ship spinning on launch

[Cannon]

I haven't been playing since 0.90 and i decided to play again, but now all my ships turn upside down when they reach something like 300 m/s. Why is this happening, i didn't have problems before, i even went to eve and back, what's the problem now?

Also, what's the best way to return to kerbin since heat system has been updated, falling straight, vertically or making periapsis something like 20km and let the air slow you down?

[GoSlash27]

I haven't been playing since 0.90 and i decided to play again, but now all my ships turn upside down when they reach something like 300 m/s. Why is this happening, i didn't have problems before, i even went to eve and back, what's the problem now?

Also, what's the best way to return to kerbin since heat system has been updated, falling straight, vertically or making periapsis something like 20km and let the air slow you down?

Cannon,

The aerodynamics are completely different now. Rockets can flip for a number of reasons, but the common ones are too much drag in the nose, maneuvering too aggressively, and accelerating too rapidly. Rockets behave better when streamlined, and even better with fins in the tail. And of course... don't taunt happy fun rocket.

For reentry, I recommend a periapsis of around 30 km if you have an ablative heat shield and around 45 km if you don't. Falling straight down can easily blow you up.

Best,

-Slashy

[guitarxe]

Pics of your rocket would help identify areas of improvement.

[Cannon]

i can't upload pics because i'm on a vacation and internet is slow here but you can find the craft file of my ship at www.cannon-gaming.site90.com

[Harry Rhodan]

I guess you mean this one. The other is just bigger and has the same structural problems.

Your initial TWR is 3.3. That is way too high and you'll hit Mach 1, the point where aerodynamical forces grow exponentially, extremely early and deep inside the atmosphere. Your whole craft is extremely long and its CoM is comparatively low and probably much lower that the center of pressure. That basically means you have a huge lever that the arodynamic forces can attack quite easily because you have lots and lots of unprotected draggy bits at the top of your rocket. You use next to no struts so those smaller boosters wobble horribly as soon as the physics load and the whole thing starts to drift and wobble in any direction as soon as you launch.

I don't know if there's a good way to save that design. You carry way too much small engines around and that makes your stages somewhat heavy and overpowered. I'd say ditch that twin keel design and build something that resembles a normal rocket (or at least strut them up vigorously). Use less stages with less parts, put enough juice in them and use upper stages that can actually keep the CoM from falling to low. Put draggy stuff like tail fins at the bottom of your rocket and either keep the top of your rocket somewhat clean or use fairings to protect the small stuff from the attacking wind. Your initial TWR should be around 1.5 to 2 (you might want to use one of the information mods like Kerbal Engineer Redux, Mechjeb or VOID) and start to turn slowly when you hit a speed between 50-100m/s and get to 45° at somewhere between 10-15km.

Edit: Ditched the whole first stage and put struts between the next two. Throttled back to around 80% after a few seconds and got it to orbit with at least 5500m/s still in the tanks. A rough ride but still doable. Orienting the craft to the north-south axis at launch might also be agood idea.

Edited July 26, 2015 by Harry Rhodan

[mrclucks]

Your craft looks like its going to land and return from the mun or minmus. My approach would be the second smallest 1.25 m lfo tank with the terrier, with some slightly longer tanks on a decoupler attached to that center tank. Outer tanks should be in 3 or 4 times symmetry, have nose cones at the top, be feeding into the inner tank to take advantage of onion staging, and should have terrier engines which should be a bit lower than the middle terrier so you can use them as stable landing legs.

Using that design should give you plenty of dv to circulize your orbit around the mun or minmus, de orbit and land, take off again and return to kerbin. You could probably use it to make some or all of the burn required to get an encounter with that planetary body, but keep in mind that you'll probably want to keep the outer tanks at least untill you take off and start returning to kerbin.

ascent, stage would either be A. a couple long 1.25 tanks with a 45 or 30 engine and a couple of srbs, or B. an adapter to go from 1.25 to 2.5, big orange tank and a skipper engine.

Regardless of how you build you must remember that you rarely need more than 2 points to connect to make something stable(fuel lines act as struts FYI) and add fins to the bottom of your rocket to help orient you rocket during ascent

Oh and use Kerbal Engineer, its a lifesaver and makes you much more informed

[Kryxal]

First things first, lose those winglets where they are! I think they're placed high enough that initially they're going to angle the wrong way given pitch/yaw inputs. I also don't care for the rockomax decoupler straight to 1.25m, use an adapter and a smaller decoupler. For that matter, you could just turn the first stage into drop tanks, or use the S1 SRBs and vary thrust levels from the mainsails, or even remove them entirely and add another orange tank to the mainsail stage.

[Cannon]

thanks for the responses, i'm still trying to figure out how these new physics work, any help would be apriciated, becuase when i was playing on 0.25 version i was a pro, now i feel like an amateur

[Arkalius]

Well, the biggest tip I can give you is try to design rockets that somewhat resemble real-life rockets. I don't think I've ever seen a monstrosity like that in real life

[GoSlash27]

Cannon,

Aerodynamics are a lot more realistic now. The old kerbal-ish lifter designs wind up being draggy and unstable.

Just design your stuff to resemble RL lifters and you should be fine. Watch the t/w ratio, avoid sharp diameter transitions, and beware draggy parts in the nose.

Also, the old "climb to 10k and hang a right" ascent profile is no good any more. Rockets don't like radical pitch changes now.

Good luck!

-Slashy

[imaspacestation]

On top of what everyone else has already mentioned, the biggest tip I can give you now is to start small again with the new physics.

Make a small craft just for orbiting, and see if you can get it into orbit. Then build on top of that. You have a lot of stuff to re-learn, but don't worry - everyone had to go through that since the move to 1.0+, and it's not that hard. In fact, once you've got the hang of it, you wouldn't know how you had ever managed to build and get those kind of monstrosities to orbit before.