Military and Commercial Technology: Navy test-fires low-cost, hypersonic-speed projectiles

Friday, 11 January 2019

Navy test-fires low-cost, hypersonic-speed projectiles

BAE Systems

The Navy said it test-fired 20 high-velocity projectiles from the USS Dewey's standard Mk45 main deck gun during an exercise last summer.

By Ed Adamczyk

Jan. 9 (UPI) -- The U.S. Navy test-fired high-velocity projectiles using existing guns aboard a destroyer during an exercise last summer.

Twenty projectiles were successfully fired at near-hypersonic speed from the USS Dewey's standard Mk 45, five-inch main deck gun during the "Rim of the Pacific" exercises off Hawaii, the USNI News reported.

It was an attempt to learn if the 40-year-old gun's utility could include a high-tech, low-cost weapon against cruise missiles and unmanned aerial vehicles.

In October, the Congressional Research Service said in a report that the new weapon, called an HPV or hypervelocity projectile, was designed for a railgun, a device using electromagnetic force to launch projectiles by means of a sliding armature.

Shot from the deck gun, the payload can travel as fast as Mach 7.4, or over 2,400 mph at sea level. The system is under consideration, as is a laser guided system and the railgun approach.

"Any one of these three new weapons, if successfully developed and deployed, might be regarded as a 'game changer' for defending Navy surface ships," the CRS said. "If two or three of them are successfully developed and deployed, the result might be considered not just a game changer, but a revolution."

The "gun-launched guided projectile," as the Navy has renamed the system tested at the summer exercises, can be fired using existing and aging guns found on many vessels -- making it considerably less expensive than the other systems under examination.

Defensive missiles cost $800,000 to a few million dollars each, and would have to be used in great number to counter incoming salvos of enemy missiles. The gun-fired guided projectiles, however, cost about $85,000 each, the CRS said.

BAE Systems, developers of the HPV, said it can be used by existing Navy, Marine Corps and Army guns.

Source: www.upi.com

Hyper Velocity Projectile

BAE Systems

The HVP is a next-generation, common, low drag, guided projectile capable of executing multiple missions for a number of gun systems, such as the Navy 5-Inch; Navy, Marine Corps, and Army 155-mm systems; and future electromagnetic (EM) railguns. Types of missions performed will depend on the gun system and platform, but range from Naval Surface Fire, to Cruise and Ballistic Missile Defense, Anti-Surface Warfare and other future Naval mission areas.

The HVP’s low drag aerodynamic design enables high-velocity, maneuverability, and decreased time-to-target. These attributes, coupled with accurate guidance electronics, provide low-cost mission effectiveness against current threats and the ability to adapt to air and surface threats of the future.

The high-velocity compact design relieves the need for a rocket motor to extend gun range. Firing smaller, more accurate rounds decreases the likelihood for collateral damage and provides for deeper magazines and improved shipboard safety.

BAE Systems

Guidance. The HVP is claimed to be guided but that’s true only in a limited sense. The guidance is GPS and is applicable only against fixed, land targets with known GPS coordinates. Useful guidance is not possible against moving land targets or aerial targets due to the extreme speed of the projectile.

One of the “side effects” of speed is inertia. The faster an object moves, the slower and harder it is to alter its course. Faster means a larger turn radius. A WWI Fokker Triplane has immensely greater maneuverability than a modern F-16 because the F-16 has such high speed. An HVP traveling at Mach 7 cannot easily change course. An incoming cruise missile traveling at high subsonic speeds, for example, would be far more maneuverable than a Mach 7 HVP which is, for practical purposes in that scenario, ballistic and non-maneuverable.

Warhead. The HVP is currently a kinetic weapon with no explosive warhead. It must hit to kill. Various reports have suggested that an explosive warhead could be developed that would enable proximity fuzed projectiles for anti-air defense.

Cost. One of the much-ballyhooed claims about the HVP is the low cost per round compared to missiles. This is true but only in an unrealistic sense. The original cost of an HVP round was claimed to be around $25,000. The current cost estimate is $86,000 per round (1) though it is unclear what version and capabilities that cost represents. This is still much less than, say, a Standard missile but only in a one to one comparison. In a realistic engagement scenario the costs are much closer. For example, Breaking Defense offers an example in which each HVP is assumed to have a kill probability of 10% (pK=0.1) and 22 shots would give a 90% chance of killing the target. Well, 22 x $86,000 = $1.9 million dollars which is the same realm as a Standard missile. Thus, cost is not a clear cut advantage and it could turn out to be more expensive over the course of an engagement. Note that the 10% pK was a number made up by Breaking Defense for illustration purposes. There is absolutely no data for actual kill probabilities. Personally, without a proximity fuzed warhead, I’d estimate the pK to be 1%-5%, at best. If true, the cost “benefit” is even less.

