You may have noticed when I recently put my moonbase down on Minmus that the base had two XL Modular Girder Segments sticking out one either side with docking ports on the ends. The reason for those was: future expansion! And the future is NOW.
I used the same carrier rocket that I used to deposit the first part of of the moonbase on Minmus, except that I added some wheels in the form of landing gear mounted on the same struts that the landing legs are mounted on. I left the landing legs in place so they could be used to absorb the shock of the initial landing. Then the landing legs can be retracted to allow the ship to settle onto the wheels. And then the ship can be driven over to do a "ground docking" with the previous segment of the base.
Below we see the launch of moonbase part B. Much of the fuel in the carrier's main and side tanks is used to get the ship into Kerbin orbit. After that, the fuel that is in the tanks that are being used as part of the moonbase structure is transferred into the main tank of the carrier (as described in my original moonbase post). Then the carrier has plenty of fuel to carry the now-much-lighter moonbase structure to Minmus.
Below we see Part B and its carrier in Minmus orbit. Notice the sideward facing LV-909 engines. I put these on the ship in case it took a lot of thrust to move the thing around on Minmus. This turned out to be unnecessary (the RCS was strong enough with all those linear ports), and the engines were a real bother since I had to keep activating and deactivating engines (I set up action groups to control the LV-909's, but I forgot to set up one to activate/deactivate the four main motors, so I had to do that manually as needed). So ignore those side facing engines, since they were not a good idea.
After the initial landing near the moonbase, I did some small hops, hovering the carrier while using the RCS to place it as close to the right spot as I could, since I didn't know yet how easy it would be to drive the thing around. The expansion girders of the moonbase are aligned toward northwest and southeast. I lowered the carrier onto its wheels by retracting the landing legs. There was only a small clearance between the bottom of the moonbase modules and the surface when the ship was resting on its wheels (to make the docking easier). This is another reason I kept the landing legs: I did not want to have the land the ship on its wheels with such a small clearance because of the possibility the landing gear compression bounce might allow the moonbase modules to be damaged if the landing was too rough.
It turned out that it was not TOO hard to drive the ship around using the RCS, but it was important to not go too fast since it took the brakes a long time to stop the ship. Once I got the docking ports close together, the magnetism of the ports was able to start drawing the ports together because of some flex in the structures. But the port on the Part B segment of the moonbase was still a little too high to allow a docking while connected to the carrier. But I got everything lined up as closely as I could...and then I blew the separator that held the moonbase section to the carrier. It dropped the short distance and latched a nice docking. After that, I hopped the carrier up off the moonbase and landed it a short distance away. Below we see the successful connection.
Below we see Minmus Moonbase parts A and B linked together. With a successful docking, the parts of the base can share power and transfer propellant, if desired, and all of the lights can be controlled at once.
Below is a picture of the carrier after hopping away. Now that the moonbase segment is gone, it's easier to see the arrangement of the landing legs and wheels.
And here the landing legs have been retracted so that the ship sits on the wheels. The bottom of the moonbase modules was about even with the axels of the wheels in this configuration.
But we aren't done yet! Part B of the moonbase was very similar in appearance to Part A, designed for habitat and some experimentation. Now that I knew the ground docking procedure worked, I modified the design to make Part C of the moonbase, which would be a section for heavy-duty experimentation and manufacturing process testing that required more power. Same basic structure, of course, but tweaked to look a bit different. Below we see the launch of moonbase Part C.
Here we see the trans-Minmus-injection burn of the Part C carrier. You'll notice that the engine exhaust fires pretty close to the structure of the moonbase modules and 'hallways', but as long as the program doesn't complain about damage to the parts, I'm cool with that.
Below, the Part C carrier has landed and is ready to start the driving phase. I didn't try to get as close this time since I knew the driving worked well. I did add some additional RCS thrusters to this carrier to make it a bit more maneuverable. And the silly side-facing LV-909s are gone, of course.
I mainly viewed things from straight overhead as I slowly moved the carrier into place. The wheels sort of stick in place when the ship is stationary, and it takes a burst or two of RCS to get it moving...but once its going, just slowly creep along and push and twist the ship as needed to line up the docking ports. After I got the ports together (with one a little high) I jiggled and jostled the carrier to see if there was enough flex in the structures to get a solid docking while Part C was still connected to the carrier...but there was not. The magnetic effect WAS strong enough to actually pull the ship closer from a tiny distance. And when I blew the separator, Part C dropped nicely into place and the magnets did the hard docking.
Then I hopped the carrier up and used the RCS to push it off a little way. You can see it behind the completed moonbase in the picture below. Part C of the moonbase has a nuclear engine that (I'm assuming) has been adapted so that the base can use the engine's reactor to power experiments that require large amounts of power (and could power the base at night if the RTGs on the various parts are insufficient). There is fuel for the engine in the tank tower on the opposite module of Part C.
Here's a view of the other side of the completed moonbase seen from the northeast. Or maybe it's not completed... it still has enpty expansion arms that could be added to in the future.
Here's Minmus Base as it currently exists. Now it just needs me to ship some kerbals up join Gergan and Cammon in inhabiting the base. But first I really do need to move those carriers off a suitable distance to reduce the lag problem that is starting to become obnoxious. Too many parts in close proximity. How far do I need to move them? Two kilometers? Four? I don't want to just throw them away, since those ships contain valuable stores of fuel and RCS fuel that could potentially be used if only my kerbals had some nice hoses to run between the ships. Maybe that will come later in the game. A nice "tank farm" would be a good addition to the base, if it was useable. Oh...there was an odd thing happening with the lights on the moonbase. I have the high-intensity area lights turned off (since they can be obnoxiously bright), but the lights over each of the twelve module entrance doors are on...but several of them on Parts B and C don't have their illumination showing up on the surface. Very strange.