Best way to set a small space ship with 2 docking ports in a SSTO Cargo hold

[gilflo]

Hi Guys

I need some help  for this set up, the small space ship must be able to undock the hold and dock again.

What I need is to know how to do the setting so that the 2 docking ports will still work after the first undocking.

I designed the small space ship with 2 docking ports, one on the top one at the back, so that it will be able  to sustain the flight to orbit, being in the cargo hold. It works, the problem being how to have my 2 docking ports still working, the 2 "female" parts being really parts of the cargo hold?

To do this I put a "female" docking port on the docking port at the back, designed it to be a root part with the root gizmo and record the small space ship in the Subassemblies part of my SPH.

I loaded my Cargo SSTO, took my small space ship from subassembly and set it in the hold by the mean of the "female" back docking port. I know that if I decouple this docking port, it will free the small space ship and the female docking port will stay as part of the cargo.

Now what about my top docking port (the second docking port)? How to set the "female" top docking port as part of the carg, so that it will not fall when undocking,  and have it really "dock" on the other part.?

If I take this docking port and I put it against the top docking port, it works because there's a node to attach it, but in this case, how to fix it to the cargo hold where there no node?

If i set a cubic octogonal strut on the cargo hold got a node to attach my docking port, but now how to make it work with top docking port of my space ship?

 

 

[Snark]

Not quite sure I'm understanding the problem.  (For one thing, there's no such thing as "male" or "female" docking ports in KSP; they're all the same, other than size.)  If you want to re-dock two ports together, you just move them together and then they dock.  What's the problem?

I'm not dismissing your issue, obviously it's there ... just that it's hard to figure out exactly what trouble you're having, from the description.  Could you post some screenshots to illustrate the issue?

Here's my best guess as to what you mean:  You want to have an L-shaped docking configuration, where your small ship has one port on the end and one port on the side.  You want this to dock to two ports on the cargo bay, to keep it stable.  I assume that just using a single docking port doesn't work for you because it's not stiff enough?

Well then, you do this:  Build the cargo bay so that it has one docking port at the end, and another docking port appropriately positioned on the side (on the inside, facing inwards).  Bring in your little ship as a subassembly whose root part is its aft docking port, and attach it to the docking port at the end of the cargo bay, so that its side-mounted port lines up with the side-mounted port on the cargo bay.

It's true that in this scenario, the two side-mounted ports aren't really "attached", just sitting next to each other.  But that's the best you're gonna get:  in KSP it's impossible to build a closed loop of parts, due to the tree structure of ships.  But in this case it should be fine, even though they're not, technically speaking, attached to each other-- as soon as you launch, the magnetic clamps in the two ports will grab hold, and it should keep the ship reasonably stable (i.e. accomplish what you want).

That's just my best guess as to what you're trying to do -- like I said, screenshots would help make it clearer.

Edited January 11, 2016 by Snark

[gilflo]

Hi 

Thank you to take time to read me.

OK, no male or female docking port, same part docking together, i know, that was just a "picture"

To make it simple, I just want to to set up a freight in a cargo by means of 2 docking ports, the freight being a subassembly part. As a subassembly part is it possible to select the 2 docking ports as root parts and if yes, how to proceed?

I just manage to select 1 docking port as root part, so when i set up the freight in the hold, i got only 1 attach point on 1 docking port....

Sorry i had seen all your post.

That's exactly what I want, a docking port on the rear and one on the top.

So if I understand you, the root part of the freight should be the back docking ports together assembled on the subassembly and 1 docking port on the top, its "brother" being in the cargo hold at the right place, so that on launch they will clamp and hold the freight by the top also?

Edited January 11, 2016 by gilflo

[swjr-swis]

Build the cargo plane with the two docking ports, spaced apart so they just allow space for the smaller ship with the two ports.

Now grab the subassembly of the smaller ship, and connect just one of the ports. Either one, doesn't really matter. for KSP, the other ports are not connected at this point, but it makes no difference.

Now when you launch and load the assembled ship, what happens is that the two ports that are not connected, but right in front of each other, will get magnetically attracted and dock. Sometimes, this doesn't happen right way - just quicksave/quickload, or go back to space center and return to the craft. They will be docked when you get back.

