Synchronous Multilayer Bomb

A Synchronous Multilayer Bomb (多層同期爆弾) is a type of tactical weapon created in Academy City. It was part of 's conspiracy to assassinate Aleister Crowley.

Principles
It is a large bomb that has a number of high power explosives arranged in a regulated manner. A normal tactical weapon spreads an enormous blast over a large area while the synchronous multilayer bomb was made to focus a highly destructive blast on one small target so as to utterly destroy it. It was created in order to bomb an enemy stronghold in an urban environment with no civilian sacrifices.

Toaru Kagaku no Railgun SS: Liberal Arts City
Synchronous multilayer bombs were among the bombs loaded into the HsB-02s which were on standby during the attack on the Liberal Arts City by the Return of the Winged One while Academy City students were on a trip there, intended by the higher-ups to destroy the island and only recover Level 5 Misaka Mikoto, should the need arise.

Battle Royale Arc
wanted to set off one of these bombs inside the Windowless Building in an attempt to kill Aleister Crowley. They planned this in an attempt to stop the chaos in the world from turning into a war. As the Windowless Building was impervious to even a nuclear attack they wanted to discover the route through which materials are brought into the windowless building. To do this they attacked the Reformatory in an attempt to take the Move Point's companions hostage and use them as leverage to find her identity. Once this was done they planned to negotiate with her to find the route they needed. In the end, however, was able to defeat  and stop their plans.