US3133841A

US3133841A - Solid propellants

Info

Publication number: US3133841A
Application number: US146165A
Authority: US
Inventors: Donald K Kuehl
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1961-10-19
Filing date: 1961-10-19
Publication date: 1964-05-19
Anticipated expiration: 1981-05-19

Description

May 19, 1964 D. K. KUEHL 3,133,841

Filed Oct. 19, 1961 2 Sheets-Sheet 1 I700 I' I G. I.

RELATIVE PAYLOAD IN POUNDS IT) so "I. Be ZAI 90 so 70 so 40 3o 20 IO 0 PERCENT OF EACH METAL BY WEIGHT IN BINARY MIXTURE INVENTOR DONALD K. KU EH L ATTORN EYS May 19, 1964 D. K. KUEHL 3,133

SOLID PROPELLANTS Filed Oct. 19, 1961 2 Sheets-Sheet 2 INVENTOR. DONALD K. KLJEl-IL ATTOR N EYS' 3,133,841 Patented May 19, 1964 United States Patent .Ofitice SOLID PROPELLANTS Donald K; Kuehl, Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Oct. 19, 1961, Ser. No. 146,165

20 Claims. (Cl. 149-5) 3 This invention relates to jet propulsion and more particularly to propellants having enhanced performance characteristics which are useful in connection therewith.

Although thepresent invention is capable of use in connection with a wide variety of transportation and military equipment, it is especially applicable in the field of aviation, to propel,'for example, missiles, rockets, jet aircraft and the like.

1 This application is a continuation-in-part of US. application Serial No. 86,613, filed February 2, 1961.

' It is an object of the present invention to provide means for enhancing the burning rate, efliciency of combustion, and specific'impulse of fuels.

It is another object of the present invention to provide fuels having enhanced burning rates, efliciency of combustionand specific impulse.

Still another object of the present invention is to provide metal additives which may be incorporated into fuel toimprove the performance characteristics thereof. .Other objects of the present invention will in part be obvious and will in part appear hereinafter.

Acc'ording to the invention described in the above identified co-pending application, it has been discovered that fuel performancecharacteristics are improved by the'addition of a mixture of. particular metals or metal alloys to propellants of the type'that comprise chemically combined, but available, oxygen and halogen. ,The mixtures of metals or metal alloys may be de scribed as systems which comprise one or more oxyphilic metals, i.e., metals having an afiinity for oxygen, and one or more halophilic metals, i.e., metals which have an affinity for halogen. By aifinity for halogen or oxygen is meant the preference of the metals to combine chemi cally with halogen or oxygen, respectively, at the temperature of combustion of the fuel.

Whether the metallic additives are alloys or mixtures of halophilic metals and oxyphilic'metals, the proportion of the halophilic metal or metals to the oxyphilic metal or metals in the additives should be carefully controlled.

. Assigning the halophilic and oxyphilic metals making up the additives disclosed herein their normal valences, the gram equivalent weight ratio of halophilic metal or metals to oxyphilic metalor metals in the mixtures and alloys making up the additives may vary between about 0.25 and 3.0, is usually between about 0.5 and 2.0, and is preferably between about 0.75 and 1.5 times the gram equivalent weight ratio of available halogen to available oxygen in the solid propellant. Optimum results are achieved when the gram equivalent weight ratio of halophilic metal or metals to oxyphilic metal or metals making up the metal additives is approximately equal to, or varies within percent of, the gram equivalent weight ratio of available halogen to available oxygen in the propellant.

By available halogen and available oxygen is meant halogen and oxygen which would leave the fuel or propellant, upon combustion, uncombined with other metals were it not for the presence of the additives disclosed herein.

Preferably, enough of the metallic additives disclosed herein should be added to the propellants to insure that there is adequate halophilic metal or metals present in the propellant to stoichiometrically react with the available halogen in the propellant, and enough of the oxyphilic metal or metals present to stoichiometrically react with the available oxygen present in the propellant. Although the amounts of halophilic and oxyphilic metals present in the fuels may vary, respectively, between about 25 and 300 percent of stoichiometric requirements, the amounts are usually between about and 150 percent, and preferably between about and percent of stoichiometric requirements.

