US2989922A - Ramjet propulsion device - Google Patents

Description

June 27, 1961 M. H. GREENWOOD EI'AL RAMJET PRoPULsIoN DEVICE Filed Feb. 17, 1953 ggf,

3 Sheets-Sheet 1 By @aww-fwd# Jlm 2.7, 1961 M. H. GREENWOOD ETAL 2,989,922

RAMJET PROPULSION DEVICE 3 Sheets-Sheet 2 Filed Feb. 17,' 1953.v

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RAMJET PROPULSION DEVICE 3 Sheets-Sheet 3 Filed Feb. 17, 1953 United States Patent Office 2,989,922 Patented June 27, 1961 Filed Feb. 17, 1953, Ser. No. 337,282 11 Claims. (Cl. 102-49) This invention relates to ramjet propulsion devices of general application but is described particularly in connection with a ramjet projectile adapted to be red from a conventional rifled gun. In general, the invention relates to a ramjet propulsion device in which the Velocity of the device through the air effects compression of air within a combustion chamber in which a supply of solid, self-sustaining fuel is provided. Sucient heat is produced by compression of the air to initiate combustion of the fuel which continues to burn due to the movement of air through the device. The heated air and products of combustion are then conducted to an appropriate nozzle to increase a thrust reaction. The principles of this invention may be applied to ramjet engines of general application Where the initial high velocity can be attained by other means or can be applied to projectiles wherein initial velocity is supplied by the usual primary propelling charge in a gun.

It has heretofore been proposed to supplement the energy imparted to a projectile while in the barrel of a gun by some reaction propulsion means contained within the projectile and rendered effective to continue to produce thrust after the projectile has been fired. Such proposals have been directed to liquid fuel burning devic and to devices containing rocket fuels. The rocket fuels are those containing, within themselves, sufficient available oxygen to support combustion of the fuel charge without the necessity of supplying oxygen from the air through which the device travels. In devices employing rocket fuels no provision can be made for controlling the rate of combustion once it has been started. It is known that ramjet propulsion devices are very sensitive to the quantity of heat added to the air passing therethrough. If the quantity of heat added to the air, in relation to the speed or velocity of the device, is too great or too little, it can actually develop drag rather than produce thrust. One reason why the previo-us proposals discussed above have not been successful is the fact that mechanism for properly metering fuel to the combustion chamber was impractical in a small device and the Irate of combustion of the type of fuel proposed could not be properly controlled.

-Ramjet motors are known to be operable with good efficiency in a speed region above Mach 1.5. A projectile fired from a conventional gun leaves the muzzle at a velocity in the neighborhood of 2,800 feet per second (Mach 2.5), well above the speed at which ramjets become effective. At Mach 2.5 air within a ramjet motor should attain a temperature of from 650 F. to 775 F., depending upon humidity, ambient temperature, and other factors. Such temperature range is sufficient to ignite certain solid fuels.

To be effective in a device of the necessarily small dimensions of a projectile, it is necessary that the temperature of the inner walls of the combustion chamber be maintained at a very high value, otherwise impractical length or diameter of combustion chamber will be necessary. For a ramjet to be small enough in dimension to be used as a projectile for conventional guns, only a solid non-ashing fuel burning on its surface can be utilized since liquid or gaseous or pulverized solid fuels cannot support combustion in such a small ramjet.

The present invention contemplates a ramjet propulsion device consisting essentially of a supersonic diffuser portion to convert velocity energy into pressure energy at a high temperature and in the particular embodiment described herein the supersonic diffuser portion consists in part of the walls of the warhead of a projectile, although it is to be understood that the provision of a warhead is not an essential feature of the invention in its broader aspects. The device also includes a combustion chamber into which the hot air at high pressure is conducted and which combustion chamber is lined with a solid, selfsustaining fuel of low ash content. The fuel does not contain its own oxygen, which is supplied by the air stream. A suitable fuel may oonsist of powdered charcoal which could be mixed with a suitable binder such as oil and asphalt formed to the desired shape. From the combustion chamber the heated air and products of combustion may be conducted to an expansion nozzle where pressure and heat are converted into velocity energy, in the usual manner, resulting in additional thrust applied to the device. When employed as a projectile containing a warhead or equivalent element, the invention also contemplates the provision of a false breech member or other means to confine the primary propulsion gases, or most of them, in the gun to the space behind the projectile and means to support the warhead and/or the body of fuel against distortion during the period of acceleration within the gun barrel.

