(S² KIKAN) 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 from
Eva-05 onward are also equipped with S² engines and thus do not need
umbilical cables.
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.