Monday, July 24, 2017

Enterprise Air Surveillance Radar

The Enterprise Air Surveillance Radar (EASR) is the radar system that is replacing the ill-conceived Dual Band Radar (DBR).  EASR is intended to replace the DBR on the Ford class carriers and the older rotating SPS-48/49 systems on a variety of ships.  It appears that the Navy intends the EASR to become the standard for non-Aegis ships such as amphibious ships, carriers, LX(R), and others.  Aegis SPY-x will remain the primary anti-air radar system for Burke class destroyers. 

Unfortunately, information on the EASR is scarce but naval-technology.com website offers a glimpse of the system (1).

Raytheon is developing the EASR and the Navy has conducted a Preliminary Design Review (PDR) of the system.

As with any new system, Raytheon/Navy claims that the new radar will perform better, be easier to maintain, require fewer personnel to operate, be more reliable, and cost less.  Of course, history assures us that most of these claims will turn out to be marginal improvements or totally false but at this stage of development, claims are typically unlimited and bordering on magical so this is nothing new or noteworthy.

The interesting aspect of this radar system is that it will be modular and scalable.

“The new air surveillance radar is designed on Radar Modular Assembly (RMA) technology, which has been matured through development and recent test successes of the US Navy’s AN / SPY-6 air and missile defence 3D radar for the DDG 51 Flight III destroyers.

Each RMA is a self-contained radar housed in a 2ft by 2ft by 2ft box, and the systems can be linked together to form radar chains of various sizes.

The EASR will be offered to the US Navy in two variants: Variant one, which will be a single face, rotating radar, and Variant two, which is a three face, fixed-array unit.” (1)

The concept of a rotating version is fascinating and leads one to wonder how and why it will be a significant improvement over the older rotating SPS-48/49 units?

EASR Variant 1 - Rotating


The system is, apparently, derived from the SPY-6 Air and Missile Defense Radar (AMDR) (2).  In fact, Raytheon claims that the AMDR and EASR are built with the identical AMDR cubical 2 ft. building blocks which leads one to wonder how and why the two systems are different and why we’re spending more money on an AMDR with a different name?

According to Raytheon, the difference between the systems is simply the number of RMAs, with the AMDR having 37 and the EASR having 9 (2).  As Raytheon describes it (2),

AMDR is comprised of 37 RMAs – which is equivalent to SPY-1D(V) +15 dB in terms of sensitivity. To give this perspective, it means that SPY-6 can see a target of half the size at twice the distance of today’s radars.

EASR is a 9 RMA configuration – which is equivalent to the sensitivity of the current SPY-1D(V) radar on today’s destroyers, and at only 20% of the size of the legacy SPS-48. These are considerable enhancements over the radars in service on current (and future) EASR-designated ship classes.


Raytheon stresses the reliability and maintainability of the system, citing the commonality between the AMDR and EASR due to the identical radar modules.

Raytheon also claims that the system will be more affordable due to having only a single radar type across the entire fleet.  They claim that training, logistics, spares, etc. will be streamlined and cheaper.

Of course, what new system in history hasn’t made those exact claims?  Some pan out, to a degree, many don’t.

So, if the AMDR and EASR are identical, differing only in the number of RMAs, why are we paying for an EASR “development” program?  From USNI News website,

“Radar maker Raytheon has been awarded a $92 million contract to develop a new Active Electronically Scanned Array (AESA) radar for the U.S. Navy’s new Ford-class carrier fleet and big deck amphibious warships, company officials told USNI News on a Monday conference call.

Based on Raytheon’s SPY-6 S-band Air and Missile Defense Radar (AMDR) planned for the services Arleigh Burke-class (DDG-51) guided missile destroyers, the Enterprise Air Surveillance Radar (EASR) will be the volume air search radar for most of the Gerald R. Ford-class carrier (CVN-78) — starting with John F. Kennedy (CVN-79) and the planned LHA-8 amphibious warship.

“It’s using identical hardware, identical signal processing software, data processing software.  It’s as near identical as possible. The goal of the program to drive affordability and commonality,” Tad Dickenson [Raytheon company spokesman] told reporters.”

Again, if it’s identical, why are we paying for a new developmental program?  It seems like $92M is a lot of money to simply change the number of RMAs.  But wait, there’s more money coming!

“Following the EMD phase, there are up to $723 million in contract options to support 16 ship sets of the radar – 6 fixed face for the Fords and 10 for amphibious ships.” (3)

And, of course, there’s always the actual construction/purchase funds still to be had! 

Interestingly, the EASR does not completely meet the Navy’s radar requirements.

“The service also plans to procure a separate X-band radar to compliment the EASR for both the future carriers and the amphibs.” (3)

I believe the separate X-band radar is intended to cover the low level, short range (horizon) region, meaning sea-skimming anti-ship missiles.  Currently, the SPQ-9B performs this function.

Raytheon has a nice little gig going for itself.  They’ve managed to direct the Navy into a single radar, sole supplier situation in which they can dictate unlimited prices and exorbitant “developmental” costs.  That’s nice work if you can get it!  The Navy now has no choice but to keep shipping barges of money to Raytheon.

There’s always the more mundane aspects of this arrangement to consider, as well.  If Raytheon’s facilities should suffer a major catastrophe like a fire or sabotage, the Navy will have no source for radars for, potentially, years while Raytheon rebuilds.  A prime target for sabotage at the start of a war with China, huh?  But, I digress …

In summary, the EASR seems to be just a renaming and repackaging of the already developed AMDR.  That leads to questioning the need for additional developmental funding.  Raytheon can’t have it both ways.  They claim the EASR is identical to the AMDR and, therefore, offers all kinds of commonality benefits and yet they want barge loads of money to “develop” the EASR.  Which is it?  Are the two systems identical or not?  I think the Navy is being gouged and has, through mismanagement, backed themselves into a no-choice corner.



