Composite propellant with reduced burning rate

Abstract

The invention relates to a composite solid propellant comprising: - a crosslinked polyurethane-type binder, which is the reaction product of a polymer polyol and a polyisocyanate-type crosslinking agent, in the presence of a crosslinking catalyst; - ammonium perchlorate; - optionally aluminum; - optionally a ballistic modifier; - at least one additive comprising a functionalized organic compound comprising from 10 to 65 carbon atoms.

Description

[0001] Reduced-burning composite propellant

[0002] Technical field of the invention

[0003] The present invention lies in the technical field of solid propellant propulsion and more specifically relates to composite solid propellants with reduced combustion speed. The invention also relates to the use of these propellants.

[0004] State of the art

[0005] Rocket propulsion is a propulsion method used in space applications (satellite launchers, satellites, orbital stations) and military applications (missiles). In the aerospace sector, solid propellant engines are highly valued for their performance and compact size. Solid propellants are inherently very dense, and therefore generate a greater quantity of propellant gases for the same volume of spacecraft than liquid propellants, resulting in a reduced structural weight. Furthermore, these engines are relatively easy to install, giving them a lower structural mass than cryogenic engines. Finally, their operation requires no moving parts, thus reducing the risk of failure. For these reasons, this type of engine remains a preferred option in the design of missiles for military applications and launchers such as the Ariane rocket.

[0006] Propellants can be divided into two families according to their composition. The first family, historically the oldest, includes propellants composed of nitrocellulose, a solid cellulose that absorbs liquid nitroglycerin, as well as additives. These homogeneous propellants are known as "dual-base" propellants. Indeed, each of these two energetic materials combines both the oxidizing and reducing agents. Their performance is not very high, but they are generally smokeless (except in the presence of metallic additives), which has contributed to their use in the design of tactical missiles. The second family of propellants is known as "composite" propellants. They are typically composed of a solid phase held together by a synthetic gum, the binder (typically polybutadiene), the whole forming a heterogeneous mass.Adding metallic powder (such as aluminum) increases the propellant's density and performance. Composite propellants offer significantly better performance than dual-base propellants and are widely used in space applications.

[0007] Application FR-A-3 139 819 describes a composite solid propellant comprising a crosslinked binder obtained from a polyester polyol and a polyisocyanate-type crosslinking agent, ammonium perchlorate, and optionally aluminum. The tested propellants have a burning rate of approximately 9 to 12 mm / s in a pressure range of 5 MPa to 10 MPa.

[0008] US patent application 2019 / 016645 describes a solid propellant comprising a reaction product between a PBHT (polybutadiene hydroxytelechelic) or PEHT (polyether hydroxytelechelic) prepolymer, a diol dimer, and a curative isocyanate. The tested propellants have a burning rate of approximately 0.3 inches per second (ips), or about 7.6 mm / s. However, the pressure at which the burning rate was determined is not specified.

[0009] US patent application 2019 / 077725 describes a solid propellant comprising PBHT-type, diol dimer and isocyanate.

[0010] The combustion rate of a solid propellant depends on the pressure P prevailing in the combustion chamber and classically follows a law (known as Vieille's law) expressed in the form:

[0011] Vc = aP n .

[0012] The combustion speed Vc and the pressure exponent n of the propellant are fundamental parameters for the ballistic tuning of a solid propellant engine (burn time, thrust, combustion stability, etc.). They determine the steady-state operating point of the engine at any given moment during firing.

[0013] It is understood that reducing the burn rate of a solid propellant could be advantageous, for example, in terms of propellant burn time, provided that the fuel's energy and mechanical performance are not affected. Several solutions could contribute to achieving this objective. One solution is to avoid using a ballistic catalyst; a complementary solution would be to identify an advantageous isocyanate as a precursor to the polyurethane matrix. However, this potential solution is not sustainable (in terms of raw material supply). It is to the credit of inventors to propose composite solid propellants with a burn rate suitable for space and strategic applications, in particular a burn rate ranging from approximately 5 to approximately 9 mm / s in a pressure range of approximately 5 MPa to approximately 10 MPa.

