Apollo Launch Roll Program

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Click11

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Hi All,
I am a new member of this forum, and have joined really to try and find the answer to a question that has been nagging at me for close on 35 years.

Can anybody tell me what the purpose of the roll program, initiatred at approx 12 to 13 seconds after liftoff of any of the saturn launches. It cannot simply be so that the crew can see the horizon once the escape tower had jetisoned because surley they could have just placed the launch vehicle on the pad differently and make the launch sequence simpler by not needing a roll program.

Hope this does not sound too daft a question

Click11 :?
 
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MeteorWayne

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I think this question would be better off in Missions and Launches, so I'll move it there.

I think I used to know the answer, but there's a few folks who worked on the program who know it better, so I'll not speculate.

Welcome to Space.com!

Wayne
 
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brooke86

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A roll program or tilt maneuver is an aerodynamic maneuver that alters the attitude of a vertically-launched space launch vehicle. The maneuver is used to place the spacecraft on a proper heading toward its intended orbit.

A roll program is completed shortly after the vehicle clears the tower. In the case of a crewed mission, a crew member (usually the commander) reports the roll to mission control which is then acknowledged by the capsule communicator.
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trailrider

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Since the direction a launch vehicle flies after liftoff may be different from the orientation of the vehcile relative to the launch pad, it is necessary to turn the vehicle to the proper launch azimuth (the intended direction). It is far easier, and places less aerodynamic loading on the vehicle if it is rolled around its longitudinal (long) axis before starting to pitch over as it climbs out. This is more apparent on the Space Shuttle missions, which fly either 28 degree (to Hubble) or the 54+ (corrections, please) degree orbits required to reach the ISS. The launch pad orientation is fixed on the ground, so the stack rolls to the proper launch azimuth just prior to pitch-over.

Another reason for doing this often has to do with the design of the guidance system's stable platform that gives the vehicle its references in space. It's somewhat complex to explain fully here, but you have to guard against "gimbal lock", and rolling the vehicle to the launch azimuth takes care of that.

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