Artifact: Sequence Controller, Master Events (MESC); Apollo Command Module, Block II

An Apollo Command Module (Block II) Master Events Sequencer Controller (MESC) which was a component of the spacecraft's Sequential Events Control System (SECS) subsystem. The SECS regulated automatically sequenced functions during mission ascent, entry, flight and in the event of an abort. 2 MESC's were installed as part of redundant SECS "A" and "B" systems. The MESC governed activities included Launch Escape Tower (LET) jettison, Service Launch Adapter (SLA) separation, Command Module/Service Module (CM/SM) separation and Earth Landing System (ELS) deployment; and directed Launch Escape System (LES) actuation and Service Propulsion System abort modes. As the Master Controller for the SECS, MECS interfaced with and commanded the following controllers: Emergency Detection System (EDS), SM Jettison Controller (SMJC), Lunar Module Separation Sequence Controller (LMSSC), Command Module Reaction Control System Controller (RCSC), Earth Landing Sequence Controller (ELSC) and the Translation Controller.

The MESC and the other SECS controllers received power from the spacecraft Entry and Post Landing batteries (these intern were charged from power provided by the Service Module Fuel Cells). The SMJC, RCSC and ELSC are further detailed as artifacts in this collection in subsequent entries following discussion of the MESC.

Part of the CM/SM separation process include the destruction of the CM to SM wiring umbilical. A prerequisite to this action was to "open" certain circuits known to be hot (i.e. active with electrical signals/current flow). To accomplish this, an additional responsibility of the MESC was to trigger pyrotechnically actuated  interrupters to dead-face these hot circuits in conjunction with CM separation from the SM.