Re: fleet week: just-in-time nuclear electricity?

From: Strata Rose Chalup (
Date: Thu Jan 25 2001 - 17:31:39 PST

Looks like I'm misinformed this time, and that it centers around
thinking I understood what "turbo-electric" meant in the
context of submarines. All non-nuclear submarines, ie
"conventional submarines" of mainstream design use electric
motors powered by generators and augmented by battery

Over 90% of what I know about subs has been from reading the
WW2 stuff, like the first person account by the commander of
the US Wahoo. I think I just assumed, since I hadn't seen
diagrams of *modern* sub designs, that they just sub'd in
a nuke reactor for the generators.

For example:
"The submarine's propulsion system is a nuclear
turbo-electric system based on a Type K15 Pressure
Water Reactor (PWR) supplying 150 MW. The
auxiliary propulsion system is diesel electric, with
two SEMT-Pielstick 8 PA 4 v 200 SM diesels."

To me this says "electric motors, powered by
electricity produced by turbines". Note also that
things like diesel electric railway locomotives use
diesel generators to produce electricity, rather than
mechanically driving a shaft. The load characteristics
of railcars and submarines are quite similar, in that
both cases involve long-term continuous application
of torque rather than initial torque followed by high
RPM low-torque loads.

On the other hand, the Grumman ES3 pages say,
"Sole provider of U.S. Navy submarine propulsion systems
and turbine generator sets." The fact that they
name them both indicates that I should probably be
reading the French sub example as having a
turbine drive AND a set of electric turbines
that happen to produce 150MW.

To be sure, I'm rather appalled. I don't know jack about
reactor efficiencies, so I can only assume that having
direct drive turbines allows flexibility and rapid
response with more leeway than electrical overdrive,
and is thus strategically practical. There's something
akin to making a giant Babbage machine out of nanoparts
here, though. I guess if it gets the job done, oh well.

New stuff in conventional subs is getting even more
"This paper describes a modern AC propulsion plant for a submarine
of the same size, intended to undertake the same role as the OBERON'S
[DC propulsion plant].
The new propulsion plant would comprise permanent magnet type
synchronous motors controlled by Pulse width Modulated inverters."
(only the abstract available, alas)

There's a new German sub being built that's using an integrated
set of fuel cells rather than conventional batteries to augment the
onboard generation plant.

But, in summary, I was wrong about the nuke subs being electric
propelled. They DO have gensets in addition to the propulsion
plants, though, so the applicability to providing shore power
is still there-- no redesign or refit of the propulsion plant
required, just crank up the gen plant.

In the future, I may not have to be appalled anymore. :-)
Check out

"These future capabilities will be greatly facilitated by the "all-electric"
submarine. Rather than harnessing most of the nuclear reactor's output power
directly to the propulsion turbines, it will be converted to electric power on a
common bus. When there is a high propulsion demand, power can be allocated to
the propulsion train. But when propulsion demand is low, as is frequently the
case, the Commanding Officer will be able to allocate power from the common bus
to a host of functions, most of which are limited only by our imagination. High
endurance UUV's, UAV's and directed energy weapons systems immediately come to



     The USS Louisville is an American Los Angeles Class attack submarine
equipped for anti-submarine warfare, intelligence gathering, show-of-force
     missions, insertion of special forces, strike missions, mining and search
and rescue. The submarine is equipped with a vertical launch missile system with
     12 launch tubes and is armed with the land-attack version and the anti-ship
version of the Tomahawk missile, and the AGM-84 (Harpoon) anti-ship
     missile system. The submarine can lay Mobile Mark 67 and Captor Mark 60
mines. The submarine is fitted with four 21 inch torpedo tubes located
     midships together with a Mark 117 torpedo fire control system. The
submarine has the capacity for 26 torpedo tube launched weapons including
     Tomahawk missiles, Harpoon missiles and Mark 48 ADCAP torpedoes. The ship
is equipped with a 26 MW nuclear pressure water reactor, model
     GE PWR S6G, developed and supplied by General Electric. The auxiliary prop
motor by Magnatek supplies 242 kW. The life of the fuel cells is
     approximately 10 years. wrote:
> Strata Rose Chalup wrote:
> > I think "the plan" is more of a facetious attempt at humor than an
> > actual plan. But in either case, I don't believe that you're
> > correct here. A nuclear submarine does not have a "nuclear drive"
> > optimized for propulsion. It has a nuclear power plant which
> What? No turbines for me? Awwwww.
> > generates electricity to run a motor drive, period. It *is* a
> > generator. It's not steam powering or water powering any kind
> > of direct drive equipment, simply providing electricity.
> That makes zero sense technologically (you have to keep the power
> density high and hence the weight and conversion losses down, and
> one less subsystem to fail), and it doesn't seem be done in practice:
> You usually know what you're talking about, so I presume you'll
> tell us the reasons and give examples for mainstream sub designs
> which use an electrical generator for propulsion.

Strata Rose Chalup [KF6NBZ]                      strata "@"
VirtualNet Consulting                  
 ** Project Management & Architecture for ISP/ASP Systems Integration **

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