Risk area estimations for Vidsel Air Base

This work aims to give the foundations for risk area assessments for fighters landing with failed munition GBU12 (with the Mk82 warhead). These kinds of assessments are essential to be allowed to fly with live munitions at Vidsel air base. The three folded task was to calculate fragment density and risk area from a detonating GBU12. Firstly only a plane ground surface was considered, secondly the correct topography was used and the bomb was located at the designated hardstand and thirdly a new suggested location for the hardstand was evaluated. The tools SWERISK and AVAL were used to calculate the risk area. All simulations were based upon one single detonating GBU12 and the carrying fighter aircraft was neglected. Neglecting the fighter also means neglecting the protection it gives for fragment distribution, which can be considered as a worst case scenario. Aircraft debris was also neglected, which is not assumed to influence the risk area. There was a good correlation between the results from the two tools regarding radial fragment distribution. The results from SWERISK showed a narrower risk area in the bomb's principal axis than the AVAL results do. This is due to a lack of fragments ejected forward and rearward from the SWERISK model of the bomb. All calculations indicated a large risk area. At the current hardstand, SWERISK gave maximum fragment distances (impacts on ground) of 1065 m to the side, 360 m rearward and 460 m forward of the bomb. The corresponding AVAL results were 1120 m, 970 m and 820 m. The risk areas found for the new suggested location of hardstand were of the same magnitude as for the current. However, in this case it was directed differently and the central air base part with buildings was outside the SWERISK risk area, but the public road to the south was still within the risk area. The risk area calculated with AVAL also covered some of the buildings and the public road in the north, with low fragment densities. The new suggested location for the hardstand is better than the current from a fragment distribution risk point of view. It reduces the probability of hitting air base buildings and public roads with fragments. It does not reduce the risk during landing and the distance to run on the taxiway is increased.