GLSDB, Perhaps a Low Cost, Containerized, Precision, Shore Bombardment and Anti-Ship Weapon / Maybe Taiwan Could Use It Too

The Drive reports on the possible provision of a weapon system to Ukraine, the Ground Launched Small Diameter Bomb (GLSDB). (I am suggesting that we could launch it from ships, so Surface Launched might have been more appropriate).

This weapon might have a place as a replacement for the big guns that once provided Naval Gun Fire Support. It also has potential as an anti-ship weapon.

The system consists of a hybrid of a normally air launched, precision guided, winged bomb, the “small diameter bomb,” flung into the air by a rocket booster used in an early Multiple Launch Rocket System (MLRS) munition, the M26.

The M26 was the first rocket developed for the Multiple Launch Rocket System (MLRS). It is spin-stabilized by 4 fins, has a range of 32 km (20 miles) and is armed with 644 bomblets, anti-personnel/anti-materiel grenades. These bomblets have fallen out of favor because the dud rate creates potential for collateral damage that may occur long after the conflict that prompted their use. To create the Ground Launched Small Diameter Bomb, the grenades are replaced by a Small Diameter Bomb.

A guest inspects a new Boeing small-diameter bomb (SDB) in it’s flight configuration at the roll-out ceremony Monday, May 22, 2006, in St. Charles, Mo. (Tom Gannam/AP)

Small Diameter Bombs:

There are four different “Small Diameter Bombs”:

“The bomb can use GPS/INS to guide itself into the general vicinity of a moving target during the initial search phase, with course correction updates provided using a Link 16 over UHF data link…The weapon is capable of fusing the information from the sensors to classify the target and can prioritize certain types of targets as desired when used in semi-autonomous mode.”

How does it compare to Naval Guns?:

These are small bombs, developed to increase the number of precision munitions an aircraft can carry in a single sortie. Four of these replace a single 2,000 pound bomb.

SDBs are small bombs but compared to most naval guns, they pack a pretty big punch. Because of their precision, the relatively small bomb is still adequate to destroy many targets including tanks, aircraft shelters, bunkers, and strong points.

 “Warhead penetration is 3 ft (1 m) of steel reinforced concrete under 3 ft of earth and the fuze has… selectable functions, including air burst and delayed options.”

The GBU-39’s 36 pound bursting charge is 50% larger than that of the last 8″ projectiles used by the US Navy and more than four and half times that of current 5″ projectiles. (The bursting charge in the 16″ High Cap projectiles fired by Iowa class battleships was only 153.6 lbs. (69.67 kg)).

Perhaps most importantly, this weapon out-ranges all existing naval guns with a range of 150 km / 81 nautical miles.

Why it will be difficult and expensive to shoot down:

Now anything can be shot down, from artillery and mortar rounds to ICBMs. Because these are glide bombs it might be assumed they would be easy to shoot down, but that is not necessarily the case. Their small size means they have a small radar cross section. Because they are a glide bomb, unlike aircraft or cruise missiles, they have little or no IR signature. That means they are not good targets for IR homing missile such as man portable air defense systems (MAPADS). Because the round is maneuverable, there may be opportunities to avoid heavy concentrations of AA.

It is probably going to require high quality AAW missiles to bring one of these down, meaning the cost exchange is likely to be favorable for the SDB. Being cheap they can be traded off against the more expensive missiles required to bring them down, depleting the enemies air defenses. That could result in making it safer for our manned aircraft.

Why not let Naval Air just drop the Small Diameter Bombs:

That is certainly an option, but if surface launched Small Diameter Bombs are available it can free aircraft for more demanding missions like air superiority and suppression of air defenses. Surface launched SDBs and aircraft could be complementary,

There is also the possibility that the carrier(s) may be called away or their flight deck might be damaged precluding air ops.

Where could we mount them?:

The video shows a six-tube launcher inside what is almost certainly a 20x8x8 foot container. That suggests that there are many options available including multiple launcher installations on Offshore Support Vessels, either manned or unmanned as well as many existing vessels.

As defensive weapons, the widespread use of 20x8x8 containers means that it is going to be very hard to single out those that mount these weapons. A “shell game” can make them very difficult to recognize and neutralize.

