ASW Drones

Unmanned is the fad of the day and using drones for anti-submarine warfare (ASW) is an idea that keeps cropping up.  So many people seem enamored with the idea and yet no one has examined the actual use.  Typically, proponents enthusiastically cite the usual drone characteristics, such as extended endurance, without understanding what that means … or doesn’t.  Let’s take a closer look and see if ASW drones are a good idea or not.
 
Let’s examine the characteristics, claimed and actual, of an ASW drone.
 
Endurance.  Proponents claim that the greater endurance of drones will revolutionize ASW, however, that ignores the reality that once any ASW aircraft, drones included, have expended their weapons/sensors they become useless regardless of their remaining endurance.  A drone with a month’s worth of flight time is finished as soon as its sonobuoys and/or weapons are expended.  It doesn’t matter how much longer it can fly.  ASW aircraft are sensor/weapon limited, not endurance limited.  Thus, drones offer no advantage and, in fact, depending on the exact drone, would very likely have fewer sensors/weapons than a manned aircraft and would, thus, have LESS effective endurance than a manned aircraft!
 
Signal Processing.  Manned ASW aircraft such as the S-3 Viking, P-3/8, and helos carry on-board computers and analysts to interpret the sensor signals.  Drones have no on-board analysis capability and must continuously communicate with the host ship.  This is a continuous, broad band transmission which is highly susceptible to detection and localization by the enemy.  The host ship, in turn, has to broadcast control signals to the drone.  Elementary analysis of the locations of drones performing ASW reveals the likely location of the host ship to the enemy.
 
Size and Operation.  Proponents never quite specify the size of the drone they’re calling for.  There are only two possible drone platforms, currently:  Burkes and amphibious ships.
 
The reality is that destroyer size ships (like a DDH) have no large flight deck or recovery area and are limited to something in the Scan Eagle size (5 ft long, 10 ft wing span, 30-40 lb empty weight, 11 lb payload) or the somewhat larger helo-type UAV such as Fire Scout.
 
Helicopter carriers could operate larger drones but even they have limits.  For example, the Wasp class LHD has a [roughly] 104 ft wide flight deck.  A commonly cited drone is the MQ-9 Reaper and I'm moderately sure that, in theory, a 1000 ft x 104 ft flight deck would allow a Reaper to take off. The caveat is that the Reaper does not have an immensely powerful engine so the acceleration might, actually, turn out to be insufficient. That would have to be tested but, for the sake of further discussion, let's assume it could take off.
 
More problematic is that the Wasp island extends close to half way across the flight deck amidships. That reduces the usable flight deck width to around 50 ft, at that point. The Reaper has a wingspan of 65 ft. which puts the nose wheel at 33 ft from either wing tip. Allowing for, say, 10 ft of wing tip clearance from the island (the Navy would probably insist on a greater safety margin than that), that would put the nose wheel 43 ft away from the island which would be within 10 ft or so of the deck edge. That, in turn, puts the wing wheels within a few feet of the deck edge. The slightest deviation and the aircraft is off the edge! In short, it would seem that the full length of the deck cannot be safely used. That leaves only a few hundred feet forward of the island for takeoffs. Now, I'm really not sure an unassisted takeoff is possible!  In fact, it seems unlikely.
 

Wasp Class - note the island extending into the flight deck

So, a Reaper would be the maximum size drone that could operate off a big deck amphibious ship with catapults and arresting gear and it’s likely even that is too big. 
 
Of course, we could purpose design a drone carrier that could operate large UAVs but that would be decades down the road and, likely, unaffordable if we continue buying $20B Fords.
 
Then, there's the issue of storing/hangaring large UAVs (Reaper is 36 ft long x 65 ft wide, for example). It would need some serious wing folding to get an acceptable spot factor so that we could operate more than one UAV.
 
Carrier Adaptation.  Adaptations such as beefed up landing gear, arresting hooks, folding wing mechanisms, etc. all add weight to the aircraft and negatively impact already limited payload capacities as well as unaided takeoff and landing distances.
 
Payload.  To give some frame of reference as we talk about drone payload capacities, here are some relevant sensor/weapon weights:
 
Sonobuoy - 35-40 lbs, depending on specific type
Torpedo - The Mk54 lightweight torpedo weighs a little over 600 lbs.
 
