FI91147C - Chlorine-based rocket propellant - Google Patents

Description

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The present invention relates to the improvement of solid rocket propellants used in paint, fireworks, rescue, lighting missiles and other types of aircraft, such as artillery or military use, such as artillery and aircraft. Possibly the propellants according to the invention could also be used in gas generators for overflow munitions.

Solid rocket propellants based on the use of perchlorates, nitrates, picrates, nitramines, nitro compounds, oxides and nitric acid esters as oxidants are previously known. Examples of these are extensively mentioned, for example, in George P. Sutton, Rocket Propulsion Elements (1990), 5th Edition, T. Urban, Chemistry and Technology of Explosives, vol. 3 (1967) and vol. 4 (1985), U.S. Pat. patents 3725154, 3756874, 3722421, 3741830, 3779822, 3784422, 3734789, 3797238, 3753813 and 3671341.

Most of the current propellants are based on either nitric acid esters (smokeless gunpowder) or ammonium perchlorate as oxidizing agents. The binder is in the foregoing cellulose nitrate and in the latter is a generally elastic polymer such as polyurethane, polyvinyl chloride, polybutadiene and its copolymers, polysulfides, polyisoprene, polyethylene ethers, polyesters and polyethers, polyoxyamides, polyoxy polymers, epoxy polymers, polypropylene, polyethylene, oxetane copolymers such as bis- (azidomethyl) oxetane-styrene copolymer or other possible liquid, powdery, plastic or thermoplastic polymers.

The above-mentioned propellants are known for their high pressure exponent and sensitivity to sudden changes in fire pressure. Due to the high pressure exponent, the propellant is sensitive to changes in the cross-sectional area of the nozzle, which can occur as a result of nozzle erosion or scaling. Such events can lead to sudden changes in fire pressure, which usually result in the rocket being extinguished, the fire becoming uneven (ying), resonant phenomena, or even the rocket exploding.

Solid propellants are also characterized by minimum fire pressure and associated difficult flammability. At a pressure below the minimum fire pressure, combustion is uneven or the propellant is extinguished. Ignition therefore requires a special igniter with which the chamber pressure of the rocket is brought close to the operating pressure and at the same time a large amount of hot gases and particles are generated which ignite the propellant. This igniter increases the complexity of the rocket and thus the cost, as well as makes it difficult to implement the rocket and impairs the reliability of the rocket.

Known propellants also invariably contain fire catalysts and ballistic additives to control the rate of fire and its pressure dependences. The properties of the propellant are particularly sensitive to the size of these ingredients, their grain size, and even the shape of their particles. The ballistic additives currently used are disadvantageous in terms of energy production and reduce the specific and volumetric impulse of the propellant. Known additives produce only a fraction of the energy produced by the reaction of an oxidant and a binder in combustion.

It is known that in order to obtain a sufficient rate of fire, the grain size of the oxidant used in current propellants must be small or very small, typically less than 25-50 micrometers. The small grain size causes great difficulties in mixing, as the mixture of polymer and finely divided solid oxidant has a very high viscosity. The small size of the grain also causes the need for grinding; Grinding the most common oxidant, ammonium perchlorate, is an explosive operation. Furthermore, the mixing and fire properties of propellants mixed from a finely divided oxidant are sensitive to the grain size and its distribution. The manufacturing process must therefore be precisely controlled and, in practice, difficult to carry out in the case of both composite propellants and smokeless powders.

The most commonly used propellants are characterized by a rather low density, which usually ranges from 1400 kg / m3 to 1750 kg / m3. The resulting charging density is quite small, considering that the flow of the flue gases must also be left in the form of a flue or between the propellant and the vessel.

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The disadvantages of the known propellants are undoubtedly the difficult ballast to be controlled and the difficult ignitability, as well as the demanding manufacturing process. The propellant according to the invention provides a par dose or a decisive par dose for all the above-mentioned disadvantages. In order to achieve this, the propellant according to the invention is characterized by what is stated in the characterizing part of claim 1. The main advantages of the propellant according to the invention are improved fire and ignition properties, a simplified and simplified manufacturing process, a higher density and volume impulse, and mechanical and thermal insensitivity compared to known mixtures.

