SE528301C2 - Liquid propellant, comprising ammonium dinitramide solution, used for spacecraft, contains formamide - Google Patents

Abstract

The propellant contains formamide as a fuel component. A liquid single-component propellant comprises a solution of ammonium dinitramide (ADM) in a mixture of water and fuel comprising formamide.

Description

20 25 528 301 2 hydrocarbons, the solubility is lower. However, to maximize performance, a hydrocarbon is needed to balance the excess oxygen at ADN. In the optimal fuel for this type of fuel, it should therefore be possible to solve as much DNA as possible. The solubility of a salt generally increases with increasing polarity of the solvent. It is therefore likely that a good hydrocarbon for this application should have as high a dielectric constant, a, as possible. Furthermore, the hydrocarbon should have as high a combustion shield, AHc, (or as low oxygen balance, Q) as possible to minimize the amount of hydrocarbon in the propellant as the solubility of the ADN decreases with increasing hydrocarbon content. WO 00150363 mentions a large number of possible fuels, e.g. MN-dimethylformamide (DMF) and N-methylformamide (monomethylformamide MMF).

The invention will be described in more detail below in connection with the data in Tables 1-2 and Fig. 1, which show the results of microcalorimeter tests of ADN in admixture with various fuel components and water.

Table 1 shows data for DMF, MMF and for methanol and N-ethylformamide (monoethylformamide MEF) and for formamide used in the present invention.

Table 1.

Fuel Methanol Formamide MMF DMF MEF sum formula 014.0 cnano czusuo canmo caHlNo M., (g / mol) 82,042 ^ 45,041 59,088 78,094 78,094 0 (%) -149,798 -88805 -148,978 488,054 -188,054 a at 0 ° c 37.8 125.0 220.4 42.1 85 220 200 153 198 (0 ° C) AH, (kJ / moi) -2885 -2540 -281 -2393 -818 AH. (kJ / g) 22,878 12,815 21,001 28,582 25,512 p (g / cmñ 0.79 1.13 1.01 0.94 0.98 From the reasoning above it can be concluded that the optimal fuel should be MMF due to its high heat of combustion (almost as high as methanol) and its extreme It is therefore very surprising that a fuel with formamide as fuel has been shown to give better performance than MMF, despite the formamide's very low combustion protection and significantly lower dielectric constant.

Table 2 shows data for three different propellant compositions optimized for a minimum operating temperature of 0 ° C. As shown in Table 2, fuels with formamide as fuel have a 2.7% higher specific impulse (IW) than fuels with MMF as fuel and 2.7% better than with methanol as fuel. If the density is taken into account, the volume-specific impulse (p-lsp) will be 10.2% better than when methanol is used.

Table 2.

Fuel FLP-103 l = ll = -1os FLP-1o6 Fuel Methanol Formamide MMF ADN (° / °) 63.4 65.7 64.6 dike (%) 25.4 13.6 23.9 Fuel (%) 11.2 20.7 11.5 p (g / cma) at 25 ° c 1,310 1,405 1,357 AH, (J / g) _5620 -4110 _5030 l., (Ne / kg) 2492 2560 2492 pl., (Ne / ams) 3265 3597 3362 e * (m / s) 1342 1376 1342 T, (k ) 2033 2253 2067 lvl (g / mol) 22.20 23.49 22.30 It is of the utmost importance that the fuel used in the fuel is compatible with ADN in order to obtain a fuel that is thermally stable. Figure 1 shows the results from micro-calorie meter experiments where ADN was mixed in the 50/50 weight proportions with water, formamide, MMF and methanol, respectively. The measurements have been made at 80 ° C for 4 days.

The heat flux indicates the degree of chemical activity in the mixture, ie the degree to which the compounds in the mixture are incompatible with each other. As clearly shown in Figure 1, formamide is significantly more compatible with ADN than the other tested fuels and t.o.m. more compatible with ADN than water.

The propellant according to the invention can be optimized for a selected minimum use and storage temperatures when the solution is saturated on the DNA. The weight ratio of formamide / water in the solvent is in the normal case in the range 1.23 - 2.33 but can also be higher and varies with the selected lowest use temperature and the requirements for oxygen balance in the propellant. For a one-component fuel to be stored and used on a spacecraft, it is essential that the fuel can be used down to a relatively low temperature. The most common liquid one-component fuel in space today is hydrazine, which has a freezing point of + 2 ° C.

Example 1 shows a preferred composition of the fuel according to the invention if, as a starting point, it is chosen that the fuel should have at least as low a minimum use temperature as hydrazine and be saturated on ADN at 0 ° C.

Example 1.

ADN 65.7% by weight Formamide 20.7% by weight Water 13.6% by weight The weight ratio of formamide / water in the solvent in this case is 1.52.

Claims (4)

10 15 528 301 Patent claims: Liquid one-component propellant comprising a solution of ammonium dinitramide (ADN) in a mixture of water and fuel, characterized in that the fuel is formamide, HCONHz. ' Fuel according to Claim 1, characterized in that the weight ratio of formamide / water in the mixture is 1.23-2.33. Fuel according to claim 1, characterized by the amount of ADN is such that the solution is saturated at a selected minimum operating temperature for the fuel. Propellant according to Claim 1, saturated with ADN at 0 ° C, characterized in that it contains 65.7% by weight of DNA, 20.7% by weight of formamide and 13.6% by weight of water.