Japan is developing two advanced anti-surface warheads that will be fitted onto two hypersonic weapons that are currently also under development, as indicated by several documents obtained by Jane's from the Ministry of Defense (MoD) in Tokyo.

The MoD's Acquisition, Technology, and Logistics Agency (ATLA) plans to arm these weapons, namely the Hyper Velocity Gliding Projectile (HVGP) and the Hypersonic Cruising Missile (HCM), with the 'Sea Buster' tandem-charge warhead and a multiple explosively formed penetrator (MEFP) warhead, according to the documents.

The warheads are designed to "attack warships and military vehicles deployed around/on the small islands and their surrounding sea area" according to one of the documents in a possible reference to Japan's more remote islands in the East China Sea.

The 'Sea Buster' warhead is being specifically developed to target enemy surface vessels, most likely larger warships, according to the documents. It is composed of a main warhead, which carries armour-piercing high-explosive shells and a nose fuze, and a precursor warhead that uses shaped charges.

Artist renderings depicting this warhead targeting large surface vessels have appeared in several ATLA documents and pamphlets obtained by Jane's . For instance, last year the ATLA published its 'R&D Vision', which contained an artist's rendering of the HCM targeting an enemy aircraft carrier. A text accompanying the image referred to Japan's development of an advanced highly effective penetration warhead that can damage the deck of an aircraft carrier or be used for "area suppression".

The MEFP warhead is being designed to engage surface vessels and both stationary and mobile ground targets, with the ATLA saying in one of the documents that one such warhead will be able to release dozens of hypervelocity metal fragments capable of striking several targets.

This image taken from a Japanese MoD report shows an artist's rendering of, among other things, Japan's future HCM targeting an enemy aircraft carrier. (Japanese MoD/Kosuke Takahashi)