US3019687A - Method of forming a solid propellant - Google Patents

Description

Feb. 6, 1962 c. A. GONGWER METHOD OF FORMING A SOLID PROPELLANT 2 Sheets-Sheet 1 Filed Sept. 11, 1952 INVEN TOR. GAL VIN A. GONGWER Feb. 6, 1962 c. A. GONGWER 3,019,687

METHOD OF FORMING A SOLID PROPELLANT Filed Sept. 11, 1952 2 Sheets-Sheet 2 IN VEN TOR. Cfi LV/N A GONGWER A37 TOEWE Y 3,01,687 METHGD 9F FGRRKNG A SQHB E RGT'ELLANH Calvin A. Gongwer, Glendora, Qalifl, assignor, by mesne assignments, to Aeroet-General Qorporation, Azusa, Calii, a corporation of Ghio Filed Sept. 11, 1952, Ser. No. 359,039 Claims. (Cl. 86-1) This invention relates to jet propulsion and more particularly to a propellant charge and method of making it, which is useful for the underwater propulsion of vessels such as projectiles.

An object of the invention is to provide a solid propellant char e exceptionally useful for underwater op erations. A related object is to provide such a charge which generates no substantial amount 'of gaseous products during reaction.

This is a continuation in part of my copending application Serial No. 175,397, filed July 22, 1950.

The charge in accordance withmy invention comprises an intimate mixture of a finely divided metal and a finely divided oxidizer. The metal may be a powdered aluminum and the oxidizer may be a powder from the group consisting of alkali and alkaline earth metal perchlorate, chlorates, chromates, dichromates and permanganates.

In forming the solid charge, the powdered metal and the finely divided oxidizer are intimately mixed in a container, and the mixture and container subjected to pressure preferably in the order of about 30,000 to 100,000 pounds per square inch. This will intimately bond the metal and oxidizer together in a solid mass. The bonded metal and oxidizer charge may also be restricted to control its burning rate.

An important advantage and feature of the use of this charge is that it can be operated without releasing gaseous products of combustion and this is a special advantage in the case of torpedoes and the like, used in wartime.

The foregoing and other features'of my invention will be better understood from the following detailed description and the accompanying drawing in which:

FIG. 1 shows an end view of an underwater device looking at the forward end, said device containing a propellant charge in accordance with this invention;

FTG. 2 is a cross-section view of the device taken at line 2-2 of FIG. 1 and shows a manner of locating therein the propellant charge according to the present invention;

PEG. 3 is across-section taken at line 3-3 of FIG. 2;

FIG. 4 is an enlarged plan view-showing awater sprayer used in the device;

FIG. 5 is an end view of the injector portion of the sprayer shown in FIG. 4;

FIG. 6 is a view partly in cross-section showing a restricted charge; and

FIG. 7 is a cross-section view taken on the line 7-7 of F IG. 6.

The device shown in the drawings comprises a torpedo-shaped body 10 provided with an inlet opening 11 at its forward end and a converging-diverging exhaust nozzle 32 at its rearward end. The torpedo body is essentially divided into three compartments: a forward compartment 13, and intermediate compartment 14, and a rear compartment 17. The forward compartment 13, in which may be carried some form of payload, such as an explosive charge, is separated by a partition or partitions 16, from the intermediate compartment 14 in which is stored a propellant charge 15. The compartment or space 17 is located between the rear end of the propellant compartment and the exhaust nozzle 12; and this space 17 serves as a reaction chamber which increases in size as the propellant charge is burned.

A tube 13 is attached to the inlet opening 11 and is the preferably positioned symmetrical to the longitudinal axis f the torpedo, so that it passes axially through compartment 13, partitions 16, compartment 14 and extends into the reaction chamber 17. The rearward end of tube 18 is provided with a spray device 19 having a plurality of orifices or openings 20 through which water entering the tube 18 is discharged into the reaction chamber 17.

A constant fiow control valve 21 is located within tube 18, and this serves to keep the amount of water entering the reaction region through the spray device, substantially constant throughout the operation regardless of variation in the rate of travel. A portion of the stream passing through the constant flow control valve 21 in tube 18 is conducted by a conduit 21a to an annulus 21b in the region of the forward portion of the exhaust nozzle i2. Annulus 21b is connected to the diminishing region of the nozzle by a plurality of small injector orifices 20a. These introduce water into the throat or constricting portion of the exhaust nozzle 12. This water is used to keep the nozzle free of solid encrustation from the residue of the burning propellant.

