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Attack submarines are much smaller than missile subs. I don't understand exactly why this is and what the trade offs are here - manoeuvrability, cost? They seem

Attack submarines are much smaller than missile subs. I don't understand exactly why this is and what the trade offs are here - manoeuvrability, cost? They seem to need approximately the same size crew of 100-150. The closer comparison would be to the US Ohio-class missile sub, which is 3x the size of the LA class with the same complement. https://en.m.wikipedia.org/wiki/Ohio-class_submarine https://en.m.wikipedia.org/wiki/Ohio-class_submarine

brandmeyer 6y ago
> I don't understand exactly why this is and what the trade offs are here - manoeuvrability, cost? Payload. One type carries a couple dozen medium-range ballistic missiles, and the other doesn't.
- dmurray 6y ago
  The Ohio-class carries 24 60-ton Trident missiles, 1,440 tons of dead weight. That doesn't seem like enough on its own to justify the difference in displacement of 18,000 tons vs 6,000 on the Los Angeles-class. (I'm just getting these numbers from Wikipedia so may misunderstand something)
  - chasd00 6y ago
    "24 60-ton Trident missiles". wow, so let's say each has a MIRV with 5 W88 warheads at 500KT each. That's about 120 independently targetable warheads (each 6-7x more powerful than the Fatman nuclear weapon dropped on Nagasaki) per submarine. Wikipedia says they are on 14 Ohio class subs operated by the US. That's 1,680 total but let's say only 75% are operational at a time. So the US Trident II SLBM cocked-locked-ready-to-rock capability is around 1.3K 500KT warheads alone. That's... a lot.
    - angry_octet 6y ago
      More like half active, a quarter in port or in light maintenance, a quarter in deep maintenance. Realistically, two always on station from each fleet, sometimes four. Enough to maintain second strike deterrence even with enemy attack subs to contend with. It also important to note that once an SSBN launches, there will likely be return fire from either land or sea based ballistic missiles that will boil the ocean for 50nm, incoming in 30-60 minutes. So tactically it is hard to launch just one nuke... It's full commitment or nothing. Just another cheery aspect of escalation dynamics.
    - dragonwriter 6y ago
      > So the US Trident II SLBM cocked-locked-ready-to-rock capability is around 1.3K 500KT warheads alone. That's... a lot. Aside from overstating operational readiness, you also upped the W88 yield from it's actual 455KT and, while most sources do reported that 4-5 warheads per missile is typical, you assumed all in the fleet or W88s, while they seem to be a mix of W88 and 90KT W76. So it's a lot less ready to go than you've estimated here. But, OTOH, it's still a lot.
chiph 6y ago
You need a certain diameter of the pressure hull in order to accommodate the length of the missiles and their launch tubes. Also a factor - the range of the missile. Want a longer range? You'll need more fuel and the missile gets longer. Which means you need a bigger sub.
masklinn 6y ago
> Attack submarines are much smaller than missile subs. I don't understand exactly why this is SLBM are big, a Trident II is 13.6m long and 2.11m wide[0] and Ohios need to fit them straight up plus the hull, so we're talking 14m moulded depth or so (excluding the sail), and a pretty similar beam, at which point… you just have a big sub, because it can't exactly be a ball: you need to fit 12 Tridents in a row, plus the reactor, engine, crew compartments, passages for the crew to move around, torpedo tubes, and enough stores to last for literally months. Attack subs can have vertically mounted cruise missiles but those are puny compared to an SLBM, a Tomahawk is 6.25m long with booster[1]: an Ohio-class carries 24 Tridents in SSBN configuration, if converted to SSGN it carries 154 tomahawks. Los Angeles carries 37, Seawolf carries 50 (and on both this competes with torpedoes and anti-ship missiles, on an Ohio you get 24 tridents or 154 tomahawks plus a dozen torpedoes or anti-ship missiles). [0] and Typhoon's SLBMs were even larger at 16.1m by 2.4 [1] and 0.5m wide
- jabl 6y ago
  Also, reportedly Soviet ballistic missiles were/are less accurate than US ones, so they compensated by having a bigger bang, in turn needing a bigger missile to launch it. Another solution would be to do what the North Korean missile subs, putting the missile tubes in the (lengthened) sail.
  - masklinn 6y ago
    > Another solution would be to do what the North Korean missile subs, putting the missile tubes in the (lengthened) sail. The US used to have something like this in the Regulus, their intended launcher (the Grayback-class) essentially had hangars. The great advantage of SLBMs is that the vertical mounting and a good enough launch sequence means you don't have to surface to launch: https://youtu.be/sUlXty69-Y8 https://youtu.be/sUlXty69-Y8
- dmurray 6y ago
  I didn't consider that the missiles need to be stored vertically, but that makes a lot of sense, thanks.
dragonwriter 6y ago
> Attack submarines are much smaller than missile subs. I don't understand exactly why this is Because a missile sub is, loosely, an attack sub with an ICBM base strapped to it. (Yes, technically SLBMs aren't ICBMs, but late Cold War SLBMs had ranges greater than the upper end for IRBMs, and so would be ICBMs if land based.) > and what the trade offs are here - manoeuvrability, cost? The boomer trades off maneuverability for the ability to destroy a moderate-size country with nuclear hellfire from thousands of miles away.