In terms of its combustion properties, the propellant according to the invention has clear advantages over known propellants. The propellant according to the invention does not tend to be extinguished, as is known, if the chamber pressure varies, for example as a result of damage to the nozzle. Current propellants turn off, tend to cough or resonate, or even detonate if the pressure fluctuates rapidly. The propellant according to the invention has a lower or the same pressure exponent compared to known perchlorate propellants, as can be seen by comparing the mixtures of Examples 1 and 2 and 3 and 4. It is clear from the examples that even a coarse oxidant achieves a high fire rate. It is possible to increase the rate of combustion at least twice by reducing the grain size of the oxidant alone, although the advantage of easy mixing is lost.

Since the ballistic additive according to the invention is itself an effective oxidant, the specific impulse is not significantly reduced by the addition, unlike when known ballistic additives are used, such as iron (in) oxide, lead chromate, iron (in) acetonyl acetate, copper and chromite, especially copper chromite, heavy chromite, cobalt benzoates, salicylates, naphthalene carboxylates and phthalates. When using the additive according to the invention, the properties of the propellant are not sensitive to the grain size of the additive or to small changes in the concentration, since the additive can be used even in the highest concentrations. When there is a lot of additive in the mixture, the variation of the properties of the substance has a relatively small effect on the properties of the mixture.

The burning rate of the propellant according to Example 1 is 17 mm / s at a pressure of 70 bar. The pressure exponent is 0.44 when polyurethane is used as a binder. By using known ballistic additives, the rate of fire can still be increased and the pressure exponent decreased somewhat. With the most commonly used oxidant, ammonium perchlorate, achieving the corresponding burning rate with the binder used in Example 4 is difficult and requires the use of a very fine oxidant. The fire rate of the known mixture 2 corresponding to Example 1 is 6 mm / s at a pressure of 70 bar and the pressure exponent is 0.68.

The manufacturing process is simplified, as auxiliaries and oxidant grinding are not necessarily required unless a very fast-burning propellant is desired. Furthermore, the crystalline form of the additive used in the propellant according to the invention is very advantageous for mixing. In addition, the crystal density of the substance is high, so its volume fraction in the finished mixture remains small. In this case, the propellant mixture is flowable and easy to cast, even if the propellant contains a lot of solids. At the same time, the density of the propellant increases, which is very advantageous in terms of volume impulse. Wetting agents or a tight grain size distribution of the oxidant do not need to be used to facilitate mixing unless the solids content is very high or the oxidant is very finely ground. Mixing is thus easy, as the viscosity of the mixture remains low. The propellant according to Example 1 is fully flowable even at a solids content of 86% without the use of wetting agents. Even a solids content of more than 90% can be used, but the alloy mixture is no longer free-flowing and the use of wetting agents becomes necessary. The high solids content and dense solids also facilitate the removal of gases from the mixture.

The propellant according to the invention is highly flammable when used in a rocket. A rocket made of a propellant according to the invention, such as the mixtures of Examples 1 and 3, does not require a special igniter, but reliably starts with a small amount of an igniting mass, for example black powder. It is also not necessary to increase the working pressure to the working pressure, since the propellant according to the invention does not, if desired, have a lower limit of combustion pressure, unlike known propellants. The propellant burns stably from normal pressure. The propellant also does not cough at start-up or resonance during combustion nearly as easily as with known propellants.

