# Crash Course - Gravity Turns & Orbits

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First up, here's how to gravity turn in under 60 seconds!

Later this will I'll upload the full video. Hope it helps!

Edited by cvusmo

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Yes, you can make ridiculous rockets and use the same principles in the crash course to do a gravity turn.

All you're doing with a larger rocket is adding mass. It's the only variable you're really changing.

Here's proof of a ridiculous rocket:

32 SRBs + 15 main engines

Edited by cvusmo
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• 1 month later...

You actually are very very late on your Gravity Turn in those videos, you can turn much sooner.

GT PitchOver is mostly function of your LiftOff TWR. Here is a comprehensive analysis I've ran with a friend, based on hundreds (and hundreds) of empirical automated kOS launches :

Each color corresponds to a given angle amplitude, calculated from the horizon. The abscissas show the TWR, and the ordinates correspond to the values of VpitchOpti. In other words, reading this graph allows you, for any launcher, and from its TWR at takeoff, to deduce a good estimate of the VpitchOpti leading to an optimal GT. For each TWR on the x-axis, we have several pairs of (Amp ; VpitchOpti). The couple of values with the lowest Vpitch will very generally be the best, but the results remain essentially the same. It will remain easier for a "hand" use to trigger a GT at 16m/s rather than at 8m/s for example, in terms of reaction time and speed of execution.

Let's take an example! The TWR 1.4 offers us 5 curves, so 5 couples of possible values, here they are

85° ; 22 m/s
80° ; 36 m/s
75° ; 50 m/s
70° ; 62 m/s
65° ; 78 m/s

Overall, all these combinations should lead you to a very aggressive and optimal GT. The combination with the lowest PitchOver amplitude value, here 85° (5° amplitude from vertical), allows the most natural and efficient trajectory. The launcher realizes a small 5° offset, very soon after the launch, from 22m/s, then remains in prograde until reaching the Apoapsis of 100km, and finally circularizes.

Nevertheless, be careful: this is an ideal target value for our precise craft. It is therefore a very good starting estimate, but could be slightly out of limit for any other craft of the same TWR. As a precaution and if you are not the kind of person who would restart a craft several times to find its perfect torque (Amp; VpitchOpti), don't hesitate to simply take a little margin, by adding 5m/s for example!

These curves can be used by users who do not have a kOS and simply do their launches by hand. However, there is an important consideration to be made: the reactivity of a program is certainly much greater than that of a human, but the angle shift command will be slower for kOS than for you, because the program remains dependent on the servoing of KSP, which does not send a binary "turn" command to the keyboard.

You can find the whole article right here, use the translation button in the upper right corner : https://kerbalspacechallenge.fr/2021/07/22/optigt-a-la-recherche-du-gravity-turn-parfait-partie-1/

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• 10 months later...

Thanks for your post @Dakitess . The contents seem very interesting but unfortunately the links do not work anymore. Can you update those ?

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Thanks for your post @Dakitess . The contents seem very interesting but unfortunately the links do not work anymore. Can you update those ?

Unfortunately, yeah, the team is moving from a website to another one and it's manual, so not all the article has been transferred so far and I can't reach the original article as I am no longer part of the team. Sorry, I'll reach you when it's back

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Hoooo so cool, the guy who wrote the whole program of OptiGT just released an English Video to showcase its use !! It's not the article and I've not seen it entirely but I can already bet that you'll be amazed

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