellant that maintains burning rate performance while reducing toxicity by utilizing cerium compounds instead of lead to reduce toxicity; the propellant comprising the following components: an admixture of nitrocellulose, energetic plasticizer for nitrocellulose, inert plasticizer for nitrocellulose, a thermal stabilizer, and burning rate modifiers including cerium metal complexes/compounds.
In an embodiment of the composition, the cerium metal complexes/compounds are selected from the group consisting of cerium (III) salicylate, cerium (IV) oxide, cerium (III) oxalate, cerium (III) carbonate, and combinations thereof.
In another embodiment of the composition, the cerium metal complexes/compounds are combined with at least one of copper salt compounds bismuth salt compounds and tin salt compounds.
In yet another embodiment of the composition, the cerium metal complexes/compounds are combined with carbon black.
In another embodiment of the composition, the energetic plasticizers selected from the group consisting of nitrate esters of polyhydric alcohols, nitramines, glycidyl azide polymer (GAP) plasticizer, glycidyl azide, and combinations thereof.
In still another embodiment of the composition, the nitrate esters of polyhydric alcohols are selected from the group consisting of as nitroglycerin (NG), butane triol trinitrate (BTTN), diglycerol tetranitrate (DGTN), diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN), trimethylolethane trinitrate (TMETN), and combinations thereof.
In yet another embodiment of the composition, the nitramines are selected from the group consisting of N-Methyl-N-(2-nitroxyethyl) nitramine (MeNENA), N-Ethyl-N-(2-nitroxyethyl) nitramine (EtNENA), N-Butyl-N-(2-nitroxyethyl) nitramine (BuNENA), and combinations thereof.
In another embodiment of the composition, the inert plasticizers comprise simple esters with alkyl carbon chains selected from the group consisting of from C1 to C20.
In an additional embodiment of the above composition, the inert plasticizers comprise liquidous, carbon chains with low water solubility and plasticization for cellulose and are selected from the group consisting of from C2 to C10 and combinations thereof.
In still another embodiment of the composition, the simple esters are selected from the group consisting of (R′—O—C(⊚O)—R—C(═O)—O—R′), (R′—C(═O)—O—R—O—C(⊚O)—R″), and combinations thereof.
In yet another embodiment of the composition, the simple esters are selected from a) a group consisting of 1) a combination of a) linear or branched alkyl, alkenyl, or alkynyl, or phenyl polyol (—OH functionality n>2) condensed with b) one to n equivalents of n-alkyl, n-alkoxy, alkenyl, alkynyl, or aryl carboxylate esters; and 2) a combination of a) n-alkyl or n-aryl polycarboxylic groups condensed with b) one to n equivalents of pendant O—R alkyl or aryl groups.
In yet another embodiment of the composition, the thermal stabilizer is selected from the group consisting of 2-nitrodiphenylamine(2-NDPA), symmetrical diethyl diphenyl urea, diphenylamine, methyl ethyl diphenyl urea, resorcinol, and combinations thereof.
While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting.
Ingredients have been combined to create a solid rocket propellant according to the present application. In a preferred embodiment, the compositions consist essentially of an intimate admixture of the following components in about the specified percentage ranges:
The inventors made propellant samples with formulations listed in Table 2 below, the samples were cut into strands and the strands were burned resulting in the
Formulations tested include a-h in Table 2. They are made of nitrocellulose, energetic plasticizer for nitrocellulose, inert plasticizer for nitrocellulose, a thermal stabilizer, and burning rate modifiers including cerium compounds.
Formulation a of Table 2 uses the burning rate modifier of cerium (III) salicylate and carbon black.
Formulation b of Table 2 uses the burning rate modifier of cerium (III) oxalate and carbon black.
Formulation c of Table 2 uses the burning rate modifier of cerium (III) salicylate and carbon black.
Formulation d of Table 2 uses the burning rate modifier of cerium (IV) oxide and carbon black.
Formulation e of Table 2 uses the burning rate modifier of cerium (III) salicylate and copper beta resorcylate.
Formulation f of Table 2 uses the burning rate modifier of cerium (III) salicylate and copper subsalicylate.
Formulation i in Table 2. The greater than additive energetic effect of cerium and copper salts exhibit a slope reduction with increased pressure from 0.45 at 1000 psi to 0.21 at 2500 psi. Relative to that of formulation i, copper salt with carbon black, the effect of cerium and copper salts exhibit an increase in burning rate.
Formulation g of Table 2 uses the burning rate modifier of cerium (III) salicylate and bismuth subsalicylate.
Formulation h of Table 2 uses the burning rate modifier of cerium (III) salicylate and bismuth stannate.
Formulation h of Table 2 uses the burning rate modifier of cerium (III) salicylate and bismuth stannate.
