Hypergolic compositions and uses thereof

Abstract

The present invention relates to a composition comprising at least one amine selected from the group consisting of N,N,N',N'-tetramethylethylenediamine, N,N,N',N'- tetramethylpropylenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, N,N- dimethylethylenediamine, 4-methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof; at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof; and at least one carboxylic, nitrate, or sulfate salt of a transition metal; wherein the transition metal is completely dissolved in the composition. The invention also relates to hypergolic compositions and uses thereof.

Description

[0001] HYPERGOLIC COMPOSITIONS AND USES THEREOF

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of hypergolic amine liquid compositions comprising a completely dissolved transition metal salt, and uses thereof in the field of self-igniting propellants.

[0004] BACKGROUND

[0005] In spacecraft propulsion, a propulsion system is any device capable of accelerating or decelerating a spacecraft, not only to achieve orbit or returning from orbit and landing but also for the purposes of controlling position and manoeuvring the spacecraft while in orbit.

[0006] Traditionally, spacecraft use hypergolic propellants, which ignite spontaneously upon contact between the fuel and the oxidizer, offering the advantage of reliable ignition in the vacuum of space without the need for external ignition sources. In such propellant, a liquid fuel and a liquid oxidising agent react exothermically with one another thereby releasing gaseous combustion products for the generation of thrust. The energy density of a two-component system of fuel and oxidising agent is generally higher than that of one-component systems, with the result that a specific impulse in the range of 270 to 340 s can be achieved. Moreover, there is no need for heating, since the usable components are in liquid form over a broad temperature range.

[0007] The most widely used hypergolic propellant combinations consist of monomethylhydrazine (MMH) or unsymmetrical dimethylhydrazine (UDMH) as the fuel, and nitrogen tetroxide (NTO) as the oxidizer. These propellants have been favoured for their stability and ignition reliability under various space conditions, but present significant challenges such as toxicity and carcinogenicity which increase the complexity and cost of spacecraft operations. Moreover, hydrazine-based fuels are environmentally harmful and pose long-term storage challenges, given their corrosive nature.

[0008] Green propellants aim to reduce toxicity without compromising propulsion efficiency. A highly concentrated (85 to 99,99%) aqueous solution of hydrogen peroxide, known as high test hydrogen peroxide (HTP), has emerged as a viable green oxidizer, capable of achieving hypergolic ignition when combined with suitable fuels, especially those catalysed by transition metal salts. However, many of the proposed green fuel systems, such as those based on sodium borohydride, suffer from water instability, which complicates their use in real -world applications due to the risk of hydrolysis and the need for additives that may impair long-term storage stability.

[0009] Recent developments in green propulsion technologies have focused on creating stable and efficient hypergolic combinations with low environmental impact. For example, the introduction of polyamine / alkanolamine-based hypergolics (PAHyp) represented a significant step forward in reducing the catalyst content required for hypergolic ignition while improving fuel stability under atmospheric conditions. Mota, Fabio A.S., et al. (Combustion and Flame 270, 2024, 113744 and Combustion and Flame 267, 2024, 113567) describe a 14 ms ignition delay time (IDT) composition, consisting of a 1 :1 mixture of N,N,N',N' -tetramethylethylenediamine (TMEDA) and methylethanolamine, catalyzed by 2 wt% copper nitrate and a 6 ms IDT composition, consisting of a 1 :1 mixture of TMEDA and dimethylethanolamine, catalyzed by 1 wt% copper (II) acetate, when reacted with 94% hydrogen peroxide, respectively.

[0010] US patent application 2008 / 0127551 discloses hypergolic liquid fuel mixtures comprising TMEDA and DMAZ, although no information is provided on further ingredients to achieve ignition.

[0011] International patent application WO 03 / 004443 A2 discloses hypergolic compositions comprising TMEDA and methanol, catalyzed by copper (II) acetate.

[0012] These solutions offer potential benefits, however, challenges remain in achieving the same level of performance as traditional hypergolic propellants, particularly in terms of ignition delay times, combustion efficiency, specific impulse and long-term storage stability, while maintaining compatibility with existing propulsion systems. For instance, achieving complete solubilisation of metal salts, which are often used as catalysts or stabilizers, can be problematic in many solvent systems, leading to inconsistent performance and potential clogging of propulsion hardware. BRIEF DESCRIPTION OF THE INVENTION

[0013] The present invention aims to provide a hypergolic composition that at least partially overcomes the disadvantages of hypergolic systems known in the art.

[0014] In this way, a first aspect of the invention is directed at a composition comprising:

[0015] - at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, dimethyl-(2-azidoethyl)amine, and mixtures thereof;

[0016] - at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof; and

[0017] - at least one carboxylic, nitrate, or sulfate salt of a transition metal; wherein the transition metal is completely dissolved in the composition.

[0018] In a second aspect, the invention provides a hypergolic composition comprising the composition of the first aspect, further comprising an oxidant.

[0019] A third aspect of the invention provides a propulsion system, comprising any of the compositions of the first or second aspects.

[0020] A fourth aspect of the invention provides a method for the preparation of the composition according to the first aspect, comprising the steps of: a) providing a mixture of:

[0021] - at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, and mixtures thereof;

[0022] - at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethyl sulfoxide, and mixtures thereof; and

[0023] - at least one carboxylic, nitrate, or sulfate salt of a transition metal; b) stirring the mixture until complete dissolution of the transition salt; and c) optionally, adding dimethyl-(2-azidoethyl)amine In a fifth aspect, the invention is directed at the use of any of the compositions of the first or second aspects in a propulsion system.

[0024] The inventors have surprisingly found that while copper (II) acetate is insoluble in the organic solvents and amines of aspect 1, the combination of at least one of said solvents and at least one of said amines will act synergistically and fully dissolve copper (II) acetate.

[0025] Therefore, a sixth aspect of the invention provides the use of at least one amine selected from the group consisting of N,N,N’,N’ -tetramethylethylenediamine, N,N,N’,N’- tetramethylpropylenediamine, l,8-diazabicyclo[5.4.0]undec-7-ene, N,N- dimethylethylenediamine, 4-methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof, and at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof, to fully dissolve a carboxylic copper salt, preferably copper (II) acetate.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] All terms as used herein in this application, unless otherwise stated, shall be understood in their ordinary meaning as known in the art. Other more specific definitions for certain terms as used in the present application are as set forth below and are intended to apply uniformly throughout the specification and claims unless an otherwise expressly set out definition provides a broader definition.

[0028] Throughout the description and claims the word “comprises" and variations of the word, are not intended to exclude other technical features, additives, components or steps. Furthermore, the word “comprise” encompasses the cases of “consist of’ and “consists essentially of’. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention.

