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PEO Subs: Navy’s Future Attack Sub Will Need Stealthy Advanced Propulsion, Controls for Multiple UUVs

The Los Angeles-class fast attack submarine USS Toledo (SSN 769), assigned to Commander, Task Force (CTF) 54, transits through the Arabian Gulf on Jan. 21, 2016. US Navy photo.

The Los Angeles-class fast attack submarine USS Toledo (SSN-769), assigned to Commander, Task Force (CTF) 54, transits through the Persian Gulf on Jan. 21, 2016. US Navy photo.

This post has been updated to include additional information about potential advanced propulsion system development.

The Navy won’t begin buying its next-generation attack submarine until 2034, but researchers are already hard at work on two key components of the SSN(X) program: an advanced propulsion system for quieter operations, and the ability to control multiple unmanned underwater vehicles at once for extended influence.

These attack boats will operate through the end of the 21st century and perhaps into the 22nd century – and Program Executive Officer for Submarines Rear Adm. Michael Jabaley believes there will still be a place for submarines in naval operations as long as the boats can keep up with changes in the operating environment.

“There’s been a lot of discussion about the future of submarines and the future of stealth and the future of anti-submarine warfare – and we take all of that into account and still firmly believe there’s a significant role for the submarine in the United States Navy well into the heart of this century and beyond,” Jabaley told USNI News in a March 3 interview.
“Now, that said, there are a lot of things that are happening that require some fundamental changes to what we consider an attack submarine to be. And some of it we’re already doing” as the office works through the design of the upcoming Ohio Replacement Program ballistic missile submarine.

To keep up with ever-improving sonar systems, the ORP will have an electric drive system.

“It’s still got a nuclear reactor, it still uses that reactor to generate heat and generate steam, but ever since we went to the nuclear reactor we’ve used that steam to drive turbines to generate electricity and turbines to generate main propulsion,” he said.
“This is one area where the significant improvements in stealth, quieting and sonar performance have gotten us to the point where we felt that in order to make the ship survivable over its entire lifespan we had to get away from those gears and pinions and reduction gears, because no matter how well you make them, they’re still heavy pieces of metal turning each other, and that generates a noise you just can’t completely quiet. So going to an electric drive system — still you’d have turbines to generate electricity, but now instead of turning gears and pinions and reduction gear, you’re turning an electric motor. So that’s a significant advance in quieting.”

SSN(X), then, could have either a similar electric drive to stay as quiet as possible, or a new advanced propulsion system that does not exist today, Jabaley said. He is already challenging the research and development communities in and outside of the Navy to tackle his propulsion problem to help these future attack subs remain as stealthy as possible regardless of whatever advances in anti-submarine warfare the next several decades bring.

“I’m not just talking about the propeller or propulsor, it’s the whole propulsion system from power generation to motion through the water,” he said.
“How am I going to get beyond the limitations of a rotating set of blades and the unavoidable noise that I just can’t get below? At this point there are no bounds on what I want people to be thinking about. I’m not the smart guy – they’re the smart guys, come tell me what the next submarine is going to look like and why, and then we’ll figure out is that achievable, can we develop the technology to get there, and then do the trade analysis – here are the benefits it brings, here’s the cost it requires versus what we’ve done in the past.”

An advancement in propulsion would, hopefully, bring about defensive advantages, making the submarine harder for a potential adversary to locate. To boost the submarine offensively, Jabaley said deploying multiple UUVs simultaneously would be a must for SSN(X).

“We have done a reasonably good job of designing UUVs that can be deployed using existing interfaces, we’ve deployed them out of torpedo tubes, out of the 3-inch countermeasure launcher, out of the trash disposal unit, but it’s almost always one at a time and limited time and it requires the entire focus of the ship to do that at that time. We’ve got to get beyond that,” he said.
“So the SSN(X) has to have UUVs as a key part of expanding its reach so the affected domain of that submarine grows from just the immediate area that its sensors interact with to something much much larger.”

Jabaley said this vision would take advances in command and control to accommodate working with multiple vehicles at once, communication, data relay, and even energy – with UUVs constantly deploying, they would need to be quickly recharged, which could take place by bringing the vehicles back to the submarine or by directing them to chargers on the seafloor.

“This new submarine is going to have to lock into a system that allows its impact to be felt in a much much greater sphere than we have now,” Jabaley said.

