Engineers at Picatinny Arsenal are seeking to potentially extend the range of cannon artillery with new manufacturing methods that improve artillery shells, allowing them to withstand higher launch velocities and temperatures.
In an artillery shell, the driving band or rotating band is a band of soft metal near the shell's bottom, often made of gilding metal, copper, or lead. When the shell is fired, the pressure of the propellant forces the metal into the rifling of the barrel and forms a seal. That seal prevents the gases from blowing past the shell, and engages the barrel's rifling to spin and stabilize the shell.
Current copper rotating bands for artillery projectiles are designed for 39 caliber gun systems. Historically, copper was used as the rotating band material due to its properties and ability to survive gun launch with minimal damage to the gun tube.
However, when these copper rotating bands are used for extended range, 50+ caliber systems, they do not survive the high launch velocities and temperatures. The solution includes both new materials and new manufacturing methods that don’t now exist in the industrial base.
“A lot of what we learned about why we need this project was learned during the Crusader era,” said Joseph Paras, a materials engineer, referring to a program for a self-propelled howitzer.
“We knew that to go out to larger calibers or extended ranges, the materials we were using wouldn’t survive. That was really the impetus for advanced manufacturing,” said Paras, who is with the Combat Capabilities Development Command Armaments Center, which is part of the Army Futures Command.
The objective of the project is to evaluate several manufacturing technologies to achieve the required rotating band performance for extended ranges, which is critical to the performance of the munition.
“We have some good guesses on manufacturing technologies that would work. We just need to do the prototyping and analysis to verify,” Paras said.
Different metal deposition approaches and technologies will be evaluated to determine the best one. Methods being studied include:
- Synchronized dual-torch arc welding, which would lower the electrical current required and thus reduce the amount of steel melted into the projectile body.
- Deposition of multiple materials to utilize the best performance characteristics of the individual materials.
- Non-traditional welding including laser welding, which would control the characteristics of the melt pool better than arc welding.
- Emerging technologies including cold spray, which would join normally incompatible materials, without melting, to create unique material properties.
A combination of manufacturing processes will also be studied. For example, welding a standard rotating band followed by cold spray to deposit a second material adjacent or on top of the first material. All manufacturing processes will be evaluated for performance and cost as preparation for low rate initial production.
A relatively new repair technique, known as high-pressure cold spray, could be a great engineering asset when applied to depositing metal for the rotating band, Paras said. The cold spray application process has become one of the military’s solutions to corrosion damage and dimensional restoration.
According to the U.S. Army Research Laboratory, “researchers use high-pressure gases to accelerate metal particles at supersonic velocities onto the target surface. Upon impact, the particle deforms and flattens out as it binds to the substrate. A high-pressure cold spray machine can deposit layers upon layers of material onto vehicle parts to fill in cavities and coat surfaces.
“Since cold spray doesn’t require heat to bind the materials, maintenance units can perform repairs on thermally sensitive components that would normally melt or otherwise be compromised with a traditional approach like thermal spray or welding.”
While the cold spray application might be a viable approach, engineers will evaluate a variety of options to determine the best solution.
“If we can use new materials, using an existing process, that would the most bang for our buck,” Paras said.
Engineers hope to achieve several objectives, including a manufacturing solution for a rotating band used on a family of extended range munitions, including the XM1128 and XM1155, developing a manufacturing process that can be adapted for other 155mm and 105mm systems, and providing technical data packages for all ordnance solutions.
“This project is going to be tied to the XM1113,” Paras said. “That’s really the target, but in terms of adapting it to other systems, whatever we learn here can be applied to other 155mm or 105mm systems.”
Paras said that the project’s proposed timeline spans from the beginning of fiscal year 2021 until 2024. The plan is to then transition to Program Executive Office Ground Combat Systems; Project Manager Combat Ammunition Systems, and Project Manager Towed Artillery Systems, in support of next generation longer range cannons. Scranton Army Ammunition Plant will be the transition point for production.