US3613371A - Hypergolic bipropellant propulsion process using boron components - Google Patents

Abstract

1. THE METHOD OF DEVELOPING A THRUST WHICH COMPRISES REACTING A BORANE COMPONENT SELECTED FORM THE GROUP CONSISTING OF BORON HYDRIDES, HYDROCARBON SUBSTITUTED BORON HYDRIDES, AND MIXTURES THEREOF, AND A HYDRAZINE COMPONENT SELECTED FROM THE GROUP CONSISTING OF HYDRAZINE, HYDROCARBON SUBSTITUTED HYDRAZINES, AND MIXTURES THEREOF, IN A CHAMBER WHICH IS CLOSED EXCEPT FOR A CONSTRICTED EXHAUST NOZZLE, AND EXPELLING THE RESULTANT REACTION PRODUCTS THROUGH SAID NOZZLE TO PRODUCE A REACTION THRUST ON SAID CHAMBER.

Description

United States Patent @fiee 3,613,371 Patented Oct. 19, 1971 3,613,371 HYPERGOLIC BIPROPELLANT PROPULSION PROCESS USING BORON COMPONENTS Lawrence J. Edwards, Zelienople, Pa, assignor to Callery Chemical Company, Pittsburgh, Pa. N Drawing. Filed Feb. 4, 1959, Ser. No. 791,231 Int. Cl. C06d 00, 5/06 U.S. Cl. 60214 9 Claims This invention relates to reaction engines and more particularly to new bipropellants useful in connection with rockets or rocket engines.

The rockets or rocket engine is a self-contained reaction engine in that it does not require the use of air to effect an energy-producing chemical reaction. Bipropellants consist of two separated components which are mixed together at the time of use in a combustion chamber where they are reacted to produce a jet thrust as the products of the reaction exhaust through a nozzle at the end of the combustion chamber. These bi-component propellants are commonly called bipropellants. Prior bipropellants have used fuel and oxidizer components. The fuels heretofore generally used or considered for use include alcohols, hydrocarbons such as JP-4, aniline, nitrogen hydrides such as hydrazine, and boron hydrides and their derivatives such as diborane and pentaborane. The oxidizers generally used include nitric acid and nitrogen oxides, hydrogen peroxide, and liquid oxygen. Liquid fluorine has also been considered for use as an oxidizer. Energy is produced from the combustion or oxidation of the fuel by the oxidizer.

The thrust-producing capacity or performance rating of a particular propellant system is commonly referred to as the specific impulse, which is usually expressed as pounds of thrust available per pound of propellant per second. The reported specific impulses for propellants currently in use range from about 150 to 280 lb. sec./lb. Those factors inherent in the propulsion reaction that significantly effect the specific impulse are the reaction temperature and the molecular weight of the reactant products. Specific impulse is directly proportional to the square root of the reaction temperature and inversely proportional to the square root of the molecular weight of the reaction products. Another major factor governing specific impulse is the ratio of chamber pressure to exit pressure; however, this is adjusted by variations in the configuration of the exhaust nozzle and may be adjusted independntly of propellant properties.

There are certain limitations of the performance of conventional fuel-oxidizer bipropellants which are inherent in the nature of the energy-producing reactions. The molecular weight of the reaction products is relatively high since the production of energy depends on the combination of comparatively heavy elements of the oxidizer with elements of the fuel, e.g. the combination of hydrogen and oxygen to produce H O or the production of oxides of carbon. Also, the oxidation products tend to dissociate at the high combustion temperature involved and a substantial amount of the potential available energy is lost by this dissociation, e.g. the dissociation of CO to C0. Although the specific impulse is increased with an increase in combustion temperature, the construction of combustion chambers for very high temperature propellants is expensive or impracticable because of the lack of suitable materials of construction. It is, therefore, especially desirable to have available propellants that develop a high specific impulse at moderate temperatures.

It is an object of this invention to provide new bipropellants for use in rockets or rocket engines that produce a high specific impulse. Another object is to provide a bipropellant that produces a high specific impulse at a moderate reaction temperature. A further object is to provide a bipropellant system that does not require a conventional oxidizer component.