As will be clear from the following, the amounts of the additives incorporated into the fuel will generally be a function of the oxygen and halogen stoichiometry of the fuel. In general, the additive will comprise at least about 1 percent, andusually at least about 5 percent or between about 5 and 40 percent by weight of the fuel.

In calculating the requirements of the oxyphilic metal, the amount of oxygen required to combine with the carbon in the binder (to form carbon monoxide) may be taken into consideration, and deducted from the total available oxygen, inasmuch as the oxygen combining with the carbon does not have to be taken up by the oxyphilic metal or metals. Likewise, in calculating the halophilic metal requirements, the halogen content of the hinder, or other materials incorporated into the fuel, if any, may be taken into consideration and added to the total halogen. Also, when chemicals are incorporated into the fuel which have halogen already combined with a metal,

e.g., .KClO LiClO and so' forth, the amount of halogen already combined with a metal may be deducted from the total available halogen. It should be noted in passing that the halogenlin such materials as KClO LiClO and so forth, is already combined with a metal, and hence is not available halogen, as that term is decsribed herein; r e

Whether or not a metal is oxyphilic or halophilic depends on a number of considerations, including free energy and temperature. Some materials, for example, exhibit halophilic characteristics at a given temperature and oxyphilic characteristics at other temperatures: Such metals, as will be obvious, may change from oxyphilic to halophilic, and vice versa, with temperature change. Whether or not a given material is halophilic also depends to a certain extent on other metals in the environment in which it finds itself. Thus, in the systems of metals described herein, acertain metal may be halophilic or oxyphilic depending upon the nature of the other metal or metals in the' system. The appropriately calculated free energies of the metals can be referred to, to indicate whether a particular metal will exhibit oxyphilic or halophilic characteristics in the system. Although based on free energy considerations,; there are potentially a large number of metal pairs or pairs of mixtures of metals which will be sufliciently different intheir aflini-ties for oxygen and halogens to be classified as oxyphilic-halophilic combinations, some of the metals in such potential combinations are more suitable for use in the present invention than are others. Thus, for'ex-ample, some of the metals suitable for use in such combinations, although satisfying the free energy requirements to be oxyphilic or halophilic, may have low heats of reaction, or low density, or other adverse properties, thereby rendering them less suitable for use than are metalswhioh have, for example, high heats of reaction and/or high density. Although all such metal pairs or pairs of mixtures of metals will follow the principles described hereinabove, the metals in the following series, because of density, heats of reaction and other pertinent properties, are especially suitable for use, and are preferred:

Beryllium Aluminum Zirconium Magnesium Silicon Boron Titanium Calcium Lithium Sodium As arranged in this series, the affinity of the metals for oxygen decreases from top to bottom, and the afiinity of the metals for halogen decreases from bottom to top.

As arranged in this series, if any pair of metals is selected, the first listed will be oxyphilic and the second listed will be halophilic for that particular pair. For example, beryllium, in combination with any other metal on the list, will be oxyphilic, while the other metal will be halophilic. Lithium, on the other hand, will be halophilic with any other metal on the list except sodium, for which case lithium is oxyphilic and sodium halophilic.

When pairs of mixtures of metals are employed, the metals making up the oxyphilic portion of the additive will be higher in the series than the metals making up the halophilic portion of the additive. Thus, for example, a suitable additive may comprise beryllium and aluminum as the oxyphilic portion and calcium and lithium as the halophilic portion. Other suitable pairs of metals or pairs of mixtures of metals will readily suggest themselves irom the foregoing description.

The pairs of metals or pairs of mixtures of metals forming an oxyphilic-halophilic system as described above enhance the burning time, efliciency of combustion and specific impulse, and, accordingly, the payload capacity of weight limited solid propellant rockets. Although systems of these oxyphilic and halophilic metals may enhance the described characteristics of volume limited solid propellant rockets, in general it may be said that the improvement in these characteristics with volume limited rockets is not as great as the improvement with weight limited rockets.

For weight limited solid propellant rockets, lithium is preferred as the halophilic metal; best results are achieved when it is used in combination with a metal or mixture of metals listed above it in the described metal series.

For volume limited solid propellant rockets, a mixture of aluminum and beryllium has been found to considerably enhance the performance characteristics of the fuel, as will be made clear hereinbelow. In this system, aluminum acts as the halophilic metal and beryllium as the oxphilic metal. The proportion of aluminum (halophilic metal) and beryllium (oxyphilic metal) added to the fuel is based on maximum density specific impulse, rather than on stoichiometry, however.

