US3136119A - Fluid-solid propulsion unit and method of producing gaseous propellant - Google Patents

Description

June 9, 1964 W. H. AVERY 3,136,119

FLUID-SOLID PROPULSION UNIT AND METHOD OF f PRODUCING GASEOUS PROPELLANT 2 sheets-sneu 1 Filed Sept. l2, 1952 I j INVENTOR ML MM H. l/Ef/ ATTORNEY United States Patent 3,136,119 FLUID-SOLID PRQPULSION UNIT AND METHOD F PRODUCING GASEGUS PROPELLANT William H. Avery, Silver Spring, Md., assignor to Research Corporation, New York, NX., a corporation of New York Filed Sept. 12, 1952, Ser. No. 309,239 16 Claims. (Cl. Gil-35.4)

This invention relates to a rocket propulsion system and particularly to a rocket propulsion system utilizing a liquid fuel and a solid oxidizer.

Rocket propulsion systems are finding extensive application as assist-take-off devices, boosters for missiles, and projectiles. The several systems previously used may be classified into two basic types in accordance with the physical state of the fuel and oxidizer employed, i.e., liquid propellant or solid propellant. A third type, a gaseous system, is obviously undesirable from the standpoint of the very large space requirements in order to provide an adequate fuel supply.

The liquid propellant systems have advantages in controllability, low cost, and high performance, but all liquid oxidizing agents present severe storage and handling problems. For example, some liquid oxidizers, such as HNO3 H2O2 are corrosive, unstable and toxic while others, such as N204, are toxic and volatile and others, such as a liquid O2, require insulation and refrigeration. In addition, conventional liquid systems require complex feed mechanisms and precise control to eliminate the hazard of explosion. The solid propellant systems are simpler and may be more reliable than the liquid propellant systems, but they are explosive, non-controllable and expensive.

Several systems employing fuels and oxidants, respectively in different physical states, had been developed.

' One such system comprised the reaction of aluminum powder suspended in a liquid hydrocarbon with liquid oxygen and involved the attendant disadvantages of the liquid type systems outlined above. Another system proposed the use of liquid nitrous oxide for burning solid carbon and still another system proposed the burning of a solid plastic, e.g., polythene fuel, with a liquid oxidizer, e.g., hydrogen peroxide. The latter two systems also involved the problem of storing and handling a highly corrosive, unstable, or toxic liquid.

Solid oxidizers were developed to provide auxiliary combustion-supporting agents for fuel-rich solid propellants. These oxidizers were included in a rocket chamber containing a solid fuel, eg., nitroglycerine or nitrocellulose, for supplying additional oxygen to promote complete combustion of the solid fuel and thereby increase the combustion efficiency. This was essentially a solid type system and embraced the disadvantageous features of non-controllability, expensiveness and short duration operation.

In the light of the foregoing review of previous rocket propulsion systems and of their attendant shortcomings, the present invention embraces, as an object, the provision of a rocket propulsion unit which combines the beneficial features of both the liquid and solid type systems but excludes the undesirable features of each.

Another object of the present invention is to provide a rocket propulsion unit that is inexpensive, simple but reliable, safe and controllable.

A further object of this invention is to provide a rocket propulsion unit embodying the above outlined features and lemploying a liquid fuel and a solid oxidizer.

Further objects and attendant advantages of this invention will become evident from the following detailed description when read in conjunction with the accompanying drawings, in which:

FIG. 1 is an axial section of a propulsion unit embodying the present invention;

FIG. 2 is a sectional view on line 2-2 of FIG. 1;

FIG. 3 is a fragmentary axial section illustrating a modification of the ignition system shown in FIG. 1;

FIG. 4 is a sectional view on line 4-4 of FIG. 3;

FIG. 5 is a fragmentary axial section illustrating a second modification of the ignition system shown in FIG. 1;

FIG. 6 is a sectional View on line 6-6 of FIG. 5;

FIG. 7 is an axial section illustrating a modification of the propulsion unit shown in FIG. 1;

FIG. 8 is a diagrammatic view showing the electric wiring of the ignition system employed by the unit shown in FIG. 7; and

FIG. 9 is an axial section illustrating a second modification of the propulsion unit.