A conical member 232 which, together with the steam nozzle 12, forms a steam injector and having a larger forward diameter than the diameter of the discharge end 2 3 of the exhaust nozzle 12, is positioned to overlap the rear end of nozzle 12, thereby providing an annular opening 24. The diameter of member 22 then decreases as it progresses downstream until it reaches the throat 26 of the diffuser portion 27, and the diffuser is preferably made to enlarge slightly between the throat 26 and the outlet end 28.

A plurality of fins 29 are mentor 22 and the body of the secure the augmentor 22 in to the nozzle 12.

In the drawings the missile is guided missile and fastened to both the augprojectile ill and these fins fixed relationship with respect assumed to be an unif desired could be spin-stabilized by providing a twisted or spiral configuration to the fins.

sufficient to enable the projectile to follow a straight line trajectory. However, this is not necessary to the invention and any system of controls found to be satisfactory could be used.

It is desired that the propellantcharge should generate no uncondensable gaseous products during the reaction, therefore, only those fuels or oxidizers which produce substantially solid or liquid combustion products should be employed. While all metals which are capable of reacting with an oxidizer to form a solid or liquid reaction product are usable, it is preferable to employ those metals which have a low molecular weight and at the same time are capable of releasing a large amount of heat per gram of fuel. The most ideal fuel for this purpose is aluminum metal, which has a molecular weight of only 27', and yet when it is oxidized to A1 0 it is capable of releasing 2.49 kcaL/grarn of propellant when reacted with potassium perchlorate.

Aluminum reacts with potassium following manner:

8Al+3KClO e 4Al O -l3KCl-l-2.49 kcal./ gm. of propellant perchlorate in I the The propellant charge can he made by intimately mixing a powdered oxidizer and a powdered metal until the mixture is substantially homogeneous. The mixture can then be placed in a mold, cylindrical in form, and the metal and oxidizer mixture is subjected to a pressure which preferably lies between 50,000 and 100,000 lbs. per square inch; although it has been observed that in some cases pressures as low as 30,000 lbs. per square inch are sulficient to cause the mixture to bind itself into a solid mass. The pressure intimately packs the fuel and oxidizer together and the ductile aluminum. or other metal binds glass tape and impregnated with 21 a itself satisfactorily with the oxidizer under this pressure, forming a grain that is for all practical purposes free of voids and does not require any other binder to hold it together. Since the charge is required to burn in a re stricted or controlled manner (that is, with a burning rate which remains substantially constant throughout the operation, and burning on only the desired faces of the grain), it is usually desired to ferential surface of the grain from burning. This can be accomplished by placing the powdered fuel and oxidizer within a non-water reactive metal shell such as, for example, thin copper jacket and then subjecting the jacket and the mixture to the high pressures mentioned above. This causes the charge to bind itself together and at the same time to bind itself to the jacket, and also to the tube 18 if the tube be set within the propellant mixture before the application of the pressure. In order to permit passage of the tube 13 through the propellant charge and at the same time to provide a satisfactory inner liner for the charge, the charge may be cast or formed around a small inner tube of suificient diameter.

Another way in which the charge may be utilized is to insert the powdered mixture into the propellant chamber of the device and then subject the chamber and the powdered mixture to the elevated pressures. This, or any other Way of lining or preventing the burning of the circumferential surface and other surfaces which are not to be permitted to burn, is satisfactory.

In the event that it is desired to prepare the replaceable charges to be inserted into the chamber of the motor and at the same time to have the charge act as a restricted burning charge, that is, a charge that all the burning occurs on a limited surface only, it is possible to form the grain in the manner which is shown in FIG. 6 and FIG. 7. In this embodiment the grain 15, which is preferably cylindrical, is enclosed in a restriction comprising a plastic liner 35 which completely surrounds the grain on all sides with the exception of the burning surface. The restricting material may be of any suitable type. A preferred form of restriction is one in which the grain is Wrapped with polyester type thermosetting resin which both attaches the tape to the grain and at the same time welds the restriction into a protective shell when cured. The base of the wrapped grain 36 in this manner is also coated to prevent it from burning.