[0029] For the purposes of the invention, any ranges given include both the lower and the upper end-points of the range.

[0030] The term “wt.%”, similar in the present disclosure to “wt%” or “%w / w” is to be interpreted as the weight of a certain substance divided by the total weight of mixture multiplied by 100. For example, a composition comprising 1 wt.% of copper means that in 100 grams, the composition comprises 1 gram of copper. The skilled person will readily understand that when wt.% is indicated as a range, the sum of the ranges cannot be greater than 100%.

[0031] As mentioned above, a first aspect of the invention is directed at a composition comprising:

[0032] - at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof;

[0033] - at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethyl sulfoxide, and mixtures thereof; and

[0034] - at least one carboxylic, nitrate, or sulfate salt of a transition metal; wherein the transition metal is completely dissolved in the composition.

[0035] Amine

[0036] The composition of the first aspect of the invention comprises at least one amine selected from the group consisting of N,N,N’,N’ -tetramethylethylenediamine, N,N,N’,N’- tetramethylpropylenediamine, l,8-diazabicyclo[5.4.0]undec-7-ene, N,N- dimethylethylenediamine, 4-methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof.

[0037] In the present disclosure, N,N,N’,N’ -tetramethylethylenediamine is also known as TMEDA, N,N,N’,N’ -tetramethylpropylenediamine as TMPDA, 1,8- diazabicyclo[5.4.0]undec-7-ene as DBU, N,N-dimethylethylenediamine as DMEN and dimethyl-(2-azidoethyl)amine as DMAZ.

[0038] Preferably, said amine is selected from the group consisting of N,N,N’,N’- tetram ethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, N,N- dimethylethylenediamine, dimethyl-(2-azidoethyl)amine and mixtures thereof. More preferably, from the group consisting of N,N,N’,N’ -tetramethylethylenediamine, N,N- dimethylethylenediamine, dimethyl-(2-azidoethyl)amine and mixtures thereof. Even more preferably, the composition comprises a mixture of N,N,N’,N’- tetramethylethylenediamine and dimethyl-(2-azidoethyl)amine or a mixture of N,N- dimethylethylenediamine and dimethyl-(2-azidoethyl)amine.

[0039] In a particular embodiment, the composition of the first aspect of the invention comprises: an amine selected from the group consisting of N,N,N’,N’- tetram ethylethylenediamine, N,N,N’,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine and 4- methylmorpholine; and

[0040] - DM AZ.

[0041] In a particular embodiment, the composition of the first aspect of the invention comprises at least 5 wt.%, at least 20 wt.%, at least 30 wt.%, at least 40 wt.%, at least 50 wt.%, at least 60 wt.%, at least 65 wt.% and at least 70 wt.% of said at least one amine, the amounts by weight being expressed with respect to the total weight of the composition.

[0042] In another particular embodiment, the composition of the first aspect of the invention comprises no more than 95 wt.%, no more than 90 wt.%, no more than 89 wt.%, no more than 85 wt.%, and no more than 80 wt.% of said at least one amine, the amounts by weight being expressed with respect to the total weight of the composition.

[0043] In a particular embodiment, the composition of the first aspect of the invention comprises from 5 to 95 wt.% of said at least one amine, preferably from 30 to 95 wt.%, more preferably from 50 to 95 wt.%, even more preferably from 65 to 90 wt.%, the amounts by weight being expressed with respect to the total weight of the composition.

[0044] In a preferred embodiment, the composition of the first aspect of the invention comprises from 5 to 85 wt.% of TMEDA, preferably from 15 to 85 wt.%, more preferably from 20 to 80 wt.%, even more preferably from 30 to 70 wt.%, the amounts by weight being expressed with respect to the total weight of the composition.

[0045] In another preferred embodiment, the composition of the first aspect of the invention comprises from 5 to 75 wt.% of DMAZ, preferably from 9 to 70 wt.%, more preferably from 20 to 70 wt.%, even more preferably from 20 to 45 wt.%, the amounts by weight being expressed with respect to the total weight of the composition.

[0046] In a particular embodiment, the composition of the first aspect of the invention comprises: from 5 to 85 wt.% of an amine selected from the group consisting of N,N,N’,N’- tetram ethylethylenediamine, N,N,N’,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine and 4- methylmorpholine, preferably from 15 to 85 wt.%; and from 5 to 75 wt.% of DMAZ, preferably from 9 to 70 wt.%; the amounts by weight being expressed with respect to the total weight of the composition.

[0047] In a particular embodiment, the composition of the first aspect of the invention comprises: from 5 to 85 wt.% of TMEDA, preferably from 15 to 85 wt.%; and from 5 to 75 wt.% of DMAZ, preferably from 9 to 70 wt.%; the amounts by weight being expressed with respect to the total weight of the composition.

[0048] In a preferred embodiment, the composition of the first aspect of the invention comprises: from 20 to 80 wt.% of TMEDA, more preferably from 30 to 70 wt.%; and from 20 to 70 wt.% of DMAZ, more preferably from 20 to 45 wt.%; the amounts by weight being expressed with respect to the total weight of the composition.

[0049] In a particular embodiment, the composition of the invention comprises further amines, preferably selected from the group consisting of N,N’ dimethylpiperazine, N,N- diisopropylethylamine, pyrrolidine, pyridine, 3-(methylamino)propylamine, l-ethyl-3- methyl-imidazolium thiocyanate and 1 -methylimidazole. More preferably, the composition of the invention does not comprise an amine selected from the group consisting of N,N’ dimethylpiperazine, N,N-diisopropylethylamine, pyrrolidine, pyridine, 3-(methylamino)propylamine, l-ethyl-3-methyl-imidazolium thiocyanate and 1- methylimidazole. Even more preferably the composition does not comprise any further amine other than N,N,N’,N’ -tetramethylethylenediamine, N,N,N’,N’- tetramethylpropylenediamine, l,8-diazabicyclo[5.4.0]undec-7-ene, N,N- dimethylethylenediamine, 4-methylmorpholine or dimethyl-(2-azidoethyl)amine.

[0050] Organic solvent

[0051] The composition of the first aspect of the invention comprises at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof. Preferably, the organic solvent is acetonitrile. In another preferred embodiment, the organic solvent is a combination of acetonitrile and dimethylsulfoxide (DMSO).

[0052] In a particular embodiment, the organic solvent does not comprise a solvent selected from the group consisting of methanol, ethanol, toluene, ethyl acetate, and tetrahydrofuran, preferably the organic solvent does not comprise a solvent selected from the group consisting of alcohols, toluene, ethyl acetate, and tetrahydrofuran. Alcohols is to be interpreted as any organic molecule comprising at least one hydroxyl group in its structure.