Referring now to FIGS. 1 and 2, there is shown a rocket propulsion unit embodying the present invention and including, in general, a fuel injection system 11, an ignition system 12, a combustion chamber 13, an exhause nozzle 14, and a streamlined cowling 15 enclosing these elements.

The combustion chamber 13 is comprised of a hollow cylindrical casing 16, having flanges 17 and 18, on the fore and aft ends, respectively, thereof, and contains a hollow cylindrical grain of solid oxidizing material 19, which will be described more fully hereinafter. The fore end of the nozzle 14 is formed with a fiange 21 which is secured, as by bolts 22 and nuts 23, to the flange 18 on the aft end of the cylindrical casing 16. The aft end portion of the nozzle 14 is shaped to present a streamlined outer surface 24 and is formed with an annular recess 25 for receiving the aft end of the Cowling 15.

A head cap 26 of cup-like construction having an end wall 27 and a cylindrical side wall 28 withav flange 29 at its open end, is positioned at the fore end of the cylindrical casing 16 with said fiange fastened, as by nuts and bolts 31, to the flange 17 on said casing. The end wall 27 of the head cap 26 is formed with a central opening 32 for receiving a fuel injection nozzle 33, to be described later in connection with the fuel injection system 11, and a pair of orifices 34, one on each side of said opening, for receiving a pair of air or oxygen injectors 35. The side wall 28 of the head cap has formed therein an kopening 36 which receives a spark plug 37 or other sparking means. For optimum ignition performance,

it is preferable to direct the orifices 34 and consequently the air or oxygen injectors 35 in such a manner that the gas emitting therefrom will impinge upon the grain 19 in the combustion chamber 13.

The fuel injection system 11 includes a fuel tank 38 which is connected by a conduit 39 to the fuel injector 33 and a suitable control valve 41 which is positioned in said conduit to permit theregulation ,of fuelinjection into the head cap 26. If desired fuel may be supplied from a suitable source other than a separate tank, i.e., the fuel tank 38, specifically provided therefor. If the unit is to be employed as an assist-take-off device for an airplane, or as a booster for a ramjet missile, fuel may be supplied from the main fuel source of the airplane or missile.

The ignition system 12 comprises a tank 42, containing compressed air or oxygen, a conduit 43 leading from said tank to the injectors 35, and a control valve 44 in said conduit for regulating the rate of injection of air or oxygen, as the case may be, .into the combustion chamber 13. The sparkplug 37 is connected to a sourcev tion upon the invention.

Y 3 a anged ring 45 and similarly, attachedby the nuts and bolts 31 to the ange 29 on the head cap 26 Vis a second tlanged ring 46, both of said rings providing for the support Vof the streamlined cowling on the assembled propulsion unit.

The fuel utilized by this invention may be any one of the numerous organic or inorganic fuels available; examples of organic .fuels are the hydrocarbons such as kerosene, gasoline and diesel oils. Other organic fuels, which may be used include the alcohols, ketones, ethers, organic compounds containing sulfur such as Typical thiophene, and organic compounds containing nitrogen i such as pyrrol and pyridine. Typical inorganic fuels are the hydrogen-nitrogen compounds, for example am! monia" andA hydrazine. Although specific .fuels are enumerated, it is not intended to limit the invention to a propulsion unit utilizing those specific fuels. Any

fuel of the common variety is suitable for use in this injected. To minimize storage hazards it is preferable and'possible touse solid oxidizers that are nonexplosive, non-toxic and. non-inflammable. Examples ofV appro priate oxidants are potassium perchlorate [KC104],

