Continuous-rod warhead

A continuous-rod warhead is a specialized munition that exhibits an annular blast fragmentation pattern. It is used in anti-aircraft and anti-missile missiles.

Construction

An even number of individual steel rods are arranged in parallel to form a cylinder. The ends of the rods are welded together—the first rod and the second rod are welded together at the top, the second and third at the bottom, and so on all the way around the form.

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Left: Rods arranged on mandrel prior to welding (single layer shown)

Center: Alternating welds completed and ready to receive explosives

Right: Representation of rod expansion due to detonation of explosives

Far right Use illustrated

Operation

Arena firing of continuous-rod warhead, 1972 at Naval Air Weapons Station China Lake.

When detonated, the high explosive imparts a momentum to the rods, thrusting them outward in an expanding circle. The rods are sufficiently soft (ductile) to allow the expansion without breaking the rods or the welded joints, the rods instead bending at these locations. At some intermediate point the ring will have a zig-zag (alternating direction) appearance within a cylindrical envelope. Upon ultimate expansion the ring is circular and contained within a plane. The ring will then break and ultimately tend to form one or more straight rods. Since the net momentum of the rod relative to the missile is roughly zero its effectiveness will rapidly diminish as the broken ring expands.

This rapidly expanding ring is more effective against aircraft than conventional fragmentation. Any portion of the aircraft intercepted by the expanding ring will be cut through. This only works as long as the ring is unbroken, so multiple layers of rods are employed in practical weapons to increase the effective radius.