October 11, 2016

The future Columbia class SSBN(X)'s reactor may be as quiet as SSKs on Battery

How should this diagram be altered to represent a Heat Exchange Reactor with Electric Drive? Diagram courtesy Bright Hub Engineering.

One of the quieting/stealth features on the future Columbia class SSBN(X) is a possible heat exchanger quiet mode in its proposed S1B reactor. This reactor is also called Columbia Program Element PE0603570N/Project 3219 (see page 32).

Apparently the S8G reactor on the current Ohio SSBN already uses a heat exchanger. I think it logical that the heat exchanger aspect will be carried over to the future Columbia.

Minimising moving parts contributes to quiet mode. Such a quiet mode may ideally be available when future Columbia's are operating at their (about 5 knots?) on station cruising speed. 

The heat exchanger tip comes from Josh in Comments on 29/9/16 12:23 AM: 

"And important attribute of the S8G fitted to Ohios is that it is a natural circulation reactor (at least at low power), relatively revolutionary at the time. The core is placed low and the heat exchanger placed high in the primary coolant loop such that the hot coolant rises to the exchanger then falls back down the other side of the loop once cooled off without the use of a pump. This eliminates an entire type of noise from plant, at the cost of size and weight apparently. The wider hull of a boomer makes this more practical to do in an SSBN than an SSN. Its not clear if the practice carried through to the Seawolf or Virginia's reactors; it might well not have been for size reasons or because more cost effective means of quieting coolant pumps became available (turbopumps, electrical systems that remove the 'snap' noise of pump engagement, etc).

Its also worth noting that any SSBN would spend its patrol at 5knts unless it was fired upon. The pump jet arrangement would only be advantageous getting to station. The Russians likely have much more reason to worry about being tracked during transit than the Americans due to their [Russian] base geography and possibility of USN SSNs off their SSBN bases at any given moment. The USN keeps boats deployed off Russian coasts at much more often than the reverse case, even during the cold war. I suspect its quite the rarity for an Akula [SSN] to appear off Maine [Kings Bay, Georgia SSBN Base] or [Bangor in Washington state] these days."
Other features contributing to the Columbia's quietness/stealth will be electic drive, X-plane rudders and pump jets - on these see this 2013 reference and a major briefing to Congress August 18, 2016 reference. 

If all of these features are in the Columbia's and perhap future US SSN(X)s they may make them quieter than SSKs on battery mode.

Submarine Matters' mentions of Columbia class stealth are at articles dated September 28, 2016


Anonymous said...

Hi Pete

I heard bottleneck of nuclear turbo-electric propulsion system is complexity of the system and limitation of motor which reduces speed [1]. USA seems to give priority to non-detectability than speed for SSBN(X).

Cutting edge conventional submarines such TYPE 212A [2] and Soryu [3] adopt PMSM (Permanent Magnet Synchronous Motor) [5] with various merits such as easiness in upsizing, convinience in maintenance, significant noise reduction and high efficiency [1,4]. But, the application of PMSM for nuclear submarine is yet reported.

[1]SHIPS OF THE WORLD, 2016, November, No848, page 84 “Propulsion System of Modern Submarine” by Masakazu Kaji, the Ex-commander of Submarine Fleet and the Vice-admiral.
[5] DC (Direct Current) propulsion motor system is adopted for most of conventional submarines because conversion of DC/AC (Alternative Current) between batteries and propulsion motor is not needed. Rotation speed of rotor is easily adjusted by voltage change. DC propulsion motor has drawbacks such as difficulty in upsizing, complicity of maintenance and noise caused by brush. To overcome these drawbacks, PMSM propulsion motor is developed for the said submarines. Rotation speed of PMSM rotor is adjusted by VVVF(Variable Voltage Variable Frequency) or AVAF(Adjustable Voltage Adjustable Frequency) inverter.


Peter Coates said...

Hi S

Yes it is not totally certain the SSBN(X) will use electric drive/PMSM. Perhaps using it on the SSBN(X) will take 10 more years of development.

Interesting the electric drive on the German Type 212A https://de.wikipedia.org/wiki/U-Boot-Klasse_212_A#Antrieb "can be controlled continuously without switching noise and voltage spikes through the entire rev range, producing low electromagnetic emissions and little waste heat. An active noise cancellation reduces low frequency sound."



