US3477373A - Underwater demolition package - Google Patents

Description

Nov. 11, 1969 I c. w. FALTERMAN ET 3,477,373

UNDERWATER DEMOLITION PACKAGE Filed April 4, 1968 INVENTORS. CHARLES W. FALTERMAN WILLIAM J. GRIFFITH ROY MILLER ATTORNEY.

United States Patent O 3,477,373 UNDERWATER DEMOLITION PACKAGE Charles W. Falterman, China Lake, and William J. Griffith, Inyokern, Califi, assignors to the United States of America as represented by the Secretary of the Navy Filed Apr. 4, 1968, Ser. No. 718,763 Int. Cl. F42b 1/04 U.S. Cl. 102-24 2 Claims ABSTRACT OF THE DISCLOSURE The invention herein describedmay 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.

BACKGROUND OF THE INVENTION This invention relates to an underwater demolition package having its buoyancy adjusted so as to be easy for swmimmers to handle at ocean depths.

Standard underwater demolition kits known to the art are negatively buoyant in water and thus diflicult to handle. Air bladders have been and are presently used to reduce the negative buoyancy, but since air is very compressible, the buoyancy of :the kits varies greatly as a function of ocean depth. The flotation bladders are cumbersome thereby limiting the number of packages or kits one man can carry. The present invention provides a compact, neutrally buoyant demolition package several of which may be carried by one swimmer.

SUMMARY OF THE INVENTION The present invention is for a neutrally buoyant underwater demolition package useful at ocean depth to 200 feet.

The ordnance items in use today which are deployed through the water are for the most part of World War II or prior with few improvements during the last twenty years. It is therefore an object of the present invention to provide an improved demolition package or assembly giving the swimmers who are the counterpart of the Special Forces Agency-trained Green Berets new and improved capabilities.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view of the demolition package in accordance with the present invention;

FIG. 2 is a section taken through 2-2 of FIG. 1;

FIG. 3 is a view partly in section of a charge used in accordance with this invention; and

FIG. 4 is a longitudinal section of an embodiment of a charge which is used in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing there is shown in FIG. 1 the underwater demolition assembly or package designated generally by numeral 10 which comprises a haversack 11 packed with a plurality of individual demolition charges 3,477,373 Patented Nov. 11, 1969 ICC or billets 12 which have been adjusted to a neutral buoyancy. Haversack 11 has an overlapping flap 13 held in place by a flap tie 14. The haversack is made of gray cotton canvas treated to be waterproof, fireproof and mildewresistant. It is provided with a shoulder strap 15 which is equipped with a snap hook 16 and fastener 17 making it adjustable to any length between 20 and 50 inches. Have'rsack 11 has a pocket 18 on the back which holds a plurality of synthetic foam strips 19 (shown in section in FIG. 2) which make haversack 11 neutrally buoyant in seawater to a depth of 200 feet. Assembly 10 can be lashed to an obstacle with the ten foot cotton securing sash cord 20 shown attached to one side of the haversack. In FIG. 2 there is shown an arrangement of synthetic foam inserts or strips 19 in the flotation pocket 18 which is an integral part of the haversack. The synthetic foam used in both the flotation pocket and in the billets to provide neutral buoyance consists essentially of expanded, closedcell polyurethane foam which is formed by the treatment of a polyester (e.g., of glycerine and adipic acid) with a diisocyanate to form isocyanate groups (-NCO) at the ends of the polymer chain. Other synthetic foams may be used such as polystyrene. The foam sections were coated with a low viscosity room temperature vulcanizing (RTV) silicone rubber (dimethylsilicone) which had a water absorption percent of zero after 7 days immersion at 77 F. This coating technique effectively kept water absorption at a minimum. A polyurethane foam piece having a density of 0.14 g./cc. or about 9 lbs./ft. coated with the silicone rubber during a 6 hour period at a pressure equivalent to 200 feet ocean depth showed water absorption of less than 1% by weight.

The billets or demolition charge-s 12 were adjusted to a neutral buoyancy to provide proper buoyancy for the assembly or package. There is shown in FIG. 3 charge 12 which comprises a lamination consisting of a single longitudinal layer of synthetic foam 21 and a corresponding layer of plastic explosive composition 22. The two layers are pressed together, and one end portion of a length of detonating cord or explosive lead 23 is positioned through the center of the charge 12. Charge 12 is fitted snugly into a canvas charge bag 24 and the length 'of explosive lead 23 extends through an eyelet 25 provided on the top of the charge bag and is looped under webbing 26 on one face of the charge bag. Each charge bag 24 has a securing sash cord attached (not shown) and looped under a securing web on the other face of the charge bag. Thus, the charge and bag can be lashed to an obstacle by the swimmer. In FIG. 4 there is shown a section of another embodiment of a charge or billet 12 pressed from an explosive composition into a section 22 about 6.6" long. Two synthetic foam sections 21 about 2.75" long and of the same dimensions as section 22 were cut and placed in abutting relation to each end of explosive section 22. A length of detonating cord (not shown) was positioned in the center of section 22 before pressing and then extended through the end sections 21. The charge was then packed into the canvas charge bag 24 for placement in the demolition package.

