6

Gimbaling the engines off the line intersecting the center of mass produces torque, which yields a rotation rate; if the vehicle is stable then a very small deflection should eventually bring you to the desired pitch angle. The basic logic is an automatic control loop using something like a PID controller, usually with several additional constraints -- like ...


6

That section of the Wikipedia article is very poorly written, conflating interplanetary gravity assist in one case with gravity turns (prior to my ruthless edit), and should be in no way considered comprehensive, nor as a serious indication that gravity turns weren't used prior to Apollo. The early crewed missions (Vostok and Mercury) were flown on ...


5

Any rocket bound for Earth orbit will use some kind of gravity turn; orbit requires a lot of horizontal speed. Interplanetary missions (almost?) always enter parking orbit around Earth before leaving for their destination (this allows them much more flexibility in launch timing). Thus they will use gravity turns. I think you’re slightly misunderstanding ...


5

Here are some shuttle ascent guidance basics so you can interpret my answer. During first stage, the shuttle flew a predesigned (therefore open-loop) pitch-yaw-roll profile based, among other things, on the measured winds of the day. (Note that only the attitude targets were open-loop. The shuttle used a closed-loop control system to fly to those targets.) ...


4

Ares I would have flown very close to an ideal gravity turn in the atmosphere. One paper that covers the simplest guidance of pitching it over on an initial azimuth and then flying it with basically zero AoA up until SRB separation is here: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080048217.pdf There's another paper here where it finds you ...


4

The optimal trajectory for reaching the cheapest ("altitude zero" circular) orbit around a perfectly spherical, airless body involves turning immediately after lift-off so that the vertical component of thrust only offsets gravity drag (weight minus centrifugal force) providing no vertical acceleration, and all the remainder of thrust goes towards horizontal ...


2

A gravity turn is the most optimal path to orbit, assuming no atmosphere or staging. On Earth, launch vehicles use a modified flight path accounting for those differences, generally resulting in a more vertical trajectory than would be the case otherwise


2

Sometimes you just can't get @RussellBorogove to admit that those really helpful comments can become a really a good answer. So until that time comes... I'll temporarily accept this copy/paste answer. From here: Any stretch of time during atmospheric ascent where the rocket isn't vertical and its AoA is near zero is gravity turn by definition. and from ...


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