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[TheProphet]

Hi I'm a new player and I need help, I'm currently constructing a large space station, I have the core part in orbit and I'm trying to lift a solar array up to orbit. I've got a lifter which uses 1 orange tank with mainsail booster, 6 of the same surrounding it in an asparagus formation, with the biggest SRBs attached on the outside. It accelerates nicely up to 10,000 ish when I drop the SRBs and then it slowly starts to roll over in random directions and flips out of control. I don't understand why. Please help or can anyone help me with a more reliable lifter 

 

[Reactordrone]

It sounds like the drag of the front end gets larger than the drag at the back end when the boosters are separated making it want to fly backwards. You may need to add more fins at the bottom of your core booster to restore natural stability.

Edited April 5, 2016 by Reactordrone

[FullMetalMachinist]

44 minutes ago, TheProphet said:

I've got a lifter which uses 1 orange tank with mainsail booster, 6 of the same surrounding it in an asparagus formation, with the biggest SRBs attached on the outside.

It sounds like you ship is short and wide (a "pancake", if you will). This used to work fine, but not so much any more. 

In general, rockets in KSP fly best if they're made like real life rockets, skinny and tall with heavy at the front, light at the back, possibly with some fins towards the back. 

To give you specific advise, it would really help to see the ship in question. Any chance you could post a screenshot? Also, this:

44 minutes ago, TheProphet said:

It accelerates nicely up to 10,000 ish when I drop the SRBs and then it slowly starts to roll over in random directions and flips out of control.

sounds like you might be doing the old style "go straight up to 10km then turn right" maneuver. If that's not the case good, but if it is, that's bad and wrong. Instead, start turning early, and keep a slow, gradual turn all the way up. 

[Harry Rhodan]

9 hours ago, TheProphet said:

I'm trying to lift a solar array up to orbit. I've got a lifter which uses 1 orange tank with mainsail booster, 6 of the same surrounding it in an asparagus formation, with the biggest SRBs attached on the outside. It accelerates nicely up to 10,000 ish when I drop the SRBs

You keep your center of mass to low by having all your stages arranged horizontally and you use a lot of extremely powerful engines to lift next to nothing which will make you too fast too soon. Probably balancing an extremely long and light payload on the top isn't helping either.

The usual approach to making your craft aerodynamically more stable is to either keep your center of mass up by having a heavy upper stage that you your first stage will carry to around 20-30km or by adding more surface area on the bottom of your rocket in the form of fins or by doing both. I'd always advise against asparagus staging for beginners because like in this case it usually makes everything just unstable. If your payload isn't too light and long a simple solution with two liquid stages on top of each other will get you reliably to LKO. Use SRBs only to support a first stage that carries too much fuel to clear the pad on its own.

Edited April 6, 2016 by Harry Rhodan

[Wemb]

That's a _lot_ of fuel and engines you're taking up - what sort of solar array are you building?  I put a pretty bigone up (A docking port with attached pylon holding, I think, 6 or 8 gigantor arrays + batteries) last year, and did it by sandwiching it in-between two heavy lift stages, rather than having the payload at the top - it was fiddly to build (the symmetry) but flew fine and worked well to limit the scale of CoM changes that took place during the launch phase.  

It looked gorgeous with two of them attached to my station, but was complete overkill - really didn't need that much power at all.

Wemb

[N_Danger]

Pressing the F12 key while in flight will show the drag and lift forces affecting your craft. The yellow lines coming off the parts show the direction of lift and the red lines coming off the parts show the direction of drag(the longer the line the bigger the force).

If the red lines are sticking out from the body you have a greater chance of the rocket flipping around the current CG in the direction of the red line. You counteract this by SAS, Fins. engine gimbal or designing the rocket differently(which is what Harry suggests, moving the CG as high up as possible).