Novel Real-Time Nondestructive Technology for Chemical and Structural Health Management of Solid Rocket Propellants
Authors: Daoud Sami , J. Villeburn Michal , D. Bailey Kevin , Kinloch Gordon 
Published: March 2024

An innovative prognostics and chemical health management (CHM) technique was developed, for quantifying and characterizing health status of a CL-01 composite solid rocket propellant of tactical rocket motors. The technique is a cutting-edge real-time nondestructive technology approach which utilizes Near Infrared (NIR) spectra (M. Blanco, and I. Villarroya, 2002) emitted by microPHAZIRTM NIR miniature handheld platform, developed by Thermo Fisher Scientific. Benchtop high-performance liquid chromatography (HPLC) and ion chromatography (IC) were utilized as baseline reference techniques for correlation to TM microPHAZIR NIR measurements.To build a quantitative calibration model, near infrared spectra were acquired for twenty freshly manufactured mixes of CL-01 propellant formulae, which were iterated using a D-Optimal full-factorial design of experiment (DOE). Four-hundred eighty measurements were recorded and analyzed using Partial Least Squares (PLS) regression analysis for model building and method development (Schreyer, 2012). NIR results were correlated to spectra, which were produced using HPLC and IC reference techniques and were determined to be in precise agreement. All recorded measurements that were performed using microPHAZIRTM handheld platform were successfully validated with HPLC and IC measurements. An algorithm was developed for microPHAZIRTM NIR thus qualifying the platform as a real-time nondestructive test (NDT)/ nondestructive evaluation (NDE) tool for quantification of primary chemical constituents of CL-01 composite solid rocket propellant. Primary chemical constituents of CL-01 comprise a binder, oxidizer, plasticiser, and antioxidant/stabilizer.Data sets for Shore-A hardness of each of the twenty DOE mixes were collected and used to calculate elastic modulus, tensile strength and percent strain. Calculated results conformed to specification requirements for CL-01 solid rocket propellant, henceforth confirming use of Shore A hardness as a real-time nondestructive test technique for validation of structural health of a solid rocket propellant. This teaming effort between Raytheon Missile Systems (RMS), United Kingdom Ministry of Defence (UK MoD), Alliant Techsystems Launch systems (ATK LS), and Thermo Fisher Scientific demonstrated outstanding ability to utilize miniature cutting-edge technology to perform real- time NDT of CL-01 composite solid rocket propellant without generating chemical waste and residue and to ameliorate RMS technology base to capture incipient failures before the fact. The new technique will further be adapted for use to measure primary chemical constituents of other solid rocket propellants, liquid propellants, and composite explosives. The new technique will significantly reduce costs associated with surveillance and service life extension programs (SLEPs), which are often destructive and requires use of lengthy and expensive test techniques described in North Atlantic Treaty Organization (NATO) Standardization Agreement (ST ANAG)-4170 and Allied Ordnance Publication (AOP)-7 manuals.