ammonia perchlorate [NH4C104], ammonia nitrate [NHQNOSL nitroparalin s, such as hexanitroethane [C2(N02)6] and higher homologues, nitrosyl perchlorate V[N0Cl04], nitroxyl perchlorate [N02Cl04], persulfuric acids, such as mono-persulfuric acid [H2805] and disulfurie acid [H2S0S], sodium peroxide [Na202], potassium peroxide [K202], potassium superoxide [K02], sulcompressionlat elevated temperature, a binderfof oxidizing or inert material in the form of a low-melting eutectic f mixture, may be used. Ars' an example, a portion of the oxidant and a low melting nitrate or nitrite, eig., sodium nitrate,V lpotassium nitrate vor sodium nitrite, would be suitable. The-following is a generic example of a suit# able composition. Although specific proportions of the ingredients are set forth, it isfto be understood thatthese are only typical, and should not be construed as a limita` 1go v 0f the numerous compositions suitable for use in'manuvfacturing the oxidizing grain, the following examples areV presented as illustrative of compositions having exceptional combustion-supporting characteristics. I

CatalystzwManganese dioxide 2 Binder: Eutectic mixture of potassium perchlorate Percent Y 2 4 v Example Il Oxidant: Potassium perchlorate 83' Catalyst: Manganesey dioxide i 2 Binder: Eutectic mixture of sodium nitrite and potaslsiurn nitrate l5 Y v Example III Oxidant: 'f y y Potassium perchlorate "14 Ammonium perchlorate 56 Catalyst: y

Ferrie oxide and manganese dioxide 2 Oxidant and binder: ammonium nitrate 28 Y Y 100 Example 17V f Oxidant: 2 f,

Potassium perchlorate 3 3 Ammonium perchlorate y 33 Catalyst: Manganese dioxide and ferricroxide y 2 Oxidantand binder: Ammonium nitrate i 32 100*y Example V Oxidantzv Potassium perchlorate V49.4 Ammonium nitrate Catalyst:` v 2 l f. Manganese dioxide Y Ammonium dichromate .6j 2 Y .100.0 In Example I, the` eutectic mixture of potassium perchlorate and sodium nitrate and, `in Example II, the eutec' Examples III', VIV and-V ammonium nitratefitself serves as a binding material as Wellasan oxidant.v ltshouldV be further pointed Vout that in Example V manganese di- 'Y oxide catalyzes the decomposition of the potassium perchlorate, and ammonium dichroinate catalyzes the de- Example 0 v i l Y Percent Oxidant e-.. 83 Catalyst 2 Binder Y l5 and sodium nitrate l5 i l composition of the ammoniumv nitrate.y l. The proportions of oxidant,rca`t'alyst and binder in each` composition mayVA be varied as desired to produce a large variety ofreifective compositions. Y

The method of fabrication of the oxidizing grains willy depend .upon the meltingV point anddecomposition tem?- Y Vperatu're of the oxidant to be employed. If the de composi-. f "tion temperature of the oxidant, with the catalyst added, is

higher than its melting point, afsimplecasting-methodrmay beused. Howevenif the decomposition,temperature is Y .lower than the melting point, then a simple casting method -1 is notsuitable since decomposition'willoccur during the casting operation. In-the latter case, compression`mold ing with a binder at .temperatures'belowy the Vmelting point 2 maybe used for consolidating the oxidant into an `oxidizing b grain; ,v Y. Y

