Table 4. Flexure Design Considerations  Location Flexure  Function Flexure Design Driver:  Stiffness Flexure Design Driver:  Stress  Single Blade Flexure  (Thick:2.00+0.05 mm) Kinematic  B.C. (5-Bar Linkage)1) Bending: LAA force required for mechanism motion 2) Axial: KaRIn Deployed 1st modeMechanism range of motion  Double Blade Flexure  (Thick:1.75+0.05 mm) 1) Bending: Assembly 2) Axial: KaRIn Deployed 1st modeMechanical environments  (and diagonal strut mass)  Hexfoil Rotary Flexure  (Thick:0.60+0.05 mm) Mechanism  Pivot Axis 1) Torsion: LAA force required for mechanism motion 2) KaRIn Deployed 1st modeMechanical environments  (and supported mass)  Radial Flexures  (Thick:0.30+0.05 mm) Thermoelastic  Distortion 1) Radial: Thermoelastic model prediction accuracy/repeatability 2) Axial: KaRIn Deployed 1st mode1) Thermal environments 2) Mechanical environments with bolt install torque added Linear Actuator Assembly Design  Key LAA design features are illustrated in Figure 8. The LAA converts commanded rotational steps from  the actuator into linear steps required by the mechanism. As the LAA is part of the primary load path, it  must react large axial, lateral, and bending loads as well as contribute to the MSA thermoelastic distortion.  To gain confidence in the design, a prototype LAA was built early in the design phase. The main objectives  with the prototype LAA were to characterize the linear step size and the effective axial instantaneous CTE  over temperature. Summarized in Figure 9 is the LAA test setup along with annotated test data graphs. The  LAA key performance metrics are summarized in Table 5.  The actuator consists of a 3-phase stepper motor, 2-stage planetary gearhead, thrust module with a hardshimmed leadscrew, and hall sensor assembly for confirming step integrity (not motor commutation).  Except for the thrust module, the actuator consists of entirely flight heritage components, which allowed for  a short procurement and development timeline. The thrust module relies on a pair of needle roller thrust  bearings to improve the axial load capability and axial stiffness within a small packaging volume. As the  LAA was only preloaded for mechanism operations, the actuator gaps in the axial direction during launch  and vibration testing. The dynamic axial stiffness was estimated as being one-half the static axial stiffness.   The telescoping cylindrical plain bearing housings provided high bending stiffness during high bending load  events, like launch or vibration testing. To estimate the bending stiffness, a non-linear contact FEM was  required. The Inner Bearing Housing was greased plated C63200 (Aluminum-Bronze). The Outer Bearing  Housing and the Leadscrew were fabricated from CRES 15-5PH condition H1025. The plain bearing  housings had tight diameter tolerances and used a 1.0 length to diameter ratio, thereby ensuring minimal  dynamic effects and minimal bending loads transferred through the actuator4. When assessing the  concentricity of the bearing housings to the leadscrew, it is advantageous to include the ACME radial play.  Table 5. Linear Actuator Assembly (LAA) Key Characteristics  Characteristic Value Notes  Total Mass 270 grams As built, includes harnessing  Interface Loads  (Approximate) Axial:  1800 N  Shear:  700 N  Moment:     400 N*m Quasi-static equivalent. Dynamic analysis used to  verify margins and make test predicts.  Dynamic Stiffness  (Approximate) Axial: 32,000 N/mm  Moment: 14,000 N*m/rad Torsional stiffness is high due to bellows.  Range of Motion 600 µm to 1000 µm As built shown. Mechanism capable of 2160+ µm.  Nominal Step Size 0.5 µm + 6% Characterize mechanism step size over ROM  4Leadscrew has a reduced diameter between ACME thread interface and actuator, thereby further  limiting the lateral and bending loads transferred through the actuator.  NASA/CP—2018-219887 32