Trusses and their uses / something missing ?

[Psykikk]

Hi,

have just tried out one ship-design and seem to have found some odd behavior:

when you start building your ship, trusses connect perfectly and help increase stability.

lets say, (ascii incoming)

a O is a fuel tank,

I or - is a truss

.. is nothing

so i start building a rectangle (looking down on my ship

the design looks like this

o-o

I.I

o.o

since the measurements are all identical, i should be able to attach a truss to finish the rectangle.

BUT, the truss only connects to one of the two tanks

so I cannot stabilize and connect the complete rectangle.

is that how trusses should work ? or is that simply an odd behaviour / bug ?

thx in advance

[OptimumAmoeba]

It's not a bug, it's to do with the tree structure with parts that stops you from doing this. You will need to use a strut to connect the last corner.

[Psykikk]

It's not a bug, it's to do with the tree structure with parts that stops you from doing this. You will need to use a strut to connect the last corner.

hm. tree structure.. haven´t read about that. but i think its a dumb mechanic.

so for this particular design i would need

at leats 4 more parts and it would look kinda stupid, too.

i know it is a little thing, but i think it needs to get ironed out.

[Garek]

You simply can't build true cycle structures with the current craft system. The parts are organized in a tree, where each part can have only one parent. So what happens to your connections is:

    Tank
   /    \
Tank  Truss
  |      |
Truss Tank
  |      |
Tank  Truss

You want the last Truss to connect to the last Tank, but that can't happen directly because parts only connect to one parent. I know of two workarounds:

1) Struts between the Tank and the Truss can replace the hard joint. Keep in mind that the struts remain only as long as the two parts are connected through the tree structure.

2) Docking ports. Two docking ports touching each other will connect on vehicle load on launch. For this, your connections have to look like this:

...     ...
 |      |
Tank  Truss
 |      |
Port   Port

Also, this is not an intended game mechanic, but a limitation imposed by the way crafts are stored.

[Psykikk]

I see.

have to rethink my whole design then. sad.

i dreamed about hexagonal and octagonal and cubic ships and such....

[OptimumAmoeba]

Let the genius / insanity begin!

[Kerbart]

hm. tree structure.. haven´t read about that. but i think its a dumb mechanic.

(...)

i know it is a little thing, but i think it needs to get ironed out.

Trees are a reliable way of storing complex structures. They allow for quick and precise determination what part goes where, what parts come off when undocking, and what parts stop working when one of them fails (during launch) without requiring extensive computing.

I'm sure the devs are aware that the tree topology is not the most realistic representation of a complex ship, and of the limitations that it brings, but apparently they judged that the benefits outweigh the limitations.

[Psykikk]

yeah might be. but making circle constructions possible would still be awesome.

but good to know its more of a program-issue rather than something else.

which means it could get fixed.

might be that this circle - construction was also the reason my ssto designs were flawed....

[sanity]

just build it in orbit

[Psykikk]

just build it in orbit

building in orbit is not an option, as docked structures are not even close to stable enough,

also connecting struts, plates and trusses in space is not possible. (alas)

and besting the challenge if putting stuff to orbit is one of the majr things i enjoy about KSP

[solidgeoff]

Just curious, since it seems we've got some people who know programming well, do you think changing the game over from tree to a more complex system would be a relatively easy thing to do for KSP? Or would it take a complete overhaul of the system? Currently, it seems struts seem to help most issues. For me, the thing I'd love to see if the ability to grab a complex object (composed of several parts), and flip it over and use a node on the underside.

[numerobis]

You can build with docking ports very close to each other, and often the docking ports dock when you launch.

Otherwise, build close and then use the strut connector to glue things together.

[Psykikk]

You can build with docking ports very close to each other, and often the docking ports dock when you launch.

Otherwise, build close and then use the strut connector to glue things together.

the strut connector was and is my way to go, but using two parts where normally one should do the trick (putting atruss in between to tanks that were placed before) seems way more pratical and logical and intuitive.

even if the programming model currently does not allow it, it should be the way to go ... and i wonder really how difficult it would be to switch it

[Garek]

solidgeoff, I know a bit about programming, and I would say that that depends very much on how the software is organized internally, something we don't know anything about. A solution I can think of which still allows the crafts to be stored primarily as a tree would be if the VAB recognized if you clipped parts' attachment points into each other and would store a list of additional hard joints in the craft file for those connections. Of course, this creates its own problems: what if you want to have two surface-attachable parts sit directly on each other, but not connected (e.g. some stuff folded with Infernal Robotics)?

[chrisb2e9]

building in orbit is not an option, as docked structures are not even close to stable enough,

also connecting struts, plates and trusses in space is not possible. (alas)

and besting the challenge if putting stuff to orbit is one of the majr things i enjoy about KSP

Putting aside that you enjoy launching it all as one piece. I took the challenge to send up my ship in parts.

Notice dual docking ports to make sure it's all lined up properly. Also, struts added after the fact. Yes, with a mod. But it works...

If you are wondering, on the far side of the ship is my lander. There will be two, one on each side. And I am considering a slight rebuild... only 3 nuclear engines is soooooo slow!

[Psykikk]

Putting aside that you enjoy launching it all as one piece. I took the challenge to send up my ship in parts.

Notice dual docking ports to make sure it's all lined up properly. Also, struts added after the fact. Yes, with a mod. But it works...

If you are wondering, on the far side of the ship is my lander. There will be two, one on each side. And I am considering a slight rebuild... only 3 nuclear engines is soooooo slow!

wow. nice docking.

for me it takes ages to dock and even mechjeb sucks at it. sometimes i think it´s even worse than myself at docking,

especially when giving control to other docking ports that are not located directly on top / bottom.

to me docking is one of the most frustrating parts of the game , probably the main reason I am avoiding it like the plague

and launch packages as big as possible....

[Superfluous J]

for me it takes ages to dock and even mechjeb sucks at it. sometimes i think it´s even worse than myself at docking,

I don't doubt it. Mechjeb is worse than a rabid ferret at docking.

Just work at it, and read up on the parts that seem to be tripping you up. I installed the Docking Port Alignment Indicator but recently I've started dragging it off to the side so I can dock with the navball. Something, somewhere, at some point in time clicked in my brain and now I "see" it where I didn't before.

[Vlk]

I experimented with this "dual-docking" thing too, but in the end, i did not really like it. As i've noticed, the tree structure still stays, there is one "dominant" connection - you can notice this with fuel flow. (Fuel goes through one docking port, but not the other). And i'm sure it was a perfect dual-docking, because i had to undock with both docking port after.

But the main reason i dont like it is that it is still unstable and wobbly, and i noticed more lag too (well, a design like that requires a little more parts, maybe this is a reason for this too).

[Alexandicity]

Yes, I had the same problem not long ago. The tree structure imposes some restrictions, but seems a decent choice for most Kerbal endeavors.

If you want to create something that "looks" to have the loop, like your example in the first post, build it as you did. The last truss won't connect to the first tank, ok, but it will look like it does. Structurally, throw a whole bunch of struts in place to hold everything in place.