Now you have the smaller ship docked both at top and bottom. Happy launching.

 

[gilflo]

Ok thanks, I'll try that

[Temstar]

Why do you need to have both docking ports actually docked in VAB/SPH? Can't you just have the top docking port of the payload docked to the SSTO's cargo bay docking port, then have the payload's side docking port not actually docked to anything? If you need stiffening of the payload so it doesn't wobble about inside the cargo bay then just run a strut from the floor of the cargo bay to the payload?

[swjr-swis]

6 minutes ago, Temstar said:

Why do you need to have both docking ports actually docked in VAB/SPH?

Intuitively, until you learn that KSP simply does not allow two simultaneous connections, it seems like it should work. Nodes 'click' onto each other, so if I fit something with two visible nodes between two other visible nodes perfectly spaced to fit, why does it not attach to both? Neither the visual interface nor any documentation in the game does anything to dispell this notion.

It's really not that surprising that it confuses some players. And even after we learn it can't be done, we'd -secretly or vocally- all want it to work that way anyway, we just accept it as a limitation of how KSP works.

It's no big deal, we've all had that moment when we started playing KSP.

[gilflo]

17 minutes ago, Temstar said:

Why do you need to have both docking ports actually docked in VAB/SPH? Can't you just have the top docking port of the payload docked to the SSTO's cargo bay docking port, then have the payload's side docking port not actually docked to anything? If you need stiffening of the payload so it doesn't wobble about inside the cargo bay then just run a strut from the floor of the cargo bay to the payload?

It 's a small science space ship that is supposed to be able to undock from and dock again when necessary to be brought back to Kerbin by the mother SSTO

[Temstar]

It is possible to make loops, but it's a pain in the ass to setup and require a good understanding of both KSP's tree structure and how docking works once simulation is actually running. Plus you need a steady hand.

If you insist you need the L shaped docking here's how to achieve it:

1. First, attach your payload to the cargo bay like normal with end on end docking ports
2. Now, put a docking port on the floor of the docking bay, use the translate gizmo to shift this docking port along the length of the cargo bay so it lines up as pixel perfect as you can get with the payload's side docking port. You may also need to adjust how deep / how much protruding out this docking port sits on the floor so you get almost no gap between the lips of the two docking ports

That's all. But wait you say, those two docking ports are not actually docked in the VAB/SPH! You are correct they are not. But once you actually put this craft on the launchpad/runway and the simulation loads the two will instantly become docked, assuming you lined them up well enough.

[Vegetal]

I would use another approach. Just use struts. When you have to re-dock, the payload will be considered another ship already, and won't clip through the cargo bay walls.

That way, you can be sure the bay itself will hold the payload for landing.

[gilflo]

5 hours ago, Vegetal said:

I would use another approach. Just use struts. When you have to re-dock, the payload will be considered another ship already, and won't clip through the cargo bay walls.

That way, you can be sure the bay itself will hold the payload for landing.

Ok guys, thank's for you comments, Itried what you tell me TEMSTAR, and it did not seems to work for the side docking, but I'll try harder and look at that.

VEGETAL, are you saying that whatever is the weight of the freight, once redock on one docking port only, it don't need any struts nor more docking port because the bay itself will hold the freight until landing?

I am surprise. In this case why would i need struts for climb to orbit ? Is that a bug in the game?

[Temstar]

Here's a set of pictures to show my method @gilflo:


Here we have a simulation of your payload inside your cargo hold. As we can see currently the top of the payload is attached to the docking port in the "cargo hold". The payload has a inline docking port facing down and there's a docking port on the "floor" of the cargo hold but they are no where near each other and not connected.


Here is the same setup, but we have used the translation gizmo to closely align the inline docking port with the floor docking port of the cargo hold. They are still not connected inside the VAB and you can see a thin gap between the two

Here I put the payload on the launchpad and let the physics load. You notice that the two docking ports that were connected in the VAB are still connected here and evidenced by the fact that they have the unique "Decouple Node" action that you cannot get from docking two docking ports together outside of the VAB. However the inline docking port of the payload and the floor docking port on the cargo hold has become stuck together and hard docked, as evidenced by the "Undock" function. What happened was that as soon as the physics loaded the magnetic attraction of the two docking ports glued them together.