[0053] In a particular embodiment, the composition of the first invention does not comprise 1- octyne, ethynylcyclopropane (ECP), or 1,4-dicyclopropylbuta-l, 3-diyne. Preferably, it does not comprise acetylenic compounds characterized by having up to 20 carbons.

[0054] In a particular embodiment, the composition of the first aspect of the invention comprises at least 5 wt.%, at least 10 wt.%, at least 11 wt.%, at least 15 wt.% and at least 20 wt.% of said at least one organic solvent, the amounts by weight being expressed with respect to the total weight of the composition.

[0055] In another particular embodiment, the composition of the first aspect of the invention comprises no more than 95 wt.%, no more than 80 wt.%, no more than 60 wt.%, no more than 55 wt.%, no more than 50 wt.%, no more than 40 wt.%, no more than 35 wt.%, no more than 30 wt.% and no more than 26 wt.% of said at least one organic solvent, the amounts by weight being expressed with respect to the total weight of the composition.

[0056] In a particular embodiment, the composition of the first aspect of the invention comprises from 5 to 95 wt.%, preferably from 5 to 50 wt.%, more preferably from 10 to 40 wt.%, even more preferably from 10 to 30 wt.%, of said at least one organic solvent, the amounts by weight being expressed with respect to the total weight of the composition. Preferably, said organic solvent is acetonitrile.

[0057] In another particular embodiment, the composition of the first aspect of the invention comprises from 5 to 95 wt.%, preferably from 5 to 70 wt.%, more preferably from 10 to 60 wt.%, more preferably from 20 to 60 wt.%, even more preferably from 45 to 60 wt.%, of said at least one organic solvent, the amounts by weight being expressed with respect to the total weight of the composition. Preferably, said organic solvent is a combination of acetonitrile and DMSO.

[0058] In yet another particular embodiment, the composition of the first aspect of the invention comprises:

[0059] - from 5 to 50 wt.% of acetonitrile, preferably from 20 to 50 wt.%; and

[0060] - from 4 to 10 wt.% of dimethylsulfoxide, preferably from 4 to 8 wt.%.

[0061] In a preferred embodiment, the composition of the first aspect of the invention comprises:

[0062] - from 40 to 50 wt.% of acetonitrile; and

[0063] - from 4 to 8 wt.% of dimethylsulfoxide.

[0064] Transition metal

[0065] The composition of the first aspect of the invention comprises at least one carboxylic, nitrate, or sulfate salt of a transition metal wherein the transition metal is completely dissolved in the composition. Preferably, the composition of the first aspect of the invention comprises at least one carboxylic, or sulfate salt of a transition metal wherein the transition metal is completely dissolved in the composition.

[0066] The expression “completely dissolved” means that the composition comprising said transition metal is homogeneous and does not develop a suspension or precipitate with time, nor does it develop any kind of separation in any proportion, during preparation and storage, including storage under operating conditions such as in a propellant tank of a spacecraft in orbit. More preferably, the transition metal is completely dissolved at normal temperature and pressure (20 °C and absolute pressure of 1 atm), even more preferably, the transition metal is completely dissolved at temperatures as low as 0 °C. A homogeneous composition is of particular interest for fuels in hypergolic mixtures, which reliably ignite upon contact with the oxidizer.

[0067] In a particular embodiment, the transition metal is completely dissolved in the composition and present in an amount of at least 0.1 wt.%, at least 0.2 wt.%, at least 0.4 wt.%, at least 0.5 wt.%, at least 0.6 wt.%, and at least 1.0 wt.%, the amounts by weight being expressed with respect to the total weight of the composition. Preferably, the transition metal is completely dissolved in the composition and present in an amount of at least 0.2 wt.%, more preferably at least 0.4 wt.% and even more preferably at least 0.5 wt.%, the amounts by weight being expressed with respect to the total weight of the composition

[0068] In another particular embodiment, the transition metal is completely dissolved in the composition and present in an amount of no more than 4.0 wt.%, no more than 3.0 wt.%, preferably no more than 2.0 wt.%, more preferably no more than 1.5 wt.%, and even more preferably no more than 1.0 wt.%.

[0069] In a particular embodiment, the composition of the first aspect comprises from 0.2 to 3.0 wt.% of said one carboxylic, nitrate, or sulfate salt of a transition metal, preferably from 0.4 to 1.5 wt.%, the amounts by weight being expressed with respect to the total weight of the composition. In a more preferred embodiment, the composition of the first aspect comprises from 0.5 to 1.1 wt.% of said one carboxylic, nitrate, or sulfate salt of a transition metal, most preferably from 0.5 to 0.7 wt.%, the amounts by weight being expressed with respect to the total weight of the composition. In yet another preferred embodiment, the composition of the first aspect comprises from 0.9 to 1.1 wt.% of said one carboxylic, nitrate, or sulfate salt of a transition metal, the amounts by weight being expressed with respect to the total weight of the composition.

[0070] In a preferred embodiment, the at least one carboxylic, nitrate, or sulfate salt of a transition metal is preferably selected from Cu(II), Mn(II), or Fe(II).

[0071] In a more preferred embodiment, the at least one carboxylic, nitrate, or sulfate salt of a transition metal is selected from the group consisting of Cu(OAc)2, Mn(OAc)2, Fe(OAc)2, CuSO4, CU(NOS)2 and mixtures thereof, even more preferably copper(II) acetate, of formula Cu(OAc)2.

[0072] In the context of the present invention, any reference to a carboxylic, nitrate, or sulfate salt of a transition metal is to be interpreted as the anhydrous salt or hydrates thereof.

[0073] In a particularly preferred embodiment, the composition of the first aspect comprises from 0.2 to 3.0 wt.% of copper(II) acetate, preferably from 0.4 to 1.5 wt.%, the amounts by weight being expressed with respect to the total weight of the composition. In a more preferred embodiment, the composition of the first aspect comprises from 0.5 to 1.1 wt.% of copper(II) acetate, most preferably from 0.5 to 0.7 wt.%, the amounts by weight being expressed with respect to the total weight of the composition. In yet another preferred embodiment, the composition of the first aspect comprises from 0.9 to 1.1 wt.% of copper(II) acetate, the amounts by weight being expressed with respect to the total weight of the composition.

[0074] In a particular embodiment, the composition of the first aspect of the invention does not comprise CuCh, preferably does not comprise a halogen salt of a transition metal. In another particular embodiment, said composition does not comprise copper phthalocyanine. More preferably, the only transition metal present in the composition of the first aspect of the invention is a carboxylic or sulfate salt of a transition metal.

