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2004-04-16 Home Front: WoT

Contracts awarded for Navy's DD(X) destroyer

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Posted by Super Hose 2004-04-16 01:25|| || Front Page|| [11126 views since 2007-05-07] Top

#1 The author of this story is clearly not an industry insider. He doesn't seem very adept at technical writing. Super Hose, you must've been in the Navy, right? I ask because you always submit articles about Navy stuff.

Posted by Kentucky Beef 2004-04-16 1:56:41 AM|| 2004-04-16 1:56:41 AM|| Front Page Top

#2 ..Is the lead ship still set to be USS Zumwalt? IIRC, there was a LOT of heartburn when Clinton annoucned that one.

Mike

Posted by Mike Kozlowski 2004-04-16 2:21:10 AM|| 2004-04-16 2:21:10 AM|| Front Page Top

#3 Does the electrical power system imply they are going to put directed energy weapons on it?

Posted by Phil B 2004-04-16 2:23:48 AM|| 2004-04-16 2:23:48 AM|| Front Page Top

#4 ..One other thought - the original USS Lexington (CV-2) and USS Saratoga (CV-3) - were turbo-electric drive - extremely advanced for that time. Lex was lost early in WWII, but when Sara got into prolonged combat, it was discovered that the TE drive systems tended to crash - terminally - from shock damage. She was out of the war for far too long with damage to the TE system that required a trip home to the US every time. Hoping they've worked out the problems instead of reinventing a wheel with one flat side.

Mike

Posted by Mike Kozlowski 2004-04-16 2:29:02 AM|| 2004-04-16 2:29:02 AM|| Front Page Top

#5 Kentucky Beef, I was in the Navy a number of years ago when roughly a third of the ships had conventional steam plants (the others ships/boats being driven by nuclear steam, large diesel engines, or gas turbines.) Like many Ensigns after commissioning I was sent to Surface Warfare Officer School in Newport. Like most I also went through Steam Engineering Officer of the Watch school as a follow-on school aka a per diem buster (kept you in school at the same location for long enough that the school could be considered a permanent duty station = no per diem and like it.)

Even then while I was learning how to operate a caveman ship and dreaming of one day being allowed to sail on a spiffy gas-turbine ship, the school instructors were already talking about the next generation ship beyond that - the turbo-electric.

The way I understood the concept was that you could use a power plant of steam, reactor, turbine or diesel without having the main driver (reduction gear) coupled to the propeller through an inconveniently long shaft that in some cases ran half the length of the ship through bearings in the nether regions of the shift. The idea was instead to generate mechanical power with the turbine or diesel but then convert the power into electrical form and transmit the power through cables to the aft (see I can still do the lingo) to be converted again into mechanical power to a much shorter shaft connected more directly to the propeller(s) - some ships have only one making them a bear to maneuver.

This provides a large reduction in heavy shafting and also eliminates the need for a seperate number of electrical generators to provide the ship with electrical power.

It's a cool idea that I hope works successfully.

Posted by Super Hose 2004-04-16 3:05:21 AM|| 2004-04-16 3:05:21 AM|| Front Page Top

#6 The idea was instead to generate mechanical power with the turbine or diesel but then convert the power into electrical form

You mean, like conventional diesel-electric locomotives? I'm surprised this hasn't been implemented earlier. It worked wonders for the railroads.

Posted by Rafael 2004-04-16 5:06:13 AM|| 2004-04-16 5:06:13 AM|| Front Page Top

#7 Concur that diesel electric did in fact work wonders for the railroads. Electric drive for ships has many advantages but the problem is the motors. The most powerful locomotive I have ever heard of puts 10,000 hp to the wheels. The DDX is supposed to have two 50,000 hp motors. The limiting factor has been motor technology. Looks like that problem is solved.

Posted by Bruce 2004-04-16 7:00:02 AM|| 2004-04-16 7:00:02 AM|| Front Page Top

#8 Oddly the motors were developed for subs.... but were still too large for a sub hull.

Posted by Shipman 2004-04-16 8:46:36 AM|| 2004-04-16 8:46:36 AM|| Front Page Top

#9 GM has a proto-type car that sounds like it uses similer tech.
The car uses a fuel cell to generate electricity that is transmitted to 4 motors mounted close to the wheels.This elminates the need for an internal combustion engine and the attendant transmision,drivelines and differentials this translates into a huge wieght savings and less maintinance due to fewer moving parts.The car is also supposed to trap and reuse energy generated from breaking(don't know how that is supposed to work).

