Kennedy Space Center workers installed three main engines into the shuttle Discovery this week for the orbiter's final launch later this year.

Using custom lifts and tractors, shuttle technicians moved the powerplants from the engine workshop into Orbiter Processing Facility bay 3, Discovery's high-tech hangar.

The shuttle's center engine, designated Engine 1, was installed Monday. Engine 3 was attached to the orbiter Tuesday morning, and Discovery received Engine 2 Tuesday afternoon.

All three of the reusable engines last flew on the shuttle Atlantis in November. The hydrogen-burning units are manufactured and maintained by Pratt & Whitney Rocketdyne.

Engine 1, which carries serial no. 2048, will fly for the 11th time on Discovery's upcoming flight. The engine's first launch was also aboard Discovery on the 1998 mission that returned John Glenn to space.

The most seasoned powerplant on Discovery is Engine 2, or serial no. 2044, occupying the lower-left position. About to fly for the 13th time, Discovery's Engine 2 first propelled the shuttle Endeavour into orbit on a flight to the Russian space station Mir in 1998.

When Engine 3 lights up on the launch pad, it will begin its sixth flight since entering service on the STS-116 space station assembly mission in 2006. Engine 3 is also known as serial no. 2058.

Each shuttle main engine produces 400,000 pounds of sea level thrust. When firing together, the three engines develop more than 37 million horsepower, equivalent to the output of 13 Hoover Dams.

NASA is preparing Discovery to launch on the STS-133 mission as early as September, but the flight will likely be rescheduled for late October to give crews more time to ready the shuttle's payload.

Discovery will launch the Leonardo cargo module, which is being modified for a permanent mission at the International Space Station. Leonardo has already flown seven round-trip supply runs to the complex.

STS-133 will also deliver another cargo pallet with spare parts for the space station.

These photos show the attachment of Engine 2 to the shuttle, plus other scenes around Discovery's hangar Tuesday.

Photo credit: Stephen Clark/Spaceflight Now

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