Docking ports wont dock

[lugge]

So, I'm finally working on my Minmus outpost.

I built a small rover which will drive beneath the various outpost modules (yeah, nothing really new :-) )

All my modules have a docking port at their bottom.

My rover then will activate its feet, thus, lifting of from the ground to lower the distance to the module's docking port (this may be new? :-) )

The idea is that, after this step, the docking ports get attached to each other, which will let my rover completely leave the ground.

Then I can retract the module's and the rover's feet and drive around.

Well, as you can see, no docking going on.

The ports are perfectly aligned, however, this cannot be seen in the picture.

Whats the problem?

Is there maybe a weight limit for what a docking port can handle?

I even attached a battery and an probe core to the module because i heart docking needs electricity (is that true?)

Any ideas?

Greetings,

lugge

Edited August 18, 2015 by lugge

[capi3101]

Assuming the port on the rover is not upside down, it could just be that Kerbin's gravity is overriding the magnetic force of the two ports. Try hacking gravity and see what happens.

[Vanamonde]

This should work, but the magnetism of the rings is pretty weak and won't lift the vehicle. Have you adjusted the legs so that the rings actually touch?

[Red Iron Crown]

What happens if you retract the upper module's landing legs?

[Sharpy]

I'd start with the gravity hack. Adlusting the legs to work in Kerbin gravity will make them quite misaligned on Minmus.

[Stoney3K]

Assuming the port on the rover is not upside down, it could just be that Kerbin's gravity is overriding the magnetic force of the two ports. Try hacking gravity and see what happens.

That shouldn't be an issue once docked? If the top vehicle were to lower itself onto the port, the two would dock (and the rover would 'disappear' as a separate vehicle) and they would have a solid connection after that.

As I can see it now, the gap is too big for the ports to attract. Put some part in front of the module's docking port to lower it and reduce the clearance, or raise the docking port on the rover.

[Brainlord Mesomorph]

I do that. It works.

Doesn't look like they are close enough.

[xtoro]

If it's gonna be on Minmus, you could ditch the legs and just use RCS thrusters to lift the rover once you're underneath it. That would eliminate messing with leg heights and having the perfect distance between docking port and ground...

[lugge]

What happens if you retract the upper module's landing legs?

Hah, worked! Shame on me :-)

However, thats still not sufficient. This would mean, I have to attach a probe core (and energy) to all of my modules.

Some of them are passive, like the connecting tubes between habitats. I just connect two structural fuselages and add docking ports.

Thus, I cannot retract the feet on some modules.

Maybe this is really just a Kerbin problem. When my rover is under the module, it drives back and forth a little when I don't hit the brakes.

Seems to be the magnetic force. It's sufficient to let my rover ... rove, but not strong enough to lift it up.

I will try the gravity hack. If my rover lifts of with Minmus gravity, all should be fine.

- - - Updated - - -

Ok, another update:

I placed the rover's docking port above a structural grid.

Now, when I extend the rover's legs beneath the module, the ports are touching each other, and, they dock :-)

It looked this close before, I really thought that should be working...

Thank you guys, you saved my evening :-)

[lugge]

Ok, seems that I encountered the next problem:

The ports are not on the same height!

I aligned the legs with the docking ports, thinking this way they will match when the legs are activated.

Is this because my habitat module has more weight?

If yes, what is the solution? Aligne the legs in the VAB by guessing?!

And how does this work with fuel tanks?

They will change in weight when I load the fuel to a docked spacecraft. Will this tear my base apart?

Evening not saved

[Stoney3K]

Try locking the suspension on your landing legs. They may sink a little due to the module's weight.

[xtoro]

If it's gonna be on Minmus, you could ditch the legs and just use RCS thrusters to lift the rover once you're underneath it. That would eliminate messing with leg heights and having the perfect distance between docking port and ground...

Try this! RCS is enough to lift a rover off the ground on Minmus.

[mellojoe]

Ok, seems that I encountered the next problem:

The ports are not on the same height!

