US3032972A - Propellants - Google Patents

Description

United States Patent 3,032,972 r p f t PROPELLANTS Ralph F. Preckel, Cumberland, Md, assignor to Hercules Powder Company, Wilmington, DeL, a corporation of *Delaware 1 r N0 Drawing. Filed Dec '21, 1956, Ser. No. 630,007

19 Claims. (Cl. 60-354) 7 This invention relates to newplatonic propellants. In

: one aspect this invention relates to a method for regulating'burning rates of platonic propellants. In another aspect thisinvention relates to propellants modified to become platonic, and to the use of phenolic compounds to, regulate plateau burning rate of the propellant. In another aspect this invention relates to platonic propellants exhibiting wider ranges of plateau burning rates than heretofore. In another aspect this invention relates to a method for regulating plateau burning rates of platonic propellants by incorporating phenolic compounds into the propellant. In still another aspect, this invention relates to a method for obtaining plateau burning rates for platonic propellants over the whole available spectrum of burning rates employing a fewer number of propellant formulations than have been utilized heretofore for that purpose.

It is well known that there is a definite and direct relationship between the pressure at which a smokeless powder propellant burns and its burning rate. This relationship may be mathematically expressed as r=cP or as log r=n log P-i-log c, where r is the burning rate, P is the pressure at which the burning rate is measured,

and c and n are constants characteristic of a given propellant. Thus, when a plot of log r against log P is made for the conventional propellant, a straight line of slope n' is obtained showing an inc'rease in burning rate for each increase in pressure. This relationship presents a serious problem in the formulation of propellants for jet-actuated devices since once the operating pressure is reached it is highly desirable that the pressure generated by the burning propellant be maintained as nearly constant as possible. Accordingly, if this result is to be attained, the slope h of the line representing the pressureburning rate relationship of the particular propellant must desirably approach zero in the zone of useful rocket pressure. In the prior art rocket powders, in all of which the slope n has a value of 0.7 or over, any-fracturing or sli-vering of the propellant charge leads to a pressure build-up because of an increase in linear burning rate resultingfrom the increase in pressure due to the increase in burning surface. The higher the 11 value of the particular powder, the higher will be the pressure rise encountered. Therefore, the results of such a fracturing or slivering vary from a highly undesirable thrust fluctuation, with consequent aberration in ballistics, to actual failure of the jet device if, with a propellant of high n value, the pressure build-up is excessive. Even unusual roughness of the charge causes serious changes in burning pressure and burning rate in the presently available rocket propellants with the result that errors in the nozzle diameter have been found to build up to an aberration of percent or more in ballistics. Consequently, there has been very little allowable tolerance in manufacture of charges and nozzles for jet devices. A propellant having a very low n value within the range of useful rocket pressures, however, would allow for considerable tolerance without appreciable deviation from the specified ballistics.

Another serious problem confronting producers of propellants for jet-actuated devices has been the diminution of the temperature coeflicient of equilibrium pressure in the desired operating pressure or in the desired pressure range. The temperature coeificient of equilibrium presice 2 sure is a measure of the pressure variation to be expected on account of temperature variation alone, using a given propellant. It is obtained by firing identical samples of propellant under identical conditions except for changes in temperature and pressure. The coefiicient may be expressed as' where AP is the experimental difference in pressure under conditions of equilibrium burning due to the temperature change At; and I is the mean of the low-temperature and high-temperature pressures.

A low temperature coefiicient of equilibrium pressure, of course, permits design for an unusually low range of service pressure over the wide temperature range ordinarily specified for such devices in field use.

