the_fungible_man t1_j21wgcw wrote
>Why wasn’t the module adjusted on the launch pad so this wasn’t necessary?
Several reasons.
The launch pad/tower infrastructure (elevators, hold down clamps, umbilicals) are designed to mate with the launch vehicle in a specific orientation. But even if you could rotate the whole kit and caboodle, it wouldn't help:
For launches with non-instantaneous launch windows, such as the Apollo missions, the trajectory the vehicle will take once it clears the launch tower varies depending on when liftoff actually occurs. Therefore, there is no pad orientation which would eliminate the need for the roll maneuver in every case.
gagaron_pew t1_j21yd69 wrote
it is possible to "rotate the whole kit". i think the russians are still doing it, or at least were doing it that way.
Barrrrrrnd t1_j21zyau wrote
Possible but not worth the cost in retrofit when they can just roll the vehicle.
the_fungible_man t1_j222q69 wrote
Interesting. It appears that rotation of Soyuz launch vehicles was necessary until the Soyuz 2.a which first launched in 2004.
bigboilerdawg t1_j22m6nt wrote
So the roll angle varies depending on the time of the launch? I never knew that.
the_fungible_man t1_j22o51w wrote
It's the flight azimuth that changes as the Earth rotates during the launch window. The rocket rolls to align itself to its flight azimuth so its flight path then becomes a simple pitch program.
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