What is a useful payload size and composition?  A reasonable minimum would be something on the order of 40 sonobuoys and 2 lightweight torpedoes.  Thus, a payload of two torpedoes plus 40 sonobuoys = 2800 lbs without launchers, pylons, and associated equipment.
 
Drone payload capacities vary widely, depending on the size of the aircraft.
 
Drone Types.  With the characteristics we just discussed in mind, let’s now review the basic drone types and see how they mesh with the characteristics.
 
Small.  Small UAVs, such as Scan Eagle or RQ-21 Blackjack size, can operate off destroyers.  The drawback is that they have a very small payload to the point of being incapable of effective ASW work.
 
Scan Eagle, as an example, is very small and has a mere 11 lb payload capacity.  A standard A-size sonobuoy is around 5” diameter x 36” long and weighs 39 lb.  A Scan Eagle size drone couldn’t even carry one sonobuoy! 
 
Medium.  Intermediate size UAVs such as the vertical takeoff and landing MQ-8B Fire Scout has a theoretical maximum payload of around 500 lbs, however, the practical payload is around 100 lbs.  Thus, it could not carry even a single torpedo and only a few sonobuoys.  This is simply not an effective payload. 
 
The larger MQ-8C Fire Scout has a maximum theoretical payload capacity of around 700 lbs with a practical payload of around 300 lbs. 
 
These drones are capable of operating off a destroyer but cannot carry a combat-useful payload.

Fire Scout

Large.  Larger UAVs such as the MQ-9 Reaper, Predator, Global Hawk, etc. have payload capacities that begin to be useful but they require actual aircraft carriers with catapults and arresting gear to operate from.  The MQ-9 Reaper, for example, has a theoretical maximum payload of 3800 lbs and a practical capacity of around 1000 lbs on a wingspan of 65 ft and a length of 36 ft. 

 
 
Land Based
 
So far, we’ve limited our discussion to ship based drones but land based drones are also an option.  While concerns about takeoff/recovery are not an issue, payloads, effective endurance, and signal processing communications are and still impose limitations.
 
Presumably, most naval operations will occur well out to sea (thousands of miles) which is certainly within reach of large UAVs (noting, of course, the inverse relationship between payload and range/endurance!) but is not a tactically responsive situation.  For example, a surface group that requests drone ASW support will have to wait many hours for a response under even the best of circumstances.  Land based ASW aircraft, whether manned or unmanned, are best employed as a base defense rather than as a task force support asset. 
 
Attempting to supply a constant ASW presence using land based aircraft would require a constant stream of aircraft flying to and from the operating area.  It would require something on the order of a dozen aircraft to maintain one continuously – and effectively – on station.  Remember, that in a war, sonobuoy and weapon usage will be staggering and all the endurance of an aircraft will be rendered moot as the aircraft quickly empties its payload and is rendered ineffective.
 
 
Conclusions
 
1. Very small drones can operate off destroyers but are incapable of performing any effective ASW due to payload limitations.
 
2.  Larger, vertical takeoff UAVs can operate from destroyers but, again, their payloads are so limited as to render them nearly useless and not worth the support and operating effort.
 
3. A big deck amphibious ship for moderate size UAVs is feasible although they would likely need to have catapults and arresting gear.  Again, there are payload concerns although they begin to approach a somewhat useful load.  This is an expensive option.
 
4. Land based ASW drones could possibly carry a useful payload but are tactically inefficient and are best relegated to patrolling around their base.
 
5. A reasonable alternative would be to modify a large commercial vessel to operate large UAVs by eliminating/minimizing superstructure and adding a long flight deck.  This would likely be the cheapest and best option.
 
 
Considering the above conclusions, it is hard to visualize effective, efficient ASW drones.  They simply don’t have the characteristics necessary to perform combat-effective ASW.  In other words, there is no viable CONOPS for ASW drones.  Further, given that we have existing ASW helos and P-8 Poseidons, one has to wonder why so many people want to force fit drones into a task they are clearly not suited for.

Industry Design

The recent book review post about Electronic Greyhounds noted that the Spruance class was the first ship designed wholly by industry instead of the Navy/BuShips.[1]  This was a radical departure from previous practice and has since become the Navy’s standard practice for ship design.  The subsequent evidence would seem to demonstrate that this is a very bad practice.
 
