September 28, 2020: The U.S. Air Force recently tested the 155mm version of its HVP (Hyper Velocity Projectile) fired from an army M-109 self-propelled 155mm howitzer. The HVP hit an incoming target drone standing in for a Russian cruise missile. The target was destroyed. In 2018 the U.S. Navy fired twenty of the smaller (127mm) HPV projectiles from a navy five-inch gun, a weapon found on all navy destroyers and cruisers.  Apparently, this test did not involve testing the HVP guidance system against airborne or moving targets.

The HVP is a guided projectile with a max range of about 80 kilometers and a top speed of Mach 7.3. That’s 2,500 meters a second, more than twice as fast as a high-powered rifle bullet. No information was released on the accuracy of the 127mm HVP or whether any of them hit a target. The HVP is fired from a cannon using a powder charge, just like a normal shell. But the HVP is in a casing that is discarded once it leaves the barrel of the gun. The HVP shape is streamlined to reduce air resistance and enable higher speed when its rocket motor fires. A 155mm shell leaves the cannon barrel at about 800 meters a second. The HVP rocket motor boosts that to 2,500 meters a second and the guidance system intercepts the target at high speed, destroying the target without need for an explosive warhead. The key element is the guidance system and that seems to be working now.

The navy is eager to use an accurate HVP on its ships because the 5-inch gun can fire up to 15 shells a minute. If the ship fire control system can find targets fast enough for the HVP, this is a much cheaper ($90,000 per shell) way to defeat missile attacks. The existing ESSM missiles used for this cost a million dollars each.

No details have been released on the current fire control capabilities for aiming the cannon firing an HVP shell so that its guidance system will detect and home in on the target. One thing is certain, a 155mm HVP shell can detect and destroy an incoming cruise missile, even if under carefully designed test conditions. Cruise missiles can be equipped with countermeasures to spoil the aim of an HVP. In theory, if HVP can take down a cruise missile it would be deadly against helicopters or jet fighters. Any 155mm howitzer could use an HVP against a wide variety of targets where speed is a factor. The only problem is making the target detection and fire control effective and reliable enough to provide targets when needed.

Range of the intercept was not released nor was the max effective range of the HVP. This involves at what distance can the speed of the HVP still be high enough, and the guidance system accurate enough, to intercept an incoming missile. That aspect of the cannon-launched HVPs appears to be a work-in-progress. HVP in general has been a work-in-progress for decades and that may continue for decades more. Despite that, technologies like this tend to “mature” (get all the bugs and deficiencies worked out) eventually, especially if there is regular progress in those areas. That is the case, so far, with the cannon fired HVP.