US2774214A - Rocket propulsion method - Google Patents

Description

Dec. 18 1956 F. J. MALINA ETA ROCKET PROPULSION METHOD Original Filed May 8, 1945 OXIDIZER FUEL INERT GAS IN VEN TOR. JOHN A. PARSONS FRANK J. MALI/VA ATTORNEY ROCKET PROPULSION IVIETHOD Frank J. Malina and John W. Parsons, Pasadena, assignors to Aerojet-General Corporation, Cincinnati,

Ohio, a corporation of Ohio Application September 1, 1950, Serial No. 182,742, which is a division of application Serial No. 486,236, May 8, 1943, now Patent No. 2,573,471, dated October 30, 1951. Divided and this application February 8, 1954, Serial No. 412,196

3 Claims. (Cl. 60-354) Our invention relates to jet propulsion and more particularly to propellants which are useful in connection therewith. This is a division of my copending application Serial No. 182,742, filed September 1, 1950, now Patent No. 2,693,077 issued November 2, 1954, as a division of application Serial No. 486,236, filed May 8, 1943, now Patent No. 2,573,471, issued October 30, 1951.

While our invention is capable of use in connection with the propulsion of a wide variety of different devices and vehicles, since it finds particular utility in the propulsion of aircraft, its advantages are described with relation to such use, it being understood that our invention is, however, not limited to such use.

Prior to our invention special means were always required to ignite the propellants. For example, when liquid oxygen is used as an oxidizer and gasoline is used as a fuel, some auxiliary ignition means must always be provided to initiate combustion of the propellants.

This is objectionable because it requires either a spark plug or other ignitor or means for heating the Walls of the combustion chamber above the ignition point of the propellant mixture making this system complex and dependent upon the operation of such ignition system.

While spontaneous combustion is obtained with our preferred combinations of propellants which is especially effective when operating in accordance with our preferred method it will be understood that the propellants we have discovered offer advantages even when operating under other conditions.

The present invention relates to fuels, and oxidizers and their combination as propellants and their method of injection into a jet motor. Among the objects of our invention are: to provide more eflicient and effective propellants for jet propulsion systems; to provide an oxidizing agent which is easily combustible with a suitable fuel and which has a large amount of oxygen available for burning a fuel; to provide propellants, that is, fuels and oxidizers, which are spontaneously combustible; to provide a method for utilizing such propellants to give smooth combustion and to eliminate danger of explosion; to obviate the difiiculties attendant upon the use of liquified gases; to eliminate the need of an auxiliary ignition system to ignite the propellants.

Oxidizers As a result of a thorough investigation of the various oxidizing agents which may be used as propellants we prefer to employ nitric acid. Since water tends to retard combustion of the acid with any fuel, the nitric acid should be substantially free of water. Thus, white fuming nitric acid, which normally contains less than about 2% of water by weight, is to be preferred to weaker solutions of nitric acid. However, we have found that more dilute solutions of nitric acid may be utilized provided that nitrogen dioxide is dissolved in the nitric acid; which is a way of increasing the concentration of an otherwise more dilute solution. Prefer- Patented Dec. 18, 1956 ably the nitric acid should contain at least about 5% N02 but preferably at least about 15 to 20% N02. Such a solution of nitrogen dioxide is known as red fuming nitric acid and almost all red fuming nitric acid which is commercially available in this country contains between about 5% and 20% nitrogen dioxide by weight and less than about 5% water by weight. Specifications for nitric acid, obtainable commercially as red fuming nitric acid, are as follows:

Chemical composition:

Specifications for nitric acid, obtainable commercially as white fuming nitric acid, are as follows:

Chemical composition:

Nitric acid 97.5% by wt. min. Water 2.0% by wt. max. N02 content 0.5% by wt. max. Physical properties: Density 1.46 min-41.52 max. at

68 F. Melting point -45 F. Color, etc Straw yellow to water white;

fumes vigorously when exposed to air.

The term white fuming nitric acid as used herein means a nitric acid containing a maximum of about 2% water by weight.

The term red fuming nitric acid as used herein means a nitric acid containing at least about 5% N02 and a maximum of about 5% water, by weight.

Nitric acid of all types containing at least HNOs is useful as an oxidizer. We have also found that liquid nitrogen dioxide is a very satisfactory oxidizer.

To eliminate the requirement for providing the jet motor with special igniting means, we employ nitric acid, and preferably red 'fuming nitric acid, substantially free of water, as an oxidizer.

Fuels We have discovered a family of fuels which are spontaneous'ly combustible with the oxidizing agents hereinabove mentioned and which are satisfactory for jet propulsion provided that the propellants are supplied to the combustion chamber under suitable operating conditions. These operating conditions are discussed more in detail hereinbelow.

We have found that the four groups of compounds listed below may be utilized as fuels. These groups are listed in the order of their efiectiveness.

Group I.Liquid organic compounds containing at least one amine radical, such as,

A. Aniline, orthotoluidine, and methylamine.

B. Liquid hydrocarbons, containing large percentages of such amine substituted organic compounds.

Group II.Highly unsaturated hydrocarbons: Liquid hydrocarbons of the acetylene type and containing a large fraction of unsaturated (double and triple) carbon bonds, or both, for example, divinyl acetylene, dipropargyl, and prop-argyl alcohol. 7

Group III.-Liquidsubstances containing the elements having the properties of lithium (Li), beryllium (Be), boron (B), aluminum (A1), magnesium (Mg), phosphorus (P), potassium ('K), and. sodium (Na). With the exception of phosphorus all of the foregoing elements. are. particularly useful in fuels because they generate large amounts of heat during combustion, and phosphorus is particularly useful because it has a low ignition temperature.

