Rocket is unstable.

[shadowpho]

I made a rocket to go to the moon [AND BACK!].

Here's my calculation:

Stage 0 - Parachute for earth + RCS for use in space.

Stage 1 - decoupler for cockpit

Stage 2 - Gear Down for moon landing. Also contains wings for stabiliziation

Stage 3 - Motor to slow down for moon entry. Small tank.

Stage 4 - 3 nuclear engines for space prowls.

Stage 5 - 3 liquid engines, 6 medium tanks for them.

Stage 6 - 6 small boosters to get to moon.

Stage 7 - 3 medium liquid engines, 12 tanks to get out of earth.

Stage 8 - 6 large boosters.

Stage 9 - 3 huge liquid engines. [only runs at 80% speed top]

Stage 10 - 12 large boosters.

Now, most of the stages work PERFECTLY. However, at stage 8 I can't control it :/.

Stage 10 - gets me to 2 km, 134 m/s

Stage 9 - gets me to 16km, 330 m/s

Stage 8 - starts looping and looping :/.

Stage 7- Goes in weird directions.

[sal_vager]

Post the pic and the craft file here shadowpho so people can test it out, it'd make helping you a lot easier

[EndlessWaves]

Yeah, without knowing how they're positioned or how the different parts of the rocket are behaving we could only guess.

As a quick fix try putting a ring of struts around the part of the boosters furthers from their attachment.

[shadowpho]

This is complete rocket:

Stage 9:

[UBERDOMINATOR]

I can't see super well, but if I had to guess for a quick fix, I would say to move/add some canards to the area around the stage that flops on you. There is still a bit of atmosphere when you hit that stage, and with the length of the rocket, may make the top end drop. Also, I see that you are using struts, but I have no idea where they are. I would personally strut some of the upper and lower stages together as I imagine they are buckling a little. I could be totally wrong though, still haven't worked out all the kinks I run into.

[sjwt]

Looks like you need Struts taking the upwards force on that thing for that stage wtih the boosters..

Run struts from the top of each of the boosters to the top of the rocket, that shoudl give you more stablity.

Good luck

[bsalis]

That seems a large and complicated rocket for a Mun return mission.

Anyhows... my 2c is this. Put struts between stages for support. It's ok to do that, the struts do not hold decoupled stages together. Other than that...as mentioned earlier, the canards can probably go. Also, ... oh wait.. you said you lost control at stage 8?

Stage 8 - 6 large boosters.

Dude. They don't gimbal. On a craft that size, always have some gimbaling liquid engines to steer.

[sjwt]

That seems a large and complicated rocket for a Mun return mission.

They don't gimbal. On a craft that size, always have some gimbaling liquid engines to steer.

Gimbal equiped controlled rocket? That's not Kerbal!

Large and complicated rocket taking 5 times the needed fuel and it can not be controlled? Now that's Kerbal

[EndlessWaves]

The rocket is dead straight in both images so I guess the top isn't wobbling and vertical struts aren't needed.

It's a little hard to tell with the JPEG artifacts but it looks like the struts on your solid fuel boosters are placed radially inwards which is about the least useful direction - even if the rocket nozzles do swing outwards you only lose some efficiency (and it may make the rocket more stable). Try placing them in a ring around the the top or bottom of the boosters (or both) and see if that makes it any less prone to tipping.

[ElJugador]

.. whoa. You're using waayyyy too many stages. The vast majority of them are dead weight. Try getting rid of the three nuke engines, the radial booster'd 3x liquid stage and everything in between.

[Nibb31]

Too big and too heavy. You are using way too much fuel just to lift fuel that you need to lift more fuel.

You really shouldn't need more that 4 stages to get to the Mun. Design your rocket top-down: A return stage, a lander stage, a LOI and deorbit stage, and 2 or 3 stages to launch that into Kerbin orbit.

Also, it is usually more efficient to design your rocket with radial stages, especially if you use fuel lines so that the outer tanks fuel the central core as well as their own engines. Any engine that isn't firing is dead weight.

[Markus Reese]

well, I see lack of struts. Cross connect lower to upper with them.

[EndlessWaves]

You really shouldn't need more that 4 stages to get to the Mun. Design your rocket top-down: A return stage, a lander stage, a LOI and deorbit stage, and 2 or 3 stages to launch that into Kerbin orbit.

That comes to 6-7 stages, which is about what he's actually using.

It is a much heavier rocket than the minimum needed to go to the moon but there's nothing wrong with getting more DeltaV or a higher thrust to weight ratio into space as it'll make corrections easier. It is worth pointing out that if you get fed up with trying to make it work that a munshot is possible with a smaller machine though.

[Markus Reese]

Reading more, you said stage 8 is when it spins out. That is the 6 large srbs. That only firing plus limited gymbal control means once you hit atmo, it is entirely up to any SAS/thrust to keep it stable. Any wobble will offset the COG and spin out of control it will. If you fit the SAS onto the launch stage, my recommendation is in with the last orbiter part, it should stabilize it muchly when the ASAS is going.

[Tauge]

Pare that bad boy down. You're lifting far more mass than needed. You don't need that much. You can get to the moon rather easily if you just don't go crazy.

[sjwt]

No! Don't slim it down!! Keep them at a size you are comfortable with, and slowly over time you will work out how to slim them! If you still cant get it working, post the file and I will try to fix it for you =>

Play KSP your way or the highway <G>

[Luke321]

I know that problem from one of my designs, try using mechjebs ascend auto pilot and press e or q while ascending.

the rolling stabilizes the craft altough i dont know why...

my rocket has 18 Mainsail engines and is perfectly stable when using this method, and not controllable at all when used without mechjeb.

[Steelfury]

From those pics it looks like your solid fuel boosters are wobbling all over the place, try sticking one or two struts on them attached to the body of the rocket

[shadowpho]

Thank you guys! Lots of fantastic advice here, I am playing with all of that . I made 2 big designs off your help, and I got 1 to minmus, and 1 to moon! w00t!