You Had One Job

In a little publicized event, Hezbollah forces downed an Israeli early warning aerostat.  The $230M aerostat radar system, called Sky Dew, was designed to provide stand off early warning of drones and aircraft with a claimed detection range of 250 km.  The aerostat was located around 21 miles from the Lebanon border and a Hezbollah drone penetrated Israeli airspace undetected and, in some fashion, suicided on the aerostat, downing it.[1]
 

Israeli Sky Dew Aerostat

Aerostats are a frequent suggestion from commenters on this blog who believe it can provide nearly unlimited detection of all enemy assets in the global hemisphere.  Okay, a touch of hyperbole there but not much.  Proponents ascribe nearly miraculous characteristics to these glorified blimps.
 
The incident illustrates a couple of noteworthy points:
 

• No technology works as advertised.  The aerostat had one job:  detect drones … and it failed completely.  The claimed detection range is 250 km.  Apparently, the actual detection range is about a foot.  The reality is that all technology is overhyped and will perform poorly in combat.  This emphasizes the necessity for realistic testing … which the Navy steadfastly refuses to do.
• Many people believe radar is a miracle of detection.  It is not.  It is useful, to be sure, but suffers spectacular detection failures on a regular basis.  It is not God’s all-seeing eye as so many believe.
• Aerostats are non-stealthy, non-maneuverable, and utterly defenseless.  They are a target waiting to be destroyed unless one provides a robust, layered, defensive support scheme.

 
By the way, just to illustrate that everyone publishes propaganda, here’s Israel’s statement about the impact of the aerostat downing. 

“Rear Admiral Daniel Hagari, Israel’s military spokesman, confirmed that a Hezbollah drone had scored a direct hit on Sky Dew but added there were no casualties and that it “had no impact to the IDF's aerial situational awareness capability in the area”.[1]

Okay … so if the loss of the aerostat ‘had no impact’ then why did you spend $230M on it since, according to you, admiral, its presence, or absence, has no impact?
 
Clearly, the Israeli admiral was just putting out pure propaganda.  Hey, Ukraine does it.  Russia does it.  The US does it.  China does it.  Everyone puts out propaganda.  One of the reasons this blog exists is to analyze these things and separate the propaganda from the facts.
 
Aerostat … you had one job and you failed miserably.
 
 
 
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[1]The National website, “Hezbollah 'blinds' Israeli defences with drone strike on Sky Dew airship”,Thomas Harding and Nada Homsi, 5/20/2024,
https://www.msn.com/en-ae/news/middleeast/hezbollah-blinds-israeli-defences-with-drone-strike-on-sky-dew-airship/ar-BB1mz3UT?ocid=BingNewsSerp

New Threat Upgrade and Aegis

From a certain perspective, the Aegis combat system was one of the worst developments in the history of the Navy.  It directly led to the [literal] sinking of an entire class of the best ASW destroyer ever built and has resulted in expensive ships with permanently degraded radar systems.  Worse, there was an alternative to Aegis which was the New Threat Upgrade (NTU) program which would have modernized the existing conventional radars and combat systems, providing much the same capabilities.  Let’s take a closer look at NTU and Aegis.
 
 
Background
 
It became apparent to the Navy that the existing aerial (meaning, mostly, missiles) threat of the time would only grow more lethal and that this would happen sooner rather than later.  Prior to this, incoming targets had been engaged one at a time in an almost leisurely manner.  Now, however, the Navy could foresee sea-skimming, saturations attacks and they recognized that a much more flexible, rapid defense was needed with the ability to engage multiple targets simultaneously or nearly so.  The situation was made worse by the fact that each defensive missile needed a dedicated illuminator radar for guidance and each ship had only two or three such illuminators.
 
The solution that the Navy envisioned was to develop a system that would allow multiple defensive missiles to be guided against multiple targets simultaneously.  Thus was born the concept that eventually led to Aegis. 
 
However, Aegis was not the only solution.  An alternative method using conventional radars was also devised, the New Threat Upgrade.
 