In theory, there are some potential benefits to an industry-design approach.  The primary advantage would be that industry might have a greater concentration of expertise.  Of course, until it was eliminated, BuShips had a concentration of expertise.  Expertise is simply a matter of ‘doing it’ on a regular basis.  There is no reason to believe that an in-house Navy design group would not be every bit as capable as industry and, indeed, BuShips proved that for decades.  In fact, since every ship would pass through the in-house group, they would accumulate more experience and expertise than industry which would only get to work on an occasional Navy project.  In fact, this ‘occasionality’ manifested itself in the LCS designs which saw not one but (if you can believe it!) two companies design and build warships despite never having done so previously.  Not exactly a concentration of expertise, was it?
 
On the flip side, a highly likely potential drawback is that there is no guarantee that industry will produce a good design (hi, again, LCS!), leaving the Navy to choose between a bad design or cancellation of the project which, given the budget implications, is assuredly never going to happen.  The Navy would much rather [irresponsibly] accept a bad design than risk losing budget money as would happen if the project were terminated.
 
There is also no guarantee that the design will be useful.  Admittedly, this is a shared responsibility between industry and the Navy with, perhaps, the bulk of the blame lying with the Navy which refuses to develop viable CONOPS prior to design in order to ensure usefulness.
 
In addition to risking a poor industry ship design, the loss of in-house expertise has resulted in the loss of institutional knowledge within the Navy about what makes a good ship.  This has resulted in NavSea having no ability to recognize flaws in a design, despite being tasked with exactly that responsibility.  Blindingly simple and obvious examples include the failure to provide cathodic corrosion protection (known and understood since the age of sail) and the omission of bridge wings (standard since … well … forever) in the LCS.  Slightly more advanced failures include inadequate stability and weight growth margins.  The Navy no longer possesses the ability to even recognize a good or bad ship design.
 
 
Examples
 
Let’s briefly consider a few examples of industry designs.
 
LCS.  The sheer number and severity of the changes made to both LCS variants attests to the lack of design expertise resident in both the Navy and the manufacturer.[2]
 
Ford.  The Ford catapult, arresting gear, elevators, weapons, toilets, dual band radar, etc. should never have gotten past the napkin stage of design.
 
Montford Point.  The Mobile Landing Platform is an example of a [apparently] technically decent design that is utterly useless with the ships having already been retired for all practical purposes.
 
Zumwalt.  The Zumwalt is a poor design (seakeeping, electrical system, hull design, non-existent close in weapons, etc.) which is also useless (no main weapon and no viable mission).
 
Burke.  The Early Burkes were barely adequate designs (insufficient close in weapons, no hangar, weak structure, etc.) that were improved somewhat in the Flt IIa and are now sub-par with the Flt III (inadequate margins, stability/weight challenges, sub-optimal radar, etc.).
 
Since some of you are already pounding out replies trying to put all the blame on poor Navy requirements, let me repeat, the poor designs are a shared failing and, depending on the specific case, the fault may lie more with the Navy than industry.
 
 
Spruance
 
In contrast to the preceding designs, the Spruance, as it turned out, was an outstanding design but there was no guarantee that would be the case.  It could just have easily been a poor design and the Navy would have had little choice but to accept it, having ceded all responsibility to the manufacturer.  The Navy gambled and got lucky.  However, depending on luck is not the way to design ships.  Unfortunately, the Spruance was the last good industry design and the Navy has had to accept a string of poor designs ever since. 
 
 
Conclusion
 
History and logic clearly demonstrate that ceding ship design responsibility to industry is a poor practice.  While the possibility of producing a good design exists, the long line of failures makes it clear that the odds of success are very poor.  To be fair, the Navy does everything they can to ensure a poor outcome with constant design changes, idiotic and conflicting requirements, absence of CONOPS, and utter lack of expertise with which to spot and correct problems at the design stage.  To be additionally fair, industry is responsible for basic failures such as inadequate structural strength, overly complex machinery (does anyone know how to design a functional combining gear????), unrepairable machinery (EMALS, for example), missing cathodic protection, stability issues, inadequate margins and allowances, incorrectly calculated weights and metacentric heights, toilets that don’t work, poorly located sensors, rampant stress cracks, and so on.
 
