Docking port used as non-stage sepatron

[Callmedave]

found this by accident, but hopefully it could be usefull for you guys.

I built a two piece rocket that would operate a a small refueling rig in orbit around the mun, with a small lander attached for the final journey from mun orbit to mun surface and back.

My lander had a docking port on its nose so it could refuel after taking off from the mun, in error i assembled the rocket with a engine on the bottom of the lander, this sat on top of the docking port of the fuel rig i was hoping to dock with in orbit.

Launched this into space, once i was in mun orbit, i realized i did not have a sepatron to detach my lander from the fuel rig (it was engine on the docking port remember) so i right clicked the docking port and clicked 'de-couple' and it worked!! the lander was successfully detached, the 'shroud' ring came away, allowing for me to turn the lander 180 degrees and dock in orbit! the mission was a sucsses!

Hope that was clear enough without pictures. (i can post pics when im home if anyone does not understand) but his could hopefully help with your builds!

A docking port will only dock to another docking port, (in space) but it un-dock from any other part! This would be a very usefull way to carry, say a rover, that will not dock again once it un-coupled or a setup similar to what i was doing.

Hope this is helpfull to some of you!

[sal_vager]

Hehe, this is useful for small probes and cargo as well, as the docking port has almost no decouple strength, so your probes won't be shot away from you

[Technical Ben]

Yeah, I've sometimes done this. I generally use a double docking setup though for re-docking whenever doing this. I think of them as little "suction" plates... actually, could we have those as pre-docking port researched items?

[HoY]

I use docking ports for carrying payloads more often than stack separator because they don't seem to get crushed as easily as well (very heavy loads)

[Specialist290]

Docking port decouplers are indeed a nifty trick.

And if you put a docking port on the payload as well, you can "recover" it with another rocket in the future should you need to. That can come in handy itself.

[DMagic]

A good idea is to set up the docking port with an action group (I always put both 'undock' and 'decouple' in the same group, I've never been sure of the difference), that way you can do this more like staging and not have to deal with trying to click on a sometimes partially hidden docking port.

Be careful if you use any kind of delta-v calculator though. This will screw up the values it gives, because it doesn't know when, or if, the docking port will be decoupled.

[HoY]

A good idea is to set up the docking port with an action group (I always put both 'undock' and 'decouple' in the same group, I've never been sure of the difference), that way you can do this more like staging and not have to deal with trying to click on a sometimes partially hidden docking port.

Be careful if you use any kind of delta-v calculator though. This will screw up the values it gives, because it doesn't know when, or if, the docking port will be decoupled.

With mechjeb as soon as you are on the pad and dissable cross feed the deltaV stats will show the difference. To get accurate numbers in the VAB the easiest thing to do is install a stack decoupler between the ports. (Remove it before launching). A low profile non cross feed part you can use alternatively if you want to launch with it still installed is the structural steel plates.

[kerbomatic]

Some words of caution though since I very recently ran into a related issue:

1. If you have fuel tanks above the docking port, they will be drained first. Imagine the look on my face when I 'decoupled', saw the booster stage drift away slowly and then realized I had 0 fuel in my spacecraft left. Needless to say this craft landed on RCS thrusters without accomplishing its mission.

2. On the next flight, I 'cleverly' disabled cross feed manually to preserve my fuel before detaching. However, my craft had radial rocket engines attached to the docking port. Guess what; with cross feed disabled they won't get fuel. And after detaching there is no way to re-enable cross feed (without docking again, presumably). The flight after that I carefully re-enabled cross feed after shutting down the engines before undocking.