/ 



free-fall concept does have certain inherent advantages: it is simple, 

 requires no special equipment, and requires very little ship time on 

 station for installation. Conceptual development of the free-fall 

 concept has built confidence in the advantages of the free-fall concept 

 and has largely ^tspelled apprehensions regarding stability and struc- 

 tural integrity. 



Anchor Systems Developed 



Free-Fa 11-Emplaced Deadweight . Th>; f ree-fall-emplaced deadweight 

 anchor (Figure 5) is a direct descendant of the high lateral load capa- 

 city deadweight anchor designed for controlled lowering [2,3,6]. The 

 grid pattern shear keys of the controlled lowering design has been 

 changed to a radial pattern to provide easy egress for the trapped water 

 beneath the anchor during landing on the seafloor. Also, the periphery 

 of the anchor has been fitted with a device to control vortex shedding 

 to minimize pitching motion during free-fall. Otherwise, the free-fall 

 configuration is the same as the controlled lowering configuration 

 (except for being circular instead of square). The free-fall anchor has 

 been designed for a mooring line load with components of 9 MN (2 x 10 

 lb) horizontal and 9 MN (2 x 10 lb) vertical - line angle of 0.8 rad 

 (45 deg) with the horizontal - (Phase Ila loading). The free-fall 

 anchor for the Phase Ila loading conditions weighs 18 MN (A x 10 lb) in 

 seawater and is 33 m (110 ft) in diameter. Air weight for the anchor 

 would be about 31 MN (7 x 10^ lb). 



The free-fall anchors will be constructed in the dry in a shipyard 

 atmosphere. The construction material will very likely be reinforced 

 concrete with some prestressing in critical areas. The anchors will be 

 transported to the OTEC sites either on barges, or by making the anchors 

 themselves temporarily buoyant and towing them. Loading of a 31 MN (7 x 

 10 -lb) payload on a barge and transporting the payload are demonstrated 

 offshore oil-platform installation capabilities. 



Offloading of a nonbuoyant payload weighing 18 MN (4 x 10 lb) in 

 seawater has not been done before, but the feat does not appear overly 

 d-fficult. Alternatively, the anchor itself can be made to resemble a 