[0075] In another particular embodiment, the composition of the first aspect of the invention does not comprise NaBFU and / or LiBFU. Preferably, the composition of the first aspect of the invention does not comprise a sodium and / or lithium alkali metal salt, even more preferably, the composition of the first aspect of the invention does not comprise an alkali metal salt. In a most preferred embodiment, the composition of the first aspect of the invention comprises copper(II) acetate and no other transition metal.

[0076] Further embodiments of the composition of the first aspect

[0077] In a particular embodiment, the composition of the first aspect of the invention comprises:

[0078] - at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof;

[0079] - at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof; and

[0080] - at least one carboxylic, nitrate, or sulfate salt of a transition metal; wherein the transition metal is completely dissolved in the composition.

[0081] In a preferred embodiment, the composition of the first aspect of the invention comprises:

[0082] - at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof;

[0083] - at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof; and

[0084] - copper(II) acetate; wherein copper(II) acetate is completely dissolved in the composition.

[0085] The inventors have surprisingly found that while copper(II) acetate is insoluble in the organic solvents and amines of the first aspect, the combination of at least one of said solvents and at least one of said amines will act synergistically and fully dissolve copper(II) acetate.

[0086] In a more preferred embodiment, the composition of the first aspect of the invention comprises:

[0087] - N,N,N’,N’ -tetramethylethylenediamine;

[0088] - acetonitrile; and

[0089] - copper(II) acetate; wherein the transition metal is completely dissolved in the composition.

[0090] In a most preferred embodiment, the composition of the first aspect of the invention comprises:

[0091] - N,N,N’,N’ -tetramethylethylenediamine;

[0092] - acetonitrile;

[0093] - copper(II) acetate; and

[0094] - dimethyl-(2-azidoethyl)amine; wherein the transition metal is completely dissolved in the composition.

[0095] In a particular embodiment, the composition of the first aspect of the invention comprises:

[0096] - from 5 to 85 wt.% of an amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, dimethyl-(2-azidoethyl)amine, and mixtures thereof, preferably from 15 to 85 wt.%; - from 5 to 95 wt.% of at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof, preferably from 5 to 50 wt.%; and

[0097] - from 0.2 to 3.0 wt.% of at least one carboxylic or sulfate salt of a transition metal, preferably 0.4 to 1.5 wt.%; wherein the transition metal is completely dissolved in the composition, the amounts by weight being expressed with respect to the total weight of the composition.

[0098] In a preferred embodiment, the composition of the first aspect of the invention comprises:

[0099] - from 5 to 85 wt.% of an amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, and mixtures thereof, preferably from 15 to 85 wt.%;

[0100] - from 5 to 95 wt.% of at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof, preferably from 5 to 50 wt.%; and

[0101] - from 0.2 to 3.0 wt.% of copper(II) acetate, preferably 0.4 to 1.5 wt.%; wherein copper(II) acetate is completely dissolved in the composition, the amounts by weight being expressed with respect to the total weight of the composition.

[0102] In a more preferred embodiment, the composition of the first aspect of the invention comprises:

[0103] - from 5 to 85 wt.% of N,N,N’,N’ -tetramethylethylenediamine, preferably from 15 to 85 wt.%;

[0104] - from 5 to 50 wt.% of acetonitrile, preferably from 10 to 40 wt.%; and

[0105] - from 0.2 to 3.0 wt.% of copper(II) acetate, preferably from 0.5 to 1.1 wt.%; the amounts by weight being expressed with respect to the total weight of the composition. Preferably, the composition further comprises from 5 to 75 wt.% of dimethyl-(2-azidoethyl)amine, preferably from 9 to 70 wt.%.

[0106] In an even more preferred embodiment, the composition of the first aspect of the invention comprises:

[0107] - from 15 to 85 wt.% of N,N,N’,N’ -tetramethylethylenediamine, preferably from 30 to 70 wt.%; - from 5 to 50 wt.% of acetonitrile, preferably from 10 to 30 wt.%; and

[0108] - from 0.4 to 1.5 wt.% of copper(II) acetate, preferably from 0.5 to 1.1 wt.%; wherein the transition metal is completely dissolved in the composition, the amounts by weight being expressed with respect to the total weight of the composition.

[0109] In a most preferred embodiment, the composition of the first aspect of the invention comprises:

[0110] - from 30 to 70 wt.% of N,N,N’,N’ -tetramethylethylenediamine;

[0111] - from 10 to 30 wt.% of acetonitrile;

[0112] - from 0.5 to 1.1 wt.% of copper(II) acetate; and

[0113] - from 20 to 45 wt.% of dimethyl-(2-azidoethyl)amine; wherein the transition metal is completely dissolved in the composition, the amounts by weight being expressed with respect to the total weight of the composition.

[0114] In another particular embodiment, the composition of the first aspect of the invention comprises:

[0115] - at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof;

[0116] - at least one organic solvent selected from the group consisting of acetonitrile, dimethylsulfoxide, and mixtures thereof; and

[0117] - at least one carboxylic, nitrate, or sulfate salt of a transition metal; wherein the transition metal is completely dissolved in the composition.

[0118] In a more preferred embodiment, the composition of the first aspect of the invention comprises:

[0119] - N,N,N’,N’ -tetramethylethylenediamine;

[0120] - acetonitrile and DMSO; and

[0121] - copper(II) acetate; wherein the transition metal is completely dissolved in the composition.

[0122] In a preferred embodiment, the composition of the first aspect of the invention comprises: - from 5 to 85 wt.% of N,N,N’,N’ -tetramethylethylenediamine, preferably from 15 to 85 wt.%;

[0123] - from 5 to 60 wt.% of acetonitrile, preferably from 10 to 60 wt.%; and

[0124] - from 0.2 to 3.0 wt.% of copper(II) acetate, preferably from 0.5 to 1.1 wt.%; the amounts by weight being expressed with respect to the total weight of the composition. Preferably, the composition further comprises from 4 to 10 wt.% of dimethylsulfoxide, preferably from 4 to 8 wt.%.

[0125] In a particular embodiment, the composition of the first aspect of the invention comprises:

[0126] - from 5 to 85 wt.% of N,N,N’,N’ -tetramethylethylenediamine, preferably from 45 to 70 wt.%;

[0127] - from 5 to 50 wt.% of acetonitrile, preferably from 20 to 50 wt.%;

[0128] - from 0.2 to 3.0 wt.% of copper(II) acetate, preferably from 0.5 to 1.1 wt.%, more preferably from 0.8 to 1.1 wt.%; and

[0129] - from 4 to 10 wt.% of dimethylsulfoxide, preferably from 4 to 8 wt.%; the amounts by weight being expressed with respect to the total weight of the composition.

