(this article is from www.joebuff.com)
Tango Bravo Today
by Joseph J. Buff, 2005
In late autumn, 2004, the U.S. Navy and DARPA jointly announced a new submarine design feasibility study, TANGO BRAVO. The name derives from the initials T and B, standing for “Technology Barriers” (or more optimistically, “Technology Breakthroughs.”) That initial announcement was met with a mix of enthusiasm, skepticism, and confusion, depending on who you were and whom you listened to back then.
Well, enough time has passed for some dust to have settled, some multi-million-dollar contracts to have been awarded, and some clarity in general to have emerged. As stated rather emphatically by senior Navy officers who are now overseeing and managing the project, TANGO BRAVO is not the design of a new class of super-submarine. Rather, the effort consists of a cluster of interrelated feasibility studies, looking “outside the box” at many different aspects of fast-attack sub layout, arming, and manning. There’s no guarantee that any particular one of these innovative concept thrusts will pan out in practice, and the timeframe for any payoff -- in terms of new subs actually in commission, in the water -- may be better measured in decades than in years. But this is definitely not bad news: It’s simply a reality check on public expectations.
The driving force behind TANGO BRAVO can be summarized in one word, cost. The latest class of fast-attack sub (SSN), the Virginias, at the present funded building rate of one a year have a price tag around 2.5 billion dollars each. Some experts believe that if this building rate could be doubled, to (say) one Virginia per year by General Dynamics Electric Boat and one by Northrop Grumman Newport News Shipbuilding (who now share the work on each sub in a complicated teaming arrangement), the cost per boat would drop to around $2 billion each. That’s still a lot of money, though arguably it’s reasonable for what the Navy and America get in undersea peacekeeping and combat power -- the Virginias are truly superb 21st century capital ships.
But here’s where the problem of fleet size comes in, driven by the problem of cost: A modern SSN has a useful hull life of about 33 years. Building at the rate of one a year, eventually the fast-attack component of our Submarine Force would reach a steady state of 33 vessels. By the 2020s, however, China alone could outnumber us with nuclear-powered and diesel subs together by a factor of five, maybe more. That puts us at the danger point where the advantage tilts from individual quality to sheer quantity, especially in enemy home waters -- i.e., WESTPAC.
If we could build more than one good or great SSN for the same money that currently pays for just one Virginia, our Navy and our country would be better prepared for whatever challenges the future holds. One conceivable way to get a cheaper but capable SSN is to perfect innovative means to make it smaller without sacrificing performance, and perhaps even while enhancing performance. Hence the bold push named TANGO BRAVO.
TANGO BRAVO feasibility studies are looking at five main areas of technology, every one of which contributes significantly to SSN cost over a sub’s useful lifespan, and every one of which could produce very valuable breakthroughs -- genuine upside discontinuities -- in what next-generation American SSNs look like and how they work. It’s way too soon to know for sure how much each of these different directions of exploration and experimentation will pan out productively. Tradeoffs will have to be made, competing new design options will lead to winners and losers in the always-brutal Beltway acquisition game -- and above all there’s the chance of technology failure. Some ideas that sound wonderful today or next year may prove to be too expensive or even infeasible in practice. Enticing artists’ conceptions of futuristic-looking fast attacks in magazines or brochures are merely that: artists’ conceptions. And implementation of any new prototype models or production designs will be subject to the same familiar bugaboos as ever: deadline delays and budget overruns. (The Virginias, originally, were supposed to go for something like only half their current price in constant dollars. The UK’s new Astute-class SSN has suffered nearly crippling delays and overruns due to an atrophying design and engineering expertise base -- a cautionary tale for the U.S.)
So a bit of healthy disbelief seems advised when TANGO BRAVO’s goal is labeled as “the same or better mission capabilities for half the money,” or claims are made that “with concerted effort, an SSN design derived from TANGO BRAVO would be ready for procurement in 2011 or -- under ideal conditions -- even earlier.” On the other hand, we can’t afford to not do TANGO BRAVO, or our own expertise base will wither irrecoverably, and we won’t have a good follow-on class beyond the Virginias.
These are the five main technology areas encompassed in legislation and contract language for TANGO BRAVO:
1. Shaftless propulsion. The propulsion shaft of current SSN designs is long and rather heavy, causing center-of-gravity (trim) difficulties for naval architects, and the shaft requires a large hole in the stern of the pressure hull. Moving to all-electric propulsion, with the drive motors encased in pods outside the people tank, and with hull penetrations needed only for power cables that don’t rotate, is a very attractive alternative. A word of devil’s advocacy, though. A commercial ship with a similar arrangement recently suffered a serious fire in one such pod; no one was injured, but the ship was crippled. And this was on the surface with help nearby -- not deeply submerged during battle maneuvers. The tech for submarine use will surely get there, but the point is it isn’t there yet and it won’t be cheap.
2. External weapons stowage. Right now, a lot of pressure-hull volume is taken up by an SSN’s torpedo room, including its weapon-handling machinery and the torpedo tubes themselves. Were weapons to be carried outside the hull, the ship could prove to be smaller and cheaper. In fact a greater number of bigger weapons might be deployable on a submarine significantly smaller than today’s available SSN classes. If it works, it’s a major gain for American taxpayers. But once more, just for argument’s sake, let me play devil’s advocate. If weapons are stored outside the hull, several new requirements arise. The weapons have to be protected from ambient sea pressure until ready to fire, because riding around for months on end at tens of atmospheres, down deep in corrosive salt water, is more than an Improved Mark 48 ADCAP torpedo or Tactical Tomahawk cruise missile is meant to bear. The weapons, whatever their physical arrangement, need to be enclosed in a streamlined casing of some sort, or else they’d create severe hydrodynamic drag and “singing” that would emit a telltale -- noisy -- acoustic signature and also reduce the ship’s maximum speed. (Are we moving toward a double-hull design like long-standing Russian/Soviet practice? If so, are our cost savings quickly evaporating?) Lastly, even if the weapon-rounds themselves are “wooden,” i.e., meant to be free from any maintenance while on board, the hookups for data links and other required preambles to firing, plus the entire complicated firing mechanism itself, could create fatal problems in case of any malfunction that occurs outside the main hull. Today, at least, all these numerous items required to put torpedoes on target, and the supporting equipment that comes with each Tomahawk vertical launch system tube, are accessible to men in the torpedo room in a shirtsleeves environment.