'In'operation,. the, control valves 41 andY 44l are `opened to permitv the injection offffuel and oxygen intothe head 1 cap 26, and thus form a combustible mixture. v A sparkV K vfrom-the spark plug l37 initiates the burning ofthe mixture which then isapplied to thesurface of the grain 19. The intense heat produced by the burning mixture causes thev grain 19 tok decompose thereby evolving oxygenwhich reacts with more fuel 'toi further intensify the .heat freleased; The -rate of oxygen evolution fromthe surfacei ofthefgrain'increasesuntil itis suicient to'burnV the :fuel

being injectedinto the combustion chamber 13 land mainj l tain a source of heat adequate to promote further decom 'A position of the grain. When the rate of oxygen evolution is great enough to produce sufficient heat by reaction with the fuel to vsustain the decompositionvrof ,the grain 19', the

control valve 44Iis closed thusrshuttingoi Vthe/oxygen.Vv

supply. Concurrently, the production of combustion gases increases thereby raising the gas temperature and pressure within the combustion chamber 13. The gaseous combustion products discharge through the exhaust nozzle 14 with high velocity and momentum to produce a' forward thrust. If desired, the fuel control valve 41 may be adjusted to admit more or less fuel into the combustion chamber. Thus, the forward thrust of the propulsion unit may be regulated.

Combustion within the chamber may be extinguished by turning ofi the fuel control valve 41, when it is desired to discontinue operation of the unit. Subsequently, if need be, combustion may be reinitiated by again injecting fuel and air or oxygen into the head cap 26, and igniting the resulting combustible mixture. The oxygen is then shut off when the rate of oxygen evolution from the grain 19 becomes sufficient to support the combustion of the fuel and maintain the temperature'required for decomposition. It, thus, can be seen that propulsion unit of thisl invention can be controlled to produce a forward thrust, or not, as desired.

In the propulsion system shown in FIGS. l and 2, it is preferable to inject air into the head cap 26 at an angle rom the end wall 27, in order to impinge the burning ignition gases directly upon the grain 19. Nevertheless,

Y several other methods of injecting air or oxygen are possible. Of these several methods two are illustrated: one in FIGS. 3 and 4, and the other in FIGS. 5 and 6.

Referring to FIGS. 3 and 4, an orifice 47 for receiving an air injector 48, is provided in the side wall 28 of the head cap 26 and is directed tangentially, as shown, into said head cap. In this manner the burning ignition gases are given a vortex motion which results in better mixing and complete combustion of the ignition mixture.

In the method shown in FIGS. and 6, orifices 49 for receiving injectors 51 are also formed in the side wall 28 of the head cap 26 but are directed radially, as shown, into said head cap. This modification, although not as effective in heating the grain 19 as those shown in the preceding figures, is entirely suitable for ignition purposes.

Other means for bringing the grain 19 to its decomposition temperature are possible. Two modifications of the ignition system are shown in FIGS. 7 and 8, and FIG. 9.

` The modification shown in FIGS. 7 and 8 employs the combustion chamber `13, the exhaust nozzle 14, and the streamlined cowling which were described in connection with the propulsion unit shown in FIG. l, and which will not be described further here.

The head cap 52, however, is of slightly different construction and includes an end wall 53 having a central opening 54 and a pair of orifices 55, one on each side of said opening and a cylindrical side wall 56.' The central opening 54 receives a fiare tube S7, to be described hereinafter, and the orifices 55 receive a pair of fuel injectors 58.

As a part of the ignition system 12, the fiare tube 57 is constructed with a closed end 59 and an open end 61, and houses four flares 62 separated from each other by insulating partitions 63, as shown in FIG. 8. The flares 62.- are each provided with squibs 64 connected in series to a battery 65 and separate poles of a multi-throw switch 66, so that upon successive actuations of said switch the Asquibs will be detonated in the order of their proximity to the open end 61 of the flare tube 57.

The fuel injection system 11 is essentially the same as Athat shown in FIG. 1, including a fuel tank 67, a pair of conduits 68 connecting the fuel injectors 58 to said fuel tank and a fuel control valve 69 for regulating the rate of fuel injection into the combustion chamber 13.