[0130] In a preferred embodiment, the composition of the first aspect, preferably characterized by being a fuel composition, comprises:

[0131] - from 45 to 55 wt.% of N,N,N’,N’ -tetramethylethylenediamine;

[0132] - from 30 to 50 wt.% of acetonitrile;

[0133] - from 0.5 to 1.1 wt.% of copper(II) acetate, preferably 0.8 to 1.1 wt.%; and

[0134] - from 4 to 8 wt.% of dimethylsulfoxide; the amounts by weight being expressed with respect to the total weight of the composition.

[0135] In a particular embodiment, the composition of the first aspect of the invention does not comprise ionic liquids.

[0136] Hypergolic composition

[0137] The inventors have surprisingly found that the composition of the first aspect of the invention is hypergolic when combined with a suitable oxidizer, and thus can be used as fuel in a non-toxic, stable, two-component hypergolic composition. In this context, a stable composition is to be understood as a composition that shows no signs of precipitation when stored at room temperature for at least 4 months, preferably at least 6 months, more preferably at least 12 months.

[0138] Therefore, in a particular embodiment, the composition of the first aspect of the invention is a fuel composition. Preferably, it is a fuel suitable for use in hypergolic compositions, more preferably for propulsion systems.

[0139] In a particular embodiment, the fuel is liquid at an operational temperature of 0 to 40 ° C, preferably 5 to 35 °C. In another particular embodiment, the fuel is liquid at an operational pressure of 1 to 40 bar, preferably 5 to 25 bar.

[0140] In a second aspect, the invention provides a hypergolic composition comprising the composition of the first aspect and any of its embodiments herein described, further comprising an oxidant.

[0141] In the present description, unless explicitly mentioned otherwise, “hypergolic composition” is to be understood as a stable two-component composition comprising a fuel (component 1) and an oxidant (component 2), separated from each other, and before ignition. The fuel, as described above, will ignite spontaneously upon contact with the oxidant, preferably under 30 ms. Without wishing to be bound by a particular theory, the inventors consider that the transition metal will catalyse the decomposition of the oxidant into oxygen and heat. A suitable test is to contact an oxidant and a fuel and observe if upon contact a flame is released without the need of an external source of ignition.

[0142] The term “oxidant” is readily understood by the skilled person as synonym to “oxidizing agent”, “oxidizer”, “electron recipient” or “electron acceptor”.

[0143] In a particular embodiment, the oxidant is liquid at an operational temperature of 0 to 40 °C, preferably 5 to 35 °C. In another particular embodiment, the oxidant is liquid at an operational pressure of 1 to 40 bar, preferably 5 to 25 bar.

[0144] In a preferred embodiment, both the fuel and the oxidant are liquid at an operational temperature of 0 to 40 °C, and operational pressure of 1 to 40 bar, preferably 5 to 25 bar. In a more preferred embodiment, the hypergolic composition does not comprise any solids, or any gases, even more preferred, the hypergolic composition is free of both solids or gases in its composition, i.e., it is a purely liquid composition.

[0145] In a particular embodiment, the oxidant is selected from the group consisting of hydrogen peroxide, nitrogen tetroxide, nitric acid, nitrous oxide, oxygen, and combinations thereof, preferably hydrogen peroxide, more preferably high test peroxide (HTP).

[0146] In the context of the present invention, HTP refers to high test peroxide, which is a highly concentrated (85 to 99,99%) solution of hydrogen peroxide with the remainder consisting predominantly of water.

[0147] In a particular embodiment, high test peroxide means hydrogen peroxide at a concentration of at least 85%, at least 90%, preferably at least 92%, more preferably at least 95%, even more preferably at least 97%, and most preferably at least 98% hydrogen peroxide, the remainder consisting predominantly of water. In another particular embodiment, the HTP is at a concentration of no more than 99%, preferably no more than 98%.

[0148] Without wishing to be bound by a particular theory, the inventors postulate that when acetonitrile is preferably used as organic solvent, it increases the miscibility of the fuel composition with HTP, an important characteristic for the hypergolicity. In a particular embodiment, the fuel is fully miscible with the oxidant, preferably HTP.

[0149] In a preferred embodiment, the hypergolic composition of the second aspect is characterized by being a two-component propellant system comprising:

[0150] - a fuel composition comprising:

[0151] - from 30 to 70 wt.% of N,N,N’,N’ -tetramethylethylenediamine;

[0152] - from 10 to 30 wt.% of acetonitrile;

[0153] - from 0.5 to 1.1 wt.% of copper(II) acetate; and

[0154] - from 20 to 45 wt.% of dimethyl-(2-azidoethyl)amine; or

[0155] - a fuel composition comprising:

[0156] - from 45 to 55 wt.% of N,N,N’,N’ -tetramethylethylenediamine; - from 30 to 50 wt.% of acetonitrile;

[0157] - from 0.5 to 1.1 wt.% of copper(II) acetate, preferably from 0.8 to 1.1 wt.% of copper(II) acetate; and

[0158] - from 4 to 8 wt.% of dimethylsulfoxide; and

[0159] - optionally, from 20 to 45 wt.% of dimethyl-(2-azidoethyl)amine; the amounts by weight being expressed with respect to the total weight of the fuel composition; and

[0160] - an oxidant selected from an 85% to 99% solution of hydrogen peroxide with the remainder consisting predominantly of water.

[0161] The skilled person will readily understand that in the hypergolic composition of the invention, any reference to wt.% in the fuel composition is expressed with respect to the total weight of the fuel composition.

[0162] In a particular embodiment, the hypergolic composition of the invention does not comprise a gelling agent.

[0163] In a particular embodiment, the hypergolic composition of the invention exhibits a specific impulse (Isp) in the range of 270 to 340 seconds.

[0164] In another particular embodiment, the hypergolic composition of the invention exhibits an ignition delay time (IDT) less than 30 ms, preferably less than 15 ms, more preferably less than 10 ms, even more preferably less than 8 ms, and most preferably less than 7 ms.

[0165] In another particular embodiment, the hypergolic composition of the invention exhibits a dynamic viscosity not greater than 3.00 mPa s, preferably not greater than 2.0 mPa s, more preferably not greater than 1.00 mPa s, even more preferably not greater than 0.80 mPa s, and most preferably not greater than 0.70 mPa s.

[0166] Propulsion system

[0167] A third aspect of the invention provides a propulsion system comprising any of the compositions of the first or second aspects as described herein. In the present invention, the term “propulsion system” is to be understood as any primary or secondary propulsion system suitable for being powered by exothermic chemical reactions of the compositions of the first or second aspects. An example of such “propulsion system” within the context of the present invention is a rocket engine, a thruster or an orbital propulsion device.

[0168] Thus, in a particular embodiment, the propulsion system of the third aspect of the invention is a rocket engine, thruster, or orbital propulsion device.

