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originally posted by: seasonal
a reply to: jimmyx
At 8:16 is a shot of the shuttle going over the cam, and it sounds to me like it is powered.
Auxiliary Power Units
The auxiliary power unit is a hydrazine-fueled, turbine-driven power unit that generates mechanical shaft power to drive a hydraulic pump that produces pressure for the orbiter's hydraulic system. There are three separate APUs, three hydraulic pumps and three hydraulic systems.
Each auxiliary power unit and its fuel system are located in the aft fuselage of the orbiter. They are identical but independent systems that are not interconnected. Each APU fuel system supplies storable liquid hydrazine fuel to its respective fuel pump, gas generator valve module and gas generator, which decomposes the fuel through catalytic action. The resultant hot gas drives a two-stage turbine. The turbine exhaust flow returns over the exterior of the gas generator, cooling it, and is then directed overboard through an exhaust duct at the upper portion of the aft fuselage near the vertical stabilizer. The turbine assembly provides mechanical power through a shaft to drive reduction gears in the gearbox. The gearbox drives a fuel pump, a hydraulic pump and a lube oil pump. The hydraulic pump supplies pressure to the hydraulic system. The fuel pump increases the fuel pressure at its outlet to sustain pressurized fuel to the gas generator valve module and gas generator. The lube oil system supplies lubricant to the gearbox reduction gears and uses the reduction gears as scavenge pumps to supply lube oil to the inlet of the lube oil pump to increase the pressure of the lube oil system.