Fuel for spacecraft and / or missiles

Abstract

The invention relates to a fuel consisting of nitromethane for spacecraft and / or missiles, wherein the fuel contains at least one additive in the form of an inhibitor that reduces the impact sensitivity, wherein the inhibitor is dimethyl sulphoxide, or wherein the inhibitor is at least one of n-butanol compounds or nitroethane or an ionic liquid, wherein the inhibitor is a phlegmatiser and reduces the impact sensitivity.

Description

[0001] Description

[0002] title

[0003] FUEL FOR SPACECRAFT AND / OR MISSILE

[0004] State of the art

[0005] The invention relates to a fuel for spacecraft and / or missiles.

[0006] Liquid Monergol propellants are often used for the orbit and attitude control of satellites and missiles. Since only one tank and a single set of propellant delivery components are required, this allows for very simple and inexpensive systems.

[0007] To date, hydrazine has typically been used as the fuel in such systems. The decomposition of this substance, which is necessary for ignition and operation of such an engine, can be easily accomplished using indium-platinum-based catalysts. The decomposition gases, i.e., the reactive support mass produced during decomposition, have a relatively low temperature of approximately 800 K, which allows for simple design without the use of expensive high-temperature materials. Nevertheless, a relatively high propulsion power can be achieved: the theoretical specific impulse is 1979 m / s. However, the disadvantage of using hydrazine is the high cost of handling this substance. This is due to its high toxicity and carcinogenicity. To meet this challenge, a number of alternative fuels have been researched, developed, and tested.One approach to creating such so-called "green propellants" involves preparing solutions of solid explosive oxidizers such as hydroxyl ammonium nitrate (HAN) and ammonium dinitramide (ADN) in water and then adding a fuel component, such as methanol or ammonia, to create a premixed, reactive mixture or explosive substance that is, however, sufficiently insensitive to be used as a propellant. Such propellants typically have a higher volume and mass specific impulse than hydrazine.

[0008] However, HAN and ADN-based propellants have high production costs. In addition, these propellants also have significantly higher burnup temperatures than hydrazine, which has so far presented a challenge for the construction materials of such engines. Furthermore, propellants based on solutions of energetic materials in water are difficult to ignite, as the water must first be evaporated from the solution for successful combustion.

[0009] Another approach is the use of natural, i.e., non-premixed, monergols. Particular emphasis should be placed on the use of highly concentrated hydrogen peroxide solutions (90–98 wt.% in water). This relatively non-toxic substance, like hydrazine, can be easily decomposed catalytically. The major disadvantage of hydrogen peroxide solutions is their low performance compared to other comparable propellants, as well as their low stability, which limits their long-term storage. The use of nitromethane also represents a potential green propellant. This substance is an inexpensive and widely available laboratory solvent, but its properties significantly complicate its use as an aerospace fuel. The substance exhibits no or unstable combustion at low combustion chamber pressures and exhibits poor flammability.The substance is very sensitive to impact and is considered explosive.

[0010] EP 2 662 350 B1 discloses a gel-like, monergolic fuel in which the high combustion temperature is reduced by adding an additive to the fuel, by means of which the carbon is oxidised to carbon monoxide during combustion of the fuel and no oxygen is made available for the oxidation of hydrogen to water and of carbon monoxide to carbon dioxide.

[0011] EP 2 607 337 B1 discloses a gel-like, injectable single-component fuel consisting of a mixture of at least one mono-ergolic base fuel, namely a hydrocarbon containing at least one nitro group, and at least one gelling agent consisting of carbon particles or carbon nanotubes and at least one solid oxidizer with an average particle size of at most 0.4 millimeters.

[0012] DE 3342347 A1 discloses the use of monergolic and hypermonergolic propellants to generate propellant gases in propellant combustion chambers of barreled weapons, and the addition of additives to the propellant to improve combustion behavior. JP-S-4919452 B1 discloses the use of hydrogen peroxide, mononitromethane, isopropyl nitrate, ethylene oxide, and similar compounds as propellants for rocket engines. It is described that the addition of additives improves combustion properties. Various additives are described.

