New Project Envisions Smaller Submarine

New Project Envisions Smaller Submarine

Since 01-02-05

Excerpted from NSL UPDATE 12-23-2004

Cheaper boats would still pack a punch, Navy, Pentagon says

By Robert Hamilton, Day Staff Writer, Navy/Defense/Electric Boat,

Published on 12/18/2004 Used with permission.

The Navy and a Pentagon research agency have teamed up to develop a submarine that would have all the capabilities of the Virginia class, but at half the size and price. A study that concluded earlier this year, which Navy sources said involved considerable participation by Electric Boat in Groton, concluded that several promising technologies could help reduce the cost and size of a submarine without detracting from its warfighting ability.

The Defense Advanced Research Project Agency, a Pentagon organization that investigates the potential for dramatic advances in weapons systems, has launched a program called Tango Bravo to build a smaller but still potent submarine, according to the agency's planning documents. One of the key technologies would be shaftless propulsion, likely some form of electric drive that would use power from the nuclear reactor to turn a network of distributed electric motors, thereby eliminating the heavy reduction gears, shaft and associated gear. But the study will also look at a new type of sonar array, launching weapons from magazines outside the hull, an automated attack center and other “radical ship infrastructure reduction.”

The Virginia is 377 feet long and displaces just under 7,900 tons. A half-size Virginia would focus on cutting weight from the current ship, though it would not necessarily be half the length — the Skipjack class in the 1950s and '60s, for instance, displaced 3,500 tons, but was still 252 feet long. On Dec. 22, the research agency will receive proposals from defense contractors who are competing to support the program.

Electric Boat officials said that given the nature of the program, which is largely classified, they cannot comment on Tango Bravo. But if the program can cut the price of submarines in half, the Navy might finally be able to build two submarines a year, up from one now, which stands to benefit the shipyard in two ways:

• On the waterfront, it would make it easier to keep fresh the skills of highly technical workers. Some jobs on a submarine are so unique they are only done once on every ship. If the Navy is building just one a year, that skill can atrophy because months pass until it is employed again. If the Navy builds two a year, that worker gets twice as much experience.

• In the design force, Tango Bravo promises years more work to incorporate some of the advances. Electric Boat is running out of work for its 2,700 designers and engineers. The Virginia-class design is largely complete, the special hull section for the Jimmy Carter is installed, and the conversion of four Trident submarines to fire conventional missiles is nearing an end.

“DARPA and the Navy are excited about embarking on this new endeavor,” said Jan Walker, a spokeswoman. “We believe that the Tango Bravo technology demonstrations promise to go a long way toward providing new submarine capabilities for the Navy.” She added that contractors appear interested in the program, with more than 140 turning out for a conference last month to discuss proposals. DARPA and the Navy will put $97 million into Tango Bravo concept development and prototyping over the next four years.

DARPA hopes to announce in the spring which companies will win contracts under Tango Bravo, then make a decision by late in fiscal year 2006 on which of the concepts should be moved into prototype production and do full-scale demonstrations in early 2008 and at-sea demonstrations in 2009. Key to the undertaking will be reducing the size, weight, complexity and cost of the nuclear propulsion plant. Currently, the nuclear reactor produces steam that powers a turbine. A huge set of gears reduces the revolutions of the turbine to a much slower shaft speed, which turns the propeller. The Navy's goal is a propulsion plant at least as quiet as Virginia — electric drive could turn out to be even quieter — while reducing the price at least 40 percent.

A smaller plant could be just the start of the savings, said Nicholas L. Flacco, a former commander of the Groton-based submarine USS Groton, now a senior scientist at Areté Associates in California. Submarines have always been sized around the propulsion plant, and if you get rid of the reduction gears and the shaft, you're talking about many tons of weight and cubic yards of space, which drive down the size that you need,” said Flacco. “You get an exponential decrease in the power requirements when you have weight reduction, so if there's anything you can do to achieve that it pays big dividends,” Flacco said. “The ship could start getting smaller very fast. All of those features could pretty quickly move you down towards a half-sized ship.”

Another area that could yield tremendous space savings is in the sonar system. Tango Bravo seeks what is known as a “hull adaptable sonar array,” which would do away with the sonar dome at the front of the boat and replace it with a system fitted to the entire hull. The Navy wants a system that will be able to track ships from at least five nautical miles away in congested near-shore areas, where it might have to differentiate that ship from 250 others. And it wants to do it while cutting at least in half the volume of sonar processing equipment o board.

Similarly, the partnership has asked for concepts for a new automated attack center that could trim the number of people needed to take the ship into combat from 17 to eight, both by automating more functions, and by providing displays that pass information so effectively that one sailor can do the job of two. External weapons and stowage has been a feature of attack submarines since the USS Providence was commissioned with its vertical missile launching system in 1985. Tango Bravo seeks a way to link fire control systems inside the ship to magazines of weapons outside the ship, so it could fire an externally mounted torpedo at maximum speed and operating depth.

DARPA has thrown the door open to any number of innovations. Tango Bravo will consider “radical ship infrastructure reduction.” The only conditions it places on proposals is they must be rugged enough for a warship, and reliable enough to last for patrols that can go 90 days or longer without an opportunity to maintain them. Retired Rear Adm. Charles H. “Chip” Griffiths, now the director of command and control systems at Raytheon's Rhode Island division, said the interesting thing about Tango Bravo is it makes it possible for defense contractors from other areas of expertise, not just submarine designers, to make innovative suggestions. “The march of technology is relentless, and our ability to continue to think smarter, more out of the box, more from a human engineering approach, really haven't begun to approach the boundaries,” Griffiths said.