3. Hull adaptable sonar array. This is a very promising area, since at present an SSN is equipped with several different sonar complexes each of which makes for awkwardness in ship equipment layout, and also in sonar blind spots. As just one example, the sonar dome within the soft nose of current SSNs makes the bow extremely vulnerable in case of collision or battle damage. (See photos released by the Navy of USS San Francisco’s sonar dome while in dry dock after she hit an uncharted seamount.) If sensors could be integrated directly with high-yield steel, all around an SSN’s hull, designers would have important new flexibility.
4. Ship infrastructure reduction. At present, different auxiliary sub-systems in an SSN are powered by electricity, hydraulics, compressed air, or other sources of energy. The result is a multitude of hardware throughout the internal compartments which calls for several distinct sets of maintenance skills, different stocks of spare parts, and different problems (and solutions) in case of a failure or a mishap. All-electric systems could greatly simplify this profusion of cables, pipes, valves, and operating machinery. The result could be a major saving in space (always at a premium in any submarine design) and in cost. However, traditionalists or conservative engineers and seasoned submariners might feel (rightly?) that using a single system to power every device aboard abandons redundancy and puts too many eggs in one basket.
5. Crew size reduction. From the Los Angeles class to the Seawolfs to the Virginias, crew size has dropped only slightly, remaining at well over one hundred men. There’s a type of Catch-22 here, since the larger the crew, the more design weight, space, and cost must be allocated toward habitability. If automation could be significantly increased, crew size might substantially shrink -- and along with it the size and cost of the ship. There’s also a possible double-whammy benefit, as a smaller crew means not only a smaller, cheaper ship (provided automation is achieved at moderate unit expense), it means much lower lifetime charges for the entire fitted-out vessel as an integrated weapon system. This is because personnel themselves cost money, not only to train and nurture as they strive to earn their Dolphins and then climb their chosen career ladders, but also in terms of payroll, health benefits, dependent allowances, pension expenses, and so forth. A devil’s advocate warning I’ve often heard from submariners is that over-automation could become an SSN’s Achilles’ heel. Scuttlebutt has it that newer data displays are non-ergonomic to the point of sometimes being distracting or overwhelming, as it is. When automation extends into the realm of artificial intelligence and expert systems for the control room, we’re entering some pretty serious terra incognita. And when physical things break, it takes human experience, improvisation, and often brute strength to repair them. The human body itself is frail (think USS San Francisco again), so crew injuries are another deleterious factor that can’t be ignored. If an SSN is too mechanized, and available manpower too small, that SSN may look like a terrific bargain on paper, but prove to be a dreadful flop at sea when it goes in harm’s way. Between fixing damage, manually compensating for whatever things have been damaged until they’re fixed, and treating wounded guys with healthy guys who can’t do two things at once, there won’t be adequate people to go around. Mission failures could result, presenting unacceptable threats to national security.
Nobody said TANGO BRAVO would be easy. This discussion can barely scratch the surface of a topic that will be worked on by some of our country’s finest minds, and finest contractors and think tanks, for a long time to come. Hopefully readers have gained a sense of what TANGO BRAVO is so far, what it isn’t, what it might be eventually, and what it can never be. By my own estimate, the first TANGO BRAVO submarine won’t be built, shaken down, tuned up back in dry dock, and ready for battle before about 2022.
The one thing we do know, with the highest certainty, is that the TANGO BRAVO feasibility study has such a long-range payoff, in terms of practical undersea platforms in the water and passing stress tests, that the problem of the one-per-year Virginia build rate will haunt us constantly. Unless, that is, we wise up and allocate more money to build two Virginias per annum when Congress first has the option to do so for fiscal year 2007, rather than putting things off to FY 2012 or forever. In a report to Congress dated June 24, 2005, a TANGO BRAVO fast-attack was already being discussed as costing 75% as much as a Virginia. That’s a heck of a lot of price creep from the 50% referred to barely six months earlier! How much further will this creeping go? When the day is done, will TANGO BRAVO cost savings turn out to be completely illusive, with all emphasis placed on the tech benefits, not the money?
Sea power is the key to global dominance, and to peace-enforcement on favorable terms. Undersea warfare is the key to modern sea power, especially when unmanned vehicles (submerged and airborne) enter the picture. There’s a major backlog in SSN construction compared to even minimum national requirements -- our fast-attack fleet is too small and getting smaller, but the worst shortfall won’t be manifest until 2015 or later, enabling dangerous complacency right now. If that backlog is allowed to grow, instead of being redressed with immediate urgency, America -- if only by default -- will take a big step toward becoming the latest former superpower.
A new Land Warrior project.
IIRC, during the 60`s, the navy looked at radical changes in propulsion such as the Sea engine and the Electro Magnetic Submarine. It`s time to start thinking in an imaginative way in terms of naval engineering. Persnally, I think the USN should get congress to fund some pure research and test bed vessels ike we did with the USS Albacore.
Looks a lot like a Russian sub.