Surface vehicle and base docking

[Jarin]

Okay, I'm looking for a bit of design advice here. I'm trying to move from orbital mechanics and the occasional docking maneuver to planetary outposts, but the methods of doing so are evading me. Specifically, I can't for the life of me figure out how to build structures designed to dock on the ground. I mean yeah, it's easy enough to just have horizontal cylinders with landing struts center-mounted, but what about vehicles? And how the heck do you dock something on the ground anyway? I think I've managed it once... and that was practically by accident while over-correcting.

My biggest problem is getting docking ports line up on anything other than practically-identical structures. It's not exactly practical to test them by launching one on the launch pad, and then the rover from the runway and spending 5 minutes driving over every time I want to tweak the alignment of something. Heck, I can't even eyeball it, since landing struts can't be extended in the building interface.

Any rule-of-thumb tips, maybe? Like, say... "X landing strut mounted radially lines up with Y wheel mounted two rotations off center" or something? How does everyone else go about this?

[DMagic]

It's not exactly practical to test them by launching one on the launch pad, and then the rover from the runway and spending 5 minutes driving over every time I want to tweak the alignment of something.

This is pretty much the only way to do it, at least that I know of. And yes, it's a huge pain. Though you don't necessarily have to do it from the runway. You can just launch the rover, drive it off the pad, you have to get far away (maybe onto the raised tracks to the VAB now, I'm not sure since they've changed the KSC), they launch the next part and drive the rover back onto the launch pad.

[nhnifong]

Here's a useful method. Once you've designed a craft that sets your docking port size and standard height, grab the subassembly that includes both the docking port and at least one ground-touching wheel, and save it with the subassembly manager mod.

Then, when editing another craft, grab a nice large flat part and hover it near your craft parallel to the ground. Then load your subassembly that defines the standard docking port height and hover it so that it's wheel just barely touches the flat part. then design the ship you're currently working on so that it's wheel also touches the flat part and it's docking port is at the same height as the reference.

Preferably do this with the same type of wheels because they have different suspension distances.

[Jarin]

Okay, finally figuring out the subassembly mod has not yet made this any easier... but it's made everything ELSE so very much better, so I'll keep trying.

[Jarin]

Okay, so here's my problem. Technically two problems. I'm trying to use a 4m (that's the orange tank width, right?) fuselage as my base "core", set horizontally, with the heavy lander legs in symmetry along the sides. However...

1. I can't extend the legs in the builder to see where it would line up to something else... and

2. I don't have a good way to vertically adjust the docking ports on another unit (say, a heavy rover).

Sorry if that's not entirely clear. If need be, I can post some pictures this evening when I get home.

[DMagic]

After digging around I finally found this old post I made about dealing with this issue. Nothings really changed since 0.19 regarding this, so everything should still apply.

http://forum.kerbalspaceprogram.com/showthread.php/27668-Tricks-hints-and-important-lessons?p=340578#post340578

[Tiron]

The docking systems really weren't designed to work on the ground. The magnetic attraction isn't really strong enough to pull the ports into alignment when on a surface.

Personally I use Kerbal Attachment System for this sort of thing, because you can have a kerbal grab the cable, haul it over to the other vehicle and attach it. Still a bit tricky figuring out how to mount it, but once you've got that figured out the actual connection is a breeze.

[Valley]

Just to let you know, even if they line up properly on Kerbin they will not on other planets or moons. I had this problem - different gravity makes the wheel suspensions react differently.

[dave4002000]

The docking systems really weren't designed to work on the ground. The magnetic attraction isn't really strong enough to pull the ports into alignment when on a surface.

Personally I use Kerbal Attachment System for this sort of thing, because you can have a kerbal grab the cable, haul it over to the other vehicle and attach it. Still a bit tricky figuring out how to mount it, but once you've got that figured out the actual connection is a breeze.

^^This

I have long given up on trying to dock modules while on the surface. Connecting everything with KAS cables is so much easier.

[Wesreidau]

Use a crane-style rover and KAS to move structural elements together.