[0013] DE 2820783 C1 describes a solid propellant based on ammonium perchlorate.

[0014] Disclosure of the invention

[0015] The object of the invention is to create a fuel with improved properties for spacecraft and / or missiles

[0016] The objects are achieved by the features of the independent claim. Advantageous embodiments and advantages of the invention emerge from the further claims, the description, and the drawings.

[0017] The features listed individually in the patent claims can be combined with one another in a technologically meaningful manner and can be supplemented by explanatory facts from the description and by details from the figures, whereby further embodiments of the invention are shown.

[0018] According to one aspect of the invention, a nitromethane propellant for spacecraft and / or missiles is proposed, wherein the propellant comprises at least one additive in the form of an inhibitor that reduces impact sensitivity, wherein the inhibitor is dimethyl sulfoxide or wherein the inhibitor is at least one of n-butanol compounds or nitroethane or an ionic liquid, wherein the inhibitor is a desensitizer and improves impact sensitivity. Impact sensitivity is understood to mean the behavior of a propellant under mechanical stress. The mechanical stress can, for example, be a vibration that arises or occurs during transport of the propellant. This can cause the propellant to explode. The reduced impact sensitivity can prevent an explosion during transport. Impact sensitivity can be determined using the so-called BAM drop hammer test.In this test, a defined weight is dropped from a defined height onto the material being tested, exerting a defined impact energy on the material. The impact energy is the product of the drop height and the weight and is measured in joules.

[0019] It is known to add phlegmatizing agents to explosives or materials used for fire extinguishing. However, propellants have not been treated with phlegmatizing agents to date, as these can impair combustion characteristics. Surprisingly, tests have shown that the impact force can be improved while simultaneously maintaining sufficiently good combustion behavior by adding the inhibitor, which reduces impact sensitivity.

[0020] In a favorable embodiment, the proportion of the inhibitor can be 3 wt% to 40 wt%, in particular 5 wt% to 25 wt%.

[0021] In a favorable embodiment, a metallocene can be provided as a further additive, whereby the metallocene can improve ignitability and enable combustion at low pressures, particularly in the range of 10 bar to 20 bar. Additives such as metallocenes significantly improve the ignitability of nitromethane-based fuel compared to pure nitromethane and advantageously enable combustion at low combustion chamber pressures. The addition of an inhibitor, also known as a phlegmatizing agent, can make the combustion of the fuel significantly more stable. Furthermore, a possible deterioration in the impact sensitivity of the fuel associated with the addition of metallocenes can be counteracted by adding an inhibitor.

[0022] Thus, the combined addition of the inhibitor and the metallocene can achieve the advantage of reduced impact sensitivity and improved ignition behavior.

[0023] Depending on the fuel's favorable design, the metallocene content can be from 0.5 wt.% to 5 wt.%. Alternatively or additionally, the inhibitor content can be from 3 wt.% to 40 wt.%, in particular from 5 wt.% to 25 wt.%. These metallocene contents can advantageously improve the ignitability of a nitromethane fuel and promote combustion at low combustion chamber pressures. The inhibitor contents can advantageously reduce the fuel's sensitivity to impact.

[0024] According to a favorable design of the fuel, the metallocene can be at least one of the group consisting of chromocene and related substances, nickelocene and related substances, ferrocene and related substances, in particular ethylferrocene, butylferrocene, catocene.

[0025] The addition of, for example, 0.5 wt.% to 5 wt.% of ferrocene and related substances such as ethylferrocene, butylferrocene, catocene, as well as chromocene and related substances, as well as nickelocene and related substances, can significantly improve the ignitability of liquid and gel nitromethane propellants under an inert gas atmosphere. Additionally, combustion can advantageously be enabled in the low pressure range up to 12.5 bar. Depending on the fuel's favorable design, the inhibitor can be dimethyl sulfoxide. Dimethyl sulfoxide is an organic, non-aqueous solvent.