The Cost Exchange Ratio:

What makes these a game changer? It is the precision and range combined with its low price. The War in Ukraine has shown the rapid expenditure of munitions. There is a need for weapons with longer range and greater survivability, but they will cost much more. We cannot afford to expend weapons that cost millions on every target. There are times when it is necessary to expend an expensive weapon on a far less expensive target, but that can’t become the norm. We need weapons that can be produced in huge numbers at a reasonable cost.

Now About Taiwan:

If the Chinese are to invade Taiwan, it will be comparable in scope to the Normandy Invasion. The Chinese Navy can transport only a small percentage of the troops that would need to land on the first day of the invasion. They will need to mobilize a very large number of civilian craft including ferries and fishing boats to transport the number of troops that will be required.

If the Taiwanese are to stop the invasion, they are going to have to sink a very large number of craft as they transit the Taiwan Strait. (The Strait is 130km wide at its narrowest point.) Most of these craft will be relatively small and have little or no self-defense capability.

Using the GBU-53B, with its tri-mode seeker, the Ground Launched Small Diameter Bomb appears ideal for this purpose. Given the bombs, the Taiwanese could probably quickly devise an even longer-range booster and launcher.

Fast Response Cutter / Navy MkVI Patrol Boat –Peter Ong

Today we have a guest author, Peter Ong. This is Peter’s sixth post on this blog, and he is now a regular contributor to Naval News. In this post, he reports a conversation with Coast Guard Cutter Forces about why the success of the Coast Guard’s Fast Response Cutter program has allowed  the Navy to cancel their MkVI patrol boat program that at one time was expected to produce 48 patrol boats.

The MkVI had only very austere galley and messing facilities, a Microwave and MREs. They were not expected to be underway more than 24 hours. The FRCs endurance, allowing days, rather than hours, on station to intercept drug and arms smugglers and their abilitiy to support counter UAS systems may be providing capabilities the MkVI simply could not have.

220822-A-KS490-1182 STRAIT OF HORMUZ (Aug. 22, 2022) From the left, U.S. Coast Guard fast response cutters USCGC Glen Harris (WPC 1144), USCGC John Scheuerman (WPC 1146), USCGC Emlen Tunnell (WPC 1145) and USCGC Clarence Sutphin Jr. (WPC 1147) transit the Strait of Hormuz, Aug. 22. The cutters are forward-deployed to U.S. 5th Fleet to help ensure maritime security and stability across the Middle East. (U.S. Army photo by Spc. Noah Martin)

When is a ship a boat and when is a boat a ship? When is an apple an orange and when is an orange an apple? Answer: they are not as these are two different and distinct things when it comes to comparing the warships of the U.S. Coast Guard to the MkVI patrol boats of the U.S. Navy.

A U.S. Navy Mark VI patrol boat with Maritime Expeditionary Security Squadron TWO moves through the water prior to a live fire exercise in the Philippine Sea, Feb. 27, 2021. (U.S. Marine Corps photo by 1st Lt. Stephanie Murphy).

The U.S. Navy is divesting of their 12 in-service Mark VI Patrol Boats, which at the Surface Navy Association 2021, Major General Tracy King, USMC, Director, Expeditionary Warfare (N95) stated that the twelve Mark VIs “Were very expensive to maintain.” However, many critics and pundits of the Mark VIs’ early retirement cite that the Mark VIs still have a lot of life left in them and that their high speeds and heavy armament makes them an asset to special forces, Marines, and Navy SEALs. Mark VIs also perform capital ship escort screenings and contribute to Distributed Lethality and Distributed Maritime Operations by having a smaller vessel signature that might help U.S. Marines move around and slip ashore undetected.

In a phone interview on September 29, 2022 with United States Coast Guard (USCG) Captain John J. Driscoll, Office of Cutter Forces (CG-751), the U.S. Coast Guard captain made a comment about the Sentinel-class Fast Response Cutters (FRC) substituting for the U.S. Navy’s Mark VI Patrol Boats in the Patrol Forces Southwest Asia (PATFORSWA) region and other parts of the globe.

