While an ice core 3,045 meters into the ice sheet was recovered in December 2011, a Replicate Ice Coring System will re-enter the existing bore to extract additional ice related to areas of scientific interest. Using the electromechanical drill system, scientists hope to extract 250 meters of new ice cores, going down to depths of about 4,000 meters, to analyze different properties in the ice cores.
While initially following the course of the parent bore hole, the Replicate Ice Coring System will slightly alter its course to create a second path to collect ice samples. The drill of the Replicate Ice Core System uses two steering actuator sections to tilt itself in the parent borehole at a targeted trajectory. Located along the shaft of the drill, the actuators apply lateral pressure against the side of the borehole to alter the orientation of the drill head. The actuators tilt and guide the drill into the replicate borehole where ice samples are collected.
“The Replicate Ice Coring System is the first of its kind engineered with a steerable drill with the intention of retrieving additional samples of ice cores at targeted depths using an existing borehole,” notes Chris Gibson, Lead Mechanical Engineer, Ice Drilling Design and Operations (IDDO) of Space Science and Engineering Center at the University of Wisconsin-Madison who is a member of the team that engineered the drill system.
Six Macro Sensors CD Series Miniature LVDT Linear Position Sensors serve as part of the replicate actuator modules that push the drill out of the original hole at a targeted trajectory. Providing feedback on drill orientation, the AC-operated LVDT linear position sensors work as part of a closed- loop system, controlled by an onboard IC, with set points provided by an operator.
While the small compact 3/8” diameter size of Macro Sensors Miniature LVDT Linear Position Sensors is ideal for the small space of the actuator system, the sensor’s resistance to pressures up to 20 kpsi proves essential to withstand extreme forces present as the drill travels two miles deep into the ice at temperatures below -30°C. To accommodate the high pressure, the LVDT sensor case is vented to equalize pressure inside and outside the LVDT linear position sensor.
“Macro Sensors LVDT Linear Position Sensors are uniquely well suited to our application because of its pressure rating,” notes Gibson. “The drill is designed to operate at depths of 4000m (5000psi) in fluid filled bore hole.”
First production deployment of the Replicate Ice Coring System is scheduled for December with a full system test running this summer that simulates conditions a close as possible to those in the field. Module level testing at pressure and temp is also being performed.
For more information on the West Antarctica Ice Sheet (WAIS), please refer to http://waisdivide.unh.edu/. For more information on Macro Sensors Miniature AC-operated LVDTs, please refer to the web site at www.macrosensors.com/CD_375.html or contact the factory at: [email protected]
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