US3033717A - Gas-producing charge - Google Patents

Description

V 3,033,717 GAS-PRODUQIING CHARGE p11 F. Preckel, Cumberland, Md., assignor to Hercules Powder Company, WilmingtomDeL, a corporation of Delaware a No Drawing. Filed Apr. 14, 1955, Ser. No. 501,441

lfiClaims. (Cl. 149-100) This invention relates to the production of smokeless powders and more particularly to the production of smoke less. powders having peculiarly desirable ballistics for applications in jet-actuated devices. It is well known that there is a definite and direct relationship between the pressure at which a smokeless pow der propellant burns and its burning rate. This, relationship may be mathematically expressed as r=cP or as log r=n log P+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 Pisl made for the conventional propellant,a straight line of slope n is ob tained showing an increase in burning rate for each inwhere AP is the experimental difierence in pressure under conditions of equilibrium burning due to the temperature change Al; and? is the mean of the low temperature and high temperature pressures. I The advantage of having a low temperature coefficient of equilibrium pressure is obvious. If the coefficient is low, the jet-actuated device may be designed for an unusually low range of service pressure over the wide temperature range ordinarily specified for such devices in field use. Since existing propellants generally have temperature coefiicients of equilibrium pressure of about v 0.8%/ C. or more, service pressure may change by crease in pressure. Such a relationship is not disadvan tageous in'theconventional gun propellant and in fact is used to advantage in progressivepowders where it is highly desirable to generate increased pressures after the projectile or shot charge has begun to move along the barrel. However, this relationship presents a serious problem in formulation of propellants for jet-actuated devices since once the desired operating pressure is reached,

totally different considerations obtain.

It is highly desirable, once the operating pressure of a jet-actuated device is reached, that the pressure generated by the burning propellant be maintained as nearly contant aspossible; Accordingly, if this resultis to'be attained, theslope n 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 slivering of the propellant charge leads to a pressure build-up because of an increase in linear burning rate resulting from the increase in pressure due to. the increase in burning surface. The higher the n 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 11 value, the pressure build-upj is excessive. Even unusual roughness of'the charge causes serious changes in burning pressure and burning rate in the presently available rocket propellants and have been found to build up to an aberration of 5% or more in ballistics. Consequently, with the propellants now available, there is very little allowabletolerance in manufacture of .charges and nozzles for jet devices. A propellant having a very low 12 value within the .range of useful rocket pressures, however,

, is obtained by firing identical samples 'of propellant under identical conditions except for changes in temperature and pressure. Thecoeflicient may beexpressed as 100% or more in going from the lowest expected temperature to the highest expected temperature. It is therepropellants and thereby hold variation in service pressures due. to temperature change to a minimum. If the coeffieient could be lowered from 0.8%/ C. to 0.4%/ C. or .less, service pressure variation would be diminished by at least one-half.

;As a result of the advantages set forth above for a propellant having a low n value and a low temperature coeflicient' of equilibrium pressure, the combination of those two ballistic characteristics would allow additionally for important economies in the inert weight of jet-actuated devices. This is clearly seen if the equation is examined which relates the ratio between the mass of propellant (m) and the mass of the jet device without propellant (M), the gas velocity of the burning propellant (V), and the highest theoretically obtainable velocity of the jet device (V as follows:

' m V,,,,,,= .303V log (1 pressures, to decrease M by 10% and increase the amount of propellant to give the same total initial weight, V would be increased by a factor of about 1.15. This would be a l5% improvement.

In my copending application Serial No. 492,802, filed 'March 7, 1955, of which the present application is a conthese effects that the finished composition be characterized by a heat of explosion of not more. than 900 calories per gram. If the smokeless powder to which one of these ballistic modifiers is added is a single-base powder, it should preferably comprise from -95% of nitrocellulose and from 5-15 of nonvolatile, nonexplosive plas- Q ticizer. If the propellant used is a multiple-base formula, it should preferably comprise from 40-85% of nitrocellulose, from 1035% of explosive liquid nitric ester and from 530% of a substantially nonvolatile, nonexplosive plasticizer. Up to and including 10% of one or moreof the ballistic modifiers selected from the group consisting of lead and the inorganic and aliphatic compounds of r =2 lead may be employed without adversely affecting the ballistics of the gas-producing compositions of the invention. However, it is preferred to employ only sufiicient of the additive to effect the desired modification in ballistics. In most cases, it has been found that 2% of the 5 various additives based on the weight of the smokeless powder employed is ample. While lead powder, lead oxide, and lead stearate are the preferred modifiers, a substantial effect has been obtained from the incorporation of lead or any inorganic or aliphatic compound of lead.