Using the borane-hydrazine propellants of this invention, the energy-producing reaction is a highly exothermic reaction between a boron hydride or hydrocarbon derivative of a boron hydride and hydrazine or a hydrocarbon derivative of hydrazine. For example, the reaction between pentaborane(9) and hydrazine proceeds accordlng to with a release of 4250 B.t.u. per pound of bipropellant.

The borane-hydrazine bipropellant reaction is a high energy reaction in comparison with conventional fueloxidizer bipropellants; for example, the hydrazine-oxygen reaction releases 3600 B.t.u./lb. Further, the new bipropellants produce large volumes of hydrogen (with a molecular weight of 2), in contrast to the consumption or reaction of hydrogen in conventional fuel-oxidizer bipropellants. For this reason the effective molecular weight of the reaction products is lower than that obtainable from conventional bipropellants.

The reaction temperature of the new borane-hydrazine bipropellants is comparable to combustion temperature of those conventional bipropellants which can develop only a moderately high specific impulse. For example, the reaction temperature of the pentaborane(9)-hydrazine bipropellant is about 4600 R, which is approximately the same as the combustion temperature of ethyl alcoholhydrogen peroxide bipropellant. Because of the low effec tive molecular weight of the reaction products, a high specific impulse is obtained at the desirable moderate temperature. Further, since the reaction products do not dis sociate to any significant amount there isv little loss of the potential available chemical energy. For example, the specific impulse of the pentaborane(9)-hydrazine bipropellant at a combustion chamber pressure of 1000 p.s.i.a. and an exit pressure of 1 atmosphere is about 338 lb. sec./ 1b., and at a chamber pressure of 300 p.s.i.a. and exit pressure of 1 atmosphere the specific impulse is about 297. In comparison, the hydrazine-oxygen bipropellant has a calculated specific impulse of 263 lb. sec./lb. at a chamber pressure of 300 p.s.i.a.

Specific impulses for some proposed fuel-oxidizer propellants have previously been calculated which approach the specific impulse obtainable from the hydrazine-borane bipropellants; however, the high specific impulse depends primarily on an extremely high combustion temperature. For example, the hydrazine-fluorine propellant has a calculated specific impulse of 316 at a chamber pressure of 500 p.s.i.a., but the combustion temperature is 7940" F. It is apparent that such high temperature creates a difficult problem of engineering design and materials of construction of the combustion chamber which are avoided with the moderate reaction temperature of the new borane'- hydrazine bipropellants.

The stable liquid boron hydrides, such as pentaborane(9) and hexaborane(l0), are preferred borane components of the propellant because they are easily handled, stored, and pumped. Other boron hydrides, such as diborane, tetraborane, and decaborane, may be used as propellant components in generally the same manner although more sophisticated storage or metering systems may be required. For example, decaborane (M.P. 99.7 C.) is a solid at ambient conditions and it may be injected as a slurry in another borane or in solution in a hydrocarbon; preferably it is melted and injected as any other liquid fuel.

Hydrocarbon substituted boron hydride may be as well as the unsubstituted boron hydrides. Suitable materials include lower alkyldiboranes such as mono-, di-, tri-, and tetra-, methyldiboranes, and ethyldiboranes; alkyl substituted higher boron hydride such as alkyltetraboranes, alkylpentaboranes, alkyl hexaboranes, and alkyldecaboranes such as methyl substituted decaboranes; borohydrocarbons such as the reaction product obtained from reaction of acetylene and boranes; other similar borohydrocarbons; and mixtures thereof. Hydrocarbon substituted higher boron hydrides are made, for example, by reacting a halogenated hydrocarbon with the boron hydride in the presence of an aluminum halide, as disclosed in the copending, coassigned application of Wunz and Stang, Ser. No. 756,058, filed Aug. 14, 1958. Although the specific impulse obtained from the hydrocarbon substituted boron hydrides is somewhat less than that obtained from unsubstituted boron hydrides, they may be preferable for certain applications because of their stability, resistance to hydrolysis, low vapor pressure, and lower toxicity.

