Question: Why is the 16 SLBM Columbia Class SSBN-X larger than a 24 SLBM Ohio? (see Table way below. Displacement and Beam is larger).
The larger the submarine the smaller the influence of its weapons
on displacement and length.
The displacement of the future SSBN-X's 8 fewer SLBMs (16) than the Ohio’s 24 and dimensions
for 8 fewer tubes doesn’t mean the SSBN-X is 33% less in displacement/length/beam.
- Beam always needs to be the same or greater to accommodate the length of the
SLBMs.
- The Ohio’s 24 SLBMs were a break in the decades old pattern (page 36) of 16 SLBMs.
- The most pessimistic predictions (of many opposing Russian SSBNs) didn't
materialise. (see comparative Table below).
- The USN must be calculating that threat, stealth and budget means 12 x 16 SLBM
SSBNs is adequate for the 2030-2080 SSBN-X era.
- But more Common Missile Compartment (CMC) quad-packs and more MIRVs
per SLBM can always be retrofitted if need be.
The SSBN-X crew (at 155) remains the same because all the requirements needed to
maintain the submarine and its SLBM payload involve the same crew specialities,
damage control and other fixtures for 16 as they do for 24. There may even be a need
for a few more crew in, say 22 years time, to improve stealth.
- the task of safely operating the reactor requires many crew no matter how many missiles are carried
- the task of safely operating the reactor requires many crew no matter how many missiles are carried
An inbuilt capacity to absorb improvements and stealth
over the 42 year life of SSBN-X involves room to grow into spaces left empty in
the hull. Much of this is expanding the computer power by adding more memory
and other processing on spare racks in the combat system database. See “must
be fitted with the most up-to-date capabilities and stealth to ensure they are
survivable throughout their full 40-year life span.”(# below), So more electronics and memory for future active stealth and combat system upgrades may take up much extra space-displacement.
Perhaps more decoys the size of HWT sized UUVs (if the 4 torpedo tubes are retained?).
The tubes for SSBN-X's SLBMs are the same 87-inch
diameter as on the Ohio-class, but are a foot longer - leaving some margin for a future missile design. This explains the need for
a space/displacement increasing Beam of 43 feet compared to the Ohio’s Beam of
42 feet.
The new reactor may be very slightly heavier and larger, with more 90+% HEU for the longer life between refuels (stretched from the Ohio's 19 year mid-life, to being sufficient for the SSBN-X’s whole 42 year service life).
SSBN-X and Ohio class
Comparison Table
Measure/Replacement or Ohio
|
Ohio Replacement, SSBN-X, Columbia class
|
Ohio class
|
Number of SLBMs
|
16***
In Common
Missile Compartment (CMC) quad packs #
|
24*
But just 20 after 2018*
|
Launch tubes
|
Same 87
inches SLBM launch tubes ***
|
Same 87
inches SLBM launch tubes ***
|
Length
|
560 feet ***
|
560 feet ***
|
Beam
|
43 feet ***
|
42 feet ***
|
Displacement
|
Larger, 20,815
tons “(as of August 2014)” submerged ***
|
Smaller, 18,750 tons submerged ***
|
Crews Blue/Gold
|
2 x 155 #
|
2 x 155
|
Years between HEU refueling
|
42
(service life) ***
|
About 19 *
|
Drive, propulsion
|
electric-drive propulsion train ***
pump jet, X-plane rudder#
|
mechanical-drive propulsion train*** bare propeller,
cruciform-H rudder
|
UK Successor and Vanguard classes
|
On UK
Successor class 8 x Trident IIs, In Common Missile Compartment (CMC) quad packs # UK made warheads **
|
UK
Vanguard class carry 16
x Trident IIs, UK made warheads**
|
* page 3 Ronald O'Rourke’s Navy Columbia Class (Ohio Replacement) Ballistic Missile Submarine (SSBN[X]) Program: Background and Issues for Congress, of August 18, 2016 CRS 7-5700 www.crs.gov R41129 https://news.usni.org/wp-content/uploads/2016/08/R41129-1.pdf (5 MB PDF)
** page 4 https://news.usni.org/wp-content/uploads/2016/08/R41129-1.pdf
** page 4 https://news.usni.org/wp-content/uploads/2016/08/R41129-1.pdf
Pete
There is comment at Breaking Defence that by designing the reactor core for the full 40+ year life of the submarine ( the current Virginia's reactor is designed for the 30 year life) that means that 12 submarines can do the work of the current 14 without the long overhaul for refueling the reactor
ReplyDeletehttp://breakingdefense.com/2015/01/new-reactor-cores-key-to-ohio-replacement-subs/
The other main new technology is using turbo-electric drive instead of the existing geared turbines. They tried two previous 'electric boats' with USS Tulibee in 1960 and USS Glenard Lipscombe ( similar in displacement to Shortfin Barracuda!) in 1974 but the results werent satisfactory. Diesel boats are of course electric drive to run off batteries.
