US Navy Submarine Chief Petty Officer explains why it’s not true that Ohio-class submarines lack enough ballast to remain submerged after they fire all of their SLBMs

‘Yes. If a Trident submarine launched all of its missiles the water that backfilled into the now empty tubes would not have enough weight to keep the submarine sufficiently negatively buoyant to remain submerged,’ James Clark, former US Navy Submarine Chief Petty Officer.

The Ohio-class SSBN was conceived in the early 1970s and at 560 feet, they became the largest submarines ever built by the US Navy.

USS Ohio (SSGN 726, the first of her class of ballistic missile submarines [SSBNs] and guided missile submarines [SSGNs], and the fourth US Navy ship to bear the name) joined the US Navy on Nov. 11, 1981.

With the end of the Cold War, the first four Ohio-class SSBNs – Ohio, Michigan, Florida and Georgia – were scheduled to be decommissioned in the early 2000s. The other 14 would remain in service as SSBNs carrying the Trident II D-5 missile. But another plan was in the works – to use the versatile Ohio seaframe to carry Tomahawks or other payloads in lieu of ballistic missiles. The result would be four platforms capable of supporting strike or special warfare missions around the world.

Under then plan, 22 Trident launch tubes were reconfigured to carry either canisters containing seven Tomahawks each – for a total of up to 154 missiles.
Giving these unique features, the Ohio-class submarines provide the Navy with unprecedented strike capabilities.

But how true is the rumor that Ohio-class submarines lack enough ballast to remain submerged after they fire all of their submarine-launched ballistic missiles (SLBMs)?

James Clark, former US Navy Submarine Chief Petty Officer, explains on Quora;

‘This is a misconstrued statement.

‘Yes. If a Trident submarine launched all of its missiles the water that backfilled into the now empty tubes would not have enough weight to keep the submarine sufficiently negatively buoyant to remain submerged.

‘A Trident D5 missile has a mass of 59,000 kg. Water of the same volume has much less mass. The difference is so large that if multiple missiles have been fired then the trim system would be incapable of handling it, thus the existence of a separate system. That is why onboard the ship between the ship’s compartments are massive compensation tanks that extend from the top to the bottom of the ship and side to side and couple feet in length. Think of them as a giant spacer between the compartments.’

Clark concludes;

‘These are flooded during launch to bring on extra water to maintain proper buoyancy.’

Photo credit: Photographer’s Mate 2nd Class Lynn Friant / U.S. Navy