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(1)naval-technology.com website, retrieved 8-May-2017,

(2)Raytheon website, retrieved 8-May-2017,

(3)USNI News website, “Raytheon Awarded $92M Navy Contract for Future Carrier, Big Deck AESA Radars”, Sam LaGrone, 22-Aug-2016,


Friday, July 21, 2017

Navy Issues Tanker RFP

The Navy has issued a draft Request For Proposals (RFP) to industry for the planned carrier based unmanned aerial tanker, the MQ-25A Stingray, and the RFP has some interesting points and aspects to it.

First, the RFP has only two key performance parameters (KPP) and both are generic to the point of useless.  They are:

  1. Carrier compatibility – the aircraft must be able to operate from a carrier and use existing catapult and recovery systems.  Duh.
  2. Mission tanking – the aircraft must be capable of aerial tanking.  Again, duh.

The Navy believes this will provide greater flexibility to industry and, ultimately, to the Navy when it comes to the design of the aircraft.  Personally, I think this approach is wrong.  I think performance parameters need to be specified – speed, range, endurance, reliability, fuel capacity, etc.  Without those specs, there’s no guarantee that you’ll wind up with an aircraft that can do the job.  Frankly, this is just the Navy passing design responsibility off to industry in an attempt to avoid accountability if the program tanks (no pun intended).

On the plus side, the Navy is indicating that development should be minimized by using nothing but existing technology.

“…the new airframe effort is less about developing new tech and more about mixing and matching existing systems to make unmanned tanking a reality on the carrier.” (1)

If the Navy can actually hold to this intent, this is a monumental leap forward in common sense acquisition practice.  There is nothing about aerial refueling that requires the development of new technology.  If the Navy can hold to this intent, the resulting costs and timeline should be quite reasonable.  Unfortunately, the Navy has a very hard time resisting gold plating programs after they’ve started.  It will be interesting to see whether they can restrain themselves.

On a related note, if the Navy can actually hold to this intent, it will make an interesting contrast to the Air Force’s tanker program (admittedly, the two programs are vastly different in scope and mission) which has been a dismal failure and this program could actually become an example for how to do acquisition.  As I said, we’ll take a wait and see approach.

I’m extremely ambivalent about an unmanned tanker.  Most of the claims for it are suspect or false. 

  • It won’t reduce manning much, if at all.  For every pilot removed from the cockpit, one has to take their place at a controller of some sort.

  • It offers no greater endurance because its endurance will be limited by the size of the fuel tanks it will carry.  Once the tanks are empty, the aircraft will have to return to the carrier just like a manned tanker would.

  • It offers no cost savings.  An aircraft is an aircraft.  If you want a plane that can travel x miles, at y speed it’s going to cost the same whether there’s a seat in it or not.  In fact, when the additional shipboard control stations are factored into the cost, it will probably be more expensive.

  • There will be inevitable in-flight aircraft failures, as with any aircraft, and without a crew to deal with it and attempt to remedy it, many aircraft may be forced to abort their missions.

  • UAVs have a solid historical record of crashing with some regularity.  The data on this is quite clear.  While losing a UAV is no big deal, losing a tanker affects many aircraft and missions.

Honestly, I don’t really see any concrete advantage to an unmanned tanker.  The only “advantage” is that the Navy gains experience in operating unmanned aircraft in preparation for the time when they try to operate unmanned combat aircraft and, to be honest, this alone may be sufficient justification for the unmanned tanker.

Overall, I like the start to this program.  I’m quite pleased that the Navy is going to at least attempt to produce an aircraft using nothing but existing technology for a routine mission.  If they can hold to the intent, it will be a major accomplishment and could set a pattern for future acquisitions.



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(1)USNI News website, “Navy Issues New MQ-25A Stingray Draft RFP to Industry Ahead of Final RFP in the Fall”, Sam LaGrone, 20-Jul-2017,


Wednesday, July 19, 2017

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

Monday, July 17, 2017

Famous Naval Movie Remakes

Remakes of famous movies are a staple of Hollywood moviemaking entertainment.  I’ve just learned that a series of famous naval movies are scheduled for remakes with a modern take on them.  Here’s a list of the movies along with a brief synopsis of the plots. 

In Harm’s Way – The inspiring story of courage against all odds.  Fighting off green energy task forces, a courageous Captain risks all to continue using incandescent light bulbs on his ship even in the face of overwhelming bureaucratic odds.

Run Silent, Run Deep – Rig for silent running as the creators of the LCS slip silently away, ducking responsibility depth charges and gaining promotions in the process!

They Were Expendable – The true story of the Spruance class destroyers that were sunk by the US Navy in a desperate attempt to stave off criticisms of the new Aegis system and eliminate any possible alternative.

Mister Roberts – A plucky lieutenant tries to look out for his crew while waging a tireless campaign to get the ship’s Captain to approve his transfer to a naval hospital for a gender change operation.

Crimson Tide – Suspense abounds as a submarine Captain and his Executive Officer clash over the wording of the PowerPoint slides they’ll use to summarize the sub’s patrol.  Mutiny ensues and the crew must choose sides:  the Captain wants Arial font and the XO wants Times New Roman.

The Enemy Below – An American destroyer Captain engages in a battle of wits with an Iranian submarine commander.  Watch as the American destroyer fires off volley after volley of strongly worded protests until the Iranian simply orders the American destroyer to stand down and be boarded, at which point the heroic American crew comply and are eventually released to return home to a hero’s welcome and medals for all the female crew members for just being there.

The Caine Mutiny  – A ship Captain is relieved for “loss of confidence in his ability to command” after an anonymous complaint from a crew member to the Navy’s 1-800-SQUEAL phone line accuses the Captain of miscounting the ship’s strawberry inventory.  The subsequent court martial reveals that, indeed, one can of strawberries was short a berry and Navy leadership congratulates itself on weeding out yet another unfit Captain.

Top Gun – A maverick pilot breaks all the rules as he battles the Navy and a caricature enemy before passing out in his F-18 due to oxygen deprivation in the climactic scene.

The Final Countdown – A freak storm sends a Navy carrier back to WWII where they learn that warships used to have armor and heavy weapons.  Stunned, they return to their own time and vow never to speak of what they have learned.