Although the metal additives comprising oxyphilic and halophilic metals may be added to a wide variety of fuels comprising oxygen and halogen, they are especially useful with propellants, and more particularly solid propellants, containing chemically combined but available halogen as, for example, 'in the oxidant portion of the propellant.

As examples of oxidants having available halogen chemically combined therewith may be mentioned ammonium and nitronium chlorate, bromate, iodate, fluorate, perchlorate, perbromate, periodate, perfluonate, and so forth. Other oxidants containing chemically combined but available oxygen and halogen will readily suggest themselves to those skilled in the 'It is clear from the foregoing that the oxidants for use in this invention are halogen containing non-metallic oxidants which release, on heating, free oxygen and free halogen;

In addition to the halogenated oxidizers described above, the solid propellants useful in carrying out the present invention may include a binder such as saturated or unsaturated hydrocarbons, halogenated hydrocarbons, polymeric organic compounds, and so forth. Thus, if desired, the binder for the solid fuel can be asphalt, cellulose, rubber, including natural rubber and synthetic rubbers such as butadiene-methylvinyl-pyridine copolymer or 'butadiene-styrene copolymer, or other suitable organic binder materials. If desired, a high energy nitropolymer, which could provide additional energy for the system, can also be used as the binder.

Depending on the nature of the binder, curing agents such as quaternizing or vulcanizing agents may be incorporated the-reinto. The propellant may also include suitable burning catalysts such as rouge, ammonium dichromate, Prussian blue, Milori blue, and the like.

The amount of binder incorporated with the powdered metal additive and the oxidant will ordinarily be the optimum amount required to maintain the powdered metal additive, the oxidant and other materials which may be present, in a coherent mass having the required (structural strength to withstand storage and handling. The utilization of ordinary techniques for the incorporation of fairly viscous polymeric compounds containing as little as 5 weight percent of binder, will produce a satisfactory solid product. A special technique will produce solid grains of powdered fuel containing as little as one weight percent of binder. This special technique comprises intimately admixing the powdered metal additive and oxidant, as, well as the other ingredients with an excess of a fluid binder material, such as lacquer or shellac, and centrifuging the mixture to remove excess fluid. Although there is really no upper limit to the amount of binder employed, when the binder is carbonaceous in nature, the amount of binder employed should be low enough to insure the availability of oxygen in excess of that required to stoichiometrically react with the carbon of the binder. Otherwise, there would be no available oxygen to combine with the oxyphilic metal; With this thought in mind, good results have been achieved with as high as 50% or more of binder, based on the weight of the fuel or propellant. After molding, or extruding, and curing, a dense charge of high structural strength is obtained.

Typical examples of the solid rocket propellants produced in accordance with the teaching contained herein are indicated in the following table:

TABLE I Formula 1, Formula 2, percent by percent by Weight Weight Ammonium perchlorate- 70 Hydrocarbon binder (CHI-I2) 10 15 Burning metal alloy 20 15 Typical examples of the burning metal alloy which may be used with the fuel compositions identified as '1 and 2 in Table I are indicated in Table I I.

The above examples of solid rocket formulations and metal alloys, it should be noted, are merely illustrative of operative embodiment of the present invention, and are not intended to limit the invention, except as such limitations may appear in the claims. The oxidizer and binder in Formulae 1 and 2, for example, may be any of those described hereinabove, and metal additives other than those described in Table II, may be used, as will be clear from the foregoing.

In the case of volume limited solid propellant rocket fuels having the general composition identified as 1 and 2 in Table 'I, an alloy or mixture of aluminum and beryllium comprising bet-ween about and 40 percent by weight beryllium is highly effective in enhancing the performance characteristics of the fuel. In general, the amount of said mixture or alloy added to the .volume limited solid propellant rocket fuel may vary between about 4 and 40 percent by weight of the fuel, and is preferably between about 15 and 25 percent by weight of the fuel.

The improvement in performance characteristics of fuels by carrying out the teachings of the present invention will be clear from the accompanying drawings.

