On an orbital mission, the Atlas' rocket engines were ignited four seconds before lift-off. The launch vehicle was held to the ground by clamps and then released when sufficient thrust was built up at lift-off (A). After 30 seconds of flight, the point of maximum dynamic pressure against the vehicle was reached, at which the astronaut felt heavy vibrations. After 2 minutes and 10 seconds, the two outboard booster engines shut down and were released with the aft skirt, leaving the center sustainer engine running (B). At this point, the launch escape system was no longer needed, and was separated from the spacecraft by its jettison rocket (C). The space vehicle moved gradually to a horizontal attitude until, at an altitude of , the sustainer engine shut down and the spacecraft was inserted into orbit (D). This happened after 5 minutes and 10 seconds in a direction pointing east, whereby the spacecraft would gain speed from the rotation of the Earth. Here the spacecraft fired the three posigrade rockets for a second to separate it from the launch vehicle. Just before orbital insertion and sustainer engine cutoff, g-loads peaked at 8 g (6 g for a suborbital flight). In orbit, the spacecraft automatically turned 180°, pointed the retropackage forward and its nose 14.5° downward and kept this attitude for the rest of the orbital phase to facilitate communication with the ground.