Before the IU was held to the launch azimuth by the theodolite, it was free, so if you could stand by the launch pad and watch a Saturn V for a full day, you would see the Instrument Unit appear to make a full turn when, really, it was the rest of the rocket turning with the Earth. At T-minus 17 seconds — 17 seconds before launch — the guidance platform was released from the theodolite. About one second after launch, the Saturn V made its first flight manoeuvre.
The yaw program was the disconcerting-looking tilt of the rocket away from the launch tower, a move designed to protect it from any swing arms that failed to move away or a strong gust of wind. About 12 seconds after launch came the second manoeuvre, the roll program.
This had the rocket roll to align itself with the launch azimuth as prescribed by the guidance computer, which was usually at a bearing of 72 degrees. The next manoeuvre was the relatively simple pitch program. The rocket slowly took on a horizontal flight path that, combined with the roll, would put the Apollo spacecraft in the perfect spot for its trip to the Moon. A roll is a pretty standard manoeuvre for a rocket, and the exact roll depends on the desired orbit of the payload.
The shuttle was also aligned on the pad with its pitch axis pointing north-south rather than east-west, necessitating a far larger roll than the Saturn V. Reusing Apollo facilities, the shuttle sat on the launch pad the same as the Saturn V, with its pitch axis running east to west. From there, the shuttle rolled for the same reason as the Saturn V, the align itself to the flight azimuth for its specific orbit.
Sources: Thank you to David Woods who talked me through the awkward of getting my head around the Saturn V roll program! And also for catching a couple of awkward phrases and typos post-publication. Create a free Team What is Teams? Learn more. Why did the Space Shuttles perform a rollover maneuver during launch? Ask Question. Asked 6 years, 1 month ago. Active 4 years, 8 months ago. Viewed 4k times. Improve this question. Add a comment.
Active Oldest Votes. You state I would think better to do it earlier after launch while the air flow pressure is low. Improve this answer. Organic Marble Organic Marble k 8 8 gold badges silver badges bronze badges.
JohnP JohnP 1, 9 9 silver badges 8 8 bronze badges. I saw this mentioned on an Aviation. Can anyone point me to the source? Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. The Complete Star Atlas. First, a shuttle must launch to achieve the desired orbit orientation. Because the launch pad can't pivot to the needed angle before liftoff, a shuttle must rotate after launch to adjust.
Then the vehicle, which initially moves slightly faster than ISS because it starts off in a lower orbit, can "catch up" to the station and dock with it.
Second, about a minute after liftoff, all atmospheric forces on the vehicle reach their peaks. Rotating a shuttle right after launch puts the vehicle into a position that helps reduce stress on the orbiter, especially on the wings and tail. Finally, the roll maneuver enables a shuttle's pilot to see the horizon.
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