Are warships with waterjets the way of the future?

By Edward Lundquist at April 12, 2011 09:19
Filed Under: Navy News
Are warships with waterjets the way of the future?

First in a series of articles on waterjets in www.maritimepropulsion.com

 

By Edward Lundquist

 

Waterjets are not new, but their employment on surface combatants—such as the U.S. Navy’s Littoral Combat Ship (LCS)—is a relatively recent development.

 

Large waterjets for naval applications are currently made by Wartsila Lips of Cheasapeake VA and Wartsila Propulsion Drunen, Netherlands, as well as Rolls-Royce Kamewa of Kristinehamn, Sweden.  Gearboxes for waterjet applications are manufactured by Reintjes of Hamlen, Germany, as well as Renk, of Augsburg, Germany, and ZF Marine of Nottingham, UK.

 

Waterjets usually cost more up front, partly because they are made from stainless steel, which can be more expensive materials used for other propulsors.

 

What are some of the benefits?

 

  • Waterjets deliver rapid acceleration; can sustain high speeds; and can stop quickly.  
  • Waterjet-powered ships are extremely maneuverable. 
  • Waterjets can be relatively simple, because flow is constant in a single-direction; engine loading is constant, regardless of vessel speed; and waterjets do not overload the engines. 
  • Waterjets can provide precise station-keeping.
  • Waterjets have no propellers, shafts and struts, or rudders extending below the waterline, so they can be used in shallow water.  There is very little risk of damage to the propulsion gear from grounding or striking a submerged object.
  • Waterjets are fast, as the lack of appendages means less drag and can mean more speed.
  • Waterjets are basically not affected by floating debris such as ropes, nets or weeds, particularly at high speed.
  • Waterjets are reliable.  Instead of a propeller shaft that turns at different speeds, the waterjet shaft turns the pump impellor at a constant speed as opposed to a much larger screw.  Drive shafts, gear boxes and engines receive less stress.  That means the propulsion system requires less maintenance and will have a longer service life.
  • Waterjets can be quieter.  Because they have no turning props, they impart a very different acoustic signature, which may be less vulnerable detection by sonar or acoustic mines.  Lower noise and less vibration also means a more quiet and comfortable ride. 
  • Waterjets can be safer, because they have no screws or rudders that can make launch and recovery of small boats and unmanned vehicles more dangerous and difficult.  
  • Waterjets are versatile.  The same jet used in a high-speed tourist ferry can also be installed in a logistics support boat used by the UK navy.  Vessel weight, power input and required speed determine the size of jet required, not the type of ship or mission.

Comments (2) -

For some naval vessels, sure. If you need to go very fast, and spend most of your time at high speeds. So, transports like JHSV and smaller patrol and interceptor craft are already well established users. But for a warship that spends most of its underway time at speeds below 20 kts (and does not have a requirement to go beyond 30 kts to questionable LCS type spring speeds), changes speeds regularly, waterjet is not the most efficient solution, is it? Inefficiency in this regime and cost may outweigh benefits above and explain why you do not generally see waterjets on OPVs or larger naval ships.

pred |     4/20/2011 11:41:05 AM #

i want to more on waterjet propulsion engine especially the comon problem

aliyu mustapha mohammed |     4/26/2011 6:17:50 PM #

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