As we discussed, the inability of industry to produce a good design is just half the problem with industry being tasked with design.  The other half is the loss of the Navy’s in-house expertise to the point that they can no longer even spot a flaw in a design.  By ceding design responsibility, the Navy has rendered themselves deaf, dumb, and blind regarding designs.  The Navy has created a fatal dependency (addiction) on industry and are now trapped into accepting whatever garbage industry pukes out.
 
Finally, let me once again repeat, the Navy contributes heavily to poor designs with their idiotic requirements and constant change orders.
 
We absolutely must reconstitute BuShips and return ship design expertise to the Navy.  We cannot afford to keep producing failure after failure.  The Navy has become so gun shy about new ship designs that they would rather continue building obsolete Burkes and Constellation mini-Burkes than risk a new design.
 
Bring back BuShips!
 
 
 
______________________________

 
[1]Capt. Michael C. Potter, USNR, Electronic Greyhounds, The Spruance-Class Destroyers, Naval Institute Press, 1995, ISBN 1-55750-682-5
 
[2]Military.com website, “Navy Engineers LCS Changes”, 27-Jun-2014,
https://www.military.com/dodbuzz/2014/06/27/navy-engineers-lcs-changes

Happy Thanksgiving!

Happy Thanksgiving to all the American readers!  Enjoy family and friends and recall all the blessings you have to be grateful for.

DDH Hayler

Helicopters have long been recognized as one of the most effective anti-submarine (ASW) assets and ASW surface ships have routinely carried one or two helos for that specific purpose.  The problem with ship based helos is that the limited number (1 or, at most, 2) guarantees very limited coverage.  Helos are notorious for maintenance challenges and a ship with, say, two helos can be expected to have perhaps six to eight hours of airborne ASW coverage per day, on average.  One potential solution is to increase the number of helos on a ship thereby creating the aviation (helo) destroyer (DDH).  One such effort was the Spruance DDH 997 derivative, the USS Hayler.
 
Litton, the designer and manufacturer of the Spruance class, proposed a DDH 997 Spruance derivative with a hangar lengthened by 40 ft and widened to the full beam of the ship thereby allowing it to accommodate 4 SH-60B Seahawks.  Curiously, the flight deck remained sized for a single helo and precluded simultaneous flight deck operations by multiple helos.
 
In the event, the DDH version of the Hayler was never built.
 

DDH Hayler Design

Image from www.shipbucket.com,

MhoshiK, Mconrads, Hood, J. Scholtens

 
Destroyer Helo ASW Operations
 
Just as the value of an aircraft carrier is wholly dependent on the abilities of the air wing, so too is the value of a DDH dependent on the abilities of the helos.  With that in mind, let’s take a closer look at small number helo ASW.
 
Four helos might seem an ideal solution to providing helos for ASW as one might assume that a 4-helo ship could maintain one helo in the air continuously.  However, even if that were possible, that’s not really the way helos would be used in ASW operations.  More typically, helos would surge to a suspected contact which, regardless of the outcome, would then result in multiple helos being ‘down’ for some significant period of time and result in gaps in the desired 24 hour coverage.  Of course, this assumes that multiple helos were available to surge.
 
One also needs to recognize that a single helo, assuming one could keep one helo in the air continuously, is only marginally effective at detection.  The helo’s sonobuoys (whether dropped or dipping) are short range and the area/volume of ocean to be covered around a ship or surface group is immense and ever changing due to the movement of the surface ship/group.  Helos are highly effective at prosecuting contacts but much less effective at detecting submarines in a ‘cold’ search effort.  Ideally, one would like to detect possible contacts with surface ships, at long range, and then use helos to prosecute the contact.
 
As we consider the operation of ASW helos, we need to bear in mind what the definition of an ‘available’ helo is.  First, and foremost, it is a helo that can fly;  no easy task given helo maintenance needs!  Second, the helo needs to have the requisite weapons to be effective.  For example, a helo that drops both its torpedoes is, instantly, toothless.  Yes, it can still search and track a contact but it can’t do anything about it.  Two lightweight torpedoes is not a lot when dealing with a submarine.  In other words, in combat, when torpedoes will be dropped at a profligate rate at any marginal contact, four helos with just 8 torpedoes is not going to provide much effective coverage.  Helos will have to spend much of their time shuttling back and forth to a ship to reload torpedoes.
 