In certain of my copending applications identified hereinafter I have disclosed and claimed propellants modified to exhibit lowered n values and lowered temperature coeificients of equilibrium pressure. Thus, in application Serial No. 492,802, filed March 7, 1955, is disclosed and claimed a smokeless powder gas-producing propellant, each particle of which contains intimately admixed therewith up to 10 percent of at least one aromatic compound of lead; in application Serial No. 492,- 801, filed March 7, 1955, is disclosed and claimed a smokeless powder gas-producing propellant, each particle of which contains an amount not exceeding 10 percent of at least one material of the group of lead, the inorganic compounds of lead and the aliphatic compounds of lead, the said gas-producing composition having a heat ofexplosion of not more than 900 calories per grain; in my copeuding application Serial No. 501,441, filed April 14, 1955, is disclosed and claimed a smokeless powder gasproducing propellant, eachparticle of which contains intimately admixed therewith an amount not exceeding 10 percent of at least one material of the group of lead, the inorganic compounds of lead and the aliphatic compounds of lead, and an amount of finely divided carbon not substantially exceeding the amount of the lead material, the gas-producing composition having a heat of explosion not exceeding 900 calories per grain; and in my copending application Serial No. 501,442, filed April 14, 1955, is disclosed and claimed a smokeless powder gasproducing propellant, each particle of which contains intimately admixed therewith an amount not exceeding 10 percent of at least one aromatic compound of lead and an amount of finely divided carbon not substantially exceeding that of the lead compound. The propellants disclosed and claimed in the copending-applications above referred to are illustrative of modified propellants with which this invention is concerned, and are referred to in the art as plateau propellants. Thus, by the term modified is meant smokeless powder gas-producing compositions which have been modified to exhibit lowered n values and temperature coetficients of equilibrium pressure, being referred to, therefore, in the art as plateau or platonic propellants.

Platonic propellants have, of course, been advantageously utilized in jet and rocket applications. One difficulty, however, that has been encountered is that each specific formulation of smokeless powder has been characterized by a specific burning rate at specific pressures andthat the plateau of low It value wherein a substantially constant burning rate and pressure are obtained is a peculiar characteristic of a given composition. Consequently, in order to obtain either a high rate of burning in a particular pressure region of low n value or to move the region of low n value to a higher pressure range, it has been necessary to design a specific charge formulation. Such a procedure obviously requires a cons? siderable amount of experimentation in order to obtain the desired ballistics, even though the desired increase in burning rate or shift in the region of low 11 value may be small.

Platonic propellants basically contain lead, inorganic lead compounds or lead aliphatic compounds in order to lower the 71 value and temperature coefficient as discussed. Because it has not been possible to regulate burning rate over a reasonably wide range at a given plateau for any given platonic propellant, regulation of plateau burning rate, over the whole available spectrum, has been accomplished only by employing a large number of different propellant formulations.

This invention is concerned with new platonic propellants exhibiting plateau burning rates over wider ranges than heretofore and with a method for regulating platonic propellant burning rates, including regulation of plateau burning rates over the entire spectrum employing markedly fewer formulations than have been required in the past.

An object of this invention is to provide new platonic propellants. Another object is to provide a method for regulating plateau burning rates of a platonic propellant over wider ranges than have been possible heretofore. Another object is to provide for regulation of plateau burning rates of platonic propellants over the whole available spectrum employing markedly fewer formulations than have been required for that purpose heretofore. Another object is to provide for use of phenolic compounds as components of platonic propellants to regulate plateau burning rates of the propellant. Other aspects and objects are apparent in light of the accompanying disclosure and the appended claims.

In accordance with this invention smokeless powder plateau propellants are provided which contain a phenolic compound incorporated into each particle thereof in an amount sufficient to provide for an increased burning rate on said plateau. Also in accordance with this invention plateau burning rates of smokeless powder plateau propellants are regulated over ranges broader than heretofore by incorporating into each particle of the propellant an amount of a phenolic compound sufficient to impart a plateau burning rate therefor over said range. Further, in accordance with the invention, plateau burning rates of plateau propellants are obtained over the whole spectrum of available burning rates which are in the order of from 0.1 to 0.9 inch per second, heretofore available only by selection of from 3 to 6 plateau propellant formulations by incorporating a sufiicient amount of phenolic compound in at least one of a first plateau propellant having a plateau burning rate in the order of from 0.1 to 0.2 in./sec. and a second plateau propellant having a plateau burning rate in the order of from 0.3 to 0.5 in./sec., to increase the burning rate of said propellant by from 0.1 to 0.5 inch per second whereby only two formulations of propellant are required for accomplishing burning rates over the whole available spectrum.

For purpose of illustration several smokeless powder platonic propellant formulations are set forth in the following tabulation together with representative plateau burning rates therefor. The modifier component is, basically, lead or a lead compound and can be inclusive of any or all of those set forth in my copending applications above referred to. Further illustrated by way of the tabulation are marked increases in plateau burning rate ranges that are obtained by incorporating a phenolic compound into each particle of the propellant in accordance with this invention.