A ramjet propulsion device of the type proposed by this invention offers many advantages over previous proposals, among them being:

(l) No flame blowout. After ignition is effected and combustion of the fuel starts, there is no danger of the flame being blown out by the air stream since combustion takes place on a solid body of fuel and the unburned fuel immediately adjacent to the burning fuel is kept sufficiently hot to ignite as soon as it is exposed to oxygen in the air stream.

(2) By using a body `of solid fuel of the type proposed the rate of combustion will vary with the supply of oxygen; at higher velocities more air, and with it more oxygen, it supplied to the combustion chamber and hence a greater rate of combustion results, whereas at lower velocities the rate of combustion is lower due to the lower rate at which oxygen is being supplied.

(3) The walls of the combustion chamber are maintained at a high temperature not only to effect continuous self-ignition of the fuel but also to produce more efficient heat transfer to the air Without necessitating a large combustion chamber.

l(4) The body of solid fuel lining the combustion chamber acts as a heat insulator to retain the heat of combustion within the motor and render it available for propulsion purposes.

(5) The centrifugal force acting on solid or liquid unburned particles of fuel, when the invention is employed in a projectile to which spin is imparted, forces the solid or liquid unburned particles outwardly against the hot walls to insure complete combustion within the combustion chamber.

(6) The use of the solid body of fuel permits higher lair stream velocities since there is no danger of blowout of the flame, and no flame holders are required.

(7) The use of a solid body of fuel also permits a fuelair mixture to be introduced into the combustion charnber instead of air alone. Such a fuel-air mixture can thus be burned, combustion being maintained by the burning solid fuel, even though the fuel-air mixture alone be too lean to support combustion and maintain a flame. Such a fuel-air mixture could be provided by adding gaseous, liquid or powdered solid fuel to the incoming airstream before it reaches the combustion chamber. In such a case the rate of consumption of the solid body of fuel would be reduced, resulting in 1an increased working range and permitting a smaller combustion chamber or a higher temperature in the combustion chamber.

(8) The use of a solid body of fuel results in greater fiexibility in the rate of consumption, in contradistinction to the burning of fuel-air mixtures, which must be supplied within a certain ratio range for successful operation. Such fuel-air mixtures must be nearly stoichiornetric to be successfully burned in a conventional cornbustion chamber, whereas no such limitation governs the burning of a body of solid fuel.

(9) A solid body of fuel as proposed herein will not evaporate and, therefore, does not create a hazard during periods of storage. No explosive gases are formed during periods of storage nor is there any likelihood of explosion while the fuel is actually burning in the combustion chamber during operation of the device.

It is, therefore, an object of this invention to provide a ramjet propulsion device of extremely simple construction, having no metering systems and of high efficiency.

Another object of the invention is to provide a ramjet device that is self-regulating as to the rate of combustion to insure efficient thrust at all speeds and altitudes.

Another object of the invention is to provide a ramjet device that can be made self-igniting upon the attainment of a velocity suitable for ramjet operation.

Another object of the invention is to provide a ramjet capable of operating with a cheap solid fuel.

A sti-ll further object of the invention is to provide a ramjet propulsion device adapted to carry a warhead or the like.

A still further object of the invention is to provide a ramjet projectile employing a cheap solid fuel and means for supporting the fuel and warhead against distortion during the initial period of acceleration.

Another object of the invention is to provide a ramjet of sufficiently small size to be suitable for use in projectiles.

Yet another object of the present invention is to provide a reliable method of igniting a solid fuel in a ramjet combustion chamber.

A still further object of the invention is to provide a simple method of operating a ramjet motor without the use of metering devices.

