Docking while on the ground

[Sharpy]

I've tried making a fuel harvester and a fuel truck as "flying cars", standard wheels, radial-mounted engines for take-off, then a main engine for flying. Considering one would be working on Minmus, the other ferrying fuel between Minmus and LKO, that was a reasonable idea. And since both were built similarly, identical "chassis" and only different payload (one - extra fuel tanks, the other - big cargo bays filled with machinery, ore containers etc) it stood to reason that if I attach docking ports in respective places, I should be able to drive one up to the other and "dock" to transfer the newly made fuel.

Except I hit some bug. I tested this on Kerbin, and the two vehicles would at first refuse to dock. Then docking happened... except control wasn't returned with both vehicles made one. I still controlled one, while the other would stay fixed to a place - that's an interesting notice, as when I switched vehicles, I could make the wheels bend and eventually even break off as they pushed against the ground while the vehicle stood fixed in place. I could start the engines, but they wouldn't move me. The docked vehicle would fight against the dock. Generally, while everything worked, one vehicle would remain in a fixed position in space.

What's worse, that bug propagated onto later instances; suddenly it hit me mid-flight and left me stuck in one position in space, stopped in the orbit.

Is this some known issue - just "don't dock on the ground"? Some workarounds? Or was I just unlucky?

Edited June 6, 2015 by Sharpy

[Ferdoni]

Did you test the docking directly on the launchpad?

And could you also post some screenshots?

[LittleBlueGaming]

What's worse, that bug propagated onto later instances; suddenly it hit me mid-flight and left me stuck in one position in space, stopped in the orbit.

I've experienced this three times, twice with the same craft. First launch the cockpit was stuck in space, so when the clamps released I wouldn't go up, but could pivot around the cockpit. Reloaded and launched again, and everything was fine until I did a 5x time warp. Everything started turning into spaghetti around the cockpit, until it broke off from everything and flew off on its own.

Third time was a probe I was sending to Eve. Everytime I load it now, it won't move. It's been 30 days away from the next maneuver node for half a year.

Not aware of any workarounds other than closing and restarting the game(and hoping).

[georgTF]

Surface docking is often frustrating. Partly because it's difficult to align the docks and you need a lot of field test and returns to VAB/SPH to correct dock position etc.

But a bigger problem is gravity. Fuel transfer, which is a major reason to use surface docking in the first place can cause docks to mis-align. Once you transfer fuel between craft and undock, you may find it impossible to dock them again because one of them is now heavier and it's dock sits lower than before. Similarly the other craft is lighter and it's dock moves up. This problem can strike even before you dock them. If you test docking on Kerbin and succed, you may fail at docking the same two craft on Minmus for example, because the gravity is much weaker there causing suspension to compress less.

The ideal way to perform temporary surface docking is to use a clawed tanker vehicle and design vehicles that will be targetted by the claw with enough clean space for the claw to attach. The claw doesn't like landing legs, sticcking batteries, panels or such small and fiddly parts.

Finally, never driver a vehicle into the claw, as that is a surefire way to cause major issues.

Due to game limitations and my previous experience, i try to construct "base" buildings as self sufficient, wheeled vehicles without any intention of ever docking them together. Wheels because it's easier to move it on it's own power once i decide it's not in the perfect location. I also keep the part count low at the expense of aesthetics and prefer to keep no "buildings" closer than 3km to each other.

There have been very strange bugs regarding craft docked on the surface. Going back 2 years i remember having problems and usually explosions. The game doesn't like having the ground nearby when calculating the new CoM of the combined craft. Even worse if one was substantially lighter than the other, or used lightweight parts between it's own CoM and the docking port (for example to extend or raise it's position, clear wheels/other parts). Kraken summoning almost guaranteed if one craft used clipping, even minor clipping.

I've had a 5t rover flip and launch a 80t fuel tanker almost a kilometer high after docking. This was on Kerbin. Docking ports are weird and buggy. Juniors are worst offenders in my experience. So in the end i try to avoid docking altogether and use claws for surface refuelling. As wonky as claws are, they are safer!

[Sharpy]

@Ferdoni: Launchpad, runway, field next to the runway... the results were the same.

@LBG: Yep, I don't know if it was the same bug or another but later on things took a turn for bizarre. I had sent a craft with a probe to Minmus to perform an orbital scan. My overly efficient launch platform still had enough fuel to bring my probe carrier to Minmus; they separated shortly before entering Minmus SOI, the launcher platform aligning for crash into Kerbin, the carrier entering polar orbit at 26km. Probe deployed, mission complete, carrier with 90% of fuel left, let's leave it somewhere where it would be usable later - just for fun I landed the carrier craft on Minmus (*almost* successfully; it broke in half but didn't fall apart; it stands vertically on its engine slightly misaligned in the middle, a Kerbal monument on Minmus.)

I must have angered some gods of Minmus. I struggled with constructing these two landers, performed some orbital science in Minmus orbit, reloaded several times (not the game, just save) until I gave up as the lander would freeze in orbit, and finally I realized on top of that one returning lander platform, I have 3 different crafts returning from Minmus. All they were the scanner probes still within carrier and the last stage of the launch platform attached. And as I'd switch to any of them, it would explode within a minute or so, and not even show the common courtesy to turn into debris, but show up as 20 or so "probes", including "probes" that consisted of a single metal grider. And they kept floating in space refusing to move in the orbit.

A long time later I got the idea to quit and reload, and they all started moving, along their crash trajectory. Finally the sky is down to standard junk. And the lander (fuel truck) is unlocked. I can try bringing it to Minmus.

This is the fuel truck on launch; I didn't take screenshots of the ghost probes but I'll try to take screenshots of the rest of the stuff.

Edited June 6, 2015 by Sharpy

[Laie]

If they shall only transfer fuel, not ever take off together... I suggest using the universal connection piece claw.

This is from way back when, what I suggest is in the upper right.

[mrklaw]

Is it KAS that has the umbilical hoses for connecting elements together? Seems like that should be very useful if you want larger bases on the ground. A better system for connecting multiple buildings/vehicles in the ground should definitely be added to the stock game.

[Mic_n]

Yup.. KAS can let you 'hose' things together, with connectors and ground points and the like. Though as mentioned, the Klaw is also an option.

As to compressing suspension.. the lander legs and landing gear have the option to lock out the suspension (can't remember about rover wheels, though I think they do as well?). Might be worth trying that, though I don't remember whether that locks the suspension where it is or at full travel.. you might need 'sets', where you can deploy a longer set of gear to hold your wheels off the ground (hence at a fixed length), lock those ones in position, then retract the 'stilts' to sit at a reference height.

[Sharpy]

Thanks all for the answers. Fuel truck just docked with the Klaw to the miner on Minmus, without a hitch (other than horrible landing). Another truck is being launched as I'm typing this Now the orbital station is gonna earn a new set of tanks to fill, and I'll be ready for interplanetary journeys.