TABLE 1 Formulation (Weight percent) Nitrocellulose (12.6% N) 30. 4 41. 8 59. 1 59.0 58. 3 Nitroglyccrin. 36. 8 29. 7 27. 3 27. 2 26. 7 Triacetin 9. 5 14. 2 10.0 10. 1 l0. 2 Sucrose octaacctate... 11. 5 10.6 2-nitrodiphenylaminc. 0. 4 2 5 2 r 2. 5 Ethyl centralite-.. 1 0 0. 5 Carbon black.-. 0.2 0 3 Modifier (Pba 04). 1.8 Lead steal-ate- 2. 8 PbO 1.0 1.0 2.0 Plateau burning rate, lXl./SGG.. 0.08 0.12 0.21 0. 3 0. t Plateau burning rate range, in./see.,

with a phenolic compound also present 0.3 0.4 0.0 0.7 0.9

The following tabulations illustrate specific platonic propellant formulations containing specific phenolic compounds as modifiers together with their plateau burning rates and pressure ranges.

TABLE 2 Composition weight percent Plateau ballistics Rate of Pressure Formulation (solvent extruded) Phenolic compound burning range,

in./sec. p.s.l.

1. None (control) 0.21 450- 800 2. 2,4-dihydroxyb'enzaldehyde 0.40 1, 250-1, 750 3. a-Naphthol 0.34 600-1, 4. fl-Naphthol 0.23 550- 900 5. N-(p-hydroxyphenyl) glycine... 0.35 1 0001,300 0. l-acetamido-G-hydroxynaphthalene. 0.50 1,400-2, 200 gtgggg gg g 016% N) gg-g i1i fi iiiiiiilfiifi ii ffiiiffjI131: 8i $363133 9. 1,5-naphthalencdiol (plus 0.2% GB) 0.80 1,900-4 000 gg 5 10. p-Toluenethiol 0. 51 1, 500-2: 100 Pbo r-cresoll .1 0.24 5(0 000 Phenolic comp 13: RZESLDhZIIIII:1.... 813% 11388 633 14. Resorcinol (plus 0.2% GB). 0. 60 1,000-4, 000 15. Phloroglucinol 0.46 1,000-2, 000 10. Phloroglucinol (plus 0.2% CB) 0. 1,050-4, 000 17. 2-hydroxy-l, 4 -naphthoqtunone 0.36 8501,350 18. 2-n1trc-l-naphthol 0.33 5001,500 19. 2,4-dinitrosoresorcinol 0.37 GOO-1,300

Nitrocellulose (12.6% N) 58.5 20. None (control) 0. 22 450- 850 Nitrog1ycer1n 27.0 21. Orcinol 0. 50 1,050-1,800 Trlacetiu 8.0 22. a.- and fl-Naphthol (l/l) 0.31 GOO-1,100 NDPA 2.5 23. Phloroglucinol/pyrogallol (1/1).. 0. 45 1, GOO-1,300 PbO 2.0 24. Resorcinol/liydroquinonc (1/1 0.45 600-1, 600 Phenolic comp 2.0 25 Resorciuol/phloroglucinol (1/1 0.55 1,3002100 7 TABLE 3 i Casting I Powder Formulae and. Casting Solvents Used Therewith, Weight Percent CASTING POWDERS Nitrocellulose 75. 88. 0 75. 0 so. 0 Nltroglycerin. 10. 0 8. 0 22. 0 31. 0 Lead salieylate 3. 0 Lead betaresoreylate- 3. 0 2-nitrodiphenylamlne 2. 0 1. 0 1. 0 PhD 2.0 2.0 2.0 Sucrose octaacetate- 11.0 Ethyl centralite 1. 0 P1110; 3.0

CASTING SOLVENTS Resor- 1,2,3-Tril1y- 2,4-Dihy- Control einol Control Resordroxybendroxybenz- Control Besorcinol Control Resoreinol 0.3% cinol 1.5% zene 1.6% aldehyde 2. 4% 1 Nitroglycerin n 70 70 60 60. 60 60 60 60 80 80 Triacetin 29 28 39 34 34 34 39 l 34 19 r 16 Ethyl oentralite.-- 1 1 I 2-nitrodiphenylamine. 1 .1 l 1 1 1 l 1 Resorcinol 1 5 6 3 Pyrogallol 5 Resorcylaldehyde Burning rate, ln./Sec. 0. 13 0. 15 0. 47 0.53 0. 0.21 0.45 0. 67 0.80 Burning pressure p.s.1... '330-500 430-600 650-1, 200 850-2, 000 1, 200-3, 500 1, 400-2, 300 500-1, 000 1, 200-2, 200 900-1, 600 1, 300-1, 900

