NASA's Space Shuttle Orbiter Electrical power for NASA's Space Shuttle Orbiter is provided by fuel cell power plants designed, developed, and built by UTC Power. In the Orbiter, a complement of three 12-kilowatt fuel cells produces all onboard electrical power; there are no backup batteries, and a single fuel cell is sufficient to ensure safe vehicle return. In addition, the water produced by the electrochemical reaction is for the crew to drink and for spacecraft cooling.

Each fuel cell is a self-contained unit 14 x 15 x 45 inches, weighing 270 pounds. They are installed under the payload bay, just aft of the crew compartment. Hydrogen and oxygen from cryogenic tanks fuel the power plants. Each fuel cell is capable of providing 12 kilowatts continuously, and up to 16 kilowatts for short periods.

Each power plant contains 96 individual cells of the alkaline (KOH) electrolyte technology, which are connected to achieve a 28-volt output. The cells are over 70 percent efficient (a typical combustion engine is about only 25 percent efficient); this high efficiency and lightweight led NASA to select fuel cells to power the Space Shuttle Orbiter.

In the Shuttle program, the fuel cells have demonstrated outstanding reliability (over 99 percent availability), with a cumulative operating time in excess of 101,000 hours. The fuel cells have a 2600-hour (6 mission) overhaul interval, at which time all servicing and maintenance is performed at our facility. We have successfully completed an upgrade program that extends the overhaul interval to 5000 hours.

Orbiter fuel cells are our second-generation space power plants; we also produced the fuel cells for the Apollo program. The Orbiter units represent a significant technology advance over Apollo, producing about 10 times the power from a similar size package.

For more information about the Space Shuttle and other space programs, please visit the Johnson Space Center and the Kennedy Space Center.