Besides serving as the thrust agent for the missile, propellants were also important in missile control. For example, the thrust unit effected roll control by  deflecting the exhaust gases from the turbine and swiveling the turbine exhaust nozzle. A second unit was the vernier thrust system that was mounted on the aft  section of the body to provide fine control of cutoff velocity of the body immediately after separation from the thrust unit. This was accomplished by a solid  propellant unit rated at 500 pounds of thrust and capable of operating for 20 seconds. While the missile was out of the sensible atmosphere and had already  separated from its thrust unit, eight jet nozzles equally spaced on the missile body provided pitch, yaw, and roll. These jets were off-on types, and were powered  by nitrogen from storage bottles housed in the body. This formed the spatial attitude control system. To depict the operation of the propulsion system during a typical flight, the missile was launched vertically and then was tilted gradually by a guidance program  device into a ballistic trajectory. Trajectory was divided into four major phases: main power, vernier, spatial attitude control, and re-entry. While in the main power  phase, the missile was controlled in pitch and yaw by hydraulically activated swiveling of the rocket engine, and in roll by the thrust unit roll control system.  Separation of the body and thrust unit then occurred when the main rocket engine cut off, and then the missile was in its vernier phase. The vernier engine now  operated to control missile velocity along the trajectory until the slant range computer in the G&C was satisfied. All during this time, the spatial attitude nozzles were helping maintain control,  _____________________________