Gas-producing compositions characterized by a low 11 value and a low temperature coefficient of equilibrium pressure have proved greatly advantageous in jet and rocket applications. Actually, the only difficulty which has been encountered lies in the fact that each specific formulation of smokeless powder and ballistic modifier has been characterized by a specific burning rate at specific pressures and that the plateau area of low n 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 higher rate of burning in a particular pressure region of low 11 value or to move the region of low 11 value to a higher pressure range, it has been necessary to design a specific charge formula. Such a procedure obviously requires a considerable 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 It value may be small. 7

The object of the present invention, therefore, is a gas-producing composition which is characterized by a low n value.

Another object of the invention is a gas-producing composition which is characterized by both a low It value and by a low temperature coefiicient of equilibrium pressure.

A further object of the invention is such a gas-producing composition in which the burning rate is substantially increased in a region of low n value within the range of useful rocket pressures.

An additional object of the invention is a means by which the burning rate of a gas-producing composition (Ii consisting of lead, the oxides 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 lead or compound of lead; said gas-producing composition having a heat of explosion of not more than 900 calories per gram.

The burning rates in the plateau or low n value region in useful rocket pressure ranges of powders modified by incorporation of lead or lead compounds have generally ranged from about 0.20 to 0.35 inch/sec. By the addition to compositions thus modified of finely-divided carbon in amounts not substantially exceeding the amount of lead and/or lead compound employed, it is possible to increase plateau burning rates in the range of useful rocket pressure far above the plateau burning rates of the same compositions to which no carbon has been added. It has been found that a preferred range of carbon addition exists for each ballistic modifier chosen from the group consisting of lead and compounds of lead. Within this range, the plateau burning rate is strongly dependent on the carbon concentration and at optimum concentration, n values of between 0.0 and 0.2 are readily obtained. In fact, negative n values are often obtained. Furthermore, there is also an optimum carbon content which will give the maximum burning rate attainable while still retaining an acceptably low slope in the desired pressure ranges. Carbon concentrations which achieve these preferred and optimum conditions are naturally functions of each particular basic formula of gasproducing composition. Generally, carbon concentrations of 1% or less and lead or lead compound concentrations of 5% or less are preferred. In all cases, however, the amount of carbon must not exceed the amount of lead and/or lead compound employed. The upper limit of lead and/or lead compound ballistic modifier is 10%. Lead stearate is the preferred ballistic modifier.

While the finely-divided carbon may vary in particle size, the smaller particle sizes are most effective. The greatest increase in plateau burning rate which has been obtained has been with a carbon black having an average particle size of 0.01 or less micron.

Having generally described the invention, the following examples are presented for purposes of illustration.

having a low n value and a low temperature coefficient ballistics arelshown for gas'pmducmg of equilibrium pressure in the range of useful rocket Posmons avmgt egenera formula pressure can be substantially increased without inordinate- Nitrocellulose (12.6% N) 58.5 1y increasing the 11 value. Nitroglycerin 27.5

Generally described, the present invention is a gas- Triacetin 7.5-10.0 producing composition comprising a smokeless powder Ethyl centralite 1.0- 4.0 having uniformly incorporated therein an amount not Lead stearate 1.0- 6.0 exceeding 10% of at least one material of the group Carbon (Excello, 0.03 micron) 0.2- 1.0

Table I VARIATIONS IN BALLISTICS WITH CONCENTRATIONS 0F LEAD STEARA'IE AND CARBON BLACK Composition Interpolated burning rate Graphical 72 Temp. Ex 000%.]? Heat of equ l exp.