Still further objects and advantages will become apparent to those skilled in the art as the description proceeds in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-sectional View through a projectile constructed according to the present invention but showing certain parts thereof in elevation;

FIGS. 2 through 6, inclusive, are longitudinal sectional views, similar to FIG. 1, but illustrating further modified forms of the invention; k

FIG. 7 is a fragmentary sectional view taken through one wall of a combustion chamber of a modified form of device showing a modification adaptable to any of the forms shown in FIGS. 1 through 6; and

FIG. 8 is a schematic view of the projectile of the present invention illustrating means for supporting the fuel.

The present invention is illustrated in the drawing as applied to a projectile to be fired from a gun. Numeral 2 indicates a casing or body of the projectile of an outer diameter properly designed to correspond to the diameter of a conventional projectile to be fired fro-m the particular gun. 'Ihe casing 2 may be provided with a projecting portion 4 comprising part of a ring pressed into a peripheral groove and adapted to engage helical lands within the gun barrel to impart initial spin to the projectile in the usual manner. The casing 2 is essentially a hollow tubular structure of generally cylindrical shape but being open at its forward or leading end, as at 6. A warhead 8 is mounted centrally within but spaced from the inner surface of the casing 2 and is supported in such central positionV by means of circumferentially spaced vanes 10 and 12. The warhead may include `a forwardly tapering pointed portion 14 extending from a position inwardly of the open end 6 ofthe casing 2 to a position at the point 18 outwardly and forwardly of the casing 2. The warheadV also includes a central rearwardlyV and conically tapered portion spaced inwardly from the inner walls of the casing 2 to define an annular passageway between the warhead and the casing. The taper of the central portion of the warhead is very slight. The warhead 8 may contain a high explosive charge to be detonated on impact or proximity with the target or may be of any other type of payload that may be desirable. Hereinafter use of the term warhead is to be understood as referring to any such payload, `whether it be a charge of high explosive material, an larmor-piercing mass, a gas-containing capsule, a signalling device, or the like. In fact, the term warhead is intended to include any such devices or combinations thereof.

Preferably the vanes 10 and 12 are so canted relative to the longitudinal axis of the projectile as to maintain or increase the initial spin imparted thereto by the rifiing in the gun. Also, the forwardly tapered portion 14 is so dimensioned and positioned that the point 18 thereof bears such relationship to the leading edge of casing 2 that the shock wave emanating from point 18 during flight of the device at supersonic speeds enters the opening 6 and increases the efficiency of -air compression within the device, all in a well-known manner.

The rearrnost portion of the warhead 8, or its equivalent, tapers rearwardly as at 20 and terminates in a transverse surface 22 adjacent to the forward portion of the combustion chamber 24. The combustion chamber of the device extends generally from the plane identified by line A-A to the plane defined by line B-B. Within the combustion chamber 24 an annular body 26 of solid fuel is positioned in snug contact with the inner surface of the casing 2 and in fact defining the inner surface of the combustion chamber. Preferably, the annular body 26 is sufliciently compact to be self-sustaining. The annular body Z6 is preferably positioned against an annular abutment surface 28 comprising a portion of the casing 2 and is fiared outwardly at its forward end as at 30 to an upper terminus substantially coincident with the inner surface of the casing 2 in a region at the forward end of the combustion chamber.

That portion of the casing 2 defining the annular shoulder 28 can also define an exhaust nozzle 32 of the usual rearwardly fiared type. The entrance to the nozzle 32 is coincident with the edge 33 of the annular shoulder 28. Preferably, the nozzle 32 fiares outwardly to a diameter only slightly less than the outer diameter of the casing 2, thus leaving a transverse terminal surface 34 at the rear end of the casing. For the greatest efficiency, the nozzle 32 should flare to a rearmost diameter equal to the outer diameter of the casing 2 but in FIG. l the surface 34 is provided for a purpose to be pointed out hereinafter.

