recoil when docking / undocking

[Execut1ve]

Hi all,

I am working to establish a modular base system and am in the process of testing the components landed on Kerbin. I am using a small rover with a docking port on top to mate with a docking port on the bottom of my base sections, move them into place, undock and drive off. The problem occurs immediately after a docking port is docked or undocked - the whole craft lurches significantly. If undocking, the base section (with the downward facing docking port) flies off in a random direction, and comes to rest several meters away and sometimes even flips over. Components seem to randomly explode also.

Has anyone else noticed this? Is there some obvious error in craft design or procedures I'm making?

Any guidance is appreciated! Thanks for reading!

Edited May 21, 2018 by Execut1ve

[bewing]

Welcome to the forums.

Yes, the docking ports have a built-in ejection push. I'm afraid you can't change it in the stock game -- you have to take it into account when you are building your craft. You can modify the ejection force of the docking ports in the config files if you choose to do so.

 

[Not Sure]

29 minutes ago, bewing said:

Welcome to the forums.

Yes, the docking ports have a built-in ejection push. I'm afraid you can't change it in the stock game -- you have to take it into account when you are building your craft. You can modify the ejection force of the docking ports in the config files if you choose to do so.

 

They do.. but I don’t think it’s as violent as the OP describes. It’s like a .05kn tap.

[bewing]

That is true. If there are any collider issues around the docking port, however, then the force can be a whole lot larger.

 

[Execut1ve]

I'll try rebuilding the craft and base section in question, keeping everything extra clean around the docking ports

[bewing]

You might want to use the offset tool to move the docking port out just a little -- and see if that fixes the problem.

 

[Execut1ve]

no luck so far - in fact it seems like offsetting the ports to protrude more has made the recoil worse!

[Geonovast]

Really hard to suggest much more without pictures.  Can you upload some screenshots?

[Vanamonde]

The parts "come to rest"? So you are docking while landed? Sounds to me like the craft are not precisely aligned so that they are under tension when joined, which is then released when you undock. 

[Dark Lion]

5 hours ago, Vanamonde said:

The parts "come to rest"? So you are docking while landed? Sounds to me like the craft are not precisely aligned so that they are under tension when joined, which is then released when you undock. 

If it docks, it could also cause parts to clip through one another, either by poor alignment, alignment of parts or even when sections of the craft are too heavy and "sag" into parts below. Undocking would be the random katastrophe for sure when those parts separate. Parts might even break Ludikrus Speeds on the way out, if you're lucky. 

[Execut1ve]

after some experimentation, I have a theory for what is happening:

In Kerbin's gravity, the landing legs supporting the pieces are compressed somewhat. When the docking port is undocked, each leg imparts a force on the craft proportional to how compressed it was (so it would seem)

I downloaded HyperEdit and tested changed the gravity to Minmus levels. The landing legs were barely compressed, if at all, due to the decreased gravity. I did not notice any parts jumping around or exploding or undocking, so that's good enough for me as Minmus is where these pieces are headed anyway!

Thanks all for the input!

[bewing]

Just FYI -- it's possible to modify gravity in the stock game for testing designs, using the debug menu (the "hack gravity" feature). So you didn't really need Hyperedit for that.

 

[Geonovast]

Just now, bewing said:

Just FYI -- it's possible to modify gravity in the stock game for testing designs, using the debug menu (the "hack gravity" feature). So you didn't really need Hyperedit for that.

 

Does hacking gravity affect anything in orbit?

I use the hack gravity system for testing, but I do it in a separate sandbox save where nothing matters.

[Execut1ve]

5 minutes ago, bewing said:

Just FYI -- it's possible to modify gravity in the stock game for testing designs, using the debug menu (the "hack gravity" feature). So you didn't really need Hyperedit for that.

 

now that's handy - sure to save some R&D time in the future!

[bewing]

10 minutes ago, Geonovast said:

Does hacking gravity affect anything in orbit?

Yes. Best to do it in a separate sandbox.