CASTING POWDERS Nitrocel 91. 6 91.0 Nitroglycerin. Lead salicylate- 2. 3 Dinitrotoluene 3.0 Lead beta-resorcylate. Lead 2-ethylhexoate... 2. 3 Lead stearate 5.0 Z-nitrodiphenylamlne 3. 8 1. 0 Pb 0.. Sucrose octaacetate Ethyl centralite- PbaOA CASTING- SOLVENTS Control Resoroinol Resorcinol Control Resorclnol Rcsoroinol 0.7% 2.0% 0.2% 0.3%

Nltroglycerln 1 15 75 71 Trlacetim- 24 22 27 DMI Ethyl centralim N DPA- 1 1 1 Resoreinol 2 0.6 PyrogalloL. Resoreylaldehyde Burning rate, InJs 0.53 0.63 0. 70 0.34 0.36 0.39 Burning pressure p.$.i 1, 350-2, 300 1, 400-3, 000 2, 000-3, 000 850-1, 300 800-1, 600 1, 000-1, 450

The foregoing tabulations illustrate the greater plateau burning rate range that is obtained from a platonic propellant when it contains a phenolic compound in accordance with this invention.

The amount of phenolic compound employed in the formulation to regulate its burning rate to a predetermined degree is, of course, dependent upon the specific formulation. However, the foregoing tabulations exemplify suitable amounts and the degree of increase in plateau burning rate range that can be obtained. Thus, it will be seen, for example, that a cast propellant (run No. 3, Table 3), containing 1 percent PbO as a modifier, will exhibit a burning rate of 0.2 inch per second at 500-1000 p.s.i., but, when modified by the presence of 2.4 percent resorcinol,

the burning rate will be 0.45 inch per second at 1200- der formulations, substantially the entire range of plateau burning rates can be readily covered.

Although platonic propellants of this invention advantageously contain up to about 10 weight percent of the phenolic compounded component generally not more than about 6-7 percent is required. Smaller amounts of phenolic compounds are, of course, employed in regulating the plateau burning rates, dependent upon the specific increase in burning rate that is sought. It is generally a matter of simple trial and error to determine the specific amount of phenolic material most suitable in any given formulation to accomplish the required burning rate.

As further illustrated with reference to the above tabulati0ns, the phenolic compound components of the propellants of this invention are not limited to oxygen compounds, but also include, for example, thiols and thiol ethers. Further, the phenolic compound components can include other functional groups in their structure. Further illustrative of phenolic compound components of the plateau propellants of this invention are meta-amino- '7 phenol, 2,4,6-triazidophenol, para-hydroxypropiophenone, 4,4-bis(b-t-butyl-3-methylphenol) and the like.

Resorcinol is the now preferred phenolic compound component, alpha-naphthol, 1,5-naphthalene diol, phloro glucinol and para-toluene thiol being particularly advantageously employed in many instances.

Platonic propellants of this invention can be produced by incorporating in a singleor double-base smokeless powder composition preferably not exceeding about 10 weight percent of at least one of the group of lead, inorganic lead compounds and aliphatic compounds of lead, together, when desired, with any one or more of additional modifiers, such as an aromatic acid and/or finely divided carbon, and with an amount of a phenolic compound sufiicient to impart an increased plateau burning rate to the propellant, generally not more than 10 weight percent of the resulting propellant composition.

If the smokeless powder component is a single base powder it should preferably comprise from 85-95 percent nitrocellulose and from 5-15 percent of a nonvolatile, nonexplosive plasticizer. Lead powder, red lead, litharge, lead 2-ethylhexoate, lead salicylate and lead stear ate are especially suitable as lead modifiers of the formulations of this invention, litharge being now preferred.

Further illustrative of suitable nonvolatile, nonexplosive plasticizers for the smokeless powder formulations of this composition are: pentaerythritol acetate-propionate, dimethyl, diethyl and other phthalates, various succinates and sebacates. Exemplary of lead modifiers in addition to those already discussed with reference to my copending applications, hereinabove, are: lead cyanamide, lead acetylsalicylate, lead carbonate, tetraethyl lead, lead azide, lead hydroxide, lead benzoate and variously substituted derivatives containing amino groups and lead thiols, ethers, esters, ketones and aldehydes.