[0026] The use of the inhibitor dimethyl sulfoxide (DMSO) is particularly advantageous. Adding more than 6 wt.% of pure nitromethane can already significantly improve impact sensitivity. Adding 12 wt.% makes the mixture virtually impact-insensitive.

[0027] The addition of DMSO to nitromethane can advantageously act catalytically at elevated pressures and temperatures. Compared to the addition of n-butanol or pure nitromethane, decomposition occurs at lower temperatures. This behavior is particularly pronounced when ferrocene is added to a nitromethane-DMSO mixture. The exothermic reaction is now located at a significantly lower temperature.

[0028] For example, a mixture containing 85 wt% nitromethane, 13 wt% DMSO, 2 wt% ferrocene, or a similar mixture can be used advantageously as a cost-effective, non-toxic, and safe "green" missile or satellite propellant with high performance compared to hydrazine, ADN, and HAN propellants. In addition, this propellant contains no water and is therefore more easily ignited than propellants based on aqueous solutions of ADN or HAN.

[0029] According to a favorable design of the propellant, the inhibitor can be at least one of n-butanol, in particular in a proportion of 3 wt.% to 10 wt.%, or nitroethane, in particular in a proportion of 10 wt.% to 30 wt.%. The addition of 3 wt.% to 10 wt.% n-butanol or 10 wt.% to 30 wt.% nitroethane can advantageously improve impact sensitivity to values ​​greater than 10 J.

[0030] According to a favorable design of the propellant, the inhibitor can be an ionic liquid. In particular, the inhibitor can be ethyl ammonium nitrate (EAN). In particular, the inhibitor can contain a proportion of 4% to 30% by weight of the phlegmatizing agent.

[0031] Mixtures of 4 wt% to 12 wt% EAN with 1 wt% to 2 wt% ferrocene or ethylferrocene and nitromethane can be advantageously used as insensitive liquid Monergol propellants.

[0032] According to a favorable embodiment, the propellant may contain at least one organic gelling agent, in particular in a proportion of 1% to 10% by weight. An organic gelling agent may also advantageously act as an inhibitor to improve impact sensitivity.

[0033] The addition of 1% to 4% by weight of organic gelling agent, in particular a low molecular weight gelling agent (LMOG; for example, N-alkyl gluconamides, 12-hydroxystearic acids and salts, (oligo)ureas, alkoxybenzoic acids, N-(oligohydroxyalkyl)alkoxybenzamides, alkoxybenzhydrazines and hydrazides, alkoxybenzoyl semicarbazides, and alkoxybenzosulfonic acids) has proven particularly beneficial for improving the impact sensitivity of the nitromethane fuel. According to a favorable fuel design, the organic gelling agent can be at least one of a pyrogenic silica, a low molecular weight organic gelling agent, carbon particles, or carbon nanotubes. Such a gelling agent has proven particularly beneficial for improving the impact sensitivity of the nitromethane fuel.

[0034] Depending on the fuel's optimal design, the additive content can be between 10 and 20 wt.%. This allows the desired properties of the nitromethane fuel, such as good ignitability, burn-off at low combustion chamber pressures, and low impact sensitivity, to be achieved.

[0035] drawing

[0036] Further advantages will become apparent from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0037] It shows, for example:

[0038] Fig. 1 Results of closed-cup differential scanning calorimetry measurements on various nitromethane propellants for spacecraft and / or missiles according to embodiments of the invention. Embodiments of the invention

[0039] The figure shows only examples and is not to be understood as limiting.

[0040] Before describing the invention in detail, it should be noted that it is not limited to the specific components of the device and the specific method steps, as these components and methods may vary. The terms used herein are intended solely to describe particular embodiments and are not intended to be limiting. Furthermore, when the singular or indefinite articles are used in the description or claims, this also refers to the plural of these elements, unless the overall context clearly indicates otherwise.

[0041] The directional terminology used below, including terms such as "left," "right," "top," "bottom," "before," "behind," "after," and the like, is intended solely to enhance understanding of the figure and is in no way intended to limit its generality. The components and elements depicted, as well as their design and use, may vary according to the considerations of a person skilled in the art and may be adapted to specific applications.