0.13. PbStr. Pressure At; 25 C. At50 0. Pressure ri l. 12.6% NG TA EC (added) (uomi- (p.s.i.) (iu./see.) (in./sec.) interval 71 pre s i i re (08 lg) N nal) (p.s.i.) (percent/ 1 58.5 27.0 8.5 4.0 None 2.0 500 0.15 0.16 300- 570 0.58 0.5 703 1,000 0.19 0.22 570- 840 0.1a 1, 500 0. 25 0. 28 840-2, 250 0. 2, 000 0. 31 0. 34 2, 2504, 000 1. 00 2,500 0. 37 0. 4a 2 58.5 27.0 8.5 4.0 0. 35 2.0 500 0.23 0.25 sou-1,400 0.07 0.4 778 1, 000 0. 37 0. 40 1, 400-3, 000 o. 17 1, 500 0. 47 0. 50 3, 000-4, 000 0. 50 2,000 0.49 0.53 2,500 0.51 0.55 58.5 27.0 8.5 4.0 0.5 2.0 500 0.22 0. 2a sou-1,500 0.71 0.4 772 1, 000 0. 30 0. as 1, 5004, 000 0. 21 1, 500 0. 4s 0. 51 4, 000-4, 600 0. 52 2,000 0. 51 0.54 2,500 0. 53 0.57 4 58.5 27.0 8.5 4.0 0.75 2.0 500 0.21 0.24 $204,000 0. 01 0 7 762 1 000 0. 32 0. as 1, 0004, 000 0. as

Heat of Percent 2.0. (As indicated).

Temp. coeff. of equilibrium pressure (Percent/ C.)

istic modifiers selected from the the inorganic compounds of lead Graphical-n Pressure interyal (p.s.1.)

ite

ycerin Rate at Rate at (in/sec.) (in/sec.)

centage of various ball group consisting of lead, and the aliphatic compounds of lead. The following basic formula was employed:

Nitro Triacetin Ethyl central Ballistic modifier 10 Carbon black (Excello, 0.03 micron) 0.0-0.5.

Table II Iuterpolated burning rate Pressure (p.s.i.)

ing varysic composition:

58.5 5 Nitrocellulose (12.6% N) 58.5.

Table III BALLISTIG EFFECTS OF FINELY DIVIDED CARBONS OF VARIOUS PARTICLE SIZE rin CARBON BLACK EFFECT ON BALLISTIOS OF SOME PLATEAU PROPELLANTS In Table II, ballistics are shown for gas-producing compositions formed by adding 0.5% of carbon hav ing particle size to the following ba Nitrocellulose (12.6% N) Nitroglyce Triacetin Ethyl centralite Lead stearate 1 Ball milled and screened thru a 325 mesh screen. 2 Passes thru a 325 mesh screen as supplied.

In Table III, the ballistic data are set forth to illustrate the effect of carbon black addition to gas-producing compositions of the invention containing the indicated per- I m w 0 N 8 7 p a w fme nmm m M mfi s o Gene m w e 8 007% mm H 1000 000 w .1 0000 500 0600 700 w. m) 3850 090 a mm. 2 L2 r. 4 a new wwwm We 1385 30% 2 1'2 4 818538 B e izzaizfmm M 0000000000 r 5 I r. g t.m m A r. C 6851769 8 u o C 1123329 A fiA M m 000 0 0 0 0 0 0 0 e n M A0 1 m. e

000 000 H ooomooomww t S.J 50505-00505 55 i i 1 i i v i 1122 1122 .m mo. r\ n d 9 5 %6 n b d o 0 r3 3mm N C n n w n. n n n w r e u u m u u m n m m n m m m w 5 n d m a u n 1.. m 0 n 4 X E 4 5 8 3 ble II -Con ned Interpolated burning rate Graphical 1: Temp. Garbo V coefi. of- Heat of Ex. Lead compound (percent) black equilibrium exp.

