Guided Ammo... Guided ammunition stepped relatively late into the history of howitzers, because this involves electronics that have to resist not only the crushing effect of firing, but also the devastating twist effect imparted by the rifling. In addition, receivers able to rapidly catch GPS signals under such circumstances and upon exiting the muzzle still needed to be invented.
Used in action by US forces, Raytheon’s Excalibur has been fired from M109A5 Paladins and M777A2s. (US Army)
US Army artillerymen get ready to shoot an Excalibur round. In production since April 2014, the Ib version is cheaper but more accurate. (US Army)
T
he first XM982 Excalibur was fired in May 2007 by an M-109A6 Paladin howitzer close to Baghdad; developed by Raytheon, together with BAE Systems Bofors and General Dynamics Ordnance and Tactical Systems, the round has a guidance unit just behind the fuse, followed by the guidance section featuring four canard wings opening forward. The round’s rear end is equipped with a base-bleed aggregate and rotating stabilization wings. In the ascending part only inertial sensors work, canard wings being deployed when the round reaches its apogee, instants after the GPS receiver is activated. Mid-course trajectory is then optimised according to target grids and time of arrival, canard wings allowing not only to direct the round but also
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Compendium Artillery 2015
providing sufficient lift from the body ensuring shaped trajectories, increasing the range compared to standard ammunition. The terminal trajectory is then optimised according to the type of warhead and target. Increment Ia-1 rounds used in Iraq and Afghanistan lacked the base bleed aggregate their range being limited to 24 km. Data from the field showed a reliability of 87% and accuracy better than 10 metres. With the addition of the base bleed Increment Ia-2 rounds, known as M982, could reach targets well over 30 km. Reliability problems with Modular Artillery Charge System (MACS) propellant charge 5 limited however its range; deployed to Afghanistan in late 2011, they were fired with charges 3 and 4. These first Excalibur rounds attracted heavy criticism
for their cost, which was also due to the reduced acquisition of Ia-2 rounds from 30,000 to 6,246 units. Since 2008 the US Army sought improved reliability and lower costs, issuing two design and maturation contracts. It selected Raytheon in August 2010 to fully develop and produce the Excalibur Ib, which in April 2014 replaced the Ia-2 on Raytheon’s manufacturing lines, and is now in full-rate production. According to the company the price has been cut by 60% while capabilities have been increased, acceptance tests having shown 11 rounds falling at an average distance of 1.26 metres from the target, and 30 rounds falling at an average 0f 1.6 metres. Overall 760 combat shots have been fired between Iraq and Afghanistan. The Excalibur features a multi-role fuse which can be programmed as point detonation, point detonation delayed, or air burst. Besides the US Army and Marine Corps, the Excalibur is in service also with Australia, Canada and Sweden. For the international market Raytheon decided to develop a round, the Excalibur-S, which also featured a laser seeker, providing semi-active laser homing capability. First testing was carried out in May 2014 at Yuma Proving Ground. Following the same guidance steps as the Excalibur, it activates its laser seeker in the last phase to lock onto the coded laser beam reflection. This allows to