The U.S. Navy plans to replace the Mark VIs and the aging Patrol Coastal boats in the PATFORSWA region with USCG FRCs. When asked how the cutter fleet is integrated with the U.S. Navy and the Department of Defense, the captain replied that the cutter fleet is built into different operational security plans within the U.S. Department of Defense, but these plans are not discussable.

Captain Driscoll said that the Coast Guard’s Fast Response Cutters and the Mark VI are different assets and have different capabilities. The 65 planned FRCs have much greater range and greater endurance (5 days, 2,500 nautical miles (4,600 km; 2,900 mi) and are designed to be on patrol 2,500 hours per year) than the U.S. Navy’s Mark VI Patrol Boats (750 nautical miles (860 mi; 1,390 km) at 25 knots; 690 nautical miles (790 mi; 1,280 km) at 30 knots).

The captain mentioned that the FRC is tremendously capable and different in how it integrates with the Department of Defense and one can’t make comparisons between the Navy’s Mark VI and the USCG’s Fast Response Cutters because the FRC is a commissioned warship of the United States with an assigned crew whereas the Mark VI is just a patrol boat—a ship versus a boat—the ship is larger. The FRC is 154-feet long (46.9 m) with a beam of 25-feet (7.6 m) whereas the Mark VI Patrol Boat is 84.8-feet (25.8 m) long with a beam of 20.5-feet (6.2 m).

Armament is about the same between the two vessels (a Mark 38 MOD 2 25mm autocannon forward with crew-served 12.7mm heavy machine guns and grenade launcher(s) aft) with the Mark VI sporting more armament (another potential Mark 38 25mm autocannon aft and potential crew-served 40mm automatic grenade launchers or 12.7mm heavy machine guns. Some PATFORSWA FRCs will receive the Mark 38 MOD 3 with a 7.62mm coaxial chaingun to the bow 25mm autocannon and a 40mm automatic grenade launcher).

Nonetheless, one can see the huge difference in operational range. Furthermore, the success of the 65 planned Coast Guard FRCs eclipses the 12 Mark VI U.S. Navy Patrol Boats in terms of production numbers. Furthermore, the Mark VI is propelled by waterjets to 45 knots (52 mph; 83 km/h) whereas the FRC has propellers that drive it at 28+ knots. Repeated requests to the U.S. Navy asking for explanation on “[The Mark VIs are] very expensive to maintain” were not answered, but one can assume that it takes a lot of time, labor, and money to clean out the Mark VI’s waterjet intakes and impellers compared to the more easily accessible external shaft and propellers on the Fast Response Cutters when operating in littoral waters potentially teeming with flotsam and seaweed.

FRC range and endurance are important. Captain Driscoll stated that the FRCs are working in the Papua New Guinea and Indonesian region to combat Illegal, Unreported and Unregulated (IUU) fishing and are working with partner nations to address the competition for maritime resources.

As for possible up-arming of the FRCs with the Mark 38 MOD 4 30mm autocannon, that is a retrofit possibility, noted the captain, although the upcoming Polar Security Cutter (PSC) heavy icebreakers will receive the 30mm autocannons first, two on each PSC. Captain Driscoll mentioned that the 30mm autocannon is in the U.S. Navy acquisition system and that the USCG and U.S. Navy both decide on future cutter armament. Programmable and airbursting 30mm ammunition options are not discussable although if the U.S. Navy has the specialized and advanced 30mm ammunition in its inventory, the USCG can also use it depending on the cutter’s mission parameters.

The new Mark 38 Mod 4 30mm naval gun system on display on MSI Defence stand at Sea Air Space 2022. It can, in theory and with funding, be retrofitted aboard existing USCG cutters if agreed upon between the U.S. Navy and the U.S. Coast Guard. Photo: NavalNews

Maybe Another Reason to Look at APKWS

The VAMPIRE system can fit in almost any pickup or vehicle with a cargo bed. (Courtesy of L3Harris)

The Navy League’s on-line magazine, Seapower, reports,

BAE Systems completed additional ground-to-air test firings to prove the effectiveness of 70mm rockets guided by APKWS guidance kits against Class-2 unmanned aerial systems (UAS) that weigh roughly 25-50 pounds and can travel at speeds exceeding 100 miles per hour, the company said in a Nov. 29 release…During the demonstration in Southern Arizona, five APKWS-guided counter-UAS rockets were fired from a containerized weapon system and destroyed all targets, including fast-moving drones.

