page_title: Ice drilling
section_title: Cable-suspended electromechanical drills
hierarchical_section_title: Ice drilling / Cable-suspended electromechanical drills
caption_attribution_description: English: Schematic of cable-suspended ice core drilling system. Redrawn from Talalay, Pavel G. (2016). Mechanical Ice Drilling Technology. Beijing: Springer. ISBN 978-7-116-09172-6. p. 110.
context_page_description: Ice drilling allows scientists studying glaciers and ice sheets to gain access to what is beneath the ice, to take measurements along the interior of the ice, and to retrieve samples. Instruments can be placed in the drilled holes to record temperature, pressure, speed, direction of movement, and for other scientific research, such as neutrino detection.
  Many different methods have been used since 1840, when the first scientific ice drilling expedition attempted to drill through the Unteraargletscher in the Alps. Two early methods were percussion, in which the ice is fractured and pulverized, and rotary drilling, a method often used in mineral exploration for rock drilling. In the 1940s, thermal drills began to be used; these drills melt the ice by heating the drill. Drills that use jets of hot water or steam to bore through ice soon followed. A growing interest in ice cores, used for palaeoclimatological research, led to ice coring drills being developed in the 1950s and 1960s, and there are now many different coring drills in use.
context_section_description: A cable-suspended drill has a downhole system, known as a sonde, to drill the hole.  The sonde is connected to the surface by an armoured cable, which provides power and enables the drill to be winched in and out of the hole.  Electromechanical (EM) cable-suspended drills have a cutting head, with blades that shave the ice as they rotate, like a carpenter's plane.  The depth of penetration of the cut is adjusted by a device called a shoe, which is part of the cutting head.  The ice cuttings are stored in a chamber in the sonde, either in the core barrel, above the core, or in a separate chamber, further up the drill.
  The cuttings can be transported by auger flights or by fluid circulation.  Drills that rely on auger flights and which are not designed to work in a fluid-filled hole are limited to depths at which borehole closure is not a problem, so these are known as shallow drills.  Deeper holes have to be drilled with drilling fluid, but whereas circulation in a rotary drill takes the fluid all the way down and then up the borehole, cable-suspended drills only need to circulate the fluid from the drill head up to the cuttings chamber.  This is known as bottom-hole circulation.
  The upper part of the sonde has an antitorque system, which most commonly consists of three or four leaf-springs that press out against the borehole walls.  Sharp edges on the leaf springs catch in the walls and provide the necessary resistance to prevent this part of the drill from rotating. At the point where the cable connects to the sonde, most drills include a slip ring, to allow the drill to rotate independently of the cable.  This is to prevent torque damage to the cable if the anti-torque system fails.  Coring drills may also have a weight that can be used as a hammer to assist in breaking the core, and a chamber for any instrumentation or sensors needed.
  At the bottom of the sonde is the cutting head, and above this is the core barrel, with auger flights around it on shallow drills, and typically an outer barrel around that, usually with internal vertical ribs or some other way of providing additional impetus to the upward-bound cuttings on the flights.  If there is a separate chip chamber it will be above the core barrel.  The motor, with suitable gearing, is also above the core barrel.
  Shallow drills can retrieve cores up to 300–350 m deep, but core quality is much improved if drilling fluid is present, so some shallow drills have been designed to work in wet holes.  Tests reported in 2014 showed that wet drilling, with the top of the drilling fluid no deeper than 250 m, would maintain good core quality.
  Drilling fluids are necessary for drilling deep holes, so the cable-suspended drills that are used for these projects use a pump to provide fluid circulation, in order to remove the cuttings from the bit.  A few drills designed for use with drilling fluid also have auger flights on the inner barrel.  As with shallow drills, the cuttings are stored in a chamber above the core.  The circulation can be in either direction: down the inside of the drill string, and up between the core barrel and the borehole wall, or in the reverse direction, which has become the favoured approach in drill design as it gives better cuttings removal for a lower flow rate.  Drills capable of reaching depths over 1500 m are known as deep drilling systems; they have generally similar designs to the intermediate systems that can drill from 400 m to 1500 m, but must have heavier and more robust systems such as winches, and have longer drills and larger drilling shelters.  Core diameters for these drills have varied from 50 mm to 132 mm, and the core length from as short as 0.35 m up to 6 m.  A common design feature of these deep drills is that they can be tipped to the horizontal to make it easier to remove the core and the cuttings.  This reduces the required height of the mast, but requires a deep slot to be cut into the ice, to make room for the sonde to swing up.
  The first cable-suspended electromechanical drill was invented by Armais Arutunoff for use in min
caption: Schematic of cable-suspended ice core drilling system[107]
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