Space Shuttle Main Engine - Components - Gimbal

Gimbal

Each engine is installed with a gimbal bearing, a universal ball and socket joint which is bolted to the launch vehicle by its upper flange and to the engine by its lower flange. It represents the thrust interface between the engine and the launch vehicle, supporting 7,480 lb (3,390 kg) of engine weight and withstanding over 500,000 lb (230,000 kg) of thrust. As well as providing a means to attach the engine to the launch vehicle, the gimbal bearing allows the engine to be pivoted (or 'gimballed') around two axes of freedom with a range of ±10.5°. This motion allows the engine's thrust vector to be altered, thus steering the vehicle into the correct orientation. The bearing assembly is approximately 290 by 360 mm (11 by 14 in), has a mass of 105 lb (48 kg), and is made of titanium alloy.

The low-pressure oxygen and low-pressure fuel turbopumps were mounted 180 degrees apart on the orbiter's aft fuselage thrust structure. The lines from the low-pressure turbopumps to the high-pressure turbopumps contain flexible bellows that enable the low-pressure turbopumps to remain stationary while the rest of the engine is gimbaled for thrust vector control, and also to prevent damage to the pumps when loads were applied to them. The liquid hydrogen line from the LPFTP to the HPFTP is insulated to prevent the formation of liquid air.