[0014] Summary of the invention

[0015] According to one aspect, the invention relates to a composite solid propellant comprising:

[0016] - about 5.0% to about 20.0% by mass of a crosslinked polyurethane-type binder, which is the reaction product of a polyol polymer and a polyisocyanate-type crosslinking agent, in the presence of a crosslinking catalyst;

[0017] - approximately 20.0% to approximately 90.0% by mass of ammonium perchlorate; - 0% to approximately 25.0% by mass of aluminium;

[0018] - 0% to approximately 5.0% by mass of a ballistic catalyst;

[0019] - 0.1% to about 20.0% by mass of at least one additive, said at least one additive comprising a functionalized organic compound comprising 10 to 65 carbon atoms, said functionalized organic compound having at least one secondary aziridine, epoxide or amine function.

[0020] According to another aspect, the invention relates to the use of the aforementioned composite solid propellant as fuel for a rocket, satellite or missile engine.

[0021] Description of the figures

[0022] Figure 1 shows the comparative combustion rates of PBHT binder compositions.

[0023] Figure 2 shows the comparative combustion rates of PBHT binder compositions with other filler particle sizes.

[0024] Description of the invention

[0025] According to one aspect, the invention relates to a composite solid propellant comprising:

[0026] - about 5.0% to about 20.0% by mass of a crosslinked polyurethane-type binder, which is the reaction product of a polyol polymer and a polyisocyanate-type crosslinking agent, in the presence of a crosslinking catalyst;

[0027] - approximately 20.0% to approximately 90.0% by mass of ammonium perchlorate;

[0028] - 0% to approximately 25.0% by mass of aluminium;

[0029] - 0% to approximately 5.0% by mass of a ballistic catalyst;

[0030] - 0.1% to about 20.0% by mass of at least one additive, said at least one additive comprising a functionalized organic compound comprising 10 to 65 carbon atoms, said functionalized organic compound having at least one secondary aziridine, epoxide or amine function.

[0031] Of course, the sum of the quantities of the different constituents of the composite solid propellant is equal to 100%.

[0032] For the purposes of this invention, "functionalized organic compound" means a compound capable of binding - via the function(s) it carries - to ammonium perchlorate and thus having an impact on the combustion rate of the propellant.

[0033] In some embodiments, the functionalized organic compound is obtained from a precursor organic compound, comprising 10 to 65 carbon atoms, chosen from a diacid or diol dimer, such as those marketed by Cargill under the name Pripol™, a polyester polyol, such as those marketed by Cargill under the name Priplast™, or a polyamine, preferably a diamine, such as those marketed by Cargill under the name Pria mine™.

[0034] In some embodiments, the functionalized organic compound comprises from 10 to 30 carbon atoms. In some embodiments, the functionalized organic compound comprises from 30 to 50 carbon atoms. In some embodiments, the functionalized organic compound comprises from 50 to 65 carbon atoms. In some embodiments, the functionalized organic compound comprises from 50 to 60 carbon atoms. In some embodiments, the functionalized organic compound comprises from 25 to 65 carbon atoms. In some embodiments, the functionalized organic compound comprises from 25 to 60 carbon atoms. In some embodiments, the functionalized organic compound comprises from 25 to 50 carbon atoms. In some embodiments, the functionalized organic compound comprises from 30 to 65 carbon atoms. In some embodiments, the functionalized organic compound comprises from 30 to 60 carbon atoms.In some embodiments, the functionalized organic compound comprises 10 to 25 carbon atoms. In some embodiments, the functionalized organic compound comprises 15 to 25 carbon atoms. In some embodiments, the functionalized organic compound comprises 20 to 30 carbon atoms.

[0035] The functionalized organic compound defined above contains (possesses) at least one aziridine, epoxide, or secondary amine functional group; advantageously, the functionalized organic compound contains (possesses) at least one secondary amine functional group, for example, at least two secondary amine functional groups. As an example, the scheme below shows the reaction of a diamine-type precursor organic compound with acrylonitrile to give a functionalized organic compound containing two secondary amine functional groups: The organic compound of the diamine type is represented by the following structure: being commercially available under the name Priamine™ (Cargill). Such a functional organic compound comprises 30 to 50 carbon atoms.

