RADAR AND VISUAL 

 DENTIFICATION 

 SPAR BUOY 



Figure A-l. — An Iceberg Tagging Scheme Using a Floating-Line Technique. 



Coast Guard, he used a much heavier line (24mm 

 polypropylene). Since the experiment was con- 

 ducted at nearly 60°N, the icebergs could be ex- 

 pected to be more stable. The array was tracked 

 using the NTMBUS-6 satellite system, but no 

 attempt was made to verify whether the iceberg 

 remained with the transmitter. The transmitter 

 was not recovered. 



The development of an instrument package 

 which can be attached to an iceberg requires so- 

 lutions to three problems; rolling, melting and 

 calving. In 1975, the Coast Guard Research and 

 Development Center tried a new approach to 

 tethering an instrument package to a berg by 

 using a large steel dart with a trailing line which 

 attached to a floating instrument package. This 

 solves the problem of rolling and melting, but 

 not calving. It is not likely that any system can 

 survive calving, since the anchoring piece of ice 

 would drift away rapidly from the iceberg itself, 

 or any conceivable line would be parted by the 

 weight of several hundred tons of ice falling 

 from the side of the berg. 



The dart was designed by applying the rela- 

 tively new branch of dynamics called terra- 



dynamics, which is the study of the forces acting 

 on a body in relative motion to solid materials. 

 After several trials, which included about two 

 dozen drops, the present design was arrived at. 

 The requirements were that it be easy to ship and 

 assemble, cheap to build, and have stability and 

 penetration for low altitude drops. The dart was 

 manufactured from 5.72 cm cold rolled steel and 

 2.54 cm steel rod (Figures T-2 and A-3). It 

 weighs 13.64 kg and has a 46 cm tail assembly 

 of extruded high density polyethylene (Figure 

 A-4). 



Using the equations developed by Young 

 (1972), it was possible to calculate the approxi- 

 mate depth of penetration of a steel dart in 

 glacial ice. The empirical equation was: 



D=0.0117 KSN VWA (V-30.48) 

 for impact velocities greater than 61 m/s. Where : 

 D = Depth of penetration, m 

 K = Scale factor, dimensionless 

 S = Index of penetrability, dimensionless 

 N = Nose performance coefficient, dimensionless 

 W = Dart weight, kg 

 A = Cross sectional area, cm 2 

 V= Impact velocity, m/s 



A-2 



