US2494026A - Projectile - Google Patents

Description

Jan. 10, 1950 N. ANDERSON 294949925 PROJECTILE Filed March 28, 1945 3 Sheets-Sheet l INVENTOR -fi e/5072 jade/son 15 6 4 ATTORNEY Jan. 10, 1950 N. ANDERSON ,4

, PROJECTILE Filed March 28, 1945 3 Sheets-Sheet 2 INVENTOR ATTORNEY 1950 N. ANDERSON 2,494,26

PRQJECTILE Filed March 28, 1945 3 Sheets-Sheet 3 INVENTOR Patented Jan. 10, 1950 UNITED 2,494,026 PRoJEc'riLE 2 Claims. 1

This invention relates to projectiles including impulse-propelled, gravity-propelled and reaction-propelled, and particularly to means for increasing the accuracy of such projectiles.

It has been the practice to equip projectiles with stabilizing fins for the purpose of holding the projectile in alignment with its trajectory, so that it will follow a predicted course as accurately as may be and neither tumble endover-end nor yaw, that is sway from side to side, both of which erratic actions cause inaccuracies of flight. This has been done with gravity-propelled projectiles or dropped bombs, with impulse-propelled projectiles fired from guns, such as mortar shells, and with reaction-propelled projectiles or rockets. All of these types of projectiles, especially those of low initial velocity, have a tendency upon being fired or launched to turn out of alignment with their trajectories. While the tail fins or stabilizing fins heretofore provided prevent excessive deviation, preventing tumbling and eventually reducing or eliminating yawing, their operation has not been as effective as has been desired. Especially the fins do not exert appreciable restoring torque until the projectile has turned or yawed thru a large angle, and hence they are ineifective to correct slight deviations. Another disadvantage is overcorrection of the deviations from the desired course. This occurs because the momentum of the projectile returning to its proper position swings it too far and carries it out of position again on the other side, due to the fact that it must travel out of alignment again through a considerable angle before the correcting force of the fins becomes effective. This permits the pro- .iectile to wobble back and forth during a large portion of its flight and seriously decreases its accuracy.

One object of my invention is to eliminate these disadvantages and increase accuracy of flight by providing means which constantly exerts on the projectile forces tending to hold the projectile aligned with its trajectory, even when the deviation is zero. This immediately tends to correct deviation.

It has also been common practice to spin projectiles about their axes to efi'ect greater accuracy. This has been attempted by the reaction of spirally placed fins in the apparent slip stream to spin the projectile. In some cases it has been found that such exposed spinning fins tend to induce or aggravate yaw and actually decrease the accuracy of the projectile. Therefore, it is another object of my invention to provide improved means for spinning that kind of projectile which cannot be fired from rifled barrels and to do so without the disadvantage of exposed spinning fins.

In the accompanying drawings:

Fig. l is a diagrammatic side elevation of a rocket provided with one form of my invention;

Fig. 2 is an enlarged side elevation of the stabilizing element indicated in outline in Fig. 1;

Fig. 3 is an enlarged section on the line 3-3 of Fig. 1;

Fig. 4 is a section on the line 4-4 of Fig. 3;

Fig. 5 is a perspective view of a single fin element;

Fig. 6 is an end elevation, as seen from the left of Fig. 2 of a modified form of the invention;

Fig. 7 is a section on the line 'l-'l of Fig. 6;

Fig. 8 is an elevation corresponding to Fig. 2 showing a modified form;

Fig. 9 is a section on line 99 of Fig. 8;

Fig. 10 is an elevation corresponding to Fig. 2 of still another form; and

Fig. 11 is an end elevation corresponding to Fig. 6 of the form of the invention shown in Fig. 10.

Referring to the drawings, a projectile which may be, for example, a rocket or a mortar shell has an explosive head Ill, a shank l l and a stabilizing tail I2. The shank lies in or along the apparent slip stream of the projectile. By apparent slip stream is meant the mass of air which the projectile pushes aside in its flight and in contact with which the projectile passes and which in being passed influences the flight of the projectile. It is that portion or mass of air which, if the projectile is considered stationary, apparently moves along the projectile near or in contact with it so that in its apparent movement it influences the flight of the projectile. The head and shank are streamlined to offer the smallest practical resistance to flight.

