US3780576A - High energy slurry explosives - Google Patents

Abstract

A method of testing the uniformity of liner effectiveness. Randomly selected shaped bomblet cases are uniformly filled with a slurry explosive. The cases are fired into armor plate targets and the relative uniformity of penetration between bomblet cases is measured.

Description

United States Patent [1 1 Mallory HIGH ENERGY SLURRY EXPLOSIVES [75] Inventor: H. Dean Mallory, China Lake, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

22 Filed: Aug. 30, 1971 21 App1.No.: 176,265

[52] US. Cl.

[51] Int. Cl. G011 5/14 [58] Field of Search 73/35, 167; 149/91,

[56] References Cited UNITED STATES PATENTS 3,194,066 7/1965 Schwab et a1 73/167 [4 Dec. 25, 1973 2,459,156 1/1949 Ferguson 73/167 3,378,416 4/1968 Perry et a1. 149/22 3,356,544 12/1967 Fee et a1. 149/91 3,515,604 6/1970 l-lamrick 149/92 Primary Examiner-Herbert Goldstein Att0meyR. S. Sciascia et a1.

[5 7 ABSTRACT 2 Claims, No Drawings 1 HIGH ENERGY SLURRY EXPLOSIVES BACKGROUND OF THE INVENTION The present standard for high energy, castable explosives is Octol which is a binary composition of Cyclotetramethylenetetranitramine (HMX) crystals in a matrix of TNT. It is made by mixing the high melting point HMX crystals with molten TNT. The hot slurry is then poured or cast into molds or into bomb cases, etc., and allowed to cool so the TNT solidifies. This produces a solid casting. The principle involved is: before the TNT is solidified, the explosive consists of uncompressed HMX crystals with all the intercrystalline air displaced by molten TNT. HMX is also known as homocyclonite or 1, 3, 5, 7 tetranitro -l,3,5,7 tetrazacycle-octane.

Castable explosives which solidify upon cooling or which harden during storage have the disadvantage of shrinking, cracking, etc. which is a degrading factor especially noticeable in certain types of warheads.

The use of unpolymerized PBXN-lOl, for example, in some warheads is not satisfactory since the material will slowly polymerize in storage and become hard. Hardening of the explosive is not desirable since warhead function may thereby be impaired to the extent that it becomes inoperable. The Octathane or Cyclothane explosives according to this invention do not become hard in storage but rather retain their slurry characteristics.

Another advantage of Octathane type explosives over unpolymerized PBX N-lOl is that the PBXN-lOl must be premixed before the slurry is poured into the warhead. The requirement for premixing requires the slurry to be pourable which automatically limits the proportion of HMX that can be incorporated in the mixture; this sets a limit on the energy output.

The Octathane explosives have no such limitation since the solid component can be loaded dry or in a partially wet state and the remainder of the liquid nitromethane added at a later stage. This loading method can be used because liquid nitromethane or its energy enhanced counterpart has low viscosity and readily wets or soaks into the solid crystal load and displaces the air. The crystals have a blotter action for nitromethane.

Octol is normally considered as a castable mixture of HMX and TNT. To more easily understand this invention, it is helpful to visualize Octol as a gravity packed HMX charge with the interstitial air displaced by molten TNT which later freezes and produces the solid Octol charge. The interstitial air can be displaced by any compatible liquid or liquified substance. If the liquid is nitromethane, the resultant product is Octathane. If the liquid is molten TNT, the resultant product is Octol. Since nitromethane is less energetic than TNT, Octathane is less powerful than Octol. However, the power of Octol could be exceeded by the use of nitroglycerine or molten TNETB (m.p. 93C) or BTNEN (mp. 945C) as the liquid.

SUMMARY Only two of these mixtures have been given special names: HMX with nitromethane (Octathane), and cyclotrimethylenetrinitramine (RDX) with nitromethane (Cyclothane). RDX is also known as hexahydro -l,3,5 trinitro-S-triazine, cyclonite, hexogen and T4. The low viscosity of nitromethane gives these particular explosives the property of easily reproducible loading which is important to the present method and which can, only with great effort, be achieved with Octol or Composition B. This reproducibility of loading makes such slurry mixes very useful in the testing of shaped charge devices of new design before entering into full scale production.

The sensitivity of Octathane type explosives can be changed by adding a few percent of sensitizing or desensitizing liquid to the nitromethane liquid phase as is already known to the art. Amines will sensitize and benzene will desensitize nitromethane. Nitromethane can also be sensitized by the addition of nitric acid or tetranitromethane.

Any solid explosive can be used in place of HMX or RDX as the solid phase. However, for high energy output, these materials are preferred.