(added) Pressure" At 0. At 50 0. Pressure pressure (eaL/g.) (p.s.i.) (in/sec.) (in/sec.) inter al 0 (percent/ (0.01.) J-) 36 4.0% lead molybdate None 500 0. 21 0. 24 300.- 730v 0. 63 0. 7 897 1, 000 0. 34 0.48 640-2, 000. 0. 45 1, 500 0. 54 0.58 2000-3, 000 0.15 2, 000 0. 60 0. 64 3, 000-4, 000 0. 63 1 2, 500 .0. 64 0. 68 38"-.. 1.0% meta lead paste None 500 0.22 0.24 300- 740 0.32 693 9 2, 500 0.40 0.44 39 do 0.2 500 0. 23 l 0.24 200-1,250 0.76 685 1, 500 0. 47 0. 49 2, 900-4, 000 0. 58 2,000 0.48 0. 51 2, 500 0.49 0. 52 2.0%1ead perchlorate None 500 0. 25 '0. 28 300- 490 0. 55 873 l, 500 0. 41 0. 45 900-1, 375 -0. 17 0. 20 2, 000 0.47 0.53 1, 375-2, 350 0. 53 2,500 0.55 0.62 2, 350-4, 000 0.81 42 4.0% lead 2-et11yl hexoate None 500. 0.10 0.19 100- 200 1.2 0.3 828 1, 500 0. 52 0. 54 a, 100.4, 000 0. 50 2, 000 0.56 0.59 2,500 0. 0.63 44..-" 2.0% lead methoxy p10pi0nete None 500 0.16 0.18 150- 350 0.50 899 1, 000 0, 28 0.29 330- 800 0.42 1, 500 0. 31 0. 34 800-1, 325 0. 03 0. 21 2.000 0.37 0.43 1 325-2, 025 0.63 2,500 0.45 0.52 2,025-4 .000 0.89 46 2.0%lead ethoxy proplonate None 50 0.23 0.26 300- 530 0.91 887 1, 000 0. 24 0. 28 530-1, 000 0. 00 0. 50 I, 500 0. 30 0. 34 1, 000-2, 0. 50 2, 000 0. 35 0. 41 2, 100-4, 000 1. 20 2, 500 0. 44 0. 50 r 47 do 0. 4 500 0. 22 0. 25 310-1, 0. 75 s23 1, 500 0.45 0. 47 1, 700-2, 300 0. 21 0.09 2, 000 0. 46 0. 45 2, 300-4, 000 0. 65 2, 500 0. 45 0. 51 48 2.0% tribasic lead maleete None 500 0.20 0.22 260 0.24 839 1, 000 0. 32 0. 34 750-1, 350 0. 00 0. 36 1, 500 0. 35 0. 42 1, 350-4, 000 0. 70 2, 000 0.44 0.50 2, 500. 0. 52 0.60 ,50. 1% lead NOIIG 500 0.22 0. 24 300- 710 0.37 0.3 696 52 40% lead sulfide None 500 0. 24 0. 25 300- 530 0.32 0.3' 890 1, 000 0. 28 0. 30 530-1, 200 0. 20 1, 500 0. 35 0. 38 1, 200-4, 000 0. 82 2, 000 0. 44 0.49 2, 500 0. 53 0. 59 53 (10 0.5 500 0.38 0.43 300- 550 0.66 0.4 869 .1 1, 000 0.54 0.59 550-1,775 0.44 1, 500 0. 65 0. 71 1, 775-4, 00 0. 19 2,000 0. 72 0.77 2,500 0.74 0.80 64 4% lead monoxide None 500 0. 17 0.19 550 0.02 0. 4 834 1, 500 0. 32 0. 38 1, 450-4, 000 0. 97 2, 000 0. 42 0. 50 r 2, 500 0. 53 0. 62 55 do 0.5 500 0.23 0.26 100- 0. 60 0.5 863 1,000 0.31 0.34 190- 700 0.18 1, 500 0. 40 0. 45 700-1, 350 0. 57 2, 000, 0. 50 V 0. 56 1, 350:4, 000 0. 75 2, 50 0 0. 00 0. 66 56, 1% tetraethyl lead None 500' 0.23 0.24 300- 500 0.24 0.3 682 Table lIICont 1nued Interpoiated burning rate Graphical 11 Temp. Carbon coefi. of Heat of Ex. Lead compound (percent) black equilibrium exp.

(added) Pressure At 25 0. .41; 50 0. Pressure pressure (020.!)

(p.s.i.) (in./sec.) (in/sec.) interval n (percent/ (p.s.i.) O.)

1, 000 0. 30 0.34 2, 175-3, 000 0. 50 1, 500 0.34 0.38 2, 000 0.37 0.41 2,500 0.41 0.45 58.. 1.5% lead acetate None 100 0.064 0.073 100- 260 0.15 0.7 609 200 0. 076 0.085 270-4, 000 0. 74 300 0.087 0.100 400 0.107 0.122 500 0.127 0.141 60 1% lead ethoxy-aoetate None 500 0.16 0.19 300- 380 0.24 0.7 820 1, 000 0. 0. 23 880-2, 150 0. 80 1, 500 0. 28 0. 32 2, 150-4, 000 1. 38 2,000 0. 36 0.40 2,500 0.47 0.53 til 0. 3 500 0.22 0.25 800-1, 250 0. 70 0. 2 807 1 Lead flakes, 80% through 325 mesh,/minera1 spirits containing 10% stearie acid-90/10.