[0042] The proposed nitromethane propellant for spacecraft and / or missiles can advantageously contain at least one additive of an inhibitor that reduces impact sensitivity, wherein the inhibitor is dimethyl sulfoxide or wherein the inhibitor is at least one of n-butanol compounds or nitroethane or an ionic liquid, wherein the inhibitor is a desensitizer and improves impact sensitivity. This improves the properties of the propellant with regard to ignitability, burn-up at low combustion chamber pressures, and impact sensitivity. A metallocene can be added to the propellant as a further additive. Advantageously, the proportion of the metallocene can be 0.5 wt.% to 5 wt.% and / or the proportion of the inhibitor can be 3 wt.% to 40 wt.%, in particular 5 wt.% to 20 wt.%.The metallocene may be at least one selected from the group consisting of chromocene and related substances, nickelocene and related substances, ferrocene and related substances, in particular ethylferrocene, butylferrocene, catocene.

[0043] The total amount of additives can advantageously be between 10% and 20% by weight.

[0044] The propellant can advantageously contain at least one inhibitor to reduce impact sensitivity. The inhibitor can advantageously be, for example, dimethyl sulfoxide (DMSO). The inhibitor can also be at least one of n-butanol, in particular in a proportion of 3 wt.% to 10 wt.%, or nitroethane, in particular in a proportion of 10 wt.% to 30 wt.%. Furthermore, the inhibitor can be an ionic liquid. In particular, the inhibitor can be ethyl ammonium nitrate, in particular in a proportion of 4 wt.% to 30 wt.%.

[0045] Advantageously, the fuel may contain at least one organic gelling agent, in particular in a proportion of 1 wt.% to 10 wt.%. The organic gelling agent may, for example, be at least one of a pyrogenic silica, a low-molecular-weight organic gelling agent, carbon particles, or carbon nanotubes.

[0046] Table 1 shows measured drop hammer impact sensitivities Si for nitromethane propellants with different additives.

[0047]

[0048] Table 1 : Results of drop hammer impact sensitivities for

[0049] Nitromethane fuels

[0050] Table 1 shows that the addition of an inhibitor such as n-butanol, nitroethane or DMSO shifts the shock sensitivity to higher values, thus improving it.

[0051] The addition of ferrocene worsens the impact sensitivity to some extent.

[0052] Figure 1 shows results of closed-cup differential scanning calorimetry (DSC) measurements on various nitromethane propellants for spacecraft and / or missiles according to embodiments of the invention. The DSC measurement signals 20 are plotted in units of pV / mg as a function of temperature 10 in °C. Curve 30 represents measurements for pure nitromethane. Curve 32 represents measurements for a nitromethane propellant containing 6 wt% n-butanol, curve 34 for a nitromethane propellant containing 13 wt% DMSO, and curve 36 for a nitromethane propellant containing 13 wt% DMSO and 2 wt% ferrocene.

[0053] Figure 1, which depicts the DSC curves of several nitromethane-based fuels, shows that the addition of DMSO (here 13 wt%) to nitromethane has a catalytic effect at elevated pressures and temperatures. Compared to the addition of n-butanol or pure nitromethane, decomposition occurs at lower temperatures, as evidenced by the increase and peak of the exothermic reaction.

[0054] This behavior is particularly pronounced when ferrocene is added to a nitromethane-DMSO mixture. The exothermic reaction is now located at a significantly lower temperature.

[0055] The pure nitromethane fuel (curve 30) exhibits the peak of the exothermic reaction at approximately 380 °C. Nitromethane fuel with 6 wt% n-butanol (curve 32) exhibits the peak at approximately 390 °C. Nitromethane fuel with 13 wt% DMSO (curve 34) exhibits a broad peak at approximately 360 °C, while nitromethane fuel with 13 wt% DMSO and 2 wt% ferrocene (curve 36) exhibits the peak at approximately 280 °C.

