Determining Root Causes of Mysterious Hardware Failures  using High Resolution CT Scanning  Michael R. Johnson* Abstract During testing of actuators for flight programs, failures have occurred that required closure with an  understanding of the root cause of the failure. Some actuators intended for a Mars mission called InSight  exhibited intermittent changes of the winding resistance of the motors during temperature changes was  extremely baffling. It was critical to determine the cause of the intermittent characteristic because the  actuators were residual flight hardware from a previous program and the company that provided the motors  was no longer in business. Using an X-Ray Computed-Tomography (CT) method that produces a threedimensional computer model of the item, the exact source of the intermittent failure was determined and  completely understood – at dimensions of less than 20 microns. In another case, after the completion of an  actuator’s life-test-to-failure, inspection was required to determine the source of the failure. The size of the  actuator (10-mm diameter) required destructive means to get to the interior of the actuator for inspection,  risking the loss of the source of the failure. Using CT imaging, the source of the failure was determined.  Introduction  Computed Tomography X-Ray inspection is a process that uses hundreds to thousands of X-ray images to  assemble a finely detailed three-dimensional computer model of the object under inspection. By taking each  image from a different location and angle around the perimeter of the object, a three-dimensional volumetric  model can be created from the individual scans. This model can then be viewed, rotated, sectioned, and  magnified in the same way as a computer design model of the object. By rotating, sectioning, and  magnifying the scanned model, details of the actual assembled components within the assembly can be  detected and measured. These measurements and views allow the illumination of anomalies within the  assembly that may otherwise be undetectable.  Two anomaly investigations are discussed that demonstrate the power of the X-Ray Computed  Tomography inspection method. One case allowed the detection of failure points that were not visible even  though the hardware could be safely disassembled and inspected directly. The second case allowed the  determination of the failure cause with a hardware assembly that could not be disassembled without  destructive means. The destructive disassembly caused significant concern that the root cause would be  lost in the process of disassembly. The use of the Computed Tomography method allowed the  determination of the failure source and in-situ measurements of the effects of the failure could be made to  fully demonstrate the extent of the failure cause.  The two cases described are:  1. Winding failures of brushed motors for the Instrument Deployment Arm on the Insight Project 2. Brushless Actuator Life Test failure of a 10-mm-diameter device for the Mars 2020 project *Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California Proceedings of the 44th Aerospace Mechanisms Symposium, Jet Propulsion Laboratory, May 16-18, 2018 NASA/CP—2018-219887 307