New Kerbonaut with spin issues at 10-20k

[Romanofski]

Hello!

I am new at Kerbal Space Program and have run into an issue.

I've managed to get a few rockets into orbit and thought my next step would be to get a shuttle to mun.

So i've made a fairly large shuttle although I don't think it's insanly big which i've attached to a large central rocket which in turn have 3 support rockets attached (everything is liquid)

And it works pretty good, until I reach between 10k and 20k altitude that's when it just decides to tip over and start spinning.

I go with SAS throughout the lanch as I cannot stabilize it manually, although I can make the ship go somewhat in the direction of kerbins rotation by temporarily turning off the SAS and get a general direction.

I've tried various things to counter this but it keeps happnening.

I've tried attaching wings with controllers. Various amount of RCS. Dropping rockets as I approach the "line", slowing the thrust. It keeps happening and I can't find the cause of it.

Any help or suggestions would be greatly appreciated from more veteran Kerbonauts!

[sal_vager]

Hi Romanofsky, welcome to the community

It would be a great help to us if you could upload your .craft (and a pic would be nice as well) so other members can try your rocket and look for the problem for you, I personally find however that if my space shuttles have wings that are allowed to generate lift during the ascent, those wings are often the cause of unwanted "tippy overy-ness" so what I like to do is make sure my shuttles wings are side on to the airflow, so cannot generate any lift.

Picture the Space Shuttle taking off sideways and you will know what I mean.

Also, to attach pics, I recommend you use Imgur, and use Mediafire for the .craft file, then post the links here

[spikeyhat09]

You say its a shuttle, which implies its half plane, half spaceship. if you're using things like tailfins and winglets to stabilize your ship on the way up, they will become less and less effective the higher up you get. when your completely out of the atmosphere, your fins will just be dead weight.

My guess is, your ship is unbalanced. Your fins and such keep it going straight on the way up, but as soon as you hit that point where they're no longer effective, your ship starts careening out of control. sound familiar?

To fix this, I would redesign your shuttle so it is more or less symmetrical weight-wise, and balanced.

Then again, I'm no expert

[SLAMS]

Also keep in mind tanks change weight depending on fuel remaining. So to avoid this mount the shuttle on the top/front(if you havent already) rather than the side of the lift rocket like "the" shuttle.

[nhnifong]

I'm guessing your ship is pretty tall. Connect 6-symmetric struts from a wide point near the middle to the highest point on the craft you can. this will help keep it rigid. It's OK if the struts connect parts from separate stages. they will automatically disconnect. Try putting 4-symmetric canards at the highest possible point. They will be dead weight for the rest of the mission, but they work wonders for stabilizing tall rockets. Also, whenever you have stages connected to the sides, go ahead and use struts to connect the side stages to eachother at the top and bottom, and connect them to the main rocket at at least one place. SAS will be most effective in the middle of the rocket. Try using two or three SAS modules.

[Tigga]

It's hard to say too much without seeing your ship, but as a rule if it isn't pretty close to symmetrical you're going to struggle out of the atmosphere unless you've spent a lot of time tweaking it. If your ship is symmetrical try adding stiffening struts as nhnifong suggests. A third alternative is to use gimballed engines which, if you're using ASAS or flying manually, should act to reduce the roll.

Incidentally, I think it'd be a great addition if the were to improve the ASAS module so that it could control engine thrusts individually as well. It'd have to be a lot more gentle then it is with RCS and control surfaces, but it'd really help to sort out craft imbalances. Either that, or we need engines with a much higher directional thrust ability.

[hjalfi]

I had tonnes of trouble with my Behemoth lifter (still trying to live up to its name; so far, 15 tonnes to a 100km orbit, which is pants) with this. As soon as you start the gravity roll you begin tumbling, yes?

I believe that it's a combination of lack of control authority and the vehicle weathercocking in the upper atmosphere at high speeds. Once you start turning, the air's coming from the side of the vehicle, the upper tanks are empty and therefore it's tail-heavy, and so the nose gets pushed round so that you're going tail-first. Which never helps. If your vehicle is asymmetrical it'll probably make things even worse.

I think the only solution is more control authority. I did a bunch of experimentation with SAS modules and RCS and control services and I found that what worked for me were winglets, placed as low down as I could manage for maximum leverage. (I tried canards at the top but they were much less effective. *shrug*)