At the tail end of the shank and at a point along which the apparent slip stream passes I provide a symmetrical stabilizing element projecting into the apparent slip stream so that it exerts a constant and symmetrical drag or resistance to flight. This may be the surface of any regular pointed geometrical solid, that is pyramid or cone, pointed to the front, but for ease of manufacture I prefer a conical surface I3. I also prefer a cone whose elements have a low angle to its axis, for example about 21. This constant drag exerts a constant moment about the natural center of gyration of the projectile and keeps it true on its course and corrects even slight tendency to yaw.

The projectile can be used without any other stabilizing means, but in some instances I may add conventional type radial stabilizing fins I 4 projecting from the cone or from the stem, or both. These serve to provide pockets on the face of the cone and assist the stabilizing action by preventing the air slipping sidewise ofi the parts of the cone that lie nearest the trajectory in that half of the cone which is exerting drag when in a yaw. This is particularly desirable in conditions in which the initial propelling impulse is great enough and crooked enough to cause tumbling.

Where such auxiliary stabilizing fins are used, I prefer the novel form of fin shown in Fig. 5. A pair of radial fins l4 jointed at an angle of 60 by a conical bridge l and a cylindrical bridge I 6, the bridges being separated by an opening H. The conical bridges are secured to the cone l3, as by spot welding, at intervals to space the fins equally about the cone. The cylindrical bridges collectively form a cylindrical socket to receive the shank H which may be secured to the tail assembly in any suitable manner. The opening I 1 is at the circle where the cylindrical surface l6 would meet the conical surface [5, and facilitates die stamping of the fin member. The fins may be provided with the usual notches it for positioning the projectile in the launching device.

When the stabilizing element is used with projectile which can be spun satisfactorily by exterior fins disposed at an angle to the trajectory, I may incline the fins as shown in M in Fig. 8.

When the projectile is a rocket, the stem Il may form or contain a discharge orifice or nozzle 26 for propelling gases. In such instances the hollow inside of the cone forms an expansion chamber 2! continuous with the discharge orifice and connected to it. Gases flowing from the nozzle expand in the cone and exert more propelling effort on the rocket than they do without the cone. It has been found that in practice this additional effort may not only overcome the drag of the exterior surface I3 of the cone but may actually increase the velocity 5% or more.

Where it is desired to have the rocket spin on its axis without using exterior spinning fins, I provide interior fins 22 on the inside of the cone as shown in Figs. 6 and 7. These are set at any desired angle a", to the elements of the cone for example from 5 to 10 as shown in Fig. 7. Expanding propellant gases leaving the cone and flowing along the fins spin the projectile on its axis.

The invention can also be used with the folding form of fin shown in Figs. 10 and 11. The fins are preferably of the form shown at 23 and are mounted on pivots 24 secured in lugs 25 which are fastened near the outer rim of the cone in any suitable manner. When the projectile is placed in the gun or launcher the fins are folded against the action of springs 26 against the motor casing 23 so as to pass within the barrel 3.6. As the projectile leaves the barrel, the springs throw the fins outward on their pivots, and due to the impulse of the springs and air resistance, or both, they fly into the dotted line position of Fig. 10 where they are held by the stop shoulder 29 bearing against the cone l3.

The stabilizing cone can be used either with or without the exterior stabilizing fins, and either with or without interior spinning fins within the scope of my invention.

I claim as my invention:

1. In a projectile the combination of a body portion disposed in the apparent slipstream of the projectile when in flight, a drag element on the rear part of the projectile having a cylindrical portion and a conical portion projecting from the cylindrical portion, and stabilizing fin elements secured to the drag element, each fin element including a portion formed into a part of a cylindrical surface and a part of a conical surface and a pair of integral fins projecting radially from both said surfaces.

2. In a projectile the combination of a body portion disposed in the apparent slipstream of the projectile when in flight, a drag element on the rear part of the projectile having a cylindrical portion and a conical portion projecting from the cylindrical portion, and stabilizing finele ments secured to the drag element each fin 'ele-- ment including a portion formed into a part of a cylindrical surface and a part of a conical surface separated from the cylindrical surface and a pair of integral fins projecting radially from both said surfaces and connecting them together.

NELSON ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 646,569 Breath Apr. 3, 1900 667,407 Sims et a1 Feb. 5, 1901 1,994,490 Skinner Mar. 19, 1935 FOREIGN PATENTS Number Country Date 41,371 France Oct. 11, 1932

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