Disposal of encased explosives

Nov. 5, 1963

3,109,369

H. J. PLUMLEY

DISPOSAL OF ENCASED EXPLOSIVES

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Nov. 5, 1963

3,109,369

H. J. PLUMLEY

DISPOSAL OF ENCASED EXPLOSIVES

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3,109,369

Patented Nov. 5, 1S63

United States Patent Office

3,109,369

DISPOSAL OF ENCASED EXPLOSIVES Harold J. Plumley, 2364 Skyland Place,, Washington, D.C.

Filed May 31,1944, Ser. No. 538,173

Claims. (Ci. 102—1) (Granted under Title 35, U.S. Code (1952), sec. 266)

This invention relates to the disposal of explosive-bearing ordnance by techniques involving either a simple burning of the explosive charge in air, tbe necessary oxygen being supplied by the air, and/or by a self-sustaining reductive reaction requiring no air or oxygen supply, and which may accordingly be effected under water.

An important object of the invention is to provide improved means whereby the explosive charges of bombs, mines, depth charges and other explosive-bearing ordnance may be removed in a quick, simple and efficient manner, with the least possible risk of high order detonation.

Another object is to provide such means which requires, in order to effectuate the removal of the explosive charge, only relatively light, compact and easily portable apparatus, and which, further, involves the use of apparatus which may be operated from a safe distance and which may be set up without creating such mechanical disturbance or magnetic effect as might initiate an unwanted detonation in event the ordnance should be equipped with anti-magnetic and/or anti-disturbance devices or the like.

While dangers and difficulties have been encountered in depotentiating such items of ordnance on land, the problems are greatly aggravated in dealing with underwater ordnance. In fact it has usually been considered impossible to render mines and the like safe under water otherwise than by detonating them. Attempts to move or raise a ground mine from the bottom usually result in its firing, since acoustic or magnetic anti-disturbance devices, or both, are usually present. Hydrostatic switches which fire the mine upon the decrease of water pressure which, occurs when it is raised are also very commonly fitted. Although in principle a diver might render safe certain of the more simple ground mine devices under water, as by removing the detonator, blocking the hydrostatic switch, etc., the hazard of this work is obvious, and is prohibitive in a practical sense, because of the poor visibility and difficult working conditions, and the lack of complete access to the mine, which is usually partially buried in the sea bottom. Removal of the fuze or detonator, or both, may also be prevented by the inclusion of anti-withdrawal devices, and the removal of these devices may also be impossible because of their inaccessible positioning, as indicated, particularly if the mine is imbedded in the sea bottom. “Booby traps” are also used to prevent disturbing these elements without firing the mine. When it is considered in addition that such mines are usually fitted with live acoustic devices arranged to cause the mine to fire in event of any substantial noise in the vicinity, it will be understood that rendering such mines safe, by means entailing the performance of any substantial amount of manual work thereon, is virtually impossible.

Since some of the same considerations obtain with respect to efforts to render harmless bombs, mines, etc., located above ground, it has become increasingly common practice to render them safe by removing the main charge. Above ground this may be done by steaming out the main charge, by the use of solvents, by washing out the charge, or by burning. Any of these procedures are impractical beneath the water.

The present invention also includes among its objects, therefore, the overcoming of the indicated difficulties, and the entirely safe destruction of explosive-bearing ordnance under the difficult conditions outlined.

Another object of this invention is to provide such means involving a construction formed entirely of nonferrous materials, which may be loaded with non-magnetic Thermit, so that danger of firing a mine or other g explosive device equipped with magnetically responsive elements is eliminated.

Another object is to provide such a mechanism which is capable of withstanding the great thermal shock involved in the rapid development of a thermal gradient , „ of about 4000° F. across the wall thickness of the unit, and the rapid cooling effect of the surrounding water.

Another object is to provide such a mechanism having delay means adapted to prevent the release of the Thermit until approximately 15 seconds have elapsed after _lg ignition of the charge, to insure that the Thermit reacts with reasonable completeness before such reaction is stopped by release of the molten iron.

