Summer 2013

Innovative Drill, Instrumentation and Hose Reel for the Askaryan Radio Array

The ARA hot water drill is the first drill of its type to be used at the South Pole. With all the success behind the IceCube drill, it might seem simple to use the same design and build a similar but smaller hot water drill for ARA.  Yet the requirements that had to be met prompted engineers to design, develop and create an entirely new drill unlike any other at the South Pole. These requirements included that the hole had to be at least six inches in diameter, usable to a 200 meter depth, and the hole must be dry.

If these requirements were not enough to challenge the engineers, the drill also has to be mobile and must be small enough to fit on a plane. Although the real challenge was how to design a drill that uses hot water and leaves the hole dry. “Drilling and pumping the water out in a serialized fashion takes too long and leaves a hole full of water that will freeze back. The unique thing is that we combined the pump out process with the drilling process by integrating a pump into the drill head” said Engineer Terry Benson. He explained that they ran a hose cable bundle that coupled two hoses, one supply and one return, which is also needed to allow the drilling and pumping to occur simultaneously. This saves time.

The ARA drill head.

When working with water at the South Pole there is a race against time with freeze back of the water in the hole. “It is a huge challenge, in some cases freezing back at a rate of 28 millimeters per hour on the diameter” Terry Benson explained. By pumping the water out of the hole, freeze back is eliminated. The drill also recovers not only the drill water but also the melt water, which closes the loop and gives a surplus of water. This water surplus is opposite of the typical case for hot water drills that maintain a water-filled hole, where water is continually lost to make up for the density difference between ice and water.

The drill itself when operating creates a traveling water column at the bottom of the hole. It supplies a high speed water jet ten meters below the pump that opens the initial hole. Then the water flows back up the hole and develops the diameter. By the time the water and pump meet, the hole is of sufficient size and the water is pumped back to the surface. “Drilling a hole takes about 6 hours, and the hole-to-hole turnover is about 10 hours with 5 drillers” he said.

Now they had to take these ideas and make them happen. Not only did the team had to build the new drill heads and custom hose and cable bundle, but they also had to build a hose reel, and everything had to be compact enough to fit on a plane and on the drill train at the Pole. In order for the hose reel to fit on the plane, it was necessary to build it so it could tilt on itself at a 45% angle.

Instrumentation that was designed for this drill was another reason for its success. The instrument box, developed jointly with James Roth (University of Delaware), provided key system information and allowed the information to be fed directly to the drillers through a wireless network. Drillers had personal digital devices that they could carry in their pockets for critical information updates as drilling took place. This assisted the drill team in being able to monitor the drill's activities closely.

Lead Drill Engineer Terry Benson makes clear that this was not a one man show. PSL led the effort with Engineers Jeffrey Cherwinka and Dan Wenman, Technicians Darrell Hamilton, Jonathan Heise, along with CADD Specialist Amy Pagac and the talented team in the Shop. The group from ARA consisted of Dave Pernic, Jim Haugen, Ken Walker, Andrew Laundrie and Matt Newcomb, along with James Roth from University of Delaware and Thomas Meures, Université Libre de Bruxelles. According to Terry, answering the requirements led to innovative thinking, design and mobility for the new ARA drill and its instrumentation, however the synergism of the group is what gave it success.

 

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