From the description thus far, it is apparent that the annular passageway surrounding the warhead 8 and leading to the combustion chamber 24 constitutes a wellknown form of supersonic diffuser for converting velocity energy into pressure energy at high temperatures. As is usual, the ducted portion of the diffuser consists of a converging entrance portion extending from the forward open end of casing 2 to the positionl, aslightly diverging passage of substantially uniform section extending from position 16 to the rear edge of the slightly conically tapered portion of the warhead and a portion of highly diverging or rearwardly increasing section leading from there to the combustion chamber. The functioning of such supersonic-subsonic diffuser is well known and need not be described in further detail except to point out that air moving rearwardly in the annular passageway and entering the diverging entrance to the combustion chamber is suciently slowed in velocity to convert enough velocity energy into pressure energy and heat to achieve a high temperature in the combustion chamber. As previously pointed out, the temperature achieved by the air in the combustion chamber is suf- Viiciently high to ignite the solid fuel 26 and maintain continuous combustion thereof.. If desired, a portion'of the annular body 26 of combustible material may incorporate a body of more readily ignitable material, indicated at 36, which may be a body of material containing its own oxygen and of a relatively low ignition temperature. Upon ignition of the body 36 suiicient heat will be developed to ignite the main body of solid fuel 26 instantaneously.

As also pointed out heretofore, the rate of combustion of the fuel 26 will depend upon the condition of the atmosphere and the velocity of the device through the air since at given atmospheric conditions the velocity will determine the rate at which oxygen is supplied to the combustion chamber and the proportions and dimensions of the device may be so designed in relation to the type of solid fuel employed so that the rate of combustion of the fuel is always within the proper range to supply the heat necessary to develop eficient thrust at that particular velocity and altitude.

By the employment of a ramjet propulsion device as described, with a projectile, the essential accuracy or high probability of hitting the target of present day ordnance is preserved while the additional thrust furnished after the projectile has left the gun results in a great increase in the range of the projectile without destroying its accuracy and, in fact, lmay result in an impact velocity even greater than the muzzle velocity imparted to the projectile by the primary propelling charge. In addition, the time from gun to target can be materially decreased which will increase the probability of hitting a moving target.

, In the construction shown, the vanes 10 and 12must necessarily be of limited section so as to provide as little obstruction as possible in the air stream. The vanes 10 and 12 may be subject to rupture under the forces resulting from acceleration of the projectile while being fired from the gun and those acceleration forces may also be sufficient to distort or break the body 26 of solid fuel in the combustion chamber. Furthermore, it is necessary to provide means to temporarily close the passageway through the device during projection from a gun to confine the expanding gases from the primary propulsion charge to the space behind the projectile and not permit those gases to escape through the ramjet device. To this end, a false breech or closure member 38 is provided and consists of a false breech element of substantially the same diameter as the casing 2 or nozzle 33 or between the two, held in abutment with the terminal surface 34 previously described. If desired, the closure 38 may be provided with a centering boss 40 adapted to loosely enter the rear portion of nozzle 32 to center the closure or false breech relative to the casing 2. If desired, the member 38 may be retained on the casing in a temporary manner by means of a suitable adhesive at the surface 34 but such holding means must be weak enough to permit the closure 38 to drop away from the projectile casing 2 after the latter has left the gun muzzle. It is to be remembered that, after leaving the gun muzzle, a relatively high static pressure will exist within the interior of the casing 2 due to the velocity of the projectile and that pressure may be employed to break the bond of the adhesive and eject closure 38 and centering boss 40 from the projectile and permit the same to drop to the ground. An explosive at 22 could be used to eject the false breech.

The closure 38 is also preferably provided with an abutment plunger 42 extending forwardly through the nozzle 32 and combustion chamber 24 into abutting contact with the rearwardly directed surface 22 of the warhead 8 or its equivalent. The plunger 42 will support the warhead 8 and relieve the vanes 10 and 12 of the stresses that would result from the acceleration of the device in the gun barrel and thus prevent their unwanted distortion.

If the body of solid fuel 26 is of such frangibility that the accelerationforces might rupture the same or cause its disintegration or breaking in any way, adequate support may be provided by filling the interior of at least the combustion chamber 24 and nozzle 32 With a suitable ilowable granular powdered or liquid material (see FIG. 8) of substantially the same specific gravity as the solid fuel 26. Such material would act to support the body of fuel during acceleration and would be exhausted from the projectile immediately upon removal of the closure 38 (any residues would burn away) and thus condition the device for immediate ignition of the fuel and operation as a ramjet propulsion device. Also, gunpowder could be used as a filler and ignited in the same manner as 36; this would assure immediate ignition of the solid fuel 26. 'Ihe granular or fluid material hereinabove 1described may obviously be used with any of the modifications to be described hereinafter, and particularly in the modifications of FIGS. 4, 5 and 6 in addition to that of FIG. l.