The first few times you do this you need to fiddle around with alignment to get this to work before you get the hang of it, which was why I said it can be a pain in the ass to setup. Also once you release this payload it can become very tricky to get both docking ports to dock again later.

Edited January 12, 2016 by Temstar

[gilflo]

Thank you TEMSTAR

As you said, it's very difficult to align 2 docking ports so that they glued together the first time. I got some success after a long pain, but more tricky is the dock again.

I am wondering if having 2 docking ports align on the floor, that means one axe, instead of one on a vertical axe and one horizontal axe, would not be easier for docking again......

[Temstar]

5 minutes ago, gilflo said:

Thank you TEMSTAR

As you said, it's very difficult to align 2 docking ports so that they glued together the first time. I got some success after a long pain, but more tricky is the dock again.

I am wondering if having 2 docking ports align on the floor, that means one axe, instead of one on a vertical axe and one horizontal axe, would not be easier for docking again......

It definitely is easier if they are all on one side, instead of an L shape or even worse a sandwich.

I first came up with the multi-docking technique way back in beta. Back then we didn't have the large 2.5m docking port yet so assembling big structure in space that's rigid was a huge pain. To get around this I made a subassembly that's a 2.5m flat adapter with four 1.25m docking ports:




Propellant depot, assembled in LKO and ready to head to Mun.


Eve exploration fleet.

I found it quite easy to dock and have all four connect at the same time. So this sort of multi-docking is definitely workable.

Edited January 12, 2016 by Temstar

[gilflo]

OK I am going to study that, thank's again

[Vegetal]

Not a bug, just the way the game works. The game has to allow clipping when it loads your craft, or else you would have problems.

When you undock the payload, the game has to load collisions for it too, and it doesn't unload them when you re dock.

I already used this technique on space planes, but the payload was large enough to not oscillate inside the bay (2.5m payload in a mk3 bay).

You can also use KAS, it's an excellent mod that has struts connectable by EVA.

[gilflo]

Well i am going to look if with only one docking port, once reduce, the payload stay in hold of my Mark IV

It's a big one, taking all the place in the hold and if necessary i'll at KAS that i know and that I have

Edited January 12, 2016 by gilflo

[gilflo]

Hi VEGETAL and TEMSTAR  

You are absolutely right about the fact that on redocking, I do not need strut to maintain the payload.

Here are some pics of my Mark IV Cargo and its spaceship in the reducing in the hold. 

This is an autonomous science ship equipped with a lab and 4 tweakeable bulb engines from Atomic Age with a cooling system. They are mounted on hinges. Bulb engine is the only gimbal nuclear engine and this ship is able of 10000DV, horizontal flight as well as very easy vertical flight at 100-200m/s over the ground of planet with no atmosphere, to explore and make science. No equipped to travel trough atmosphere, won't support overheating, that's why i reduce it to bring it back to Kerbin and it was a success......

 

3 minutes ago, gilflo said:

Hi VEGETAL and TEMSTAR  

You are absolutely right about the fact that on redocking, I do not need strut to maintain the payload.

Here are some pics of my Mark IV Cargo and its spaceship in the reducing in the hold. 

This is an autonomous science ship equipped with a lab and 4 tweakeable bulb engines from Atomic Age with a cooling system. They are mounted on hinges. Bulb engine is the only gimbal nuclear engine and this ship is able of 10000DV, horizontal flight as well as very easy vertical flight at 100-200m/s over the ground of planet with no atmosphere, to explore and make science. No equipped to travel trough atmosphere, won't support overheating, that's why i need to redock  to bring it back safe to Kerbin and it was a success......

 

 

Edited January 14, 2016 by gilflo

[Vegetal]

Told ya

But if you are so much into mods, then the most elegant solution would be to use KAS struts in my opinion, you can place them with an engineer on EVA.