The U.S. Navy Quietly Tested Mach 3 Heavy Gun Shells That Could Revolutionize Surface Warfare

The U.S. Navy, without fanfare or notice, tested a new weapon last summer that could revolutionize surface warfare. The hyper velocity projectile (HVP) is a Mach 3 shell fired from existing guns on cruisers and destroyers. A guided projectile, HVP can drop high explosives on enemies on the ground up to three times as far as conventional ship gun ammo with a high rate of precision. It can also intercept incoming anti-ship missiles, providing an economical alternative to increasingly expensive anti-missile interceptors.

According to USNI News, the guided missile destroyer USS Dewey fired 20 new HVP projectiles during the 2018 Rim of the Pacific (RIMPAC) exercises. Although the test was unclassified, it was not reported at the time by the U.S. Navy. It was the first known use of HVPs at sea by a warship.

Large surface combatants in the U.S. Navy all carry the Mk.45 5-inch (127mm) Naval Gun System. Unlike railguns, these are chemical energy guns that use gunpowder to launch projectiles, a basic technology hundreds of years old. Guided missile cruisers of the Ticonderoga-class carry two Mk.45 guns, while guided missile destroyers of the Arleigh Burke-class carry one. These guns are typically used for shore bombardment, softening up enemy defenses before an amphibious assault, although in a pinch they could be unleashed against enemy surface ships and incoming aerial threats.

I wonder if this system is scalable. For example, if a 5 inch HVP can fly at Mach 3 with a range of 40 miles what would say an 8 inch version or higher be able to do. What is the capabilities of a 16 inch battleship firing 16 inch versions of these rounds.

This might scale but not in the way you might think. Shell weight goes up with the CUBE of diameter.

A 5"/54 shell weighs 70 pounds
An 8"/50 shell weighs 335 pounds.
A 16"/50 shell weighs 2,200 pounds
Propulsive force required increases similarly.

There are a LOT of factors that go into getting a hit with a naval gun. Other than the obvious, there is the matter of the consistency of shell weight and propulsive energy.

The key item here, other than the increased range, is the guidance system built into the shell. A 5" gun can put out 16-20 rounds a minute. A 16" only 2 rounds. Then there is the accuracy to take into account. Currently, we get 80-90% hit rates with a 5" while 16" is only about 1-2%. Assuming you could get the accuracy of a 16" up to 30% you could get the accuracy of a 5" up to around 98-99%.

You don't need to sink the enemy to win. Given the construction of modern ships, I would much rather hit the target 5-6 times very fast and get a mission kill than maybe not hit them at all.

There is also the issue of the construction of the ship necessary to mount the larger gun calibers. Back in the early 80s we mounted the light weight 8" gun on the USS Hull as a test platform. It had previously had a 5" with no issues. The 8" shook the ship apart and drastically shortened the ship's service life to the point it had to be decommissioned. We can, and do slap a 5" on all kinds of ships with no issues.

Now consider scaling DOWN the shell size. The 76mm has a shell weight half that of the 5" (126mm) but a rate of fire that is four times greater. With the same hit rate, you can get twice the weight of shell on target at roughly the same range as the current 5".

Hope this helps. If you still have questions, just ask.

WWG1WGA

Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)

On my phone so this is short and not very quote-y.

The thing is, is that the larger guns aren’t really used for naval combat. Maybe in WWII when you had groups of ships, and your 1% hit rate was multiplied by 20 targets. Yes, modern round guidance systems are more accurate, but 8”+ guns are going to be used for shore bombardment, where there’s a greater area of effect and a miss isn’t as much of a miss.

On the other hand, scaling down you start losing out on impact and how much damage you can do. Equal momentum does not equal the same punch across different bores.

I think we are in general agreement here.

The original article highlighted the weapon as a lower cost method of killing cruise missiles and drones over the Sea Sparrow and SM2 missile systems. For this purpose you would WANT the Mk45 5" or the 76mm OTO Melara.

Larger calibers are preferable for shore bombardment but for that purpose you don't need the HVP guided projectiles. Standard ammunition works just fine. Naval Gun Fire Support (NGFS) is a MUCH simpler fire control solution vs that of hitting a surface vessel, drone, aircraft, or missile.

The point remains that our current ship hulls are not designed for and would not be able to handle a scaled up version of the Mk45 5" gun. This means that new classes of ships would have to be designed and built.

Yes, we could bring back 2 or 3 of the Iowa BBs but it might be cheaper to design and build new ships. Bringing back the BBs would be faster but if they are needed that badly then we have much bigger problems. Notably, the failure of our Intelligence Services to identify the looming threat that the BBs would be the counter to.

WWG1WGA

Depending on your height of eye, 10NM can be over the horizon. As a general rule, our surface search radar was good out to 20NM. Air search much farther. There are considerations other than height when determining the effective range of a radar.

A drone operating a radar would alert the enemy to your presence and would be killed in short order. They would also begin maneuvering so as to throw off your fire control solution. I know I would be maneuvering like crazy.

The targeting drone or aircraft would be the immediate subject of ECM (Electronic Counter Measures), degrading or disrupting its targeting capability.

This was my specialty. I have a patent in Electronic Warfare. Uncle Sam owns it but my name is on it.

WWG1WGA

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.