Any explosive or near-explosive liquid of reasonably low viscosity can be used in place of nitromethane to displace the intercrystalline air of the solid phase. It is of course assumed that the liquid and solid phase are chemically compatible. Other liquids might at times be desirable to change the sensitivity or volatility of the final composition.

DESCRIPTION OF THE INVENTION The basic Octathane explosive consists of HMX crystals with the intercrystalline air displaced by liquid nitromethane. Sufficient liquid nitromethane is used to just displace the intercrystalline air in order to give the highest possible amount of HMX both for the high energy potential of the final explosive, and to prevent settling out of HMX crystals in the charge. Used in this way, the nitromethane willdissolve some of the HMX. This can be prevented, if so desired and in many cases it will be so desired, by saturating the nitromethane with HMX before it is added to the HMX to make the Octathane.

In the basic formulation, Octathane will be slightly less energetic than Octol because the nitromethane used to displace intercrystalline air is less energetic than TNT. However, an energy enhanced Octathane can be made by dissolving RDX in nitromethane (nitromethane will dissolve a small amount of RDX) and using this solution to formulate the Octathane. Other explosive or energetic nitrated materials of greater solubility than RDX may'be dissolved in the nitromethane to increase its energy. However, the solution of large quantities of other materials in the nitromethane may overly increase its viscosity making it more difficult for the liquid to displace the intercrystalline air of the HMX.

Instead of Octathane (HMX and nitromethane) a similar but lower energy explosive, Cyclothane, can be made by combining RDX crystals with nitromethane (with or without the prior solution of RDX in the liquid nitromethane). If the nitromethane is used without previously saturating it with RDX, some of the RDX will dissolve in the liquid nitromethane after the components are mixed. An indication of the degree of solution can be gained by noting that the density of nitromethane is 1.129 (2 3/4 g/ml and the density of HMX saturated nitromethane is 1.132 (2 3/4) g/ml and the density of RDX saturated nitromethane is 1.145 (2 3/4) g/ml.

UTILITY The use of an explosive mixture according to the present invention can best be illustrated by a description of the operations performed in loading and testing cone shaped cluster bomblets with copper liners for reproducibility of said liners. Through an open port above the cone apex, nitromethane was poured in until the bomblet case was half full. Dry, class A, HMX was then sifted in with tapping to dislodge air bubbles. Since nitromethane is a thin, mobile liquid of much lower density (1.13 g/cc) than HMX (1.90 glcc), the HMX crystals quickly sink to the bottom of the container, shedding air bubbles as they drop. This results in very well packed HMX around the cone where loading reproducibility is so important for test purposes. There is no tendency toward segregation as in Octol since nitromethane cannot hold HMX in suspension as can the more viscous, higher density, molten TNT. HMX was added until it reached the top of the charge; any excess liquid was blotted up with a paper towel.

The bomblets were then fired at probe standoff into armor plate targets. Firing was done without the usual impact sensing element and fuse wire running from the probe to the base fuse. Test results, therefore, showed the reproducibility of two things l) the explosive load,

and (2) the copper liner. A group of 6 bomblets so detonated gave the following mean penetration and stan- 4 dard deviation:

i 7.12 inches i 0.46 inches.

These results were confirmed by loading and firing a second group of 19 production run bomblets. These gave 7.21 inches :t 0.48 inches.

Given the controlled uniformity of the explosive charge, the relatively small deviations in penetration indicates the uniformity in performance of the production reen copper liners. What is claimed is: 1. A method of testing uniformity of liner effectiveness in shaped charge explosive devices comprising:

uniformly filling randomly selected shaped charge bomblet cases having copper liners with a slurry explosive selected from the group consisting of HMX with nitromethane and RDX with nitromethane;

firing the cases so filled at a predetermined stand-off into armor plate targets; and

measuring the degree of penetration of the target material and relative uniformity of penetration between bomblet liners.

2. The method of claim 1 wherein the explosive mix consists of HMX and nitromethane and wherein the bomblet casing is half filled with nitromethane and thereafter dry crystalline HMX is sifted in while tapping to dislodge air bubbles.

Claims (2)

1. A method of testing uniformity of liner effectiveness in shaped charge explosive devices comprising: uniformly filling randomly selected shaped charge bomblet cases having copper liners with a slurry explosive selected from the group consisting of HMX with nitromethane and RDX with nitromethane; firing the cases so filled at a predetermined stand-off into armor plate targets; and measuring the degree of penetration of the target material and relative uniformity of penetration between bomblet liners.

2. The method of claim 1 wherein the explosive mix consists of HMX and nitromethane and wherein the bomblet casing is half filled with nitromethane and thereafter dry crystalline HMX is sifted in while tapping to dislodge air bubbles.