G.I. Jane – In an absurd bit of movie making, a woman breezes through SEAL training.  Oh wait, that’s not a ridiculous remake – that was the original movie!

An Officer and a Gentleman – A young man attends Officer Candidate School where he learns what it really means to be a Navy officer.  Watch as he learns to smile and salute while extolling the virtues of a non-functional weapons program, thwarts Congressional cost caps, masters the art of micromanagement, rises through the ranks by taking no chances, and ultimately retires to a well earned position on the board of a major defense industry company.

Operation Petticoat – This lighthearted WWII movie sees a pink submarine with an all female crew rescue a party of helpless men from the Japanese advance.  The ensuing hijinks show why men don’t belong in a modern Navy!

The Cruel Sea – A taut psychological thriller of life at sea.  Witness the cruelty of life at sea as the ship crosses the equator and the Pollywogs in the crew are forced to endure unimaginable hazing cruelties when the Shellbacks in the crew make funny faces at them.  Warning!  Some scenes may be too graphic for younger viewers as Pollywogs are politely requested to eat Jello blindfolded while being told that it is dragon’s blood.

Down Periscope – A misfit Captain and his crew take a submarine into a wargame, sink all the blue ships, and the results are ignored.  Oh wait, that was Millenium Challenge 2002, not a movie.


How about it?  Seen any good movie remakes lately that didn’t make the list?




Friday, July 14, 2017

Does Every Sub Need Tomahawks?

Here is a companion piece to the recent post, “Does Every Ship Need A Helicopter?” which examined US Navy design assumptions.  This time, we’ll take a look at submarine design.

One of the seeming absolute characteristics of a US Navy submarine design is the capability to shoot Tomahawk cruise missiles.  Here are the recent submarine classes and their possible Tomahawk loads.

Los Angeles  12
Ohio SSGN    154
Seawolf      50
Virginia     12-40

Without a doubt, having the capability to covertly shoot Tomahawks from submarines is a useful capability.  But, does every sub need to be able to shoot Tomahawks?

The question is not whether Tomahawk cruise missiles are useful but whether their usefulness is sufficient to justify the expenditure of ship’s volume, the concomitant increase in cost and the resulting decrease in number of submarines built?  The volume and money dedicated to a submarine cruise missile capability could go to other ship’s functions and to building more subs.  In other words, there is an opportunity cost associated with submarine launched cruise missiles.

Let’s look a bit closer.

Tomahawk missiles add size and cost to submarines.  The size increase is 20% or so, depending on the specific sub class and version.  The cost increase is harder to determine but one solid data point is the Virginia Payload Module (VPM) scheduled to be installed on the newest Virginias.  The cost increase is estimated to be around $500M which is a 20% increase over the base cost of around $2.5B.

By leaving out the VPM, we could build one extra Virginia class sub for every five subs built.  Are the added Tomahawks worth losing one extra sub for every five built?  To answer that, we need to recall the submarine’s mission(s).

The problem with “missions” is that people tend to assemble a laundry list and then, in discussions, assign by implication equal value to every mission.  For instance, here’s a partial list of submarine missions in no particular order.

  • Anti-submarine warfare
  • Anti-surface warfare
  • Long range strike warfare
  • Intelligence gathering
  • Special operations forces support
  • Presence
  • Cross training with foreign navies
  • Mine laying
  • Carrier group escort
  • Area denial
  • Blockade

As we examine the list of missions, we see that long range strike warfare is on the list.  Ergo, we must have Tomahawks on every submarine!  See what I’ve done, there?  I’ve equated every mission.  They are all equally important.  Therefore, they must all be incorporated into the design of any sub.  This is what we do today but it is wrong.

What we should be doing is prioritizing the list of missions.  We should be asking ourselves, what is the most important mission?  We might also ask ourselves what the most likely mission is – it’s often not the same as the most important!  If we do that then we can begin to intelligently design a submarine and make informed tradeoffs between cost and capability.

In war, a submarine’s most important mission is anti-submarine warfare according to US Navy doctrine since the Cold War – I’m talking about attack subs, SSN’s, not ballistic missile submarines.  The main job of our submarines is to eliminate the enemy’s submarines.  A close second mission, but still second, is anti-surface warfare.  Every mission after that is extraneous, in a sense.  If, by eliminating all the other missions – Tomahawk capability, in this case – we could build an extra submarine for every five we now build, would this be worth the loss of 12-40 Tomahawks (we’re talking about Virginia class subs, now)?  I suggest it would be and would be well worth it. 

Consider, of the 50 or so attack subs we’d like to have, we could have 10 extra subs if we dropped the Tomahawk capability!  60 subs vs. 50.  That’s a trade I’ll take!

But wait!  What about the loss of Tomahawk strike capability?  Well, that’s a significant loss, no doubt.  However, we have plenty of alternate Tomahawk strike capability in the form of Burkes and we could have much more if we took the retiring Ohio class subs and converted them into additional SSGNs with 154 Tomahawks each.  The subs are already built so it would just require the incremental cost to modify them to launch cruise missiles.  Wiki reports the conversion cost at around $700M per sub in mid-2000’s dollars.  Relative to ship building costs, that’s quite reasonable.


Submarine Launched Tomahawk - Is It Needed?


You’re asking yourself, how does an SSGN square with my previous mission list and stated priorities of ASW and ASuW?  Well, an SSGN has a different mission priority – pure cruise missile strike warfare – so the SSGN falls in line with the concept of recognizing what the priority mission is.

We see, then, that we could have more subs for the same cost and maintain or increase our fleet wide Tomahawk strike capability if we choose to spend a little bit more. 

Note, the cost of one LCS would just about cover the cost of converting one SSBN to SSGN.  Would you rather have one LCS or one Ohio SSGN with 154 Tomahawk missiles?

So, does every submarine need to have Tomahawk launch capability?  My answer is no.  The Navy needs to look at submarine CONOPS and rethink submarine design and numbers.  We need to abandon the every-ship-must-be-capable-of-every-mission thinking that now dominates our design philosophy.


