Ohio Replacement Subs to Shift to Electric Drive

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by KRIS OSBORN
Defensetech September 27, 2013

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.



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Ohio Replacement Submarine Starts Early Construction
by Kris Osborn on October 24, 2013
http://defensetech.org/2013/10/24/ohio-replacement-submarine-starts-early-construction/

The U.S. Navy is in the early phases of prototyping, building specs, and doing design work on its next generation nuclear-armed ballistic missile submarine—the Ohio Replacement Program, service leaders said at the 2013 Naval Submarine League, Falls Church, Va. The new ship, slated for construction by 2021, will replace the existing fleet of Ohio Class submarines, a class of ballistic missile submarines.

The service's chief of naval operations approved the Capability Definition Document last year, leading to prototyping, design work and construction.

"We'll complete 161 ship spec sections this year needed to define the hull and mechanical and electrical systems. This early-stage work is critical to achieving a design that is 80-percent complete by construction's start and producible with few design errors," said Rear Adm. Dave Johnson, Program Executive Officer, Submarines.

Navy program managers with the Ohio Replacement Program, or ORP, describe the CDD as integral to much of the ongoing work. "It helps us understand the requirements upfront so we can work toward executing them in the most cost-effective way possible." said Capt. William Brougham, ORP Manager, in an interview with Military"‹.com.

The ORP is slated to serve through 2085 at 124 patrols per-ship, Johnson said. Construction, testing and design work is underway at a handful of locations around the U.S. and in the U.K., as part of the ongoing technology development phase, or TD phase. The Navy's Ohio Replacement Program is being worked on by Electric Boat, a division of General Dynamics, under a five-year, $1.85 billion deal.

Like other high-priority programs in DoD, the ORP effort faces substantial financial challenges due to the current fiscal environment, sequestration and the lack of a fiscal year 2014 budget.

"I've never seen such a persistently unstable budget in my 31 years in acquisition. We can never forget that our submarine force and our nation are counting on us to succeed," Johnson said. In particular, if sequester continues and if there are more continuing resolutions, the Navy will have to delay ORP production by as long as two years, Navy officials said. Meanwhile, the Navy is working vigorously to lower the per ship cost of the ORP down to below $5 billion.

"The Ohio Replacement Program has a daunting challenge. We have to cut the average ship procurement cost by $700 million dollars – in 2010 dollars – to get to our affordability target of $4.9 billion," Johnson. Part of the cost saving strategy is built into the acquisition and contracting approach, Johnson said.

"The R&D contract with Electric Boat maintains discrete incentives for reaching specific non-recurring operation and support cost. This is the first time a ship-building research and development contract has tied substantive incentive fees to cost reduction areas across the entire life cycle," Johnson said.

Elements of the missile tubes are already under construction as part of a U.S./U.K. common missile compartment deal to mutually develop and benefit from the technology.

"Hardware for this common missile compartment is already being purchased for a Navy test facility in Port Canaveral, Fla.," Johnson said. Overall, the U.K. plans to build 48 individual missile tubes and the U.S. plans to build 192 of the same, Johnson said.

The common missile compartment is also being worked on by General Dynamics' Electric Boat under a $770 million contract. The U.S. and U.K. are buying parts together for the common missile compartment and the U.K. has decided to buy all of its missile tubes off of the U.S. production line, Brougham said. In total, the U.K. plans to build four nuclear-armed ballistic missile submarines, each configured with 12 missile tubes.

The U.S., by contrast, is planning on 12 ships, each with 16 missile tubes. In particular, Brougham said construction is underway on what's called an "integrated tube and hull forging," a structure connecting the tube and steel cylinder with support systems and portions of what will be part of the hull. "At the bottom of the tube there is another section called the eject chamber which is also welded to the hull. This is designed to eject the missile," Brougham said.

The ORP will be engineered to fire the Trident II D5 missile along with heavyweight torpedos. In fact, the Navy plans to restart production of the Mk 48 Heavyweight Torpedoes by 2016, Johnson said. While the ORP will be armed with heavyweight torpedoes, there function is purely defensive in nature, meaning they only are there to protect the ship if it comes under attack. Conventional attack missions are not part of the ORPs mission scope, Brougham said.

"We are a nuclear strategic deterrent. This is a single function submarine that does strategic deterrence," he added. If the program stays on track, the ORP will begin construction in 2021 and then go to sea for three years in 2028 for testing and certification before launching on its first strategic patrol in 2031, Brougham explained.

The TD phase also includes research and investment in certain key areas, such as electric drive, x-shaped stern and propulsion shaft research. The Navy is looking to develop propulsion shaft technology for the ORP that can last as long as 12 years, under an immense amount of strain. "We have to make sure the shaft has the operational availability that we need," a Navy official said.

The Navy is also working on software, computer modeling and something the Navy calls strategic weapons systems, an effort designed to look at individual components for the missile tubes such as valves, hatches and other technologies.

This means that an even quieter boomer than the already very quiet Ohio Class is on the way.