Of course, helicopter ASW is a numbers game.  To be ridiculous, if one had forty helos continuously searching the surrounding area/volume, they would likely be fairly effective.  However, that’s unrealistic.  What would be realistic is a squadron of, say, four DDH vessels with, in that case, 16 helos.  In the case of a convoy or task force, there might well be several to dozens of DDH escorts which would, indeed, provide useful numbers of helos, in the aggregate.
 
Recognizing the importance of numbers in the ASW helo game, this leads us to the true ASW helicopter carrier of which there are, have been, many examples.  The main characteristic of the helicopter carrier is, of course, the capacity to carry and operate large numbers of helos.
 
 
 
Other Examples
 
The Japanese developed two 2-ship DDH classes, the Haruna and Shirane, which could carry three SH-60 type helos while retaining conventional destroyer weapons and sensors.  I’m unaware of any other examples by any other countries.  It is interesting to note that the Japanese produced the two mini-classes and then abandoned the DDH for helicopter carriers in the form of the succeeding Hyuga class.  I do not know what the rationale was but it suggests that the DDH was found to be less effective and efficient than a true helicopter carrier.
 
There have been numerous examples of ASW helicopter carriers but that’s not what we’re looking at in this post. 
 
 
Conclusion
 
It seems clear that the DDH concept has limited value due to the limited number of helos unless the ships are grouped in fairly large numbers.  That being the case, one has to wonder whether the cost of fielding several to dozens of DDH’s could be better spent on a true ASW helicopter carrier.  A helicopter carrier with, say, 18-24 helos would be the equivalent of 4-6 DDH’s.  At a very optimistic $1B per DDH, that would equate to $4B-$6B available for a helicopter carrier.  At a more realistic cost of, say, $2B per DDH, that would equate to $8B-$12B which would allow two to several helicopter carriers for the price of the DDH’s, depending on the degree of commercial adaptation incorporated into the carrier design (a large merchant ship with a flat deck would suffice!).
 
It is also clear that the tactical use of ASW helos is not so much searching as fixing and attacking.  This suggests that if one did want to build a DDH, the ship’s ASW sensors would be just as important as the helos, themselves, as they would be counted on to provide the initial detection.  This means that the DDH design should be a highly specialized, intimately integrated ASW design, as opposed to a mere flight deck on a hull as was the case for the LCS.
 
The lack of actual DDH designs in naval history suggests that the navies who considered the concept found it wanting for whatever reasons.  Our analysis suggests this is the case.  A DDH could, under the right circumstances and with a carefully considered CONOPS, be useful.  Unfortunately, carefully considered CONOPS are not a characteristic of the US Navy.
 
The DDH would seem to have some potential but, overall, the resources would be better spent on ASW helicopter carriers.
 
 
 
______________________________

 
[1]Capt. Michael C. Potter, USNR, Electronic Greyhounds, The Spruance-Class Destroyers, Naval Institute Press, 1995, ISBN 1-55750-682-5

Open Post

It's been while since the last open post so let's do it again.  This is your chance to offer a comment on whatever interests you.

Got a suggestion for a post topic?

Want to talk about something that's been neglected?

Want to tell me what you'd like more (or less) of?

Want to tell me how you'd make the blog better?

Want to give a shout out to your favorite foreign ship design?

Got a rant you want to get off your chest?

Have at it!

Radar – Rotating vs. Panels

We previously compared vertical launch systems (VLS) to arm launchers (see, “VLS Versus Arm Launchers”) and concluded that VLS was not quite the unquestioned advantage that it was claimed and assumed to be.  Similarly, we’re now going to compare rotating radars against fixed, flat panel arrays which are assumed to be infinitely superior.
 
One of the major developments in naval sensors has been the advent of flat panel radar arrays.  The panels are mounted on the sides of the superstructure with, typically, 3-4 spaced around so as to provide 360 degree coverage, each panel covering 90-120 degrees.  This architecture is assumed to be hugely more beneficial than conventional, rotating radars, presumably due to the elimination of moving parts as well as the simultaneous improvement in radar technology, generally.  Is this assumption of superiority valid?  Let’s see.
 
