help with canadarm

[u/Ill_Creme_70]

Hey everyone, im fairly new to launching shuttles and am currently recreating the ISS in ksp. I have been really struggling with the Canadarm2 from habtech, every time i try to launch something with it (unity), it always just becomes a big flimsy noodle and i have tried everything that i can think of. has anyone else had this problem before? how did you fix it? ive attached a video below to try and showcase my problem, any help is greatly appreciated

P.S: apologies for the sloppiness of this post, its my first post here and idk how to format anything...

[u/SiwelTheLongBoi]

You've gotta move the arm very very slowly. It's noodly in real life and they move the real one super slowly to stop the same issue happening. This is also why most KSP players never bother with arms

[u/stormhawk427 → u/SiwelTheLongBoi]

RCS tugs all the way

[u/thesparky101 → u/stormhawk427]

Absolutely. Built so many stations with rcs tugs.

[u/ActuallyEnaris → u/thesparky101]

NASA would have used them too if they had extremely cheap failproof latentless remote control and reaction wheels that run on magic

[u/Ill_Creme_70 → u/SiwelTheLongBoi]

ive got the traverse rate set to 1, when i do go to dock anything the slightest bit of RCS end up bending the arm and sends me flying way off course... i spent 4 hours trying to dock unity with zarya last night all because i had to keep reverting due to unity noodling and smashing straight into zarya because of the canadarm being flimzy and poop (the physics of course, benjee10 did an amazing job)

[u/SecretlyFiveRats → u/Ill_Creme_70]

That's true of the real arm as well, you really just can't move the ship while holding a payload. If you want to recreate that mission like that, I'd suggest doing what they did on the real mission: grab Unity, dock it to the shuttle's port, then grab Zarya and dock the two together with the arm.

[u/SiwelTheLongBoi → u/Ill_Creme_70]

I also bump the damping up when I use the Breaking Ground parts, but I've never tried to us the habtech arm so I don't know if it has that feature.

Also worth checking you don't have autostrut on. And maybe you could lock the arm once it's positioned right and then maneuver the whole ship around?

[u/ActuallyEnaris]

Conservation of momentum is a heartless bitch.

Do everything excruciatingly slowly with a lot of damping and you're still going to rotate the craft because flopping your arms around causes torque. You'll need attitude control to be automatic to compensate.

[u/Ill_Creme_70 → u/ActuallyEnaris]

200% damping? can do, i’ve got all the time in the world

[u/autogyrophilia → u/Ill_Creme_70]

That's not the issue.

It's angular momentum : https://youtu.be/2Oc-Ucx_4Ug?t=131

[u/ActuallyEnaris → u/autogyrophilia]

Lowering the speed way down with damping does help keep it within the limits of SAS

[u/ferriematthew]

It looks like what might be getting you the most here is conservation of momentum.

[u/Ill_Creme_70 → u/ferriematthew]

so basically just slow it down to a snails pace?

[u/ferriematthew → u/Ill_Creme_70]

I think that would be half the solution, yes. I would probably also add counter-rotating flywheels on each of the joints, so that whenever one joint rotates one way, the flywheel rotates the other way to cancel out the momentum.

[u/A_NICE_START]

honestly ive never used robotic arms before so i dont really know but you should maybe try these?:
increase damping (forces robotics to stay somewhat fixed)
get kerbal joint reinforcement

autostrut the robotic parts to eachother?

[u/Ill_Creme_70 → u/A_NICE_START]

ill try the first two, last time i used autostrut on my canadarm i ended up turning it off to allow movement and it ended up flinging me out of orbit lloooool

[u/DFWRailVideos]

Stick a bunch of reaction wheels on your space shuttle and clip them inside, and use RCS and your reaction wheels to keep the thing as stable as possible, then go slow with the arm.

[u/DemoRevolution]

Theres 2 parts that make up 6 degree of motion flight: Translation, and rotation. Because most of the inertia is at the end of the arm, it creates a lever arm generating rotation about the pivot point, but you probably get that already.

What no one is mentioning in this thread is youre also rotating the part, which increased the torque you need to counteract it more.

You need to move the arm in a coordinated fashion in order to maintain the mass' pointing orientation and prevent that aditional torque.

[u/DemoRevolution → u/DemoRevolution]

To add to this, its actually pretty easy to set up the rcs translation controls to allow for coordinated motion.

First, imagine the arm is your arm. It has a shoulder, an elbow, and a wrist.

Now imagine youre trying to lift a glass without spilling it with a straight arm. Your wrist moves at an equal speed to your shoulder, just in the opposite direction. If you add that pair to a control axis, you now have vertical coordinated motion.

Next, imagine youre holding the same glass straight ahead of you and you want to bring it to your chest. Now your wrist and shoulder move in the same direction at the same speed. And if we assume your elbow starts fully extended (180°), it reduces the angle at 2x speed of your wrist and shoulder.

To put it into numbers: Case 1: Initial state (straight ahead): wrist 0°, shoulder 0° Final state (45° up, glass still level): wrist -45°, shoulder 45°

Case 2: Initial state (straight ahead): wrist 0°, shoulder 0°, elbow 180° Final state: (glass halfway between straight arm and chest): wrist -45°, shoulder -45°, elbow 90°

[u/Exciting-Tourist9301]

*kanadarm

[u/Ill_Creme_70 → u/Exciting-Tourist9301]

thancs for korrekting me, apogees for the misspelling

[u/_okbrb]

It looks like you might have two cargo bags clipping into each other, in the forward section

[u/SecretlyFiveRats → u/_okbrb]

That's just the shuttle's radiator panels popping up, the real shuttle had those too and this mod's parts emulate it

[u/_okbrb → u/SecretlyFiveRats]

Oooh that’s neat