You have discovered the #1 problem with docking land-based modules. Getting the docking ports to match is a feat that is sometimes impossible. When I did my Mun base, I ended up using Kerbal Attachment System to dock modules together using the flexible piping.

On systems with lower gravity (like Minmus), you can wiggle things around and get them to align. But on the Mun, Duna, etc, that can sometimes not be sufficient.

[lugge]

You have discovered the #1 problem with docking land-based modules.

Yeah, I discovered something :-)

Ok, but when everyone sooner or later comes to this point:

Whats the solution?

I cannot imagine that "guessing" is the proper way to solve this issue.

Moreover, if I just adjust the ports, hoping that it will work on Minmus, I cannot test my base on Kerbin anymore, due to its stronger gravity.

Maybe this "Suspension lock" is the solution?

Unfortunately, I can test this not before tomorrow evening :-(

However, there must be some kind of best practise?

Greetings,

lugge

[Sharpy]

For low-gravity words, RCS is the solution.

[lugge]

For low-gravity words, RCS is the solution.

How is RCS the solution when the docking ports aren't on the same height due to leg suspension, caused by the heavy weight of habitat- or fuelmodules?

Please note:

My initial question is solved. I now have another problem :-)

[Starhawk]

RCS thrusters are powerful enough to move around and lift even fairly heavy craft in Minmus low gravity. That will allow you to wiggle your craft into place until the docking ports click.

Happy landings!

[lugge]

RCS thrusters are powerful enough to move around and lift even fairly heavy craft in Minmus low gravity. That will allow you to wiggle your craft into place until the docking ports click.

Happy landings!

But that would mean, every single module needs to have RCS capabilitys, monoprob and engines.

Another problem I can think of:

Imagine a habitat module using RCS to slowly lift up and gets docked to my connector tube.

Now, after docking, RCS is shut down.

Wouldn't the hab's legs suspense again, taking the connected module with it?

Thus, messing up the whole base?

The same with fuel tanks:

Imagine an orange tank, slowly getting filled via ISRU.

Now, a full orange tank is quiet heavy, also messing up my base when it's getting fulled?

[goldenpsp]

Yeah, I discovered something :-)

Ok, but when everyone sooner or later comes to this point:

Whats the solution?

I cannot imagine that "guessing" is the proper way to solve this issue.

Moreover, if I just adjust the ports, hoping that it will work on Minmus, I cannot test my base on Kerbin anymore, due to its stronger gravity.

Maybe this "Suspension lock" is the solution?

Unfortunately, I can test this not before tomorrow evening :-(

However, there must be some kind of best practise?

Greetings,

lugge

He already said the solution. It's called "there's a mod for that". Namely Kerbal attachment system or KAS.

[cantab]

Hah, worked! Shame on me :-)

However, thats still not sufficient. This would mean, I have to attach a probe core (and energy) to all of my modules.

Some of them are passive, like the connecting tubes between habitats. I just connect two structural fuselages and add docking ports.

Thus, I cannot retract the feet on some modules.

I recommend a probe core on everything you want to keep anyway, otherwise it'll be considered debris and there's a chance the game deletes it. Probe core + RTG/OX-STAT is only two extra parts.

I do recommend the over/under docking rather than the side-by-side method, because of what you found about ports not aligning.

[Sharpy]

But that would mean, every single module needs to have RCS capabilitys, monoprob and engines.

Nope, you need only one drone with the Klaw to do all the engineering work of moving and adjusting the modules.

Another problem I can think of:

Imagine a habitat module using RCS to slowly lift up and gets docked to my connector tube.

Now, after docking, RCS is shut down.

Wouldn't the hab's legs suspense again, taking the connected module with it?

Thus, messing up the whole base?

The same with fuel tanks:

Imagine an orange tank, slowly getting filled via ISRU.

Now, a full orange tank is quiet heavy, also messing up my base when it's getting fulled?

That's why the ports can't be too far, and why you need to "lock suspension" on legs of modules that can become massive.