.FIG. 1 is a plot of payload capabilities for a propellant comprising, by Weight, 70 percent ammonium perchlorate,

10 percent of solid hydrocarbon binder having the theoretical formula C H- and percent of a binary alloy of lithium and beryllium. FIG. 1 shows the effect of varying the proportions of lithium and beryllium on the payload capacity. The calculations for determining the payload capacity shown in FIG. 1 are made on a IBM 704 calculating machine programmed on the basis of isobaric, isenthalpic combustion and isentropic, adiabatic, reversible expansion through the nozzle from 1000 to 14.7 p.s.i.g. The payload capacities indicated in 'FIG. 1 are for a weight limited rocket of 18,000 pounds gross weight and 2100 mile range. As is apparent from FIG. 1, maximum payload capacity occurs when the binary metal additive comprises between about 18 and 40 percent by weight of lithium, and between about 82 and 60 percent by weight of beryllium.

. Although FIG. 1 is a plot of theoretical values, it is representative of the comparative improvement in performance for'the fuel systems indicated hereinabove.

FIG. 2 is a plot of relative payload capabilities in terms of density specific impulse for a propellant comprising 70 percent by weight ammonium perchlorate, 10 percent by weight of solid hydrocarbon binder having the formula C H and 20 percent by weight of a binary alloy of aluminum and beryllium. As may be seen from FIG. 2, the maximum payload capacity of the fuel is optimum when the composition of the binary alloy is between about 15 and 40 percent by weight of beryllium and 85 and 60 percent by weight of aluminum.

Although mixtures or alloys of the metals described herein may be employed, it should be understood that alloys are preferred for the reason that they may provide greater density of the metal components than does a mixture of metals, and will have superior combustion characteristics, as will be understood by those skilled in the art.

In making the fuels of the type described herein, it has been discovered that the 'oxyphilic and halophilic metals which are used to produce high energy do not always burn with high efliciencies.

Theburning efiiciency of the metal-additives is a function of many variables. For any given metal, however, the burning efiiciency can be generally said to vary invers'ely with the size of the particle sought to be burnedthe larger the particle the lower the burning efficiency.

For rapid burning rate and high burning efiiciency, it has been discovered that the metal additive should have an average particle size less than about 15 microns, and preferably less than 1 0 microns, or between about 0.001 and 10 microns. Many particles within this size range, however, have an extremely high surface to volume ratio and are pyrophoric. Accordingly, small metallic particles Particle Size Disadvantages Advantages Large (10 to 250 mi- Less efficiency be- Easy to handle; less crons). cause of low burndegradation being rate. cause of low surface area. Small (0.001 to 10 mi- Pyrophoric-large sur- Rapid burning leads crons face-volume ratio. to high burning efiiciency.

As will be clear from Table III and the foregoing discussion, there are disadvantages as well as advantages connected with the use of both large and small particle sizes. As may be seen, however, the problems connected with the use of small particles having an average particle size within the range 0.001 to 10 microns is primarily one of handling and storage. If such particles could be rendered non-pyrophoric under ordinary conditions of fuel preparation and storage, substantial advantages would accrue from their use.

According to the present invention, it has been discovered that small metal particles of the type under discussion and having an average particle size within the range of 0.001 to 10 microns, may be rendered non-pyrophoric by distributing the small metal particles, prior to incorporation into the fuel, into a matrix of a second, low melting or low boiling or readily decomposable metal element, or resinous material. The resulting mixture can then be handled in the form of sufiiciently large particles so as to reduce the reactivity and handling problem. The matrix masks the high surface to volume ratio of the small, pyrophoric particles, and renders them, in the matrix, practically inert.

The resulting composition, comprising a matrix of a low melting or low boiling or readily decomposable material having distributed therein highly reactive, extremely finely divided metal particles, when added to the fuel, leads to substantial improvement of combustion efiiciencies of the fuel.

When the matrix is dissipated, as by melting, or boiling, or decomposition, upon ignition of the fuel, there are released to the combustion zone a large number of the finely divided metal particles, which, because of their size, burn rapidly and completely to release enormous quantities of energy.

FIGURE 3 is a schematic illustration comparing the burning proper-ties of a particle of a pure metal with a powder of the same metal in a matrix of the type described.

As shown in FIGURE 3, 1 is a relatively large metallic particle, and 2 is a particle of the same size, but comprising a matrix 4 having extremely small metal particles 3 distributed throughout.