Still another object is to provide electric ignition means, and to protect the electrical lead-in and other means as₂₀ sociated therewith against the high pressures which may be involved and which may be applied from either or both sides.

Still another object is to provide such a mechanism incorporated in a simple, unitary compact construction ₂g which is absolutely waterproof to depths of at least 200 ° feet, and which is capable of withstanding the considerable internal pressures developed during the reaction period. Still another object is to provide such a unit which is light in weight and which is in stable equilibrium „₀ when placed on a cylindrical or spherical surface underwater, and which is able to maintain itself in position under gravity and without special attaching means, under ordinary conditions.

Other objects and advantages will be apparent from the „ - following description taken in conjunction with the drawings forming a part of the present disclosure.

In the drawing, in which like reference characters designate similar parts throughout the several views:

FIGURE 1 is a perspective view of a mine to which is shown attached a preferred means for initiating self-destruction in accordance with the present invention;

FIGURE 2 is a vertical, substantially diametric crosssection of the initiating device, taken substantially on the line 2—2 of FIGURE 1 and looking in the direction of the arrow;

FIGURE 3 is a sectional detail taken substantially on the line 3—3 of FIGURE 2 and looking in the direction of the arrow;

FIGURE 4 is a perspective view of a bomb, together with rigging, and an initiating device supported by the rigging, such devicve being of somewhat modified construction;

FIGURE 5 is a vertical substantially diametric sectional view taken substantially on the line 5—5 of FIGURE 4 _rr and looking in tire direction of the arrow;

FIGURE 6 is a vertical substantially diametric crosssectional view of a unit constructed in accordance with the present invention and suitable for underwater use, showing the same in position upon a mine case, which is θ fragmentarily illustrated; and

FIGURE 7 is a view partly in top plan and partly in cross-section taken substantially on the line 7—7 of FIGURE 6 and looking in the direction of the arrow.

I have found that if the high explosive charge contains aluminum or some other reducing agent, a slow, self³⁵ destructive reaction may be initiated under water as well as above ground, by exposing the charge to a temperature of about 2500° F. for a short time, and that furthermore, such self-destructive reaction will continue and spread throughout the charge, destroying it completely with no danger whatsoever of causing detonation, of any part of the charge. The essential feature of this reaction is ap

3,109,369 parently the progressive reduction of the nitrated organic constituents of the explosive by the metallic aluminum. The solid end product is a porous ash, a typical sample of which has been found to be composed of 94% aluminum oxide and 6% carbon. Ammonia is prominent among the gaseous end products of the reaction. Apparently the necessary and sufficient condition of the initiation of this reaction is the presence in the high explosive of between 10 and 50% of any finely divided metallic reducing agent such as aluminum, magnesium or zinc. Aluminum is the most commonly used agent, and since the aluminizing of exposives for underwater ordnance results in such a wellestablished enhancement of explosive power, the use of such material will probably be continued, or at least the use of some comparable reducing agent which will afford the same possibility of destroying the charge by my improved method.

I have also found that non-violent self-destruction of explosives under water may be made to occur by another type of reaction which differs from the above described auto reduction in that it takes place in certain explosives which are entirely free of metallic reducing agents and the end products of which seem to be entirely gaseous, no ash whatever being left. This reaction is apparently a slow exothermic decomposition started by local heating of the charge, and it progresses automatically due to the heat yield of the reaction. Thus far it has been determined that the condition for the sub-surface auto-decomposition reaction in this manner is the presence in the explosive of either hexanitrodiphenylamine or cyclonite. This reaction also occurs without violence and with a rate of gaseous discharge which is entirely moderate.

In accordance with my preferred method, the case of the explosive-bearing ordnance is penetrated and charge ignition initiated, in a single operation, by allowing a pool or jet of molten iron, obtained from a Thermit reaction, to contact or impinge upon the mine or bomb.

