Figures 2 and 3 illustrate the umbilical ties to the support ship for electrical 

 power and data acquisition. Current effort at URI is to reduce this cabling 

 requirement to a single coaxial conductor strength member over which data and 

 command signals will be passed through an FM multiplex telemetry system, and 

 power will be in the form of direct current from DOSP mounted, submersible, 

 pressure compensated batteries. A unique feature of this lightweight aluminum 

 structure is the ability to hydrostatically self-anchor by means of a pump act- 

 ing through taps in the large baseplate (Figure 1) . Only three pounds/inch 

 pressure differential distributed across this plate will give the DOSP a net 

 negative weight in water of 2,000 pounds in addition to its submerged weight of 

 400 pounds. 



Maximum sediment resistance to penetration for all four probes is less than 

 1,500 pounds (Lewis, 1971) in the sediments anticipated in the deep sea. Forces 

 larger than this are encountered in the grainy, low porosity continental shelf 

 sediments (as on the Virgin Islands plateau) and therefore the DOSP has limited 

 shallow water application. 



In terms of core disturbance parameters, the DOSP sampler has clearance ratios 

 (Rosefelder, 1967) that are 20-507o smaller than the average values of 11 ocean 

 sediment coring instruments in current use, but still somewhat larger than the 

 ideal conditions discussed by Hvorslev (1949) . 



In the present study, the data retrieved in situ were the velocity and attenu- 

 ation of compressional sound waves through the sediment and the thermal gradient 

 into the sediment to depths of 5.0 feet. Additional sensors monitor the command 

 and control functions, bottom engagement and tilt in two axes to give the oper- 

 ator an instantaneous view of DOSP electro-mechanical behavior. All of these 

 data are monitored directly in the ship's laboratory (Figure 3) and also recorded 

 on high speed magnetic tape (analog) for later analysis in the laboratory. The 

 sound source for the acoustic tests is a common automotive sparkplug which is 

 fired on command from the surface ship through a pulsed discharge capacitor 

 electronic system on the DOSP. Hydrophones are BaTi02 piezoelectric crystals 

 located in each of the remaining three probe legs. The frequency content of 

 this sparker signal is such that a fast rise time leading edge is recorded for 

 velocity determinations, and a broad band (5-50 kHz) signal is also recorded for 

 attenuation studies. 



SEA TRIALS 



Phase I Studies : March 31-April 8, 1970 



Consultation with personnel at the Caribbean Research Institute, St. Thomas, 

 prior to beginning this phase warned of coarse sediment at the Lameshur Bay 

 site, but suggested other potential "soft" sediment areas for DOSP operations. 

 Table 1 lists these sites and the sampling results using either Pheleger corers 

 (P) or grab samplers (G) . Geographically, these stations are as follows: 



P-1 near Ram's Head, St. John 



P-2 in Francis Bay, St. John 



P-3 off White Harbor, Jost Van Dyke 



P-4 in Lameshur Bay, St. John 



VII-20 



