Explosive and thermic compositions or charges – Structure or arrangement of component or product – Solid particles dispersed in solid solution or matrix
Utility Patent
1999-09-02
2001-01-02
Jordon, Charles T. (Department: 3641)
Explosive and thermic compositions or charges
Structure or arrangement of component or product
Solid particles dispersed in solid solution or matrix
C149S019920
Utility Patent
active
06168677
ABSTRACT:
DEDICATORY CLAUSE
The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalties thereon.
BACKGROUND OF INVENTION
The U.S. Army Aviation and Missile Command at Redstone Arsenal has long been interested in the removal of environmental hazards in its tactical missile propellants. Of particular interest is the removal of lead from the exhaust products of all tactical missiles. Lead compounds are currently the major ballistic modifiers used in the traditional minimum signature propellants for tactical missile applications. Lead is currently found in nearly all tactical missiles where minimum signature is required. The toxicity of lead has been well documented and is the incentive behind the Army's desire to remove it from missile systems. However, this task has proven to be difficult, especially when minimum signature and ballistic integrity of the propellant must be maintained. Typically, when an ingredient is found to control ballistic properties, a loss in minimum signature properties has resulted also. This information was disclosed in an earlier presentation by L. C Warren, “Burning Rate Catalysis of Ammonium Nitrate Propellants”, presented at the Tri-service propellant Formulators Conference, Edward AFB, August 1990. A later presentation by L. C. Warren et al., “High Performance Ammonium Nitrate Propellants for Next Generation Survivable Propulsion Systems”, was presented at 1995 JANNAF PDCS, JPL, Pasadena, Calif. More detailed information is presented in the Information Disclosure Citation filed with this application.
Two bismuth compounds, bismuth salicylate and bismuth citrate, have been evaluated as lead alternatives in a propellant formulation similar in theoretical performance properties of currently fielded propulsion systems. Industrially, bismuth is considered the less toxic of the heavy metals. The MSDS for bismuth compounds, bismuth salicylate and bismuth citrate has been furnished by Shepherd Chemical Company. Some forms of bismuth are less toxic than others. One such compound is bismuth salicylate. Bismuth salicylate is used in some medicines and is the active ingredient in the non-prescription medicine Pepto Bismol®, an oral over the counter medication used for relieving upset stomach problems. Both bismuth salicylate and bismuth citrate are readily available and are inexpensive.
An object of this invention is to provide a propellant formulation with minimum signature and ballistic integrity of high performance.
Another object of this invention is to provide a lead free propellant formulation and a nitroglycerin free propellant formulation, which is environmentally more attractive based on current EPA requirements.
SUMMARY OF INVENTION
A general description of the bismuth compounds used in the evaluations of this invention is set forth in Table A below.
TABLE A
BISMUTH COMPOUNDS EVALUATED
Formula
Supplier
Bismuth Compound
wt. (g)
Density (g/cc)
The Shepherd Chemical
Bismuth Salicylate
362
2.36
Company
C
7
H
5
BiO
4
SIGMA Chemical
Bismuth Citrate
398
3.46
Company
C
6
H
5
O
7
Bi
The baseline propellant formulation of this invention is outlined in Table B below.
TABLE B
BASELINE PROPELLANT FORMULATION
Ingredient
%
ORP-2
7.00
BTTN
20.17
TMETN
8.64
CARBON
0.50
RDX, 17&mgr;
34.36
RDX, 4&mgr;
6.24
HMX, 2.75&mgr;
17.40
ZrC, 7&mgr;
1.50
MNA
0.50
Bi COMPOUND
2.00
N100
1.69
The propellant binder system consists of the energetic nitramine prepolymer(s) ORP-2 or 9DT-NIDA, plasticized with the nitrate esters BTTN and TMETN, and cured with N 100. Without nitroglycerin, an energetic polymer such as ORP-2 or 9DT-NIDA, is needed to enhance propellant performance impulse to greater than 245 seconds. The elimination of NG is proven to be more beneficial for immediate safety considerations than the elimination of lead. ORP-2 and 9DT-NIDA also enhance propellant burning rates and mechanical properties, two great improvement needs for minimum signature propellants.
Initial evaluations centered on determining the effectiveness of various bismuth additives as the sole ballistic modifier (without zirconium carbide stabilizer) in propellant formulations. By themselves neither lead salicylate nor bismuth salicylate will affect significantly minimum signature propellant burning rate properties. However, it was discovered that the addition of zirconium carbide with either ingredient present, resulted in significant enhancement in propellant ballistic properties, in particular lowering propellant burning rate pressure exponent. Bismuth salicylate was equally as effective as lead salicylate or lead citrate in the presence of zirconium carbide for increasing propellant burning rates and reducing burning rate pressure exponent values. Bismuth citrate appeared to be only slightly less efficient than the bismuth salicylate. This could be because the concentration of bismuth in the citrate derivative is less than in the salicylate.
During these evaluations an unexpected influence by carbon on the propellant ballistic properties was observed. In this work two different carbons were used, Thermax and Sterling R. The particle size of the carbon black played a significant role in enhancing propellant burning rates and reducing burning rate exponents. Superior ballistic properties were achieved with Sterling R carbon as opposed to Thermax carbon. The average particle sizes of the Thermax and Sterling R carbons are 270 and 60 nanometers, respectively. A similar phenomenon concerning average particle size of the bismuth compounds was observed. When the average particle size of the bismuth compounds was less than 5 microns, the ballistic properties adequate for tactical missile applications were achieved.
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Larry C. Warren et al. “High Performance Ammonium Nitrate Propellants for Next Generation Survivable Propulsion Systems”, Apr. 1995, Presented at : Jannaf Propulsion Development and Charization Subcommittee Meeting.
Larry C. Warren et al. “High Performance Ammonium Nitrate Propellants for Next Generation Survivable Propulsion Systems”, 1995.
Bush Freddie M.
Jordon Charles T.
S{acute over (a)}nchez Glenda L.
The United States of America as represented by the Secretary of
Tischer Arthur H.
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