I've built the following ship, which is capable of taking me to the Mun. However, with some careful piloting, I can make it into a stable Mun orbit with a bunch of fuel still left in the second-to-last stage. So if I want to land on the Mun, I have to decouple my lander module from the rest of the ship, and abandon any spare fuel I might have left in the tank.
So, I came up with the idea of using a docking clamp to attach the capsule to the main ship instead, so that I can leave my fuel in orbit when I want to land, and return to it later after returning to orbit from the surface.
Only problem is, I have no idea how docking clamps work. I'll learn how to approach docking maneuvers later, what I'd like to know NOW is how I should build the connection between the two sections to make this possible. I've circled the current decoupler in the image below.
Best Answer
Docking clamps have very little shear strength, so I suspect if we just changed the decoupler into two docking clamps, your cockpit would fall off during the ascent.
It's a bit more complicated to replace decouplers with docking ports; decouplers just fire off of your current stage, and stick to the stage you might want to return to. That doesn't work so well when you want the decoupler to detach from BOTH stages, leaving the docking port free for later use.
So what you want is:
Pictures of this will be forthcoming shortly.
This setup will allow you to take it back to Kerbin (if you have enough fuel remaining), and leave it in orbit for future use.