Tuesday, July 11, 2017

Frigate RFI

The Navy has released its Request for Information (RFI) related to the frigate it apparently wants to acquire in place of the LCS.  Of course, we all recognize that the most likely “frigate” will be a modified LCS just as occurred the last time the Navy evaluated small surface combatants.  Nevertheless, let’s take a look at the RFI and see what bits of interest it holds.  You can read the RFI for yourself through the link below (1).

Of course, the first thing that should have already occurred is the development of a concept of operations (CONOPS) so that the Navy knows exactly what it wants the ship to do.  In fact, if they did that and had a solid idea of what the ship was intended to do, they’d already know what equipment it needs and would not need an RFI.  So, the fact that an RFI is even issued suggests that a CONOPS was not developed.  In fact, I’ve not heard a whisper of a frigate CONOPS.  So, the Navy already has strike one against it for this program.

Having failed the first step, there is an interesting statement in the introduction of the RFI that hints at the role the Navy sees for the ship.

The Navy is interested in the FFG(X) to provide Combatant and Fleet Commanders a uniquely suitable asset to achieve select sea control objectives and perform maritime security operations while facilitating access in all domains in support of strike group and aggregated fleet operations.”

Oops!  My bad.  That was just an incoherent grouping of buzzwords which someone inserted into the RFT to, presumably, try to seem intelligent and thoughtful.  Let’s try again.

“… this FFG(X) small surface combatant will expand blue force sensor and weapon influence to provide increased information to the overall fleet tactical picture while challenging adversary ISR&T efforts.”

Okay, now we have something.  This statement suggests that the Navy sees this ship as an information node and, interestingly, as an anti-information node as opposed to a warship.  This actually falls right in line with the Pentagon’s Third Offset Strategy which envisions beating enemies with uncontested and unhindered information rather than explosives.  It also falls in line with the recent post about the Marine Information Group.

This assessment of the ship as an information node is further supported by this statement.

“The FFG(X) will be capable of establishing a local sensor network using passive onboard sensors, embarked aircraft and elevated/tethered systems and unmanned vehicles to gather information and then act as a gateway to the fleet tactical grid using resilient communications systems and networks.”

So, this ship will be an information node and the mechanism will be via unmanned vehicles. 

Side note:  Is this beginning to sound an awful lot like the original LCS concept which envisioned the LCS as a node in a vast sensor network (yes, that really was the original LCS concept) enabled by modules consisting largely of unmanned vehicles?  But, I digress …

The RFI goes on to note that the ship will “aggregate” into strike groups during the run up to, and initiation of, hostilities.

The meat of the RFI appears in tables of desired characteristics.  Here’s a list of some of the more interesting ones.

Requirements

  • Operational Availability = 72%
  • Service Life 25 yrs
  • Shock hardening of propulsion, critical systems, and combat systems
  • Crew size = 200
  • Range 3000 nm @ 16 kts
  • Reserve power for future energy weapons
  • Max speed 28 kts
  • COMBATSS-21 combat control system
  • Enterprise Air Surveillance Radar
  • 1x full size helo plus 1x Fire Scout UAV
  • 360 degree EO/IR
  • Hellfire
  • SeaRAM
  • 8 cannister launched, over the horizon (OTH), anti-ship missiles;  type unspecified
  • Mk 110 57 mm gun

The RFI also notes that the Navy is very interested in understanding the trade offs required to incorporate ESSM/Standard AAW missile capability.

We see, then, that this ship will have only short range AAW self-defense unless someone can figure out how to include ESSM/Standard without breaking the budget.  This limited AAW excludes the frigate from escort duties, or at least the AAW portion of escort which is a major portion, to say the least!  Is it really a frigate if it can’t escort?

The absence of VLS cells limits the ship’s offensive and defensive flexibility.

We also see that the ship will have only a limited OTH anti-surface capability with only 8 missiles.  Still, a group of, say, 4-6 ships could generate a significant surface strike.

It’s interesting to note that the requirements for shock hardening, reduced speed, operational availability, and increased crew size all seem to spring directly from the failings of the LCS.  Maybe the Navy is capable of learning lessons?

One of the more disappointing characteristics is the very limited range.  A range of 3000 nm is not impressive against the backdrop of operations in a Pacific theater where bases are few and far away from relevant operating areas.  Maybe I spoke too soon.  Maybe the Navy isn’t capable of learning lessons?

The 57 mm gun????  It’s failed miserably on the LCS and the Zumwalt program dropped it.  Despite that, the Navy wants it for this ship?  The Navy is definitely not learning lessons!

I also see no mention of acoustic quieting that would be necessary for truly effective ASW and I see no mention of any on-board anti-submarine weapon for those shallow water, close up, unexpected encounters.  To be fair, this may be a level of detail not really appropriate for an RFI.

My overall assessment is that this is a somewhat beefed up LCS rather than a hard hitting, hard fighting warship.  The lack of even a medium range AAW capability is the most glaring shortcoming.

This ship also betrays a Navy mindset that has strayed from firepower and bought into the misguided belief in the primacy of information – almost for its own sake.

In short, the RFI is disappointing and will not produce a warship.



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(1) RFI: FFG(X) - US Navy Guided Missile Frigate Replacement Program
Solicitation Number: N0002418R2300, 10-Jul-2017,


Monday, July 10, 2017

Carrier Losses In War

USNI Blog has an article about carrier losses in a peer war and suggests that we should be prepared to lose around half within the first year (1).  The article goes on to suggest that we should be preparing to deal with replacement rates, environmental impact due to nuclear issues, and the impact of losses on subsequent combat operations.  This article jibes with a commonly held belief among many that carriers are highly vulnerable – essentially sitting ducks waiting to be sunk.

The problem with this article is that it looks at historical data and then projects the results to a modern war (with China, obviously, though the article does not specifically state that) without considering the circumstances of the historical data and the likelihood (or not) of those circumstances repeating themselves in a modern war with China.  This is the most cursory kind of analysis and leads, inevitably to incorrect conclusions.