[0169] The propulsion system of the third aspect comprises a composition according to any of the first or second aspects that, upon ignition, serves as propellant thus generating thrust. Preferably the propulsion system propels a spacecraft. Thus, in a particular embodiment, said propulsion system, preferably a rocket engine, thruster, or orbital propulsion device, is a propulsion system of a spacecraft. In this context, a thruster includes reaction control thrusters.

[0170] The compositions of the present invention are particularly useful for in-orbit, from orbit and to-orbit propulsion.

[0171] In the present invention, the terms “in-orbit”, “from orbit”, and “to-orbit” propulsion are to be interpreted as encompassing at least one of the following: orbital station-keeping, attitude control, Delta-v manoeuvring, orbital manoeuvring, acceleration, deceleration, space-launch, atmospheric entry and landing.

[0172] In this way, in a particular embodiment, the propulsion system comprising any of the compositions of the first or second aspects is a propulsion system for in-orbit, from orbit and to-orbit propulsion.

[0173] In a preferred embodiment, the propulsion system comprises a fuel according to the first aspect in a first reservoir, and an oxidant as disclosed above in a second reservoir. The reservoirs are separate from one another but disposed such that the fuel can be put in contact with the oxidant, so that ignition only occurs once both fuel and oxidant are contacted. Once ignition takes place, gases are produced which provide the thrust.

[0174] Non-limiting examples of “reservoir” include tanks, such as fuel or propellant tanks, containers and storage vessels. Method for the preparation of the composition of the first aspect of the invention

[0175] A fourth aspect of the invention provides a method for the preparation of the composition according to the first aspect, comprising the steps of: a) providing a mixture of:

[0176] - at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine and mixtures thereof;

[0177] - at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethyl sulfoxide, and mixtures thereof; and

[0178] - at least one carboxylic, nitrate or sulfate salt of a transition metal; b) stirring the mixture until complete dissolution of the salt of the transition metal; and c) optionally, adding dimethyl-(2-azidoethyl)amine to the solution of step (b), and stirring.

[0179] The skilled person will readily understand the conditions required to prepare the composition of the first aspect, including the duration, temperature, and order of addition of each step. For example, it is clear to the skilled person that the duration of stirring will depend on the size of the reaction vessel and on the amounts used.

[0180] In a particular embodiment, step (a) comprises the addition of said amine into said organic solvent, preferably while stirring. In this step, said salt of a transition metal is preferably added after said amine.

[0181] In a preferred embodiment, the method is conducted without heating, i.e., at room temperature.

[0182] Step (b) requires complete dissolution of the salt of the transition metal. In a particular embodiment, the mixture is stirred for at least 5, at least 10, at least 15, at least 30 and at least 60 minutes. Preferably, the mixture is stirred for at least 10 minutes. In another particular embodiment, the mixture is stirred for 5 to 120, 5 to 60, 5 to 45, 5 to 30, preferably 10 to 20 minutes. In the optional step (c), dimethyl-(2-azidoethyl)amine is added to the solution of step (b) and the mixture is stirred. In a particular embodiment, the mixture is stirred for at least 5, at least 10, at least 30, at least 60 and at least 120 minutes. Preferably, the mixture is stirred for at least 60 minutes. In another particular embodiment, the mixture is stirred for 5 to 180, 10 to 180, 30 to 180, 60 to 180, preferably 120 minutes.

[0183] In a preferred embodiment, step (c) is conducted and the product is a liquid fuel, as disclosed above.

[0184] Uses

[0185] The present invention aims to provide fuels and hypergolic compositions. Thus, in a fifth aspect, the invention is directed at the use of any of the compositions of the first or second aspects in a propulsion system.

[0186] In a particular embodiment of the fifth aspect, said use comprises in-orbit, from orbit and to-orbit propulsion

[0187] The inventors have surprisingly found that while copper(II) acetate is insoluble in the organic solvents and amines of the first aspect, the combination of at least one of said solvents and at least one of said amines will act synergistically and fully dissolve copper(II) acetate.

[0188] Therefore, a sixth aspect of the invention provides the use of at least one amine selected from the group consisting of N,N,N’,N’ -tetramethylethylenediamine, N,N,N’,N’- tetramethylpropylenediamine, l,8-diazabicyclo[5.4.0]undec-7-ene, N,N- dimethylethylenediamine, 4-methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof, and at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof, to fully dissolve a carboxylic copper salt, preferably copper(II) acetate.

[0189] In a preferred embodiment of the sixth aspect of the invention, the at least one amine is selected from the group consisting of N,N,N’,N’ -tetramethylethylenediamine, N,N,N’,N’ -tetramethylpropylenediamine, l,8-diazabicyclo[5.4.0]undec-7-ene, N,N- dimethylethylenediamine, 4-methylmorpholine and mixtures thereof, more preferably N,N,N ’ ,N’ -tetramethyl ethyl enedi amine . In another preferred embodiment of the sixth aspect of the invention, the at least one organic solvent is selected from the group consisting of acetonitrile, dimethyl isosorbide, dimethylsulfoxide, and mixtures thereof, more preferably acetonitrile. In another preferred embodiment, the solvent is acetonitrile and dimethylsulfoxide.

[0190] In a particular embodiment, the use of the sixth aspect is to fully dissolve a carboxylic copper salt at a temperature ranging from 0 to 82 °C, from 10 to 80 °C, from 10 to 70 °C, from 15 to 70 °C, from 15 to 60 °C, preferably from 15 to 50 °C.

[0191] Said carboxylic copper salt is preferably at a concentration of from 0.2 to 4.5 wt.%, 0.2 to 3.0 wt.%, preferably from 0.4 to 1.5 wt.%, the amounts by weight being expressed with respect to the total weight of the composition comprising the at least one amine, the at least one organic solvent and the copper salt. In a more preferred embodiment, said carboxylic copper salt is preferably at a concentration of from 0.5 to 1.1 wt.%, most preferably from 0.5 to 0.7 wt.%, the amounts by weight being expressed with respect to the total weight of the composition comprising the at least one amine, the at least one organic solvent and the copper salt. In yet another preferred embodiment, said carboxylic copper salt is preferably at a concentration of from 0.9 to 1.1 wt.%, the amounts by weight being expressed with respect to the total weight of the composition comprising the at least one amine, the at least one organic solvent, and the copper salt.

[0192] In a most preferred embodiment, the sixth aspect of the invention provides the use of N,N,N’,N’ -tetramethylethylenediamine and acetonitrile to fully dissolve copper(II) acetate, preferably wherein copper(II) acetate is in an amount of from 0.2 to 3.0 wt.%, the amounts by weight being expressed with respect to the sum of the weights of N,N,N’,N’- tetramethylethylenediamine, acetonitrile and copper(II) acetate.