brandmeyer 6y ago

> I don't understand exactly why this is and what the trade offs are here - manoeuvrability, cost? Payload. One type carries a couple dozen medium-range ballistic missiles, and the other doesn't.

dmurray 6y ago
The Ohio-class carries 24 60-ton Trident missiles, 1,440 tons of dead weight. That doesn't seem like enough on its own to justify the difference in displacement of 18,000 tons vs 6,000 on the Los Angeles-class. (I'm just getting these numbers from Wikipedia so may misunderstand something)
- chasd00 6y ago
  "24 60-ton Trident missiles". wow, so let's say each has a MIRV with 5 W88 warheads at 500KT each. That's about 120 independently targetable warheads (each 6-7x more powerful than the Fatman nuclear weapon dropped on Nagasaki) per submarine. Wikipedia says they are on 14 Ohio class subs operated by the US. That's 1,680 total but let's say only 75% are operational at a time. So the US Trident II SLBM cocked-locked-ready-to-rock capability is around 1.3K 500KT warheads alone. That's... a lot.
  - angry_octet 6y ago
    More like half active, a quarter in port or in light maintenance, a quarter in deep maintenance. Realistically, two always on station from each fleet, sometimes four. Enough to maintain second strike deterrence even with enemy attack subs to contend with. It also important to note that once an SSBN launches, there will likely be return fire from either land or sea based ballistic missiles that will boil the ocean for 50nm, incoming in 30-60 minutes. So tactically it is hard to launch just one nuke... It's full commitment or nothing. Just another cheery aspect of escalation dynamics.
  - dragonwriter 6y ago
    > So the US Trident II SLBM cocked-locked-ready-to-rock capability is around 1.3K 500KT warheads alone. That's... a lot. Aside from overstating operational readiness, you also upped the W88 yield from it's actual 455KT and, while most sources do reported that 4-5 warheads per missile is typical, you assumed all in the fleet or W88s, while they seem to be a mix of W88 and 90KT W76. So it's a lot less ready to go than you've estimated here. But, OTOH, it's still a lot.

chiph 6y ago

You need a certain diameter of the pressure hull in order to accommodate the length of the missiles and their launch tubes. Also a factor - the range of the missile. Want a longer range? You'll need more fuel and the missile gets longer. Which means you need a bigger sub.

masklinn 6y ago

> Attack submarines are much smaller than missile subs. I don't understand exactly why this is SLBM are big, a Trident II is 13.6m long and 2.11m wide[0] and Ohios need to fit them straight up plus the hull, so we're talking 14m moulded depth or so (excluding the sail), and a pretty similar beam, at which point… you just have a big sub, because it can't exactly be a ball: you need to fit 12 Tridents in a row, plus the reactor, engine, crew compartments, passages for the crew to move around, torpedo tubes, and enough stores to last for literally months. Attack subs can have vertically mounted cruise missiles but those are puny compared to an SLBM, a Tomahawk is 6.25m long with booster[1]: an Ohio-class carries 24 Tridents in SSBN configuration, if converted to SSGN it carries 154 tomahawks. Los Angeles carries 37, Seawolf carries 50 (and on both this competes with torpedoes and anti-ship missiles, on an Ohio you get 24 tridents or 154 tomahawks plus a dozen torpedoes or anti-ship missiles). [0] and Typhoon's SLBMs were even larger at 16.1m by 2.4 [1] and 0.5m wide

jabl 6y ago
Also, reportedly Soviet ballistic missiles were/are less accurate than US ones, so they compensated by having a bigger bang, in turn needing a bigger missile to launch it. Another solution would be to do what the North Korean missile subs, putting the missile tubes in the (lengthened) sail.
- masklinn 6y ago
  > Another solution would be to do what the North Korean missile subs, putting the missile tubes in the (lengthened) sail. The US used to have something like this in the Regulus, their intended launcher (the Grayback-class) essentially had hangars. The great advantage of SLBMs is that the vertical mounting and a good enough launch sequence means you don't have to surface to launch: https://youtu.be/sUlXty69-Y8 https://youtu.be/sUlXty69-Y8
dmurray 6y ago
I didn't consider that the missiles need to be stored vertically, but that makes a lot of sense, thanks.

dragonwriter 6y ago

> Attack submarines are much smaller than missile subs. I don't understand exactly why this is Because a missile sub is, loosely, an attack sub with an ICBM base strapped to it. (Yes, technically SLBMs aren't ICBMs, but late Cold War SLBMs had ranges greater than the upper end for IRBMs, and so would be ICBMs if land based.) > and what the trade offs are here - manoeuvrability, cost? The boomer trades off maneuverability for the ability to destroy a moderate-size country with nuclear hellfire from thousands of miles away.