APKWS  info.

Another Gun/Missile Remote Weapon Station Suitable for Patrol Boats

Navy Recognition reports,

At Euronaval 2022, a naval defense exhibition that was held in Paris, French Company Nexter unveils the latest generation of its NARWHAL 20mm remote-controlled turret which is now armed with one 20mm automatic cannon and the MBDA’s AKERON guided missile launch pod.

I am not a fan of this particular system. I would like to see at least a 30mm gun, but it is more evidence of the practicality and desirability of combining small missiles with a gun mounted on a remote weapon station.

Would really like to see the Coast Guard push for an upgrade of their Mk38 gun mounts to incorportate either APKWS or Hellfire / JAGM.

“Laser-Guided Rockets Are Getting New Highly-Versatile Anti-Armor Warhead” –The Drive

The Drive reports on a test of a new warhead for the “Advanced Precision Kill Weapon System” (APKWS)

The Advanced Precision Kill Weapon System, or APKWS, laser guidance kit designed by BAE Systems has been tested in a surface-to-surface role with a new highly versatile, multi-purpose warhead that is capable of taking on armor and other targets. The new warhead is provided by General Dynamics Ordnance and Tactical Systems. The test demonstrated added flexibility for not only the APKWS itself, which is most often employed in air-to-ground applications against more lightly armored targets, but also for all platforms that are capable of firing APKWS rockets.

A screenshot from the General Dynamics video showing the launcher configuration used during the test. Credit: General Dynamics

The test also demonstrated a new launcher.

The report was quite complete, providing background and an update on the entire program.

If you have been reading this blog regularly, you know I think APKWS would be a good fit for the Coast Guard as a precision weapon that would be highly effective against small, fast, highly manueverable threats while minimizing the possibility of collateral damage. Its relatively new proximity fuse also makes it effective against Unmanned Air Vehicles which appear to be an emerging threat. APKWS might even be effective against small ships if used in quantity.

For larger threats Hellfire or its replacement, JAGM, would be a better choice, but because this is so much cheaper and available in larger quatities, it appears much more likely. APKWS would probably be a better choice for PATFORSWA where the threat includes large numbers of small craft and UAVs.

We may have seen the video below, but it does suggest that the system is suitable for the 85 foot Navy MkVI patrol boat, so its certainly suitable for cutters of similar size and larger.

“Loitering Munition Strikes Ukrainian Gunboat, A First In Naval Warfare” –Naval News

Naval News reports a Ukrainian Gyruza-M-class patrol boat

Gyurza-M-class gunboat. Photo: Ministry of Defense of Ukraine

has been hit by a Russian Lancet Loitering Munition.

ZALA Lancet, side view, Photo by Nickel nitride

The Ukrainian gunboat seems to have been pretty well armed.

We have talked about Loitering Munitions before:

These could be the answer to the Coast Guard’s need to be able to defeat small, highly manueverable, high speed surface threats.

They also extend the range at which non-state actors might be able to engage Coast Guard units.


Joint-Forces reports,

General Robotics of Israel, an advanced systems developer, has unveiled the SHARK Naval RCWS smart weapon station for light boats.

Not only is it light (85 kg without weapon and ammunition), but it also has a unique fire control system,

When the operator presses the trigger, the AI-driven fire control runs a target prediction algorithm to align the projectile’s path and the target’s expected location and points the weapon in that direction. Only then is a burst fired. This technique has demonstrated hit accuracy of about 70 percent. This unique capability enables SHARK to be used as a naval Counter-UAS weapon.

Looks like something the Coast Guard might be interested in.

A pair of these mounted on opposite corners of the PATFORSWA Webber class, replacing two of the crew served .50 cal., might come in handy.

Boom Defense, Everything Old is New Again

A little footnote on the War in Ukraine. This is from Covert Shores “Attack On Kerch Bridge: Initial Geolocation Of Damage.” A section at the bottom of the post is a look at increased Russian activity after the attack on the bridge.

Take a look at the detail picture of the harbor, above, top, near the center, second from the right. The thin wavy line is a boom or net accross the entrence to Sevastopol harbor.