The data is what it is.  The US Navy started WWII with 7 fleet carriers (I’m not counting Langley) and lost 4 of them in the first year of the war.  The article projects that loss rate to a modern war.  Is that a proper analysis?  Of course not!  Let’s look at the circumstances surrounding those WWII losses.  Here are a few key points.

  • Because of Pearl Harbor, the US started the war with no viable battle fleet and had ONLY carrier groups to fight the Japanese.

  • The Japanese were advancing rapidly across the Pacific.  If we did not stop their advance, we would lose all our forward bases.

  • Initially, Japanese battle fleet ships and carriers outnumbered Navy forces significantly.

Thus, due to circumstances, we had no choice but to try to stop the Japanese advance when and where we could and the only naval assets available were the carriers and our fleets would always be outnumbered.  The carriers that we lost were expended stopping the Japanese advance at Coral Sea and Midway.

How is this relevant?  Our carriers were not lost at random.  They didn’t just spontaneously sink.  The Japanese didn’t methodically hunt them down and destroy them.  Quite the opposite.  We carefully husbanded our carriers and committed them to high risk, major battles as necessary to stop the Japanese advance.  In other words, we knowingly and intentionally put them in situations where they were at great risk of being sunk.  Of course, what they accomplished before sinking is legendary but that’s not the point of this post.

Unlike the expectation of so many carrier critics and unlike the implication in the USNI blog article, carriers don’t just spontaneously sink and an enemy has very little ability to find and attack a carrier that is not, itself, committed to battle.  We had no unexpected carrier losses in WWII.  If we had opted not to commit our carriers to high risk battles, we wouldn’t have lost any!  Of course, we would have had a much harder time winning the war.  Similarly, if we opt not to commit our carriers to a modern battle, we won’t lose any!  But, is that any way to fight and win a war?

This gets back to circumstances.  In WWII, we had no choice but to commit to high risk battles to stop the unchecked Japanese advance.  Consider, now, the circumstances of a war with China.  At least for the foreseeable future, it is highly unlikely that the Chinese will attempt a wholesale advance across the Pacific.  Thus, the pressing need to commit to high risk battles in a desperate bid to stop an advance won’t exist.  A war with China is, in the foreseeable future, going to start at, and be fought around, the periphery of the South China Sea, a relatively contained and small region.  There likely won’t be a need to commit to desperate, high risk battles.  Thus, there likely won’t be high carrier attrition.  We’ll be in a much better position to pick and choose our battles as opposed to WWII.  The circumstances, which the article chose not to consider, will be vastly different!

The one possible exception to this is the Taiwan scenario.  I’ve stated that in any war with China, Taiwan will be the first act.  If the US commits to an immediate, and strategically unwise, retaking of Taiwan then we may well be forced to commit carriers to a high risk battle.

Another circumstance that would be different in a war with China than WWII is the initial number of carriers and surface ships.  Because of Pearl Harbor, we started with a severe shortage of ships.  Barring a modern Pearl Harbor, we will start a war with China with twice the number of carriers and our full surface fleet.  This will allow us to form proper carrier task forces (neglecting that each carrier will have a vastly undersized air wing!) with robust AAW protection in the form of numerous Aegis escorts.


Yorktown Sinking


We see, then, that the circumstances are everything when it comes to carrier usage and potential losses.  Carriers will sink only if and when we commit them to high risk combat.  Thus, the article’s prediction of losing half our carrier force in the first year of combat is logically unfounded because it fails to account for circumstances.

Okay, so far I’ve criticized the article but I’ve got to be fair and note that it brings up some good points and raises some good questions.  The article makes clear that carrier losses are inevitable unless the carriers are simply withheld from combat which would then lead to the obvious question, why did we bother building them?  Thus, we have to accept the fact that losses will occur if we commit carriers to battle.  That’s not a bad thing, assuming they accomplish suitably worthy tasks before they’re lost – it’s just part of the attrition of war.  However, this, in turn, suggests that we ought to rethink the current cost of carriers.  Do we really want to spend $14B+ on ships that can and will be lost in combat?  Might it behoove us to simplify carrier design and construction and get that cost down to a level that we can afford to lose, however reluctantly?

The article also raises questions about our ability to replace lost carriers, the environmental impact of sunken nuclear ships, our plan for carrying on the war when don’t have as many carriers, etc.

As the article suggests, we need to be able to “quickly” replace lost carriers which means, again, that we need to simplify carrier design.  Perhaps we ought to be building conventional, non-nuclear, “basic” carriers especially in light of the diminished air wing sizes.  We certainly ought to begin qualifying at least one other shipyard to build carriers. 

The article also suggests that we need to begin planning for how to continue combat operations when don’t have as many carriers as needed.  We need to game out naval strategies that are not dependent on carriers.

In summary, although the article completely misses the most important factor in carrier losses – circumstances – it does raise important questions and issues that we need to address now.




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(1)United States Naval Institute blog, “What Is Old Is Old Again - We Will Lose Carriers, and That’s OK”, CDRSalamander, June 14, 2017,


Saturday, July 8, 2017

Marine Information Group?

The Marines have been on a questionable foolish path for some time, now, with their focus on aviation and their shedding of tanks and artillery.  The push to become some kind of expeditionary air force and to drop from a middle weight fighting force to a light weight one is ill-considered and does not support the Marine’s main function which is to brutally and explosively seize an opening into an enemy’s territory to pave the way for follow on forces.

Now, the foolishness continues with the latest announcement of a name change for the Marine Expeditionary Force (MEF) Headquarters Group.

“On Thursday, July 6, the Camp Pendleton, Calif.-based I Marine Expeditionary Force Headquarters Group will be re-designated as I MEF Information Group.”

MEF Information Group????  It sounds like they want to be an ad agency, making up travel brochures.  This indicates a complete separation from reality and a total loss of recall about what the Marine’s purpose is.  If they want to rename the Headquarters Group, they should call it the Blowing Things Up Group because that’s what war is about.

