Looking for a Solution to Securing a Floppy Robotic Arm

[mojobojo]

I am looking for a little design help in a spacecraft. If it's not clear by the image I am using quite a few mods. Basically my issue is that my robotic arm is flopping all over the place and I am looking for a way to secure it for launch, then be able to move it around in space, then secure it back for reentry. My main issue is that it moves out of the cargo bay when launching causing stability issues due to Ferram Aerospace, same deal on returning but it's much worse and a challenge keeping it on the right track so I don't end up in a fatal stall. My only solution right now is securing it with struts attached to a decoupler for liftoff and have another decoupler for returning and I just jettison it when I am returning to Kerben. I would prefer not to do that because it ruins my reusablility aspect (although tehnically not there in the first place). Any suggestions on any ingenious way of using parts like they shouldn't be used or any mods to help remedy this would be greatly appreciated.

I would have taken an image of the return but I needed to keep the thing stable as I recovered from a stall which led me to only recover a few km above kerben.

Really these pictures aren't necessary but I like to show off my creation.

Edited March 27, 2014 by mojobojo

[Wayfare]

Have you considered docking ports instead of decouplers?

[mojobojo]

Have you considered docking ports instead of decouplers?

Because the arm is considered part of the ship the docking ports don't collide with each other.

[Wayfare]

Because the arm is considered part of the ship the docking ports don't collide with each other.

Even so you should still be able to dock them up - it's the same principle as people who use multiple docking ports as structural connectors in the VAB (they dock when physics load) or even in docking operations (they never dock at exactly the same time, so at some brief point there is one ship docking several ports together on itself). Unless KSP is being, you know, KSP about it

Though honestly it seems like more of an issue with the rigidity of the arm itself and you may want to ask around in that mod's release thread for advice.

[merendel]

Silly question but is there any reason you couldnt attach the arm to the other side of the cargobay? Right now you have it on the back end and when under thrust the rigidity of the joint must overcome any moment of force applied to the whole arm to keep it from pivoting. Basicly it has to stand up under some number of G's and not tip over. On the other hand if you attach it to the front it would be hanging from the ceiling when under thrust and shouldnt go anywhere.

[mojobojo]

Silly question but is there any reason you couldnt attach the arm to the other side of the cargobay? Right now you have it on the back end and when under thrust the rigidity of the joint must overcome any moment of force applied to the whole arm to keep it from pivoting. Basicly it has to stand up under some number of G's and not tip over. On the other hand if you attach it to the front it would be hanging from the ceiling when under thrust and shouldnt go anywhere.

That's a good idea worth exploring. However I think it has more to do with when I move, like it will be stable until I try to fix my trajectory or do a gravity turn.

Even so you should still be able to dock them up - it's the same principle as people who use multiple docking ports as structural connectors in the VAB (they dock when physics load) or even in docking operations (they never dock at exactly the same time, so at some brief point there is one ship docking several ports together on itself). Unless KSP is being, you know, KSP about it

Though honestly it seems like more of an issue with the rigidity of the arm itself and you may want to ask around in that mod's release thread for advice.

Yeah its the Infernal Robotics mod that I used for the arm. I am sure they know about how the parts lack rigidity. Perhaps there is a setting in the save I can edit.

[merendel]

That's a good idea worth exploring. However I think it has more to do with when I move, like it will be stable until I try to fix my trajectory or do a gravity turn.

It shouldn't mater too much. IR parts are generally rigid enough to return to their zero point in a micro gravity. It might flop a little bit if you apply alot of torque suddenly but it should zero out after a bit. The advantage of it hanging is its naturally going to want to align with the axis of thrust. assuming normal rocket design that basically means its going to hang strait down towards the rocket. During a gravity turn it may deflect slightly depending the shape of your turn. On the other hand the forces pulling it out of line will be negligable compaird to the thrust and rigidity trying to pull it back into line when its hanging vs thrust and gravity trying to upll it out of line and only the rigidity fighting that.

[mojobojo]

It shouldn't mater too much. IR parts are generally rigid enough to return to their zero point in a micro gravity. It might flop a little bit if you apply alot of torque suddenly but it should zero out after a bit. The advantage of it hanging is its naturally going to want to align with the axis of thrust. assuming normal rocket design that basically means its going to hang strait down towards the rocket. During a gravity turn it may deflect slightly depending the shape of your turn. On the other hand the forces pulling it out of line will be negligable compaird to the thrust and rigidity trying to pull it back into line when its hanging vs thrust and gravity trying to upll it out of line and only the rigidity fighting that.

Then perhaps then its to do with the amount of torque I changed a SAS module to with the part tweaker mod. I needed to make it much stronger for the stability of my asymmetric launch.

EDIT:

Putting the arm on the other side increased ship stability. However I cannot grab payloads and it still has a major case of the wobbles when I return.

Edited March 28, 2014 by mojobojo

[Ascension Islander]

Have you tried Kerbal Joint Reinforcement?

[Vanamonde]

This looks like a job for Gameplay Questions! (Moved.)