Let’s start by understanding the three basic types of radar configurations:
 
Conventional Lattice – These are typified by the SPS-48/49 which are modern versions of the classic, mechanically steered, rotating radars with a lattice framework.
 

Wasp class with SPS-48 on the right and SPS-49 on the left

Hybrid Panel – These place flat panels on a rotating assembly to produce a hybrid rotating panel.  Examples include the TRS-3D which rotates at 10, 17, 20 or 60 revolutions per minute (rpm) [1] or the TRS-4D which rotates at 15, 30 rpm [2].  Both are quite capable.
 

TRS-4D is a G-Band three-dimensional, multi-function naval radar for surveillance, target acquisition, self-defense, gunfire support, and aircraft control. It is a software-defined radar using a rotating version of the active electronically scanned array (AESA) with multiple digitally formed beams. …
 
The TRS-4D radar simultaneously conducts a three dimensional search of the air space volume and sea surface area around the ship. … The transmitter modules in the active antenna are solid-state modules in Gallium Nitride technology. The radar allows a graceful degradation of the transmitted power depending on the required maximum range.
 
The MRESR version of the TRS-4D was installed on US LCS ships of the U.S. Navy’s Freedom class. It was designated by US Navy as AN/SPS-80.[2]

TRS-3D

 
Another example of a hybrid panel radar is the SPY-6(V)2 which is intended to be installed on amphibious ships and Nimitz class carriers.
 

SPY-6(v)2

Panel – These are the ubiquitous flat panels found on US ships and include the various Aegis SPY-1 variants, SPY-6 (Air and Missile Defense Radar, AMDR), SPY-6(V)3 Enterprise Air Surveillance Radar (EASR), and whatever other names they’re known by.
 

Flat Panel

Advantages and Disadvantages
 
Simplicity.  Flat panels are mechanically simpler in that they have fewer moving parts although, to be fair, a motor and some bearings to rotate on are not exactly rocket science in terms of complexity.  Still, no movement is undeniably simpler than rotating.
 
Of course, rotation is not the end of the simplicity story. 
 
Both types require sophisticated, complex computers/software to control and process the signals so that’s a wash.
 
What isn’t a wash is the extent of electronic and utility support that a panel requires.  Each element in a panel requires its own power, computer connections, data and computer control connections, and cooling support.  A rotating radar requires much the same but only a single instance of each, as opposed to an instance for each element of the array.  Notably, rotating radars do not require cooling which is a major requirement.
 
Further, the individual modules that make up a panel are quite complicated and there is no hope of repairing one aboard ship.  On the plus side, they can be swapped out without too much difficulty, as I understand it.  Similarly, the ‘guts’ of a hybrid panel are similarly complex.  The conventional lattice is, of course, as simple as it gets.
 
Volume.  Rotating radars are essentially external to the ship whereas panels require significant amounts of internal ship’s volume to house the array elements and support equipment.  Further, panels typically exist as 3-4 repeated installations, each of which requires its own, equal, large amount of ship’s volume to house it.  Thus, rotating units require only, perhaps, a tenth of panel’s volume.  This is a significant consideration in ship cost and design.
 
Weight.  I do not have data on unit weights but I assume that panels, with 3-4 duplicates and large elements, have significantly higher total weight than rotating units.
 
Damage Resiliency.  Older, lattice type rotating radars have a degree of inherent damage resiliency in that their lattice structure is mostly space.  Shrapnel sprayed in their direction will largely pass through with little resulting damage.  The denser the lattice or, in the case of rotating panels, the greater the degree of damage susceptibility.  Rotating panels, while solid as opposed to a lattice, are smaller than a rotating lattice and significantly smaller than flat panels.  Thus, their size confers a degree of damage resilience.
 
Fixed panels, on the other hand, are absolutely certain to sustain damage from shrapnel.  One hundred percent of shrapnel from nearby explosions will impact the panel with every piece producing damage.  Manufacturer’s claim that panels are resistant to damage because the undamaged elements can continue to function, albeit at a lower overall efficiency and effectiveness.  However, this claim is unproven by any realistic testing.  For example, while a single damaged element may not significantly impact the overall radar performance, what is ignored is the cabling, communications, cooling, and power ‘behind’ the elements and those are extremely vulnerable to damage and would, when damaged, likely affect large portions, or all, of the panel.  The manufacturer’s claims do not consider this type of damage, at all.
 