As the Navy works towards that goal, there may be an opportunity to test incremental advances in future Virginia-class subs instead of waiting for the SSN(X) program to start. The Virginia-class attack subs have been built in blocks – Block III lowered the cost per boat to about $2 billion, and the current Block IV tackled total ownership costs by eliminating the need for a maintenance period and adding an additional deployment in its place. Block V, which will begin in Fiscal Year 2019, will insert the Virginia Payload Module to help mitigate the reduction in firepower when the four SSGNs – which carry 154 Tomahawk missiles each – retire in the mid-2020s.

Blocks VI and VII, though, remain undefined still in terms of the improvements they will bring to the class, Jabaley said. These boats may present an opportunity to start introducing more advanced UUV operations ahead of the major shift SSN(X) will bring.

  • sferrin

    Turbo electric drives have a history of poor performance. Neither Tullibee (SSN-597) nor Glenard P Lipscomb (SSN-685) were very impressive, and did nothing to convince the USN that turbo-electric was the way to go. Quite the contrary. Might be acceptable for an SSBN (particularly since the new one is suppose to be significantly larger than the Ohios despite having half the weapons), not for an SSN. Very poor power to weight ratio compared to direct drive.

    • RobM1981

      “Building 597” certainly had it’s problems…

      Perhaps the technologies have matured?

    • B.J. Blazkowicz

      We’ve come a long way from unreliable 1960’s technology. What they want now is possible with COTS equipment.

    • NavySubNuke

      “particularly since the new one is suppose to be significantly larger than the OHIOs despite having half the weapons”
      False – ORP will be about the same size as the OHIO and will have 16 tubes vice 24 tubes.
      But just counting tubes isn’t a good measure considering the launcher and warhead limits of the New START treaty and how the US has publicly announced we will meet those limits. Namely, we are converting 4 of the 24 OHIO tubes to not be able of carrying a missile so by the time ORP enters the fleet it will be with 16 vice 20 tubes. Also, the OHIO and ORP will likely carry the same number of “weapons” since each missile carries multiple warheads – the only thing that would change would be the average loading per missile.

      • sferrin

        Thought ORP was suppose to be 24,000 tons submerged? And tube count is a VERY good way of measure giving the subs will be in service half a century and treaties have a way of changing. Bit difficult to chop a sub in two and stuff eight more launchers in there when (not if) the START treat becomes null. I suppose they could just continue to add numbers to the class. Lastly, sticking 24 (or 20) missiles worth of warheads on 16 missiles will cut their range. So fewer missiles with lower range? Not a good idea IMO.

        • NavySubNuke

          I’m pretty sure 24K tons is not correct. ORP is basically the same size as OHIO just a lot stealthier according to what I saw at the last Sub League Symposium. Can’t find a source for that though. I do remember specifically that it was the same length.
          Tube count matters to some extent but our missiles have enough “extra” range it isn’t that big of a deal. The SSBN leg is already going to carry something like 75% of the new START warhead count – more tubes would just encourage policy makers to put even more eggs into that basket.
          IMO the greater crime with ORP was going with the same 87″ tubes instead of jumping up to 97″. But the budget of today won out over flexibility in the future on that one.

  • RunningBear

    Turbo electric drive, fifteen years later in development, will be implemented in the ORP. The electric drive part is now underway in the DDG-1000 Zumwalt-Class. Maybe the Canoe Club will have better luck with the newer designs. Time will tell.

  • Russ Neal

    Probably also will have to operate at greater depths to avoid active sonar detection. Maybe a long skinny hull design to take the pressure?

  • KellyJ

    The Lexington and Saratoga had Turbo Electric drive and certainly had no problems with their performance in WW2. Perhaps the issue is less about the technology and more about the gold plating.

    • NavySubNuke

      You can call qualities like stealth, efficiency, and small size “gold plating” if you like but the fact of the matter is they are absolutely essential to having a successful submarine – and they aren’t cheap qualities.
      Making this type of drive quiet while still providing the necessary power from something that actually fits inside the submarine is no simple challenge. The Navy has tried several times already and always failed. Its only now that technology has actually advanced enough to make it possible.

  • Secundius

    “It’s Aaah Revelation, It’s a Miracle”. The German Kreigsmarine Figure that out Back in 1941. And it Took the US Navy 75-years to figure that one Out…