As indicated, the longitudinal axis AA in FIGURE 3 is a time axis, and the horizontal axis BB represents ig-' nition. At ignition, an arbitrary time of zero may be assigned. Time increases from the ignition axis in the direction of the arrow indicated on time axis AA, and the area below ignition axis BB represents the combustron zone.

Upon ignition, the particles 1 and 2 begin to burn in the combustionzone. With particle 2, the matrix 4 dissipates and releases the extremely fine particles 3 to the combustion zone. The fine powder burns rapidly, and combustion is complete in a relatively short period of time.

With the metal particle 1, however, combustion is slow,

and a considerable portion of the particle escapes from the combustion zone unburned, thereby leading to poor fuel efficiency.

In the combustion zone of FIGURE 3, 5 represents the unburned portion of metal particle 1, whereas 6 represents the consumed portion of the particle.

As may be seen from FIGURE 3, the metal powder of particle 2 is completely consumed in a relative time of 10 units, whereas with particle 1, after 40 time units, about one-half of particle 1 remains unburned.

As already indicated, the matrix in which the finely divided metal particles may be distributed should be capable of melting, volatiliz'ing or otherwise dissipating or decomposing at or about ignition temperature or below to release the extremely finely divided metal particles to the combustion zone.

As suitable materials for the matrix may be mentioned low melting and preferably low boiling metals or metal alloys having a melting point, and preferably a boiling point, below about 1200 F. Also may be mentioned such materials as sulfur and phosphorous which are solid at normal temperatures, e.g., room temperature, but which boil at relatively low temperatures. Also may be mentioned various Waxes, resins, fats and the like, which are susceptible of decomposition at relatively low temperatures.

Suitable resins include epoxy resins; silicone resins; cellulose derivatives, such as cellulose acetate, cellulose butyrate and the like; acrylic polymers and co-polymers; polyethylene and polypropylene resins; furane resins; polyarnides, such as nylon; styrene polymers and cpolymers; vinyl polymers and co -polymers; polyurethanes; polybutadiene acrylic acid polymers and terpolymers; and the like.

Of the resins mentioned, silicone resins are the least suitable and epoxy resins are poor because these materials do not decompose sufiiciently completely on heating and, therefore, tend to leave residues.

Of the resins mentioned, the polyurethane and polybutadiene acrylic acid polymers and terpolymers happen to give exceptionally good results and are preferred for use.

The matrix concept represents an advantageous means of introducing extremely small particles, i.e., 0.001 to 10 microns, of the oxyphilic and halophilic metals into the fuel compositions hereinabove discussed.

Thus, extremely small particles of the oxyphilic and halophilic metals may be distributed throughout the matrix materials described above and, in this manner, introduced into the fuel. The oxyphilic and halophilic metals may be introduced into the same or a different matrix. In the former embodiment, particles of an alloy of the oxyphilic and halophilic metals may, of course, be employed.

In a preferred embodiment, the halophilic or oxyphilic metal or metals may form the matrix for extremely finely divided particles of the other metal or metals.

For example, when it is desired to employ lithium as the halophilic metal and beryllium as the oxyphilic metal, particles of beryllium may be dispersed throughout a matrix of lithium.

As shown in FIGURE 4, beryllium particles 12 having a diameter of about 10 microns or less are dispersed in a matrix 10 of lithium, the size of the matrix being large in comparison to the size of the beryllium particles.

When the oxyphilic or halophilic metal forming the matrix for the other metal is susceptible to decomposition, the matrix can itself can be coated or encapsulated by a less reactive or inert metal or other material. Such an embodiment is shown in FIG. 5.

In FIGURE 5, small beryllium particles 20 are dis tributed in a matrix 22 of lithium, and the matrix is coated with a thin layer 25 about 10 microns thick of aluminum. When particles of the type shown in FIG- URE are used in the fuels disclosed herein, the alumi- 8 mum and beryllium will act as the oxyphilic metal, and the lithium as the halophilic metal.

As will be clear from FIGURE 5 and the foregoing description, the terms encapsulation and encapsulated, as used herein, refer to coating the matrix with a thin layer of a material stable and inert at ordinary conditions, but volatizable or decomposable below the ignition temperature of the fuel. The encapsulation technique, it should be pointed out, is necessary only when the matrix material is one that has a tendency to decompose at ordinary conditions. The encapsulation technique is different from and ought not to be confused with the matrix concept.

