Story by Mark Sashegyi on 06/11/2019Naval Surface Warfare Center, Port Hueneme Division (NSWC PHD) recently hosted research engineers and representatives from NASA Armstrong Flight Research Center (AFRC) and the Office of Naval Research (ONR) to brainstorm partnership opportunities that could lead to improved fleet maintenance capabilities using fiber optic sensing systems (FOSS).
NSWC PHD Deputy Technical Director Vance Brahosky spoke on behalf of PHD's command mission overview and collaborative efforts to advance In-Service Engineering Agent (ISEA) of the Future initiatives.
"Fiber optics are among the most essential topics to the ISEA of the Future conversation here at PHD," said Brahosky. "And the only way we'll get through these challenges is with our sister partnerships."
NSWC PHD engineers Jerry Bobo and Regina Powell briefed attendees on the Remote Environmental and Condition Monitoring Systems (REACMS) project, a now defunct system they hope others here at PHD may want to jumpstart again with renewed interest and collaborative aid via external partnerships.
"It is designed to basically record everything," said Bobo. "We actually used fiber optic sensors that monitored temperature, relative humidity, shock and vibration, with future plans to monitor hypergolic propellant fuels, liquid detection, contamination, radiation, strain and electric and magnetic fields."
Formerly known as CAESAR (Condition and Environment Sensing and Reporting), REACMS was developed to fulfill a need to monitor high valued assets utilizing sensing technology that can be encased with live ordnance.
Powell passed around an example of a temperature fiber optic sensor and spoke on the results REACMS produced.
"We delivered a system with the most current COTS [commercial off-the-shelf] fiber optic technologies at the time," said Powell.
CAESAR was tested on NSWC PHD's Self Defense Test Ship (SDTS) before moving on to Cruiser class warships conducting Standard Missile 3 Flight Test Missions.
"REACMS allowed us to elevate confidence in real-time applications on active warships and ensure systems are ready before moving forward," added Brahosky.
REACMS, a now patented system, was designed, developed and built over a 10-year period by Bobo, Powell and Patricia Johnson, a now retired colleague. The patent was issued in January 2016.
ONR Program Manager Ignacio Perez outlined his team's efforts.
"We embedded as many sensors in an optic as possible to establish a new program which can demonstrate and identify key problems in a relatively short time," said Perez.
ONR's main proposition consists of creating a FOSS that can monitor, diagnose, and prognosticate the health of most critical components, hot spots, fatigue and damage prone areas of weapon systems in a reliable and economical way.
"We can increase sensing systems while reducing cost of maintenance, existing parts life and new materials," said Perez. "Ultimately, we are going to need endorsement letters, and PHD can help in freeing up resources."
AFRC presented the pros and cons of why they favor the lighter, smaller and easier fiber optic sensors over the bigger, heavier and harder resistive gages, and drew on the sensors in the human body as biological inspiration for their fiber optic smart structures.
"This is new technology and temperature compensation is required but there is no unique gauge factor, multiplexing is available and the installation time is much faster," said NASA FOSS Researcher Patrick Chan. "Where it would take eight hours to do proper installation of one string' sensor, the decreased installation time really gives you a lot of bang for your buck."
AFRC elaborated on Fiber Bragg Grating (FBG)an optical fiber sensor that reflects a particular wavelength and transits all othersand the two methods they use in their systems: the typical Wavelength Division Multiplexing (WDM) and NASA's unique FBG Interrogation Technique called the Optical Frequency Domain Reflectometry (OFDR).
"WDM is much simpler but has finite bandwidth limitation," said Chan. "OFDR uses high spatial density, which allows FEM (finite element method) type of data to be achieved through real-time testing."
While the cost per sensor length in an OFDR system is also dramatically reduced compared to WDM-based sensors, AFRC representatives acknowledged the use of WDM's systems.
"We use both systems depending on the needs," said Alan Parker, NASA Senior Research Engineer and Primary Developer of FOSS. "We did tests on the longevity of the sensors to see how long they functioned before they failed. The OFDR sensors we installed on the windows of Composite Crew Module in 2010 are still there."
AFRC is using a combination of WDM and OFDR on its Hybrid Fiber Optic Sensing System (HYFOSS), and by coupling both technologies on the same fiber, it allows it to record high spatial resolution along the entire length of the fiberan advantage of OFDRand high sample rates at strategic points along the fiberan advantage of WDM.
The visit concluded with AFRC taking a tour of the SDTS and the Surface Warfare Engineering Facility, which work in tandem with one another to test future fleet capabilities.
To date, partnership opportunities have resulted in AFRC working with PHD's additive manufacturing capacities to construct fiber optics parts, as well as PHD pursing a collaborative installation on their Vertical Launching System and other PHD supported programs.