In FIG. 6 the base 36 of the grain is positioned on a supporting base '37 that is provided with threaded bores 38 to permit the grain to be attached to the motor proper. The base 37 is provided with a plurality of supporting rods 39 that are secured to the base 37 by means of holes 40 extending a short distance into the base from the outer circumference and correspond in size to the diameter of the rods 39. Holes 40 are positioned near the rearward side of base 37. The rods 39 are provided with a bent end 41 to fit into the holes it) so that the long part of the rod extends along the side of the grain and extends a short distance beyond the end of the grain. The rods are bound in place to the liner 35 by means of a second external wrapping which can also be glass cloth tape impregnated with plastic and subsequently cured. The outline of this outer liner may be in the form of any polyhedron depending upon the number of rods employed. In FIG. 7 twelve rods are used giving the outer surface of the charge a form of a dodecahedron. When a grain of this type is used, it is usually ignited by means of an ignitor 42. Igniter 42 is supported in proper relationship with the grain by a plastic housing 43, which, in the embodiment shown in FIG. 6, is in the form of a conical plastic shell. The igniting charge 44' is placed inside of the apex 47 of the housing 43. A squib 45 such as an electric match having initiator wires 46 is employed to supply necessary heat and flame to cause the igniter material 44 to burn. When this material burns the flames impinge against the burning surface of the grain 48 causing it to burn.

The manner in which the device operates is as follows: The projectile with its charge of compressed metal and oxidizer is launched into the water at high velocity. The motion of the projectile through the water develops a ram pressure, causing the water to enter tube 18, and spray through the openings 29. A firing squib 30 located at the rear of the propellant charge is fired by some suitable means, such as are Well-known, at the time the projectile is launched. One way of firing the squib, for example, is to make it of a water-reactive material, so the reaction will start spontaneously at the time the sprayed water comes in contact with the squib. Such a squib may be a mass of water-reactive chemical such as sodium or the like. The combustion of the squib generates sulficient heat to start the reaction between the metal and oxidizer in the charge; and the reaction once started will continue unabated until all of the propellant charge has been consumed.

The required propellant charges are those which produce substantially only solid products of combustion and heat when burned, which heat converts the water, con tinuously spraying through the orifices 20, into steam. The steam under pressure escapes through the nozzle 12 and impinges in the chamber 31 against the water which is entering the injector through the annular scoop 24. By the time the steam and water mixture has reached the throat 26 virtually all of the steam should be condensed to water and a substantial portion of velocity of the'steam will thus have been transferred to the water. The velocity of the water at this point will be greater than the original spouting velocity of the Water entering the scoops 24 but will be less than the velocity of the steam jet. The pressure at the throat 26 and in the chamber 31 should then be approximately equal to the equilibrium pressure of the mixture of water and steam which will be a very low value because of the large amount of cold Water present.

Downstream from the throat 26 where the passageway undergoes a slight gradual expansion to the exit opening, this enlargement serves as a diffuser and is suflicient to cause some of the velocity head to change into static pressure which is desired for discharging the jet against the existing external static pressure. The area of the entry scoop 24 and the amount of the enlargement in the diffuser section should preferably be designed to be selfadjusting so as to vary with the depth of submersion which may vary over wide limits; and with this in mind, good design proportions can be selected. This may be accomplished by tapering the lip 24a of the conical member 22 to form a section of decreasing thickness which becomes very thin as it approaches the end. The thin lip is deflected by the external pressure of the water acting upon it, thereby decreasing the area of the opening as the external pressure increases upon submersion to greater depths.

An important factor in the operation is that the introduction of water into the reaction chamber is insured. When the device is travelling at high speeds, for example, knots minimum, the ram head acts against the water in the tube and places the water under sufiicient pressure to cause it to be injected into the reaction chamber against the pressure developed by the restriction provided on the exit of the steam by the nozzle 12. In this type of device no water pump is required; and the operation can be started by either launching it at high velocities or providing an auxiliary water injection in the reaction chamber until the velocity is sufliciently great to de-. velop the necessary ram pressure.

Another outstanding characteristic is the fact that the propellants which have been referred to generate only combustion; the heat being used to convert the Water into steam and the solid products being exhausted through the nozzle and the diifuser. The propellant charge burns cigarettewise thereby insuring a constant burning area and burning rate on its rear exposed surface.

Since the direction of the flow in the case of both water entering through the scoops 24 and the steam escaping through the exhaust nozzle lies in the same general direction, the two fluid streams impinge each other in an impact in which the total momenta of the water and of the steam streams are conserved in the momentum of the resulting stream of Water and condensate at 26.

The phenomenon that the efficiency becomes greater at substantial depths than at shallow depths may be in part explained by the fact that the back pressure acting on the steam nozzle is very low. This back pressure is the saturation pressure of the mixture of condensate and condensing water. Furthermore as the depth increases, the condensing water entering the device through the scoops 24 spouts into the condensing chamber 31 from the surrounding medium at increasing velocities. This causes the impact between the steam and water to take place with more kinetic energy being transferred from the steam jet to the stream of condensing water. This is due to the fact that the steam velocity is many times greater than the velocity of the water; and the mass rate of flow of the stream is many times less than that of the water; in accordance with the law of conservation of momentum, a substantially constant velocity increase is therefore given to the mass of water. Since the water has an initially high velocity, and in addition is given an additional velocity, the kinetic energy of the water mass is much higher than if the same velocity increase were transferred to a slower moving mass of water. This is because kinetic energy increases with the square of the velocity. In this manner, the energy of the steam is more effectively transferred to the condensing water as the depth increases and as a result, higher energy is obtained in the jet formed by the combined condensate and condensing water. This results in a higher exit velocity and more thrust is developed, other things beiu equal, as the depth of submersion increases.