Yes, I understand that cyber warfare, electronic warfare, and intelligence are part of the methodology of combat.  Further, I don’t really care what name they apply to anything.  What I do care about is the underlying mindset that leads to this kind of action – a mindset totally divorced from the recognition that war is a brutal, ugly, terribly destructive business.  Our military, and the Marines, in particular, seem to believe that war will be a dainty affair, conducted neatly from behind a computer, using spreadsheets and networks.  That notion will hold right until the Russians start dropping crude, primitive artillery barrages of high explosives and cluster munitions on top of our Information Group and all our light infantry joy-riding around the countryside in glorified jeeps.

“The commander of the MIG will be responsible to provide the MEF commanding general with a comprehensive understanding of the information environment, which includes the threat environment, command and control network health, status and vulnerabilities, the electromagnetic spectrum, cyberspace, environmental factors, cognitive and social factors, as well as further elements that may affect our ability to compete with near-peer adversaries.” (1)

Network health?  Environmental factors? Cognitive and social factors?  Are the Marines preparing for brutal combat or a high school debate?

The Marines seem firmly and enthusiastically headed down a rabbit hole of irrelevance and combat ineffectiveness and I’m very sorry to have to witness it.



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(1)USNI News website, “Primed and Ready: I MEF First to Organize Information Warfare Group”, Gidget Fuentes, 4-Jul-2017,



Tuesday, July 4, 2017

Torpedo Lethality Myth

This post is going to ruffle a few feathers.  It should be fun!

Let's see a show of hands.  How many of you think a torpedo kills a ship by breaking its back due to suspending the ship over a giant bubble of air?  Most of you raised your hands and the rest started to but hesitated because they sense a trap coming.

There is a widespread school of thought that a single torpedo hit spells instant doom for any ship in the world, no matter its size.  Thus, proponents say, there’s no sense applying armor to a ship – it would be pointless.  In fact, many of these people believe that adding armor increases the weight of the ship and, due to the greater weight, makes the ship more prone to breaking its back when suspended over the gas bubble formed by a torpedo explosion.  Presumably, these same people would advocate the thinnest sheet metal covering on a hull that is sufficient to keep out the ocean during normal sailing.  By logical extension, one would also have to assume that these people see no point in damage control measures because a single torpedo is an absolute guarantee of a sunk ship.

Well, this concept could not be more wrong and it’s time to learn why.  First, we’ll take a look at the characteristics of underwater explosions.  Then, we’ll examine the damage mechanisms associated with underwater explosions.  With that base of understanding, we’ll look at the specific case of a “broken back” by a ship suspended over an explosion created bubble.  Lastly, we’ll examine torpedo damage mitigation measures.

The foundation of this post is a review of scientific papers on the subject of underwater explosions.  Note that this is a blog post not a thorough and comprehensive review of every piece of scientific data out there – that would require a book length piece of writing.  That said, I’ve reviewed numerous papers and selected and referenced the ones that best illustrate the various relevant concepts.  I am also forced to summarize and, to a degree, simplify the scientific data for the sake of brevity and clarity.  For example, few of us are trained to understand the advanced mathematics contained within these types of papers nor do we care.  We are interested in the results – hence, my summations.  I’ve cited the references so you can peruse them if you are so inclined.

Underwater Explosion Characteristics and Behavior

An underwater explosion manifests two major effects:  an initial shock wave and a gas bubble. 

A gas bubble is created due to the formation of hot gaseous byproducts of the explosive chemical reaction.

“The underwater detonation of an explosive charge can best be described as an exothermic chemical reaction that is self-sustaining after initiation. Forming throughout the detonation process are gaseous reactive components that are at an extremely high temperature (approximately 3000 degrees Celsius) and pressure (approximately 50000 atmospheres). The entire detonation process represents a rapidly propagating reaction, with propagation speeds in the neighborhood of 25000 feet per second.”

As the gas bubble slowly forms (slow, on a scale of seconds), a shock wave propagates outward in all directions through the surrounding water.  The shock wave propagates quickly (fast, on a scale of milliseconds), relative to the gas bubble formation.

Shock wave pressure begins at a peak value and decays exponentially over time.  For example, a 250 lb HBX-1 explosive charge detonated at a distance of 50 ft from the target measurement point has a peak value of about 2500 psi and decays exponentially down to a value of about 850 psi in 0.62 milliseconds. (1)

After the shock wave passes, the gas bubble forms, expands due to the temperature and pressure of the enclosed gases, overexpands due to momentum, and then collapses back in on itself.  Similar to the overexpansion, the bubble over-collapses (over compresses the gases) and reforms and re-expands.  This cycle of expansion and collapse of the bubble occurs several times, each time less energetically, until either the entire bubble reaches the surface (it rises vertically the entire time since, like any bubble, it is less dense than the surrounding water) and vents or, if the explosion was deep enough, the bubble’s energy is dissipated and the bubble collapses a final time.

Each expansion/contraction cycle of the bubble generates an additional pressure wave (as distinct from a shock wave), the first, and largest, of which can be 10-15% of the peak pressure of the initial shock wave. (4)

There are secondary effects, as well, such as surface layer shock wave reflection, ocean bottom shock wave reflection, bubble-rigid surface jet effects, internal bubble reflective shock waves, etc., but from a ship damage perspective, these are usually of lesser import.

Keil presents a nomograph of maximum bubble radius as a function of explosive charge weight and depth of the explosion.  For explosions typical of a torpedo, say 500-1500 lbs charge and 30-50 ft depth, the resulting maximum bubble is 50-60 ft diameter. (5)  The bubble size is relatively insensitive to charge weight and depth within the range of expected torpedo charges and depths.  The most common torpedo charges and depths tend to produce a bubble around 50 ft diameter or a bit less.

Underwater Explosion Damage Mechanisms

Understanding the basics of an underwater explosion, we can now ask, what is the damage mechanism towards a ship?  According to Wardlaw and Mair (2),

“The 1D [ed.- one dimensional; a modeling technique] explosion exhibits two important damage mechanisms: the initial shock, and subsequent pressure pulses from bubble collapse and rebound.” (2)

Best (3) discusses the possibility of cavitation damage from high speed liquid jets that form on the side of a bubble opposite a solid surface and compress the bubble to a non-spherical form and eventually contact the solid surface.  The magnitude of this effect, if it holds in large underwater explosions, is unknown and it should be noted that this mechanism only applies if the bubble is in direct contact with a solid surface (ship’s hull).