[0036] The polyol polymer is typically a hydroxytetracheal polybutadiene (PBHT), for example, the one marketed under the name R45HT™ by Resin Solutions. The polyurethane-type crosslinked binder is obtained by crosslinking the polyol polymer with at least one polyisocyanate-type crosslinking agent, which is generally used in a controlled quantity, i.e., in an amount such that the NCO / OH bridging ratio (Rp) is between 0.7 and 1.5. The OH groups are, as one might expect, provided by the polyol polymer.

[0037] The polyisocyanate type crosslinking agent is suitable for crosslinking such polyol polymers. In some embodiments, the crosslinking agent, known per se, is a polyisocyanate selected from methyl diisocyanate (MDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), dicyclohexyl methylene diisocyanate (MDCI), hexamethylene diisocyanate (HDI), the trimer of said hexamethylene diisocyanate (in particular marketed by Bayer under the trade name Desmodur® N 3300), biuret trihexane isocyanate (BTHI), 3,5,5-trimethyl-1,6-hexamethylene diisocyanate and mixtures thereof. Such crosslinking agents are conventionally used (i) in the necessary and sufficient quantity to ensure crosslinking of the polyol polymer (not excessive so as not to pollute the crosslinked product obtained) and (ii) in such quantity that the bridging ratio Rp is as defined above.

[0038] The reaction between the polyol polymer and the polyisocyanate-type crosslinking agent is carried out in the presence of a crosslinking catalyst, which is generally used in an amount between approximately 0.1 ppm and approximately 10 ppm, advantageously between approximately 0.1 ppm and approximately 1 ppm, this amount being expressed relative to the mass of the composite solid propellant. In some embodiments, the crosslinking catalyst is selected from triphenylbismuth, tin dibutyl dilaurate (DBTL), a bismuth carboxylate such as bismuth octoate or bismuth neodecanoate (as described in application FR-A-3 102 476), and mixtures thereof.

[0039] The composite solid propellant according to the invention comprises about 20.0% to about 90.0% by mass, such as for example about 60% by mass to about 75% by mass, of ammonium perchlorate (oxidizing charge).

[0040] In some embodiments, ammonium perchlorate comprises at least two fillers selected from class A fillers, class A' fillers, class B fillers, and class C fillers. Thus, ammonium perchlorate may be composed, for example, of mixtures of the following class fillers: A / C; A' / C; A / B / C; A' / B / C; A / A' / C; A / A' / B / C. In this disclosure, "class A filler" means a filler whose single-mode particle size distribution has a Dw value between approximately 100 µm and approximately 110 µm, a D50 value between approximately 170 µm and approximately 220 µm, and a D90 value between approximately 315 µm and approximately 340 µm.In this disclosure, "Class A' load" means a load with a single-mode particle size distribution exhibiting a Dw value between approximately 120 pm and approximately 270 pm, a D50 value between approximately 359 pm and approximately 465 pm, and a D90 value between approximately 599 pm and approximately 660 pm.

[0041] In this disclosure, "Class B load" means a load with a single-mode particle size distribution that has a Dw value between approximately 15 pm and approximately 20 pm, a D50 value between approximately 60 pm and approximately 120 pm, and a D90 value between approximately 185 pm and approximately 220 pm.

[0042] In this disclosure, "Class C load" means a load with a single-mode particle size distribution that has a Dw value between approximately 1.7 pm and approximately 3.6 pm, a D50 value between approximately 6 pm and approximately 12 pm, and a D90 value between approximately 20 pm and approximately 32 pm.

[0043] The values ​​Dw, D50, and D90 represent the diameter at which the cumulative volume percentage is 10%, 50%, or 90%, respectively. These particle size values ​​are derived from measurements performed using a laser particle size analyzer (Mastersizer™ 3000 type or equivalent), according to a procedure defined by standard NF 11-666. Regarding the A' charge, the D50 values ​​are derived from measurements performed by sieving, according to a procedure defined by standard MIL-STD-1234.

