Rapid Coring Drill

The deep drilling at WAIS Divide, Antarctica has come to a close. It took eight field seasons to prepare the remote field camp, to drill the 3,405 meter deep ice core (the longest ice core in U.S. history), and to collect the 285 meters of valuable replicate core (see story above), but we did it. On February 5, the National Science Foundation (NSF) released a press release celebrating this historic accomplishment. In case you didn't see the press release, it is available at:
http://www.nsf.gov/news/news_summ.jsp?cntn_id=126761&org=NSF&from=news

In addition to the NSF press release, The Antarctic Sun also released a great story about the success of replicate coring at WAIS Divide this season. The story is available at:
http://antarcticsun.usap.gov/science/contenthandler.cfm?id=2788

For the first time, significant innovations in ice drilling engineering are providing scientists with replicate ice cores from targeted depths and directions in the ice sheet!

The newly developed, state-of-the-art Replicate Ice Coring System was deployed in December 2012 to re-enter the 6.5-inch diameter deep borehole at WAIS Divide, Antarctica, and successfully allowed the researchers to drill through the wall of the 3,405 meter deep parent borehole and collect a total of 285 meters of additional core from five of the most interesting time periods in the WAIS Divide climate record.

The Replicate Ice Coring System is capable of retrieving additional ice cores from specific depths on the uphill side of the main (parent) borehole. The Replicate Coring technique, developed and tested by the IDDO engineers as part of the Deep Ice Sheet Coring (DISC) Drill, is a key advance, because it allows scientists to take samples from specific levels of a parent borehole without impeding the hole itself, leaving the parent borehole open for future logging of information.

The Replicate Ice Coring System collects additional ice at depths of interest by deploying into an existing borehole and then deviating from it. The drill uses two steering actuator sections to tilt itself in the parent borehole by applying sidewards force against the borehole wall. In the first step of the process, the broaching cutter head is deployed to the target depth. Using the actuators, the drill is tipped to the high ("up hill") side of the borehole to engage the cutters. Ice is removed in repeated passes of approximately 15 meters in the up-stroke. In the second step of the process, a milling head is deployed and creates a landing for the coring head. In the third step of the process, a coring head removes a 20 mm kerf and allows a 108 mm diameter core to enter the core barrel. Two meters of core are removed per trip. The coring is repeated until all of the desired replicate ice from the target depth is obtained.

The Replicate Ice Coring System builds on the existing infrastructure of the DISC Drill and thus requires substantial logistics and infrastructure support. However, the design and engineering behind the system is such that it can be scaled down for use with smaller, more agile drilling systems as well. The downhole portion of the DISC Drill, the sonde, was significantly modified to meet the requirements of steering out of the parent hole. The major components of the replicate sonde are described below.

Cable Interface Section
The existing cable interface section of the DISC Drill provides the connection to 4km of fiber optic cable.

Upper Actuator Section
The upper actuator section steers the drill, and with the anti-torque levels extended keeps the drill from spinning during cutting operations.

Instrument Section
The instrument section provides power and communications to operate the drill.

Lower Actuator Section
The lower actuator is identical to the upper actuator, but is configured with discs on the levers to provide smooth navigation.

Pump/Motor Section
The pump/motor section has a powerful pump for chip transport and contains the cutter motor.

Lower Sonde
The lower sonde includes chip barrels that collect the chips that are cut during coring, a core barrel to collect the core, and the coring head. The lower sonde can be assembled in multiple configurations to meet the needs of the different stages of the replicate coring process.