Keil notes several damage mechanisms: (5) 

  1. Initial direct blast damage from the explosion itself if the explosion occurs in contact with the ship (torpedo or mine contacting the hull).  The size of the resulting hole and extent and degree of damage is a straightforward comparison of the explosive kinetics (crudely, charge size) and the various yield, tensile, sheer, and other properties of the ship’s plating (generally steel).
  2. Damage from the initial shock wave.
  3. Damage from the subsequent bubble pulses (cyclical expansions and contractions).
  4. Damage from the bubble water jet.

The magnitude and relative contribution of each type of damage is dependent on the location and depth of the explosive charge.

Keil (5) goes on to describe the mechanism of failure of the ship’s structural members.  The mechanism is one of sequential elastic flexing and relaxation of the strength members of the ship (bulkheads and longitudinal members) in response to the various shock and pressure waves.  If certain structural properties are exceeded, a permanent deformation of the hull structure will occur.  If those properties are exceeded by a sufficient amount, the deformation (flexing) cannot be recovered (relaxation) and the structural members tear – the iconic broken back scenario.  This is conceptually identical to the phenomenon of scoring a piece of metal and flexing it back and forth until it cleanly snaps.  Thus, the broken back is seen to be the result of repeated flexing of the structure.

Broken Back Scenario

Now that we understand the basics of underwater explosions and the associated damage mechanisms, let’s look at the widespread notion of a torpedo breaking a ship’s back by suspending the ship on a bubble of air.  For ease of typing, let’s hereafter call this the air break phenomenon.  Here is a conceptual illustration of the phenomenon.


Torpedo Back Breaking Myth


We’ve already noted that the damage mechanisms are direct explosive effects and shock waves of various origins.  I have not found any mention in any scientific examination of underwater explosions and damage mechanisms of the air break phenomenon.  Instead, the broken back phenomenon is explained by the rapid, repeated, elastic deformation (flexing and relaxation) of the ship’s structural members or the instantaneous application of shock wave pressure that far exceeds the structure’s various strength properties.

Still not convinced?  Let’s apply basic logic and see where that takes us.

First, a vessel must be just the right size and construction to even be susceptible to the air break phenomenon.  For example, a canoe can be lifted at each end and suspended in air indefinitely with no ill effect.  A Cyclone class PC (180 ft long) can be suspended and moved on slings near the ends of the vessel with no ill effect.  A super tanker or super carrier is too heavy to be “lifted” by a bubble of air.  So, in order for the air break phenomenon to occur, the ship must be bigger than a PC and smaller than a large tanker or aircraft carrier.  That would seem to limit the phenomenon to a destroyer size ship.

Let’s consider further the concept of suspending a ship over a bubble of air and breaking its back.  Intuitively, we all recognize that a one inch bubble of air under the hull of a ship isn’t going to break the ship’s back.  Why is that?  Why do we intuitively believe that a ship is immune to breaking its back over a one inch bubble of air?  It’s not just intuitive, either.  Ship’s encounter bubbles of that size under their hulls all the time from wave action, wake effects, etc. and don’t sink.  So, not only do we intuitively know a one inch bubble can’t break a ship’s back, empirical evidence proves it. 

Back to the question – why do we intuitively know a one inch bubble can’t break a ship’s back?  It’s because we understand, without needing any engineering calculations to back it up, that a one inch bubble doesn’t “suspend” enough of the ship’s hull to cause a problem.  The ship’s structure is sufficiently strong enough to withstand the stress of being “suspended” over a one inch bubble.  So, bubble size must be important in this purported phenomenon.  What about a one foot bubble?  No, that won’t break a ship’s back.  What about a ten foot bubble?  Hmmm …  No, that doesn’t seem likely.  Well, what size would cause a problem, then?  A hundred foot bubble?  Two hundred feet? 

Hey, while we’re speculating about the bubble size, I wonder how long a destroyer size ship is?  Well, a Burke is a touch over 500 ft and an LCS is around 380 ft.

Wait a minute!  If we’re going to “suspend” a destroyer size ship over a bubble and break its back, we need a bubble that nearly spans the length of the ship, right?  That means we need a near 500 ft bubble to break a Burke and a near 380 ft bubble to break even an LCS.  Wait …….  Wait …… I’m vaguely recalling a key piece of information from earlier ….

Didn’t we note earlier that for typical torpedoes (charge and depth) the resulting maximum bubble size was on the order of 50 ft?  Yes!  Yes, we did.  Is 50 ft enough to beak a ship?  Well, 50 ft is only 10% of a Burke’s length.  Does suspending 10% of a ship’s hull seem like it would cause instant, fatal damage?  No, that doesn’t seem believable.  Even for the LCS, a 50 ft bubble is only 13% of the ship’s length.  For a one thousand foot carrier, a 50 ft bubble is only 5% of the ship’s length.

I’m starting to think that the air break phenomenon may be a misconception.  The utter lack of scientific mention and the failure of the logical analysis suggest that the widespread belief that a ship’s back is broken by a bubble of air is false – a myth.

The final piece of the logical analysis is the videos we’ve seen of ship’s breaking in two during a torpedo test.  Going back over those videos, what we’ve failed to note is that the ships are thrust up, out of the water with their backs already structurally broken in an inverted “v” shape.  In other words, the structural back of the ship was deformed by upward pressure (or direct blast effects or the initial shock wave) not downward pressure as the air break phenomenon would mandate.  The broken back was not due to suspension over a bubble but by weak structural members deforming and snapping due to initial pressures, most likely the initial shock wave or direct blast effects.

There is no such thing as an air break phenomenon.  A torpedo cannot break a ship’s back by suspending the ship over a bubble.  A torpedo can certainly break a ship’s back but it’s not by suspending the ship over a bubble!  It’s from simple pressure effects causing deformation to the structural members that exceed the structure’s ability to resist or recover.