The boiling and melting points for the preferred oxyphilic and halophilic metals disclosed herein, arranged in the order described above, are as follows:

TABLE IV Boiling Melting Metal Point Point 0.) C.)

Beryllium 2, 970 1, 285 Aluminum 2, 447 660 2, 900 1, 857 1, 107 651 2, 355 1, 420 2, 550 2, 300 3, 000 1,800 1, 240 842 Lithium 1, 317 180. 5

For weight limited solid propellant rockets, as has already been indicated, lithium is the preferred halophilic metal. Because the melting and boiling point of lithium is lower thanor at least as low as-the melting and boiling point of most of the other metals in the series, this metal is a particularly good one to use for the matrix in preparing the Weight limited solid propellant rocket fuels disclosed herein. Any of the remaining metals in the series, i.e., beryllium, aluminum, zirconium, magnesium, silicon, boron, titanium, calcium, and mixtures of the foregoing, can be dispersed throughout the lithium matrix, to give suitable oxyphilic-halophilic systems. The particle size of the oxyphilic metals in the lithium matrix will be between about 0.001 and 10 microns. The granule size of the metal additive comprising the lithium matrix and the oxyphilic metal powder will be about 10 to 250 microns. In this embodiment, because the lithium forming the matrix is susceptible of decomposition at normal conditions, it is desirable to encapsulate or coat the matrix with a thin coating of an inert material. Those materials suitable to form the matrix material hereinabove, and which are stable at ordinary conditions, may be used for encapsulation, if desired.

Other suitable arrangements for the matrix and powdered metal, according to this embodiment, will readily suggest themselves to one skilled in the art from Table IV and the foregoing description.

In the case of volume limited solid propellant rocket fuels, as has been brought out hereinabove, the preferred metal additive is aluminum and beryllium. According to the teachings contained herein, this additive may be added in the form of an aluminum matrix having distributed therein beryllium particles having an average particle size of between about 0.001 and 10 microns.

In preparing the metal additive compositions, the matrix material may be first rendered fluid, and the finely divided metal powder intimately admixed therein. In handling the finely divided powder, adequate precautions, including inert atmospheres, should be used to guard against spontaneous ignition of the powder. The matrix material is then solidified or otherwise hardened. If desired, the composition may be molded or extruded prior to or simultaneously with solidification to increase its density. The resulting material may then be suitably comminuted or reduced in size to form particles varying in size from about 15 to 200 microns, and in this form,

introduced into the fuel, with suitable encapsulation, if required.

When resinous materials are employed, suitable hardening or curing agents may be used in a manner Well understood in the art.

Compositions in which the matrix material forms up to 60 percent by weight of the composition, or more, or

' between about 2 and 60 percent by weight, are especially suitable. The following examples are illustrative of the method of making the metal additives:

Example 1 Example 2 A liquid polybutadiene-acrylic acid copolymer of the type sold by Naugatuck Chemical Company and designated RF-l is used as the matrix material. This material is a copolymer of butadiene and acrylic acid typically' containing 0.065 equivalent of acid per 100 grams.

An alloy of lithium and beryllium containing 70 percent by weight of beryllium is reduced in size under an argon atmosphere to an average particle size of 0.001 to microns. The small alloy particles are intimately admixed with the resin in a. weight ratio of 4:1. An epoxide type curing agent is added to the resulting admixtureandthe resulting admixture heated to a temperature of about 120 until hard. The resulting material is then comminuted into particles having an average particle size of 10 to 250 microns.

The invention in its broader aspects is not limited to the specific details shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its hcief advantages.

What is claimed:

1. For use with solid propellant rocket fuels, an easy to handle, stable, rapid burning composition of matter in the form of granules having an average particle size of about 10 to 250 microns, said granules comprising a matrix of a material normally solid at ordinary temperatures which is a member selected from the group consisting of low melting metals and alloys, phosphorus and sulfur, the matrix having imbedded therein a plurality of finely divided particles of a pyrophoric metal, the average particle size of the pyrophoric metal being less than about 10 microns, the matrix material at ordinary temperatures serving to prevent ignition of the imbedded particles of pyrophoric metal but being capable of dissipating at temperatures below about 1200 F. to release the finely divided particles of the pyrophoric metal.