Steel floats for anti-submarine nets, 1953

Anti-submarine nets were common during WWII, and booms go back to at least the American Revolution if not to antiquity. This may be in response to Ukraine’s apparent use of unmanned surface vessels. I have seen some barriers deployed around aircraft carriers moored at North Island in San Diego.

What does this have to do with the Coast Guard? Buoy tenders were commonly used as Net Tenders during WWII, opening and closing the anti-submarine nets.

Armed unmanned surface and subsurface vehicles are providing a new reason to deploy nets and barriers. We may see a return of these systems.

“Hellfire Missile With Roughly Three Times More Range Tested…” –The Drive

New Lockheed Hellfire/JASM launcher discussed earlier

The Drive reports an exercise that claimed to employ an enhanced version of Hellfire with a range about three times as great as that of the previous versions. Hellfire’s replacement, JASM, perhaps more accurately an upgraded Hellfire, has now been approved for full rate production and there have been reports that a longer range version was in the works.

Beyond the air-launched advantages, this missile would be hugely beneficial for sea-launched applications, such as the LCS. Beyond that, it could be extremely beneficial in servicing Hellfire’s growing surface-to-air role, as well.

Since the typically reported surface to surface range of the Hellfire is 8 km, three times that would be 24 km or over 26,000 yards (equal to the longest ranged battleship hit in WWII). In most cases, that means it can reach anything within the visual horizon. It would also mean, it would out range our 57 and 76mm guns. If this longer ranged Hellfire/JASM is mounted on the new 30 mm Mk38 Mod4, it could mean even Polar Security Cutters will have a potentially more potent weapon than the 57mm Mk110, with a much smaller footprint and lower maintenance requirements.

The weapon would certainly be a welcomed addition to the Webber class patrol craft of PATFORSWA because it would give them greatly enhanced capability against swarming small inshore attack craft, helicopters, and UAS, threats common in their operating area.

As I noted earlier, JASM could provide Coast Guard vessels as small as patrol boats, with a much more accurate, more powerful, and longer ranged response to the need to be able to forcibly stop vessels both small and large, while also providing counter UAS, a degree of anti-aircraft protection, and should it ever be required, a naval fire support ashore capability.


U.S. Marines with Marine Aerial Refueler Transport Squadron (VMGR) 252 equip a KC-130J Hercules with AGM-114 Hellfire missiles (U.S. Marine Corps photo by Lance Cpl. Christian Cortez)

Sandbox has a good overview of the Hellfire missile’s replacement, the AGM-179 JAGM (Joint Air Ground Missile–Despite the acronym, this missile will be used surface to surface and even surface to air, as well as air to surface.)

I have for a long time pointed to the Hellfire as a missile that could provide much needed firepower if any of our vessels, down to and including patrol boats, encounter a situation where they need to forcibly stop a vessel, regardless of size, with a near 100% prospect of success against small, fast highly maneuverable targets and at least some chance of success against large ships. All with minimal chance of collateral damage.

The post notes that the AGM-114L Longbow Hellfire, the version used in vertical launchers as part of the anti-surface module on Littoral Combat Ships has been out of production since 2005, but the new missile will include the capabilities of the Longbow Hellfire as well as Semi-Active Laser Homing.

The Missile:

JAGM shares many components with the Hellfire. It has the same dimensions:

  • Length: 70″ (1,800mm)
  • Diameter: 7″ (180mm)
  • Weight: 180 pounds (49 kg)
  • Warhead: 20 pounds
  • Range: 8 km (almost 9,000 yards)


There are a number of ways the missile could be integrated into the various cutter classes.

There are stand alone single round launchers.

Launch tubes could be attached to existing Mk38 gun mounts.

We could use small vertical launch systems.

Textron Systems’ CUSV with Surface Warfare payload including a Hellfire vertical launch system, the box in the center, at SAS 2019

These weapons will be made in huge numbers, thousands per year, and in the meantime, there are thousands of Hellfires in inventory that could meet our needs. This is a weapon based on the Hellfire’s history of success and with a promising long term future. It has a small foot print, and requires minimal maintenance and training while providing the punch of a 6″ naval gun. Range is expected to be extended to 16 km.

This is doable, at modest cost, and the Navy should pay for most of it.