Atlas MA engine series

Series of Atlas rocket engine packages that consisted of the two booster engines of the missile, which flanked a single sustainer engine. At the end of the boost period, the MA section would slide away on rails, leaving the single sustainer engined to continue on to burnout. This provided the Atlas ICBM or orbital capability in a '1 1/2' stage layout that allowed all engines to be firing at liftoff, removing the difficulties of in-flight ignition a second stage would have to face.