Complex sentence: A launch capsule is used to carry a submarine-launched missile from the attacking submarine through the distance of water up to the ocean surface, immediately after which the capsule is jettisoned, as the missile continues its journey propelled by the booster motor.
Split into simpler sentences: A launch capsule is used to propel a submarine-launched missile to the ocean surface. Upon reaching the surface, the capsule is jettisoned, and the missile continues its journey propelled by the booster motor.