USCGC Kathleen Moore (WPC-1109)

What is the Problem?:

For a good while, I have been pointing out that the Coast Guard really does not have a means of forcibly stopping a medium to large ship, if its crew is willing to risk death. Even the largest guns the Coast Guard has (76 and 57mm) are unlikely to be able to reliably stop such a ship, and those larger cutters that carry the 76 and 57mm guns are unlikely to be available when needed anyway. They are more likely to be either deployed far from the ports or in maintenance status, unable to respond in a timely manner. There are also no other US military forces positioned and ready to respond to this type threat.

This means, the assets most likely to be available to stop a terrorist attack are Webber class WPCs and smaller vessels. They are armed, at best, with the 25mm M240 chain gun in a Mk38 mount and .50 caliber machine guns. These are even more unlikely to be able to forcibly stop a vessel. In addition there is a good possibility, a hostile vessel used for such a mission could be equipped with weapons that can out gun and out range the cutter. The Mk38 has a reported effective range of 2700 yards. I estimate the maximum effective range of improvised weapons on a terrorist vessel might be as much as 4000 yards. (I have never seen any indication anyone is attempting to train to use anything approaching the 25mm’s maximum range of 7,450 yards.)

Photo: This is a Chinese experiment with improvised armament for civilian ships. Likely useful systems include anti-tank guided missiles, recoilless rifles, heavy machine guns, man portable anti-aircraft missiles, and anti-aircraft and anti-tank guns which are designed to follow fast moving targets allowing them to compensate for movement of the ship. Terrorists would probably make more of an effort to hide the weapons, but you get the idea. 

What is available?:

I believe light weight torpedoes are the lightest, cheapest way to provide the missing capability.

Until recently, I had assumed, we would have to at least reprogram some of our existing light weight torpedoes. Recently I saw a report that the Mk46 mod5 has an anti-surface capability, so it may not be necessary to create or modify a torpedo for the role.

The Mk46 torpedo is not exactly new tech, the original design is over 50 years old and the mod5 version was introduced over 30 years ago. Two newer light weight torpedoes have been developed since introduction of the Mk46, the Mk50 in 1981 and the Mk54 (which uses the propulsion system of the Mk46) in 2004. Because the replacements are more expensive, there are still a large number of Mk46 torpedoes in the inventory. The national fleet (Navy and Coast Guard) has far fewer light weight torpedo armed surface combatants now (85) they did, 30 years ago (229). (At one time, the Coast Guard had quite a few Mk46 torpedoes on the 378s.)

Despite its age, the Mk46 appears adequate to stop most ships. It has an unclassified reported speed 45 knots and a range variously reported as at least 8,000 yards. Its warhead wight is only 98 pounds, about 15% that of the Mk48 heavy weight torpedo’s 650 pound warhead, but the effects of underwater explosions are not proportional to the weight of explosive. The effect, assuming the same explosive is use, is proportional to the cube root of the weight of explosive. This means that the shock experienced as a result of a 98 pounds of explosive underwater is more than half that experienced as a result of the explosion of 650 pounds at the same distance.

We might convince the Navy that putting torpedoes on Coast Guard cutters, is just another place to store them until needed. We are not likely to expend many of them, and if we use one or two, I think they will forgive us.

Why the Webber class WPCs?:

If there is a terrorist attempt using a medium to large ship, a Webber class WPC is likely to be the most capable Coast Guard unit available to attempt to stop the attempt. Larger ships are likely to be either far away or unable to get underway in time.

Perhaps in the future we could also equip the larger cutters and the 87 foot WPB replacement with these weapons, but the WPCs should be the highest priority.

What does an installation look like?: 

American light weight torpedo launchers are all designated Mk32, but they are available in three configurations, triple, stacked twin, and single. The single tube fixed Mod11 is the lightest and probably most appropriate for the WPCs. Two torpedo tubes and two torpedoes are probably sufficient. Support equipment can mostly be left at a support facility ashore.

Surface Vessel Torpedo Tube, Mk32 mod11

These systems are relatively small, 11’4″ in length and less than two feet wide. Loaded with a Mk46 torpedo, each tube weighs 1160 pounds. They do require 9’6″ of open space behind the breech for the tray used to load the 8’6″ long torpedo.

Where to put install?:

In regard to putting torpedoes on Webber Class cutters, one question I have gotten is, “where would you put them?”

I see three likely locations. All three would require some minor modifications to the ship.

1. On the stern aimed aft to fire over the transom.
2. On the O-1 deck behind the bridge firing forward and slightly to the sides.
3. On the O-1 deck forward of the bridge firing forward and slightly to the sides.

The first would require some rearrangement of deck outfit.

The second and third options would likely require about a three foot wide and 12 foot long extension to the O-1 deck on both sides essentially covering the walkway between the main deck superstructure and the side of the hull. This would allow mounting and access to the tubes which would be pointed at a shallow angle outboard placing the muzzle just inside and above the ship’s side. The breech would be angled in so that it is accessible for loading from the clear space behind it.

Personally I prefer the second or third options.

If there is ever a question “Are cutters are large enough to launch a light weight torpedo?” this should dispel any doubts. Below is a photo of a 12 meter (40 foot) Unmanned Surface Vessel with two torpedo tubes. It also has a dipping sonar (presumably the type used by helicopters).