sustainer engine
rocket engine which remains with a spacecraft during its ascent after booster engines have separated from the spacecraft
en-GB/səˈsteɪnə ˈɛnd͡ʒɪn/
en-US/səˈsteɪnɚ ˈɪnd͡ʒən/
rocket engine which remains with a spacecraft during its ascent after booster engines have separated from the spacecraft