The advantage of the propellant according to the invention is also achieved in the loading density, since the propellant is denser than known. The density of the propellant of Example 1 is 1910 kg / m 3, of the propellant of Example 3 2090 kg / m 3, while the densities of the respective known mixtures 2 and 4 are 1680 kg / m 3 and 1840 kg / m 3. If an oxidant with a suitably distributed grain size and less binder is used, the density will be even higher and at the same time mixing will be easier. Using Examples 1 and 2 I! The specific impulse for the oxidants according to 5 91147 is approximately the same as for ammonium perchlorate propellants in general, 2300 to 2600 Ns / kg. However, the volume impulse is about 10% higher due to the higher density. The importance of a large volume impulse is particularly emphasized in slow-moving missiles, such as naval missiles, artillery missiles, and the early stages of a multi-stage missile. The use of the lithium salt according to the invention gives a higher specific impulse, 2400-2800 Ns / kg depending on the binder. The volume impulse also increases in the same proportion, since the density when using the lithium compound is approximately the same as with the oxidant of Examples 1 and 2. The real impulse is also increased by the condensation of the metal chloride contained in the combustion gases as it passes through the nozzle, whereby the latent thermal energy of the salt is used. A similar phenomenon does not occur if the flow is completely gaseous, as is the case with smokeless powders and several known composite propellants.

Contrary to good flammability, the propellant of the invention is less sensitive to ignition by mechanical stimuli than known ammonium perchlorate mixtures or other propellants such as smokeless gunpowder. The mixing of the propellant can thus be carried out with the same or similar means as the mixtures of the present. Thermally, the propellants according to the invention are also less sensitive to powders and known perchlorate propellants, so the propellants according to the invention are also excellently suitable for preparation by the so-called plastisol method. The impact test according to BAM (Bundesanstalt fur Materialpriifimg) has obtained an impact sensitivity of 25 cm for a known propellant made of ammonium perchlorate, polybutadiene and aluminum powder with a 1 kg hammer. With the mixture according to Example 1, the impact sensitivity with a one kilogram hammer is 40 cm. The load of the abrasion sensitivity test according to BAM with the same ammonium perchlorate propellant is 18 kp, with the propellant of Example 1 22 kp. The flash point according to BAM for the ammonium perchlorate propellant is 260 ° C, for the propellant of Example 1 330 ° C. The impact sensitivities of smokeless powders vary from 5 cm to 20 cm with a 1 kg hammer, the abrasion sensitivities from 8 kp to 18 kp and the bump points from 160 ° C to 190 ° C in BAM experiments. Due to the high density, the propellant according to the invention is also very difficult to detonate, which further increases its safety in use.

Advantages include the domestic raw materials of the propellant according to the invention. With the exception of smokeless gunpowder, the raw materials for known propellants are dependent on imports. The additive used in the propellant according to the invention is domestic. In addition, the substance is cheap, its price is 6 1 / 2..1 / 10 of the price of commonly used materials. If the additive is used in high concentrations, the propellant also becomes more advantageous. Example mixture 1 is made of domestic materials, with the exception of aluminum and ammonium perchlorate, when the binder is polyurethane.

Examples of propellants according to the invention and known are: 1. ammonium peridorate 56.3% by weight sodium chlorate 10.7 aluminum 17.0 "polyurethane or ΗΓΡΒ 15.5"

Sodium chlorate grain size distribution: more than 2 mm 35% by weight 1 - 2 mm 55 less than 1 mm 10

Grain size distribution of ammonium perchlorate: more than 1 mm 2% by weight 0.5 to 1 mm 13 0.25 to 0.5 mm 31 0.125 to 0.25 mm 42 0.067 to 0.125 mm 9 less than 0.067 mm 3

The aluminum powder is ground to a grain size of about 50 micrometers.

The fire rate of the mixture of Example 1 at a pressure of 70 bar is 17 mm / s and the pressure exponent when polyurethane is 0.44 and when HTPB is 0.06. The minimum fire pressure is about 3 bar polyurethane as binder and about 2 bar HTPB as binder. The density of the mixture is 1910 kg / m3.

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It should be noted that sodium chlorate and ammonium perchlorate are not compatible in the mixture of Example 1. However, this is not a disadvantage, as long as it is ensured that the substances in question do not get mixed up with each other, i.e. they are not added to the mixture at the same time. Despite the incompatibility of the individual materials, the finished mixture has been found to be very stable, as shown by the results of the previously mentioned sensitivity tests.