The examples in Table 'IV illustrate that it is undesirable to employ more than the necessary amount of finelydivided carbon and that plateau ballistics are not obtained where the amount of carbon substantially exceeds the amount of lead or lead compound.

aliphatic compounds are generally operable in lowering the n value and the temperature coefficient of equilibrium pressure in smokeless powder compositions having a heat of explosion of not more than 900 calories per gram,

35 some of the specific compounds, and particularly lead Table IV Burning rate Graphical 11 Temp. 0. (in/sec.) coefi. of N0 Carbon Lead equilib- Heat 0! Ex. 12.6% N NG TA E0 black stearate rium exp.

(added) (nominal) 1,000 1,500 Pressure pressure (caL/g.)

p.s.l. p.s.i. interval at (percent/ (p.s.i.) C.)

58. 5 5 None 10 0. 19 0.26 200- 500 0 3 750 58. 5 26 5 1 10 39 44 1, 000-3, 000 0.3 5 710 58. 5 26 10 10 39 49 1, 000-2, 500 6 7 435 58. 5 28 5. 5 8 None 1 22 26 660-1, 250 2 3 760 58. 5 27 8. 0 1 0.5 5 1 38 No plateau 740 l Nitrodiphenylamine substituted for ethyl centralite. Norn.-NC =nitrocellu1ose, NG =nitrog1ycerin,

EXAMPLE 67 The following single base gas-producing compositions were prepared: A. Nitrocellulose (12.6% N) 95.0 Ethyl centralite 1.0

Lead stearate 4.0 B. Same except for addition of 0.5% carbon black.

These compositions had the following comparative properties:

From the foregoing examples and from the disclosure of the copending application, Serial No. 492,802, it is evident that while lead, its inorganic compounds and its TA triacetin, E C =ethyl centrallte.

stearate, are more effective than others. In like manner, while the addition of finely-divided carbon will raise the burning rate in the plateau region of all these compositions, some combinations of ballistic modifier and carbon are more desirable than others. From the combined viewpoints of effectiveness and economy, combinations of lead stearate and carbon are preferred.

From the examples it is further seen that relatively small amounts of finely-divided carbon will usually produce the desired burning rate increase in the plateau region. In fact, optimum results are generally encountered when the finely-divided carbon constitutes between 10 and 33% by Weight of the lead and/ or lead. compound employed. Greater amounts of carbon may be employed up to 10% by weight of the gas-producing composition as long as the amount of carbon never substantially exceeds the amount of ballistics modifier. If the amount of carbon employed does exceed the amount of plataeauproducing agent, plataeau ballistics are detrimentally affected. Furthermore, increasing the carbon content of a particular powder composition brings about a corresponding increase in brittleness in the powder. In addi- 13 tion it will be appreciated that addition of unnecessary amounts of either the plateau-producing modifier or the carbon effects a cooling of the powder which lowers p l. and snitahil yfiaassque y. it is undesirable to employ more of either modifier than is necessary to obtain the desired modification in ballistics.

While the ranges given for the conventional components of the singleor multiple-base powders are not critical as long as the heat of explosion of the powder with the added modifier does not exceed 900 calories per gram, it has been found that powders prepared according to these ranges are more apt to come within this critical calorific requirement.

The compositions of the invention may be prepared by solventless extrusion. In the conventional solventless process, water-wet nitrocellulose and the other ingredients are admixed in a Schrader bowl with water. The resulting slurry or paste is dried to 10% water and is colloided and dried between hot colloiding. rolls which may be even-speed or differential-speed rolls as desired. The resulting colloided, dry sheets are then cut into disks or convolutely rolled into carpet rolls. The disks or carpet rolls are then extruded to desired grain size. Flake powder may be formed by suitably shredding the sheet. The resulting grains are normally glazed, usually with graphite, to lower static generation and to improve flowing characteristics.

The compositions of the invention may also, be made by the solvent process. in the usual solvent process, the

water in hydrated nitrocellulose is first replaced, for exa 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. The greater portion of the solvent is normally removed by passing a warm inert gaseous medium such as air or flue gas over the grains. The remainder of the solvent which can be practically removed is then usually leached out by a water treatment. Water is. then removed by an air dry step and the dry grains are normally given a glaze, usually of graphite, to lower static generation and to improve flowing characteristics.

In the usual casting process, tiny singleor double-base powder grains, prepared by either the solvent orsolventless techniques, are introduced into a mold together with suitable plasticizers. When the castings are cured, preferably by warm air storage at temperature of from about 100 F.to about 160 F., the plasticizers cause the grains to coalesce into a unitary mass of plastic composition. Thev preferred casting process is that disclosed in the copendingapplication of Gordon W. McCurdy, Serial No.