In the further modifications illustrated in FIGS. 2 through 7, parts bearing the same reference numerals are substantially identical to similarly numbered parts described in connection with FIG. l.

In the modification shown in FIG. 2 the warhead 8 is provided with a rearwardly extending plunger 44 projecting from the surface 22. A closure plug 46 is provided with an outwardly flared lower portion 48 complementary to the inner surface 32 of the jet nozzle and is provided with a longitudinal bore 50 slidably receiving the plunger 44. The closure plug 46 extends through the combustion chamber into contact with the surface 22 of the warhead and at least that portion of the plug extending through the annular body 26 of solid fuel is complementary in size and shape to the inner surface of that annular body so as to engage that surface when inserted in the device as shown. The lowermost flared end of the plug 46 engages the inner surface of the jet nozzle and constitutes a closure to confine primary propelling gases to the rear of the projectile during projection of the device from a gun barrel.

The bore 50 in plug 46 extends rearwardly a greater distance than the plunger 44, thus leaving a chamber between the lowermost end of plunger 44 and the bottom of the bore 50. That chamber is filled with an explosive charge 52, which may be gunpowder or the like, and a passageway 54 of reduced section provides communication between the explosive charge 52 and the rearmost face of the closure plug 46. While the primary propelling gases in the gun barrel act to propel the entire projectile from the gun, those hot gases enter the passageway 54 and ignite the explosive charge 52 to thus create a pressure in the chamber tending to eject the closure plug 46 rearwardly from the projectile. 'Ihe charge S2 is sufficiently small that it cannot effect shear or rupture of the vanes 10 or 12 but is sufficiently large to effect ejection of the plug 46 as soon as the projectile has left the muzzle of the lgun and the pressure of the primary propelling charge is relieved. Since the plug 46 engages the inner surface of the annular body 26 of solid fuel, the plug will provide support for that body of fuel and prevent its destruction or distortion by the acceleration forces produced in the gun barrel. At the same time the plug 46 provides support for the warhead 8 to prevent rupture of the vanes 10 or 12 in the same manner as described in connection with FIG. 1.

The modification shown in FIG. 3 is substantially the same as that shown and described in connection with FIG. 2 but `differs therefrom in that the inner surface of the annular body of solid fuel 26 is conical in shape rather than cylindrical. The plug 46 is complementarily conical and more readily ejected from the device without danger of tearing the body of solid fuel during ejection. y In the modification of FIG. 4 the warhead 8 is provided With a plunger 44, the same as FIGS. 2 and 3, but the closure plug 52 is of less diameter than the inner surface of the annular body of solid fuel and does not provide the support for the fuel described in connection with FIGS. 2 and 3. In this modification the body of solid fuel may be supported during acceleration by the fluid or flowable means described in connection with FIG. 1. The lower end of the plug 52 is provided With an enlarged tapered head 56, corresponding to the head 48 of FIGS. 2 and 3, and engageable in sealing engagement with the inner periphery of the nozzle 32.

Each of the embodiments shown in FIGS. 2, 3, and 4 may be further modified by providing a closure like that of FIG. l at 38 abutting against the terminal surface 34 of the casing rather than engaging the inner surface of the jet nozzle.

