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My Shuttle's in the Shop
Enveloped in a labyrinth of workstands and platforms, Shuttle Discovery is nearly invisible inside the Orbiter Processing Facility (OPF) at NASA's Kennedy Space Center in Florida.

Discovery inside the Orbiter Processing FacilityFlying missions puts tremendous stress on the Shuttle orbiter, the white and black spacecraft that takes off like a rocket and lands like a plane. So every few years, each orbiter goes through a routine but invasive series of inspections and special tests called the Orbiter Maintenance Down Period (OMDP).

This bird's-eye view of the Orbiter Processing Facility shows Shuttle Discovery surrounded by platforms and equipment.

"It's basically an overhaul of the whole vehicle," said Stephanie Stilson, NASA vehicle manager for Discovery.

Modifications and upgrades to orbiter systems are made during the Orbiter Major Modification (OMM) portion of OMDP. Modifications range from the simple -- such as changing a part's label -- to something as complicated as the first-time changeout of the orbiter's rudder speed brake's operating mechanism. This time around, Discovery underwent 99 upgrades and 88 special tests, including new return-to-flight changes.

"During the typical sequence of preparations for launch, called the 'flow,' there are about 4,000 requirements to meet in about 250,000 hours of work," said Carol Scott, NASA lead project engineer and chief engineer for Discovery. "But during an OMDP, like this one, there are more than 8,000 requirements. It takes about a million hours of work, because of the amount of detail in the work."

Discovery lands at KSC after STS-105Aug. 22, 2001: Discovery touches down on KSC runway 15, completing the 11-day STS-105 mission to the International Space Station. STS-105 was Discovery's most recent mission before beginning its overhaul, known as an OMDP.

To allow thorough structural inspections, nearly all accessible parts were removed, exposing the orbiter's airframe. Constructed mostly of high-grade aluminum, the airframe is inspected for corrosion and wear and tear. Corrosion is often not visible to the naked eye, occurring in patches so tiny that it sometimes requires being magnified up to 10 times its original size.

Additionally, the orbiter endures painstaking wiring inspections. It is crucial that any damaged wires or cables are found and fixed. This may sound simple, but it's a pretty tall order: Each orbiter houses about 150 miles of wiring!

Discovery's overhaul, which began in September 2002, marks the first time an OMM was performed at KSC. Previous overhauls occurred at the California plant where the orbiters were built.

"As the Shuttle program progressed, the KSC team spent so much time with their hands on the vehicles -- from landing to launch, every mission -- that we became the experts," said Scott.

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+ Part 2: Into the Orbiter
+ Part 3: From Nose Cap to Body Flap
Anna Heiney
NASA's John F. Kennedy Space Center