[0193] EXAMPLES

[0194] The following examples are intended to illustrate but not to limit the disclosed embodiments.

[0195] Example 1. Preparation of a fuel according to the invention

[0196] 19 g of acetonitrile was weighed in a 250 mL screw-capped flask equipped with a magnetic stirrer. Then, 63.2 g of TMEDA was added. After, 0.9 g of copper (II) acetate monohydrate was added and the mixture stirred until complete dissolution of the salt (ca. 15 min). The mixture turned from a heterogenic turquoise mixture to a dark blue homogeneous solution. Finally, 66.8 g of DMAZ was added while stirring. After the addition was complete, the bottle was flushed with N2, closed with a cap and the mixture stirred for 2 h to afford a blueish green solution.

[0197] The stirring was stopped, and the contents were poured into a 250 mL oven-dried amberglass flask, the air was replaced by N2, and the bottle was sealed with a screw cap, then parafilm, and finally stored at room temperature protected from light.

[0198] Example 2, Stability tests

[0199] The fuel of Example 1 was submitted to a stability test, based on the Manual of Tests and Criteria, which, according to the provisions of the "United Nations Recommendations on the Transport of Dangerous Goods, Model Regulations", as well as of chemicals presenting physical hazards according to the "Globally Harmonized System of Classification and Labelling of Chemicals" (GHS), contains criteria, test methods and procedures to be used for classification of dangerous goods.

[0200] The test was Test 3 (c): Thermal stability test at 75 °C.

[0201] In detail, approximately 1g of the selected fuel was placed in a vial and sealed with a screw cap (no purge was performed, so the samples were closed at ambient atmosphere). A picture of the sample was taken as reference. Then, the vial was carefully placed in a pre-heated oven at 75°C and it was left at constant temperature for 32h. The sample was monitored constantly, especially during the first 8h, seeking for signs of violent reactivity (bubbling, ignition, etc.).

[0202] After, the sample was visually inspected and compared with the initial state. The colour of the sample did not vary significantly. The sample was also subjected to a drop-test (Example 4) to evaluate the ignition delay time (IDT) and no significant difference was observed with the untreated sample.

[0203] Example 3, Solubility tests

[0204] Copper (II) acetate is very soluble in water, but was shown to be poorly soluble in pure TMEDA (0.07 wt.%) or pure acetonitrile (0.8 wt.%), even when stirring at 50°C. However, stable compositions containing completely dissolved up to 2 wt.% Cu(OAc)2 were prepared by mixing TMEDA and acetonitrile. Stable compositions containing completely dissolved up to 4.5 wt.% Cu(OAc)2 were also prepared by mixing TMEDA and acetonitrile.

[0205] Example 4, Drop test (ignition test)

[0206] A fuel "pool" was prepared by placing 60 microliters of the fuel in a watch glass with a pipette. Then, a micropipette was loaded with 20 microliters of HTP (>95%) and placed approximately 30 cm above the fuel pool. Then, the HTP was dropped as a single drop into the fuel pool. The experiment was recorded with a camera at 240 fps, and the IDT calculated by measuring the time from the frame where the HTP drop collides with the fuel pool until the first flame kernel is observed. The experiment was carried out in a ventilated area to avoid accumulation of combustion vapours. The experiments showed that these mixtures were hypergolic with HTP, yielding IDTs lower than 30 ms, down to 6 ms.

[0207] Replacing acetonitrile with dimethyl isosorbide (DMI) also produced completely dissolved hypergolic compositions, with IDTs lower than 30 ms.

[0208] Replacing TMEDA with N,N-dimethylethylenediamine also produced completely dissolved hypergolic compositions.

[0209] Replacing TMEDA with any of N,N’ -dimethylpiperazine, l-methyl-4-piperidone, MEA, DMEA, DBU, NMM, DMPA, Pyr, TMPDA, DIPEA, N-methylpiperidine, N- methylpyrrolidine, 1 -methylimidazole either resulted in a suspension / precipitate, or in mixtures that were not hypergolic (or ignited at IDTs greater than 40 ms).

[0210] Example 5, Hypergolic compositions according to the invention

[0211] Stable compositions comprising dimethyl-(2-azidoethyl)amine (DMAZ), TMEDA, acetonitrile, further comprising between 0.3 and 1.5 wt.% of copper (II) acetate as catalyst were prepared.

[0212] For example, formulations comprising from 0.6 to 1 wt.% Cu (II) acetate, and acetonitrile:DMAZ:TMEDA ratios comprised between 10:22:68 and 26:41 :33 remained stable as liquid homogeneous solutions. These formulations were hypergolic, showing IDTs as low as 6.6 ms. However, replacing acetonitrile with DMSO, acetone, y-valerolactone or toluene resulted into a heterogeneous mixture.

[0213] Example 6, Comparative compositions

[0214] Ignition tests were conducted following the procedure described in example 4, for comparative samples comprising DMAZ and TMEDA (composition shown in the table below), as taught in prior art document US2008 / 127551A1.

[0215] Sample TMEDA (g) DMAZ (g) Result from droptest*

[0216] A 0.00 1.00 No reactivity

[0217] B 0.25 0.75 No reactivity

[0218] C 0.50 0.50 No reactivity

[0219] D 0.75 0.25 Fumes but no ignition

[0220] E 1.00 0.00 Fumes but no ignition

[0221] * Droptest consists of letting a drop of HTP collide to a pool of fuel in a watch glass.

[0222] This experiment shows that a combination of TMEDA and DMAZ is not hypergolic when put in contact with HTP.

[0223] Following the procedure described in example 4, further ignition tests were conducted for comparative samples comprising copper(II) acetate in TMEDA and methanol or octyne, as taught in WO 03 / 004443 A2.

[0224] First, copper (II) acetate solubility in TMEDA was tested and found to be close to 0.07% in weight or 0.55 mg / mL. The solution showed high reactivity with hydrogen peroxide, but with an ignition time of >1500 ms and inconsistent results. For this reason, it is not considered hypergolic (IDT <30 ms).

[0225] The following table shows the results for compositions comprising TMEDA, copper acetate, and 1 -octyne.

[0226] Sample TMEDA (0.07% Cu) (g) Octyne (g) Result from droptest*

[0227] F 0.305 0.605 Mild reactivity

[0228] G 0.409 0.552 Mild reactivity

[0229] H 0.490 0.417 Mild reactivity

[0230] * Droptest consists of letting a drop of HTP collide to a pool of fuel in a watch glass. Mild reactivity means bubbling and / or fuming but no ignition. These tests show that compositions comprising 0.07% copper(II) acetate in TMEDA and Octyne are not hypergolic.