[Starhawk]

But that would mean, every single module needs to have RCS capabilitys, monoprob and engines.

Another problem I can think of:

Imagine a habitat module using RCS to slowly lift up and gets docked to my connector tube.

Now, after docking, RCS is shut down.

Wouldn't the hab's legs suspense again, taking the connected module with it?

Thus, messing up the whole base?

The same with fuel tanks:

Imagine an orange tank, slowly getting filled via ISRU.

Now, a full orange tank is quiet heavy, also messing up my base when it's getting fulled?

Not being much of a base-builder, I can't say for sure, but the docking ports have considerable flexibility and a reasonable attachment strength once docked so the module should stabilize. Either that, or tear the entire base apart.

As far as having a probe core, power, RCS fuel, and thrusters on everything. Have you considered a tractor/tug which had all the RCS and power and could maneuver the modules into place? It could use either docking ports (if the module is equipped with more than one), or the klaw. Once again, I don't know how practical that is, not having much experience with surface bases other than my Minmus mining operation, which is easy because it's on one of the flats.

Happy landings!

edit: Ninja'd by Sharpy.

[mellojoe]

My solution has been ... docked single craft for orbital stations and separate modules on the ground near each other and "roleplaying" as a single base.

[Pecan]

It's all lovely on the flat, once you've spent weeks getting it all together.

Then you land somewhere that isn't a simple plane, and the docking ports won't even point at each other enough to dock.

KAS, other mods, or forget it.

[Overland]

WARNING - THE FOLLOWING CONTAINS TRACES OF TRAINS - AVOID IF ALLERGIC

(sorry its the best way to explain docking ports on land..)

[TRAINS]

I deal with docking ports on the land alot. actually never in space.. im a train driver not a rocket pilot generally.. so im constantly shunting trains using docking ports..have been over a year so I got the fair level of experience even on rough terrain..

The solution I use for trains.. be it locomotives, wagons and suchlike to maintain height.. I use a standard bogey set.. in the subassembly of SPH.. eg everything has the same 3 truss and wheel sets then attached to that whatever its going to be.. then I modify the wheels accordingly for what its use is..

example. 40 class with booster and wagons & 44 class constructed by same system

What you should do likewise is construct a base with landing legs of locked suspension height like suggested earlier.. then copy that into subassemblies.. then base everything off that or put that under everything.. so the height is the atleast touching the ground wise..

it works for my trains.. not all that different to what your trying to do

a pointer I can give though since 1.0+ upgrade is docking ports are rigid as hell for no good reason.. I used to be able to have a train with docking ports straight onto the wagons turn effortlessly.. but these new things its like trying to turn a metal bar..

Eg.. no spaces between the docking ports = bad idea.. for a train and your base too

if your worried about your base flexing when you connect and you actually WANT it to absorb some movement..

put a truss between the docking ports and the vehicle/building/tank.. look at my above train with no spaces vs the earlier screenshots.. putting a truss mounted onto something.. then a docking port on that gives alot of flex.. very useful

they let the trains turn almost 90 degrees without harm...bob with the terrain and generally act like couplings.. not hard docking ports... so your base should be able to flex and not take everything else with it

TRUSS - DOCKING PORT-DOCKING PORT-TRUSS

take note at 1 minute as 4003 turns the corner out of the yard, thats what I mean

they'll still transfer fuel and power.. thats how my trains run.. the wagons are fuel.. if it didnt. they wouldnt get far

Also!.. I see your using that docking port junior in the first screenshot.. dont

its a nasty little thing.. quite fussy and worst of all. when its hit by anything it actually slides away from the part, also coming away with weight or in my case torque of the locomotive's acceleration or braking.. it always springs back and creates a terrible energy filled spring force..

use the standard sized docking ports.. they seem to lock easier.. their much stronger and they dont float around their own neighbouring part if hit.. they stay in 1 spot.. I use them for trains all the time now.. I used the smaller ones for a few months in the early landliner class locos.. im glad I made the change

[/TRAINS]

Edited August 20, 2015 by Overland