Why do many rockets complete a roll maneuver during takeoff? Rockets are cylindrical, so doesn't that make it unnecessary?

Update:

I understand why the shuttles would do that but the Apollo rockets would also have a roll maneuver in their liftoff sequencing.

8 Answers

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  • D g
    Lv 7
    5 months ago

    NOT all rockets do it but .. most do .. one explanation is that the rockets are set a specific way ... with the capsule window or the payload attached to the rocket a certain way .. that they are shifting the window to a location that is more favorable to orbital position..

    for a payload like a satalite they might want its weight on the lower half of the tip of the rocket since it probably wont be totally balanced..

    the official reason was just to change the attitude of the rocket for proper orbital entry ..

    I thought about the liquid propelant they may be using the spin to get the propelant moving providing some kind of stabalizing effect

  • 6 months ago

    They're stabilised by spinning, like a rifle bullet, because gyroscopes always point in the same direction. This is later reversed by forces acting in the opposite directions.

    • Warren
      Lv 7
      6 months agoReport

      Absolutely not! Nothing you said is true!

  • 6 months ago

    This was specific for the STS, fixed to the side of the external fuel tank. This roll positioned the main engines for its trajectory into orbital insertion. After tank jetison, the 3 main engines were cut and used smaller OMS rockets to fine tune orbit.

    The mighty Saturn V of the Apollo era made no such roll maneuver. 'Aiming' the engines, guided the rocket on a path into orbit so roll was not needed.

    Reentry of Apollo relied on visual alignment with an etched graticule on windows matched to the horizon to 'FLY' the spacecraft through reentry path so roll was crucial.

  • 6 months ago

    Different rockets roll for different reasons... the Shuttle rolled to get on the correct trajectory - as the launch pad only faced one direction, and it needed to roll so many degrees to get the proper orbital angle. The Saturn V rolled for about the same reason, as the moon's angle with respect to the rotation of the Earth changed as we orbited the Sun; it also performed a 'gimbal check' on the guidance machinery.

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  • 6 months ago

    Rockets do not need to do a roll maneuver as you say, they are round. The roll came when we launched stuff either were asymmetrical such as the Space Shuttle so that the weight was under the rocket or when there was people on board so that they would be more or less upright inside the capsule. That would put them in the best position to endure the positive g-force of the rocket going up. With the space shuttle they could not have both so decided the stability of the rocket/shuttle took priority over the position of the crew.

  • 6 months ago

    there is a benefit to having in an internal rotation when it comes to maintaining path direction, which is why we have rifled barrels for guns. Gives an angular motion that is hard to disrupt. Keeps the center of mass on a line; prevents accidental lateral (off axis) movement. I don't think they do that with rockets though, at least not at launch. The force of acceleration is enough. Once they stop pushing, though, a minor rotation is generally preferred.

  • 6 months ago

    the only one I know of that executed a roll is the space shuttle, and it was far from cylindrical.

    wikipedia:

    Shortly after liftoff, the Shuttle's main engines were throttled up to 104.5% and the vehicle began a combined roll, pitch and yaw maneuver that placed it onto the correct heading (azimuth) for the planned orbital inclination and in a heads down attitude with wings level. The Shuttle flew upside down during the ascent phase. This orientation allowed a trim angle of attack that was favorable for aerodynamic loads during the region of high dynamic pressure, resulting in a net positive load factor, as well as providing the flight crew with a view of the horizon as a visual reference.

  • 6 months ago

    It looks cool for the people watching

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