[Skorpychan]

I resorted to making bases out of identical wheeled rovers that can simply be rammed together until they dock, or something breaks. It worked great on kerbin; hooked together after a few tries, and then went roaming happily around until I crashed them into the launchpad and the whole thing exploded. I have yet to land two on the mun intact, and so can't say it works on rough terrain.

Standardised design is your friend.

[Tripzter]

My experience with docking land vehicles has been...bad.

The main problem is the suspension.

Once you dock the suspension tends to get "stuck" in the position you docked in so if your vehicle is at a 20% incline once you undock it will remain at a 20% incline. So say the rear tires are in the air.. they will remain in the air and wont come down.

I tried making a trailer looking thing for my rover.. yeah no luck.

[Jarin]

Use a crane-style rover and KAS to move structural elements together.

I think maybe I'll give this a shot tonight. If nothing else, the utility rover can double as a base-location surveyor on Minmus. Can't find a kethane deposit with a flat landing spot for the life of me.

[M5000]

Don't worry, OP. I've still never built a proper surface base.. I don't have a good way to get my stuff down on the planet I want, first off, it's usually just one module and then I abandon the whole project.

However, I have to promote the KAS-and-crane idea. You get a crane that's easily high enough to go over any module you may put on the base, then have a central crane that can raise/lower the part.

Then, just drive the rover into place, and lower the module to the right height. Inch forward for the final dock and it should go just fine. Then, deploy the legs on the module you just docked, assuming you're building a base with the horizontal-2.5m-parts-docked-on-end method. (Orange tank is 2.5m, by the way.)

To build a rover that will dock with your base (definitely build the rover for the base, not the base for the rover), you can design it with a 2.5m fuselage and put whatever wheels you want on it. Just remember to equip it with landing legs that are the same height as the other 2.5m modules so it can support itself. As long as the landing legs reach past the wheels of the rover, you'll be fine. Use your big crane to dock the smaller one in place, then again deploy the landing legs for support.

The biggest problem I have personally is getting the stupid thing to wherever I want to have my base... The stock game is really not very conducive for building anything interesting on the ground..

[Jarin]

Well, it's just a Minmus base, in my case, so getting down to the surface is trivial. And I finally got a stock heavy lifter that I feel good about, so I'm wanting to get into some bigger projects.

Can I refuel through a KAS cable connection? If so, I might not bother having a fully-dockable rover, and just use my MUV for vehicular fueling.

[Tripzter]

Expect the rovers to be fairly bad on the minimus surface. the very low gravity makes driving them a pain. Might as well fly your person to there using the jet pack.

I landed a rover on the moon... havent touched it since for that reason.

Edited August 6, 2013 by Tripzter

[Jarin]

I expect I'll be building the vehicle as semi-flight capable. Probably a standalone vehicle that can land and reorbit by itself, and just happens to have wheels.

Also, I've seen mention of using ion thrusters mounted dorsally to hold a vehicle down in low gravity. I assume that would probably only be useful on really small/light vehicles?

Alternately, since I fully expect to have a mini-refinery on the utility vehicle, just low-throttle regular engines, since it could refuel itself...

Edit: Honestly... since I'm basically building a micro-spaceship anyway... might I be better off just using landing gear and assuming it'll fly/float most of the time? What's the weight capacity and steering like on landing gear? Could I still use it as a crane vehicle?

Edited August 6, 2013 by Jarin

[Tripzter]

I assume that would probably only be useful on really small/light vehicles? .

Theres no mass in the acceleration to gravity equation. Remember the feather and the hammer experiment? Which one falls first on the moon.

[Jarin]

Yeah, but the smaller rover has so much less momentum when accidentally ramping off of ridgelines. <.<

Edit: Also, thrust/weight ratio doesn't go away in a vacuum.

Edited August 6, 2013 by Jarin

[Jarin]

Jeb says "any test you can walk away from is a good test"

[dave4002000]

Can I refuel through a KAS cable connection? If so, I might not bother having a fully-dockable rover, and just use my MUV for vehicular fueling.

Yes you can. There are two options when you connect a KAS cable. You can connect it in an 'undocked' mode which basically just tethers the two craft together. Or you can connect it in a 'docked' mode which allows full resource transfer and is no different than having the two craft connected with docking ports.