Hydrazine, N H is the preferred hydrazine component of the propellant since its use results in the highest specific impulse with any borane component, but hydrocarbon substituted hydrazine may be used if desired, e.g. lower alkyl hydrazines such as methyl hydrazine, sym-dimethyl hydrazine, unsym-dimethylhydrazine, trimethyhydrazine, ethylhydrazine, diethylhydrazines, and triethylhydrazine.

When hydrocaron substituted propellant components are used, the reaction products include boron nitride, boron carbide, carbon, hydrogen, and small amounts of dissociation products such as boron and nitrogen.

The borane-hydrazine bipropellants of the invention may be used in the same manner and in the same type of engine as is used with conventional fuel-oxidizer bipropellants. The hydrazine component and the borane component are contained in separate tanks from which they are fed to the combustion chamber. In order to ob tain the best utilization of the available stored chemical energy they are preferrably fed in stoichiometric proportions. The bipropellants are pumped into the chamber; however, they may be injected by pressurizing the tanks with an inert gas. Impingement injectors, spray injectors, non-impinging injectors, and other types of injectors may be used. The unsubstituted hydrazine-unsubstituted boron hydride propellants are hypergolic at room temperature and atmospheric pressure so auxiliary ignition or preheating of the combustion chamber is not normally required. If the combustion chamber is at very low temperature, it may be preheated before beginning injection of the propellant to prevent an accumulation of unreacted propellant which may then spontaneously ignite and cause an explosion in the chamber. The hydrocarbon substituted propellant components do not reliably ignite spontaneously at ambient conditions, so ignition by spark plug, hot wire, or other conventional methods should be used. Ignition may be conveniently accomplished by introducing small amounts of oxygen, hydrogen peroxide, or other oxidizer into the combustion chamber. The reactions, however, are self-sustaining at the high temperature of the combustion chamber under operating conditions, so only an initial ignition is required.

According to the provisions of the patent statutes, I have explained the principle and mode of practicing my invention and have described what I now consider to be its best embodiments. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. The method of developing a thrust which comprises reacting a borane component selected from the group consisting of boron hydrides, hydrocarbon substituted boron hydrides, and mixtures thereof, and a hydrazine component selected from the group consisting of hydrazine, hydrocarbon substituted hydrazines, and mixtures thereof, in a chamber which is closed except for a constricted exhaust nozzle, and expelling the resultant reaction products through said nozzle to produce a reaction thrust on said chamber.

2. A method according to claim 1 in which the hydrazine component is hydrazine.

3. A method according to claim 1 in which the borane component is a boron hydride.

4. A method according to claim 2 in which the borane component is diborane.

5. A method according to claim 2 in which the borane component is pentaborane(9).

6. A method according to claim 2 in which the borane component is decaborane.

7. A method according to claim 2 in which the borane component is a lower alkyl substituted higher boron hydride.

8. A method according to claim 7 in which the borane component is a methyl substituted decaborane.

9. A method of operating a jet propelled device which comprises separately supplying to the reaction chamber of the device hydrazine and decaborane to produce thrust.

References Cited Clark, Ordnance, vol. 36, pp. 661-3 (1952), Penner, J. Chem. Ed., pp. 379 (January 1952).

BENJAMIN R. PADGETT, Primary Examiner U.S. Cl. X.R.

Claims (1)

1. THE METHOD OF DEVELOPING A THRUST WHICH COMPRISES REACTING A BORANE COMPONENT SELECTED FORM THE GROUP CONSISTING OF BORON HYDRIDES, HYDROCARBON SUBSTITUTED BORON HYDRIDES, AND MIXTURES THEREOF, AND A HYDRAZINE COMPONENT SELECTED FROM THE GROUP CONSISTING OF HYDRAZINE, HYDROCARBON SUBSTITUTED HYDRAZINES, AND MIXTURES THEREOF, IN A CHAMBER WHICH IS CLOSED EXCEPT FOR A CONSTRICTED EXHAUST NOZZLE, AND EXPELLING THE RESULTANT REACTION PRODUCTS THROUGH SAID NOZZLE TO PRODUCE A REACTION THRUST ON SAID CHAMBER.