Ship Superstructures

I’ve noted, over the years, the Navy’s trend toward larger and larger superstructures.  Much of this is due to stealth considerations but not all.  Let’s take a look at the trend and then we'll discuss the implications.

WWII early war Gato submarines had fairly large superstructures.  As the war progressed, these were steadily cut down until only the barest structure remained.  This was done to reduce silhouettes and the concomitant chance of visual detection.  Look at the Gato profiles below and note that the superstructure was reduced by around 50% which significantly lowered the profile and reduced the total visible superstructure bulk.

Gato - Early War

Gato - Late War

WWII ships in general and the Fletcher class destroyer, specifically, had narrow, small superstructures.  In the drawings below, note the relatively wide deck areas on both sides of the superstructure, stretching the length of the ship.  The superstructure was around 50% of the hull width for much of the length of the superstructure, widening out to around 80% at the forward end.  Also note that the height of the superstructure was fairly short.  Combined with a low lying hull, the overall profile was quite short.

Fletcher DD

Note the very small superstructure on the Baltimore class cruiser shown below.   On a relative basis, there is more deck space than on the Fletchers.  Note that the available horizontal deck space allows the placement of large numbers of weapons.  There is also a large section amidships that has no superstructure!

Baltimore Class CA

Now, let's take a look at a modern destroyer, the Burke class DDG.  In contrast to the WWII designs, note that the superstructure is massively large and in most areas spans the width of the ship.  Excluding the flight deck which is not usable space, the only available large deck space is the bow area or top of the hangar which is only usable for equipment if there is no deck penetration.

Burke Class DDG

Look at the LCS.  Note that the stealthy, slanted superstructure spans the entire width of the hull and covers the deck from just behind the forward gun, all the way aft to the hangar.  There is no horizontal deck space in the area of the superstructure.  Also, note the relative height of the superstructure compared to the overall height of the ship from the bottom of the hull to the top of the superstructure.  Finally, note the width of the superstruture even at the very top.  It's still quite wide at around 80% of the width of the hull.  That's a lot of weight to carry quite high on the ship.  The bulky superstructure also makes the ship quite visible.

Freedom Class LCS

Even with stealth shaping, size still equates to radar signature.  The smaller the superstructure, the smaller the radar signature for a given shape.  Just as WWII sailors understood that a smaller superstructure translated to a smaller visual signature, so too does a smaller superstructure, today, translate to a smaller radar signature.

Another issue with large superstructures is top weight and stability.  A large superstructure means a higher proportion of weight higher up which negatively impacts stability margins.(distance the vertical center of gravity can shift in response to weight growth before stability is compromised).  Typical stability margins range from 0.3 m for amphibious ships to 0.8 m for carriers.  The LCS, for example, with its overly large superstructure, has a stability margin of 0.15 m - a very low value compared to other classes (1).

Another aspect of superstructure size is its impact on deck space and deck working space.  If the superstructure gets too large, the available horizontal deck space for mounting guns, boat cranes and storage, underway replenishment equipment, etc. becomes very limited.  Similarly, limited deck space impacts the working space for the crew, be it line handling, weapons operation, resupply, boat handling, etc.  Take a close look at the Freedom LCS.  It has very little usable deck space relative to its size.

WWII ships had plenty of horizontal deck space and mounted large numbers of weapons and equipment.  With modern slanted superstructures, deck space is at a premium and negatively impacts the number of weapons a ship can carry.  Often, it is necessary to carve out platforms higher up or on top of the superstructure which, again, impacts stability.  

Take a look at the LCS, for example.  The weapon pits, 30 mm gun mounts, etc. are at the top of the superstructure.  The problem with this is that it places the weight high up which makes the ship top heavy.  People talk about adding weapons to the LCS to make it more useful but such discussions overlook the fact that adding such weapons would be difficult due to the lack of deck space.  Mounting the weapons on top of the superstructure worsens the already marginal stability.

The Burke has a VLS cluster mounted on top of the hangar due to the lack of main deck space and that elevated mounting negatively impacts the stability.  

The modern trend of larger superstructures also results in more functions being placed above the main deck, in less armored (to the extent that anything is armored on modern ships) and less protected spaces.  Remember, unlike torpedoes, anti-ship missiles tend to hit the superstructure.  We are going to lose combat functionality by having more of it "exposed" in the superstructure rather than buried in the hull where armor, tanks, and void spaces help provide a measure of protection.

