N222-121 TITLE: Compact Sensor for Non-Destructive Propellant Mechanical Property Evaluation

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Materials / Processes; Sensors

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop a compact sensor capable of operating safely in an energetic environment that collects data that can be used to determine the mechanical state of solid rocket propellant in a non-destructive manner. The sensor will take data that can be used to infer the mechanical state of solid rocket motor propellant and be used in the analysis of propellant grain integrity.

DESCRIPTION: Solid rocket motors employed by the Navy use propellants that must withstand all of the structural loads the motors are exposed to during transport, storage, stowage, and operation. The motors are designed to meet/exceed these load requirements. However, age and environmental exposure can alter the response of the propellant to these structural loads. The Navy has a need for a compact sensor or a suite of sensors that can collect data that can be used to infer the mechanical state of solid rocket motor propellant in a non-destructive manner. Such a sensor would be used to inspect the propellant of solid rocket motor assemblies in a rapid fashion. Understanding the mechanical state of the solid rocket motor propellant allows for a better evaluation of the health of the propellant and provide greater fidelity in aging trend evaluations. In addition to the sensor(s), an insertion system that can place the sensor at different locations on the propellant surface of a solid rocket motor system will need to be designed. The needed R&D is the miniaturization of the sensor head (on the order of inches) and the development of an insertion system compatible with solid rocket motor assemblies currently deployed by the Navy.

A sensor or a sensor suite that can perform the required measurements will address the difficulty of non-destructively evaluating the mechanical state of the propellant grain while having limited access to the interior of the solid rocket motor assembly. This technology will avoid the current need to disassemble the solid rocket motors and avoid all associated costs with disassembly and reassembly. The technology will minimize or eliminate (preferred) the need to attach the inspection equipment to the solid rocket motor. All of these features will allow measurements to be taken on substantially more available solid rocket motor assets as opposed to the current limited number of assets assigned to the monitoring program.

This SBIR topic is focused on the development of a compact, highly mobile sensor that can collect the data needed to determine fundamental (gross or bulk) material properties, such as the modulus for elastic and elastic-plastic deformation. The propellant is a highly filled elastomer that contains organic and inorganic solids, plasticizers, and stabilizers, held together by a polymeric binder. The proposed approach may employ a miniature version of an indentation testing technique or leverage a completely different method. Proposed methods should minimize the need for attachment to the solid rocket motor. The proposed sensor would move to the correct measurement position. The sensor then measures the resisting force being applied by the material on the contact head. In this mode, the contact head is moved to fixed required depth. In another mode, the contact head is moved at a constant rate while measuring the resisting force. The sensor should meet low power, low voltage, and the Navy’s HERO (Hazards of Electromagnetic Radiation to Ordnance) requirements for on-shore use [Ref 6]. The sensor should be capable of being maneuvered through the confined area of a nozzle and be used in the interior of a solid rocket motor. The sensor system must be capable of being calibrated prior to use. The insertion system must be capable of placing the sensor at multiple locations, up to several meters into the solid rocket motor or preferably a mobile system capable of moving to the correct location for measurement. The insertion system should be simple to install and minimize the number of personnel and amount of support equipment needed for measurements. The sensor and insertion assembly must be capable of intermittent usage for a period of ten years.

PHASE I: Develop a technical concept for a propellant mechanical property sensor. Proposed design concepts should be completed during Phase I. Laboratory-scale demonstrations to verify the proposed sensor concept(s) should be completed. Modeling should be completed to verify proposed concept(s) can meet size/volume constraints while providing the correct data. The laboratory testing and modeling must be satisfactorily completed to transition from Phase I to Phase II. Identify risks to the technical approach and develop/evaluate plans to mitigate those risks for Phase II. Laboratory-scale demonstrations to verify the proposed insertion system should be completed. The Phase I Option, if exercised, will include the initial design specification and capabilities description to build a prototype solution in Phase II. Coordinate with Navy SBIR liaisons on key technical requirements data to be measured, size of the sensor, size of the insertion system, application method, power, and data storage/transmission needs.

PHASE II: Design and develop a prototype of the mechanical property sensor based on the concept(s) from Phase I. Ensure the design has the ability to collect data that can be used to measure, at a minimum, the data needed to calculate the initial modulus and the relaxation modulus. Ensure the design is sized such that it can pass through the throat of a solid rocket motor nozzle and fit within the bore of the motor. Ensure the design is capable of performing the measurements at multiple locations in a repeatable manner. Ensure the insertion system is capable of moving the sensor to the desired location. Complete testing of the sensor prototype to validate operation and feasibility. Design the testing to emulate the installation, sensing, data collecting/storage, and removal. Test material compatibility to ensure survivability and compatibility with solid rocket propellant during the inspection process.

PHASE III DUAL USE APPLICATIONS: Update the sensor based on Phase II efforts. Support the development of an instruction manual for use. Manufacture an updated prototype and demonstrate use on an identified asset that is considered representative. Provide the necessary support for certification and qualification of the system for deployment and use at fleet facilities and/or facilities where fleet assets are located.

This technology has the potential to be used commercially in any industry that has a need for mechanical property monitoring of elastic / elastic-plastic materials in areas of high hazards.

REFERENCES:

1. Champagne, J.W. "An Instrumented Indentation Technique for Characterization of the Mechanical Behavior of Solid Propellants." JANNAF 36th Structures and Mechanical Behavior Subcommittee Meeting, March 2004. jannaf.org
2. Standard Test Method for Rubber Property – Durometer Hardness, ASTM 2240.
3. Oliver, W. and Pharr, G. "An Improved Technique for Determining Hardness and Elastic Modulus Using Load and Displacement Sensing Indentation Experiments." J. Mater. Res. Vol. 7, No 6 (1992).
4. Lu, H., Wand, B. and Huang, G. "Measurement of Complex Creep Compliance Using Nanoindentation." Proceedings of the Society for Experimental Mechanics Annual Conference 2003.
5. Lee, E. and Radok, J. "The Contact Problem for Viscoelastic Bodies." J. Appl. Mech. 27 1960.
6. NAVSEA OP 3565/NAVAIR 16-1-529 (REV. 16) (VOL. 2), TECHNICAL MANUAL: ELECTROMAGNETIC RADIATION HAZARDS - HAZARDS TO ORDNANCE (HERO) (01 JUN 2007). http://everyspec.com/USN/NAVSEA/NAVSEA_OP3565_NAVAIR_16-1-529_R16-V2_8137/

KEYWORDS: Relaxometry; 1.1 Propellants; Non-Destructive Measurement; Mobile Sensor; High Elongation Propellants; Propellant Mechanical Properties

** TOPIC Q&A **

Questions answered 05/31/22 Q1. Have standard ultrasonic non-destructive testing methods been considered for this problem? If so, are there issues precluding their use? A1. As of today, ultrasonic testing methods have not been considered. The Indentation method mentioned in the topic write up, provides estimate of tensile and relaxation modulus. If other methods like ultrasonic measures are able to provide this information, we are open to those approaches as well.