The operation of the above described propulsion unit is as follows. The switch 66 is actuated to detonate the first squib 64 in the flare tube 57. The squib in turn ignites the first fiare 62 which produces an intense heat. The surface of the grain 19 is thus heated to its decomposition temperature, whereupon oxygen is evolved. Then the control valve 69 is opened to permit the injection of fuel 6 into the combustion chamber where it reacts with the evolved oxygen to further intensify the heat within the chamber. When the flare 62 burns out, combustion of the fuel in the chamber 13 releases sufficient heat to sustain the evolution of oxygen from the surface of the grain 19 and the temperature and pressure within the chamber build up. The high temperature, high pressure combustion gases produced by the combustion of the fuel discharge with a high velocity and momentum through the exhaust nozzle 14 to impart a forward thrust to the unit. If desired the control valve 69 may be adjusted to admit more or less fuel into the combustion chamber, thus regulating the magnitude of forward thrust.

Combustion within the chamber 13 may be extinguished by turning off the fuel control valve 69, when it is desired to discontinue the operation of the unit. Subsequently, if need be, the combustion may be reinitiated by actuating the switch 65 to ignite the second fiare tube 57. As described'above, the burning fiare heats the surface of the grain 19 to its decomposition temperature and oxygen is evolved. Then the fuel control valve 69 is turned on and combustion proceeds, as previously, to produce high temperature, high pressure gaseous products which discharge through the exhaust nozzle 14 to impart a forward thrust to the unit. Operation of the unit may be discontinued and reinitated as many times as the number of fiares 62 present in the flare tube 57 will permit.

Referring now to the modification shown in FIG. 9, there is illustrated a propulsion unit comprising the combustion chamber 13, the exhaust nozzle 14 and the streamlined cowling 15 as described in connection with the FIG. l embodiment. The fuel injection system 11, however, is slightly modified and the ignition system 12 involves the utilization of a high resistance wire 71 lfor heating the grain 19.

In detail, the head cap 72 is constructed with acylindrical side wall 73 and an end wall 74. The end wall 74 has formed therein a central opening 75 for receiving a fuel injector 76 and a pair of orifices 77 disposed on either side of said central opening for receiving two insulating sleeves 78, which support the high resistance wire 71 of the ignition system 12.

The fuel injector 76 is connected by a conduit 79 to a suitable fuel tank 81 as in the FIG. l embodiment, and a fuel control valve 82 in said conduit permits the regulation of fuel injection into the combustion chamber 13.

The ignition system'12 of this modification includes the high resistance wire 71 which extends into the combustion chamber in close proximity to the grain 19. The insulating sleeves 78 support the wire 71 which passes therethrough out of the chamber 13 to a battery S3 and a switch 84.

In operation, the switch 84 is closed permitting current, from the battery 83, to flow through the high resistance wire 71 which heats up to raise the temperature of the grain 19. When the decomposition temperature of the grain is reached the evolution of oxygen commences and the fuel control valve 82 is turned on to inject fuel into the chamber 13 where reaction with the evolved oxygen takes place. When the heatreleased by the reaction of fuel and oxygen becomes sufcient to maintain the grain 19 at its decomposition temperature, the switch 84 is opened to arrest the fiow of current through the high resistance wire 71. The high temperature, high pressure combustion gases produced by the fuel-oxygen reaction discharge at high velocity and momentum through the exhaust nozzle 14 to impart a forward thrust to the unit.

The thrust of the unit may be regulated by adjusting the fuel control valve 82 or eliminated entirely by turning off said valve. Combustion of fuel may be reinitiated and extinguished as desired by following the foregoing procedure.

What is claimed is: V i 1. A propulsion unit, comprising, a combustion chamber, a solid body of oxidizing material Within said .f

chamber, and meansfor injecting uid fuel into said chamber.

, 2. Apropulsion unit, comprising, a combustion chamber, an exhaustnozzle connected to said chamber, a Solid body of oxidizing material within said chamber, means for injecting fluid fuel into said chamber, means for controlling the rate of fuel injection, and ignition means for initiating the combustion of said fuel within said chamber.