28,218, filed May 20, 1948.

As is well known to the art, colloiding solvent can be removedfrom powder grains of large diameter and web onlywith extreme. difliculty. This difficnlty increases as the webthickness is increased. It is therefore desirable to prepare grains of the multiple-base formulations of this invention by solventless extrusion or by a suitable casting process. It is preferredto extrude grains up to about or 6. inches in diameter and to cast all'larger grains. Casting of the larger grains is preferred because the cost andmassive nature of extrusion presses large enough to produce grains of over 5 or 6 inches in diameter become prohibitive.

The single-base formulations given in the examples are preferably made by a conventional solvent process, extruded, and cut to the desired granulation. Such a process limits the possible size of the single-base grains to a diameter or web thickness which will allow sufficient removal of the colloiding solvent. Grains of solventcolloided powder having large diameter and web are, of course, operable and as long as the heat of explosion does not exceed about 900 calories per gram, addition of the disclosed modifiers according to this invention will effect the desired modification in ballistics. It is, of course, well known that the change in ballistics during storage caused by gradual migration and evaporation of the colloiding solvent is the reason why large grains of solvent-colloided powder are not manufactured. As improved processes and means for solvent removal are developed, it will perhaps be possible to produce correspondingly larger grains of solvent-colloided powder which are ballistically stable. 7 i

t is not preferred to produce single-base grains by solventless extrusion or by casting because, in order to keep the powder in the single-base category, the plasticizer employed to bring about colloiding and/or consolidation must be of lower potential than the nitrocellulose. The necessary amount of plasticizer, therefore, so lowers the potential that such powders have only a limited application. Nevertheless, incorporation of the disclosed modifiers in single-base grains prepared by solventless extrusion or by casting still results in a low 11 value and a low temperature coefficient of equilibrium pressure.

If the gas-producing charges of this invention are made by solventless extrusion, the ballistic modifier or modifiers are preferably added at some time prior to dehydration of the water slurry and the additive system is mixed to a state of homogeneity. The slurrry is then dehydrate, the moist mass is rolled into colloided sheets, the sheets are male into rolls and the rolls are extruded in the conventional manner. However, it is often found advantageous to add the ballistic modifiers during the rolling operation, rather than to the water slurry. If the Well known Schrader process is employed, the modifiers may be added to the hydrated nitrocellulose in the mixing bowl in any preferred order. A portion of the water is evaporated prior to rolling. The Schrader process is preferred when water-soluble plasticizers are employed.

If the charges of this invention are prepared by solvent extrusion, the ballistic modifier or modifiers are preferably added to the dehydrated nitrocellulose after it has been broken up in a mixelz The modifiers may be introduced with the plasticizer or plasticizers or may be added before or after introduction of the plasticizer as may be desired in the particular formulation.

If the grains are made by casting, the ballistic molifier is homogeneously incorporated during'the preparation of the casting powder.

The heat of explosionof an explosive composition may be experimentally determined in the known manner by actually exploding a sample of the substance in a bomb calorimeter under conditions which insure complete combustion of the constituents of the composition, and measuring the heat liberated. However, in the case'of smokeless powder compositions, which contain at most only small portions of inorganic material, it is usually desirable to determine the heat of explosion by calculation. Thecalculation of heats of explosion is especially desirable in order to accurately predetermine the calorific value of a proposed composition prior to its formulation. In this calculation, use is made of a simple relation; namely, the heat of explosion per gram of powder is equivalent to the sum of the products of the weight fraction of a 'given constituent by the contribution to the heat of explosion of the constituent, This contribution of the constituent is for convenience termed the partial calorific potential or the partial heat of explosion, and is usually designated as K Thus, th heat of explosion of the composition is derived by the equation:

Heat of explosion=zX K where X, is the weight fraction of the powder component i.

For compositions consisting principally of carbon, hy-

1 drogen, oxygen, and nitrogen, K is quickly and accurately determined according to the following equations:

where 0 is the number of gram-atoms of oxygen per gram of the powder component i, C is the number of gram-atoms of carbon per gram of the powder component i, H is the number of gram-atoms of hydrogen per gram of the powder component i, H0. is the heat of combustion at 25 C. and constant volume, and AEf is the heat of formation per gram of the powder component i from its elements.