[0056] This is consistent with combustion chamber tests and so-called Strand-Bumer tests. In Strand-Bumer tests, a mixture of 85 wt.% nitromethane, 13 wt.% DMSO, and 2 wt.% ferrocene could be ignited even at 12.5 bar inert gas pressure. In combustion chamber tests, stable combustion was achieved with this mixture even at 13 to 15 bar. With a comparable mixture, but with 6 wt.% n-butanol as an inhibitor, only a minimum combustion chamber pressure of 40 bar could be demonstrated.

[0057] Based on the measurement results presented, the following fuels made from nitromethane with additives prove to be suitable for various applications:

[0058] Fuels for spacecraft and missiles:

[0059] 85 wt% nitromethane, 13 wt% DMSO, 2 wt% ferrocene;

[0060] 92 wt% nitromethane, 6 wt% n-butanol, 2 wt% ferrocene;

[0061] 92 wt% nitromethane, 6 wt% n-butanol, 2 wt% metal salt (e.g. chromium(III) acetyl acetonate);

[0062] 94 wt% nitromethane, 6 wt% dimethyl sulfoxide;

[0063] 92 wt% nitromethane, 6 wt% n-butanol, 2 wt% ferrocene;

[0064] 90 wt% nitromethane, 8 wt% EAN, 2 wt% ferrocene.

[0065] Gel-like propellants for missiles:

[0066] 85 wt% nitromethane, 10 wt% DMSO, 4 wt% LMOG gelling agent, 1 wt% ethylferrocene;

[0067] 88 wt% nitromethane, 7 wt% EAN, 4 wt% LMOG gelling agent, 1 wt% ethylferrocene.

[0068] Reference symbol

[0069] 10 Temperature

[0070] 20 signals

[0071] 30 Nitromethane, pure

[0072] 32 nitromethane + 6% by weight n-butanol

[0073] 34 Nitromethane + 13 wt% DMSO

[0074] 36 Nitromethane + 13 wt% DMSO + 2 wt% Ferrocene

Claims

Claims 1. A nitromethane propellant for spacecraft and / or missiles, wherein the propellant comprises at least one additive in the form of an inhibitor reducing impact sensitivity, wherein the inhibitor is dimethyl sulfoxide or wherein the inhibitor is at least one of n-butanol compounds or nitroethane or an ionic liquid, wherein the inhibitor is a phlegmatizing agent and improves impact sensitivity.

2. Propellant according to claim 1, wherein the proportion of the inhibitor is 5 wt% to 40 wt%, in particular 5 wt% to 25 wt%.

3. Fuel according to claim 1, wherein a metallocene is provided as a further additive, wherein the metallocene improves the ignitability and enables combustion at low pressures, in particular in the range of 10 bar to 20 bar.

4. A fuel according to claim 3, wherein the proportion of metallocene is 0.5 wt% to 5 wt%.

5. Fuel according to claim 3 or 4, wherein the metallocene is at least one selected from the group consisting of chromocene and related substances, nickelocene and related substances, ferrocene and related substances, in particular ethylferrocene, butylferrocene, catocene.

6. Fuel according to one of the preceding claims, wherein n-butanol is present as inhibitor in a proportion of 3 wt.% to 10 wt.%.

7. Fuel according to one of the preceding claims, wherein nitroethane is present as inhibitor, in particular in a proportion of 10 wt.% to 30 wt.%.

8. Fuel according to one of the preceding claims, wherein the inhibitor is the phlegmatizing agent ethyl ammonium nitrate, in particular in a proportion of 4 wt.% to 30 wt.%.

9. Fuel according to one of the preceding claims, wherein the Fuel contains at least one organic gelling agent, in particular in a proportion of 1 wt.% to 10 wt.%.

10. The fuel of claim 8, wherein the organic gelling agent is at least one of a fumed silica, a low molecular weight organic gelling agent, carbon particles, carbon nanotubes. 11 . Fuel according to one of the preceding claims, wherein the proportion of additives is between 10 wt.% and 20 wt.%.

Images