![]() ![]() As a final note, all rockets will have their TWR go up as the launch progresses due to shedding weight by burning fuel. If you find your TWR at launch is too high, either use a smaller engine or just throttle down, and vice versa. Smaller and lighter rockets handle higher TWR's better than big and heavy ones and each craft will have its own sweet spot you are encouraged to experiment. For these reasons, in my experience, a TWR of ~1.5 is a good sweet spot between efficiency and controllability of the rocket. A higher TWR also causes increased stress to the craft, inducing wobble and risking a RUD, especially when trying to maneuver. This reduces overall efficiency and defeats the purpose of having a higher TWR to begin with. What usually ends up happening is that you have to force the gravity turn manually, which does generate significant drag (because you expose the sides of your rocket to the airstream anytime you deviate from your prograde vector), and causes steering losses ( Dv wasted on changing direction rather than gaining velocity). ![]() The drawback is it makes your rocket less forgiving in terms of control during ascent, and it shortnes your widnow to make a pitch-over maneuver. ![]() Thus, a slightly higher TWR of around ~2.0 in theory is more efficient, but only if the launch profile is flown correctly. Keep in mind that drag losses are almost negligible in the new aero, unless your rocket is shaped like a brick or you are going extremely fast in the lower atmosphere. A higher TWR at the beginning of the launch makes it harder for your rocket to turn naturally, as gravity will have less influence on its trajectory, making it fly straight and screwing up your gravity turn. TWR: Your thrust-to-weight ratio ( TWR) at launch should be relatively low, around 1.5. It is important to keep this in mind.īefore even launching, you need to take these design items into consideration when building your rocket: T he best way is to do a real gravity turn that is, a turn caused by gravity and aerodynamic forces, rather than one achieved by actively turning the rocket. We want to launch in a way that we gradually turn sideways while we ascend. To do this, we could launch straight up until we're out of the atmosphere, then point sideways and accelerate to orbital speed. You all probably know by this point that to get into orbit you need to go up, above the atmosphere, but you also need to go sideways (i.e. When your Ap reaches the desired altitude, cut your engines, coast to Ap and circularize. Start pitching down manually towards the horizon and adjust throttle to keep your Ap around 45 seconds in front of you.Ħ. When your altitude reaches ~40 km, turn SAS ON. Avoid control inputs and use only throttle to control your gravity turn (throttle up to turn slower, throttle down to turn faster).ĥ. ![]() the control input arrows on the bottom left are all centered), turn it OFF. When your speed reaches 50 m/s, perform a pitch over maneuver (tip towards the East until pointing between 5° to 10°).Ĥ. TL DR (courtesy of Turn ON SAS and set throttle to give TWR of ~1.5.ģ. For that, you'll need to go through the entire post, but I'm also including a TLDR as a "cheat sheet": More than giving a script or set of instructions, my goal with this tutorial is for you to gain an understanding of the factors that affect your rocket's behavior during launch, so that you can apply it to any rocket you fly. This tutorial works for versions 1.0 to 1.3. This is an in-depth tutorial, but still directed to beginner-intermediate players, on how to do a proper launch and gravity turn with the new aerodynamic model introduced as of version 1.0. ![]()
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