Having settled that question, let’s now look at the corollary.  Many people believe that a single torpedo is instant, unstoppable death to any ship of any size. 

Lethality and Mitigation

We’ve debunked the air break myth but there’s no denying that torpedoes are powerful and, often, deadly but are they instant death for any ship?  The answer to this is that the degree of lethality is almost wholly dependent on the size of the ship – the bigger the ship, the more resistant it is.  History bears this out irrefutably and I’m not going to waste much time on it.  The interested reader can peruse the various histories of ship sinkings to ascertain this for themselves.  A large tanker or super carrier cannot be sunk by a single torpedo or even a few.  It would take several, at least, to do the job.  Conversely, a destroyer (Burke) size ship might sink from one but would likely require two hits.  Smaller ships are likely single hit sinkers.

The more interesting and relevant question is whether anything can be done to mitigate torpedo damage.  Again, the “torpedoes can’t be stopped and are instantly fatal” crowd believes there is nothing that can be done to mitigate torpedo damage, so why even try?  Of course, nothing could be further from the truth.

Now that we understand the torpedo damage mechanism and the structural failure mode of the target ships, we can begin to develop torpedo resistant ship designs.  Note that this is not the same as “torpedo proof”.  It merely means that we can lesson the resultant damage from a torpedo hit just as we can lesson the damage from any other kind of weapon on land, sea, or air.  There’s nothing uniquely unstoppable about torpedoes.

Setting aside the active and passive torpedo defenses, there are design modifications that could and do impart inherent torpedo resistance.

Keil noted the use of bubble curtains to mitigate the effect of shock waves (5).  US Navy ships already have bubble curtains of a sort in the form of the Prairie/Masker quieting system.  Adapting Prairie/Masker to torpedo defense would not seem terribly difficult.

Keil also suggests that considerable underwater explosion damage resistance can be achieved by designing in a large degree of elasticity into the ship’s structure and plating as opposed to attempting to resist damage via increased hardening (5).  This illustrates the concept of designing the ship to absorb torpedo damage rather than trying to resist it.

On a related note, in hull panel testing, Rarnajeyathilagam and Vendhan (4) noted that concave panels offer better resistance to shock loads.  Thus, varying the geometry of the ship’s hull (round versus flat versus v-shape, etc.) offers a possibility of mitigating underwater explosion damage.  A concave v-shape hull may, then, mitigate underwater explosion damage.

A reasonable extrapolation of the concave geometry induced variation in shock resistance is the expectation that the degree of shock wave induced damage is dependent on the angle the shock wave strikes the target.  Just as a shell is more likely to ricochet from an angled hit or a radar wave scatters and reflects when hitting an angled surface, so too, does it appear that a shock wave is scattered and mitigated when striking an angled surface relative to the incident direction of the wave.  Thus, a flat bottomed ship design would seem to be the worst possible design for resisting under-hull shock waves.  Again, a curved or v-hull of some sort would seem to offer a degree of mitigation.

To belabor the point, a v-shaped hull on land vehicles is proven to mitigate underbody explosive effects.  An underwater explosion follows the same laws of physics as an explosion on land/air.  Yes, some properties are different, notably the density of air versus water, but the behavior is still governed by physical laws.  Just as v-hulls deflect land/air explosive forces, so too have underwater explosive forces been proven to be mitigated by properly shaped hull plates.  Thus, there is every reason to believe that a v-shaped ship’s hull would offer a degree of protection from underwater explosions.  Whether the degree of protection is sufficient to warrant any adverse effects on the ship’s overall seakeeping is unknown.

Void spaces, fluid filled tanks, and collapsible spaces have long been known to mitigate torpedo damage and ought to be a designed-in aspect of every warship.

Increasing the number and strength of the longitudinal structural members of a ship would greatly increase the overall resistance to shock.  Each longitudinal member acts as a mini-keel, tying the length of the ship together and transmitting the shock loads across the length of the ship rather than trying to resist the shock in just a few, localized spots.  Thus, even if the torpedo punches a hole in the hull, damage and flooding would be localized as opposed to breaking the ship’s back and outright sinking.

Armor belts and armored decks act as keels in that they are longitudinal structural members.  Large ships like battleships, carriers with armored flight decks, and heavy cruisers with armor belts and armored decks essentially have multiple keels.  Thus, the “loss” of the traditional keel (broken due to a torpedo) on the bottom of the ship is not even remotely a fatal event.  The remaining “keels” bind the ship together and each is capable of maintaining the structural integrity of the ship.  Of course, this only applies to larger ships.  Smaller ships do not have sufficiently strong and heavy enough belts and decks to constitute “keels”.

It is obvious, then, that torpedoes are not instant death to a ship and by understanding torpedo damage mechanisms we can design resistant ships of all types and sizes.  Again, this does not mean that ships can laugh off torpedoes.  What it means is that the degree of damage can be mitigated and offer the target ship a better chance to survive and continue fighting.


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This post also illustrates the danger in accepting truisms.  Not all are actually true!  We need to continually question our assumptions rather than blindly repeating them.  This also illustrates that conventional wisdom, even that "documented" on the Internet, may well be wrong.  



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(1)Naval Surface Warfare Center, “Underwater Explosion Phenomena and Shock Physics”, Frederick A. Costanzo, Feb 2010,

(2)Shock and Vibration, 5, ” Spherical solutions of an underwater explosion bubble”, Andrew B. Wardlaw, Jr. and Hans U. Mair, Feb 1998, p.89-102,

(3)“The Dynamics of Underwater Explosions”, John Philip Best, University of Wollongong, 1991

(4)Defence Science Journal, Vol. 53, No. 4, October 2003, pp. 393-402, “Underwater Explosion Damage of Ship Hull Panels”, K. Rarnajeyathilagam and C.P. Vendhan,

(5)“The Response of Ships to Underwater Explosions”, A.H. Keil, Presented at the Annual Meeting, New York, N. Y., November 16-17, 1961, of The Society Of Naval Architects and Marine Engineers,