Starting to have problems with my spacecraft?

[Tortoise]

One of the following problems occur during most of my flights:

*Right before I enter space at around 14,000 feet my rocket suddenly dips towards the ground, out of control

*At around 12,000 feet my rocket would do a complete 360 while encountering severe turbulence

*My rocket would fall apart upon stage switching

*I maintain full throttle all the way up without overheating, and suddenly my rocket slows down and starts descending while I am at full throttle facing up/forward

Here are some craft files I'll leave for you guys:

Craft1

Craft 2

Craft 3

Craft 4

Please help me.

Edited June 12, 2013 by Tortoise

[Nao]

The "turbulence" you encounter is probably because of rocket being not stiff enough and wobbling around. Bigger craft's suffer more from this, and need more struts between its parts.

The xLS 60 and 61 have bottom three engines not connected by together by struts, that causes severe wobble and is probably the reason for difficult control (3 strust connecting the lower fuel tanks together in a triangle should fix that).

The xLS 62's wings are placed at the height of center of mass (CoM) (bottom left icon in VAB) therefore they can only help with ship's rotation, and will not give you any additional control over the ship, you can move them closer to the bottom of the ship.

xLS 64 similarly to 60 and 61, lack struts in key places. Try stiffening the center stack, you can strut the bigger gray tank to the four boosters (4 struts). Alternatively you can place struts connecting each fuel tank in the center stage to it's neighbor in a stack (including connections to decouplers and probe body) (1-2 struts per connection here will do the job.

Switching the stacks of the flat gray fuel tanks to one bigger tank will help too.

Also its not feet, its meters. , hope that helps Cheers!

edit: There is one more thing i noticed that might add to strange behavior in flight as well as on the pad (for 60 and 61 crafts). The 1m probe body is kind of bugged, try replacing it and make sure its connected properly (right now the top part is connected to the bottom of it and bottom part is on the top, causing clipping and probably more phantom forces.

Edited June 10, 2013 by Nao

[Tortoise]

Ah ok, i'll see if that works.

Thank Nao.

[Tortoise]

I fixed most of the problems, added struts and moved wings lower, on my xLS-66 but for some reason after the 1st stage I start descending.

Heres the craft:

Download

[Kerbal01]

Your gravity turn is too steep, i try to go for:

10k: 30 degrees

50k:45 degrees

70k 20 degrees

100k 0 degrees

[Rosco P. Coltrane]

Yep, looks like it.

And since we are on the subject. The prograde marker (yellow circle with three lines in the navball), also called the "flight path marker" in airplanes, marks where you are going regardless of where you aim your nose. In this case, it's below the horizon, so rise your nose at least until it's above it. This is also useful for spaceplanes, to keep a level flight just put the FPM/prograde marker over the horizon.

[falofonos]

Double post.

Edited June 10, 2013 by falofonos
Double post.

[falofonos]

For the 3cGX3.craft the radial engines add instability and this rocket can get into a stable 100km orbit without them. I made it with approx 236 fuel in the last booster stage remaining.

a strut on each side of the twin engine / tanks to connect them together will improve stability.

Not entirely sure what this payload is for but the docking port connecting the last stage separator is either not required or it is the wrong way round.

[Tortoise]

For the 3cGX3.craft the radial engines add instability and this rocket can get into a stable 100km orbit without them. I made it with approx 236 fuel in the last booster stage remaining.

a strut on each side of the twin engine / tanks to connect them together will improve stability.

Not entirely sure what this payload is for but the docking port connecting the last stage separator is either not required or it is the wrong way round.

Alright, thank you.

And for the docking port, I just wanna get this peice of ship into orbit so I can launch other rockets and practice docking.

[Tripod27]

I have Ferram's aerospace research mod on and the large amount of drag on the front of my bigger rockets (because we don't have fairings yet) causes them to flip if I start my gravity turn at under 24,000 meters because of the air resistance being too high

If you have the same mod, it could explain the flipping

[Tortoise]

I have no mods, Tripod.

And do any of you have skype?

[Francesco]

Your gravity turn is too steep, i try to go for:

10k: 30 degrees

50k:45 degrees

70k 20 degrees

100k 0 degrees

I would like to know your efficiency with such an ascent profile.

45° at 50km is nonsense, you should already be down to 10°.

[Tripod27]

Well it depends on your thrust to weight ratio Francesco

If your rocket's so heavy that at a 45 degree angle your prograde marker is pointing 10 degrees, then it's be fine

[WhiteWeasel]

A good way that I found to keep you rocket from oscillating/flexing is to strut the joints of fuel tanks and/or use small hardpoints to give your struts more 'space' to reach stuff directly above it. Like this:

Edited June 15, 2013 by WhiteWeasel

[Francesco]

Well it depends on your thrust to weight ratio Francesco

If your rocket's so heavy that at a 45 degree angle your prograde marker is pointing 10 degrees, then it's be fine

right, but if your TWR is so low, you probably need to rethink your rocket and add more thrust.

[Tank Buddy]

When in doubt, add more struts. That's the rule of thumb for KSP. Your unplanned rocket disassembly could also be a result of bad fuel lines. If you do not use the appropriate symmetry, fuel will drain unevenly and the rocket will tip because of the misalignment of the center of mass. I can't help you with the rest, but good luck.