FIGURES 1, 2 and 3 show a suitable Thermit crucible adapted to be used in air, by placing the same upon the case of the item of ordnance to be depotentiated. The Thermit may be fired from a distance by means of a squib which is electrically operable. Preferably no magnetic materials are used in the construction of the crucible, and hematite base Thermit is used, since it is non-magnetic, unless it is certain that the mine or other ordnance is so designed that it is not sensitive to magnetic materials, in which event black magnetite base Thermit may be used, since it affords greater burning speed.

In the embodiment of FIGURES 1, 2 and 3, a unitary Thermit burning charge 15 is housed in a container formed of a cylindrical tube 1 surrounded by a cylinder, 2, of Transite or the like and closed at its upper end by a dished plate, 4, which carries centrally depending from its bottom a cupped container, 5, in which is housed a booster charge, 7. A firing squib, 9, carried by the top plate, 4, projects into the booster, and is adapted to be connected as by the wire, 18, to electrical firing means, not shown, whereby the device may be fired from a safe distance. The container is closed on the bottom by a cupped reentrant wall, 12, fitted into the tube, 1, and preferably secured thereto by cement, to retain the Thermit burning charge, 15. An asbestos ring, 17, controls the area of the molten iron stream which is first discharged against the case, and the bottom wall delays for a slight and desirable interval the access of the material to the case of the mine or other ordnance, allowing the Thermit reaction to be well initiated before the material is released. If the assembly is formed of cylindrical tubular parts, in the manner indicated, it will be apparent that it will be stable when placed upon spherical surfaces within a wide range of radii and that the lower end of the container will make good contact with such surfaces. If the article to be de-armed, however, is of some other configuration, as in the case of the cylindrical mine illustrated, the gaps between the lower edges of the Thermit unit and the mine case may be sealed as by means of a clay or sand pack to retain the molten iron for a sufficient length of time.

When the unit is fired, the Thermit reaction creates a 5 pool of molten iron on top of the case, having an area of approximately 50 sq. in., which area of the case is heated to the melting point of iron, producing an opening roughly equal in area to the cross-section of the burning charge. It has been found, however, that this type of 10 Thermit unit is best used so as to allow the pool of liquid iron to form, that is, it should not be placed on the side of a mine, nor should it be supported above a mine, or placed on an object of curvature or radius so small as to allow some of the material to escape. The operation 15 of such a unit further seems to be limited to steel case thicknesses of not greater than .25.

In order to perform a similar operation upon mines having thicker cases and/or different shapes, I have provided a modified technique which involves the use of a 20 crucible unit designed to discharge a greater quantity of molten iron, in a smaller stream, against the case to be entered. The construction of such a unit is illustrated in FIGURE 5, and a suitable manner of supporting it in operation is indicated in FIGURE 4. Preferably the 25 vent of the crucible should be located from 2 to 4 inches above the surface or case, and somewhat off-center, so that the stream of iron will impinge on a sloping surface. For steel case thicknesses up to and including .375, a six to ten-pound Thermit charge has been found to be ade30 quate. As shown in FIGURE 5, the refractory crucible, 1A, is open at its top, the bottom being formed with a relatively small discharge opening, 20. The crucible may be enclosed in a sheet metal container as 2A, having a sheet metal bottom cap, 12A, adapted to be melted 35 through after retaining the Thermit material and molten iron until the reaction is well initiated. The firing squib, 9A, and booster charge, 7A, are indicated on top of the main charge, and as shown in FIGURE 5, the crucible assembly may be supported upon a simple scaffold gen40 erally designated 22. Electric leads, 10A, permitting operation from a safe distance may be connected to suitable electrical firing means (not shown).