 
NTU
 
As the shortcomings of the initial Standard SM-1 missile and its guidance system became apparent, a series of upgrades were developed culminating in the SM-2 which would be paired with NTU along with two new radars, the SPS-49 and SPS-48 which would have replaced the common SPS-40 and SPS-55 sets then in use.  In fact, the SPS-48/49 combination is still in use on big deck amphibious ships such as the Wasp and America classes and the SPS-48 is standard on the San Antonio class.
 

SPS-48, -49 on Wasp Class

Other new NTU-related equipment included [2]:
 

• SPS-64 navigation radar
• SLQ-34 electronic warfare
• SRQ-4 data link for SH-60 helicopters
• SYS-2 Integrated Automatic Detection and Tracking (IADT) system
• SYR-1 telemetry receivers (missile in-flight position data)

 
All of these new pieces of equipment were to feed directly to the NTDS (Naval Tactical Data System) combat system, the combat management system equivalent to Aegis.
 
The main improvement offered by NTU was the ability to time-share the few SPG-51 illuminators so that multiple missiles could be controlled by a single illuminator.  In addition, the NTU ships Kidd and Scott demonstrated cooperative engagement capability (CEC) during tests in 1989 using Link 11.
 

SPG-51 Illuminator

As it happened, the NTU upgrades were applied to the 4-ship Kidd variant of the Spruance class, USS Mahon, and the Leahy class.  Elements of NTU were applied to USS Long Beach but it is unclear whether the entire, formal NTU upgrade was applied.  USS Texas, CGN-39, was retired in the midst of its NTU upgrade.  NTU would have made the Virginia class cruisers quite formidable. 
 
NTU, when it first came out, was generally considered superior to Aegis which would spend quite some time working out its bugs, as documented in ref[1].  See the side note at the end of this post for a more detailed description of Aegis’ early problems. 
 
In the event, the Cold War ended shortly after NTU came to fruition and the resulting budget restrictions led to fierce competition between NTU and Aegis for funding.  Recognizing the teething problems of Aegis and the fact that many believed NTU to be a viable (superior, at the time) and hugely cheaper alternative, the Navy decided to, literally, sink the entire Spruance class to eliminate the possibility of a Spruance-NTU fleet threatening Aegis funding.
 
 
NTU Alternate History
 
Where would NTU have gone in its subsequent development?  It is fascinating to contemplate the course of US naval history had NTU been the winner of the combat system ‘war’.
 
One can only imagine the altered path of ship development if the Virginia-NTU and Spruance-NTU had come to pass.  It is likely that the compromised Ticonderoga class (10 lbs of ship in a 5 lb can) would never have come about and the Burkes might have, initially, been designed as the pure AAW ships they always should have been.  This could have given us two focused ship classes: the ASW Spruances and the AAW Burkes instead of trying to make the Burkes a do-everything design.  One could imagine that, having specialized ASW and AAW destroyer classes, a true cruiser class, with an emphasis on offensive firepower, might have replaced the Virginia class instead of the badly compromised Ticonderogas.
 
As for NTU, itself, it is likely that, as radar development progressed, the conventional lattice radars would have given way to something akin to the TRS-3D/4D, rotating panels.  This would have been a hugely significant development in that it would have resulted in reduced size, reduced complexity, no alignment issues, reduced weight, reduced top-heaviness (stability) issues, and less utility demands in all subsequent ship designs.  Arguably, it would have produced more resilient radar setups by allowing multiple units, each providing 360 degree, and taking up far less external space and internal volume than Aegis flat panel arrays.  In short, the follow on ship classes would have been cheaper, simpler, and more combat resilient than what the Navy actually developed.
 