Posted by raptor 2004-04-16 9:10:03 AM|| 2004-04-16 9:10:03 AM|| Front Page Top

#10 The linked article is...interesting, to say the least. It would seem either that the reporter was badly misinformed, or that there's a cover story here. Here's why:

A fundamental principle of physics is that every time you convert energy from one form to another, you lose some. On a ship or sub, the electricity to run a large e-drive is usually generated by steam turbines--which is how a standard mechanical drive works too. Thus there's no *efficiency improvement* here. Certainly there can be advantages from eliminating a long propshaft, or in being able to turn two props from a single generator if needed, but better *drive efficiency* is highly unlikely.

Noise isn't a concern for a destroyer, so that's not the explanation. One possible reason--as some have suggested--could be that the vessel will be equipped with energy weapons.

Posted by sf 2004-04-16 12:27:38 PM|| 2004-04-16 12:27:38 PM|| Front Page Top

#11 One other thought - the original USS Lexington (CV-2) and USS Saratoga (CV-3) - were turbo-electric drive - extremely advanced for that time. Lex was lost early in WWII, but when Sara got into prolonged combat, it was discovered that the TE drive systems tended to crash - terminally - from shock damage.

There are a few advantages to the TE. The engines themselves can be located in separate areas of the ship. Technically, they can even be placed in the superstructure. There is technology to reduce and prevent shock damage.

In any case, the cost savings alone from not having main reduction gears will be significant.

Posted by Pappy 2004-04-16 12:34:13 PM|| 2004-04-16 12:34:13 PM|| Front Page Top

#12 SF, Pappy is correct - the reduction gear on the USS Dahlgren (DDG-43), my first ship was a large as my current 2500 square foot house. Don't get too caught up with the idea of energy losses in the conversion from mechanical to electrical and then back to mechanical and the cable losses. The energy losses from a high speed turbine through the reduction gear will be greater because the shaft turns so much slower than the turbine. The HP turbine is essentially an aircraft engine screaming along at some ridiculous RPM's. To convert the high speed mechanical energy from the turbine into the slow mechanical energy of the shaft is many many stages that include heat loss at every stage. The reduction gear sits on a gigantic oil pan that is continuously cooled by seawater flow from the main circulation pump, the biggest pump on the ship.
The reduction gear is incredibly complex and expensive. On a gas turbine ship if a turbine goes bad the turbine can be craned out of the ship and a replacement craned back in and installed. I have never heard of a main reduction gear being damaged but I don't see how the gear would have been disassembled on my DDG. I project that such repairs would have taken six months in the shipyard.
As for the shaft, I would estimate that the component was a 4 foot diameter solid steel that ran 200 feet. It's size relative to the size of the ship could be effectively illustrated by taking a look at the drive train underneath an SUV with four-wheel drive.
I would expect that the diesels or turbines would still be placed low in the ship and on the centerline. Any other placement of heavy machinery usually results in the ship becoming a barf-a-matron for the crew.

Did I do OK, Pappy? I still love ships but the technology is passing me by. This topic might best be dalt with by Steven Den Beste.

Posted by Super Hose 2004-04-16 1:07:18 PM|| 2004-04-16 1:07:18 PM|| Front Page Top

#13 Did I do OK, Pappy? I still love ships but the technology is passing me by. This topic might best be dalt with by Steven Den Beste.

BZ, SH. I My last ship was a Spruance about twelve years ago, but I try to keep up. One of the curses of having been a 'snipe'.

The turbines can be swapped out pretty quickly pierside, but the shafts and MRG have to wait until the ship goes into drydock. From what I was told, the navy actually leases the Main Reduction Gears.

I agree on the machinery placement being a bitch on stability and ship-riding (my first job as a JO was DCA on an MSO), but relocating machinery from its traditional side-by side engineroom arrangement was one of the things that was being pushed during the electric-drive program.

Posted by Pappy 2004-04-16 11:44:58 PM|| 2004-04-16 11:44:58 PM|| Front Page Top

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