[0044] In some embodiments, ammonium perchlorate comprises a mixture of class A, B, and C fillers. Advantageously, such a mixture comprises, by mass, the following proportions of the different fillers:

[0045] - approximately 30 to approximately 90% by mass of class A charge;

[0046] - approximately 0 to approximately 35% by mass of class B charge;

[0047] - approximately 1 to approximately 35% by mass of class C charge.

[0048] In some embodiments, ammonium perchlorate comprises a mixture of class A', B, and C fillers. Advantageously, such a mixture comprises, by mass, the following proportions of the different fillers:

[0049] - approximately 30 to approximately 90% by mass of class A' charge;

[0050] - approximately 0 to approximately 35% by mass of class B charge;

[0051] - approximately 1 to approximately 35% by mass of class C charge.

[0052] In some embodiments, ammonium perchlorate comprises a mixture of class A, A' and C fillers. Advantageously, such a mixture comprises, by mass, the following proportions of the different fillers:

[0053] - approximately 0 to approximately 90% by mass of class A charge;

[0054] - approximately 0 to approximately 90% by mass of class A' charge; - approximately 10 to approximately 35% by mass of class C charge.

[0055] The composite solid propellant according to the invention also comprises 0% to about 25.0% by mass, such as about 15% by mass to about 20% by mass, of aluminium (reducing charge).

[0056] In some embodiments, the aluminum reducing charge has a D5O value less than or equal to 30 pm.

[0057] The composite solid propellant according to the invention also comprises 0% to about 5.0% by mass of a ballistic catalyst.

[0058] In some embodiments, the ballistic catalyst is chosen from among conventional ballistic catalysts, such as metal salts and oxides.

[0059] The composite solid propellant according to the invention also comprises 0.1% to about 20.0% by mass of at least one additive, said at least one additive comprising a functionalized organic compound as defined above.

[0060] In some embodiments, the composite solid propellant according to the invention comprises, in addition to the functionalized organic compound, at least one additive selected from plasticizers, anti-glare agents, adhesion agents between the binder and the oxidizing charge, antioxidants, and energy charges.

[0061] Examples of plasticizers include dioctyl azelate, diisooctyl sebacate, isodecyl pelargonate, polyisobutylene, dioctyl phthalate, and also energetic plasticizers such as triethylene glycol dinitrate.

[0062] Examples of anti-glare agents include compounds based on alkali metals, sodium (Na2SO4, etc.) and especially potassium (K2SO4, KNO3, K3AIF6, C4H5KO6, etc.), particularly potassium salts such as potassium cryolite (K3AIF6) or monobasic potassium tartrate (QHsKOe). Monobasic potassium tartrate can be in L- or D-enantiomer form or in racemic form. These specific potassium salts are commercially available in conventional particle sizes (powders with grains generally having a D50 between 1 and 300 µm).

[0063] Examples of adhesion agents between the binder and the oxidizing charge include bis(2-methylaziridinyl)-methylaminophosphine oxide (methyl BAPO) or triethylene pentamine acrylonitrile (TEPAN).

[0064] Examples of antioxidants include those from the rubber industry, such as ditertiobutylparacresol (DBC) or 2,2'-methylene-bis(4-methyl-6-tertio-butylphenol) (MBP5).

[0065] Examples of energetic charges include hexogen (RDX) and octogen (HMX). Without limiting the scope of this discussion, the composite solid propellants according to the invention can be prepared by a process comprising the following steps:

[0066] - the constitution of a homogeneous paste by: a) incorporation, with agitation, at a temperature between approximately 30°C and approximately 70°C, in a liquid polyol polymer, of the other constituent ingredients of the desired composite solid propellant with the exception of the crosslinking agent and the crosslinking catalyst, and b) agitation of the resulting mixture, under partial vacuum, at a temperature between approximately 30°C and approximately 70°C;

[0067] - the incorporation into said homogeneous paste formed, under partial vacuum and at a temperature between approximately 30°C and approximately 50°C, of ​​said crosslinking agent and approximately 0.1 ppm to approximately 10 ppm of said crosslinking catalyst, followed by stirring of the mixture formed;

[0068] - the pouring of said mixture constituted in at least one structure; and

[0069] - the heat treatment of said mixture constituted agitated poured into said at least one structure.