A. Liquid hydrides of those elements.

B. Liquid organo-metallic compounds containing one or more of such elements.

C. Liquid fuels containing one or more such. elements.

D. Liquid fuels containing one or more such elemerits in suspension.

Group IV.-Organic compounds having the properties of -While aniline is toxic it has the great advantage of being relatively inexpensive, even though more expensive than gasoline, and of being commercially available in large quantities.

Method of operation The above mentioned oxidizers and fuels may be used i together as pairs of spontaneously combustible propellants zit-atmospheric temperature and pressure. However, if desired these oxidizers and fuels may be used with other fuels (such as gasoline) or other oxidizers (such as liquid oxygen) respectively.

So far as we know we are the first to achieve spontaneous combustion in jet propulsion systems at the temperature and pressure of the medium surrounding the jet motor and while other fuels and oxidizers might be utilized to accomplish such spontaneous combustion we prefer to use the [fuels and oxidizers hereinbefore mentioned.

Certain difficulties are encountered when utilizing these propellants for propulsion. Unless the propellants are supplied to the jet motor under the proper conditions the motor is liable to fail completely, to pulsate in its operation, or to explode, even though the propellants are supplied at uniform rates.

These difliculties may be eliminated and certainty and smoothnes of operation secured by so relating the rates of injection of fuel and oxidizer to the size of the jet chamber and the inherent ignition properties of the mixture that explosion of the combustible mixture is avoided during the initial combustion, and subsequent inject-ion occurs at rates conducive to the combustion of the continuously supplied propellants so as to avoid the accumulation in the jet chamber of any substantial amount of the unburned propellants. To achieve this result, we initially inject propellants into the combustion chamber at rates such that the amount of propellants injected prior to the initiation of combustion is lessthan about 20% of the volume of the combustion chamber. After combustion has been initiated, the propellants may be injected at a greater rate than they are injected initially inasmuch as the time interval between their 5 injection and combustion is reduced because of the higher temperature and pressure of the mixture resulting The fuels and oxidizers hereinbefore described are advantageously employed in the propulsion of an aircraft by providing the fuel and oxidizer in separate-containers 11 and 12 respectively connected in any suitable manner as by pipes 13 and 14 to a jet or combustion Throttle valves 16 and 17 energized by elec chamber. trical circuits 18 and 19 are provided in said pipes to control the rates of supply of the fuel and oxidizer re- 7 20 spectively to the combustion chamber 15. A receptacle 20 is connected by a conduit 21 having a pressure regulator 22 therein to the receptacles 11 and 12 and is provided with a gas under pressure, preferably a gas inert with respect to either propellant. Preferably the 25 container for the fuel and the container for the oxidizer.

are connected to a source of pressure adapted to force the contents of such-containers into the jet or combustion chamber at controlled rates determined by the degree of opening of the valves in said pipes.

plates so relating the rates of'injection of the oxidizer and of the fuel'to the combustion or jet chamber to theirinherent combustion properties and the size and temperature of the chamber that smooth non-explosive combustion occurs initially and throughout the entire operation while providing the desired quantity of propulsive power.

when the combustion chamber is initially at atmospheric temperature, or at the temperature of any other medium 40 in which the motor is to operate, as we are able to achieve combustion initially without auxiliary ignition or preheating of the chamber or the propellants.

If the propellants are supplied at such initial rates,

then, when the propellants are initially injected into the jet motor, the initially burned propellants soon fil-l the .combustion chamber with high temperature gases and vapors which heat the incoming propellants thereby vaporizing them and reducing the ignition time lag.

Then the subsequently injected propellants burn spontaneously without any substantial accumulation of propellants in the liquid phase.

As an example, applied to a combustion chamber having a length of about 10 inches and a cross sectional area of about 7 square inches, highly concentrated nitric add and aniline operate very satisfactorily when they are .injected into the'combustion chamber initially and prior to combustion at the rates of 3.6 lbs. per second and 2.4

'lbs. per second respectively.

/ While these propellants and method of use and the apparatus for their use in propelling aircraft or other devices, which are hereinbefore described, are fully capable of providing the advantages primarily stated, it will be recognized by those skilled in the art that various modifications and alterations may be made therein while still providing such advantages, and our invention is therefore tobe understood as not limited to the specific i-embodiments hereinbefore described but as including all modifications. and variations thereof coming within the scope of the claims which follow.

We claim as our invention:

.1. The method of producing thrust which comprises ejecting, from .a reaction chamber, the gaseous products produced by the spontaneous combustion of an oxidizer selected from the group consisting of red fuming nitric 75" acid, white fuming nitric acid and nitrogen dioxide; and

The practice of the method of our invention contem- 7 Our invention is particularly advantageous a heterocyclic nitrogen compound selected from the group consisting of pyrrole and pyridine.

2. The method of producing thrust which comprises ejecting, from a reaction chamber, the gaseous products produced by the spontaneous combustion of an oxidizer 5 References Cited in the file of this patent UNITED STATES PATENTS 1,506,323 ONeill Aug. 26, 1924 FOREIGN PATENTS 476,227 Great Britain Dec. 3, 1937 OTHER REFERENCES Finnemore: Essential Oils, E. Benn Limited, London Hackhs Chemical Dictionary. Philadelphia, 3rd ed., pp. 837, 876.

The Blakiston Co.,

Claims (1)

1. THE METHOD OF PRODUCING THURST WHICH COMPRISES EJECTING, FROM A REACTION CHAMBER, THE GASEOUS PRODUCTS PRODUCED BY THE SPONTANEOUS COMBUSTION OF AN OXIDIZER SELECTED FROM THE GROUP CONSISTING OF RED FUMING NITRIC ACID, WHITE FUMING NITRIC ACID AND NITROGEN DIOXIDE; AND

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