How can I shore up docking port connections?

[JebNeedsHelp]

I'm running a stock .24.2 game, and I just finished testing a two-part proof-of-concept spacecraft for carrying loads of fuel to the Jool system. The problem is that where the two halves were docked together, even with the Clamp-O-Tron Sr., under too much thrust I was afraid the wobble would break the ship apart. I had to baby it all the way to Jool on less than 50% thrust, and that was with nuclear engines. Without that mod that lets Kerbals EVA and add struts, I don't know how to make the docking connection more stable. Any help would be greatly appreciated! Thanks in advance!

Edited October 9, 2014 by JebNeedsHelp

[Claw]

Well, we can make lots of guesses and stabs in the dark, but it would help greatly if you could provide a picture of said craft.

Multidocking is an option, as is changing the configuration of your ship. Puller designs can be more rugged than pusher, but doesn't guarantee that it'll work. Sometimes just stiffening up the payload works. Or try switching where your controlling the ship from. It kind of depends on the ship.

Cheers,

~Claw

[JebNeedsHelp]

Fair enough. I should have included these. Basically, I took two copies of the same Tylo probe and transfer vehicle, attached a docking port at the top, linked them up, and headed out - the goal being an actual Tylo landing that didn't lithobrake (this time I ran out of fuel just above the surface - the probe took a hard bounce and tipped over but survived without a few engines).

Each half is a probe lander, and two big tanks with four nuclear engines each. The two tanks at the far end are the last of that half's orbital stage.

The worst wobbling was when both halves had the nuclear engines and their two big tanks of fuel. When I used one up, it got better, but not that good.

[Laie]

The core of the problem is that even the largest docking port isn't stable enough for a vessel of your size. Under KSP shipbuilding rules, the only thing that helps will be more connections. It needen't be many and they don't have to be very strong in order to take up the wobble. They need to be there, that's all. One tiny docking port on top of every structural panel would do -- which leaves you with the problem of making them *all* come together. I couldn't do it without some kind of alignment indicator mod.

The alternative is to tie them together with struts and launch them as one piece.

That's all the stock ways I can think of, really. There's a mod that allows your crew to place struts while on EVA (KAS), and then there's the "Quantum Struts" mod.

[Axelord FTW]

I've never done it myself but can't you dock multiple parallel (and side by side) docking ports together? I use KAS and even with a lot of struts and some Sr. docking ports I still got some wobbly wobble.

Edited October 9, 2014 by Axelord FTW
Hit submit by accident

[cheeseit]

I used the largest docking port with a very very similar set up and it worked okay.

If I hit full throttle it would wobble around but if I slowly ramped up the speed it would be fine. I only had 2 Nuclear engine though.

[Laie]

If I hit full throttle it would wobble around but if I slowly ramped up the speed it would be fine. I only had 2 Nuclear engine though.

Good point, I totally forgot about that. Deactivating gimbals may also help, and "control from" a suitable part.

[Pecan]

Won't fix the wobble but: lose the huge, heavy, monopropellant tanks and replace the Mk 55 radials. As it is you have enough monopropellant for a couple of complete space programs and the worst engines in the game. If you're not confident of your docking you'll still have plenty with a couple of cylindrical tanks. Just about any cluster of engines will outperform the Mk 55s.

[Alshain]

That seems like a lot of space craft for Tylo.

[Taki117]

Also, a puller design is inherently more stable than your current pusher design. Place your engines above the CoM and disable gimbals and you should be fine.

[JebNeedsHelp]

As it is you have enough monopropellant for a couple of complete space programs...

I've heard this quote before. Maybe I just used too much RCS swinging this monster around (I get impatient waiting too long for the thing to rotate), but I ran out of RCS fuel long before I wanted to.

I agree it's a lot of ship. Rather than design a new vessel, I was jerry-rigging my newest Tylo lander attempt. I should point out that I have never yet soft-landed on Tylo, as even with F9 reloads, this lander runs out of fuel just above the surface. I was hoping to use one lander for most of the descent and actually land with the other - it still didn't quite work.

Thanks for the tips. Tylo's the only landing that still kicks my butt. Hopefully my next attempt will finally be the one.

[Superfluous J]

Also, a puller design is inherently more stable than your current pusher design. Place your engines above the CoM and disable gimbals and you should be fine.

I agree with a lot on this thread (Especially the lack of need for monopropellant. Turn off the RCS jets when you don't need them and a little fuel can go a LONG way) but this I agree with the most. You can link a LOT of stuff together with the wobbliest of docking ports and if your engines are at the front, it's perfectly fine. With gimbals disabled. That can get crazy quick. As I found out once while trying to land on Moho.