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 electrolyte consisting of potassium hydroxide and water, an oxygen electrode (cathode), and a hydrogen electrode (anode).
The accessory section monitors the reactant flow, removes waste heat and water from the chemical reaction, and controls the temperature of the stack. The accessory section consists of the hydrogen and oxygen flow system, the coolant loop, and the electrical control unit (Hoogers 181).
Fuel cells typically contain expensive metal catalysts. The function of the catalysts is to release electrons from hydrogen or other reactants. Contaminants, h...