Ohio Replacement Subs to Shift to Electric Drive


The U.S. Navy’s successors to Ohio-class submarines will feature an electric propulsion system, making them quieter and stealthier than today’s versions.

The technology for the ballistic-missile subs is being developed by the Navy and General Dynamics Corp. as part of the Ohio Replacement Program, Rear Adm. Richard Breckenridge told Military.com in an interview. Construction of the boats is set to begin in 2021, he said.

Unlike existing versions, which use mechanical propulsion technology, the replacement subs are designed to have an electric-drive system, Navy officials said. The technology still relies on a nuclear reactor to generate heat and create steam to power turbines, they said. However, the electricity produced is transferred to an electric motor rather than so-called reduction gears to spin the boat’s propellers, they said.

“We just take the electricity from those high-speed turbines and use that electricity to drive an electric motor that propels the ship,” Breckenridge said. “It is quieter than a mechanical drive system.”

Evolving global threats require ever more quiet submarines, Navy officials said. The Navy decided to invest in the technology after reaching the limits of trying to silence mechanical propulsion, they said.

“Great minds have figured out how to get those gears whisper quiet,” one Navy expert said. “We did not have any more tools in the bag to get the stealth that we knew we needed for this national strategic imperative.”

The Navy has experimented with electric drive in the past, but it took 15 years for the service to perfect the technology, officials said.

The system offers a number of potential advantages, including noise reduction, according to Bryan McGrath, managing director at FerryBridge Group LLC, a defense consulting firm based in Easton, Md.

“When you have the motor tied directly to the propulsion shaft, that should eliminate some of the noise,” he said.

Electric propulsion can also help ships generate more on-board power for electronics, sensors and weapons systems, McGrath said.

“Electric drive makes a lot of sense for submarines,” he said. “There is some technical risk in moving from mechanical to electric drive, but electric drive has been around for decades. The DDG 1000 (Zumwalt-class destroyer) surface ship is also electric drive — so you have two very big important ships are moving to electric drive.”

Other innovations in the submarine program include an X-shaped stern to improve maneuverability and stealth, officials said. As subs evolved from using propellers to more quieter propulsors, they lost some surface maneuverability, they said.

“With the X-stern, the Ohio Replacement will regain some of that maneuverability and, as a side effect, will have improved flow characteristics in the stern area while submerged,” the Navy expert said. “This will improve quieting and it simplifies the hydraulic control layout in the engine room.”

Similar to the current Ohio-class submarines, the replacements will be equipped to fire the Trident II nuclear missile, Breckenridge said. The missile, designated D5, has proven reliable in testing, with all but one of its 149 test shots successful, he said.

“Last week we did another round of successful firings of that missile,” he said.
“The performance of that strategic missile is just incredible. As we look to deter bad behavior from other countries, we’ve got this kind of reliability.”

The new subs will eventually be fielded with the successor to the D5, Breckenridge said. The program office is also working with officials in the United Kingdom to engineer a common missile compartment. General Dynamics’ Electric Boat unit in Groton, Conn., is building prototypes under a $770 million contract.

The Ohio Replacement Program aims to control costs in part by borrowing technology already in production on the Virginia-class attack submarine program, officials said. Examples of the technology include conformal plane array sonar, fiber-optic links between sail-mounted cameras and a control room and “fly-by-wire” digital controls that allow crews to use a joystick and touch-panel to control the boat, they said.

Sonar technology is of particular importance to a submarine platform whose mission depends upon quietness and detectability, Breckenridge said.

“The SSBN has to have a capable sonar system with hull arrays,” he said. “We also stream along a towed array by putting out a string of transducers that give you that much more listening power. SSBN wants to detect an undersea adversary – if we can hear them further than they can hear us we have a tactical advantage in the undersea domain.”

In addition, the new submarines are being engineered with a new nuclear-reactor core designed to power the ships for 42 years. Unlike the current Ohio-class SSBNs, which require a multi-year refueling process halfway through their service life, the new Ohio Replacement boats will be able to continue their missions without needing a refueling pause, Breckenridge said.

The technology also allows the Navy to conduct the same mission with fewer submarines, service officials and analysts said.

About the Author

Kris Osborn
Kris Osborn is the managing editor of Scout Warrior and a former associate editor at Military.com.