Known mixture: 2. ammonium perchlorate 65.0% by weight polyurethane or HTPB 18.5 "

aluminum 16.0 M

copper oxide 0.4 "potassium dichromate 0.6"

The combustion rate of the propellant of Example 2 at 70 bar is 6 mm / s and the pressure exponent is 0.68 when polyurethane is used and 0.31 when HTPB is used. The grain sizes of aluminum and ammonium perchlorate are the same as above. The minimum fire pressure of the mixture is about 15 bar as polyurethane binder and about 10 bar as HTPB binder. The density is 1680 kg / m3.

3. Potassium perchlorate 38.0 weight percent sodium chlorate 35.0 "aluminum 9.0" epoxy resin 18.0 "

Grain size distribution of potassium perchlorate: more than 0.25 mm 6% by weight 0.25 to 0.125 mm 28 0.067 to 0.125 mm 54 less than 0.067 mm 12

The mixture of Example 3 burns at 32 mm / s at a pressure of 70 bar and the pressure exponent of the mixture is 0.72. The minimum fire pressure is about 5 bar and the density is 2090 kg / m3. The particle size distribution of sodium chlorate is 8 s ama as before.

Known alloy: 4. potassium perchlorate 69.0 weight percent aluminum 9.0 "epoxy resin 22.0"

The fire rate of the mixture of Example 4 is about 25 mm / s at a pressure of 70 bar and the pressure exponent is 1.0 or more. Accurate values are not available, as they are particularly difficult to measure due to the high pressure exponent and minimum combustion pressure. The minimum fire pressure is about 30 bar and the density is 1840 kg / m1.

As the polyurethane of the examples, Civiol 7007 polyol and MDI (methylene bis (phenyl isocyanate)) manufactured by Neste Oy can be used. HTPB can be used, for example, in the R-45M of Arco's PolyBD resin. The epoxy resin used is, for example, DER-332 resin manufactured by Dow Chemical, the hardener of which is polyamine and the plasticizer of dibutyl phthalate.

In particular, it should be noted that ballistic additives other than those mentioned in the examples, which fall within the definition of the characterizing part of claim 1, can also be used in the propellant according to the invention. In addition, the compositions may contain binders and oxidants other than those mentioned in the examples, at least those listed in connection with the description of the prior art at the beginning of this appendix. Furthermore, the compositions may contain, as a propellant, metal in a suitable form, stabilizers, phlegmatizers, known ballistic additives such as pressure exponent, fire rate dependence and erosion control, plasticizers, wetting agents and other possible additives. In this and the mentioned examples, it is not intended to limit the invention in any way to the examples only, but many, not even mentioned, variations of the invention are possible within the scope of the inventive idea defined by the following claims.

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Claims (2)

91147 A propellant for rockets, consisting of a mixture of known oxidizing agents, binders, metals, wetting agents, ballistic additives, stabilizers, fire catalysts, phlegmatizers, plasticizers and possible other known additives, propellants, propellants, propellants and propellants. 1.5-40% by weight of lithium, sodium, barium or other metal chlorate as an impurity or other additive affecting the internal ballistics of the propellant. Propellant according to Claim 2 or 3, characterized in that it consists of a mixture of the following substances: Wear oxidant, binder, metaller, antifreeze, ballistic catalyst, stabilizer, stabilizer, phlegmatic medium, myrtle and and other mole, Kill tensate, wax, medium, lead-free, lead-free a bran-nkatalysator, som en reglare av tryckexponent eller antåndningsegenskaper eller som ett annat tillsatsåmne påverkande drivmediets innerballistik. 2. Drivmedel enligt patentkrav 1, k å η n e t e c k n a t av, att det består av blandning av foljande åmnen: 1 ammonium perchlorat ca. 55% sodium chlorate ”10” Aluminum "17" polyurethane or HTPB "18"