[0070] The partial vacuum mentioned is intended for degassing the medium above which it is applied. It is generally around 10 mm Hg. Incidentally, it is not necessarily of constant intensity.

[0071] The heat treatment (for crosslinking the polyol polymer) is generally carried out at a temperature between approximately 30°C and approximately 60°C (30°C < T < 60°C), for several days.

[0072] The composite solid propellants according to the invention advantageously have a burning rate of less than approximately 10 mm / s, for example, in the range of approximately 5 mm / s to approximately 9 mm / s, for example, approximately 5 mm / s to approximately 8 mm / s, or even approximately 5 mm / s to approximately 7 mm / s, over an operating pressure range of approximately 5 MPa to approximately 10 MPa. They are particularly suitable as propellant for rocket, satellite, or missile engines. Their use for this purpose is especially recommended. This is an integral part of the present invention and constitutes another aspect thereof.

[0073] In another aspect, the invention relates to a propellant charge containing at least one composite solid propellant as defined above. Such a charge is suitable not only for satellite or missile engines, but also for engines for space launch vehicles such as, for example, those of the Ariane rocket. The propellant charges contained in these engines have a mass ranging from a few hundred kilograms to several hundred tons.

[0074] In another aspect, the invention relates to a rocket, satellite, or missile engine comprising a propellant charge as defined above. The invention will be better understood with the aid of the illustrative examples below.

[0075] Example 1

[0076] A propellant was prepared from a "conventional" binder containing a polyisocyanate and a PBHT-type polyol polymer (R45HT™, marketed by Resin Solutions), and possibly a plasticizer (such as dioctyl azelate), according to the following protocol:

[0077] - incorporation into the binder, with agitation, at a temperature of 70°C, of ​​0.3% of a functionalized diamine organic compound (obtained by reaction of Priamine™, marketed by the company Cargill, with an acrylonitrile), and of the constituent ingredients of the composite solid propellant (mainly 68% ammonium perchlorate (mixture of class A, B and C fillers) and 20% aluminium) with the exception of the crosslinking agent and the crosslinking catalyst;

[0078] - agitation of the resulting mixture, under partial vacuum, at a temperature of 70°C for 60 minutes;

[0079] - incorporation into said homogeneous paste, under partial vacuum and at a temperature of 50°C, of ​​the crosslinking agents MDCI and 0.3 ppm of DBTL, followed by agitation of the mixture formed;

[0080] - the pouring of said mixture into a mold;

[0081] - heat treatment for 2 weeks at 50°C.

[0082] Comparative example 1

[0083] The protocol from Example 1 was repeated, but omitting the functionalized diamine organic compound. This comparative example was reproduced, under the same operating conditions, a few months apart.

[0084] Test 1

[0085] The combustion rate (Vc) of the propellants was measured according to example 1 and comparative example 1. The results are presented in figure 1 in which the upper curves represent the Vc of the propellant of comparative example 1, and the lower curve the Vc of the propellant of example 1. A significant decrease in the combustion rate (of at least -1.5 mm / s) of the propellant containing the functionalized organic compound is observed over the operating pressure range of 5 MPa to 10 MPa compared to the propellant not containing it.

[0086] Examples 2 and 3: The protocol of Example 1 was repeated, but using as propellant constituents either a mixture of 68% ammonium perchlorate (a mixture of class A' and C charge materials) and 18% aluminum (Example 2), or a mixture of 68% ammonium perchlorate (a mixture of class A and C charge materials) and 18% aluminum (Example 3). The proportion of functionalized diamine organic compound was increased to 0.6% for each example.

[0087] Comparative examples 2 and 3

[0088] The protocol of example 2 was repeated, but omitting the functionalized diamine organic compound. Comparative example 2 was reproduced, under the same operating conditions, a few months apart.