3. A propulsion unit, comprising, a combustion chamber, a solid body of oxidizing material within said cham'- ber, a fuel injectorfor introducing fluid fuel into said chamber, and a plurality vof. injectors for initially introducing oxidizing gas into said chamber to initiate Vcombustion of said fuel.

4. A propulsion unit, comprising, a combustion cham-Y. ber, a solid body of oxidizing material within said chamber, means for injecting fluid fuel into said chamber, and a flare forv preheating said oxidizing material to decom# position temperature, whereupon 'oxygen is evolved'to` support the combustion of said fuel. Y

5. A propulsion unit, comprising, a combustion chamber, a solid body of oxidizing material within said chamber, means for injecting liuid fuel into said chamber, a

high resistance Vwire within saidV chamber, and a source of electric energy associated with said wire for preheating lsaid oxidizing material to decomposition temperature;L

whereupon oxygen is evolved to support the combustion of said fuel. Y

V6. A method of producing a propelling gaseous fluid which comprises supplying a stream of iuid fuel'to the f surface of a'solid body of an oxidizing material.

7. A'rnethod as delined in claim 6 whereinv the oxidiz-X ing material consists essentially of a major proportion o f` an oxidizer and a catalyst to promote the decomposition" of said oxidizer. Y n

8. A method as defined in claim 7 wherein the solid body of oxidizing material includes a binder toV consolidate said'oxidizer and said catalyst.

1li. Amethod as defined inA claimf 6 wherein the solid body'of oxidizingmaterial consists essentially of a major, proportion of `potassium perchlorate and aminor'proporf. Y

tionfof manganese dioxide. Y V

Cil

12. A method as defined` in claim-6 wherein the solid 'Y body of oxidizingI material consists essentially of a,y major proportion of potassium perchlorate, aminor proportion -K ofmanganese dioxide and a` binder consisting of .an eutectic mixture Y' of potassium( perchlorate and sodium `nitrate.'` 'Y Y 1,3. A method as aanedrn vclaim 6 whereinthe ,solid Vbody ofY oxidizing materialconsisrts essentially of a major proporton'of potassium-perchlorate, a minor proportion Y of manganese dioxide and a `binder consisting of an eutectic 'mixturejof sodium nitrite andV potassium nitrate. 14. A method as defined in claim 6 wherein the fuel is an organicfuel.

15. A method as dened in yclaim l6 whereinthe fuel 'i Y' l isfanv inorganiclfuel. v'

u 16. A method ,ofproducing a .propelling gaseous fluid which comprises supplying'heat to the surface of a solid body of oxidizing V.material .until decomposition ofthe oxidizing' material4 is initiated and'thereafter supplying 9. A method as. defined in `claim 6 wherein the .solid body'of oxidizing material consistsessentially ofa major proportion of potassium perchlorate. l,

10. A method las defined in claim 9 wherein the solid body of oxidizing material includes an oxidizer'selectedV from thergroup consisting of ammonium perchlorate andA ammonium nitrate.

a stream of fluid fuel to said surface. Y

v i References Citedfin the Yfiile of this patent `Y UNITED STATES PATENTS `24,898 y OTHER REFERENCES j i Mellor: Comprehensive Treatise on Inorg. and Theo.-

retical Chem., Longmans, Green & Co., N.Y.'(1928), vol.' 8, pp. 317-318 incl. V Y. Y Y Chemical .and Engineering News, vol; 23, No'. 17, Sep'- Y tember 1.0 1945, p. 1519.

Claims (2)

1. A PROPULSION UNIT, COMPRISING, A COMBUSTION CHAMBER, A SOLID BODY OF OXIDIZING MATERIAL WITHIN SAID CHAMBER, AND MEANS FOR INJECTING FLUID FUEL INTO SAID CHAMBER.

6. A METHOD OF PRODUCING A PROPELLING GASEOUS XXXX WHICH COMPRISES SUPPLYING A STREAM OF FLUID FUEL TO THE SURFACE OF A SOLID BODY OF AN OXIDIZING MATERIAL.

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