A power generation system explained by the super-solenoid theory
advocated by Dr. Katsuragi. When an Evangelion
is equipped with this system, its operational time limit is extended to infinity
. All the Angels
have S² engines
, and Eva-01
acquired one when it devoured the 14th Angel
. Moreover, all Evangelion Mass-Production Models
onward are also equipped with S² engines and thus do not need umbilical cable
Source: The End of Evangelion : Glossary contained within The End of Evangelion - Theatrical Program.
Please note that the '2' in S2 is in superscript, as in 'S²', in the original program, however to ease the discovery of this write-up the node title is listed as simply S2.