Protecting sensitive systems to put the punch in guided artillery shells
How do you keep a sensitive guidance system from getting smashed to smithereens as it goes from 0 to more than 1,000 mph on the tip of an artillery shell? The answer: bulletproof electronics.
The key to the modern Excalibur® precision-guided projectile is Raytheon’s method for protecting its flight-control and global positioning systems as troops fire it from a howitzer. Excalibur was called a “magic bullet” for its ability to fly 30 miles and score a direct hit.
“Demands of the gunfire environment are severe, with extreme force and acceleration at play,” said Mark Hokeness, Raytheon Excalibur program director. “To withstand the shock of firing, we’ve perfected a technology of strengthening and flexing appropriately. We call it gun hardening.”
Engineers from Raytheon and its network of suppliers developed a process that encases the weapon’s GPS guidance and electronics package in a “hockey puck” filled with a putty material to hold the equipment in place during firings.
According to Hokeness, one of the secrets to gun hardening is keeping things small.
“Less mass is better,” he said, adding that the design allows the electronics to survive 15,000 times the force of gravity as the shell leaves the gun.
The projectile streaks out of the barrel, its base spinning as it goes. Fins and canards -- small surfaces that help steer the shell -- pop out. The GPS determines its position and the precision-guided projectile begins its 25- to 30-mile journey.
The shell's flight ends with a nearly 90-degree descent to the target. The projectile can be set to explode above the target, upon contact or after penetrating a roof or other structure.
Excalibur is cost-effective because it can replace aircraft in challenging, close-in operations.
“Excalibur gives ground forces the ability to rapidly respond to threats and engage longer-range targets -- targets that previously could only be engaged with close air support,” said Joe Peterson, vice president of business development for Raytheon's Land Warfare Systems.
The company continually works with suppliers to reduce the cost of the projectile. Over the years, Raytheon has cut Excalibur's cost by 60 percent, all while increasing its capabilities and range.
“When considering a total-mission cost of a precision strike, Excalibur is the only weapon system that a commander has available today and can call on 24/7, all-weather,” said Paul Daniels, an Excalibur business development manager.
U.S. forces have fired more than 760 Excalibur rounds in support of combat operations, from destroying foot bridges used by attackers to blowing up bomb workshops.
Raytheon has developed the Excalibur Shaped Trajectory, or EST, variant to enable soldiers to reach targets in hard-to-reach locations by selecting the projectile's terminal or final phase attack angle. It was successfully tested in 2018 and is now being deployed to U.S. forces.
The company is also developing a laser-guided version of the projectile, the Excalibur S. This variant incorporates a digital, semi-active, laser seeker, allowing it to hit engage and strike even moving targets without accurate location information. It also reduces the risk associated with GPS jamming.
Additionally, the company is developing a sea-based, five-inch variant called the Excalibur N5. The Excalibur N5 is expected to more than double the maximum range of conventional five-inch munitions and will provide the same accuracy as the land-based version.
“We see an opportunity to leverage a highly successful, mature program in the Army and Marine Corps to fill that capability for the Navy very affordably and quickly,” Daniels said.