Rocket propellants monopropellants

Uses Laboratory reagent for detecting double bonds in organic compounds oxidizer in rocket propellants monopropellant increase octane rating for diesel fuel. 

The pentazolate anion. Ns (11.2), is estimated to have a half-life of 2.2 days, whereas that of the parent pentazole HN5 is predicted to be only ca 10 min in methanol at 0 Although HN5 is unknown, the cyclic anion N5 has been detected by tandem mass spectrometric studies of 4-hydroxyphenylpentazole. Similarly to its congener P5 (Section 11.2), N5 (isoelectronic with cyclopenta-dienide [C5H5] ) has the potential to form metallocene-like complexes. The acyclic (V-shaped) cation Ns has been isolated as a hexafluoroantimonate salt, which decomposes at ca 70 °C. The estimated energy density of [N5] [N5] is approximately twice that of hydrazine, a well-known rocket propellant, suggesting that this ionic polynitrogen allotrope would be an excellent monopropellant... 

Liquid rocket propellants are subdivided into monopropellants and bipropellants. Monopropellants are liquids which burn in the absence of external oxygen. They have comparatively low energy and specific impulse and are used in small missiles which require low thrust. Hydrazine is currently the most widely used monopropellant however, hydrogen peroxide, ethylene oxide, isopropyl nitrate and nitromethane have all been considered or used as monopropellants. Information on the performance of some monopropellants is presented in Table 8.3. 

For liquid rocket propellants, there is a difference between mono and bipropellants. Monopropellants are endothermic liquids (e.g. hydrazine), which decompose exothermically - mainly catalytically (e.g. Shell-405 Ir/Al203) - in the absence of oxygen ... 

Hydrogen peroxide has been used as a monopropellant, especially in various solutions with water. It was used as a rocket propellant in the X-15 research aircraft. However, because of storage stability problems and low performance, hydrogen peroxide now is no longer used. 

RocketPropella.nts, Liquid propellants have long been used to obtain maximum controUabiUty of rocket performance and, where required, maximum impulse. Three classes of rocket monopropellants exist that differ ia the chemical reactions that release energy (/) those consisting of, eg, hydrogen peroxide, ethylene oxide, C2H4O and nitroethane, CH2CH2NO2 that can undergo internal oxidation—reduction reactions (2) those... 

The use of N2H4 as a hypergolic propellant fuel for rocket propulsion is discussed in detail in this Vol under Hypergolic Propellants. It has also been used extensively as a monopropellant fuel or in combination with hydrazine nitrate and/or water as a thruster for maneuvering space vehicles (Ref 31)... 

The most interesting feature of the decomposition flames is their analogy to flames of the solid monopropellants. In fact, many of these substances, which are ordinarily liquids, may support a flame directly from the liquid phase without auxiliary vaporization of the liquid. In this case, the flame supplies the necessary heat of vaporization or decomposition in exact analogy to the solid propellant flame.8 The principal usefulness of a decomposition flame is found in the simplicity of design and control of a rocket powered by such a flame, even though more powerful fuels are readily available. A recent example, which has been featured in the news, is the hydrogen peroxide attitude-control rocket used in the artificial earth satellites of the U.S.A. 

Another non-equilibrium effect arises when the product composition contains a condensible substance. Solid propellant formulations based upon potassium perchlorate form solid potassium chloride and the acetylenic monopropellants upon decomposition form large quantities of carbon particles, as do very fuel-rich mixture ratios of hydrocarbon propellant systems. More recently metal and metal compounds have been used as fuels and form product oxides which are very high boiling point compounds that condense to varying degrees in the rocket chamber and nozzle. For example, estimates indicate that the normal boiling points of Li20, BeO,... 

The advantages of a monopropellant over a bipropellant combination result primarily from a substantial reduction in the number of components in the tankage and flow hardware. The attractive simplications in the propulsion system resulting from the use of monopropellants are obtained only at the expense of a reduced specific impulse. The resulting implied trade-off between simplicity and propellant performance limits the attractiveness of monopropellants to propulsion systems where a simplicity and the usually associated reliability which comes with simplicity are premium desired characteristics. Typical applications have included attitude control rockets, vernier rockets for mid-course trajectory corrections, and other low thrust propulsors, especially those having a requirement for pulsed operation or repeated restarts. Monopropellants also find application as a source of relatively low temperature working fluids, as for driving gas turbines. 

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