The embodiment of FIG. 5 provides the annular body of solid fuel 26 as described in connection with previous figures but in this embodiment the warhead 58 is a long gradually tapered body extending rearwardly and centrally of the casing tube through the combustion chamber 24 and into the nozzle 32. The forward portion of the warhead 58 is held in centrally spaced position in the casing tube by means of angularly arranged vanes It). The rear portion of the warhead 58 is held in central position by circumferentially spaced vanes 60 extending to the casing 2 at the lowermost end of combustion chamber 24. The warhead S8 is also provided with an enlarged conically tapered body 62 in the jet nozzle portion. An annular closure ring 64 is so proportioned as to snugly engage the inner surface of the jet nozzle and the outer surface of the conical body 62 to effect closure of the rear portion of the ramjet device. The closure ring 64 functions exactly as the closures described in connection with the previous figures, to confine primary propelling gases to the space behind the projectile and to provide support for the warhead 58 against the acceleration forces produced in the gun barrel. After the projectile has been ejected from the gun barrel, pressure within the forward portion of the projectile causes ejection of the closure rin-g 64 and the device then operates as described.

The modification of FIG. 5 offers further advantages in the arrangement of the vanes 10 and 60. ' I'he vanes 10 and 60 rotating relative to the air stream entering the combustion chamber and the stream of hot gases entering the nozzle produce a turbojet effect resulting in higher pressure in the combustion chamber and more efficient thrust production in the nozzle 32. In order to get the turbojet effect, vanes 10 must be positioned ahead of the combustion chamber and vanes 60 must be behind the combustion chamber. Furthermore, the enlarged conical body 62 acts to induce higher velocities in the jet nozzle, in a well-known manner.

The modification of FIG. 6 comprises essentially thc same casing 2 and annular body 26 of solid fuel as disclosed in connection with previous figures and also includes the same jet nozzle 32 and shoulder 28 merging with the jet nozzle surface at surface 3.3. The warhead I66 of this embodiment is mounted in the device for free sliding movement in a fore and aft direction through a limited range of movement. 'Ihe portion of the warhead near the forward end of the projectile is cylindrical in shape and supported centrally of the casing for sliding movement by a guide ring 68 held centralized in the casing 2 by the peripherally spaced vanes 10. The warhead 66 includes a rear cylindrical portion 70 of reduced diameter slidably guided in a guide ring 72 held in centrally fixed position in casing 2 by means of vanes 74. The rearmost portion of the warhead 66 consists of an enlargement 76 terminating in a conically tapered portion 78. Inv the forward Yposition of the warhead 66, shown in full lines in FIG. 6, the device operates as a ramjet in the same manner as described in connection with previous embodiments. When the device is placed in a gun barrel to be fired therefrom, the warhead is in its rearmost position, indicated by dotted lines in FIG. 6. In this position the enlargement 76 and/or conical portion 78 engage the surface 33 of the casing 2 to effect closure of the passageway through the projectile. The ratio of the projected area of the conical portion 78 exposed to the propelling gases in the gun barrel to the projected area of the projectile exposed to the propelling gases in the gun barrel is such that the inertia forces involved in projecting the device from a gun barrel hold the warhead in its rearmost position until the projectile has left the gun barrel. In other words, the ratio A/M (where A is the effective area of the casing exposed to propelling gases and M is the mass of the casing) must be substantially greater than the ratio A'/M (where A is the effective area of the warhead exposed to the propelling gases and M' is the mass of the warhead). The ratio A/M must be sufficiently greater than the ratio AVM to cause the casing to accelerate at a greater rate than the warhead despite the friction forces between the casing and the gun barrel.

The enlargement 76 and conical portion 78 are thus maintained in substantial sealing relation to the entrance to the jet nozzle to prevent escape of the primary propelling gases until the projectile has left the gun barrel and the acceleration force on the warhead'66 has diminished sufficiently to permit pressure Within the combustion chamber to move the warhead forwardly to its full line position.

In this modification, as also in the form shown in FIG. 5, the annular body of solid fuel may be supported during periods of acceleration by the fiowable or liquid supporting material described in connection with FIG. l. The vanes 74 of FIG. 6 also function to help support the body 26 of solid fuel against distortion during acceleration since those vanes actually pass through the annular body of solid fuel and are attached to the casing 2.

In each of the modifications heretofore described, that is, those shown in FIGS. 1 through 6, inclusive, the false breech or closure members 38, 48, 56, 64, and 76-78 may be provided with one or more small openings extending therethrough and providing communication between the jet nozzle and the combustion chamber. With such openings through the false breech or closure members, hot propelling gases may be admitted to the combustion chamber to effect early ignition of the igniter material 36 and/or the body 26 of solid fuel.

