3 the fuel cell removed from the orbiter Discovery is lowered onto a bracket on the work stand.

In NASA Kennedy Space Center’s Orbiter Processing Facility bay 3, the fuel cell removed from the orbiter Discovery is lowered onto a bracket on the work stand. Fuel cells are located under the forward portion of the payload bay. They make power for the orbiter by mixing hydrogen and oxygen to produce electricity. Fuel cells also create potable water that is pumped into storage tanks for the crew to use in orbit. Discovery is the designated orbiter for the second return-to-flight mission, STS-121, scheduled for launch in May. Photo credit: NASA/Kim Shiflett