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Rockets tip over while i initiate gravity turn


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So basically whenever i launch a rocket, E.G a rocket to haul a space station up into orbit, it tips over. After the roll, i initiate the pitch, but then quickly loose control and my space ship literally tips over facing the ground. I tried MechJeb, Manual flight, but nothing works. Any help would be much appreciated.

Edited by SnakeNation
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It's because your rocket is aerodynamically unstable, so it wants to point backwards.

Your next question is "well, what's wrong with my rocket, and what do I need to change so it doesn't do that?"  :)

That's hard to answer without seeing a screenshot.  If you post a screenshot, we can give more specific advice.

However, general rule of thumb:

  • Heavy and pointy stuff goes in the front
  • Light and draggy goes in the back

Make sure your CoM is as high towards the front of the rocket as possible, and stick fins on the back to help stabilize it.

Beyond that... screenshot please?

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how are you doing your gravity turn? if you're going to 10km or so and turning 45 degrees, then there's pretty much nothing you can do to stop it from flipping over. you have to do a real gravity turn in order to not flip over. wait until you get up to about 100 m/s or so, then just barely pitch your rocket towards the horizon in the heading you want to go (5 or so degrees should be enough). then maintain prograde as closely as possible and keep slowly pitching down (but make sure to not stray too much off the prograde vector or you'll make your ascent less efficient and you'll risk flipping over) so you're at about 50-40 degrees or so above the horizon at ~10km and you should be only a few degrees over the horizon by the time your apoapsis gets to your target altitude.

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what altitude do you start it at?  what is your speed at that time?  how much are you turning over?

 

also i recomend you turn your rocket in the vab to avoid the roll, makes things simpler and less to go wrong.

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1 hour ago, SnakeNation said:

So basically whenever i launch a rocket, E.G a rocket to haul a space station up into orbit, it tips over. After the roll, i initiate the pitch, but then quickly loose control and my space ship literally tips over facing the ground. I tried MechJeb, Manual flight, but nothing works. Any help would be much appreciated.

If you can't fly it and MJ can't fly it you probably want to start with something a bit smaller than a space station in one go.

Possibly teaching you to suck eggs but it's your first post so I don't know what experience you have: first get something into space, then into orbit.  Once you can reliably orbit you can start to get ambitious - and go back to smaller stuff when it doesn't work, which it won't, until you get the hang of design my practicing lots and lots of stuff.

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The advanced answers are already given above: move the CoM around, improve the gravity turn. But the really easy and basic solution is to just stick giant fins on the back of that rocket. If it still flips, make them bigger.

Obviously, if you manage to somehow make the rocket behave itself without the need for extra fins, that would improve the efficiency, as fins in the end are nothing but a source of extra drag.

But post pictures. Imgur is really easy to use, and with some pics you get far more feedback!

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Use long rockets if your fairing is wide, this give an long arm between the front an the fins. 
If you launch something very bulky with lots of drag you might want to do an slower and higher than normal gravity turn, say mechjeb turn shape 60. 
 

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Good big fins (delta wing, tail fin etc), and reasonable TWR (at least 1.5). Some alierons on them won't hurt.

For fins to work, your speed must exceed some 50-100m/s. Otherwise aerodynamics is nonexistent. That's why you need good TWR - with poor TWR and low speed your rocket is a pencil standing upright on your fingertip. With good air flow going (speed!) the fins will be stabilizing it.

Depending on TWR the point where you initiate the gravity turn and its depth changes. With huge TWR you may want to start immediately and dip pretty deep, as the fins will make the dip due to gravity turn very shallow once aero kicks in. With heavy payloads and underpowered engines... no, you don't start the gravity turn later. You add moar boosters.

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