Scientists interested in using the DISC Drill in the future need to work with the Ice Drilling Program Office - Science Advisory Board (http://icedrill.org/about/sab.shtml) to formulate their plans and to ensure that their science is articulated in the Long Range Science Plan (http://icedrill.org/scientists/scientists.shtml#scienceplan), which is updated annually each spring. The current schedule for the DISC Drill is as follows:

• Dec 2012 - Jan 2013: Replicate coring at WAIS Divide, Antarctica
• Dec 2013: Disassemble and pack DISC Drill at WAIS Divide
• Nov 2014 - Jan 2015: Disassemble arch and prepare for traverse back to McMurdo Station
• Nov 2015 - Jan 2016: Traverse DISC Drill from WAIS Divide to McMurdo Station
• Feb 2016: Retrograde DISC Drill to CONUS via vessel
• May 2016: DISC Drill arrives in Madison, WI
• May 2016 - Nov 2017: Inspect, re-build, re-design and replace drill system components if necessary

Given the anticipated schedule above, the DISC Drill could be ready for shipment to the field again in late 2017. For the latest information and schedule for the DISC Drill, visit: https://icedrill.org/equipment/deep-ice-sheet-coring-drill

After review of data collected during the previous Antarctic field season and in preparation for the 2012-2013 WAIS Divide field season, IDDO has designed and fabricated a sophisticated test set-up to determine the root causes of shortcomings experienced by the Replicate Coring system. During the third quarter, IDDO was able to complete a major portion of a "sonde-in-the-borehole" test of the Replicate Coring System to determine drill sonde deflection, to verify the mechanical system analyses and to measure force at cutter head for given set points. This will assist IDDO engineers in making system modifications necessary to successfully collect replicate core during the next field season. The root cause of the intermittent instrument section faults witnessed in the field and during the system test in Madison was identified; the fix is designed and is currently being implemented. Troubleshooting of actuator motors, pressure testing of motor sections and modifications of instrument section circuit boards and LabVIEW software modifications were all successfully completed. System testing and modifications will continue into the Fourth Quarter. The large DISC Drill winch motor was also successfully repaired, rebuilt and returned to IDDO.

This season's maiden voyage of the DISC Drill's Replicate Coring capability proved to be both challenging and enlightening. While no core was obtained, IDDO engineers gained a great deal of insight into the process of creating a deviation for replicate coring. A new borehole camera proved valuable in assessing the results of the deviation effort. The video and operating data are being analyzed to aid in the modification to replicate components in order to improve chances of success during the upcoming replicate coring production season. IDDO has held several internal design reviews and, in addition, IDPO led an external review of Replicate Coring modifications held in Madison on March 27-28. Dr. George Cooper, Emeritus Professor at U.C. Berkeley and Dr. Alfred Eustes, Associate Professor at Colorado School of Mines participated as external reviewers. The effort to carefully review and analyze the recent field season experience has led to the design of tests and test fixtures needed to improve the replicate coring system.

IDDO completed the bench testing of replicate coring components prior to their being shipped to WAIS Divide. In addition, IDDO designed and built a new inclinometer control board with greater accuracy for positioning the sonde in the borehole for replicate coring, developed a bumper for the broaching cutter head to protect the borehole during the lowering and raising of the drill sonde, and designed and built a downhole camera system. IDDO conducted field-testing of the replicate coring system at WAIS Divide in January 2012, and the system will be used for production drilling at WAIS Divide during the 2012-13 field season.

For more information about the Replicate Coring System, visit: https://icedrill.org/equipment/replicate-ice-coring-system

IDDO completed fabrication and bench testing of the DISC Drill's Replicate Coring System, and plans to conduct field-testing of the system at WAIS Divide in the latter part of the 2011-2012 Antarctic field season. Production drilling with the replicate coring system at WAIS Divide is planned for the 2012- 2013 Antarctic field season.

For the latest news regarding 2011-2012 WAIS Divide field season progress, visit: http://waisdivide.unh.edu

The first-ever Replicate Ice Coring technology is progressing toward its debut in the field next year (January 2012) at WAIS Divide as IDDO engineers design, assemble, and test a system that will allow the DISC Drill to be steered and recover cores from branches deviating from the main borehole. This new technology enables gathering of additional ice core samples containing key climate information on abrupt changes, drilled from targeted depths kilometers beneath the ice surface.

