SE stands for sustainer engine. It is the primary rocket engine that continues to fire and accelerate a spacecraft or missile after the initial strap-on boosters or first-stage engines have depleted their fuel and detached. It is optimized for efficiency in the thinner upper atmosphere or vacuum of space.
Heard on the job
Telemetry confirms booster separation and nominal SE performance.
Related terms
Sustainer
A rocket engine designed to burn continuously from liftoff through the later stages of ascent.
SECO
The exact moment a launch vehicle shuts down its sustainer engine.
SES
The moment a launch vehicle ignites its sustainer engine.
Strap-on
An auxiliary rocket booster attached to the side of a core launch vehicle to provide extra thrust at liftoff.