Carbon black, when employed as a modifier, is employed in amounts not substantially exceeding the amount of lead and/ or lead compound employed. The contribution of the presence of carbon black to plateau properties of the propellant is, of course, dependent upon the particular basic formula of the gas-producing composition. Carbon concentration of 1 percent or less and lead or lead compound concentrations up to about 5 percent are preferred. Particle size of the carbon component can be varied, the preferred particle size being in the order of 0.01 micron or less.

As hereinabove illustrated, propellant compositions of this invention can be prepared by solventless extrusion. In the conventional solventless process water weight nitrocellulose and the other ingredients are admixed in a Schrader bowl with water. The resulting slurry or paste is dried to about percent water and is colloided and dried between hot colloiding rolls which may be even spaced, or differential speed rolls, if desired. The resulting colloided dried sheets are then wound into discs or convolutely rolled into carpet rolls. The discs or carpet rolls are then extruded to desired grain size.

The propellant composition can also be made by the solvent process. In the usual solvent process, the water in hydrated nitrocellulose is first replaced, for example, by treatment with ethyl alcohol. A colloiding solvent such as ether or acetone is then added to the dehydrated nitrocellulose along with additional ingredients and a doughy mass is formed in a suitable mixer such as a sigma blade mixer. This dough is then formed into green grains, usually by extrusion into cords and cutting the cords to the desired length. The green grains are then subjected to solvent removal steps, including vaporization, water leaching and drying.

As is well known in the art, in the manufacture of grains exceeding about 5-6 inches in diameter it is preferred to cast the propellant. In the usual casting process, tiny singleor double-base powder grains, prepared by either the solvent or solventless techniques are introduced into amold together with suitable plasticizers. The plasticizers cause the grains to coalesce into a unitary mass of plastic composition. The plasticizer is a liquid composed of a mixture of nonvolatile explosives and nonexplosive plasticizers and is often referred to as the casting liquid or casting solvent. One casting method comprises initially mixing the powdered components into a homogeneous mass, introducing the resulting mass of powder granules quickly and at an even rate into a suitable casting container, placing a vented weight on top of the powder to hold it in place and then admitting the casting solvent, including the phenolic compound, upwards through an opening in the base of the container. As the casting liquid slowly rises in the container it forces air trapped in the powder upwards and the casting liquid completely contacts and surrounds the individual powder granules. The casting so produced is homogeneous and is completely free from air bubbles which are initially trapped in the powder. However, a now-preferred casting method and casting apparatus is that disclosed and claimed in the copending application of Gordon W. Mc Curdy, Serial No. 28,218, filed May 20, 1948, in accordance with which the incoming casting liquid is evenly distributed over the cross-sectional area at the base of the casting container to prevent channeling of the casting liquid in the casting material, whereby passage of entrained air from the casting liquid system into the casting material is prohibited.

When producing propellants of this invention by solventless extrusion, the modifier, including the phenolic compound, is preferably added at some time prior to dehydration of the water slurry and the additive system is mixed to a stage of homogeneity. The slurry is then dehydrated, the moist mass is formed into colloided sheets, the sheets are rolled and the rolls thus formed are extruded in the conventional manner. However, if desired, the modifier components, including the phenolic compound component, can be added during milling.

When producing propellants of this invention by solvent extrusion, the modifier, including the phenolic component, is preferably added to the dehydrated nitrocellulose after it has been broken up in a mixer. The modifiers may be added with the plasticizer before or after introduction of the plasticizer.

When the grains are made by casting, the lead or lead compound modifier can be homogeneously incorporated by introduction into the casting powder. Preferably, however, the phenolic compound, as demonstrated, is added as a component of'the casting solvent.

All modifiers, including the .phenolic component, are uniformly admixed with the other ingredients of the composition. The modifier, including the phenolic component, must be intimately admixed with the other ingredients within each particle of the composition whether the charge is a loose charge of individual grains or consists of a single grain.

As will be evident to those skilled in the art, various modifications can be made or followed in light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

This application is a continuation-impart of my copending applications, Serial Nos. 492,801 and 492,802, both filed March 7, 1955, and Serial Nos. 501,441 and 501,442, both filed April 14, 1955.

