Ball Screw/Nut The right handed ball screw has a 25.4-mm (1-in) diameter shaft and 6.35-mm (0.25-in) pitch. The ball nut  has two tracks/return tubes with 2.5 circuits per track. The ball screw was sized to handle worst case mechanism loads with positive margin. The ball nut is not preloaded and the nut-to-screw backlash is .13- .38 mm (.005-.015 in). As stated earlier, the backlash is removed from the system when the mechanism is  in the deployed state due to the preload imparted by the stiff compression spring in the stop tower. The ball screw shaft is fabricated from 4150 alloy steel Rc 56-60 and is chrome plated to .005-.010 mm  (.0002-.0004 in) thick. The ball nut is made from AISI 1117, nitrided to Rc 56-60 and electroless nickel  coated to .005-.010 mm (.0002-.0004 in) thick. The balls have a nominal diameter of 3.96 mm (.156 in) and are made from AISI 52100 steel. The ball screw shaft grooves, nut and balls are lubricated with Braycote 601EFVB. Barrier film is applied to each end of the ball screw shaft to prevent lubricant migration. All of the critical drive components of the Deployment Mechanism are brought together by the ball nutmotor bracket. The section view in Figure 7 illustrates how the actuator, transfer gear and ball nut interface with the ball nut-motor bracket. This bracket is fabricated from Titanium 6AL-4V to reduce the CTE mismatch between the ball nut, thin section bearings and bracket. The ball nut rotates on thin  section bearings within the bracket when it is driven by the actuator through the transfer gears. The ball  screw shaft does not rotate as it advances either in the deployed or stow direction. Throughout the deployment the ball nut-motor bracket pivots on two radial ball bearings that are located in pockets machined into each side of the bracket. The ball nut-motor bracket is attached to a base bracket that is  mounted to the baseplate as shown in Figure 6.     Thin Section Bearings The thin section bearings that support the ball nut are an angular contact face-to-face pair and a single  floating radial bearing. The face-to-face style angular contact bearing pair was chosen for their ability to  withstand high axial loads. The main load path of the mechanism travels along the axis of the ball screw  and through this face-to-face bearing pair. The bearing pair was sized to handle the maximum thrust load  with positive margin. The single radial bearing is floating axially and only provides radial support to the ball nut. The load and lifetime cycle requirements make preloading this bearing unnecessary. Both the angular contact bearing pair and single radial bearing are lubricated with Braycote 601EF. The material ofthe thin section bearing races and balls is 440C stainless steel. Bellows The expandable and  collapsible bellows is used to contain the lubricant on  the ball screw shaft. The  completed assembly has acompressed length of 4.8 cm (1.9 in) and it can be  expanded to 31.5 cm (12.4  in) resulting in a 26.7-cm  (10.5-in) stroke capacity which meets the requirements of the Deployment Mechanism.  The bellows is fabricated  using pieces of .10-mm(.004-in) thick AM350  stainless steel that are hydraulically stamped into diaphragms. Once stamped, several of the diaphragms  Figure 8. Kinematic Mounts/Restraint Bolt Section View in the  Launch Configuration 442