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."