Reduced toxicity hypergolic bipropellant fuels

Details Reduced toxicity hypergolic bipropellant fuels Reduced toxicity hypergolic bipropellant fuels

2002-04-12

2004-02-24

Carone, Michael J. (Department: 3641)

Explosive and thermic compositions or charges

Containing liquefied gaseous fuel or liquefied oxygen...

C149S108600, C060S211000, C060S212000

Reexamination Certificate

active

06695938

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to reduced toxicity hypergolic bipropellants and, more particularly, to the development of new rocket fuels which are hypergolic with 70-100 weight % hydrogen peroxide. These novel bipropellant combinations are less toxic than conventional hydrazine based bipropellant systems.
2. Description of Related Art
Innovative propellants have long been used by the United States Navy for power generation, propulsion and ordnance. Prime considerations in the post World War II era have been specific impulse, volumetric energy content, surge/mobilization readiness and shipboard safety. While these parameters are still important, toxicity, personnel endangerment, environmental concerns, commercial transitions and cost have been added to the list of considerations to be taken into account.
Traditional propulsion systems requiring storable hypergolic bipropellants have used a hydrazine based fuel, such as monomethyl hydrazine, combined with nitrogen tetroxide or inhibited red fuming nitric acid. Storable hypergolic bipropellant systems using interhalogen oxidizers have also been developed and used. However, these oxidizers are highly toxic to humans and extremely reactive. As a result, these oxidizers are difficult to use and dangerous in many environments. Further, these bipropellants pose significant environmental problems and have high associated costs. When a mission requires the use of a storable hypergolic bipropellant, the choice has traditionally been limited to a hydrazine based fuel used in conjunction with N
2
O
4
or IRFNA. These bipropellants deliver excellent performance, but they are highly reactive, toxic and/or carcinogenic substances. It is very difficult and expensive to implement these bipropellants into propulsion systems, which are able to satisfy stringent military safety requirements.
In the past, various polar and nonpolar fuels have been used with hydrogen peroxide to form usable bipropellants. However, except for a potassium cuprocyanide catalyzed hydrazine hydrate fuel discovered in the 1940's, these bipropellants were not hypergolic and required an ignition system. These non-hypergolic bipropellants are not well-suited for applications requiring pulse mode operation and/or multiple restarts. Thus, traditional hydrogen peroxide based bipropellants could not be considered as viable replacements for the more toxic hypergolic bipropellants. The potassium cuprocyanide catalyzed hydrazine hydrate fuel yielded poor performance compared to nitrogen tetroxide/monomethyl hydrazine and is also a highly toxic fuel. Thus, it has never been a serious fuel candidate.
During the last decade the, the propulsion community launched a significant research effort to develop a new, less toxic, alternative storable hypergolic bipropellants for divert and attitude control systems (DACS) that would meet shipboard requirements. Rocket grade (90-99%) hydrogen peroxide (RGHP) emerged as the liquid oxidizer of choice. The problem was a general lack of hypergolic fuels that could be used successfully with the RGHP. The first significant breakthrough was the development of a manganese acetate catalyzed methanol fuel sufficiently hypergolic to yield successful rocket engine firings.
Please refer to U.S. Pat. No. 5,932,837 issued Aug. 3, 1999 to Rusek, et al. The formulations of the U.S. Pat. No. 5,932,837 provide a reduced toxicity hypergolic miscible fuel, which can be used in combination with a rocket grade hydrogen peroxide to form a reduced toxicity miscible bipropellant with rapid ignition capabilities. In addition, the formulations of the U.S. Pat. No. 5,932,837 provide a reduced toxicity hypergolic miscible fuel containing a dissolved manganese compound, which forms a catalyst in solution. This new bipropellant is especially applicable for use in divert/attitude control systems, as well as general propulsion applications.
The concept for the formulations of the U.S. Pat. No. 5,932,837 was derived from earlier research involving catalyst-doped JP fuels, specifically JP-10. These fuels were formulated by dissolving a manganese containing organic compound in JP-10 fuel. The manganese catalyzed JP-10 fuels would initiate decomposition of the RGHP when sprayed together in a rocket motor injector, but satisfactory hypergolic ignitions were not obtained. The nonpolarity of the JP-10 and the polarity of RGHP did not enable mixing of the two propellants in a manner intimate enough or fast enough to attain the degree of hypergolicity required. In addition, theoretical energy calculations of the combination of the fuels and RGHP resulted in an optimum oxidizer to fuel ratio in the range 5:1 to 7:1. The next step was to find a catalytically active manganese, or other transition metal compound, which was soluble in a lower molecular weight polar solvent that could also serve as the fuel. The result was a hypergolic fuel composition consisting of manganese acetate tetrahydrate dissolved in methanol.
Unfortunately, the formulations of the U.S. Pat. No. 5,932,837 exhibited poor aging/storage characteristics. In time, irreversible degradation occurred in the fuel making it unacceptable for long-term tank storage. The formation of the precipitate is accelerated by heat and by the presence of water and oxygen. This is a fatal flaw for the hypergolic methanol/manganese acetate fuel described in the U.S. Pat. No. 5,932,837.
U.S. patent application Ser. No. 09/510,993, incorporated herein by reference, provides a reduced toxicity hypergolic bipropellant consisting of a modified methanol/manganese acetate fuel and rocket grade hydrogen peroxide oxidizer. The modified fuel resists the formation of precipitate over time when exposed to upper limit thermal environments. This is accomplished by buffering the pH of the fuel with acetic acid and alkali acetate and the addition of a polar amide species to increase the polarity of the solvent. Although the formulations of the Ser. No. 09/510,993 application resist the formation of precipitate better than the formulations of the U.S. Pat. No. 5,932,837, the resultant fuels do not have sufficient stability to satisfy Navy requirements. Therefore, a need in the art exists for rocket fuels with superior performance and acceptable long term tank storage capability
SUMMARY OF THE INVENTION
A preferred embodiment of the present invention provides a hypergolic fuel, either a reactive fuel or a catalytic fuel, which is used in combination with rocket grade hydrogen peroxide oxidizer to produce a reduced toxicity hypergolic bipropellant. The rocket grade hydrogen peroxide oxidizer comprises about 70 weight % to about 99 weight % of hydrogen peroxide with the balance water. The preferred hydrogen peroxide concentration is about 94 weight % to about 99 weight %. The reactive fuel is comprised of about 6 weight % to 10 weight % reducing agent dissolved in a fuel, which is also a solvent for the reducing agent. The resultant reactive fuel is intrinsically reactive with the rocket grade hydrogen peroxide oxidizer. The catalytic fuel is comprised of about 6 weight % to about 10 weight % catalytic agent dissolved in a fuel, which also serves as a solvent. The resultant catalytic fuel stimulates the decomposition of the rocket grade hydrogen peroxide oxidizer upon contact.
One object of a preferred embodiment of the present invention is to provide a reduced toxicity hypergolic fuel, which can be used in combination with rocket grade hydrogen peroxide to form a reduced toxicity hypergolic bipropellant with rapid ignition capabilities.
Another object of a preferred embodiment of the invention is to provide a reduced toxicity hypergolic fuel, which remains stable when subjected to long-term storage at maximum and minimum service

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