FUEL CELLS ON THE NASA SPACE SHUTTLE ORBITER

This research reviews the fuel cells used on the NASA space shuttle orbiter vehicles. The presentation of the review focuses on (1) fuel cell structure, (2) fuel cell components, (3) fuel cell reactants, (4) fuel cell storage and distribution, and (5) fuel cell operation. The review of fuel cell operation includes consideration of (a) parameter and (b) processing.

The concept of the fuel cell is not a new technology. The fuel cell dates to 1839 and British scientist Sir William Grove. The first fuel cell appeared in 1842 (Connelley 1). Practical applications of the fuel cell concept proved elusive, however, until the National 'ronautics and Space Administration (NASA) funded the development of fuel cell applications for early space flights. The Soviet space program also used fuel cell technology. Today, NASA uses advanced fuel cell technology in its space shuttle orbiter vehicles (Hart 1; Stone, Allakhverdov, and Lawler 468).

Fuel cells are relatively uncomplicated devices. Table 1 below illustrates the essential components required to support the fuel cell process of producing electricity.

Each of the three fuel cell systems on a NASA space shuttle orbiter consists of 96 fuel cells contained in three substacks. Manifolds extend through the length of the substacks (Hoogers 181). The fuel cells contain an electrolyt

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r of the fuel cell power plant to the Freon-21 coolant loop system. The location of the coolant loop system in the mid-fuselage of the space shuttle orbiter. Internal control of the circulating fluid maintains the cell stack at a normal operating temperature of approximately 930 C (Dicks and Larminie, 616). When the reactants enter the fuel cells, they flow through a pre-heater that raise their temperature to a minimum of 4.50 C from cryogenic temperature levels. The reactants then enter a two-stage, integrated dual gas regulator module. The first stage of the regulator reduces the pressure of the hydrogen and oxygen to 135-to-150 psia (atmospheric pressure). The second stage reduces the oxygen pressure to a range of 62-to-65 psia and maintains the hydrogen pressure at 4.5-to-6 psia differential below the oxygen pressure. The regulated oxygen lines connect to an accumulator, which maintains an equalized pressure between the oxygen and the fuel cell coolant. If the oxygen's and hydrogen's pressure decreases, the coolant's pressure also decreases to prevent a large differential pressure inside the stack that could deform the cell stack structural elements (Dicks and Larminie, 616). Upon leaving the dual gas regulator modul
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Approximate Word count = 3594
Approximate Pages = 14 (250 words per page)

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