2. For use with solid propellant rocket fuels, an easy to handle, stable, rapid burning composition of matter in the form of granules having an average particle size of about 10 to 250 microns, said granules comprising a matrix of a material normally solid at ordinary temperatures which is a member selected from the group consisting of low melting metals and metal alloys, sulfur and phosphorus, the matrix having imbedded therein a plurality of finely divided particles of a pyrophoric metal which is a member selected from the group consisting of beryllium, aluminum, zirconium, magnesium, silicon, boron, titanium, calcium, lithium, sodium, and mixtures of the foregoing, the particles of the pyrophoric metal 10 having an average size of less than about 10 microns, the matrix material at ordinary temperatures serving to prevent ignition of the imbedded particles of pyrophoric metal but being capable of dissipating at temperatures below about 1200 F. to release the finely divided particles of pyrophoric metal.

3. For use with solid propellant rocket fuels, an easy to handle, rapid burning composition of matter in the form of granules having an average particle size of between about 10 and 250 microns, said granules consisting essentially of a matrix of lithium having distributed throughout finely divided particles of a pyrophoric metal selected from the group consisting of beryllium, aluminum, zirconium, magnesium, silicon, boron, titanium, calcium and mixtures of the foregoing, the average particle size of the pyrophoric metal imbedded in the lithium matrix being less than about 10 microns.

4. The composition of matter of claim 3 wherein the granules are coated with a thin film of aluminum.

5. For use with solid propellant rocket fuels, an easy to handle, stable, rapid burning composition of matter in the form of granules having an average particle size of between about 10 and 250 microns, said granules consisting essentially of a matrix of aluminum having imbedded therein a plurality of finely divided discrete particles of beryllium, the average particle size of the beryllium being less than about 10 microns.

6. A solid propellant fuel comprising the granular composition of matter of claim 1, a hydrocarbon containing binder, and a halogen containing non-metallic oxidizer which is capable of being decomposed on heating to release free oxygen and free halogen for combination with the pyrophoric metal of the granules.

7. A solid propellant fuel comprising the granular composition of matter of claim 2, a hydrocarbon containing binder, and a halogen containing non-metallic oxidizer which is capable of being decomposed on heating to release free oxygen and free halogen for combination with the pyrophoric metal of the granules.

8. A solid propellant rocket fuel comprising the granular composition of matter of claim 3, a hydrogen containing binder, and a halogen containing non-metallic oxidizer which is capable of being decomposed on heating to release free oxygen and free halogen for combination with the metals of the granules.

9. A solid propellant rocket fuel comprising the granular composition of matter of claim 4, a hydrogen containing binder, and a halogen containing non-metallic oxidizer which is capable of being decomposed on heating to release free oxygen and free halogen for combination with the metals of the granules.

10. A solid propellant rocket fuel comprising the granular composition of matter of claim 5, a hydrocarbon containing binder, and a halogen containing nonmetallic oxidizer which is capable of being decomposed on heating to release free oxygen and free halogen for combination with the metals of the granules.

11. The solid propellant fuel of claim 6 wherein the oxidizer is a member selected from the group consisting of ammonium and nitronium chlorates, bromates, fluorates, perchlorates, perborates, periodates, perfluorates, and mixtures of the foregoing.

12. The solid propellant fuel of claim 7 wherein the oxidizer is a member selected from the group consisting of ammonium and nitronium chlorates, bromates, fluorates, perchlorates, perborates, periodates, and perfluorates, and mixtures of the foregoing.

13. The solid propellant fuel of claim 8 wherein the oxidizer is a member selected from the group consisting of ammonium and nitronium chlorates, bromates, fluorates, perchlorates, perborates, periodates, and perfluorates, and mixtures of the foregoing.

14. The solid propellant fuel of claim 9 wherein the oxidizer is a member selected from the group consisting of ammonium and nitronium chlorates, bromates, fluorates, perchlorates, perborates, periodates, and perfiuorates, and mixtures of the foregoing.

15. The solid propellant fuel of claim wherein the oxidizer is a member selected from the group consisting of ammonium and nitronium chlorates, bromates, fluorates, perchlorates, perborates, periodates, perfiuorates, and mixtures of the foregoing.