FIGS. 1 and 7 illustrate still further means for supporting the annular body 26 of solid 4fuel against distortion during acceleration in the gun barrel. In this modifcation the casing 2 is provided with inwardly directed integral projections extending into the annular body of solid fuel and providing the necessary support therefor. The projections 80 cooperate with the shoulder 28 to support the entire body of fuel. Projections 80 may be in the form of integral and circumferentially spaced projections, they may be rings extending around the entire inner periphery of the casing 2 or they may be a single helically arranged rib. Preferably, the projections are provided with transverse supporting surfaces extending in a direction substantially normal to the helix of the rifling in the gun barrel. The support provided by projections 80 may also be provided by separate bolts or pins mounted on the casing 2 or, as an alternative, the inner surface of casing 2 may be provided with suitable circumferentially extending grooves to receive portions of the annular body 26 of solid fuel. Clearly, the supporting means of FIG. 7 may be incorporated in any of the modifications shown in FIGS. l through 6, inclusive, although shown only in connection with FIG. 1, specifically.

In designing ramjet propulsion devices of the type dis- 9 closed herein, it is to be borne in mind that the space vacated by the rburned solid fuel increases the volume of the combustion chamber. Initially, the ramjet motor could be overloaded with solid fuel, leaving too small an air passage in the combustion chamber to provide optimum efficiency. After a certain working period, enough solid fuel will have been burned away to reach full efficiency. Thus, the working range could be increased. The space of the fuel ring is converted into combustion chamber space.

FIG. 8 is merely a schematic view of a projectile embodying the present invention with parts thereof corresponding to those of the modification shown in FIG. l. However, as shown in FIG. 8, a granular or fluid material 100, previously referred to, is shown in position to support the fuel 26 against shattering or fracture as a result of the high acceleration `forces encountered during firing the projectile from a gun. As heretofore stated, although FIG. 8 represents only the form of FIG. l, the uent material 100 may be used with any of the modifications heretofore described.

While a limited number of specific embodiments of the invention have been shown and described herein, it is to be understood that the invention is not limited thereto but encompasses all modifications and embodiments falling fairly within the scope of the appended claims.

We claim:

1. A ramjet propulsion device comprising, a tubular body structure having a supersonic diffuser inlet portion, a combustion chamber and a jet nozzle, the inner surface of said combustion chamber comprising an annular self-sustaining body of solid combustible material, transverse closure means for said nozzle abutting a rear portion of said tubular body, and a mass of iiowable material substantially filling said combustion chamber and said nozzle, whereby to prevent distortion or fracture of said body of combustible material upon acceleration of said device by a force applied to said closure.

2. A ramjet projectile comprising, a relatively short generally cylindrical open-ended hollow body structure having a supersonic diffuser inlet portion at its open forward end, an intermediate combustion chamber, and a rearwardly directed jet nozzle, a solid annular body of combustible material lining said combustion charnber, a warhead positioned centrally within and spaced from said cylindrical hollow body forwardly of said combustion chamber, and circumferentially spaced means supporting said warhead centrally within said hollow body, said means including vanes forwardlyof said cornbustion chamber, fixed to said cylindrical hollow body and positioned angularly relative to the axis of said projectile whereby said vanes serve to direct air flowing therepast in a manner to increase the pressure thereof in said combustion chamber.

3. A ramjet projectile comprising, a generally cylindrical hollow body structure having an open forward end, an intermediate combustion chamber, and a rearwardly directed jet nozzle, a supply of combustible material in said combustion chamber, a warhead and circumferentially spaced means holding said warhead positioned centrally within and spaced from said hollow body forwardly of said combustion chamber, said warhead having `a rearwardly facing surface, a transverse closure member loosely fitted to a portion of said projectile rearwardly of said combustion chamber, and a compression member extending forwardly from said closure through said combustion chamber into contact with said rearwardly facing surface.

4. A projectile as defined in claim 3, wherein said closure member comprises a member complementary to and peripherally engaging the inner surface of said jet nozzle.