[0089] Test 2

[0090] The combustion rate (Vc) of the propellants thus prepared was measured. The results are presented in Figure 2, in which: the solid curves represent the Vc of the propellants of comparative example 3 (highest curve) and comparative examples 2 (intermediate curves); the dashed curves represent the Vc of the propellants of example 2 (lowest curve) and example 3 (highest curve).

[0091] Over the operating pressure range of 5 MPa to 10 MPa, there is a significant decrease in the combustion rate (of at least -1.5 mm / s with charge distribution A,C and of at least -1 mm / s with charge distribution A',C) of propellants containing a functionalized organic compound compared to propellants not containing one.

Claims

Demands 1. Solid composite propellant comprising: - 5.0% to 20.0% by mass of a crosslinked polyurethane type binder, which is the reaction product of a polyol polymer and a polyisocyanate type crosslinking agent, in the presence of a crosslinking catalyst; - 20.0% to 90.0% by mass of ammonium perchlorate; - 0% to 25.0% by mass of aluminium; - 0% to 5.0% by mass of a ballistic catalyst; - 0.1% to 20.0% by mass of at least one additive, said at least one additive comprising a functionalized organic compound comprising 10 to 65 carbon atoms, said functionalized organic compound having at least one secondary aziridine, epoxide or amine function.

2. Solid composite propellant according to claim 1, wherein the functionalized organic compound comprises from 10 to 25 carbon atoms, from 25 to 50 carbon atoms, or from 50 to 65 carbon atoms.

3. Solid composite propergol according to claim 1 or claim 2, wherein said functionalized organic compound contains at least one secondary amine function.

4. Solid composite propergol according to claim 3, wherein the functionalized organic compound comprises 30 to 50 carbon atoms and is obtained from a diamine of formula:

5. Solid composite propergol according to any one of claims 1 to 4, wherein the crosslinking agent is selected from methyl diisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethylene diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate trimer, biuret trihexane isocyanate, 3,5,5-trimethyl-1,6-hexamethylene diisocyanate and mixtures thereof.

6. Solid composite propergol according to any one of claims 1 to 5, wherein the crosslinking catalyst is selected from triphenylbismuth, tin dibutyl dilaurate, a bismuth carboxylate, and mixtures thereof.

7. Solid composite propellant according to any one of claims 1 to 6, wherein the ballistic catalyst, when present, is selected from metal salts and oxides.

8. Solid composite propergol according to any one of claims 1 to 7, wherein the polyol polymer is a hydroxytelechelic polybutadiene.

9. Composite solid propellant according to any one of claims 1 to 8, wherein the aluminum perchlorate comprises a mixture of class A, B and C fillers, where: - Class A loads have a single-mode particle size distribution with a Dio value between 100 pm and 110 pm, a D5o value between 170 pm and 220 pm and a D90 value between 315 pm and 340 pm; - Class B loads have a single-mode particle size distribution with a Dio value between 15 pm and 20 pm, a D50 value between 60 pm and 120 pm and a D90 value between 185 pm and 220 pm; - Class C loads have a single-mode particle size distribution with a Dio value between 1.7 pm and 3.6 pm, a D50 value between 6 pm and 12 pm and a D90 value between 20 pm and 32 pm.

10. Composite solid propellant according to any one of claims 1 to 8, wherein the aluminium perchlorate comprises a mixture of fillers of classes A', B and C, where: - Class A' loads have a single-mode particle size distribution with a Dio value between 120 pm and 270 pm, a D50 value between 359 pm and 465 pm and a D90 value between 599 pm and 660 pm; - Class B and C charges are as defined in claim 9.

11. Solid composite propellant according to any one of claims 1 to 8, wherein the aluminum perchlorate comprises a mixture of class A, A' and C fillers, wherein said class A, A' and C fillers are as defined in claims 9 and 10.

12. Use of a composite solid propellant as defined in any one of claims 1 to 11 as rocket, satellite or missile engine fuel.

13. Propellant load comprising at least one composite solid propellant as defined in any one of claims 1 to 11.

14. Rocket, satellite or missile engine comprising a propellant load according to claim 13.

Images