Launch Escape System
The Launch Escape System (LES) consists of the Boost Protective Cover (BPC) over the Command Module (CM), the attached Launch Escape Tower (LET) and associated electronics and pyrotechnics.
Launch Escape Tower
The LET contains three solid rocket motors.
The Abort Motor is the largest, positioned at the bottom of the tower with four exhausts pointing out at angles to deflect the blast away from the BPC. This is used in the event of a life-threatening emergency to pull the CM away from the rest of the Saturn stack.
The Jettison Motor is smaller and positioned near the top of the tower, with two exhausts at angles out of the sides of the tower. This is used on every mission, either to jettison the tower from the Saturn in a normal launch, or to jettison the tower from the CM in an abort.
Note that the Jettison Motor nozzles are angled relative to the center of gravity to ensure that the jettisoned LES follows a curved path away from the CM to avoid a later collision. Note also that when the LES is jettisoned after an abort, a cable attached to the LES will pull the Docking Probe away from the CM to allow the parachutes to deploy properly.
The final motor is the Pitch Motor, which is used in some abort profiles to turn the CM so that the heat shield is correctly oriented for re-entry.
Boost Protective Cover
The function of the BPC is explained by its name. It's a simple cover fitted over the CM to protect it from atmospheric heating during the 'boost' phase of the mission from launch until the Saturn leaves the dense parts of the atmosphere, with a secondary function of protecting the CM against the Abort Motor exhaust in the event of an abort.
While the BPC was essential in a real Saturn flight, in Orbiter it serves no function other than to prevent you using the parachutes while it is attached.
Notes
If you switch focus to the jettisoned LES in a normal (non-abort) launch, it provides a good vantage point to watch the Saturn fly past.