37 Comments on "Ohio Replacement Subs to Shift to Electric Drive"

  1. Glad to see Ohio get the new tech added to them I dont see them going away or any new sub coming soon in this fiscal environment.

  2. Let's just keep the lid on this from R&D through production. We cannot afford to let the Chinese infiltrate our Contractors and steal our secrets, like most other programs have. This is our last step up in our weapons and delivery systems which they have not gotten away with all of our secrets. Cyber espionage is huge and more sensitive information is being stolen each and everyday. Like the old adage states…Loose lips sink ships. Instill this in every military branch like they used to, and this crap will STOP ASAP!!!

  3. Have to wonder about the magnetic signature that can be observed from the air over a sub with this type of propulsion.

  4. Ohio Replacement Program = NOT Ohio Class. Talk about bad titling. This has nothing to do with the existing boats at all.

  5. I'm curious if we can progress ballistic grade polymer fast enough to make ships/subs out of them.

    That should improve sound signature correct?

  6. China is building new nuke subs and missiles. These SSBNs will be patrolling in the Gulf of Mexico and Atlantic within 3-5 years. China has not the bogus 240 nukes advertised but between 1,200 (Russian intel) and 3,000 (Georgetown U. Study). China is building between 100-300 nukes per year of various designs. She just took delivery of 15 new turboprop strategic bombers.

  7. None of the newer SSBN's are being designated as replacements for the Ohio SSGN subclass, and the POTUS designated a pile-o-dough for the extension of the Virginia hulls to provide a similar capability.

    Lamentably, the GOP-led HoR voted the funding for the Virginia hull extension program down to ZERO dollars. Hence – this important capability looks like its going to be lost when the Ohio SSGN's are decommissioned.

  8. Perhaps the next SSGN'ed submarine should also serve as a electric drive testbed? Let's figure this out before the R&D is billed to SSBN-X and each submarine costs more than its weight of platinium and rare earth metals.

  9. @blight the US NAVY operated a Electric drive nuclear sub in the 1970's I think ,and the French have been using Electric drives on their sub's for years. the only reason the US navy did not go with them was they where conservative and did not trust the technology.

  10. If they're smart they'll make it a hybrid drive so they can run silently using the electric drive but have the full power of the steam turbine available to run if they really need to get somewhere fast.

  11. Nice. I wonder if it will be as quiet as, say, a Type 214 with AIP and fuel cells or if the reactor cooling system will still be a big giveaway.

  12. I'm curious how exactly they'll "tie the electric motor directly to the propeller shaft" without reduction gears. Electric motors of all kinds favor RPM. Especially those under a heavy load like moving a large amount of (relatively) viscous fluid at any given moment.

    IMO, one more thing to fail for propulsion in an emergency.

  13. I am totally elated to finally see a subject where so much constructive information is passed out, instead of the usual dribble that we see so much of. Thank you one and all for your very informative comments.

  14. They could go further and expand the steam through a piston engine instead of a turbine and use the engine to turn the generator. That way there would be nothing whirring away at really high RPM. If they did that, the steam powered engine could work as a 2 stroke and develop twice the horsepower of the equivalent diesel burning engine. Since the reactor itself doesn't make any noise, then they'd be at least as quiet as a diesel electric if not quieter, plus they'd be able to run long distances underwater and make their own air like they do now.

  15. FYI: the chinese have successfully attach a "star fish" to a U.S. sub to track it for a distance of a few hundred miles using the same tech as the whale tracker but quieter, it broadcasted a very tiny burst of signal of computer code! this meant U.S. sub is no longer invinsible! this occurance off the coast of Japan sometime! and it is not a magnitised device but some kind of suction that look very much like a sucker fish that is very small! I hope the U.S. Navy is aware of this! if not pass this to them asap. The source is not reliable, but the info is investigatable! the attachment was attached while the sub was not at home base.

  16. Wow! What a lot of info to absorb and yet it's not all that difficult to condense into what is coming next. First, propulsors give the boats great maneuverability. Then the EMF signal from the electric motors has been dealt with for years so not a problem. Boats will revert back to (almost diesel boats) but eliminating the diesel for a very quiet reactor instead. DBF now becomes NBF. As to secrecy let us hope that the company which put out a scale model of our Boomers in the 60's doesn't get access to data allowing them to do it again. AIPs are not quiet enough and are also limited duration so phooey to that technology. Finally, the new reactor technology has enough excess power to be used for future weapons (think of the Bush class CVN which has electric launchers and will carry rail guns. I don't know much more but my experience tells me that we have a great submarine coming in the future.

