Micron Optics announced the installation of one of their state of the art optical interrogation systems on one of the nation’s most famous monuments, Mount Rushmore. The Rock Block Monitoring System (RBMS) will provide the National Park Service with critical information about shifts in the rock system which makes up the Mount Rushmore National Monument. The RBMS was installed in partnership with Respec Inc. and the Mount Rushmore Rope Access Team and is composed of one Micron Optics sm125 Optical Sensing Interrogator and 36 sensors.

For more information, see the full press release or read the case study on the website.

Orion is the Crew Exploration Vehicle that was created for NASA’s Constellation project. At first glance, Constellation is reminiscent of the Apollo system, with the crew riding atop a large launch vehicle. But Orion is meant for longer missions to the moon and rendezvous with asteroids. So while Apollo and Constellation might look similar, the engineering tasks represent a new set of challenges. See more here www.nasa.gov/

Fiber optic strain sensors are being used to verify the design and performance of a critical part of the Orion Capsule - the heat shield. Recent drop tests at the US Army’s Aberdeen Proving Grounds included 41 drops and various angles and velocities. A Micron Optics sm130-700 Optical Sensing Interrogator was the primary measurement tool gathering data from dozens of FBG strain gages welded to the interior surface of the heat shield.

Chris Lynn, NASA’s lead engineer for these tests, had this to say to the Micron Optics team following the tests “The Crew Module water landing drop tests were very successful, so much so that we completed a total of 41 drops when we only planned for 23 in the original test matrix. The fiber optic strain sensors provided by Micron Optics held up extremely well during testing - we didn’t lose a single sensor during the duration of testing. We greatly appreciate MOI’s support during all phases of work, without the great work the testing would not have been a success. Thanks again for the great work!”

Tom Graver
Vice President -Optical Sensing Group

The Deep Underground Science and Engineering Laboratory (http://www.dusel.org) at Homestake gold mine in South Dakota is posing technical challenges far ahead of the actual experiments to be performed there. In particular, the mine itself must be prepared to ensure a safe as well as scientifically interesting work environment. Research in many scientific disciplines is being undertaken at this facility including Astrophysics, Geoscience, Microbiology and investigations of future technologies such as CO2 Sequestration.

Why perform experiments 8,000 feet underground? Because the mass of rock shields astrophysics experiments from cosmic interference. If you want to learn more about pioneering work in neutrino detection, you’ll find fascinating details here: www.bnl.gov/bnlweb/raydavis/research.htm.

Professor Herb Wang of the University of Wisconsin leads a team of geoscientists and engineers (GEOX) who are relying on fiber optic sensing systems to measure movement of the rock structures. The GEOX research is sponsored by the Geomechanics Program of the National Science Foundation. GEOX’s charter is clear: “The objective of GEOXTM is to understand the mechanical response of rock masses to loading for spatial scales from centimeters to kilometers and for time scales from milliseconds to decades by installing the world’s largest and deepest underground network of fiber optic strain and temperature sensors and tiltmeters.” One advantage of the fiber optic sensing technology is that not only is science being performed but safety and structural health monitoring of these very large structures can be realized also. The focus of the safety assurance work is to understand rock-mass deformation resulting from dewatering of the old mine passages followed by excavation of giant caverns that will house the experiments.

For example, meter long FBG based strain gages are mounted in threes to sense rock shifts in X, Y and Z axes in critical locations. Just last week, the GEOX team was working with hydraulic jacks in the mine to load the rock mass and study its response.

JoAnn Gage, a PhD candidate at the University of Wisconsin and key member of the GEOX team, has invented special “strain strips” that combine six strain and six temperature sensors and are grouted in boreholes in the rock.

The motivation for using fiber optic measurement techniques, rather than conventional electrical gages, is that fiber optic methods (including fiber Bragg gratings, Raman, and Brillioun) can address the wide range of measurement scales, i.e., centimeters to kilometers and milliseconds to decades.

Herb Wang sums it up nicely. “Fiber-optic sensors have the versatility and stability to extend our understanding of how rock masses deform. We were successful in this work because we received extensive technical support from Alan Turner and the entire Micron Optics organization.”

Alan Turner,
Micron Optics Sales

ETA: If you want to read more on SUSEL, you can purchase “Fiber Optic Strain And Temperature Monitoring In Crystalline Rock At the Sanford Underground Science And Engineering Laboratory (SUSEL), Lead, South Dakota” by Dr. Gage, et al. which was presented at the 44th U.S. Rock Mechanics Symposium and 5th U.S.-Canada Rock Mechanics Symposium in 2010.

In September, I posted a brief about work that Applied Geomechanics (AGI) had done with the Federal Aviation Administration (FAA) to measure strain in pavement. One of the sensor types evaluated by AGI and the FAA was produced by Monitor Optics. To create this novel sensor, Monitor Optics has developed a pultrusion process that coats and protects a FBG sensor arrays so that they can be directly embedded in asphalt and concrete pavements either during construction or long after.

You can learn more about such an application on our website here. It highlights an installation in Australia that sought to quantify risks associated with potential mine subsidence under a highway. An update is here. In this case study, see how the data helped highway and mine officials identify the root cause of a road buckling event. Was it the result of thermal expansion or an indication of an imminent mine collapse? Without the data from the fiber optic sensors, the answer would not have been so clear.