The second quarter FY2011 yielded success on many fronts for IDPO and IDDO. Of particular note is the reaching of the drilling goal of 3,331 meters using the DISC Drill at WAIS Divide, Antarctica, becoming the deepest U.S. ice core ever drilled. The newly-developed Blue Ice Drill achieved and surpassed its design requirements at Taylor Valley, Antarctica for drilling large volumes of ice in a short amount of time; over 600 meters of high quality, large (9.5-inch diameter) ice core was recovered at a rate faster than anticipated. IDPO worked with the community and with IDDO to discuss implications of the science requirements for the future intermediate depth drill design, cost estimates, and potential collaborations. The most critical issues currently facing IDDO are the repair and updating of the DISC Drill after the 2010-2011 WAIS Divide field season and the development of the DISC Drill Replicate Coring System, which is scheduled for testing at WAIS Divide during the 2011-2012 Antarctic field season.

The mechanical design and testing of the Replicate Coring System is a little ahead of schedule. The electronics design is somewhat delayed due to the problems with not completing the DISC Drill motor controllers prior to the start of the 2010-11 WAIS Divide field season. This delay plus the need to correct the problems experienced with the DISC motor controllers at WAIS Divide will impact the cost of completing the design, fabrication, and testing of the electronics systems for the Replicate Coring system. However, IDDO feels confident that the Replicate Coring system will still be ready for use at WAIS Divide during the 2011-12 field season.

The community proposes to begin replicate coring at WAIS Divide during the 2011-2012 Antarctic field season. The conceptual design of the Replicate Coring System was completed in FFY2009 and substantial progress was made in FFY2010 in translating the replicate coring concept into a detailed mechanical design. During the coming year the design of the lower sonde (core and screen barrels and cutting head/cutters) will be completed as will the sensor and control electronics design and software development. Assembly and "bench" testing of the actuators and lower sonde are also scheduled for completion. The entire system will be integrated and tested to the extent possible before its shipment to WAIS Divide for use during the 2011-2012 field season.

IDDO suffered a set-back in its development of replacements for outdated motor control modules for the DISC Drill when it was discovered during testing that the design was inadequate and the electronic circuits would have to be re-designed, prototyped, tested, and manufactured. This problem, along with the need to extensively modify drill system sheaves, the need to modify the azimuth measurement system and the resignation of an electrical engineer put a heavy workload on the one remaining electrical engineer. IDDO has contracted an electrical engineer to assist in the tasks.

The unexpected issues with the DISC Drill Development also affected the DISC Drill Replicate Coring System Development Project as resources planned for the project are needed to complete work on the DISC Drill before the 2010-2011 WAIS Divide field season. However, IDDO is confident that the replicate coring system will be ready for first use at WAIS Divide during the 2011-2012 field season.

Replicate coring
In the second quarter FFY2010, design of the "actuated" anti-torques, which will allow the drill to be steered, was completed. IDDO ordered components for the prototype model of the anti-torque actuators and test fixture. A control program was written to allow testing of the mechanical system, and initial testing began. Replicate coring capability for the DISC Drill will be ready beginning with the 2011/12 Antarctic field season.

A new drill for intermediate depth drilling
A white paper justifying the need for an intermediate drill is in preparation by Eric Saltzman, Chair of SAB, and Eric Steig, ICWG representative. Because the new NZ drill (designed from the Danish Hans Tausen drill) may provide an excellent prototype for this drill, detailed science requirements will be developed with the broader community by IDPO-IDDO after results of NZ drill testing at NEEM this coming summer. IDDO engineer Tanner Kuhl will be at NEEM to witness the testing of the NZ drill. This will give an excellent first-person assessment of aspects of the drill that should be replicated and identification of possible problem areas. Opportunities for funding acquisition of a drill are being explored.