[0231] The following table shows the results for compositions comprising TMEDA, copper(II) acetate, and methanol.

[0232] Sample TMEDA (0.07% Cu) (g) MeOH (g) Result from droptest*

[0233] I 0.319 0.591 Mild reactivity

[0234] J 0.396 0.536 Mild reactivity

[0235] K 0.516 0.400 Mild reactivity * Droptest consists of letting a drop of HTP collide to a pool of fuel in a watch glass. Mild reactivity means bubbling and / or fuming but no ignition.

Claims

CLAIMS1. A composition comprising:- at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof;- at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof; and- at least one carboxylic, nitrate, or sulfate salt of a transition metal; wherein the transition metal is completely dissolved in the composition.

2. The composition according to claim 1, comprising:- from 5 to 85 wt.% of N,N,N’,N’ -tetramethylethylenediamine, preferably from 15 to 85 wt.%;- from 5 to 50 wt.% of acetonitrile, preferably from 10 to 40 wt.%; and- from 0.2 to 3.0 wt.% of copper(II) acetate, preferably from 0.5 to 1.1 wt.%; the amounts by weight being expressed with respect to the total weight of the composition.

3. The composition according to any one of claims 1 or 2, comprising an amine selected from the group consisting of N,N,N’,N’- tetram ethylethylenediamine, N,N,N’,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine and 4- methylmorpholine; and dimethyl-(2-azidoethyl)amine.

4. The composition according to any one of claims 1 to 3, comprising:- from 5 to 85 wt.% of N,N,N’,N’ -tetramethylethylenediamine, preferably from 15 to 85 wt.%;- from 5 to 50 wt.% of acetonitrile, preferably from 10 to 40 wt.%; and- from 0.2 to 3.0 wt.% of copper(II) acetate, preferably from 0.5 to 1.1 wt.%; and- from 5 to 75 wt.% of dimethyl-(2-azidoethyl)amine, preferably from 9 to 70 wt.%; the amounts by weight being expressed with respect to the total weight of the composition.

5. The composition according to any one of claims 1 to 4, characterized by being a fuel composition comprising:- from 30 to 70 wt.% of N,N,N’,N’ -tetramethylethylenediamine;- from 10 to 30 wt.% of acetonitrile;- from 0.5 to 1.1 wt.% of copper(II) acetate; and- from 20 to 45 wt.% of dimethyl-(2-azidoethyl)amine; the amounts by weight being expressed with respect to the total weight of the composition.

6. The composition according to any one of claims 1 to 5, comprising a combination of acetonitrile and dimethylsulfoxide.

7. The composition according to any one of claims 1 or 2, comprising:- from 5 to 85 wt.% of N,N,N’,N’ -tetramethylethylenediamine, preferably from 45 to 70 wt.%;- from 5 to 50 wt.% of acetonitrile, preferably from 20 to 50 wt.%; and- from 0.2 to 3.0 wt.% of copper(II) acetate, preferably from 0.8 to 1.1 wt.%; and- from 4 to 10 wt.% of dimethylsulfoxide, preferably from 4 to 8 wt.%; the amounts by weight being expressed with respect to the total weight of the composition.

8. The composition according to claim 7, characterized by being a fuel composition comprising: from 45 to 55 wt.% of N,N,N’,N’ -tetramethylethylenediamine; from 30 to 50 wt.% of acetonitrile;from 0.8 to 1.1 wt.% of copper(II) acetate; and from 4 to 8 wt.% of dimethylsulfoxide; the amounts by weight being expressed with respect to the total weight of the composition.

9. A hypergolic composition comprising the composition of any one of claims 1 to 8, further comprising an oxidant.

10. The hypergolic composition according to claim 9, wherein the oxidant is selected from the group consisting of hydrogen peroxide, nitrogen tetroxide, nitric acid, nitrous oxide, oxygen, and combinations thereof, preferably hydrogen peroxide, more preferably high test peroxide.

11. The hypergolic composition according to any one of claims 9 or 10, characterized by being a two-component propellant system comprising:- a fuel composition comprising:- from 30 to 70 wt.% of N,N,N’,N’ -tetramethylethylenediamine;- from 10 to 30 wt.% of acetonitrile;- from 0.5 to 1.1 wt.% of copper(II) acetate; and- from 20 to 45 wt.% of dimethyl-(2-azidoethyl)amine; or- a fuel composition comprising:- from 45 to 55 wt.% of N,N,N’,N’ -tetramethylethylenediamine;- from 30 to 50 wt.% of acetonitrile;- from 0.8 to 1.1 wt.% of copper(II) acetate;- from 4 to 8 wt.% of dimethylsulfoxide; and- optionally, from 20 to 45 wt.% of dimethyl-(2-azidoethyl)amine; the amounts by weight being expressed with respect to the total weight of the fuel composition;and- an oxidant selected from an 85% to 99,99% solution of hydrogen peroxide with the remainder consisting predominantly of water.

12. A propulsion system, comprising a composition according to any one of claims 1 to 11.

13. The propulsion system of claim 12, characterised by being a rocket engine, thruster or orbital propulsion device.

14. A method for the preparation of the composition according to any one of claims 1 to 8, comprising the steps of: a) providing a mixture of:- at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4- methylmorpholine, and mixtures thereof;- at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide, and mixtures thereof; and- at least one carboxylic, nitrate, or sulfate salt of a transition metal; b) stirring the mixture until complete dissolution of the transition salt; and c) optionally, adding dimethyl-(2-azidoethyl)amine to the solution of step (b), and stirring.

15. Use of the composition according to any one of claims 1 to 11 in a propulsion system.

16. Use of at least one amine selected from the group consisting of N,N,N’,N’- tetramethylethylenediamine, N,N,N’ ,N’ -tetramethylpropylenediamine, 1,8- diazabicyclo[5.4.0]undec-7-ene, N,N-dimethylethylenediamine, 4-methylmorpholine, dimethyl-(2-azidoethyl)amine and mixtures thereof, and at least one organic solvent selected from the group consisting of acetonitrile, dimethyl isosorbide, acetone, dimethylsulfoxide and mixtures thereof, to fully dissolve a carboxylic copper salt, preferably copper(II) acetate.

17. The use according to claim 16, wherein said amine is N,N,N’,N’- tetramethylethylenediamine, said organic solvent is acetonitrile, and said carboxylic copper salt is copper(II) acetate.

18. The use according to any one of claims 16 or 17, wherein copper(II) acetate is in an amount of from 0.2 to 4.5 wt.%, preferably from 0.2 to 3.0 wt.%, the amounts by weight being expressed with respect to the sum of the weights of N,N,N’,N’- tetramethylethylenediamine, acetonitrile and copper(II) acetate.