THE ANALYSIS AND DESIGN OF A SHIP-CRADLE DECOUPLING SCHEME FOR DEEP SUBMERSIBLE RECOVERY AT SEA

An analysis is done of the motion of an underwater cradle for submerged recovery of the DSRV Alvin. The cradle is modeled as a three degree of freedom system with four corner springs and includes heave pitch and roll motions. The surface ship Lulu is taken as the driving force that couples energy into the cradle through the springs. Hydrodynamic damping values are found by a 64 section finite element analysis and are compared to corresponding linear approximates. Solution of the resulting equations was accomplished using a Runge-Kutta numerical integration method developed at M.I.T. The solution showed that four soft corner springs in the range of 20-50 pounds of force will substantially decrease the transmitted ship motion. Additionally, the results indicate that the pitch and roll natural frequency is higher than the heave natural frequency and consequently is the limiting design consideration. The results of the analysis are discussed and several possible approaches are considered for producing a soft spring constant while at the same time supporting the high static load of the cradle weight.

• Corporate Authors:

  Massachusetts Institute of Technology

  Department of Ocean Engineering, 77 Massachusetts Avenue
  Cambridge, MA  United States  02139
• Authors:
  • Dow, L A
• Publication Date: 1973-5

Subject/Index Terms

• TRT Terms: Catamarans; Submersibles; Tension; Wire rope
• Old TRIS Terms: Deep water
• Subject Areas: Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00048367
• Record Type: Publication
• Source Agency: Massachusetts Institute of Technology
• Report/Paper Numbers: MS Thesis
• Files: TRIS
• Created Date: Oct 31 1973 12:00AM