The Columbia will also have a reactor that won't need refueling for its service life. That might be resulting in more displacement too. Also there is something a bit funny to mention. The Columbias will accept women for service, unlike Ohios. Having both genders serve on ships increase their displacement. Because it requires the duplication of a lot of living spaces and amenities. Displacement is a lot more significant for subs than surface vessels because it directly determines their submerged volume. Therefore submarine branches are among the last branches to accept women.
How many times do I need to write this one???
In shipbuilding displacement is the
equivalent of the
weight of the ship. It's not the mass of the entire ship only the mass of the water that it displaces when empty or under different loads. The heavier the load the more its hull submerges and the more water it displaces. This determines the amount of mass that any given hull can carry and not sink below the water's surface (also considering sea state). No other measure of mass of the ship is necessary which is why this traditional measure is still used.
This means that having more displacement is not a problem. Having more mass than maximum displacement is the problem.
For submarines specifically more
volume is a problem because volume determines the hull's ability to resist pressure, create drag, sustain pressure differentials etc.
Soviet submarines had greater displacement, especially Typhoon and Oscar, because they used double hull construction which made it possible to put two pressure hulls inside a single outer hull so it made constructing subs with larger internal volumes much easier. For western submarines which used single hull construction volume imposes a hard limit before construction costs grow disproportionately. However western shipyards have never needed to switch to double hull construction because Typhoon and Oscar were early 70s designs which had higher noise levels due to two propellers required for larger hulls. As limiting noise became a priority in the 80s twin-hull design stopped being useful. That reimposed hard limits on single hull submarines even if they used double-hull construction method because it can only increase internal volume so much and advancements in technology provided greater savings of internal space.
While having 20 (ala Typhoon) or even 24 (ala Ohio) IC-SLBMs per SSBN sounds pretty cool - It's not really conductive to concentrate so many nuclear warheads onto one single boat, given how there are plenty of combat (e.g. damaged and/or sunk by enemy action) and non-combat (e.g. maintenance, refueling, accident etc) reasons that would keep an SSBN from performing its responsibilities.
This is not how the calculations were made. The number of missiles per boat was determined by the
total number of warheads on patrol.
Ohio had 24 missiles because that is the number that was required for the subs to have to be able to replace the number of warheads already in service on smaller subs of which there were 41 boats with 12 missiles each - a total of 492 missiles. The number for Ohio-class was 14 boats with 24 missiles which was 336 missiles. Ohio entered service along with Trident C-4 but was designed for larger Trident D-5 which was slated to come into service in the 1990s when Benjamin Franklin-class was to be retired.
If it was possible to build more Ohios and faster and keep them in service in larger number they would likely have 16 missiles like Vanguard. But shipyards could only build so many SSBNs and so many could be kept in service which is why they received 50% more missiles than most SSBNs in service including main Soviet SSBN - Deltas which carried 16 (II, III, IV) or 12 (I). There were 43 Deltas total in service, apart from other SSBNs, while USN needed to reduce the number of SSBNs in favour of SSNs. Soviet Union needed greater number of SSBNs because they were aware of the vulnerability of their subs due to the spy ring that got them information on American sonar.
Sure, China may need less boats...
I won't change my avatar to make that joke land as it should, but...
fewer
Anyway, as I was saying before it is not the number of boats but the number of warheads on patrol so if China has an ICBM with sufficient number of MIRV and PenAids (especially one capable of trajectory over the South pole) then it likely won't need more than 12 to 16 SSBNs total. SSBN payload is calculated for second strike and second strike is always calculated for
everyone regardless of number of belligerents.
This is another element of nuclear strategy that almost nobody is aware of - once you deplete your second strike potential you are defenseless so by definition as soon as you are in strategic nuclear exchange with another nuclear power you are in a strategic nuclear exchange with every nuclear power on Earth.
This is one of the very rational reasons why disarmament talks happened. As soon as the decisionmakers understood the game theory logic of nuclear warfare - which is far more interesting and grim than the "tic tac toe" epiphany in Wargames - it became obvious that there is no reasonable way out of nuclear war. There can never be a limited war because in nuclear exchanges less ammunition doesn't mean a pause in fire until more is made. It means losing the war with a country that you weren't fighting.
Nuclear war is scary this way. Which is why any talk about nuclear exchanges on this forum as if they were a plausible thing are only proof of frightening stupidity of the users engaging in them. Read on nuclear doctrine before you start talking about numbers of warheads or parameters of missiles. People far smarter than you can ever hope to be came up with very reasonable conclusions which is why we had disarmament. None of these psychopaths in power would do it if they could any hope of winning it. There is no hope. Everybody loses. The point of having a nuclear weapon is never to use it. So why have it? Because if you don't have it then someone who has it may use it. So both of you get them and none of you uses them ever again.
And it's not human nature. It's mathematics.
