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 DETAILED MISSION DESCRIPTION

Figure 13 illustrates the orientation of the space vehicle on the launch pad. The spacecraft's -Z axis (direction of crew's heads), and the launch vehicle's Position I are pointing east. In the event of a pad abort at this point, the orientation is such that the trajectory of the launch escape vehicle would take the Command Module over the water.

The inner gimbal of both the spacecraft's and launch vehicle's Inertial Measurement Unit (IMU) are aligned normal to the upcoming orbit plane.

EARTH ASCENT

Lift off occurs after a 6-second hold down period following engine ignition (Figures 14 and 15). During this time, the thrust of the first stage, which is powered by five F-1 engines, has built up to its rated value of 72 million pounds. The thrust-to-weight ratio of the vehicle at this point is 1.25, so its initial ascent acceleration is relatively small.

The space vehicle rises vertically from the launch pad until the mobile launcher is cleared. It then performs a roll maneuver to align the launch vehicle Position I along the desired launch azimuth, which can vary between 72° and 108°. The orientation on the pad was such that Position I was pointing east.

Following the vertical rise period, which lasts 12 seconds, a programmed pitch is commanded which will continue throughout the first stage burn. Maximum dynamic pressure (700 psf) is reached at about 84 seconds at an altitude of 43,000 feet. The inboard engine cutoff of the first stage will occur about 155 seconds after liftoff and will be followed by the outboard engines' cutoff four seconds later. During this first stage operation, the spacecraft will have attained an altitude of about 200,000 feet and will be about 65 nautical miles down range. Maximum acceleration will have occurred at this point and amounts to about 4½ g's. Tracking and communications will have been continuous during this period with the ground-based facilities in the Cape area and with the facilities at Grand Bahama during the latter portion of the burn.

Since the launch vehicle operations during this period are automatic, the crew has been functioning in mainly a capacity of monitoring launch events and communicating the occurence of these events to the ground. Critical spacecraft systems