USS Narwhal had a unique reactor-direct drive setup which wasnt repeated either ( the turbine was a large diameter slow turning)en.wikipedia.org/wiki/S5G_reactor
The construction cost per boat is supposed to be withing a cap set by Congress of around US $5 bill. But that doesnt include new technology development , especially the reactor and detailed design and first of class costs.
www.wired.com/2013/01/secret-sub-design/
This report gives an outline of how the CMC or quad pack common missile compartment will be built integrally with the hull around it.
"The tubes are the same 87-inch diameter vessels as the current Trident II D5 launchers on the Ohio-class, but are a foot longer — leaving some margin for a future missile design."
warisboring.com/americas-next-missile-submarine-will-be-silent-huge-and-live-longer-than-you-edd02eb8c7a2#
"“If you look at the overall length of the ship, the length of the missile compartment is smaller,” Lennon said. “But it’s distributed pretty much equally — the increase — forward and aft. Very little of that has to do with electric drive. It’s really to do with the other capabilities we’ve had to put into the ship in order to meet the mission needs.”
The new reactor and electric drive dont seem to be the main reason for the increase in size.
Some of the detail in the table could have different numbers
ReplyDelete"The U.S. Navy today operates 18 Ohio-class submarines -- 14 of which carry the Trident nuclear missile, and four of which have been modified to carry conventionally armed long-range
"The CMC design includes an increased diameter of the launch tubes from 2.21m (current) to 3.04m"
while others say
"The tubes are the same 87-inch diameter vessels as the current Trident II D5 launchers on the Ohio-class, but are a foot longer — leaving some margin for a future missile design."
http://ukarmedforcescommentary.blogspot.co.nz/p/successor-submarine-trident.html
warisboring.com/americas-next-missile-submarine-will-be-silent-huge-and-live-longer-than-you-edd02eb8c7a2#
Its difficult to confirm more official sources for the CMC dimensions
Hi Ztec
ReplyDeleteThanks for those extra details. Because of the proliferation of secondary sources, which frequently use old and contradictory info, I've intentionally combed through (and used) the most official, most recent report I know of: Ronald O'Rourke Specialist in Naval Affairs,
Navy Ohio Replacement (SSBN[X]) Ballistic Missile Submarine Program: Background and Issues for Congress, May 27, 2016 https://www.fas.org/sgp/crs/weapons/R41129.pdf (5 MB PDF)
Then the Table cites source for piece of info.