Partial heats of explosion for inorganic substances such as the ballistic modifiers of the invention are not quite as readily calculated but may, nevertheless, be determined according to methods disclosed by De Pauw in Z. f. ges. Schiessund Sprengstoffwesen, 32, 11, 36-, 60 (1937); or by Hirschfelder and Sherman in Simple Calculation of Thermochemical Properties for Use in Ballistics, O.S.R.D. Report No. 1300, declassified and issued as PB27421S.

Actually, it is unnecessary to experimentally determine the K values for the various constituents of the smokeless powders in accordance with the invention since tables of the partial heats of explosion for these materials are available as published data. The following is a listing of the K values of the normally usel smokeless powder components and many of the operable ballistic modifiers in accordance with the invention.

Substance (i): Partial heat of explosion (cal./ g.)

Acetone 1938 Carbon black 3330 Diamylphthalate -2190 Dibutylphthalate -2055 Diethanol nitramine dinitrate 1294 Diethylene glycol dinitrate 1030 Diethylphthalate -1746 Dinitrotoluene 140 Diphenylamine 2684 Diphenylurea -2227 Diphenylurethane -2739 Ethyl alcohol 1749 Ethyl centralite 2398 Ethyl urethane 1639 Graphite -3377 Lead 0 Lead acetate (trihydrate) 282 Lead azide 385 Lead bromide -137 Lead carbonate (basic) 471 Lead chloride 151 Lead perchlorate 1250 Lead chromate 977 Lead diacetylacetonate 868 Lead ethoxyacetate 639 Leal Z-ethyl hexoate 1336 Lead fluoride -127 Lead hydroxide -189 Lead iodide 91 Lead linoleate 1982 Lead maleate (tribasic) -320 Lead molybdate 403 Lead naphthenate -2048 Lead oleate 20l0 Lead oxalate 58 Lead oxide (PbO) 67 Lead oxide (Pb O 139 Lead oxide (PbO 302 Lead methoxy propionate 634 Lead ethoxy propionate 1400 Lead stearate Substance (i): Partial heat of explosion (cal./ g.) Lead sulfate -l50 Lead sulfide 222 Lead tartrate 172 Lead tetraethyl l231 Nitrocellulose 13.25% N 1041 13.15% N 1027 13.00% N 1007 12.60% N 951 12.20% N 895 12.00% N 867 11.50% N 797 Nitroglycerin 1785 Nitroguanidine 720 Triacetin 1284 Water -5 In order to produce the plateau" type ballistics of the invention, the modifiers must be uniformly incorporated with the other ingredients of the composition; that is, the modifier 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 of any desired size. The glazing or coating of a single grain or a plurality of grains in a loose charge will not produce the desired modification in the pressure-burning rate relationships. Thus, powder grains coated or glazed with a lead compound to render them free-flowing are not operable in the invention.

The advantages of the gas-producing compositions of this invention over presently available formulations are readily apparent. T he compositions of this invention are characterized by distinguishing properties which have heretofore been found highly desirable but unobtainable; namely, a lower temperature coefficient of equilibrium pressure and a constant or more nearly constant burning rate over a wide pressure range within the zone of useful rocket pressures. Furthermore, by varying the carbon concentration in the gas-producing compositions of the invention within the prescribed limits, the burning rate of the plateau region, or region of low n value, may be greatly increased without shifting the plateau out of the zone of useful rocket pressures.

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

1. A gas-producing composition consisting essentially of a smokeless powder having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of at least one material selected from the group consisting 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 said material, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

2. A gas-producing composition consisting essentially of a smokeless powder having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of lead and an amount of finely-divided carbon not substantially exceeding the amount of lead, said gas-producing composition having a heat or explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressureburning rate relationship.

3. A gas-producing composition consisting essentially of a smokeless powder having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of lead oxide and an amount of finely-divided carbon not substantially exceeding the amount of lead oxide, said gasproducing composition having a heat of explosion not exceeding 900 calories per gram and having a value of 17 less than 0.7 for the .slope n of the line representing the pressure-burning rate relationship.

