Fuel, rocket cryogenic

The reactants in most systems are considered to enter at the standard reference temperature 298 K. Consequently, the enthalpy terms in the braces for the reactants disappear. The JANAF tables tabulate, as a putative convenience, (Hj - H°29i) instead of (U°T - Ha(]). This type of tabulation is unfortunate since the reactants for systems using cryogenic fuels and oxidizers, such as those used in rockets, can enter the system at temperatures lower than the reference temperature. Indeed, the fuel and oxidizer individually could enter at different temperatures. Thus the summation in Eq. (1.10) is handled most conveniently by realizing that T 0 may vary with the substance j. 

In organizing the symposium, we made the usual division into solid and liquid rocket propellants. Most readers no doubt already know the relative merits of solid vs. liquid systems—viz., the instant readiness of solids (compared with cryogenic liquids), their higher density (important in volume-limited systems), and the relative simplicity of rocket construction liquids offer easy variation in thrust level and the attainment of higher specific impulses, the latter because physical separation permits the use of fuels and oxidizers that would be incompatible if premixed. 

Liquid hydrogen is very important as a fuel for powering missiles and rockets. It is used in laboratory research on the properties of some materials at cryogenic temperatures, work often associated with studies of superconductivity. Liquid hydrogen can be used as a fuel, for either propulsion or heating. 

Ignoring the cryogenic liquid market (e.g., rocket fuel) that accounts for 7% of the merchant market, in 2003 the total U.S. merchant hydrogen gas capacity was about 1 500 M Standard Cubic Feet (SCF)/day. Most of this merchant production capacity (92%) was located in three slates Texas with 560 M SCF/day, Louisiana with 440 M SCF/day, and California with 380 M SCF/day [5,6]. Also, the Chemical Market Reporter [5] writes, Another 3 billion SCF per day of captive hydrogen capacity exists at 145 locations in the US. Therefore, in 2003 the U.S. had a total capacity of about 4 500 M SCF/cUy, or about 127 M mVday. 

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