Anonymous said...

Hello Pete,

thanks for your really interesting blog!
I have been reading it for a while, and learned a lot about submarine technology.

As for this article: at first I thought that the "electric drive" would be for "creep speeds". Is it really intended to pass all those horsepowers (normally transmitted through a gearbox) through a generator and an electric motor? What is the size of these components in the 10-15-20 MW range? Do electric motors of this size exist for submarine use at all?

Also, I do not think that an SSN/SSBN/SSGN with an electric drive could ever be as quiet as an SSK on batteries.
For the nuclear boats you would have the reactor running (at low load), the steam turbine running (at low load), the generator running and the electric motor running.
For the SSK, only the electric motor would be running.
More running equipment for the nuclear boat means it cannot be as quiet as the SSK.

Regards: FMate

Anonymous said...

Hi Pete

Power of propulsion motor is as follows [1].

Germany: 2MW for TYPE 212 (2MW PSMS x1), 4 MW for TYPE 214 (2MW PSMS x 2), 8MW for SEA German solution (2MW PSMS x4)

France: 3.3 MW for Scorpene, 7MW for Brazilian nuclear submarine program (possible SEA French Solution)

Japan: 5.9 MW for Soryu (large PSMS+ small PSMS for silent operation at low speed). As 5.7MW (=2.85MW+2.85MW) system is already adopted for Pre-Soryu (Oyashio-class), 10-11 MW is likely to be achievable by combination of two large PSMSs

Size of motor for German submarine (212, 214) is 4-5m in diameter as shown in pictures of Siemens Permasyn™ Motor [2, 3]. Diameter of motor for Soryu may be a bit bigger than German submarine.

According to ex-commonder of submarine fleet Kobayashi, lack of high power motor enforces the use of gear system in nuclear subs.

[1]http://corporate.siemens.com.au/content/dam/internet/siemens-com-au/root/aunz-defence-solutions/apdr-october-2015-issue-future-submarine.pdf (page 44, “Main Motor”)
[2] ibid (page 44, Figure 2)
[3]http://www.industry.siemens.com/verticals/global/en/marine/submarines/propulsion/permasyn/pages/default.aspx (picture)


Peter Coates said...

Hi FMate [at 18/10/17 6:32 AM] on electric drive for nuclear subs.

The US DoD would be conducting classified studies (shore based test stands?) on noise/efficiency issues for electric drive for future Columbia SSBNs. DoD would be looking at curves against requirements.

Also the classified characteristics (eg. noise) of the new reactor portion of the system would be relevant.

All this leaves we overt media in ignorance until DoD decides to release more details justifying electric drive.



Peter Coates said...

Thanks Anonymous [at 4/11/17 2:16 AM] on comparing MW propulsion between different submarine types.

This is very useful data for a Table I can publish as an article next week.

I'm assuming/hoping Naval Group might opt for 4 or 5 x MTU 4000s for Shortfin?



Anonymous said...

Hi Pete

[4/11/17 2:16 AM Part II]
As development of submarine diesel generator is very expensive, private sector achieves high power generation by combination of off-the-shelf small diesels to reduce cost. 4 or 6 diesels are needed for large submarine. Public sector such as Japan MoD can achieve high power generation by combination of original large diesels, and reduces number of diesels and length of submarine.

Scorpene equips with 4 MTUs, and I think Shortfin equips with 6 MTUs.

I also think Japan SEA1000 equips with 4 KAWASAKIs. SEA1000 without huge LOx tanks is 6-8m longer than AIP Soryu with 2 KAWASAKIs. This elongation is not explained only by improvement of endureance. Improvement of charging rate of LIBs by additional 2 KAWASAKIs seems to be rational explanation.

For 2000 tonnes submarine with 2MW+2MW motors, one motor is used for surveillance at low speed. But, 300 kW of output is enough for surveillance and use of 2 MW motor is not efficient in energetics. Though optimal arrangement of motor is unequal combination of 300kW and 3.7MW motors, the equal arrangement (2MW + 2MW) is used because it cheaper than the unequal arrangement.