4. A gas-producing composition consisting essentially of a smolekless powder having uniformly incorporated therein and intimately admixed therewith within-each particle thereof an amount not exceeding of lead Z-ethylhexoate and an amount of finely-divided carbon not substantially exceeding the amountof lead Z-ethylhexoate, said gas-producing composition having a heat of explosion not exceeding 900-calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship,

5. A gas-producing composition'consisting essentially of a smokeless powder having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of a fatty acid, salt of lead and an amount of finely-divided carbon not substantially exceeding the amount of fatty acid salt of lead, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

6. A gas-producing composition consisting essentially of a smokeless powder having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount notexceeding 10% of lead stearate and an amount of finely-divided carbon not substantially exceeding the amount of lead stearate, said gasproducing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

7. A gas-producing composition consisting essentially of a smokeless powder containing from 85 to 95% nitrocellulose and having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of at least one material selected from the group consisting 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 said maiierial, said gasproducing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship. I

8. A gas-producing composition consisting essentially of a smokeless powder containing from 85 to 95 nitrocellulose and having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of lead and an -amount of finely-divided carbon not substantially exceeding the of a smokeless powder containing from 85 to 95% nitrocellulose and having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of lead oxide and an amount of finely-divided carbonnot substantially exceeding the'amount of lead oxide, said gasproducing composition having aheat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressureburning rate relationship.

'10. A gas-producing composition consisting essentially of a smokeless powder containing from 85 to 95 nitrocellulose and having uniformly incorporated therein and intimately admixed therewith each particle thereof an amount not exceeding 10% of lead 2-ethylhexoate and an amount of finely-divided carbon not substantially exceeding the amount of lead Z-ethylhexoate, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

11. A gas-producing composition consisting essentially of a smokelesspowder containing from 85 to 95% nitrocellulose and having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of a fatty acid salt of lead and an amount of finely-divided carbon not substantially exceeding the amount of fatty acid salt of lead, said gasproducing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relations hip. Y

12. A gas-producing composition consisting essentially of a smokeless powder containing from 85 to 95 nitrocellulose and having uniformly incorporatedtherein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of lead stearate and an amount of finely-divided carbon not substantially exceed-.

ing the amount of lead stearate, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

13. A gas-producing composition consisting essentially of a smokeless powder containing nitrocellulose and at least one explosive nitric ester and having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of at least one material selected from the group consisting 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 said material, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

14. A gas-producing composition consisting essentially of a smokeless powder containing nitrocellulose and at least. one explosive nitric ester and having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of lead and an amount of finely-divided carbon not substantially exceeding the amount of lead, said gasproducing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

15. A gas-producing composition consisting essentially of a smokeless powder containing nitrocellulose and at least one explosive nitric ester and having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of lead oxide and an amount of finely-divided carbon not substantially exceeding the amount of lead oxide, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

16. A gas-producing composition consisting essentially of a smokeless powder containing nitrocellulose and at least one explosive nitric ester and having uniformly incorporated therein and tintimlately admixed therewith within each particle thereof an amount not exceeding 10% of lead 2-ethylhexoate and an amount of finelydivided carbon not substantially exceeding the amount of lead Z-ethylhexoate, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship. v

17. A gas-producing composition consisting essentially of a' smokeless powder containing nitrocellulose and at least one explosive nitric ester and having uniformly incorporated therein and intimately admixed therewith of fatty acid salt of lead, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

18. A gas-producing composition consisting essentially of a smokeless powder containing nitrocellulose and at least one explosive nitric ester and having uniformly incorporated therein and intimately admixed therewith within each particle thereof an amount not exceeding 10% of lead stearate and an amount of finely-divided carbon not substantially exceeding the amount of lead stearate, said gas-producing composition having a heat of explosion not exceeding 900 calories per gram and having a value of less than 0.7 for the slope n of the line representing the pressure-burning rate relationship.

References Cited in the file of this patent UNITED STATES PATENTS 1,357,865 Henning Nov. 2, 1920 2,385,135 Holmes Sept. 18, 1945 2,498,388 Ball Feb. 21, 1950 2,982,638 Cooley May 2, 1961 v FOREIGN PATENTS 621,685 Great Britain Apr. 14, 1949

Claims (1)

1. A GAS-PRODUCING COMPOSITION CONSISTING ESSENTIALLY OF A SMOKELESS POWDER HAVING UNIFORMLY INCORPORATED THEREIN AND INTIMATELY ADMIXED THEREWITH WITHIN EACH PARTICLE THEREOF AN AMOUNT NOT EXCEDDING 10% OF AT LEAST ONE MATERIAL SELECTED FROM THE GROUP CONSISTING 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 SAID MATERIAL, SAID GAS-PRODUCING COMPOSITION HAVING A HEAT OF EXPLOSION NOT EXCEEDING 900 CALORIES PER GRAM AND HAVING A VALUE OF LESS THAN 0.7 FOR THE SLOPE N OF THE REPRESENTING THE PRESSURE-BURNING RATE RELATIONSHIP.