When the charge is ignited, it first burns a hole in the bomb case and then enters the interior, igniting the ex45 plosive content. Explosive materials of the ordinary types used in ordnance burn relatively quietly when so ignited. If the charge contains aluminum or other metallic reducing agents, the reaction may, rather than an ordinary burning, consist of an auto reduction reaction with 50 formation of aluminum oxide and gas as mentioned above in connection with underwater disposal. If no reducing agent is present, as in 'the case of pure TNT, the material may be destroyed by straght burning at the orifice created in the case. The action is regenerative, that is, a part of 55 the flame serves to heat the charge and the container, in turn maintaining volatilization of the explosive and feeding the flame. This continues until the bomb or mine is completely empty or until the reaction is stopped by some sort of low order detonation. Such detonations 60 may occur near the end of the burning, and usually, when the charge has been reduced to· such proportions that danger of any substantial destruction by such detonation is virtually eliminated.

In the underwater embodiment of FIGURES 6 and 7, 65 the cylindrical case, IB, is preferably formed of insulating material having great resistance to thermal shock and considerable mechanical strength. The best material thus far found for this use is sold under the trade name “Transite.” Such material is also easy to fabricate and 70 machine. Top and bottom closure plates, 4B, 12B, respectively, may be bolted in place, as shown, to secure the Thermit charge, 15B, which is preferably formed of nonmagnetic hematite. The closure plates project radially beyond the remainder of die casing and are perforated 75 in vertical alignment, to receive supporting rods 22B.

3,109,369

Rods 22B are pointed at their lower ends and project below the assembly to support the same, being adjustably attached by means of manually operable clamping screws 23B. An annular or refractory frustoconic bottom portion 17B, arranged directly above the bottom plate 12B, defines the effective size of the discharge opening 20B. This opening is closed by a thin brass plate 13B which quickly burns through when the molten iron is discharged, additional delay being interposed by ’the use of a thin layer of slow-burning bonded Thermit, 16B. It will be apparent that the thickness and characteristics of this layer may be varied to provide any desired delay.

A booster charge 7B, housed in a can 5B, is suspended in the Thermit charge by means of a strap 25, an electrically operable firing squib, 9B, being arranged in the can 5B. The electrical connection to the squib is provided through the top plate, 4B a pressure resistant connector, 24, being provided at this point having a suitable terminal at its outer end to which the lead 10B may be connected as shown.

The development of unduly high internal pressures within the unit is prevented by the use of a simple oneway piston valve, consisting of a piston element, 27, housed in cylinder, 29, connected to the top of the unit and communicating with the interior thereof via passage, 30. A soft rubber gasket, 32, is arranged between the piston, 27, and the shoulder 31 formed by the counterbored portion of the cylinder, 29, in which the piston is housed, the piston being tightly held against the cylinder by the cotter pin, 33 which is removed before firing, the piston thereafter being held in place by hydrostatic pressure. Alternatively, the piston, 27, and gasket, 32, may be cemented together, and against the .shoulder, 31, space being left between the piston, 27, and cotter pin, 33, and the fit of the piston being loose enough to permit escape of pressure therearound when it is unseated and the cement seal is broken.

The piston may be forced off its seat by sufficient internal pressure. In the arrangement first described, when the internal pressure rises sufficiently, the piston is discharged from the opening and entrance of sea water is prevented during the reaction by the continuous gaseous discharge.

In operation, the device is simply positioned upon the mine or other device to be entered, and fired from a safe distance. The unit generates a pool of molten iron, as will be readily apparent, and releases it in a jet against the case upon which the device is positioned. The molten iron melts its way into the interior of the case and initiates the above described reaction, which progresses until the explosive charge is destroyed.

In view of the fact that acoustically operable mines, which might be detonated by the firing of the squib and booster of my mechanism, are usualy also equipped with anti-countermining devices arranged to prevent detonation if the noise is in the form of a sufficiently loud report, I preferably also fire a detonator or other small quantity of explosive simultaneously, to actuate the anticountermining means. This supplemental, “paralyzing” charge, such as 40', FIG. 6, may of course be fired against or close to the mine by the same wiring and electrical means, its squib being simply connected in parallel with the squib 9, 9A or 9B.

It will be apparent that when the technique herein described is use, it is not necessary for personnel to be near the explosive ordnance for more than a very short length of time. Neither is it necessary to disturb the mine or bomb, so that danger of accidental detonation is virtually eliminated.

The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.