US2813013A - Blends of acetylenic hydrocarbons - Google Patents

Description

BLENDS OF ACETYLENIQ HYDROC f 1 No Drawing. Application May 21, 1956, Serial No. 586,329

1 Claim. c1. 52-5 This invention relates to improvements in propellants, and more particularly pertains to improvements in acetylenic hydrocarbons for use as rocket fuels.

It is well known that various jet propulsion devices including both monopropellant and bipropellant rocket systems and ram jets, have assumed great importance in recent times. The subject is of ever increasing importance in jet propulsion systems as used in airplanes, guided and unguided missiles, and jet-assisted takeoff units.

Generally, the fuels that can be used for these purposes can be classified roughly into three categories. These three categories consist of the low performance type, the intermediate performance type, and the high performance type. Examples of the low performance type include the kerosene and refined petroleum fractions and the simple alcohols such as ethyl alcohol. These fuels are low in cost but they have relatively low specific impulse, or driving force, and they are not hypergolic; that is, they do not ignite spontaneously with the oxidizing agents with which they are employed commonly. At the other extreme, the jet fuels having very high specific impulse, such as diborane and the like, are very expensive, diflicult to produce, and are generally quite toxic.

Although pure acetylenic hydrocarbons having prohibitively high melting points cannot be used as liquid fuels, by blending these high melting point materials with particular other acetylenic hydrocarbons of lower melting point, desirable blend characteristics can be obtained, thereby retaining a major portion of the advantageous features of both components. By suitably selecting the components and proportions of such blends, the stability characteristics of the blend to storage over prolonged periods of time and to elevated temperatures, as well as their shock sensitivity, can also be improved materially.

A principal object of this invention is to provide a blend of acetylenic hydrocarbons for use as rocket fuels.

Another object is to provide such a blend having practical logistics, boiling and freezing points, vapor pressure, viscosity, density, specific impulse, heat of combustion, flame velocity, stability, ignition, corrosion and metal salts formation, and toxicity characteristics.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same ice becomes better understood by reference to the following detailed description.

An acetylenic hydrocarbon having good ignition properties is dimethyl divinyl diacetylene, 2,7-dimethyl 1,7 octadiene 3,5-diyne, having the structural formula Tests of this compound indicated the high ignition rating of 8 with hexane dilution and 7 with benzene dilution. However, the compound has several undesirable characteristics. Its freezing point is 23 F., and it exhibits a high degree of instability towards mechanical and thermal shock. Its mechanical shock sensitivity is 80% on the drop weight impact test, one of the highest ratings of acetylenic hydrocarbons, and it bursts into flame when subjected to thermal shock.

Methyl vinyl acetylene, Z-methyl l-butene 3-yne, having the structural formula has a very low freezing point, lower than l12 F., and a high heat of combustion, 19,680 B. t. u. per pound. It is also far more stable than dimethyl divinyl diacetylene, standing at 40% on the rating scale. Further, it is much cheaper to manufacture than the dimethyl divinyl diacetylene. Methyl vinyl acetylene is further characterized by an ignition rating of 5 with hexane or benzene dilution.

A 30% mixture of dimethyl divinyl diacetylene in methyl vinyl acetylene remained liquid at 40 F. This blend has an ignition rating of 7 with hexane dilution, and 6 with benzene dilution, an appreciable improvement over the 5 rating of methyl vinyl acetylene with both dilutions. The impact shock rating of the blend is substantially less than the rating of the dimethyl divinyl diacetylene.

The blend described thus provides an acetylenic hydrocarbon rocket fuel having an ignition rating almost as good as that of the original dimethyl divinyl acetylene, as well as substantially improved shock resistance making feasible its use for the purposes intended.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

We claim:

An acetylenic hydrocarbon rocket fuel consisting of a 30% mixture of dimethyl divinyl diacetylene in methyl vinyl acetylene.

References Cited in the file of this patent UNITED STATES PATENTS 2,573,471 Malina et al Oct. 30, 1951 2,702,984 Britton et al Mar. 1, 1955