When damage does occur, if you lose a panel, you lose that coverage sector (90-120 degrees) permanently.  There is no alternative mechanism to compensate.  You have a permanent hole in your coverage.  Not good in combat!  In contrast, a rotating radar provides full coverage until it is completely incapacitated.  In addition, the typical radar arrangement of -48 and -49 allows either radar to take over the other’s coverage in the event of damage.
 
Coverage.  Rotating radars, by their nature, provide only intermittent coverage as the active (transmitting and receiving) portion of the radar is always moving.  In many cases, such as tracking at long ranges, this is an insignificant issue since the target is not changing location fast enough to matter.  At closer ranges and higher target speeds, such as supersonic missiles inside the horizon, this can be a significant problem.
 
The problem of intermittent coverage can be mitigated by using higher rotational speed or using double sided radars which have active portions front and back thus providing near 360 degree coverage.
 
Alignment.  While I can’t speak to every panel radar that exists, the Aegis SPY variants apparently require a very precise alignment as evidenced by the impaired performance and required repairs of radars of ships that have grounded or been in a collision.  Whether this alignment sensitivity is true of modern panels, I have no idea.
 
Protection.  Flat panels are likely easier to protect with armor.  A simple armored cover can slide over the panel, as needed.  Rotating radars would require either a rotating, box-like arrangement or a retractable mechanism – doable, of course, but a bit more complicated.
 
Performance.  How effective is each radar type?  Panels and hybrids both use the same general technology so, ignoring size, there is no difference.  Of course, size does affect performance under certain circumstances (long range detection of small or stealthy targets, for example) and, in those cases, large panels would be preferred.
 
Detection range (against some theoretical target), alone, is not the measure of performance.  Performance is dependent on the circumstances of use.  If one is attempting to detect very long range, small targets, one would want the largest, most powerful panel possible.  Alternatively, if one is attempting to conduct a horizon range anti-air engagement, large panels are a waste and a small, rotating or hybrid radar would be preferred.
 
However, performance cannot be divorced from other aspects such as survivability, maintainability, repairability, size, weight, etc.  Performance must be appropriately weighted in balance with the other factors.
 
Bear in mind that manufacturers focus on extreme detection range against ideal targets as the measure of performance.  In reality, that is an unlikely use case in combat (EMCON being the default state!) where horizon range engagements are the far more likely scenario.  Being able to detect a stealth mosquito a continent away is of no use when engaging missiles from the horizon in.
 
The interesting aspect of performance is the question, to what degree can a conventional lattice radar be improved?  There seems to be no end to the degree of improvement that panels can undergo but what about lattice radars?  Can they be improved?  How much?
 
A closely related question is, to what degree do lattice radars need to be improved.  Given that we’ve stated that horizon range engagements are the most likely use case, and knowing that lattice radars have theoretical detection ranges of hundreds of miles (against suitable, theoretical targets), how much better do they need to be?  Perhaps they’re more than sufficient, right now?  If a lattice radar can provide, say, 90% of the required performance at a miniscule fraction of the cost, is that not good enough?  I can’t answer that.  I merely pose the questions but they are important questions.
 
 
Conclusion
 
It is clear that each type of radar configuration has advantages and disadvantages and that modern flat panels are not the unquestioned superior choice that most assume.  The choice of radar configuration depends on the balance between all the factors.  It would seem that hybrid rotating panels represent the best balance, overall.  They have good performance, less weight, consume little internal volume, provide adequate coverage, and have a reasonable cost.  Of course, much depends on the use case.  For example, a dedicated AAW ship might well justify multiple, large panels.
 
For general purpose surface ships, a hybrid rotating panel is the best choice.
 
 
 
__________________________

 
[1]https://www.radartutorial.eu/19.kartei/07.naval/karte008.en.html
 
[2]https://www.radartutorial.eu/19.kartei/07.naval/karte027.en.html

Old is New?

 
Just a bit of nonsense.  I was struck by a photo of a concept model of a MEKO A210 frigate. 
 

MEKO A210

Does anyone else think it’s reminiscent of the old Clemson class, 4-stacker destroyer?
 

Clemson Class Destroyer

Maybe it's just me?