Lethality. This is a difficult issue to quantify. Yes, we can calculate kinetic energy for the projectile but that’s only part of the story. Consider the example of a bullet fired from a handgun at a piece of paper. Based on the kinetic energy calculation, the paper should be vaporized and yet the only damage done is a hole the size of the bullet! Why? Because the kinetic energy wasn’t transferred to the paper target. More accurately, the bullet had POTENTIAL energy that wasn’t converted to actual kinetic energy upon impact (I’m grossly simplifying some physics here for sake of illustration). In simplistic terms, the paper did not offer enough resistance to the bullet to allow the bullet to convert its potential energy into kinetic energy on the target. The bullet passed through the paper, converting only a very tiny fraction of its potential energy, and retained most of its potential energy.

Similarly, if an HVP hits one of today’s thin-skinned warships or even thinner-skinned missiles, will the projectile be stopped, thereby converting all of its potential energy into kinetic energy and causing significant damage or will it pass through, like the bullet through paper, and convert only a portion of its potential energy to kinetic energy? The astute observer will note that the impressive videos of rail guns and HVP rounds always show the damage done to targets that are several inches to many feet thick of steel or some such material. What would happen if a rail gun HVP projectile impacted a 3/8” thick metal sheet, as is typical of a modern ship? Undoubtedly, the projectile would pass through, almost unaltered, leaving behind only a hole the size of the projectile. In other words, it would cause very little damage.

Now, in an actual ship, there would be multiple bulkheads (even thinner!) and pieces of equipment (really thin!) that the projectile would encounter on its path through the ship. Each would cause the projectile to “dump” some potential energy but would the cumulative effect be enough to achieve the massive energy conversion that would constitute significant damage? I have no idea but I suspect not. Of course, the projectile might also encounter flammable fluids leading to fires or sever pipes and electrical lines causing more damage. I suspect, though, that if a HVP were fired at a ship, it would pass straight through and cause relatively little damage. This is just semi-informed speculation on my part. One would hope that someone in the Navy has thought this through before we commit to this weapon. Of course, one would have hoped that we would have thought about galvanic corrosion on a ship (known about since the days of sail) and yet we failed to provide galvanic protection on the LCS so I make no assumptions about what the Navy should have considered.

Of course, one could imagine using a HVP with a contact fuzed explosive warhead. That would solve the problem of pass-through and provide localized damage effects. The 15 lb payload, however, drastically limits the magnitude of the explosive effect. It is also unknown whether the entire 15 lbs is available for explosive or whether a significant portion would be devoted to fuzing, electronics, etc. While the 15 lb compares favorably to the 5” gun round burst charge of around 8 lbs, the 5” round is a heavier walled shell which contains the burst and amplifies the damage effects versus a thin walled, uncontained burst. I have no idea what the wall thickness of the HVP is but I suspect it is not very thick.

All of this leads one to ask whether there is any actual gain in damage effects over those obtained from a conventional shell.

That takes care of anti-ship lethality. Next, let’s look at land attack.

For a specific, hard target such as a building or hangar, the kinetic HVP will likely cause significant damage. However, it has a significant limitation in that a near miss will cause no damage. The projectile will simply bury itself in the ground. There is no explosion. It’s a case of exact hit or no damage. Conversely, a conventional round with an explosive warhead may well cause damage from a near miss due to the explosive effects and shrapnel. Of course, a warhead could be added to the HVP but with a payload of only 15 lbs, it wouldn’t be much of an explosion. Thus, the HVP looks to be an excellent choice for a specific, hard target but of limited use in general bombardment and useless for suppressive fire (one of the major uses of naval gun fire).

I have been unable to determine which HVP warheads other than the kinetic (inert) version actually exist, if any. My impression is that all are just proposed versions.

In summation, the HVP appears to be a potentially useful weapon for a limited target set, primarily fixed, hard, land targets. The projectile is very long on claims and proposals and very short on demonstrated performance, as is typical of new, developmental weapons. It is well worth continued development but appears to be well short of being the miracle weapon that its hype would suggest.

This is one of those subjects that some readers may have more current information on than I do. If so, feel free to add information via the comments. Additions will be greatly appreciated. Just be sure to offer supporting documentation.

(1)Breaking Defense, “$86,000 + 5,600 MPH = Hyper Velocity Missile Defense”, Sydney J. Freedberg, Jr., 26-Jan-2018,

https://breakingdefense.com/2018/01/86000-5600-mph-hyper-velocity-missile-defense/

(2)BAE Systems website,

https://www.baesystems.com/en-us/product/hyper-velocity-projectile-hvp

Source: navy-matters.blogspot.com

Mk 45, five-inch main deck gun