Assembling ships in space?

[DaymareDev]

I tried building a ship in parts; main ship, with symmetrically aligned engine attachment ports using docking ports, and each docking port having a small nuclear engine + more fuel attached to it. I can't seem to be able to steer the ship properly, and it lists to one side. Any ideas why that might be? Is it even possible to assemble ships in space this way in stock?

Picture of prototype below, The twin set of engines at the top are the ones misbehaving.

[Red Iron Crown]

I would check the following:

- You're "controlling from" the capsule in the nose of the ship.

- Your ship is truly symmetrical (in your pic one of your nuclear modules is attached in a different orientation than the other two).

- Your nuclear modules aren't wobbling too much. If they are, try disabling the gimbals on them.

- Can having SAS on control the unwanted attitude change?

- Tanks are filled and drain symmetrically. If tanks on one side drain faster than the other, you're gonna have a bad time.

Hope this helps.

[adinfinitum]

Like Red Iron Crown said, it might be because the engines are rotated in different directions, so the docking ports cause the center of mass to be lined up very slightly off center.

If the engines were directly attached to the ship, I wouldn't think this would cause much of a list. Since they're attached by docking ports, things get a lot more bendy and springy, and the different orientations of the engines might cause them to bend in slightly different directions that each other.

Also, I'm curious, is there a particular reason why the RCS blocks on the engine modules are in what looks to be six-way symmetry?

[Vanamonde]

It is possible to assemble and fly much larger structures than that.

But they are extremely sensitive to imbalances of mass. One thing that helps is to apply thrust in small increments rather than all at once, to give the SAS time to adjust. But more importantly, do all of the fuel tanks on your ship which are not on the centerline have equal amounts of fuel in them? If not, you can right-click on two tanks to transfer fuel between them in flight.

[Kerba Fett]

Actually you right click on one tank then hold ALT while you right click on the other to bring up the transfer menu.

[CaptainKipard]

Get RCS Build Aid.

Click the "Engine" button.

Assemble the whole thing in the VAB as you want it to look in space. RCS Build Aid will help you balance the ship.

Break the ship up into launchable parts.

Launch and assemble in space.

[DaymareDev]

Like Red Iron Crown said, it might be because the engines are rotated in different directions, so the docking ports cause the center of mass to be lined up very slightly off center.

If the engines were directly attached to the ship, I wouldn't think this would cause much of a list. Since they're attached by docking ports, things get a lot more bendy and springy, and the different orientations of the engines might cause them to bend in slightly different directions that each other.

Also, I'm curious, is there a particular reason why the RCS blocks on the engine modules are in what looks to be six-way symmetry?

each rocket module is able to dock itself with the ship

[Dust]

With all those docking ports, especially the medium-sized ones just in front of the thrusters, I suspect the craft is wobbling back and forth. In Scott Manley's Interstellar Quest series he addressed this on his Duna ship by putting the thrusters at the front, thereby pulling the ship rather than pushing.

[Kasuha]

Potential reasons:

- initial imbalance, may be caused e.g. by fuel in fuel tanks not distributed proportionally around the ship

- throttle control on individual engines, it is possible to set up throttle limiter on each engine separately and under certain circumstances it may happen involuntarily during the ship construction

- secondary imbalance, caused by uneven draw of fuel from fuel tanks. That may be in turn caused by the way how you docked your engines, especially if you docked them in groups, i.e. more docking ports at once. Because when docking more ports at once, only one of them then allows fuel transfer.

If nothing of the above applies, maybe you could share your persistence file. If the ship is stock, I can take a look at it.

[m4rt14n]

Dock with MJ. Click on Force Roll

[Wooks]

Dock with MJ. Click on Force Roll

Don´t do this unless you want to never know what happened to your ship.

[m4rt14n]

Don´t do this unless you want to never know what happened to your ship.

Care to elaborate? Good sir.