The one drawback would have been reduced maximum range, however, given the close range encounters that I believe most likely to occur in modern combat, much of Aegis’ performance claims are have been rendered moot.  Remember that Aegis was developed to counter high altitude, massed bomber and missile attacks.  For that, maximum radar range was required and, thus, the development of Aegis was understandable.  However, that requirement was fairly quickly abandoned in favor of low level attacks and NTU would have been equal or superior in that case.  Further, as it turns out, current advances in radar technology have seen small, rotating flat panel radars with claims of range equaling or exceeding the Aegis SPY claims.  Whether any of those claims are accurate is, of course, unknown.
 
In short, Aegis imposed all manner of severe penalties on the Navy and subsequent ship designs.  NTU might well have avoided most/all of those.
 
 
Aegis Cost
 
One of the main disadvantages of Aegis was that it was hideously expensive for the time (still is!).  The CIMSEC report makes note of the high cost of Aegis development and fielding. 

… [Aegis] critics noted the cost of fielding Aegis was consuming much of the Navy’s budget for engineering development. At the same time, ADM Zumwalt was committed to replacing the Navy’s World War II-era surface escorts which were still in service. To make this escort replacement program affordable, ADM Zumwalt planned to asked Congress to fund a “high-low” mix of ships, which featured low capability, less expensive escorts for convoy protection and high capability, higher speed escorts for work with carriers. The projected high cost of Aegis made ADM Zumwalt’s task of obtaining funds for large numbers of both “high” and “low” capability ships just that much more difficult.
 
At that stage ADM Zumwalt considered cancelling the whole project. He was angry because there was no AAW development plan to integrate the various ongoing AAW projects, and he correctly anticipated that Congress would resist funding sufficient numbers of an expensive, nuclear-powered Aegis ship.[1]

USS Long Beach was considered for an AEGIS conversion but the $800M (then year dollars) cost was prohibitive.[1]
 
NTU, in comparison, used modifications of existing radars and required no great redesign of ships in order to accommodate it and certainly did not require that a new class of ship be built just to ‘hold’ it.
 
 
History’s Judgment
 
Some might argue that even if Aegis was not all it was claimed to be, initially (what is?), it has now developed into the most advanced radar-combat system in the world.  However, this is simply not true.  As mentioned, Aegis is degraded fleet wide and this is, apparently, a permanent condition.  The degree of degradation is unknown as is the actual capability of the system since it has never been tested under realistic conditions.[3]
 
Recent events have also demonstrated that Aegis’ claims far exceed its actual capabilities as the entire USS Mason incident demonstrated (see, “Yemen Missile Attacks”).  The Navy has claimed to have shot down some drones and missiles recently, related to the Israeli-Hamas conflict, but, again, no details have emerged.
 
History also notes that conventional, rotating radars have become quite advanced with manufacturers claiming performance equal to or exceeding Aegis.  Of course, manufacturer claims are invariably greatly exaggerated.  Still, to those who would suggest that all the pain and cost of Aegis at least led us to a point we could not have otherwise reached, I would point out that current hybrid, rotating panel radars prove we could have reached this same point without going the Aegis route.
 
 
Conclusion
 
This post is emphatically not a debate about which system, NTU or Aegis, was or would become the better system.  As it turns out, Aegis has never lived up to its full hype.  The system is so complex that it is perpetually degraded, fleet wide, as stated by the Navy.  Whether that degraded state is superior to what would have been a modernized NTU system is, as I stated, unknown and not the point of the post.  The point of the post is that Aegis imposed heavy costs and penalties on the Navy by eliminating an entire class of the best ASW destroyer the world has ever seen just to ensure that Aegis had no funding competition.  In addition, Aegis permanently altered the course of Navy ship design and force structure for the worse.  That is the true cost of Aegis.
 
Aegis also ushered in the continuing era of unworkably complex technology which now infests our ships.  Far too many ship systems are beyond the ability of Navy technicians to maintain and repair.  In short, the systems are not combat-resilient.  On paper – or when they have been exquisitely tweaked by Ph.D. manufacturer tech reps – the capabilities are impressive but in real life they fall well short.  For example, in the early years of Aegis, the systems were supported by on-board crews of manufacturer’s tech reps but, as time went by, the tech reps left and Aegis fell into a degraded state as documented in a past Proceedings article by an Aegis ship captain.
 
