ABSTRACT 



A controlled-depth cable-towed depressor designed to house 

 a conductivity, temperature, depth (CTD) instrument system is 

 described. Design considerations are discussed, and the results 

 of basin and preliminary at-sea evaluations conducted to ensure 

 hydrodynamic performance are presented. The evaluations indi- 

 cate that the basic design objectives were satisfied. Detailed 

 hydrodynamic performance predictions as well as operation and 

 maintenance guidelines are included in Appendices. 



ADMINISTRATIVE INFORMATION 

 This work was funded by Naval Oceanographic Office Project Order N6230678P085023 

 of 29 March 1978, David W. Taylor Naval Ship Research and Development Center Work 

 Unit 1548-801. 



INTRODUCTION 



The David W. Taylor Naval Ship Research and Development Center (DTNSRDC) was 

 requested by the Naval Oceanographic Office (NAVOCEANO) to provide a controlled- 

 depth towed depressor to house a conductivity, temperture, and depth (CTD) instrument 

 system. In addition to sensors located at the depressor, provision for two sets of 

 remote sensors to be located on the towcable were requested. 



This report discusses design considerations and calculations to establish 

 towing configurations and depressor wing forces; describes the resulting hardware 

 and control electronics; and summarizes the results of basin and preliminary at-sea 

 experiments conducted to examine towing performance of the depressor. Predicted 

 performance curves as well as information concerning operation and maintenance of 

 the equipment also are given. 



DESIGN CONSIDERATIONS 



The depressor is required to maintain selected depths to 200 m at speeds up 

 to 10 knots. During steady towing, depth excursions no greater than + 150 mm are 

 desired, although excursions up to + 300 mm are acceptable. Cyclic depth control 

 of the depressor at frequencies from near zero to 0.2 Hz is required. Cycle ampli- 

 tudes up to 7.6 m are desired at frequencies below 0.01 Hz; at frequencies above 0.01 

 Hz, cycle amplitudes up to 600 mm are desired. 



Instrument space for the control electronics should be located in an area sep- 

 arated from the CTD electronics to avoid interference. An internal space 152 mm 