Using that Page 8 "The SSBN(X) is to be equipped with an electric-drive propulsion train, as
opposed to the mechanical-drive propulsion train used on other Navy
submarines. The electric-drive system is expected to be quieter (i.e., stealthier)
than a mechanical-drive system.20"
Thanks for ""The tubes are the same 87-inch diameter vessels as the current Trident II D5 launchers on the Ohio-class, but are a foot longer — leaving some margin for a future missile design."
http://ukarmedforcescommentary.blogspot.co.nz/p/successor-submarine-trident.html"
This helps explain why SSBN-X's Beam will be 43 feet instead of Ohio's 42 feet. (Page 8, https://www.fas.org/sgp/crs/weapons/R41129.pdf )
Yes I think more electronics and memory for future active stealth and combat system upgrades may take up much extra space-displacement.
Regards
Pete
Hi again Ztev
ReplyDeleteThanks. I've added to the text:
The tubes for SSBN-X's SLBMs are the same 87-inch diameter as on the Ohio-class, but are a foot longer [ https://warisboring.com/americas-next-missile-submarine-will-be-silent-huge-and-live-longer-than-you-edd02eb8c7a2#.j7gqn4au2 ] — leaving some margin for a future missile design. This explains the need for a space/displacement increasing Beam of 43 feet compared to the Ohio’s Beam of 42 feet.
Regards
Pete
Relevant to the SHORTFIN is http://nationalinterest.org/blog/the-buzz/the-us-navy-getting-ready-build-the-most-stealth-submarine-17549 where it says:
ReplyDelete"The “X”-shaped stern [rudder] will restore maneuverability to submarines; as submarine designs progressed from using a propeller to using a propulsor [pump jet] to improve quieting, submarines lost some surface maneuverability, Navy officials explained. "
The Electric Drive to be fitted on the Ohio Replacement, Columbia class, SSBN(X) is just one of the new generational nuclear powered subs moving in the direction of the quietness of conventional subs (SSKs) See http://nationalinterest.org/blog/the-buzz/the-us-navy-getting-ready-build-the-most-stealth-submarine-17549 . Unclear whether the Columbia class will:
1. feature an X-rudder alone or
2. an X-rudder and a pump jet?
The Barracuda SSN also reputely has Electric Drive for the same quietness reason.
Pete
Better late than never: While not discussed publicly, I think one reason for the larger hull than an Ohio class is to accommodate advances in machinery quieting.
ReplyDeleteFor decades machery in submarines has been isolated from the hull via "rafting". The early designs were no more than rubber elastomeric mounts between the machinery/raft/hull. But now I think they've gone to "active" machinery rafting. (i.e. the mounting between the machinery/raft/hull is electro-hydraulic with feed-back?).
The rafts themselves are probably designed to lessen resonant frequencies and would need to be more massive to to achieve this. All of this additional weight may need to have a large hull displacement.
Just conjecture on my part, my time on subs was a while ago....
I understand the need for a 43 foot hull diameter.
ReplyDeleteI do not understand the desire to have the vessel longer when the missile compartment is so very much smaller.
There are vague references to "future growth and expansion" of technology (paraphrased), but a larger vessel to carry a smaller load appears to be illogical. With the missile compartment only 2/3rd the size of the Ohio class, and a stated desire for increased maneuverability, one would presumably look to a length reduction of about 62 feet.
That reduction in length would increase maneuverability, maintain the same buoyancy effect, and reduce the tonnage to 18,510 submerged.
As a submariner veteran.
I understand the need for the next generation boomer.
As a taxpayer, I find myself livid at the cost and the stated requirement that the Columbia class "The SSBN(X) will have a beam (i.e., diameter) of 43 feet, compared to 42 feet
on the Ohio-class design, and a length of 560 feet, the same as that of the Ohio class
design."
As a requirement, that appears to be a desire to achieve the "Bigger" part of "bigger and better". The price-tag is already huge, and simply wanting something to be bigger for the sake of being bigger appears ludicrous and only increases cost.
