The Meson Cannon (メソンカノン)[1] was an energy weapon produced by Aurelia for the Atmos Ring. Aurelia built eight Meson Cannons, but did not complete them. Leasath installed and used the Meson Cannons after capturing Griswall in the Aurelian War.


A Meson Cannon preparing to fire

The Meson Cannons are particle-beam weapons that fire charged muons. The Atmos Ring can generate charged mesons by firing accelerated proton beams at certain materials (including aluminum and beryllium). These mesons decay into muons, and each Meson Cannon can emit the muons in a specific direction using linear particle accelerators in a tower and gun barrel.[1]

The Meson Cannons are highly-effective weapons. Their beams fire at just under the speed of light, so if they precisely aim at a specific target, it is nearly impossible to avoid their attack. The Meson Cannons's beams do not create secondary emissions harmful to humans, unlike nuclear weapons. The cannons can defend any site from long-range attacks such as ICBMs, and they cannot run out of ammunition.[1]

Despite their effectiveness, the Meson Cannons incur drawbacks due to their design. Their use of cutting-edge technology makes the cannons very expensive to produce. Muons themselves decay at a fast rate, so the beams have a short range of only a few kilometers. In addition, while the cannons can move to change their beams's emission direction, they cannot quickly move at steep angles like lasers. Enemy fighter aircraft can use this vulnerability to their advantage to destroy the cannons.[1]

The muons generated by the Atmos Ring's accelerated proton beams have a very short lifespan. They manifest only as short bursts as a result, limiting the effectiveness of the Meson Cannons. They would only be able to fire pulse shots. Aurelian engineers at the Monte Breeze Industrial Area developed the Meson Beam Stabilizing Regulator to solve the muon decay problem, which would allow Meson Cannons to fire a continuous beam of charged muons.[2] Even with MBSRs installed, the Meson Cannons could not fire beams at a longer range.[3]


Meson Cannon beams over Griswall

Aurelia designed the Meson Cannons to use the Atmos Ring to defend Griswall from enemy attacks. However, Aurelia was historically a peaceful country and had no reason to install the Meson Cannons.[1] Coupled with their high development costs and the political concerns with neighboring countries, Aurelia canceled their development.[4]

When Leasath captured Griswall in the early stages of the Aurelian War, they retrieved the Meson Cannons and installed them on the Atmos Ring. They prepared to use the cannons to defend against any Aurelian attempts to liberate Griswall.[5] Leasath also captured the Meson Beam Stabilizing Regulators at Monte Breeze. They attempted to transport the regulators to Griswall to strengthen the Meson Cannons, but Gryphus Squadron shot down all of the transports.[6][note 1]

Soon afterward, the Aurelian Liberation Corps entered Griswall and temporarily drove Leasath forces out of the city. They captured the Atmos Ring and attempted to disable the Meson Cannons. While Gryphus Squadron and Ninox Squadron entered the area, Leasath soldiers fired the Meson Cannons at them. They successfully shot down Ninox 2 before the ALC shut down all power to the Atmos Ring. Without any power, the Meson Cannons could not fire. This opened an opportunity for Gryphus One to destroy all of the Meson Cannons.[5][note 1]



  • The Meson Cannons are arrayed in a similar layout to Stonehenge.
  • "Meson Cannon" is a misnomer, since the cannons actually fire muons decayed from mesons.


  1. 1.0 1.1 The mission-specific information adheres to the canon guidelines set in Acepedia:Canon § Ace Combat X branching paths.


  1. 1.0 1.1 1.2 1.3 1.4 ACE COMBAT X -> 用語解説 (Glossary) -> メソンカノン (Meson Cannon). Retrieved on 24 April 2018.
  2. ACE COMBAT X -> 用語解説 (Glossary) -> MBSR. Retrieved on 24 April 2018.
  3. Atmos Ring, Ace Combat X: Skies of Deception.
  4. ACE COMBAT X -> 用語解説 (Glossary) -> アトモスリング (The Atmos Ring). Retrieved on 24 April 2018.
  5. 5.0 5.1 Wild Card, Ace Combat X: Skies of Deception.
  6. Joint Operation, Ace Combat X: Skies of Deception.