The odd part about the entire trend towards slanted, stealthy superstructures that span the width of the ship is that I've seen no evidence that narrower superstructures with more exposed deck space are any less stealthy.  I've read that vertical sides and bulkheads generate a significant radar return but I've never read a word suggesting that horizontal deck space generates a significant return.  If the sending/receiving radar were positioned directly overhead then the deck would constitute a perpendicular surface and would generate a large return but any other angle will just scatter the radar wave away from the sending/receiving unit and if the unit is directly overhead then the ship has already been spotted!

Admittedly, my understanding of ship radar stealth is rudimentary, at best.  However, until someone can demonstrate why a horizontal deck surface is bad, I've got believe that the benefits of additional deck space far outweight any supposed gain in stealth and the additional drawbacks to a slanted superstructure, such as top heaviness and lack of weapons mounting space, further reinforce that belief.  We need to re-examine the entire ship stealth concept as it relates to equipment, weapons, and sensor mounting.

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(1) Government Accountability Office, "LITTORAL COMBAT SHIP - Additional Testing and Improved Weight Management Needed Prior to Further Investments", GAO-14-749, July 2014

LCS ASW Update

Here’s an interesting tidbit from the DOT&E 2016 Annual Report (p.267) concerning the LCS ASW module development and testing.

“The Navy did not conduct any at-sea testing of the ASW mission package in FY16.”

Huh???  I thought the ASW package was settled and a vendor for the variable depth sonar, Thales, was selected and the module was in the final integration and testing stages.  I guess not.

What’s the hold up?  Apparently, it’s weight. 

“The Navy continued its efforts on a weight reduction program for the components of the mission package, including the handling system and support structures for the variable depth sonar and multifunction towed array.”

We’ve repeatedly noted that the LCS (both variants) are overweight and have no weight growth margins.  Every pound added to the LCS has to be balanced by a pound removed.  The LCS “growth” has become a zero-sum game.  In other words, growth is no longer possible for the LCS.

Regarding the VDS vendor selection, apparently that is not the settled issue I thought it was.

“The Navy anticipates downselecting to a single vendor for the variable depth sonar in FY17 and beginning a test program soon thereafter.”

To refresh your memory, the ASW module currently consists of

• Lightweight Tow torpedo countermeasure (a Nixie-like acoustic decoy)
• Multi-Function Towed Array
• Variable Depth Sonar
• MH-60R and MQ-8B/C Fire Scout VTUAV

The Navy hopes to begin testing in 2018 or 2019.  Assuming, optimistically, a typical few years of testing and a few more years to actually purchase production modules, we’re looking at 2025 or so before production ASW modules reach the fleet.  That’s a lot of time and effort for what will be a pretty anemic ASW fit.  Many LCS ships are going to live significant portions of their service lives without any modules.  

LCS Module Update

GAO’s 2015 annual weapons assessment report contains some interesting tidbits about the LCS modules (1).

ASW Module

Regarding the ASW module,

“Program officials report that currently the [ASW] mission package is 5 tons too heavy to fit within the parameters reserved for the packages.”

This is probably the most mature and useful module if only because the Navy abandoned every aspect of the original module and is now using proven, existing components:  a Thales variable depth sonar, a multi-function towed array, and a standard Navy helo.  The challenge is whether they can get the components to integrate in an effective manner.  Of course, the LCS can never be an effective ASW platform due to inherent structural problems that impact ASW performance:  the vessel is not quieted and optimized for ASW and the ship’s self-noise from the water jets not only precludes a hull mounted sonar but makes the ship an acoustic beacon for miles around.  Add to that the lack of an onboard ASW weapon and you have an extremely mediocre ASW platform.  Further, the inability to operate two helos (yes, some reports credit the LCS-2 version with the ability to operate two but that is questionable due to flight deck structural weaknesses) severely limits the extent of available helo ASW coverage. 

The Navy is currently contracting with three companies for ideas on how to reduce weight in the ASW module without removing a key component.  You know the process when things go through contracts and studies.  It will be years, yet, before we see a functioning ASW module.

MCM Module

Regarding the MCM module,

“The Navy has accepted five MCM packages without demonstrating that they meet interim—or threshold—requirements and plans to accept one more in fiscal 2015.”

As we know from various reports, the MCM module has proven particularly troublesome with most, or all, of the module components failing to meet their performance criteria.  Thus, the Navy’s continued purchases of MCM modules is puzzling, to say the least.  I guess it’s analogous to buying F-35s that are not ready.

Further, the Navy just announced that the MCM module would not reach its scheduled IOC in September due to across the board reliability issues discovered during testing.

