Rockets, hydrogen-powered

Fossil fuels are nonrenewable, and combustion products contaminate the atmosphere. Consequently, scientists are searching for new sources of energy. One possibility is molecular hydrogen, which releases energy when it reacts with oxygen 2 H2(g) + 02(g) 2H2 0(/) + Energy Hydrogen powers the rockets of the space shuttle,... 

Alfred Stock (1876-1946) studied the hydrides of some of these metal-like elements. A hydride occurs when hydrogen gains (or shares) an electron rather than losing its single electron when it combines with metals or metallic-like elements. Stock spent years experimenting with boron hydrides (B Hg and BH ), which were used as hydrogen-based rocket fuels powerful enough to lift rockets into space. 

Liquid hydrogen has been used as a fuel in the U.S. space program for many years. Hydrogen powered the Saturn V rocket that carried the first astronauts to the moon, and it fuels the rocket engines of the space shuttle (Figure 14.14a). 

Monomethylhydrazine is a clear, colorless liquid used extensively in military applications as a missile and rocket propellant, in chemical power sources, and as a solvent and chemical intermediate. Upon contact with strong oxidizers (e.g., hydrogen peroxide, nitrogen tetroxide, chlorine, fluorine) spontaneous ignition may occur. 

Of a special astronomical interest is the absorption due to pairs of H2 molecules which is an important opacity source in the atmospheres of various types of cool stars, such as late stars, low-mass stars, brown dwarfs, certain white dwarfs, population III stars, etc., and in the atmospheres of the outer planets. In short absorption of infrared or visible radiation by molecular complexes is important in dense, essentially neutral atmospheres composed of non-polar gases such as hydrogen. For a treatment of such atmospheres, the absorption of pairs like H-He, H2-He, H2-H2, etc., must be known. Furthermore, it has been pointed out that for technical applications, for example in gas-core nuclear rockets, a knowledge of induced spectra is required for estimates of heat transfer [307, 308]. The transport properties of gases at high temperatures depend on collisional induction. Collision-induced absorption may be an important loss mechanism in gas lasers. Non-linear interactions of a supermolecular nature become important at high laser powers, especially at high gas densities. 

Combustion is an oxidation-reduction reaction between a nonmetallic material and molecular oxygen. Combustion reactions are characteristically exothermic (energy releasing). A violent combustion reaction is the formation of water from hydrogen and oxygen. As discussed in Section 9.5, the energy from this reaction is used to power rockets into space. More common examples of combustion include the burning of wood and fossil fuels. The combustion of these and other carbon-based chemicals forms carbon dioxide and water. Consider, for example, the combustion of methane, the major component of natural gas ... 

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. 

Liquid hydrogen fuel powers the rockets of the U.S. space shuttle. 

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