Even if one were to stipulate that Aegis would have been theoretically superior to NTU, the question has to be asked whether it is better to have a theoretically superior Aegis that is perpetually degraded and impossible to repair at sea or a theoretically lesser NTU that routinely works at 100% efficiency and effectiveness?
 
It is also important to note that the strengths of Aegis were long range, high resolution sensing which was a desirable characteristic when facing large, high flying Soviet bombers but today’s threats are sea-skimming missiles in short range (horizon) engagements for which NTU would have been well suited.
 
All things considered, it appears that NTU may well have been the better path.  Of course, hindsight is 20/20!
 
 
 
_________________________________
 
As a related side note, Aegis performed poorly in its early years.  For those interested in the early trials and tribulations, here is an excerpt from a CIMSEC report.[1] 

In 1983, the newspaper headline war heated up again. CG-47 was put through qualifications trials that April. That summer, Representative Denny Smith (R-Oregon), a frequent critic of high-cost military procurement programs, alleged that CG-47’s Aegis combat system had failed operational evaluation. His criticisms were echoed in the Senate by Gary Hart of Colorado, a candidate for the Democratic Party’s nomination for President. As Senator Hart told The Wall Street Journal, “Do we have a testing and reporting system that is fundamentally dishonest?” To head off speculation, the CNO acknowledged that there had indeed been software system failures in the April trials and he pledged further tests in September.
 
After the September 1983 tests, both Watkins and Secretary Lehman wrote to Representative Smith, assuring him (as Lehman did on 11 October) that “Aegis is the most carefully tested combat system ever built.” But Smith did not stop his criticism of Aegis. That winter, he found an ally in Senator Charles Grassley (R-Iowa), a member of the Senate Armed Services Committee. In February 1984, Grassley grilled Secretary Lehman and CNO Watkins on CG-47’s performance. The Navy Secretary accused Grassley of “grandstanding” and said that CG-47 was performing splendidly off the Lebanese coast in her first tour overseas. One week later, unnamed Pentagon and Congressional sources told The Washington Post that the Under Secretary of Defense for Research and Engineering had informed the Secretary of Defense that Aegis had serious design problems, and the Secretary of the Navy admitted to reporters that “actual missile kills … have not been that impressive.” At the same time, Secretary Lehman officially (and privately) directed PMS-400 to supervise “a fully challenging test series,” which it did with CG-47, April 23-29, 1984, near Puerto Rico.
 
ADM Watkins praised the results of the trials at a public press conference, and the May 1985 Naval Institute Proceedings carried a glowing description of the Aegis system and also praised the performance of CG-47 during the ship’s tour of duty off of the Lebanese coast the previous fall. A later issue of the same journal, however, carried a long letter from an officer who claimed that the ability of CG-47’s radar to monitor contacts against the backdrop of the Lebanese coast had been exaggerated. The ship had been approached by a light plane while patrolling near Beirut’s harbor, and, by his account, CG-47 never detected it. The question of Aegis’ operational performance was therefore left somewhat unresolved.[1]

 
________________________________

 
[1]CIMSEC, “The Politics of Developing The AEGIS Combat System, PT. 2”, Thomas C. Hone, Douglas V. Smith, and Roger C. Easton, Jr., 2-May-2023,
https://cimsec.org/the-politics-of-developing-the-aegis-combat-system-pt-2/
 
[2]Capt. Michael C. Potter, USNR, Electronic Greyhounds, The Spruance-Class Destroyers, Naval Institute Press, 1995, ISBN 1-55750-682-5, p.172-4
 
[3]Note that there were tests in Aegis’ very early development (after serious real world problems were revealed) that claimed to be extensive and realistic but the conditions of the tests are unknown and the Navy has a well earned reputation for lying about such matters.  Further, the tests were against very early missiles now multiple generations removed from today’s threats.  The testing has not been repeated against today’s threats.

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