Simulation of Space Shuttle Gear Performance

Abstract

Scuffing damage was found on Space Shuttle Power Drive Unit gears for the Rudder Speed Brake. Scuffing simulation tests rule out a predicted scuffing scenario. Scuff initiation is caused by tooth interference under unique transient high speed and torque conditions. Simulation tests for subsequent operation following a scuffing event show limited wear much less than the thickness of the gear case hardened layer.

New Scuffing Test Methods for the Determination of the Scuffing Resistance of Coated Gears

“…Photographs of the components of the rudder speed brake power drive unit of a space shuttle: a) pinion and ring gear of the power drive unit, b) damaged pinion tooth [4] From the above example, it is absolutely apparent that the prevention of scuffing is still an important challenge, even in the high-tech sector.…”

“…Photographs of failures of the gear teeth flanks due to scuffing: a) "non-symmetric" scuffing observed in gear service, resulting from the incorrect distribution of load along the tooth [3], b) scuffing on the flank of the test gear due to poor extreme-pressure (EP) properties of the tested gear oil during the gear scuffing experiments performed by the authors Another example of scuffing of gears concerns the rudder speed brake power drive unit of a space shuttle, observed during its inspection after grounding [4]. Figure 2 a) shows the pinion and ring gear of the power drive unit of the space shuttle.…”