Because the oxidizer has no significant structural strength, the fuel must not only perform well but must also supply the necessary form and rigidity to the grain. The fuels used are hydrocarbons, such as asphaltic-type compounds, or plastics. The oxidizer is usually ammonium nitrate, potassium chlorate, or ammonium chlorate, and often comprises as much as four-fifths or more of the whole propellant mix. Here, separate fuel and oxidized chemicals are used, intimately mixed in the solid grain. The other type of solid propellant is the composite. They are often processed and formed by extrusion methods, although casting has also been employed. These propellants lend themselves well to smaller rocket motors. The molecules are unstable, and upon ignition break apart and rearrange themselves, liberating large quantities of heat. The first, the so called double-base propellant, consists of nitrocellulose and nitroglycerine, plus additives in small quantity. Two general types of solid propellants are in use. Some propellants are used in very large quantities, the availability of Propellant, an entire new chemical plant must be built. In some cases, in order to obtain adequate amounts of a Upon contact with air, or upon contacting any organic substance, or inĬertain cases upon contacting most common metals.Īlso essential to the choice of a rocket propellant is itsĪvailability. Substances can be used to contain them some may burn spontaneously Most war gases some are so corrosive that only a few special Many propellants are highly toxic, to a greater degree even than Use, gasoline is, of course, highly flammable and must be handled withĬare. To be a very active chemical hence, most propellants are corrosive,įlammable, or toxic, and are often all three. Unfortunately, almost any propellant that gives good performance is apt Some are unstable to varyingĭegrees, and cannot be safely stored or handled. Render their use difficult or impossible. Others exhibit peculiarities in combustion that Some are not adequate as coolants for the hot SomeĬhemicals that yield excellent specific impulse create problems inĮngine operation. Other criteria must also be considered in choosing propellants. Partly offsets the high specific impulse of the hydrogen propellant. However, it is a veryīulky substance, requiring large tanks. Is energetic and its combustion gases are light. Of dense propellant can be carried in a smaller, lighter tank than the Hydrogen (the lightest), carbon, oxygen, fluorine, and the lighterĪnother important factor is the density of a propellant. Products containing simple, light molecules embodying such elements as To be efficient, therefore, a propellant should have a large heat ofĬombustion to yield high temperatures, and should produce combustion Temperature, and from exhaust gas having very low (molecular) weight. High values of specific impulse are obtained from high exhaust-gas The most energeticĬhemical propellants are theoretically capable of specific impulses up Ranging from about 175 up to about 300 seconds. GENERAL FEATURES OF ROCKET PROPELLANTSĬhemical propellants in common use deliver specific impulse values
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