5. A ramjet projectile comprising, a generally cylindrical hollow body structure having an open forward end, an intermediate combustion chamber, and a rearwardly directed jet nozzle, a solid annular body of combustible material lining said combustion chamber, a warhead and circumferentially spaced means holding said warhead positioned centrally within and spaced from said hollow body forwardly of said combustion chamber, said warhead having a rearwardly facing surface at its rear end, a closure member loosely abutting the rear end of said projectile, and a compression member extending forwardly from said closure through said nozzle and combustion chamber into contact with said rearwardly fac ing surface.

6. A ramjet projectile comprising, a generally cylindrical hollow body structure having an open forward end, an intermediate combustion chamber, and a rearwardly directed jet nozzle, a solid annular body of combustible material lining said combustion chamber, a warhead and circumferentially spaced means holdin-g said warhead positioned centrally within and spaced from said hollow body forwardly of said combustion chamber, said warhead having a rearwardly facing surface, a transverse closure member loosely fitted to a portion o-f said projectile rearwardly of said combustion chamber, a support member extending forwardly from said closure member and into contact with said rearwardly facing surface, said support member being complementary in size and shape to the inner surface of said annular body of combustible material whereby to physically support said body against distortion or fracture upon acceleration of said projectile.

7. A projectile as defined in claim 6 wherein said closure comprises a member complementary to and fitting the inner surface lof said jet nozzle.

8. A ramjet projectile comprising, a generally cylindrical hollow body structure having an open forward end, an intermediate combustion chamber, and a rearwardly directed jet nozzle, a supply of combustible material in said combustion chamber, a warhead and circumferentially spaced means holding said warhead positioned centrally within and spaced from said hollow body forwardly of said combustion chamber, said warhead having a rearwardly facing surface, a transverse closure member loosely fitted to a portion of said projectile rearwardly of said combustion chamber, and a compression member extending forwardly from said closure through said combustion chamber into contact with said rearwardly facing surface, said compression member having a bore extending rearwardly therein, said warhead being provided with a rearwardly extending plunger slidably received within said bore, an explosive change in said bore rearwardly of said plunger, and a small passageway providing communication between the portion of said bore containing said charge and the rearmost face of said closure.

9. A projectile as defined in claim 8, wherein said combustible material comprises an annular norm-ally selfsustaining body of said material lining the inner wall of said combustion chamber 'and wherein said compression member is complementary in size and shape to the inner surface of said annular body of combustible material whereby to engage said surface and support said body against distortion or fnacture upon acceleration of said projectile.

10. A ramjet projectile comprising, a generally cylindrical hollow body structure having an openforward end, an intermediate combustion chamber, and a rearwardly directed jet nozzle, a solid annular body of combustible material lining said combustion chamber, and a warhead positioned centrally within and spaced from said cylindrical hollow body, said warhead extending rearwardly from the open forward end of said body through said combustion chamber, circumferentially spaced vanes supporting said warhead centrally within said hollow body and being fixed to said hollow body, said vanes being arranged angularly relative tothe axis of said projectile,

certain of said vanes being positioned adjacent to the forward open end of said hollow bod-y and others of said vanes being positioned between said combustion chamber and said jet nozzle whereby to impart rotary motion to gases moving to said nozzle.

11. A ramjet projectile adapted to be projected from a gun by the `action of primary propelling gases therein and comprising, a hol-low tubular body structure having a supersonic diffuser inlet portion 'at the forward end thereof, a combustion chamber communicating with Said inlet and a jet nozzle at the rear of said combustion chamber, the inner surface of said combustion chamber comprising an annular self-sustaining body of solid combustible material, a warhead positioned centrally within and spaced from said cylindrical hollow body, movable transverse closure means loosely closing said hollow body adjacent the rear portion thereof rearwardly of said combustion chamber to prevent passage of said primary pro- 12 pelling gases forwardly into Vsaid combustion chamber, said closure means being arranged, when in closing position, to transmit forward acceleration forces, produced thereon by said primary propelling gases, directly to said warhead.

References Cited in the le of this patent UNITED STATES PATENTS

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