“… LCS Mission Modules Program Manager Capt. Casey Moton said Thursday at a Mine Warfare Association lunch that across-the-board reliability problems in the two start-to-finish mine clearance runs in the technical evaluation led the program to extend the evaluation for several months rather than move prematurely to IOT&E.”

Independence, LCS-2, has been testing the MCM module for how long, now?  Since the mid-70’s, it seems like.  Despite all that work, the module reliability is still unacceptable.  How bad must the reliability be, to be unacceptable to the Navy?!  They’ve accepted barely built ships and F-35’s that have no combat capability.  For them to balk, it must be really bad!

It appears that IOC will be pushed back another year or so.

ASuW Module

The Navy has dropped the plan to use the incredibly short ranged and lightweight Griffon missile in favor of the Hellfire missile.  While there is nothing wrong with the Hellfire, it is still a lightweight, short range missile.  Wiki lists the range as 550 yds out to 5 miles.  It is doubtful that range holds for a surface, vertical launch.  The effective range will likely be more like 3-4 miles.  Also, note the minimum range.  If a target gets inside 550 yds the LCS will have to engage with guns which have, thus far, proven problematic.  The 30 mm guns have had a succession of maintenance and performance issues and the 57mm gun is inaccurate above 10 kts or so due to ship vibration.  Further, the guns are optically aimed and are not linked to radar in the ship’s fire control system.

USNI News has some disturbing news even about the Hellfire missile testing. (2)

“The program office began tests on a research vessel at the end of February against ‘high-speed maneuvering targets out off the Virginia Capes.’  That testing wrapped up in June, and based on the results, the office has to do ‘some tweaking – it’s really that level, tweaking – to the missile seeker and such.”

When you factor in the military’s ridiculously positive spin on testing – every test is an unqualified success, no matter how bad (remember the fabulously successful F-35B tests on the Wasp that actually barely achieved 50% availability? – you get the sense that the Hellfire has some serious issues integrating into a vertical launch system.  “Tweaking”, with the slight negative connotation it has, must indicate that the missile failed badly!  Getting a missile that is designed to launch horizontally to launch vertically, tip over, and acquire its target, is not a trivial feat without mid-course guidance.

The missile will have to undergo another set of tests several months down the road.

Here is GAO’s summary assessment in their typically bland style.

“The systems that comprise the Navy's mission packages have yet to work successfully together to achieve results. For example, none of the mission packages for any increment have achieved interim requirements on the Independence variant, or meet its threshold requirements for either seaframe.”

Remember, also, that the IOCs that the Navy is trying so desperately to achieve are not for the desired modules but for very stripped down versions that simply allow the Navy to field a bare minimum (many would say less than minimum) capability as a PR event.  The desired modules that the Navy sold the LCS program on are many years down the road or, more likely, will never be achieved.  Go back and read the original module descriptions to see just how much the modules have been dumbed down in the quest to get something, anything, fielded.  We’ve largely forgotten the grandiose promises made and have come to believe that the current, anemic versions of the modules are what was always intended.  Nothing could be further from the truth.  As a group, the modules are an utter and colossal failure.

Perhaps the most important point in the report, though, is this one,

“The Navy continues to procure LCS seaframes, even though the sub-systems necessary to meet full mission package requirements have not yet been fully developed, demonstrated, and integrated with either seaframe class.”

The LCS’s value and effectiveness, whether you support it or not, is predicated on the performance of its modules just as a carrier’s value is based wholly on its air wing.  An LCS without an effective module is just an overgrown Coast Guard cutter, if even that.  GAO points out that the Navy is proceeding full speed with seaframe acquisition in the absence of any useful and effective module.  The only module that even theoretically exists is the ASuW module and, let’s be real, an ASuW module that consists of a couple of machine guns and a RHIB is hardly useful or effective.

Worse is the Navy’s laser like focus on seaframes.  While the modules languish, seaframe construction continues unabated.  It would be nice if the Navy put the same effort into the modules as the seaframes and it would be even nicer if the Navy would recognize the importance of the modules.  No module, no useful LCS.  If the Navy isn’t careful, half the LCS seaframes will reach their end of life without ever seeing a useful module.  What a waste that would be (assuming you don’t consider the LCS to already be a waste!).

(1)Government Accountability Office, “Defense Acquisitions – Assessments of Selected Weapon Programs”, Mar 2015, GAO-15-342SP

(2)USNI, “LCS Anti-Sub Warfare Package Too Heavy; 3 Contracts Issued For Weight Reduction Study”, Megan Eckstein, July 30, 2015

http://news.usni.org/2015/07/30/lcs-anti-sub-warfare-package-too-heavy-3-contracts-issued-for-weight-reduction-study

Fat, Drunk, And Stupid Is No Way To Go Through Life

From the movie Animal House, "Fat, drunk, and stupid is no way to go through life ...".