  17. Nice article however I would be interested in how the experience with the SSN-685 propulsion plant is being parlayed into a new design. Clearly the surface fleets experience with AC power conversation equipment and improved efficiencies are now viewed as doable in a submarine.

  18. Why would the Chinese bother to infiltrate? Just do like they did in Clinton's time and give political donations to the DemoncRat Party. The DNC will hand-over the drawings and data and the American Sheeple will yawn and watch American Idol reruns.

  19. The USS Glenard P. Lipscomb (SSN 685) was the US Navy�s second prototype design using a turbo-electric power plant similar to the USS Tullibee (SSN-597). The Glenard P. Lipscomb was generally similar to the SSN-637 Sturgeon class, apart from the use of submarine turbo-electric drive [TEDS] rather than the standard geared drive. Intended to test the potential advantages of this propulsion system for providing quieter submarine operations, the substantially larger and heavier machinery also resulted in slower speeds. Those disadvantages, along with reliability issues, led to the decision not to utilize this design on the follow-on SSN-688 Los Angeles class of submarines. Although serving as a test platform, the "Lipscomb Fish" was a fully combat-capable attack submarine.

  20. It's about time, this is the norm for new surface merchant vessels and has been for a while already, especially in "high-tech" vessels. Those subs ought to be.

  21. Being a Boatswain Mate I never served aboard subs, but I was on two sub tenders and I retired from NSSF New London OPS Department where I was on tugs that moored subs (they can't get underway or dock without BM's) so I know a little about what subs can do. But, for the media to release any information about the technology of our submarine fleet is irresponsible. The Chinese and other countries already do enough damage to our military through cyber spying we sure don't need to whet their appetites by announcing new thecnology through the news media.

  22. Wilderness voice | October 3, 2013 at 2:40 pm | Reply

    We lack the will to use them why have them.

  23. Just want to state that way the system of a motor driving the propeller shaft works is this: The shaft is wrapped and becomes the rotor. The stator is stationary with the shaft going through it. There is no clutch used to couple the motor for drive but it can be decoupled from the propeller. Not sure of this arrangement. It is a DC motor so can be fine tuned as to the number of revolutions (speed control). As someone stated the torque varies with the voltage applied but there are new materials and controllers now which can use DC much more efficiently. If you want to see an actual submarine with such a system, google the USS Dolphin which is on display at the Maritime Museum in San Diego.

  24. Whatever happened to MHD drives for subs? When I was in the Navy (80's), the Soviets were rumored to have it. The fictional "Red October" had it, but was it fictional or not?

  25. In regard to electric drive, didn' the Lexington (CV2) and Saratoga (CV3) have electric drive when they were built back in the 1920's?

  26. Seems like this makes perfect sense as electric drive would significantly reduce radiated noise. Hardly a secret technology also.

  27. Reading through the post and the comments as well makes me think that i think media or journalists must have a little of etiquette and limitations. They might be allowed to search for something to report but I think it must undergo screening and evaluation of their reports especially if it harms the security of the country. I mean they would still have that freedom but they must also think of how to save and help the country through responsible selection of reports. I guess we already know what's helping us and what's not for the benefit of the many people and the country itself.

    On the other hand, I was wondering how does it feel to ride in a sub?

  28. look at brit type 45 destroyer and new carrier class.
    all electric propulsion

  29. I was an A -ganger on the Hawkbill and in a sense the boats are somewhat of a hybrid in the first place you can ether run power from the diesel gen to the battery to the aux electric motor . or run the turbo generators to the battery to the aux electric motor. running on the battery is by far the quietest mode of operation. the bad part is that if you have to get out of dodge in a hurry, your screwed.

  30. Wow! Using electric engines to run submarines!? They say it's been around for 50 years? Electric propellers were already in use when WWII began in 1939, which was 76 years ago.

  31. Brian B. Mulholland | April 29, 2015 at 12:12 pm | Reply

    davec, they did. So did the South Dakota battleships of WW II vintage; I believe a couple of older battleships, built between the wars, did so as well.

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