Computational analysis improves I-500 warhead survivability

  • Published
  • By Brian Plunkett
  • Air Force Research Laboratory Munitions Directorate
EGLIN AIR FORCE BASE, Fla. --  Air Force Research Laboratory engineers conducted dynamic computational analysis geared towards improving the survivability of a proposed I-500 warhead design. The intent of this warhead is that it provide hard-target penetration capability while duplicating the properties of mass (i.e., 500 lb weight), external dimensions and external interfaces that are hallmarks of the Mk-82 general-purpose bomb. 

By designing the I-500 weapon according to these constraints, engineers were able to forgo the flight certification process required for new warheads, decreasing both program costs and the time needed for transitioning the technology to the warfighter. The advanced computational analysis methods employed for this effort enabled assessment of the warhead's performance throughout its penetration of a hardened target.

The I-500 concept consists of a hardened penetrator encased in a lightweight composite shroud that captures the outer moldline of the Mk-82. It also includes an arming well cut into the side of the penetrator's steel casing in order to accommodate standard cable attachments for fuze arming and thereby match existing external interfaces of the Mk-82. AFRL's dynamic structural analysis of the I-500 predicted that significant localized deformation around the arming well hole would occur during oblique penetration into a hardened concrete target. Such deformation would indicate a very high risk of warhead case fracture, an event likely to precipitate catastrophic systems failure.

Based on these results, AFRL engineers subsequently redesigned the I-500 for enhanced survivability. In order to mitigate the risk of structural failure during penetration, AFRL's design improvements included recommendations to locally increase case thickness near the arming well hole (providing extra stiffness), repackage the fuze-arming unit inside the arming well (reducing the hole's diameter by approximately 20%), and add a tip to the originally blunt nose (decreasing deceleration loads during penetration). Ongoing computational analysis suggests that these changes should significantly increase the warhead's structural survivability during its penetration into hardened targets. The new design is slated for sled test during the summer of 2008.