While the LCS certainly seems to have been designed by drunk and stupid people, it now appears that the LCS is fat, also.

Weight growth margins have long been a known deficiency of the LCS.  While fairly well documented in the Freedom variant, the magnitude of the problem in the Independence variant has been less clear and many observers have assumed that the Independence variant had little or no weight problem.  Freedom, you may recall, had to have "water wings" (buoyancy tanks) welded on to the stern and they have been incorporated into subsequent ships of the class. 

Stability has also been a known problem for the Freedom class.  Module swap tests revealed that simply shifting normal container weights caused the ship to reach its allowable incline limits.

A new GAO report now sheds some light on the weight situation and provides some actual data (1).

The report notes that the ships have exceeded their expected weights with resulting impacts on performance.

"Weight growth occurred on the first four LCS seaframes, which affected the capabilities of both Freedom and Independence variant seaframes. This situation has led the Navy to accept lower than minimum requirements on two delivered seaframes (LCS 1 and 2) in endurance and sprint speeds, respectively."

From the report, affected performance parameters include,

• range

• sprint speed

• navigational draft

• service life allowance for weight

• stability

The report notes that range has already been significantly reduced,

"In 2009, the Navy received authorization from the Joint Requirements Oversight Council to reduce LCS’s original endurance requirement, which was a 4,300-nautical-mile range when operated at a speed of 16 knots, to the current endurance requirement. [ed: 3,500 nm at 14 kts]"

The report states that the service life allowance (SLA) weight is specified as 50 tons.  This is the required weight growth margin for future equipment additions to the ship.  Only two of the first six ships have met their specifications and the rest have missed by a substantial margin.  Listed below are the individual ships, their target SLA (tons) and their actual margin (tons).

LCS-1  50  26

LCS-3  50 156

LCS-5  50  67

LCS-2  50 -16

LCS-4  50  16

LCS-6  50  31

Only LCS-3 and -5 have met their SLA margins.  The rest have missed by a substantial amount.  Interestingly, the Independence variant seems to be significantly worse than the Freedom, contrary to what most people thought.

The report also provides data on the ship's full load weights (crew, stores, module) compared to their naval architectural limits (max allowable weight).  Full load weights that exceed the naval architectural limit risk damaging the ship due to excessive strains and stresses imposed by the excess weight.  Here are the full load weights as a percentage of the naval architectural limits.  The closer the ship is to 100%, the more the strain and stress.  Values over 100% risk damage.

LCS-1  99%

LCS-3  96%

LCS-5  98%

LCS-2 101%

LCS-4  99%

LCS-6  99%

None of the ships have any significant operational weight margins and LCS-2 actually exceeds the allowable limit. 

The report indicates that the Navy will operate LCS-2 at reduced fuel loads so as to reduce the weight to acceptable levels.  As equipment or additional crew (remember that the Navy has increased the core crew from 40 to 50 and will probably add more) is added, the remaining ships may also have to be operated at reduced fuel loads.

Further, the Navy is addressing weight concerns in the Independence variant by designing reductions in fuel capacity (hence, range) in future ships of the class,

"... the Navy is developing design modifications for Independence variant seaframes to reduce fuel capacity—estimated to total over 100 metric tons—in order to restore service life allowances."

The report notes that various ships have failed to meet their range and speed requirements due to excess weight.  This, after the range spec was already substantially reduced!

The specification for sprint speed is 40 kts but the report notes,

"LCS 2 contractor officials told us that the calculated speed in the full load condition LCS 2 is 36.5 knots."

Thus, the shining characteristic of the LCS, speed, which negatively impacts so much of he ship's design, is not even being met.  Yikes!  That's a double hit.

As if all this isn't bad enough, the service life allowances not only aren't being met but it turns out that the allowances aren't even up to industry standard.  As stated in the report,

"Complicating the weight growth on early LCS seaframes is the fact that LCS requirements for service life allowances already fall short of the growth margins called for under Navy and industry recommended practice."

Standards for other ship classes range from a low of 5% margin for amphibious ships to 10% for surface combatants.  The LCS target margin is only 1.5% to begin with.  So, in addition to not meeting the margin, the margin was ridiculously low to begin with.

