# Would the space shuttle do a yaw maneuver to avoid the tower?

I read some rockets do a small yaw maneuver of about a degree immediately after T0 to avoid the tower in case of wind gusts.

Would the space shuttle ever do such a maneuver? Did it?

I read also that from T0 through the start of the pitchover maneuver, the attitude indicator will display pitch-yaw-roll in that order relative to an inertial reference frame conveniently located at the launchpad and aligned with the launch azimuth precisely at T0.

Because pitch was the first rotation in the displayed sequence, a yaw maneuver relative to that inertial pad frame would have registered as a combined pitch and yaw rotation sequence and not as a pure yaw rotation. This would have been less than intuitive for the crew, so from this alone I want to say the shuttle never did yaw maneuvers and instead went straight to the roll and pitch rotations.

Does this seem right?

• If anything, the Space Shuttle launch stack always seemed to be doing a slight translational move as it commenced liftoff...never noticed any yaw... Mar 1 at 16:46

No. The commanded Euler angles in the Boost Reference frame1 were: pitch 90 degrees, roll and yaw 0 degrees until

the computed relative velocity of the stack exceeded the value stored in a reconfigurable flight software variable called PPOLY(2). The nominal value of PPOLY(2) was 118.45 ft/sec. This was nominally achieved at ~ T + 8 seconds and and altitude of ~376 feet.

Once that computed relative velocity was exceeded, the Single Axis Rotation a.k.a. Roll Program started.

1The Boost Reference frame is an inertial system frozen in time and space at liftoff and defined as follows:

• The origin is at the launch pad
• The z-axis is directed along the local gravity vector and positive downward.
• The x- and y- axes are contained in the local horizontal plane with positive x directed northward and y completing the right handed triad.

Sources:

• The boost reference frame---was it used in the flight control calculations? Or was it used in the ADI pitch-yaw-roll display calculations? Or both?
– user36480
Feb 1 at 3:06
• Again...don't get hung up on the ADI, that is just for crew reference. The Boost Reference frame is what the pre-programmed yaw/pitch/roll commands for first stage were defined in. Feb 1 at 3:11
• Yes, but I need to know because I'm modeling both flight control and attitude display... Thanks anyway.
– user36480
Feb 1 at 3:26
• Answers, discussions, and references from previous questions should make it abundantly clear what the ADI FORs were. Feb 1 at 3:45
• They did, until your answer here mentioned a frame I didn't know existed, and which brought what I thought I knew about the ADI into question. It wouldn't be the first time I've been wrong.
– user36480
Feb 1 at 4:01