water must be kept low. The current meter selected for this project was a 

 Richardson type instrument, Model A-lOO, manufactured by the Geodyne Corpo- 

 ration of Waltham, Massachusetts. The meter as used was capable of making 

 continuous current observations for 3% days. In the intermittent mode, 

 readings could have been made one minute out of twenty for a period of 10 

 weeks . 



The device used to release the anchor was also manufactured by the 

 Geodyne Corporation. This mechanism can be set to release after a desired 

 number of twenty minute intervals (up to a total of 140 days). When the 

 desired time interval has elapsed, an explosive squib is fired and the 

 ballast is released, allowing the package to rise to the surface. 



Flotation Package 



The key to the success of the buoy is the flotation material that 

 maintains the current meter in a vertical position while the data is being 

 gathered, and then provides the buoyant force necessary to return the 

 instruments to the surface for recovery. 



The depth for which the package was designed was 6,000 meters (9,000 psi). 

 Initially, it was desired to use containers filled with gasoline to provide 

 the necessary flotation. This was discarded for the following reasons: the 

 impossibility of carrying gasoline aboard our research vessel TRIDENT; 

 handling difficulties caused by the mass required; and the horizontal drag 

 forces that would be placed on the buoy while the equipment was on the 

 bottom. Other materials considered were: filed epoxy materials; aluminum 

 spheres; and glass spheres. The cost of a pound of flotation varies con- 

 siderably from one material to the next. The filled epoxy was $16.50 per 

 pound; the aluminum spheres $7.60 per pound; and the glass spheres $2.70 

 per pound. These costs are for the flotation material alone and do not take 

 into consideration the problems of attaching the sensor and of providing a 

 platform on which location aides can be mounted. 



Glass spheres were selected to provide the flotation. These units, 

 manufactured by Corning Glass Works, are 10 inches in diameter, with a \ 

 inch wall, and are designed for service up to 10,000 psi. The spheres were 

 specified as providing 11 3/4 pounds of buoyancy each, but subsequent in- 

 vestigation revealed the buoyancy to be 12,5 to 13.0 pounds per unit. 



The spheres were sandwiched between two aluminum discs, the resulting 

 float having the shape of a flat disc with a thickness to diameter ratio of 

 0.2. The discs were cut out in a honeycomb pattern to reduce drag and 

 weight. Support of the equipment required 109 pounds of buoyancy; thirteen 

 spheres were used, leaving an assumed net buoyant force of 44 pounds. This 

 was later revised to 57 pounds when the difference in the buoyancy of the 

 spheres was discovered. 



A pressure case containing a small radio transmitter and a flashing 

 xenon light was placed in the center of the float assembly, resulting in a 



238 