Among the advantages of my invention a e the following: It is capable of operating at very great speeds; and the efiiciency increases as the depth of submersion be comes greater, a feature which has heretofore been unknown in underwater heat engines. The devices possesses no moving parts or valves with the possible exception of the depths compensation for the scoops, therefore, requires no careful adjustment or expensive repair. The fuel and oxidizer charge can be pressed into a rigid grain which is insensible to wide temperature variations and may be instantly employed regardless of the length of time the grain may have been stored.

A particular feature of the invention which is of importance in naval operations during war time is that the device operates without the creation of a gaseous wake, and it is therefore difficult to detect its presence.

Another feature is that the energy density of the compressed propellant 8Al+3KClO exceeds 6 kcaL/ cc. and this together with the goo-d thermopropulsive efficiency provided gives an unusually high value of propulsive horse power hours available from a missile of given size. This is reflected by permitting the development of small missiies of long range and high speed.

It should be understood that the description and drawings employed in the above specification are given by way of example rather than of limitation; and the invention is not limited except by the scope of the appended claims.

I claim:

1. A method of forming a solid integral propellant charge which comprises intimately mixing powdered aluminum with finely-divided potassium perchlorate, placing said mixture within a metal container, subjecting said mixture and container to pressure between 30,000 and 100,000 p.s.i., thereby intimately bonding said aluminum and potassium perchlorate together to form a solid mass and simultaneously bonding said solid mass to said metal container.

2. A method of forming a solid propellant charge according to claim 1 wherein the metal container is a copper tube.

3. The method of forming a solid propellant charge which comprises intimately mixing in approximately stoichiometric proportions, a finely divided metal having an atomic weight less than about 27 and finely divided inorganic oxidizing salt selected from the roup consisting of alkali metal and alkaline earth metal chlorates, perchlorates, chromates, dichromates, and permanganates, placing said mixture within a metal container, subjecting said mixture and container to a pressure of from about 30,000 to 100,000 p.s.i., thereby intimately bonding said metal and inorganic oxidizing salt together to form a solid mass and simultaneously bonding said solid mass to said metal container.

4. The method of claim 3 wherein the metal container is a cylindrical metal container.

5. The method of claim 3 wherein the metal container is a copper tube.

References Cited in the file of this patent UNITED STATES PATENTS 356,651 Linton Jan. 25, 1887 1,253,597 Hitt Jan. 15, 1918 1,430,272 Werner Sept. 26, 1922 1,506,323 ONeill Aug. 26, 1924 1,528,101 Davison Mar. 3, 1925 1,775,063 Bradner Sept. 2, 1930 1,882,365 Lubelsky Oct. 11, 1932 2,356,149 Davis Aug. 22, 1944 2,373,799 Wilson Apr. 17, 1945 2,479,470 Carr Aug. 16, 1949 2,479,828 Geckler Aug. 23, 1949 2,529,465 Wallace Nov. 7, 1950 2,539,404 Crutchfield et al. Ian. 30, 1951 2,563,265 Parsons Aug. 7, 1951 2,573,471 Malina et a1 Oct. 30, 1951 2,600,678 ONeill June 17, 1952 2,617,326 Morris Nov. 11, 1952 OTHER REFERENCES A.P.C. Application of Charles Baron, Serial No.

393,137, published June 15, 1943.

Journal of the American Rocket Society, No. 72, December 1947, pages 14 and 15.

Claims (1)

1. A METHOD OF FORMING A SOLID INTEGRAL PROPELLANT CHARGE WHICH COMPRISES INTIMATELY MIXING POWDERED ALUMINUM WITH FINELY-DIVIDED POTASSIUM PERCHLORATE, PLACING SAID MIXTURE WITHIN A METAL CONTAINER,M SUBJECTING SAID MIXTURE AND CONTAINER TO PRESSURE BETWEEN 30,000 AND 100,000 P.S.I., THEREBY INTIMATELY BONDING SAID ALUMINUM AND POTASSIUM PERCHLORATE TOGETHER TO FORM A SOLID MASS AND SIMULTANEOUSLY BONDING SAID SOLID MASS TO SAID METAL CONTAINER.

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