Excessive weight also affects stability as demonstrated with the Freedom module swap tests.  Other ship classes have stability margins (distance the vertical center of gravity can shift in response to weight growth before stability is compromised) of 0.3 m for amphibious ships to 0.8 m for carriers.  The LCS stability margin is 0.15 m - again, a very low value compared to other classes.

Note that the current weights are with the very stripped down version of modules currently being procured.  As the modules gear up to their target requirements, the module weights will increase and this is already impacting module design and will get worse with time.  As noted,

"According to Navy officials, future additions to mission packages ... will be offset by removing existing systems ..."

Module weight limits may result in modules being developed in variations.  For example, the MCM module may not have all its equipment in a single module.  Instead, it may have to field variations of the module which have subsets of MCM equipment to meet weight limits.

What does all of this mean?  Well, beyond the obvious conclusion that the LCS design is a poor one, one of the major selling points of the LCS was that it would represent the ultimate in flexibility and adaptability over its service life.  This would be the ship that could be adapted and modified to accommodate future needs, thus keeping it relevant over its entire life.  Unfortunately, the reality is that the ship is severely constrained by weight issues and has little or no room for growth.  Module improvements - and let's be honest, improvements always mean bigger and heavier - will have to be severely restricted by weight limits.  Anything added to the ship will have to compensated by the removal of an equivalent amount.  This pretty much eliminates flexibility as a characteristic of this class.

Amazingly, the Navy is about to embark on this same weight limited path with the Burke Flt III.  Talk about an inability to learn a lesson!

(1) Governement Accountability Office, "LITTORAL COMBAT SHIP - Additional Testing and Improved Weight Management Needed Prior to Further Investments", GAO-14-749, July 2014

LCS - Bigger Crew Coming?

Most of us realized, after about 30 seconds of thought, that the target crew size of the LCS (about 40 for the core crew) was too small to operate, maintain, and fight a ship that size.  Because personnel costs are one of the major sources of life cycle costs, the Navy has tried everything possible to keep to the small crew size.  However, Michael Fabey of Aviation Week (article) reports,

"... according to a source intimately familiar with shipboard operations, the Navy has plans to increase the sailor count by 50% to 60 personnel this summer, and is studying the impact of further increasing the crew size to 150, close to the crew size on a a frigate, both to allow for the maintenance now being deferred, and to make sure the vessel can conduct combat operations."

So, the Navy is finally coming around and seeing what everyone else has known since the beginning.  Unfortunately, given the non-existent weight margins and constrained internal volume, installation of extra berthing, mess, laundry, showers, heads, food storage, etc. to support the additional crew will prove challenging, to say the least.

Hmmm .......  This ship is sounding more and more like a frigate - except for the total lack of weapons and sensors, of course!

LCS - Module Swapping



ASuW Module - 30 mm Gun

The LCS was envisioned to be a flexible and rapidly adaptable seaframe carrying customizable mission modules.  In fact, depending on which reports are to be believed, the LCS's high speed was less about tactical uses and more about high transit speed to and from the module swapping location.  Unfortunately, module swapping (not that there are any!) has proven to require two to three days of continuous work which kind of negates the flexible and rapidly adaptable portion of the concept.

Related to module swapping comes this tidbit from the Department of Defense Developmental Test and Evaluation and Systems Engineering FY2011 Annual Report, March 2012, p.67.

"While the MM [mission module] swap aboard LCS 1 was completed within the threshold time period, the stability limitations and tight quarters aboard the mono-hull seaframe became evident. In order to maintain the allowable list angle during movement of the 15,000 lb Remote Multi-Mission Vehicles (RMMV), the ship’s force needed to balance the ship by emptying a JP-5 fuel tank on the port side of the ship, and by placing a weight equal to that of an MH-60S helicopter on the starboard side. Changes have reportedly been incorporated into the LM design for LCS 3 and beyond that will increase stability and should eliminate the need for adding weight to accommodate mission packages."



Note that movement of a 15,000 lb object was sufficient to cause unacceptable list angles.  The LCS displaces 3000 tons.  A 15,000 lb object is 0.25% of the total displacement.  That's a pretty insignificant object to be causing stability issues.  One has to wonder how the movement of helicopters around the flight deck will be accomplished.



Testing the Mine Countermeasures (MCM) Module

So, once again we see a vessel that has serious weight (remember, buoyancy tanks had to be added to the stern) and stability issues which further complicate an already difficult and time consuming module swap procedure.

I think we're going to see far less module swapping than envisioned in the original concept.  In fact, there are signs that the LCS is moving towards a single purpose vessel with module swaps occuring only rarely.  More on this at a later time.