16. A solid fuel composition comprising an intimate mixture of a halogen containing non-metallic oxidizer which is a member selected from the group consisting of ammonium and nitronium chlorates, bromates, fluorates, perchlorates, perborates, periodates, perfluorates, and mixtures of the foregoing, and capable of decomposing to release free oxygen and free halogen upon being heated, a hydrocarbon containing binder, and at least one oxyphilic and one halophilic metal selected from the group consisting of beryllium, aluminum, zirconium, magnesium, silicon, boron, titanium, calcium, lithium, sodium, the indicated arrangement of metals in the series being such that the affinity for oxygen decreases from top to bottom of the series and the affinity for halogen decreases from bottom to top of said series, so that, if any pair of metals is selected from the series, the first listed is oxyphilic and the second listed is halophilic, the gram equivalent weight ratio of the oxyphilic metal to the halophilic metal in the fuel being between about 0.25 and 3.0 times the gram equivalent weight ratio of available oxygen to available halogen in the fuel composition; at least one of the metals being in the form of granules having a particle size of about 10- to 250 microns, said granules comprising a matrix of a material normally solid at ordinary temperatures having irnbedded therein finely divided particles of said metal of an average size of less than about 10 microns, the matrix material of said granules serving to prevent ignition of the imbedded particles of metal at ordinary temperatures but being capable of dissipating at temperatures below about 1200 F. to release the finely divided particles of metal.

17. The fuel composition of claim 16 wherein the halophilic metal is lithium and the oxyphilic metal is a member selected from the group consisting of beryllium, aluminum, zirconium, magnesium, silicon, boron, titanium, calcium, and mixtures of the foregoing, and wherein the oxyphilic and halophilic metals are present in the fuel in the form of granules having an average particle size of from about 10 to 250 microns and comprise an encapsulated matrix of lithium having dispersed therein finely divided particles of the oxyphilic metal, the finely divided particles of the oxyphilic metal in the lithium matrix having an average particle size between about 0.001 and 10 microns.

18. The fuel composition of claim 16 wherein the oxyphilic metal is beryllium and the halophilic metal is aluminum and wherein the aluminum and beryllium are present in the fuel in the form of granules having an average particle size of from about 10 to 250 microns and comprising a matrix of aluminum having dispersed therein beryllium particles of an average size of less than 10 microns.

19. The fuel composition of claim 16 wherein the amount of the oxyphilic metal is between about and percent of that stoichiometrically required to combine with the available oxygen, and the amount of the halophilic metal is between about 95 and 105 percent of that stoichiometrically required to react with the available halogen.

20. The solid propellant fuel of claim 16 wherein the gram equivalent weight ratio of the oxyphilic metal to the halophilic metal is approximately the gram equivalent weight ratio of available oxygen to available halogen in the fuel, and wherein the combined weight of oxyphilic metal and halophylic metal is about 1 to 40 percent, based upon the Weight of the fuel.

References Cited in the file of this patent UNITED STATES PATENTS 2,926,613 FOX Mar. 1, 1960 2,995,431 Bice Aug. 8, 1961 3,010,815 Pierce et al Nov. 28, 1961

Claims

1. FOR USE WITH SOLID PROPELLANT ROCKET FUELS, AN EASY TO HANDLE, STABLE, RAPID BURNING COMPOSITION OF MATTER IN THE FORM OF GRANULES HAVING AN AVERAGE PARTICLE SIZE OF ABOUT 10 TO 250 MICRONS, SAID GRANULES COMPRISING A MATRIX OF A MATERIAL NORMALLY SOLD AT ORDINARY TEMPERATURES WHICH IS A MEMBER SELECTED FROM THE GROUP CONSISTING OF LOW MELTING METALS AND ALLOYS, PHOSPHOROUS AND SULFUR, THE MATRIX HAVING IMBEDDED THEREIN A PLURALITY OF FINELY DIVIDED PARTICLES OF A PHYROPHORIC METAL, THE AVERAGE PARTICLE ZIE OF THE PYROPHORIC METAL BEING LESS THAN ABOUT 10 MICRONS, THE MATRIX MATERIAL AT ORDINARY TEMPERATURES SERVING TO PREVENT IGNITION OF THE IMBEDDED PARTICLES OF PYROPHORIC METAL BUT BEING CAPABLE OF DISSIPATING AT TEMPERATURES BELOW ABOUT 1200*F. TO RELEASE THE FINELY DIVIDED PARTICLES OF THE PYROPHORIC METAL.