Unclassified 



irCURlTv CLASSIFICATION C «^ this PAGECWhen Data Hnlertid} 



20. Continued 



In addition, the reduction in the dynamic tensions in the lift Hne allows the use of smaller 

 lines for a gi\ en payload weight, greater payload capacity for a specified line size, or a greater 

 depth capability for a given line size. The concept selected for development called a "boom 

 bobber" incorporated a boom pivoted at one end and supported by a relatively soft passive 

 fluid spring. This spring decouples the payload from the motion of the support platform. 

 At-sea testing included determination of system performance for two payloads of 12,000 

 and 40,000 pounds wet weight. Cable tensions and time-correlated motions of the ship, 

 lift system, and payload were recorded. Data obtained were sufficient to prove the promise 

 of the basic concept, even though both at-sea test series ended with specific component 

 failures. 



Civil Engineering Laboratory 



DEVELOPMENT AND EVALUATION OF A MOTION 

 COMPENSATING LIFT SYSTEM FOR DEEP OCEAN 

 CONSTRUCTION (Final) by 1..W. Ilallanger, PhD and R. L. Brackett 

 TR-829 30p.illu5 December 1975 Unclassified 



1. Motion compensation 2. Load handling I, 3.1410 



A system to raise and lower loads in the deep ocean while providing lift-line tension 

 control and payload motion control was Jcsigiuil, fabricated, and tested. Design parameters 

 included a maximum wet payload weight of 40,000 pounds at a maximum operating depth of 

 6,000 feet through sea conditions state 4 when the system is mounted on an ARS-type vessel. 

 A load-handling system of this type allows soft landing of a payload on the seafloor. In addition 

 the reduction in the dynamic tensions in the lift line allows the use of smaller lines for a given 

 payload weight, greater payload capacity for a specified line size, or a greater depth capability 

 for a given line size. The concept selected for development called a "boom bobber" incorpora- 

 ted a boom pivoted at one end and supported by a relatively soft passive fluid spring. This 

 spring decouples the payload from the motion of the support platform. At-sea testing included 

 determination of system performance for two payloads of 12,000 and 40,000 pounds wet 

 weight. Cable tensions and time-correlated motions of the ship, lift system, and payload were 

 recorded. Data obtained were sufficient to prove the promise of the basic concept, even though 

 both at-sea test series ended with specific component failures. J 



I'liclassiried 