The same foam used to make the haversack buoyant was used to make the billets buoyant. The explosive compositions may vary in accordance with the need. Explosive compositions C-3 and C-4 were used herein. They can be shaped by hand have great shattering power. Composition C-3 contains 78:2 percent cyclotrimethylenetrinitramine (RDX) and 22:2 percent explosive plasticizer consisting of mononitrotoluene, trinitrotoluene, tetryl, and nitrocellulose.-Composition C-4 contains 91 percent cyclotrimethylenetrinitramine, 2.1 percent polyisobutylene, 1.6 percent motor oil, and 5.3 percent di-(2- ethylhexyl)sebacate. These and other suitable explosives are described in detail in the manual designated 3 TM9-1910/TO-11A-1-34, entitled Military Explosives by the Departments of the Army and the Air Force, April 1955. Composition C-3 has the consistency of putty at room temperatures between -20 F. and +125 F. It is about 1.35 times as powerful as TNT. As the explosive charge is tightly packed in the canvas charge bag, it cannot be molded into any desired shape. It can, however, be bent or curved into close contact with a surface that The detonating cord or explosive lead 23 is inserted into the body of billet 12. A conventional detonating cord consisting of pentaerythrite tetranitrate (PETN) and lead azide wrapped in a plastic tubing was used. Various lightweight detonating cords of satisfactory size may be used.

In the practice of this invention several available haversacks about 12" x 6" x 12" were made neutrally buoyant by replacing the air bladder with eleven pieces of silicon rubber-coated polyurethane foam. This reduced the immersed weight approximately 6 /2 pounds to pound.

After remaining underwater for 3 days, the immersed weight had increased to pound. Tests on the individual components of the system showed that the coated foam and explosive which formed the billets or charges gained very little weight when water soaked for 4 hours, while the canvas portions could be expected to gain about of a pound.

Component parts of the demolition package were soaked in water. It was found that in 1 /2 hours the immersed weight of the explosive charge (308 grams) had increased 3.5 percent, while the immersed weight of the canvas sack (38 grams) had increased by 37 percent. A large canvas sack (401 grams) increased by 23 percent. After 2 /2 hours the explosive charge (308 grams) had increased 47 percent, while the large canvas bag (401 grams) had increased 35 percent. The increase in immersed weight of the canvas portions of the haversack accounts for an increase of about of a pound.

Tests were conducted on the coated and uncoated synethetic foam samples having a density of 9 pounds per cubic foot. One of each sample was pressurized in salt water to 90 p.s.i., then 140 p.s.i., 175 p.s.i. and finally 200 p.s.i. with a hold of 15 minutes at each pressure. The uncoated sample gained about 12 percent in weight on the first cycle and then did not gain much more on continued cycling, and its volume shrunk by about one percent of original. The RTV silicone rubber-coated sample gained a total of about one percent over its original weight with a decrease of 0.87 percent in volume after all four pressure cycles.

The present demolition package or assembly can be floated on the surface of the water for towing by a swimmer. If desired, a chain of several assemblies may be connected for towing.

Personnel swimming with this improved package report ease of carrying and handling over old types. The gain in weight at 25 feet was slightly more than /2 pound.

What is claimed is:

1. An improved underwater demolition package which has its buoyancy adjusted to about one-fourth pound positive buoyancy at depths ranging from 20 to 200 feet which comprises a haversack having a pocket positioned on the back and forming an integral part thereof, a flap type closure, a strap for carrying said haversack and a sash cord for lashing said haversack to an obstacle;

a plurality of polyurethane foam strips mounted inside said pocket, said strips having been coated with room temperature vulcanizing dimethylsilicone to provide minimum water absorption;

a plurality of explosive charges each fitted into an explosive charge bag and positioned in said haversack, and each of said charges being provided with a length of a detonating cord extending into and through the end thereof, the excess of said cord being looped on one face of said charge bag.

2. The demolition package of claim 1 wherein each of said charges a consists of a lamination comprising at least one layer of polyurethane foam coated with room temperature vulcanizing dimethylsilicone and at least one layer of a plastic explosive composition composed of 7 8 :2 percent cyclotrimethylenetrinitramine and 221-2 percent explosive plasticizer consisting of mononitrotoluene, trinitrotoluene, tetryl, and nitrocellulose.

References Cited UNITED STATES PATENTS 2,682,220 6/1954 Hagensen 102-22 X 2,982,209 5/1961 Borcher 102-22 ROBERT F. STAHL, Primary Examiner US. Cl. X.R. 102-22, 97

Images