Hypergolic mixture

Hypergolic A hypergolic mixture ignites upon contact of the components without any external source of ignition (heat or flame). The only field, in which this is a desirable event, is in rocket fuel research. Accidental mixing of incompatible materials can lead to a fire or explosion. Here is one example provided by the staff at ILPI of what can happen, when incompatibles are mixed. Always read the labels on your bottles (don t assume a chemical s identity by the shape, size, or color of the bottle), and know what materials are incompatible with the chemicals that you are using. 

Munjal, N. L. et al., Amer. Inst. Aero. Astronaut. J., 1972, 10, 1722-1723 The effects of dichromates in promoting ignition of non-hypergolic mixtures of red fuming nitric acid with cyclohexanol, 2-cresol or 3-cresol, and furfural were studied. Ammonium dichromate was most effective in all cases, and the only effective catalyst for cyclohexanol. Potassium chromate and potassium dichromate were also examined. 

In mixtures containing nitric acid various fuels may be employed. Fuels used for hypergolic ones, i.e. those which autoignite on mixing, differ essentially from those used in other mixtures. In hypergolic mixtures, fuels are used which reac. violently with nitric acid, e.g. aliphatic or aromatic amines, furfuryl alcohol, mercapt tans, hydrazine etc. It is also advisable to add surface-active substances to the mixture-... 

Nitromethane (Vol. I, p. 579) may be used as a monergol propellant. However its negative oxygen balance may be reduced by the addition of liquid oxidants, e.g. of tetranitromethane to form a bipropellant. In practice, however, nitromethane decomposes too slowly, and it is difficult therefore to obtain hypergolic mixtures from it. To facilitate and accelerate the decomposition of mixtures with nitromethane it is necessary to add a catalyst, such as a salt of chromic acid. 

The strong oxidizing agent dinitrogen tetroxide is used for many applications. It is employed as a catalyst in oxidation reactions and as an inhibitor in the distillation of acrylates. It is also used in the manufacture of explosives and as bleach. In rocket propellants, it is used in a hypergolic mixture with hydrazine derivatives. The command module of the Apollo mission used a 1 1 mixture of hydrazine and N,N -dimethylhydrazine with N2O4 as the oxidant. 

Many mixtures of oxidizers and oxidizable chemicals catch fire spontaneously and are called hypergolic mixtures. Nitric acid and phenol form such a mixture. 

Mixtures with triethylaluminium have been used as hypergolic igniters in rocket propulsion systems. 

Hydrocarbons, 1,1 -Dimethy lhy drazine Ingolgaonkar, M. B. et al., J. Armam. Stud, 1979, 15(2), 33-42 Presence of the hydrazine confers hypergolicity upon mixtures of several non-hypergolic hydrocarbons with red fuming nitric acid. 

Though neither of the components is individually hypergolic with red fuming nitric acid, mixtures with magnesium containing 20% and 30% of 2-nitroaniline ignite with 67 and 23 ms delay, respectively. 

Miyajima, H. et al., Combust. Sci. Technol., 1973, 8, 199-200 Combinations with hydrazine, methylhydrazine, 1,1-dimethylhydrazine or mixtures thereof are hypergolic and used in rocketry [1]. The hypergohc gas-phase ignition of hydrazine at 70-160°C/53-120 mbar has been studied [2],... 

Blends of perchloryl fluoride with halogen fluorides are homogeneous and stable. When these are used as storable liquid oxidizers for rocket propulsion, the halogen fluoride usually confers hypergolicity, increased density, and lowered vapor pressure whereas the perchloryl fluoride provides oxygen needed for efficient combustion of carbon in the fuel or of certain metal additives. The mixtures are thermally stable and their... 

Hypergolic Oxidizer and Fuel Mixtures. A list of oxidizers and fuels which are hypergolic follows RFNA with aniline (Ref 7) N2H4 (Refs 8 9) H2 (Ref 10) toluene (Ref 11) diethylenetriamine (Ref 8) MMH (Ref 8) ... 

M. Kilpatrick L.L. Baker, Jr, A study of fast reactions in fuel-oxidant systems, FifthSymp Comb, Reinhold, NY, (1955) 26) S.A. Masier et al, Hypergolic ignition of light hydrocarbon fuels with fluorine-oxygen (FLOX) mixtures, ... 

Motoren Werke (BMW). By 1945 some 6000 fuel-nitric acid mixtures had been tested. Some of these were hypergolic... 

Hypergols, i.e. systems composed of several (two, at least) liquids which when mixed react spontaneously, usually after a certain induction period (e.g. a mixture of petrol with an admixture of aromatic amines which reacts spontaneously with nitric acid). For practical purposes the induction period of hypergols should be as short as possible—at any rate shorter than 0.1 sec. 

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