An Cosantóir the official magazine of the Irish Defence Forces and Reserve Defence Forces.
Issue link: https://digital.jmpublishing.ie/i/107373
24 | in reserve GunDog A fire-control system for the 120mm mortar T he Ruag 120mm mortar, introduced to the Defence Forces in late 2008, has become the primary artillery fire-support weapon for overseas deployments and is currently deployed with our troops in Lebanon. It is capable of firing a 14kg projectile out to a range of almost 8km. While this is a long way short of the 17km range offered by the 105mm howitzer, the compact size of the An Cosantóir Feb 2013 www.dfmagazine.ie Report by Capt Dave Power (31 Res Arty Regt) Main Image Armn Jason Byrne mortar system has made it the weapon of choice for such deployments. This article describes the development of a system to calculate firing data for the mortar. It is called 'GunDog', a name derived from the fact that the first version ran on a 'Husky' handheld device, similar to the type used by the 'MorFire' system. The Artillery Corps uses a range of modern survey equipment to accurately determine the location of each gun or mortar to the nearest metre. It also has an array of equipment, including tripodmounted, laser rangefinders, AMSTAR ground radar and LTAVmounted OP suites that can accurately determine a target location to within five metres. To tie all of these elements together to deliver accurate fire on the ground, a computerised fire-control system is required to calculate mortar firing data. Graphical plotters for determining firing data were provided along with the mortars. On these the operator marks the battery centre and the target on a 50cm plastic disc that is then rotated to determine the bearing to the target. The elevation is determined by measuring with a ruler graduated with charge and elevation data. This system is simple and easy to learn but has a number of limitations: the plotting resolution is 50m, the system is comparatively slow, and doesn't take the displacement of each individual gun into account. Furthermore, it only computes centre-to-centre data, and isn't capable of calculating sheaf, linear or converged fire patterns. The Artillery School initially sought to upgrade its 'GunZen MkIII' systems to compute data for the new mortars. However, since Switzerland was the only other country in the world that used the Ruag 120mm, no off-the-shelf fire-control solution existed for it. The cost of having a custom module written for the 'GunZen' was investigated but proved prohibitive. When people consider how the skills of personnel serving with the RDF can benefit the Defence Forces, their first thoughts usually turn to one of the other corps such as CIS, logistics, medical and engineering. It is usually the case that civilian qualifications are not officially recognised by the Defence Forces but there is a tacit understanding that an RDF member who has specialist skills, say, for instance, in installing data networks, would be of immense value in a corps such as CIS. To most, however, it is not immediately obvious that there could be civilian skills, which are of use to the Artillery Corps. The Artillery School has always been keen to make the most of its RDF assets. RDF gun crews are often mixed with PDF batteries