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Automated ICBM wall thickness measurements



OBJECTIVE: This topic is to automate continuous mapping of ICBM silo steel liner wall thickness measurements. These measurements will be used to determine where corrosion has damaged the steel wall, dictating repairs. 

DESCRIPTION: The interior walls of ICBM silos are lined with mild steel plate. The steel thickness varies depending on location. The NDI equipment shall be operated from the inside of the area. Per inspection work cards, when an active water leak or bulge in the metal due to corrosion from the back side occurs, a repair to the steel plate is required. Current state of the art for measuring the wall thickness of the ICBM silos is to use hand held ultrasound thickness probes. Current technology takes 2 technicians 2 – 3 hours to cover an area of about 2 Sq. Ft. The thickness measurements may be performed while energetic materials or Electromagnetic Impulse (EMI) sensitive equipment is present. Hence, all of the measurement equipment shall meet 21M-LGM30G-12 TO specifications. The automated mapping thickness measurement device shall be able to measure on flat or curved wall surfaces (minimum radius 40”) which may be vertical and/or overhead, with obstructing ladders, piping, and geometric changes. The device shall require no human aid to stay in place or to move across the wall surface (operators would set up and initiate the device’s operation and return after the wall area thickness measurement mapping is completed). The shape of the areas requiring wall thickness measurements will vary (i.e., shapes may be in the form of squares, rectangles, oblongs, circles, and ovals) and area sizes may range from 10 square feet to 10,000 square feet. The areas where wall thickness measurements are obtained may have coatings applied to its surface (e.g. cadmium, primer, and/or paint with a thickness up to 0.030”). The device shall not damage walls in any way and shall meet energetic material and EMI safety requirements (21M-LGM30G-12 TO Specifications). The device’s operation shall not require operators to modify the walls, such as by boring fastener attachment holes or by removing paint. The device shall detect wall thickness within +/-0.025”. The data from the wall thickness measurements shall be stored in such a manner that a digital representation of the thickness of the wall area can be accessed in the future. 

PHASE I: Develop a solution that meets above requirements and conduct preliminary business case analysis (BCA) to determine implementation costs, including a return-on-investment (ROI) calculation that compares anticipated savings to expected costs. Proof-of-concept prototype(s) shall be developed to demonstrate conformance to the requirements. 

PHASE II: Proof-of-concept prototype(s) shall be refined to installation-ready article and shall undergo testing to verify and validate all requirements. This process may require multiple iterations before a final design is selected. Refine BCA/ROI based on the final design. 

PHASE III: If cost effective, transition and implement the verified and validated technology. 


1: 21M-LGM30G-12 TO

2:  Master Change Log (MCL) 21-SM80-1440, Repair Water Leaks, Launch Facility

KEYWORDS: NDI, Wall Thickness, Missile Silos 


Mark Forbes 

(801) 586-5928 

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