This is a reference to the recently released Congressional Research Service (read: GAO) document "Navy Columbia Class (Ohio Replacement), Ballistic Missile Submarine (SSBN[X])
Program: Background and Issues for Congress
Ronald O'Rourke, Specialist in Naval Affairs, May 12, 2017
Better doesn't always mandate bigger. In fact, as we compare the Seawolf and Virginia class programs, we learned that the 95% solution of the Virginia class is able to accomplish everything a fast attack sub needed, but without the Seawolf's colossal price tag. Yes, I do know that the Virginia class benefitted from the research that went into the 'Wolf.
Why are we Hell-bent to make another Seawolf or Zumwalt scale error in judgement?
Note: numbers based on estimates of the existing missile compartment accounting for 1/3rd of hell length (about 186.7 feet), and that section now being 1/3rd less in size due to carrying 1/3rd less weaponry (16 vs. 24), resulting in a reduction of about 62 feet from total length.
Hi Richard K
ReplyDeleteI think you're on the right track.
As you can see in the article I've listed the official reasons for not reducing the size of the Columbia class.
BUT submarine building is also run as a business, which almost always boils down to builder corporations persuading the Pentagon and broader US politicians (with factories in Districts) bigger is "better". Bigger is always more expensive - which means more money, jobs, factories and votes in US House of Represenative Districts.
Arms manufacturers generally want more revenue and profit per unit built. So executive careers, workers pay and shareholder dividends cannot remain the same (or less) but must increase.
Increased size and price per unit also helps shield the building corporation from reductions in units ordered by the Pentagon or
even the Australian Navy, eg. growth of Australia's existing generation of 6 sumarines to 12 new subs, in the hope that after the expected 4 are cancelled (due to high costs) 8 new subs will eventually be built.
Strategic opponents, like China, also help the unit justification by building ever better, larger and more capable Chinese SSKs, SSNs and SSBNs.
To be cynical indeed helps.
Cheers
Pete
Hi again Richard K
ReplyDeleteSpeaking of the revenue sub builders will make from the Columbia class SSBNs "Washington Business Journal, August 9, 2017 reveals https://www.bizjournals.com/washington/news/2017/08/09/general-dynamics-sees-75b-in-possible-revenue-with.html :
"Falls Church-based General Dynamics Corp. (NYSE: GD) is on track to finish the design and development of the Navy's massive Columbia class submarine and is looking at $75 billion in possible revenue for the lifespan of the project, according to CEO Phebe Novakovic..."
Pete
Or for less money, convert Virginia class into boomers with a slight limo stretching. And save the taxpayer 75 billion. We'd probably only need 12 units.
ReplyDeleteSuch as what was done with the George Washington: they took a Skipjack class, specifically the first Scorpion hull, and added a missile compartment. Another hull was then ordered to replace the Washinton/Scorpion.
DeleteHi spikedpsycho (re your comment way back June 24, 2018)
ReplyDeleteA Virginia hull for SSBN is likely unviable as the diameter/beam would need to be increased from Virginia's 10m to Columbia's 13m to accommodate the Trident D5s and maybe even taller follow-ons.
Also the Columbia will house a probably quieter reactor and electric drive than Virginia class's.
Cheers
Pete
Hi again Richard K (August 11, 2019)
ReplyDeleteYes the George Washington was likely a compromise of speed in building/launching by placing a missile compartment plug in a Skipjack class (the Scorpion's hull).
On "compromise" - only 5 George Washington's were built (from 1958) with a quick overlap to 5 Ethan Allen class SSBN (building from 1959). This suggests a rush and that the US (the Rickover political effect and all) had money to burn in beating any perceived Russian missile gap.
--------------------------------------------------------
Returning to why the Columbia's (with only 16 Trident silos) will have a slightly longer hull length than the Ohios (with 24 Trident silos).
I think the reactor portion of Columbia's length will increase - with the incorporation of the future Columbia's whole of life (40 year?) no need to refuel reactor. This reactor is also meant to be quieter than Ohio's.
Also the the incorporation of quieter electric drive may require more length than the Ohio's mechanical-geared drive.
Regards
Pete