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RESEARCH PROJECT ON THE USE OF UNDERWATER PARACHUTES TO BRING MAMMOTH SHIPS TO AN EMERGENCY HALT

The advent of super-mammoth ships and the acute increase in marine transportation, in recent years, have necessitated the development of new devices for ship manoeuvering. Improvement of the stopping ability of ships, especially, is now being taken up as one of the most vital problems. In answer to this demand, a research project of bringing mammoth ships to an emergency halt by means of underwater parachutes was attempted. The development of this project was carried out by Mitsubishi Heavy Industries, Ltd. under the support of Japan Ship's Machinery Development Association. The parachutes were made by Fujikura Parachute Co. for experimental purposes, and several tests were performed. Some boundary conditions such as the sea speed of large tankers which is about 16 knots and the maximum tension allowable on wire ropes which can be handled manually aboard a ship, the limit of which is about 30 tons, had to be considered in the designing of this braking system. Eventually, the multiple parachute system, utilizing underwater parachutes producing a resistance of 30 tons each at 16 knots was adopted. The number of parachutes are to be determined based on the size of ship and the required stopping performance. The parachute, made of durable nylon, is semi-spherical in shape with adequate slots or discharging holes for stable underwater performance. The braking underwater parachutes are subjected to extremely heavy load factor (braking force/area), about ten times that of aerial parachutes. Full scale parachute performance tests were carried out on an ore carrier, the "Santa Isabel Maru" of Mitsubishi Ore Transport Ltd., on 21st December 1969. The results proved that the underwater parachutes are effective in shortening the braking distance considerably. Moreover, it is revealed that the parachutes are effective in controlling the direction of the bow during the stopping manoeuvre of a ship. Heretofore, it was considered dangerous to apply a crash stop astern even in an emergency because it was impossible to forecast in which way the bow might turn during this operation. However, since it was revealed that this manoeuvre can be made quite safely, it can now be applied in avoiding collisions or groundings. The other effect of the parachutes made evident by the trials is the improvement of manoeuverability under low speed operation. This will be helpful in increasing the safety of navigation in narrow passages. The problems remaining are the development of an automatic dropping and lifting apparatus and a navigating system which would forecast the danger of the ship and indicate the time to order the dropping of parachutes in case of emergency.

  • Corporate Authors:

    Mitsubishi Heavy Industries Limited

    5-1 Marunouchi, 2-chome, Chiyoda-Ku
    Tokyo 100,   Japan 
  • Publication Date: 1970

Media Info

  • Features: Figures; Photos; Tables;
  • Pagination: 39 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00019260
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Nov 8 1973 12:00AM