What I claim and desire to protect by Letters Patent is:

1. A propellant composition consisting essentially of a smokeless powder containing nitrocellulose as a chief ingredient and selected from the group consisting of single base and double base smokeless powders and containing an amount not exceeding about 10 weight percent of at least one material selected from the group consisting of lead, inorganic compounds of lead, aromatic compounds of lead and aliphatic compounds of lead to maintain a value less than 0.7 for the slope n of the plateau line representing the pressure in burning rate relationship of (4.2m "limit said propellant, and a suificient amount of a phenolic compound to provide for an increased burning rate on said plateau.

2. A propellant of claim 1 containing finely divided carbon in an amount not substantially in excess of that of said lead material.

3. A propellant of claim 1 wherein said phenolic compound is selected from the group consisting of resorcinol, alpha-naphthol, 1,5-naphthalene diol, phloroglucinol, and para-toluene thiol.

4. A propellant of claim 1 wherein said lead material is litharge.

5. A propellant of claim 1 wherein said lead material is lead stearate.

6. A propellant of claim 1 wherein said lead material is lead Z-ethylhexoate.

7. A propellant of claim 1 wherein said lead material is lead salicylate.

8. A propellant composition of claim 1 containing up to weight percent of said phenolic compound.

9. In a propellant of claim 1 finely divided elemental carbon in an amount not in excess of that said lead material.

10. In the burning, in a rocket motor, of a smokeless powder propellant composition containing nitrocellulose as a chief ingredient and selected from the group consisting of single base and double base smokeless powders and containing an amount not exceeding about 10 weight percent of at least one material selected from the group consisting of lead, inorganic compounds of lead, aromatic compounds of lead and aliphatic compounds of lead to maintain a value less than 0.7 for the slope n of the plateau line representing the pressure in burning rate relationship of said propellant, the improvement comprising burning an amount of a phenolic compound, as a uniformly admixed component of said propellant, sufiicient to provide for an increased burning rate on said plateau.

11. The improvement of claim 10 wherein red lead is burned in said propellant together with said phenolic compound.

12. A method of claim 10 wherein finely divided carbon black is incorporated into said propellant.

13. A method of claim 10 wherein said phenolic compound is selected from the group consisting of resorcinol,

smokeless powder containing nitrocellulose as a chief ingredient and selected from the group consisting of single base and double base smokeless powders, and containing red lead and a phenolic compound each in an amount not exceeding 10 weight percent.

19. In a method for producing a smokeless powder propellant composition containing nitrocellulose as a chief said propellant, and wherem the burning rate on said 1 plateau is predetermined and is within the range of 0.1 to

alphanaphthol, 1,5-naphthalene diol, phloroglucinol, and

para-toluene thiol.

14. A method of claim 10 wherein said lead material is lithange.

15. A method of claim 10 wherein said lead material is lead stearate.

16. A method of claim 10 wherein said lead material is lead Z-ethylheiroate.

17. A method of claim 10 wherein said lead material is lead salicylate.

18. A propellant composition consisting essentially of a 0.9 inch per second, the improvement which requires only one of two basic formulations in the manufacture of such a propellant composition over the said range of predetermined burning rate values, which comprises selecting as a basic formulation a smokeless powder propellant composition, above described, having a burning rate onthe said plateau of at'least 0.1 lower than the said predetermined value' and selected from the group consisting of a first formulation having a burning rate on the said plateau of from 0.1 to 0.2 inch per second and a second formulation having a burning rate on the said plateau of 0.3 to 0.5 inch per second and having a burning rate value on the said plateau not greater than 0.5 below the said predetermined value, and uniformly admixing with the basic formulation so selected a suificient amount of a phenolic compound to increase the burning rate of the said basic formulation to the said predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 2,385,135 Holmes Sept. 18, 1945 2,617,251 Hutchinson et a1 Nov. 11, 1952 2,711,366 Davidson -l. June 21, 1955 2,852,359 Achilles Sept. 16, 1958 2,885,736 ONeill May 12, 1959 FOREIGN PATENTS 597,879 Great Britain Feb. 5, 1948 485,622 Canada Aug. 12, 1952 485,662 Canada Aug. 12, 1952 OTHER REFERENCES Colver: High Explosives, Crosby Lockwood & Son, London (1918), pp. 135, 169, 253, 342.

Military Explosives, Technical Manual, No. 9-1910, Technical Order No. 11-A-1-34, Dept. of The Army and Air Force, April 1955, pp. 247 and 259.